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<CENTER><A HREF="#CONTENTS"><H1>Introduction to FreeS/WAN</H1></A><BR>
</CENTER>
<HR>
<H1 ALIGN="CENTER"><A NAME="CONTENTS">Table of Contents</A></H1>
<BR>
<BR><B><A HREF="#intro">Introduction</A></B>
<UL>
<LI><A HREF="#ipsec.intro">IPsec, Security for the Internet Protocol</A></LI>
<UL>
<LI><A HREF="#intro.interop">Interoperating with other IPsec
 implementations</A></LI>
<LI><A HREF="#advantages">Advantages of IPsec</A></LI>
<LI><A HREF="#applications">Applications of IPsec</A></LI>
<UL>
<LI><A HREF="#makeVPN">Using secure tunnels to create a VPN</A></LI>
<LI><A HREF="#road.intro">Road Warriors</A></LI>
<LI><A HREF="#opp.intro">Opportunistic encryption</A></LI>
</UL>
<LI><A HREF="#types">The need to authenticate gateways</A></LI>
</UL>
<LI><A HREF="#project">The FreeS/WAN project</A></LI>
<UL>
<LI><A HREF="#goals">Project goals</A></LI>
<LI><A HREF="#staff">Project team</A></LI>
</UL>
<LI><A HREF="#products">Products containing FreeS/WAN</A></LI>
<UL>
<LI><A HREF="#distwith">Full Linux distributions</A></LI>
<LI><A HREF="#kernel_dist">Linux kernel distributions</A></LI>
<LI><A HREF="#office_dist">Office server distributions</A></LI>
<LI><A HREF="#fw_dist">Firewall distributions</A></LI>
<LI><A HREF="#turnkey">Firewall and VPN products</A></LI>
</UL>
<LI><A HREF="#docs">Information sources</A></LI>
<UL>
<LI><A HREF="#docformats">This HowTo, in multiple formats</A></LI>
<LI><A HREF="#rtfm">RTFM (please Read The Fine Manuals)</A></LI>
<LI><A HREF="#text">Other documents in the distribution</A></LI>
<LI><A HREF="#assumptions">Background material</A></LI>
<LI><A HREF="#archives">Archives of the project mailing list</A></LI>
<LI><A HREF="#howto">User-written HowTo information</A></LI>
<LI><A HREF="#applied">Papers on FreeS/WAN</A></LI>
<LI><A HREF="#licensing">License and copyright information</A></LI>
</UL>
<LI><A HREF="#sites">Distribution sites</A></LI>
<UL>
<LI><A HREF="#1_5_1">Primary site</A></LI>
<LI><A HREF="#mirrors">Mirrors</A></LI>
<LI><A HREF="#munitions">The &quot;munitions&quot; archive of Linux crypto
 software</A></LI>
</UL>
<LI><A HREF="#1_6">Links to other sections</A></LI>
</UL>
<B><A HREF="#2">Upgrading to FreeS/WAN 2.x</A></B>
<UL>
<LI><A HREF="#2_1">New! Built in Opportunistic connections</A></LI>
<UL>
<LI><A HREF="#2_1_1">Upgrading Opportunistic Encryption to 2.01 (or
 later)</A></LI>
</UL>
<LI><A HREF="#2_2">New! Policy Groups</A></LI>
<LI><A HREF="#2_3">New! Packetdefault Connection</A></LI>
<LI><A HREF="#2_4">FreeS/WAN now disables Reverse Path Filtering</A></LI>
<LI><A HREF="#2_5">Revised ipsec.conf</A></LI>
<UL>
<LI><A HREF="#2_5_1">No promise of compatibility</A></LI>
<LI><A HREF="#2_5_2">Most ipsec.conf files will work fine</A></LI>
<LI><A HREF="#2_5_3">Backward compatibility patch</A></LI>
<LI><A HREF="#2_5_4">Details</A></LI>
<LI><A HREF="#2_5_5">Upgrading from 1.x RPMs to 2.x RPMs</A></LI>
</UL>
</UL>
<B><A HREF="#quickstart">Quickstart Guide to Opportunistic Encryption</A>
</B>
<UL>
<LI><A HREF="#opp.setup">Purpose</A></LI>
<UL>
<LI><A HREF="#3_1_1">OE &quot;flag day&quot;</A></LI>
</UL>
<LI><A HREF="#opp.dns">Requirements</A></LI>
<LI><A HREF="#easy.install">RPM install</A></LI>
<UL>
<LI><A HREF="#3_3_1">Download RPMs</A></LI>
<LI><A HREF="#3_3_2">Check signatures</A></LI>
<LI><A HREF="#3_3_3">Install the RPMs</A></LI>
<LI><A HREF="#testinstall">Test</A></LI>
</UL>
<LI><A HREF="#opp.setups.list">Our Opportunistic Setups</A></LI>
<UL>
<LI><A HREF="#3_4_1">Full or partial opportunism?</A></LI>
</UL>
<LI><A HREF="#opp.client">Initiate-only setup</A></LI>
<UL>
<LI><A HREF="#3_5_1">Restrictions</A></LI>
<LI><A HREF="#forward.dns">Create and publish a forward DNS record</A></LI>
<UL>
<LI><A HREF="#3_5_2_1">Find a domain you can use</A></LI>
<LI><A HREF="#3_5_2_2">Choose your ID</A></LI>
<LI><A HREF="#3_5_2_3">Create a forward TXT record</A></LI>
<LI><A HREF="#3_5_2_4">Publish the forward TXT record</A></LI>
</UL>
<LI><A HREF="#3_5_3">Test that your key has been published</A></LI>
<LI><A HREF="#3_5_4">Configure, if necessary</A></LI>
<LI><A HREF="#3_5_5">Test</A></LI>
</UL>
<LI><A HREF="#3_6">Full Opportunism</A></LI>
<UL>
<LI><A HREF="#3_6_1">Put a TXT record in a Forward Domain</A></LI>
<LI><A HREF="#3_6_2">Put a TXT record in Reverse DNS</A></LI>
<UL>
<LI><A HREF="#3_6_2_1">Create a Reverse DNS TXT record</A></LI>
<LI><A HREF="#3_6_2_2">Publish your TXT record</A></LI>
</UL>
<LI><A HREF="#3_6_3">Test your DNS record</A></LI>
<LI><A HREF="#3_6_4">No Configuration Needed</A></LI>
<LI><A HREF="#3_6_5">Consider Firewalling</A></LI>
<LI><A HREF="#3_6_6">Test</A></LI>
<LI><A HREF="#3_6_7">Test</A></LI>
</UL>
<LI><A HREF="#opp.test">Testing opportunistic connections</A></LI>
<LI><A HREF="#3_8">Now what?</A></LI>
<LI><A HREF="#3_9">Notes</A></LI>
<LI><A HREF="#3_10">Troubleshooting OE</A></LI>
<LI><A HREF="#3_11">Known Issues</A></LI>
</UL>
<B><A HREF="#4">How to Configure Linux FreeS/WAN with Policy Groups</A></B>
<UL>
<LI><A HREF="#4_1">What are Policy Groups?</A></LI>
<UL>
<LI><A HREF="#4_1_1">Built-In Security Options</A></LI>
</UL>
<LI><A HREF="#4_2">Using Policy Groups</A></LI>
<UL>
<LI><A HREF="#4_2_1">Example 1: Using a Base Policy Group</A></LI>
<LI><A HREF="#4_2_2">Example 2: Defining IPsec Security Policy with
 Groups</A></LI>
<LI><A HREF="#4_2_3">Example 3: Creating a Simple IPsec VPN with the
 private Group</A></LI>
<LI><A HREF="#4_2_4">Example 4: New Policy Groups to Protect a Subnet</A>
</LI>
<LI><A HREF="#4_2_5">Example 5: Adding a Subnet to the VPN</A></LI>
</UL>
<LI><A HREF="#4_3">Appendix</A></LI>
<UL>
<LI><A HREF="#4_3_1">Our Hidden Connections</A></LI>
<LI><A HREF="#4_3_2">Custom Policy Groups</A></LI>
<LI><A HREF="#4_3_3">Disabling Opportunistic Encryption</A></LI>
</UL>
</UL>
<B><A HREF="#5">FreeS/WAN FAQ</A></B>
<UL>
<LI><A HREF="#questions">Index of FAQ questions</A></LI>
<LI><A HREF="#whatzit">What is FreeS/WAN?</A></LI>
<LI><A HREF="#problems">How do I report a problem or seek help?</A></LI>
<LI><A HREF="#generic">Can I get ...</A></LI>
<UL>
<LI><A HREF="#lemme_out">Can I get an off-the-shelf system that includes
 FreeS/WAN?</A></LI>
<LI><A HREF="#consultant">Can I hire consultants or staff who know
 FreeS/WAN?</A></LI>
<LI><A HREF="#commercial">Can I get commercial support?</A></LI>
</UL>
<LI><A HREF="#release">Release questions</A></LI>
<UL>
<LI><A HREF="#rel.current">What is the current release?</A></LI>
<LI><A HREF="#relwhen">When is the next release?</A></LI>
<LI><A HREF="#rel.bugs">Are there known bugs in the current release?</A></LI>
</UL>
<LI><A HREF="#mod_cons">Modifications and contributions</A></LI>
<UL>
<LI><A HREF="#modify.faq">Can I modify FreeS/WAN to ...?</A></LI>
<LI><A HREF="#contrib.faq">Can I contribute to the project?</A></LI>
<LI><A HREF="#ddoc.faq">Is there detailed design documentation?</A></LI>
</UL>
<LI><A HREF="#interact">Will FreeS/WAN work in my environment?</A></LI>
<UL>
<LI><A HREF="#interop.faq">Can FreeS/WAN talk to ...?</A></LI>
<LI><A HREF="#old_to_new">Can different FreeS/WAN versions talk to each
 other?</A></LI>
<LI><A HREF="#faq.bandwidth">Is there a limit on throughput?</A></LI>
<LI><A HREF="#faq.number">Is there a limit on number of tunnels?</A></LI>
<LI><A HREF="#faq.speed">Is a ... fast enough to handle FreeS/WAN with
 my loads?</A></LI>
</UL>
<LI><A HREF="#work_on">Will FreeS/WAN work on ... ?</A></LI>
<UL>
<LI><A HREF="#versions">Will FreeS/WAN run on my version of Linux?</A></LI>
<LI><A HREF="#nonIntel.faq">Will FreeS/WAN run on non-Intel CPUs?</A></LI>
<LI><A HREF="#multi.faq">Will FreeS/WAN run on multiprocessors?</A></LI>
<LI><A HREF="#k.old">Will FreeS/WAN work on an older kernel?</A></LI>
<LI><A HREF="#k.versions">Will FreeS/WAN run on the latest kernel
 version?</A></LI>
<LI><A HREF="#interface.faq">Will FreeS/WAN work on unusual network
 hardware?</A></LI>
<LI><A HREF="#vlan">Will FreeS/WAN work on a VLAN (802.1q) network?</A></LI>
</UL>
<LI><A HREF="#features.faq">Does FreeS/WAN support ...</A></LI>
<UL>
<LI><A HREF="#VPN.faq">Does FreeS/WAN support site-to-site VPN (Virtual
 Private Network) applications?</A></LI>
<LI><A HREF="#warrior.faq">Does FreeS/WAN support remote users
 connecting to a LAN?</A></LI>
<LI><A HREF="#road.shared.possible">Does FreeS/WAN support remote users
 using shared secret authentication?</A></LI>
<LI><A HREF="#wireless.faq">Does FreeS/WAN support wireless networks?</A>
</LI>
<LI><A HREF="#PKIcert">Does FreeS/WAN support X.509 or other PKI
 certificates?</A></LI>
<LI><A HREF="#Radius">Does FreeS/WAN support user authentication
 (Radius, SecureID, Smart Card...)?</A></LI>
<LI><A HREF="#NATtraversal">Does FreeS/WAN support NAT traversal?</A></LI>
<LI><A HREF="#virtID">Does FreeS/WAN support assigning a &quot;virtual
 identity&quot; to a remote system?</A></LI>
<LI><A HREF="#noDES.faq">Does FreeS/WAN support single DES encryption?</A>
</LI>
<LI><A HREF="#AES.faq">Does FreeS/WAN support AES encryption?</A></LI>
<LI><A HREF="#other.cipher">Does FreeS/WAN support other encryption
 algorithms?</A></LI>
</UL>
<LI><A HREF="#canI">Can I ...</A></LI>
<UL>
<LI><A HREF="#policy.preconfig">Can I use policy groups along with
 explicitly configured connections?</A></LI>
<LI><A HREF="#policy.off">Can I turn off policy groups?</A></LI>
<LI><A HREF="#reload">Can I reload connection info without restarting?</A>
</LI>
<LI><A HREF="#masq.faq">Can I use several masqueraded subnets?</A></LI>
<LI><A HREF="#dup_route">Can I use subnets masqueraded to the same
 addresses?</A></LI>
<LI><A HREF="#road.masq">Can I assign a road warrior an address on my
 net (a virtual identity)?</A></LI>
<LI><A HREF="#road.many">Can I support many road warriors with one
 gateway?</A></LI>
<LI><A HREF="#road.PSK">Can I have many road warriors using shared
 secret authentication?</A></LI>
<LI><A HREF="#QoS">Can I use Quality of Service routing with FreeS/WAN?</A>
</LI>
<LI><A HREF="#deadtunnel">Can I recognise dead tunnels and shut them
 down?</A></LI>
<LI><A HREF="#demanddial">Can I build IPsec tunnels over a demand-dialed
 link?</A></LI>
<LI><A HREF="#GRE">Can I build GRE, L2TP or PPTP tunnels over IPsec?</A></LI>
<LI><A HREF="#NetBIOS">... use Network Neighborhood (Samba, NetBIOS)
 over IPsec?</A></LI>
</UL>
<LI><A HREF="#setup.faq">Life's little mysteries</A></LI>
<UL>
<LI><A HREF="#cantping">I cannot ping ....</A></LI>
<LI><A HREF="#forever">It takes forever to ...</A></LI>
<LI><A HREF="#route">I send packets to the tunnel with route(8) but they
 vanish</A></LI>
<LI><A HREF="#down_route">When a tunnel goes down, packets vanish</A></LI>
<LI><A HREF="#firewall_ate">The firewall ate my packets!</A></LI>
<LI><A HREF="#dropconn">Dropped connections</A></LI>
<LI><A HREF="#defaultroutegone">Disappearing %defaultroute</A></LI>
<LI><A HREF="#tcpdump.faq">TCPdump on the gateway shows strange things</A>
</LI>
<LI><A HREF="#no_trace">Traceroute does not show anything between the
 gateways</A></LI>
</UL>
<LI><A HREF="#man4debug">Testing in stages</A></LI>
<UL>
<LI><A HREF="#nomanual">Manually keyed connections don't work</A></LI>
<LI><A HREF="#spi_error">One manual connection works, but second one
 fails</A></LI>
<LI><A HREF="#man_no_auto">Manual connections work, but automatic keying
 doesn't</A></LI>
<LI><A HREF="#nocomp">IPsec works, but connections using compression
 fail</A></LI>
<LI><A HREF="#pmtu.broken">Small packets work, but large transfers fail</A>
</LI>
<LI><A HREF="#subsub">Subnet-to-subnet works, but tests from the
 gateways don't</A></LI>
</UL>
<LI><A HREF="#compile.faq">Compilation problems</A></LI>
<UL>
<LI><A HREF="#gmp.h_missing">gmp.h: No such file or directory</A></LI>
<LI><A HREF="#noVM">... virtual memory exhausted</A></LI>
</UL>
<LI><A HREF="#error">Interpreting error messages</A></LI>
<UL>
<LI><A HREF="#route-client">route-client (or host) exited with status 7</A>
</LI>
<LI><A HREF="#unreachable">SIOCADDRT:Network is unreachable</A></LI>
<LI><A HREF="#modprobe">ipsec_setup: modprobe: Can't locate module ipsec</A>
</LI>
<LI><A HREF="#noKLIPS">ipsec_setup: Fatal error, kernel appears to lack
 KLIPS</A></LI>
<LI><A HREF="#noDNS">ipsec_setup: ... failure to fetch key for ... from
 DNS</A></LI>
<LI><A HREF="#dup_address">ipsec_setup: ... interfaces ... and ... share
 address ...</A></LI>
<LI><A HREF="#kflags">ipsec_setup: Cannot adjust kernel flags</A></LI>
<LI><A HREF="#message_num">Message numbers (MI3, QR1, et cetera) in
 Pluto messages</A></LI>
<LI><A HREF="#conn_name">Connection names in Pluto error messages</A></LI>
<LI><A HREF="#cantorient">Pluto: ... can't orient connection</A></LI>
<LI><A HREF="#no.interface">... we have no ipsecN interface for either
 end of this connection</A></LI>
<LI><A HREF="#noconn">Pluto: ... no connection is known</A></LI>
<LI><A HREF="#nosuit">Pluto: ... no suitable connection ...</A></LI>
<LI><A HREF="#noconn.auth">Pluto: ... no connection has been authorized</A>
</LI>
<LI><A HREF="#noDESsupport">Pluto: ... OAKLEY_DES_CBC is not supported.</A>
</LI>
<LI><A HREF="#notransform">Pluto: ... no acceptable transform</A></LI>
<LI><A HREF="#rsasigkey">rsasigkey dumps core</A></LI>
<LI><A HREF="#sig4">!Pluto failure!: ... exited with ... signal 4</A></LI>
<LI><A HREF="#econnrefused">ECONNREFUSED error message</A></LI>
<LI><A HREF="#no_eroute">klips_debug: ... no eroute!</A></LI>
<LI><A HREF="#SAused">... trouble writing to /dev/ipsec ... SA already
 in use</A></LI>
<LI><A HREF="#ignore">... ignoring ... payload</A></LI>
<LI><A HREF="#unknown_rightcert">unknown parameter name &quot;rightcert&quot;</A></LI>
</UL>
<LI><A HREF="#spam">Why don't you restrict the mailing lists to reduce
 spam?</A></LI>
</UL>
<B><A HREF="#manpages">FreeS/WAN manual pages</A></B>
<UL>
<LI><A HREF="#man.file">Files</A></LI>
<LI><A HREF="#man.command">Commands</A></LI>
<LI><A HREF="#man.lib">Library routines</A></LI>
</UL>
<B><A HREF="#firewall">FreeS/WAN and firewalls</A></B>
<UL>
<LI><A HREF="#filters">Filtering rules for IPsec packets</A></LI>
<LI><A HREF="#examplefw">Firewall configuration at boot</A></LI>
<UL>
<LI><A HREF="#simple.rules">A simple set of rules</A></LI>
<LI><A HREF="#complex.rules">Other rules</A></LI>
<UL>
<LI><A HREF="#7_2_2_1">Adding additional rules</A></LI>
<LI><A HREF="#7_2_2_2">Modifying existing rules</A></LI>
</UL>
<LI><A HREF="#rules.pub">Published rule sets</A></LI>
<UL>
<LI><A HREF="#Ranch.trinity">Scripts based on Ranch's work</A></LI>
<LI><A HREF="#seawall">The Seattle firewall</A></LI>
<LI><A HREF="#rcf">The RCF scripts</A></LI>
<LI><A HREF="#asgard">Asgard scripts</A></LI>
<LI><A HREF="#user.scripts">User scripts from the mailing list</A></LI>
</UL>
</UL>
<LI><A HREF="#updown">Calling firewall scripts, named in ipsec.conf(5)</A>
</LI>
<UL>
<LI><A HREF="#pre_post">Scripts called at IPsec start and stop</A></LI>
<LI><A HREF="#up_down">Scripts called at connection up and down</A></LI>
<UL>
<LI><A HREF="#fw.default">The default script</A></LI>
<LI><A HREF="#userscript">User-written scripts</A></LI>
</UL>
<LI><A HREF="#ipchains.script">Scripts for ipchains or iptables</A></LI>
</UL>
<LI><A HREF="#NAT">A complication: IPsec vs. NAT</A></LI>
<UL>
<LI><A HREF="#nat_ok">NAT on or behind the IPsec gateway works</A></LI>
<LI><A HREF="#nat_bad">NAT between gateways is problematic</A></LI>
<LI><A HREF="#NAT.ref">Other references on NAT and IPsec</A></LI>
</UL>
<LI><A HREF="#complications">Other complications</A></LI>
<UL>
<LI><A HREF="#through">IPsec through the gateway</A></LI>
<LI><A HREF="#ipsec_only">Preventing non-IPsec traffic</A></LI>
<LI><A HREF="#unknowngate">Filtering packets from unknown gateways</A></LI>
</UL>
<LI><A HREF="#otherfilter">Other packet filters</A></LI>
<UL>
<LI><A HREF="#ICMP">ICMP filtering</A></LI>
<LI><A HREF="#traceroute">UDP packets for traceroute</A></LI>
<LI><A HREF="#l2tp">UDP for L2TP</A></LI>
</UL>
<LI><A HREF="#packets">How it all works: IPsec packet details</A></LI>
<UL>
<LI><A HREF="#noport">ESP and AH do not have ports</A></LI>
<LI><A HREF="#header">Header layout</A></LI>
<LI><A HREF="#dhr">DHR on the updown script</A></LI>
</UL>
</UL>
<B><A HREF="#trouble">Linux FreeS/WAN Troubleshooting Guide</A></B>
<UL>
<LI><A HREF="#overview">Overview</A></LI>
<LI><A HREF="#install">1. During Install</A></LI>
<UL>
<LI><A HREF="#8_2_1">1.1 RPM install gotchas</A></LI>
<LI><A HREF="#8_2_2">1.2 Problems installing from source</A></LI>
<LI><A HREF="#install.check">1.3 Install checks</A></LI>
<LI><A HREF="#oe.trouble">1.3 Troubleshooting OE</A></LI>
</UL>
<LI><A HREF="#negotiation">2. During Negotiation</A></LI>
<UL>
<LI><A HREF="#state">2.1 Determine Connection State</A></LI>
<UL>
<LI><A HREF="#8_3_1_1">Finding current state</A></LI>
<LI><A HREF="#8_3_1_2">What's this supposed to look like?</A></LI>
</UL>
<LI><A HREF="#find.pluto.error">2.2 Finding error text</A></LI>
<UL>
<LI><A HREF="#8_3_2_1">Verbose start for more information</A></LI>
<LI><A HREF="#8_3_2_2">Debug levels count</A></LI>
<LI><A HREF="#8_3_2_3">ipsec barf for lots of debugging information</A></LI>
<LI><A HREF="#8_3_2_4">Find the error</A></LI>
<LI><A HREF="#8_3_2_5">Play both sides</A></LI>
</UL>
<LI><A HREF="#interpret.pluto.error">2.3 Interpreting a Negotiation
 Error</A></LI>
<UL>
<LI><A HREF="#ikepath">Connection stuck at STATE_MAIN_I1</A></LI>
<LI><A HREF="#8_3_3_2">Other errors</A></LI>
</UL>
</UL>
<LI><A HREF="#use">3. Using a Connection</A></LI>
<UL>
<LI><A HREF="#8_4_1">3.1 Orienting yourself</A></LI>
<UL>
<LI><A HREF="#8_4_1_1">How do I know if it works?</A></LI>
<LI><A HREF="#8_4_1_2">ipsec barf is useful again</A></LI>
</UL>
<LI><A HREF="#8_4_2">3.2 Those pesky configuration errors</A></LI>
<LI><A HREF="#route.firewall">3.3 Check Routing and Firewalling</A></LI>
<UL>
<LI><A HREF="#8_4_3_1">Background:</A></LI>
<LI><A HREF="#ifconfig">View Interface and Firewall Statistics</A></LI>
</UL>
<LI><A HREF="#sniff">3.4 When in doubt, sniff it out</A></LI>
<UL>
<LI><A HREF="#8_4_4_1">Anticipate your packets' path</A></LI>
</UL>
<LI><A HREF="#find.use.error">3.5 Check your logs</A></LI>
<UL>
<LI><A HREF="#interpret.use.error">Interpreting log text</A></LI>
</UL>
<LI><A HREF="#bigpacket">3.6 More testing for the truly thorough</A></LI>
<UL>
<LI><A HREF="#8_4_6_1">Large Packets</A></LI>
<LI><A HREF="#8_4_6_2">Stress Tests</A></LI>
</UL>
</UL>
<LI><A HREF="#prob.report">4. Problem Reporting</A></LI>
<UL>
<LI><A HREF="#8_5_1">4.1 How to ask for help</A></LI>
<LI><A HREF="#8_5_2">4.2 Where to ask</A></LI>
</UL>
<LI><A HREF="#notes">5. Additional Notes on Troubleshooting</A></LI>
<UL>
<LI><A HREF="#system.info">5.1 Information available on your system</A></LI>
<UL>
<LI><A HREF="#logusage">Logs used</A></LI>
<LI><A HREF="#pages">man pages provided</A></LI>
<LI><A HREF="#statusinfo">Status information</A></LI>
</UL>
<LI><A HREF="#testgates"> 5.2 Testing between security gateways</A></LI>
<LI><A HREF="#ifconfig1">5.3 ifconfig reports for KLIPS debugging</A></LI>
<LI><A HREF="#gdb"> 5.4 Using GDB on Pluto</A></LI>
</UL>
</UL>
<B><A HREF="#compat">Linux FreeS/WAN Compatibility Guide</A></B>
<UL>
<LI><A HREF="#spec">Implemented parts of the IPsec Specification</A></LI>
<UL>
<LI><A HREF="#in">In Linux FreeS/WAN</A></LI>
<LI><A HREF="#dropped">Deliberately omitted</A></LI>
<LI><A HREF="#not">Not (yet) in Linux FreeS/WAN</A></LI>
</UL>
<LI><A HREF="#pfkey">Our PF-Key implementation</A></LI>
<UL>
<LI><A HREF="#pfk.port">PF-Key portability</A></LI>
</UL>
<LI><A HREF="#otherk">Kernels other than the latest 2.2.x and 2.4.y</A></LI>
<UL>
<LI><A HREF="#kernel.2.0">2.0.x kernels</A></LI>
<LI><A HREF="#kernel.production">2.2 and 2.4 kernels</A></LI>
</UL>
<LI><A HREF="#otherdist">Intel Linux distributions other than Redhat</A></LI>
<UL>
<LI><A HREF="#rh7">Redhat 7.0</A></LI>
<LI><A HREF="#suse">SuSE Linux</A></LI>
<UL>
<LI><A HREF="#9_4_2_1">SuSE Linux 5.3</A></LI>
</UL>
<LI><A HREF="#slack">Slackware</A></LI>
<LI><A HREF="#deb">Debian</A></LI>
<LI><A HREF="#caldera">Caldera</A></LI>
</UL>
<LI><A HREF="#CPUs">CPUs other than Intel</A></LI>
<UL>
<LI><A HREF="# strongarm">Corel Netwinder (StrongARM CPU)</A></LI>
<LI><A HREF="#yellowdog">Yellow Dog Linux on Power PC</A></LI>
<LI><A HREF="#mklinux">Mklinux</A></LI>
<LI><A HREF="#alpha">Alpha 64-bit processors</A></LI>
<LI><A HREF="#SPARC">Sun SPARC processors</A></LI>
<LI><A HREF="#mips">MIPS processors</A></LI>
<LI><A HREF="#crusoe">Transmeta Crusoe</A></LI>
<LI><A HREF="#coldfire">Motorola Coldfire</A></LI>
</UL>
<LI><A HREF="#multiprocessor">Multiprocessor machines</A></LI>
<LI><A HREF="#hardware">Support for crypto hardware</A></LI>
<LI><A HREF="#ipv6">IP version 6 (IPng)</A></LI>
<UL>
<LI><A HREF="#v6.back">IPv6 background</A></LI>
</UL>
</UL>
<B><A HREF="#10">Interoperating with FreeS/WAN</A></B>
<UL>
<LI><A HREF="#10_1">Interop at a Glance</A></LI>
<UL>
<LI><A HREF="#10_1_1">Key</A></LI>
</UL>
<LI><A HREF="#10_2">Basic Interop Rules</A></LI>
<LI><A HREF="#10_3">Longer Stories</A></LI>
<UL>
<LI><A HREF="#10_3_1">For More Compatible Implementations</A></LI>
<UL>
<LI><A HREF="#freeswan">FreeS/WAN</A></LI>
<LI><A HREF="#isakmpd">isakmpd (OpenBSD)</A></LI>
<LI><A HREF="#kame">Kame</A></LI>
<LI><A HREF="#mcafee">PGPNet/McAfee</A></LI>
<LI><A HREF="#microsoft">Microsoft Windows 2000/XP</A></LI>
<LI><A HREF="#ssh">SSH Sentinel</A></LI>
<LI><A HREF="#safenet">Safenet SoftPK/SoftRemote</A></LI>
</UL>
<LI><A HREF="#10_3_2">For Other Implementations</A></LI>
<UL>
<LI><A HREF="#6wind">6Wind</A></LI>
<LI><A HREF="#alcatel">Alcatel Timestep</A></LI>
<LI><A HREF="#apple">Apple Macintosh System 10+</A></LI>
<LI><A HREF="#ashleylaurent">AshleyLaurent VPCom</A></LI>
<LI><A HREF="#borderware">Borderware</A></LI>
<LI><A HREF="#checkpoint">Check Point VPN-1 or FW-1</A></LI>
<LI><A HREF="#cisco">Cisco</A></LI>
<LI><A HREF="#equinux">Equinux VPN tracker (for Mac OS X)</A></LI>
<LI><A HREF="#fsecure">F-Secure</A></LI>
<LI><A HREF="#gauntlet">Gauntlet GVPN</A></LI>
<LI><A HREF="#aix">IBM AIX</A></LI>
<LI><A HREF="#as400">IBM AS/400</A></LI>
<LI><A HREF="#intel">Intel Shiva LANRover / Net Structure</A></LI>
<LI><A HREF="#lancom">LanCom (formerly ELSA)</A></LI>
<LI><A HREF="#linksys">Linksys</A></LI>
<LI><A HREF="#lucent">Lucent</A></LI>
<LI><A HREF="#netasq">Netasq</A></LI>
<LI><A HREF="#netcelo">Netcelo</A></LI>
<LI><A HREF="#netgear">Netgear fvs318</A></LI>
<LI><A HREF="#netscreen">Netscreen 100 or 5xp</A></LI>
<LI><A HREF="#nortel">Nortel Contivity</A></LI>
<LI><A HREF="#radguard">Radguard</A></LI>
<LI><A HREF="#raptor">Raptor (NT or Solaris)</A></LI>
<LI><A HREF="#redcreek">Redcreek Ravlin</A></LI>
<LI><A HREF="#sonicwall">SonicWall</A></LI>
<LI><A HREF="#sun">Sun Solaris</A></LI>
<LI><A HREF="#symantec">Symantec</A></LI>
<LI><A HREF="#watchguard">Watchguard Firebox</A></LI>
<LI><A HREF="#xedia">Xedia Access Point/QVPN</A></LI>
<LI><A HREF="#zyxel">Zyxel</A></LI>
</UL>
</UL>
</UL>
<B><A HREF="#performance">Performance of FreeS/WAN</A></B>
<UL>
<LI><A HREF="#pub.bench">Published material</A></LI>
<LI><A HREF="#perf.estimate">Estimating CPU overheads</A></LI>
<UL>
<LI><A HREF="#perf.more">Higher performance alternatives</A></LI>
<LI><A HREF="#11_2_2">Other considerations</A></LI>
</UL>
<LI><A HREF="#biggate">Many tunnels from a single gateway</A></LI>
<LI><A HREF="#low-end">Low-end systems</A></LI>
<LI><A HREF="#klips.bench">Measuring KLIPS</A></LI>
<LI><A HREF="#speed.compress">Speed with compression</A></LI>
<LI><A HREF="#methods">Methods of measuring</A></LI>
</UL>
<B><A HREF="#test.freeswan">Testing FreeS/WAN</A></B>
<UL>
<LI><A HREF="#test.oe">Testing opportunistic connections</A></LI>
<UL>
<LI><A HREF="#12_1_1">Basic OE Test</A></LI>
<LI><A HREF="#12_1_2">OE Gateway Test</A></LI>
<LI><A HREF="#12_1_3">Additional OE tests</A></LI>
</UL>
<LI><A HREF="#test.uml">Testing with User Mode Linux</A></LI>
<LI><A HREF="#testnet">Configuration for a testbed network</A></LI>
<UL>
<LI><A HREF="#testbed">Testbed network</A></LI>
<LI><A HREF="#tcpdump.test">Using packet sniffers in testing</A></LI>
</UL>
<LI><A HREF="#verify.crypt">Verifying encryption</A></LI>
<LI><A HREF="#mail.test">Mailing list pointers</A></LI>
</UL>
<B><A HREF="#kernelconfig">Kernel configuration for FreeS/WAN</A></B>
<UL>
<LI><A HREF="#notall">Not everyone needs to worry about kernel
 configuration</A></LI>
<LI><A HREF="#assume">Assumptions and notation</A></LI>
<UL>
<LI><A HREF="#labels">Labels used</A></LI>
</UL>
<LI><A HREF="#kernelopt">Kernel options for FreeS/WAN</A></LI>
</UL>
<B><A HREF="#adv_config">Other configuration possibilities</A></B>
<UL>
<LI><A HREF="#thumb">Some rules of thumb about configuration</A></LI>
<UL>
<LI><A HREF="#cheap.tunnel">Tunnels are cheap</A></LI>
<LI><A HREF="#subnet.size">Subnet sizes</A></LI>
<LI><A HREF="#example.more">Other network layouts</A></LI>
<UL>
<LI><A HREF="#internet.subnet">The Internet as a big subnet</A></LI>
<LI><A HREF="#wireless.config">Wireless</A></LI>
</UL>
</UL>
<LI><A HREF="#choose">Choosing connection types</A></LI>
<UL>
<LI><A HREF="#man-auto">Manual vs. automatic keying</A></LI>
<LI><A HREF="#auto-auth">Authentication methods for auto-keying</A></LI>
<LI><A HREF="#adv-pk">Advantages of public key methods</A></LI>
</UL>
<LI><A HREF="#prodsecrets">Using shared secrets in production</A></LI>
<UL>
<LI><A HREF="#secrets">Putting secrets in ipsec.secrets(5)</A></LI>
<LI><A HREF="#securing.secrets">File security</A></LI>
<LI><A HREF="#notroadshared">Shared secrets for road warriors</A></LI>
</UL>
<LI><A HREF="#prodman">Using manual keying in production</A></LI>
<UL>
<LI><A HREF="#ranbits">Creating keys with ranbits</A></LI>
</UL>
<LI><A HREF="#boot">Setting up connections at boot time</A></LI>
<LI><A HREF="#multitunnel">Multiple tunnels between the same two
 gateways</A></LI>
<UL>
<LI><A HREF="#advroute">One tunnel plus advanced routing</A></LI>
</UL>
<LI><A HREF="#opp.gate">An Opportunistic Gateway</A></LI>
<UL>
<LI><A HREF="#14_7_1">Start from full opportunism</A></LI>
<LI><A HREF="#14_7_2">Reverse DNS TXT records for each protected machine</A>
</LI>
<LI><A HREF="#14_7_3">Publish your records</A></LI>
<LI><A HREF="#14_7_4">...and test them</A></LI>
<LI><A HREF="#14_7_5">No Configuration Needed</A></LI>
</UL>
<LI><A HREF="#extruded.config">Extruded Subnets</A></LI>
<LI><A HREF="#roadvirt">Road Warrior with virtual IP address</A></LI>
<LI><A HREF="#dynamic">Dynamic Network Interfaces</A></LI>
<UL>
<LI><A HREF="#basicdyn">Basics</A></LI>
<LI><A HREF="#bootdyn">Boot Time</A></LI>
<LI><A HREF="#changedyn">Change Time</A></LI>
</UL>
<LI><A HREF="#unencrypted">Unencrypted tunnels</A></LI>
</UL>
<B><A HREF="#install">Installing FreeS/WAN</A></B>
<UL>
<LI><A HREF="#15_1">Requirements</A></LI>
<LI><A HREF="#15_2">Choose your install method</A></LI>
<LI><A HREF="#15_3">FreeS/WAN ships with some Linuxes</A></LI>
<UL>
<LI><A HREF="#15_3_1">FreeS/WAN may be altered...</A></LI>
<LI><A HREF="#15_3_2">You might need to create an authentication keypair</A>
</LI>
<LI><A HREF="#15_3_3">Start and test FreeS/WAN</A></LI>
</UL>
<LI><A HREF="#15_4">RPM install</A></LI>
<UL>
<LI><A HREF="#15_4_1">Download RPMs</A></LI>
<LI><A HREF="#15_4_2">For freeswan.org RPMs: check signatures</A></LI>
<LI><A HREF="#15_4_3">Install the RPMs</A></LI>
<LI><A HREF="#15_4_4">Start and Test FreeS/WAN</A></LI>
</UL>
<LI><A HREF="#15_5">Install from Source</A></LI>
<UL>
<LI><A HREF="#15_5_1">Decide what functionality you need</A></LI>
<LI><A HREF="#15_5_2">Download FreeS/WAN</A></LI>
<LI><A HREF="#15_5_3">For freeswan.org source: check its signature</A></LI>
<LI><A HREF="#15_5_4">Untar, unzip</A></LI>
<LI><A HREF="#15_5_5">Patch if desired</A></LI>
<LI><A HREF="#15_5_6">... and Make</A></LI>
<UL>
<LI><A HREF="#15_5_6_1">Userland-only Install for 2.6 kernels</A></LI>
<LI><A HREF="#15_5_6_2">KLIPS install for 2.2, 2.4, or 2.6 kernels</A></LI>
</UL>
</UL>
<LI><A HREF="#15_6">Start FreeS/WAN and test your install</A></LI>
<LI><A HREF="#15_7">Test your install</A></LI>
<LI><A HREF="#15_8">Making FreeS/WAN play well with others</A></LI>
<LI><A HREF="#15_9">Configure for your needs</A></LI>
</UL>
<B><A HREF="#config">How to configure FreeS/WAN</A></B>
<UL>
<LI><A HREF="#16_1">Requirements</A></LI>
<LI><A HREF="#config.netnet">Net-to-Net connection</A></LI>
<UL>
<LI><A HREF="#netnet.info.ex">Gather information</A></LI>
<UL>
<LI><A HREF="#16_2_1_1">Get your leftrsasigkey</A></LI>
<LI><A HREF="#16_2_1_2">...and your rightrsasigkey</A></LI>
</UL>
<LI><A HREF="#16_2_2">Edit /etc/ipsec.conf</A></LI>
<LI><A HREF="#16_2_3">Start your connection</A></LI>
<LI><A HREF="#16_2_4">Do not MASQ or NAT packets to be tunneled</A></LI>
<LI><A HREF="#16_2_5">Test your connection</A></LI>
<LI><A HREF="#16_2_6">Finishing touches</A></LI>
</UL>
<LI><A HREF="#config.rw">Road Warrior Configuration</A></LI>
<UL>
<LI><A HREF="#rw.info.ex">Gather information</A></LI>
<UL>
<LI><A HREF="#16_3_1_1">Get your leftrsasigkey...</A></LI>
<LI><A HREF="#16_3_1_2">...and your rightrsasigkey</A></LI>
</UL>
<LI><A HREF="#16_3_2">Customize /etc/ipsec.conf</A></LI>
<LI><A HREF="#16_3_3">Start your connection</A></LI>
<LI><A HREF="#16_3_4">Do not MASQ or NAT packets to be tunneled</A></LI>
<LI><A HREF="#16_3_5">Test your connection</A></LI>
<LI><A HREF="#16_3_6">Finishing touches</A></LI>
<LI><A HREF="#16_3_7">Multiple Road Warriors</A></LI>
</UL>
<LI><A HREF="#16_4">What next?</A></LI>
</UL>
<B><A HREF="#background">Linux FreeS/WAN background</A></B>
<UL>
<LI><A HREF="#dns.background">Some DNS background</A></LI>
<UL>
<LI><A HREF="#forward.reverse">Forward and reverse maps</A></LI>
<LI><A HREF="#17_1_2">Hierarchy and delegation</A></LI>
<LI><A HREF="#17_1_3">Syntax of DNS records</A></LI>
<LI><A HREF="#17_1_4">Cacheing, TTL and propagation delay</A></LI>
</UL>
<LI><A HREF="#MTU.trouble">Problems with packet fragmentation</A></LI>
<LI><A HREF="#nat.background">Network address translation (NAT)</A></LI>
<UL>
<LI><A HREF="#17_3_1">NAT to non-routable addresses</A></LI>
<LI><A HREF="#17_3_2">NAT to routable addresses</A></LI>
</UL>
</UL>
<B><A HREF="#user.examples">FreeS/WAN script examples</A></B>
<UL>
<LI><A HREF="#poltorak">Poltorak's Firewall script</A></LI>
</UL>
<B><A HREF="#makecheck">How to configure to use &quot;make check&quot;</A></B>
<UL>
<LI><A HREF="#19_1">What is &quot;make check&quot;</A></LI>
<LI><A HREF="#19_2">Running &quot;make check&quot;</A></LI>
</UL>
<B><A HREF="#20">How to write a &quot;make check&quot; test</A></B>
<UL>
<LI><A HREF="#20_1">Structure of a test</A></LI>
<LI><A HREF="#20_2">The TESTLIST</A></LI>
<LI><A HREF="#20_3">Test kinds</A></LI>
<LI><A HREF="#20_4">Common parameters</A></LI>
<LI><A HREF="#20_5">KLIPStest paramaters</A></LI>
<LI><A HREF="#20_6">mkinsttest paramaters</A></LI>
<LI><A HREF="#20_7">rpm_build_install_test paramaters</A></LI>
<LI><A HREF="#20_8">libtest paramaters</A></LI>
<LI><A HREF="#20_9">umlplutotest paramaters</A></LI>
<LI><A HREF="#20_10">umlXhost parameters</A></LI>
<LI><A HREF="#20_11">kernel_patch_test paramaters</A></LI>
<LI><A HREF="#20_12">module_compile paramaters</A></LI>
</UL>
<B><A HREF="#21">Current pitfalls</A></B>
<BR>
<BR><B><A HREF="#umltesting">User-Mode-Linux Testing guide</A></B>
<UL>
<LI><A HREF="#22_1">Preliminary Notes on BIND</A></LI>
<LI><A HREF="#22_2">Steps to Install UML for FreeS/WAN</A></LI>
</UL>
<B><A HREF="#23">Debugging the kernel with GDB</A></B>
<UL>
<LI><A HREF="#23_1">Other notes about debugging</A></LI>
</UL>
<B><A HREF="#24">User-Mode-Linux mysteries</A></B>
<BR>
<BR><B><A HREF="#25">Getting more info from uml_netjig</A></B>
<BR>
<BR><B><A HREF="#politics">History and politics of cryptography</A></B>
<UL>
<LI><A HREF="#intro.politics">Introduction</A></LI>
<UL>
<LI><A HREF="#26_1_1">History</A></LI>
<UL>
<LI><A HREF="#26_1_1_1">World War II</A></LI>
<LI><A HREF="#postwar">Postwar and Cold War</A></LI>
<LI><A HREF="#recent">Recent history -- the crypto wars</A></LI>
</UL>
<LI><A HREF="#intro.poli">Politics</A></LI>
<LI><A HREF="#26_1_3">Links</A></LI>
<LI><A HREF="#26_1_4">Outline of this section</A></LI>
</UL>
<LI><A HREF="#leader">From our project leader</A></LI>
<UL>
<LI><A HREF="#gilmore">Swan: Securing the Internet against Wiretapping</A>
</LI>
<UL>
<LI><A HREF="#26_2_1_1">Deployment of IPSEC</A></LI>
<LI><A HREF="#26_2_1_2">Current status</A></LI>
<LI><A HREF="#26_2_1_3">Why?</A></LI>
<LI><A HREF="#26_2_1_4">What You Can Do</A></LI>
<LI><A HREF="#26_2_1_5">Related projects</A></LI>
</UL>
<LI><A HREF="#policestate">Stopping wholesale monitoring</A></LI>
</UL>
<LI><A HREF="#weak">Government promotion of weak crypto</A></LI>
<UL>
<LI><A HREF="#escrow">Escrowed encryption</A></LI>
<LI><A HREF="#shortkeys">Limited key lengths</A></LI>
<UL>
<LI><A HREF="#26_3_2_1">Some real trade-offs</A></LI>
</UL>
</UL>
<LI><A HREF="#exlaw">Cryptography Export Laws</A></LI>
<UL>
<LI><A HREF="#USlaw">US Law</A></LI>
<UL>
<LI><A HREF="#UScontrib">US contributions to FreeS/WAN</A></LI>
</UL>
<LI><A HREF="#wrong">What's wrong with restrictions on cryptography</A></LI>
<LI><A HREF="#Wassenaar">The Wassenaar Arrangement</A></LI>
<LI><A HREF="#status">Export status of Linux FreeS/WAN</A></LI>
<LI><A HREF="#help">Help spread IPsec around</A></LI>
</UL>
<LI><A HREF="#desnotsecure">DES is Not Secure</A></LI>
<UL>
<LI><A HREF="#deshware">Dedicated hardware breaks DES in a few days</A></LI>
<LI><A HREF="#spooks">Spooks may break DES faster yet</A></LI>
<LI><A HREF="#desnet">Networks break DES in a few weeks</A></LI>
<LI><A HREF="#no_des">We disable DES</A></LI>
<LI><A HREF="#40joke">40-bits is laughably weak</A></LI>
<LI><A HREF="#altdes">Triple DES is almost certainly secure</A></LI>
<LI><A HREF="#aes.ipsec">AES in IPsec</A></LI>
</UL>
<LI><A HREF="#press">Press coverage of Linux FreeS/WAN:</A></LI>
<UL>
<LI><A HREF="#26_6_1">FreeS/WAN 1.0 press</A></LI>
<LI><A HREF="#release">Press release for version 1.0</A></LI>
</UL>
</UL>
<B><A HREF="#ipsec.detail">The IPsec protocols</A></B>
<UL>
<LI><A HREF="#27_1">Protocols and phases</A></LI>
<LI><A HREF="#others">Applying IPsec</A></LI>
<UL>
<LI><A HREF="#advantages">Advantages of IPsec</A></LI>
<LI><A HREF="#limitations">Limitations of IPsec</A></LI>
<LI><A HREF="#uses">IPsec is a general mechanism for securing IP</A></LI>
<LI><A HREF="#authonly">Using authentication without encryption</A></LI>
<LI><A HREF="#encnoauth">Encryption without authentication is dangerous</A>
</LI>
<LI><A HREF="#multilayer">Multiple layers of IPsec processing are
 possible</A></LI>
<LI><A HREF="#traffic.resist">Resisting traffic analysis</A></LI>
<UL>
<LI><A HREF="#extra">Using &quot;unnecessary&quot; encryption</A></LI>
<LI><A HREF="#multi-encrypt">Using multiple encryption</A></LI>
<LI><A HREF="#fewer">Using fewer tunnels</A></LI>
</UL>
</UL>
<LI><A HREF="#primitives">Cryptographic components</A></LI>
<UL>
<LI><A HREF="#block.cipher">Block ciphers</A></LI>
<LI><A HREF="#hash.ipsec">Hash functions</A></LI>
<UL>
<LI><A HREF="#hmac.ipsec">The HMAC construct</A></LI>
<LI><A HREF="#27_3_2_2">Choice of hash algorithm</A></LI>
</UL>
<LI><A HREF="#DH.keying">Diffie-Hellman key agreement</A></LI>
<LI><A HREF="#RSA.auth">RSA authentication</A></LI>
</UL>
<LI><A HREF="#structure">Structure of IPsec</A></LI>
<UL>
<LI><A HREF="#IKE.ipsec">IKE (Internet Key Exchange)</A></LI>
<UL>
<LI><A HREF="#phases">Phases of IKE</A></LI>
<LI><A HREF="#sequence">Sequence of messages in IKE</A></LI>
<LI><A HREF="#struct.exchange">Structure of IKE messages</A></LI>
</UL>
<LI><A HREF="#services">IPsec Services, AH and ESP</A></LI>
<LI><A HREF="#AH.ipsec">The Authentication Header (AH)</A></LI>
<UL>
<LI><A HREF="#keyed">Keyed MD5 and Keyed SHA</A></LI>
<LI><A HREF="#sequence">Sequence numbers</A></LI>
</UL>
<LI><A HREF="#ESP.ipsec">Encapsulated Security Payload (ESP)</A></LI>
</UL>
<LI><A HREF="#modes">IPsec modes</A></LI>
<UL>
<LI><A HREF="#tunnel.ipsec">Tunnel mode</A></LI>
<LI><A HREF="#transport.ipsec">Transport mode</A></LI>
</UL>
<LI><A HREF="#parts">FreeS/WAN parts</A></LI>
<UL>
<LI><A HREF="#KLIPS.ipsec">KLIPS: Kernel IPsec Support</A></LI>
<LI><A HREF="#Pluto.ipsec">The Pluto daemon</A></LI>
<LI><A HREF="#command">The ipsec(8) command</A></LI>
<LI><A HREF="#ipsec.conf">Linux FreeS/WAN configuration file</A></LI>
</UL>
<LI><A HREF="#key">Key management</A></LI>
<UL>
<LI><A HREF="#current">Currently Implemented Methods</A></LI>
<UL>
<LI><A HREF="#manual">Manual keying</A></LI>
<LI><A HREF="#auto">Automatic keying</A></LI>
</UL>
<LI><A HREF="#notyet">Methods not yet implemented</A></LI>
<UL>
<LI><A HREF="#noauth">Unauthenticated key exchange</A></LI>
<LI><A HREF="#DNS">Key exchange using DNS</A></LI>
<LI><A HREF="#PKI">Key exchange using a PKI</A></LI>
<LI><A HREF="#photuris">Photuris</A></LI>
<LI><A HREF="#skip">SKIP</A></LI>
</UL>
</UL>
</UL>
<B><A HREF="#lists">Mailing lists and newsgroups</A></B>
<UL>
<LI><A HREF="#list.fs">Mailing lists about FreeS/WAN</A></LI>
<UL>
<LI><A HREF="#projlist">The project mailing lists</A></LI>
<UL>
<LI><A HREF="#which.list">Which list should I use?</A></LI>
<LI><A HREF="#policy.list">List policies</A></LI>
</UL>
<LI><A HREF="#archive">Archives of the lists</A></LI>
</UL>
<LI><A HREF="#indexes">Indexes of mailing lists</A></LI>
<LI><A HREF="#otherlists">Lists for related software and topics</A></LI>
<UL>
<LI><A HREF="#28_3_1">Products that include FreeS/WAN</A></LI>
<LI><A HREF="#linux.lists">Linux mailing lists</A></LI>
<LI><A HREF="#ietf">Lists for IETF working groups</A></LI>
<LI><A HREF="#other">Other mailing lists</A></LI>
</UL>
<LI><A HREF="#newsgroups">Usenet newsgroups</A></LI>
</UL>
<B><A HREF="#weblink">Web links</A></B>
<UL>
<LI><A HREF="#freeswan">The Linux FreeS/WAN Project</A></LI>
<UL>
<LI><A HREF="#patch">Add-ons and patches for FreeS/WAN</A></LI>
<UL>
<LI><A HREF="#29_1_1_1">Current patches</A></LI>
<LI><A HREF="#29_1_1_2">Older patches</A></LI>
<LI><A HREF="#VPN.masq">VPN masquerade patches</A></LI>
</UL>
<LI><A HREF="#dist">Distributions including FreeS/WAN</A></LI>
<LI><A HREF="#used">Things FreeS/WAN uses or could use</A></LI>
<LI><A HREF="#alternatives">Other approaches to VPNs for Linux</A></LI>
</UL>
<LI><A HREF="#ipsec.link">The IPsec Protocols</A></LI>
<UL>
<LI><A HREF="#general">General IPsec or VPN information</A></LI>
<LI><A HREF="#overview">IPsec overview documents or slide sets</A></LI>
<LI><A HREF="#otherlang">IPsec information in languages other than
 English</A></LI>
<LI><A HREF="#RFCs1">RFCs and other reference documents</A></LI>
<LI><A HREF="#analysis">Analysis and critiques of IPsec protocols</A></LI>
<LI><A HREF="#IP.background">Background information on IP</A></LI>
</UL>
<LI><A HREF="#implement">IPsec Implementations</A></LI>
<UL>
<LI><A HREF="#linuxprod">Linux products</A></LI>
<LI><A HREF="#router">IPsec in router products</A></LI>
<LI><A HREF="#fw.web">IPsec in firewall products</A></LI>
<LI><A HREF="#ipsecos">Operating systems with IPsec support</A></LI>
<LI><A HREF="#29_3_5">IPsec on network cards</A></LI>
<LI><A HREF="#opensource">Open source IPsec implementations</A></LI>
<UL>
<LI><A HREF="#linuxipsec">Other Linux IPsec implementations</A></LI>
<LI><A HREF="#BSD">IPsec for BSD Unix</A></LI>
<LI><A HREF="#misc">IPsec for other systems</A></LI>
</UL>
<LI><A HREF="#interop.web">Interoperability</A></LI>
<UL>
<LI><A HREF="#result">Interoperability results</A></LI>
<LI><A HREF="#test1">Interoperability test sites</A></LI>
</UL>
</UL>
<LI><A HREF="#linux.link">Linux links</A></LI>
<UL>
<LI><A HREF="#linux.basic">Basic and tutorial Linux information</A></LI>
<LI><A HREF="#general">General Linux sites</A></LI>
<LI><A HREF="#docs.ldp">Documentation</A></LI>
<LI><A HREF="#advroute.web">Advanced routing</A></LI>
<LI><A HREF="#linsec">Security for Linux</A></LI>
<LI><A HREF="#firewall.linux">Linux firewalls</A></LI>
<LI><A HREF="#linux.misc">Miscellaneous Linux information</A></LI>
</UL>
<LI><A HREF="#crypto.link">Crypto and security links</A></LI>
<UL>
<LI><A HREF="#security">Crypto and security resources</A></LI>
<UL>
<LI><A HREF="#std.links">The standard link collections</A></LI>
<LI><A HREF="#FAQ">Frequently Asked Question (FAQ) documents</A></LI>
<LI><A HREF="#cryptover">Tutorials</A></LI>
<LI><A HREF="#standards">Crypto and security standards</A></LI>
<LI><A HREF="#quotes">Crypto quotes</A></LI>
</UL>
<LI><A HREF="#policy">Cryptography law and policy</A></LI>
<UL>
<LI><A HREF="#legal">Surveys of crypto law</A></LI>
<LI><A HREF="#oppose">Organisations opposing crypto restrictions</A></LI>
<LI><A HREF="#other.policy">Other information on crypto policy</A></LI>
</UL>
<LI><A HREF="#crypto.tech">Cryptography technical information</A></LI>
<UL>
<LI><A HREF="#cryptolinks">Collections of crypto links</A></LI>
<LI><A HREF="#papers">Lists of online cryptography papers</A></LI>
<LI><A HREF="#interesting">Particularly interesting papers</A></LI>
</UL>
<LI><A HREF="#compsec">Computer and network security</A></LI>
<UL>
<LI><A HREF="#seclink">Security links</A></LI>
<LI><A HREF="#firewall.web">Firewall links</A></LI>
<LI><A HREF="#vpn">VPN links</A></LI>
<LI><A HREF="#tools">Security tools</A></LI>
</UL>
<LI><A HREF="#people">Links to home pages</A></LI>
</UL>
</UL>
<B><A HREF="#ourgloss">Glossary for the Linux FreeS/WAN project</A></B>
<UL>
<LI><A HREF="#jump">Jump to a letter in the glossary</A></LI>
<LI><A HREF="#gloss">Other glossaries</A></LI>
<LI><A HREF="#definitions">Definitions</A></LI>
</UL>
<B><A HREF="#biblio">Bibliography for the Linux FreeS/WAN project</A></B>
<BR>
<BR><B><A HREF="#RFC">IPsec RFCs and related documents</A></B>
<UL>
<LI><A HREF="#RFCfile">The RFCs.tar.gz Distribution File</A></LI>
<LI><A HREF="#sources">Other sources for RFCs &amp; Internet drafts</A></LI>
<UL>
<LI><A HREF="#RFCdown">RFCs</A></LI>
<LI><A HREF="#drafts">Internet Drafts</A></LI>
<LI><A HREF="#FIPS1">FIPS standards</A></LI>
</UL>
<LI><A HREF="#RFCs.tar.gz">What's in the RFCs.tar.gz bundle?</A></LI>
<UL>
<LI><A HREF="#rfc.ov">Overview RFCs</A></LI>
<LI><A HREF="#basic.prot">Basic protocols</A></LI>
<LI><A HREF="#key.ike">Key management</A></LI>
<LI><A HREF="#rfc.detail">Details of various things used</A></LI>
<LI><A HREF="#rfc.ref">Older RFCs which may be referenced</A></LI>
<LI><A HREF="#rfc.dns">RFCs for secure DNS service, which IPsec may use</A>
</LI>
<LI><A HREF="#rfc.exp">RFCs labelled &quot;experimental&quot;</A></LI>
<LI><A HREF="#rfc.rel">Related RFCs</A></LI>
</UL>
</UL>
<B><A HREF="#roadmap">Distribution Roadmap: What's Where in Linux
 FreeS/WAN</A></B>
<UL>
<LI><A HREF="#top">Top directory</A></LI>
<LI><A HREF="#doc">Documentation</A></LI>
<LI><A HREF="#klips.roadmap">KLIPS: kernel IP security</A></LI>
<LI><A HREF="#pluto.roadmap">Pluto key and connection management daemon</A>
</LI>
<LI><A HREF="#utils">Utils</A></LI>
<LI><A HREF="#lib">Libraries</A></LI>
<UL>
<LI><A HREF="#fswanlib">FreeS/WAN Library</A></LI>
<LI><A HREF="#otherlib">Imported Libraries</A></LI>
<UL>
<LI><A HREF="#33_6_2_1">LibDES</A></LI>
<LI><A HREF="#33_6_2_2">GMP</A></LI>
</UL>
</UL>
</UL>
<B><A HREF="#umltesting">User-Mode-Linux Testing guide</A></B>
<UL>
<LI><A HREF="#34_1">Preliminary Notes on BIND</A></LI>
<LI><A HREF="#34_2">Steps to Install UML for FreeS/WAN</A></LI>
</UL>
<B><A HREF="#35">Debugging the kernel with GDB</A></B>
<UL>
<LI><A HREF="#35_1">Other notes about debugging</A></LI>
</UL>
<B><A HREF="#36">User-Mode-Linux mysteries</A></B>
<BR>
<BR><B><A HREF="#37">Getting more info from uml_netjig</A></B>
<BR>
<BR><B><A HREF="#makecheck">How to configure to use &quot;make check&quot;</A></B>
<UL>
<LI><A HREF="#38_1">What is &quot;make check&quot;</A></LI>
<LI><A HREF="#38_2">Running &quot;make check&quot;</A></LI>
</UL>
<B><A HREF="#39">How to write a &quot;make check&quot; test</A></B>
<UL>
<LI><A HREF="#39_1">Structure of a test</A></LI>
<LI><A HREF="#39_2">The TESTLIST</A></LI>
<LI><A HREF="#39_3">Test kinds</A></LI>
<LI><A HREF="#39_4">Common parameters</A></LI>
<LI><A HREF="#39_5">KLIPStest paramaters</A></LI>
<LI><A HREF="#39_6">mkinsttest paramaters</A></LI>
<LI><A HREF="#39_7">rpm_build_install_test paramaters</A></LI>
<LI><A HREF="#39_8">libtest paramaters</A></LI>
<LI><A HREF="#39_9">umlplutotest paramaters</A></LI>
<LI><A HREF="#39_10">umlXhost parameters</A></LI>
<LI><A HREF="#39_11">kernel_patch_test paramaters</A></LI>
<LI><A HREF="#39_12">module_compile paramaters</A></LI>
</UL>
<B><A HREF="#40">Current pitfalls</A></B>
<BR>
<BR><B><A HREF="#nightly">Nightly regression testing</A></B>
<BR>
<BR><B><A HREF="#nightlyhowto">How to setup the nightly build</A></B>
<UL>
<LI><A HREF="#42_1"> Files you need to know about</A></LI>
<LI><A HREF="#42_2">Configuring freeswan-regress-env.sh</A></LI>
</UL>
<HR>
<H1><A name="intro">Introduction</A></H1>
<P>This section gives an overview of:</P>
<UL>
<LI>what IP Security (IPsec) does</LI>
<LI>how IPsec works</LI>
<LI>why we are implementing it for Linux</LI>
<LI>how this implementation works</LI>
</UL>
<P>This section is intended to cover only the essentials,<EM> things you
 should know before trying to use FreeS/WAN.</EM></P>
<P>For more detailed background information, see the<A href="#politics">
 history and politics</A> and<A href="#ipsec.detail"> IPsec protocols</A>
 sections.</P>
<H2><A name="ipsec.intro">IPsec, Security for the Internet Protocol</A></H2>
<P>FreeS/WAN is a Linux implementation of the IPsec (IP security)
 protocols. IPsec provides<A href="#encryption"> encryption</A> and<A href="#authentication">
 authentication</A> services at the IP (Internet Protocol) level of the
 network protocol stack.</P>
<P>Working at this level, IPsec can protect any traffic carried over IP,
 unlike other encryption which generally protects only a particular
 higher-level protocol --<A href="#PGP"> PGP</A> for mail,<A href="#ssh">
 SSH</A> for remote login,<A href="#SSL"> SSL</A> for web work, and so
 on. This approach has both considerable advantages and some
 limitations. For discussion, see our<A href="#others"> IPsec section</A>
</P>
<P>IPsec can be used on any machine which does IP networking. Dedicated
 IPsec gateway machines can be installed wherever required to protect
 traffic. IPsec can also run on routers, on firewall machines, on
 various application servers, and on end-user desktop or laptop
 machines.</P>
<P>Three protocols are used</P>
<UL>
<LI><A href="#AH">AH</A> (Authentication Header) provides a packet-level
 authentication service</LI>
<LI><A href="#ESP">ESP</A> (Encapsulating Security Payload) provides
 encryption plus authentication</LI>
<LI><A href="#IKE">IKE</A> (Internet Key Exchange) negotiates connection
 parameters, including keys, for the other two</LI>
</UL>
<P>Our implementation has three main parts:</P>
<UL>
<LI><A href="#KLIPS">KLIPS</A> (kernel IPsec) implements AH, ESP, and
 packet handling within the kernel</LI>
<LI><A href="#Pluto">Pluto</A> (an IKE daemon) implements IKE,
 negotiating connections with other systems</LI>
<LI>various scripts provide an adminstrator's interface to the machinery</LI>
</UL>
<P>IPsec is optional for the current (version 4) Internet Protocol.
 FreeS/WAN adds IPsec to the Linux IPv4 network stack. Implementations
 of<A href="#ipv6.gloss"> IP version 6</A> are required to include
 IPsec. Work toward integrating FreeS/WAN into the Linux IPv6 stack has<A
href="#ipv6"> started</A>.</P>
<P>For more information on IPsec, see our<A href="#ipsec.detail"> IPsec
 protocols</A> section, our collection of<A href="#ipsec.link"> IPsec
 links</A> or the<A href="#RFC"> RFCs</A> which are the official
 definitions of these protocols.</P>
<H3><A name="intro.interop">Interoperating with other IPsec
 implementations</A></H3>
<P>IPsec is designed to let different implementations work together. We
 provide:</P>
<UL>
<LI>a<A href="#implement"> list</A> of some other implementations</LI>
<LI>information on<A href="#interop"> using FreeS/WAN with other
 implementations</A></LI>
</UL>
<P>The VPN Consortium fosters cooperation among implementers and
 interoperability among implementations. Their<A href="http://www.vpnc.org/">
 web site</A> has much more information.</P>
<H3><A name="advantages">Advantages of IPsec</A></H3>
<P>IPsec has a number of security advantages. Here are some
 independently written articles which discuss these:</P>
<P><A HREF="http://www.sans.org/rr/"> SANS institute papers</A>. See the
 section on Encryption &amp;VPNs.
<BR><A HREF="http://www.cisco.com/en/US/netsol/ns110/ns170/ns171/ns128/networking_solutions_white_papers_list.html">
 Cisco's white papers on &quot;Networking Solutions&quot;</A>.
<BR><A HREF="http://iscs.sourceforge.net/HowWhyBrief/HowWhyBrief.html">
 Advantages of ISCS (Linux Integrated Secure Communications System;
 includes FreeS/WAN and other software)</A>.</P>
<H3><A name="applications">Applications of IPsec</A></H3>
<P>Because IPsec operates at the network layer, it is remarkably
 flexible and can be used to secure nearly any type of Internet traffic.
 Two applications, however, are extremely widespread:</P>
<UL>
<LI>a<A href="#VPN"> Virtual Private Network</A>, or VPN, allows
 multiple sites to communicate securely over an insecure Internet by
 encrypting all communication between the sites.</LI>
<LI>&quot;Road Warriors&quot; connect to the office from home, or perhaps from a
 hotel somewhere</LI>
</UL>
<P>There is enough opportunity in these applications that vendors are
 flocking to them. IPsec is being built into routers, into firewall
 products, and into major operating systems, primarily to support these
 applications. See our<A href="#implement"> list</A> of implementations
 for details.</P>
<P>We support both of those applications, and various less common IPsec
 applications as well, but we also add one of our own:</P>
<UL>
<LI>opportunistic encryption, the ability to set up FreeS/WAN gateways
 so that any two of them can encrypt to each other, and will do so
 whenever packets pass between them.</LI>
</UL>
<P>This is an extension we are adding to the protocols. FreeS/WAN is the
 first prototype implementation, though we hope other IPsec
 implementations will adopt the technique once we demonstrate it. See<A href="#goals">
 project goals</A> below for why we think this is important.</P>
<P>A somewhat more detailed description of each of these applications is
 below. Our<A href="#quick_guide"> quickstart</A> section will show you
 how to build each of them.</P>
<H4><A name="makeVPN">Using secure tunnels to create a VPN</A></H4>
<P>A VPN, or<STRONG> V</STRONG>irtual<STRONG> P</STRONG>rivate<STRONG> N</STRONG>
etwork lets two networks communicate securely when the only connection
 between them is over a third network which they do not trust.</P>
<P>The method is to put a security gateway machine between each of the
 communicating networks and the untrusted network. The gateway machines
 encrypt packets entering the untrusted net and decrypt packets leaving
 it, creating a secure tunnel through it.</P>
<P>If the cryptography is strong, the implementation is careful, and the
 administration of the gateways is competent, then one can reasonably
 trust the security of the tunnel. The two networks then behave like a
 single large private network, some of whose links are encrypted tunnels
 through untrusted nets.</P>
<P>Actual VPNs are often more complex. One organisation may have fifty
 branch offices, plus some suppliers and clients, with whom it needs to
 communicate securely. Another might have 5,000 stores, or 50,000
 point-of-sale devices. The untrusted network need not be the Internet.
 All the same issues arise on a corporate or institutional network
 whenever two departments want to communicate privately with each other.</P>
<P>Administratively, the nice thing about many VPN setups is that large
 parts of them are static. You know the IP addresses of most of the
 machines involved. More important, you know they will not change on
 you. This simplifies some of the admin work. For cases where the
 addresses do change, see the next section.</P>
<H4><A name="road.intro">Road Warriors</A></H4>
<P>The prototypical &quot;Road Warrior&quot; is a traveller connecting to home
 base from a laptop machine. Administratively, most of the same problems
 arise for a telecommuter connecting from home to the office, especially
 if the telecommuter does not have a static IP address.</P>
<P>For purposes of this document:</P>
<UL>
<LI>anyone with a dynamic IP address is a &quot;Road Warrior&quot;.</LI>
<LI>any machine doing IPsec processing is a &quot;gateway&quot;. Think of the
 single-user road warrior machine as a gateway with a degenerate subnet
 (one machine, itself) behind it.</LI>
</UL>
<P>These require somewhat different setup than VPN gateways with static
 addresses and with client systems behind them, but are basically not
 problematic.</P>
<P>There are some difficulties which appear for some road warrior
 connections:</P>
<UL>
<LI>Road Wariors who get their addresses via DHCP may have a problem.
 FreeS/WAN can quite happily build and use a tunnel to such an address,
 but when the DHCP lease expires, FreeS/WAN does not know that. The
 tunnel fails, and the only recovery method is to tear it down and
 re-build it.</LI>
<LI>If<A href="#NAT.gloss"> Network Address Translation</A> (NAT) is
 applied between the two IPsec Gateways, this breaks IPsec. IPsec
 authenticates packets on an end-to-end basis, to ensure they are not
 altered en route. NAT rewrites packets as they go by. See our<A href="#NAT">
 firewalls</A> document for details.</LI>
</UL>
<P>In most situations, however, FreeS/WAN supports road warrior
 connections just fine.</P>
<H4><A name="opp.intro">Opportunistic encryption</A></H4>
<P>One of the reasons we are working on FreeS/WAN is that it gives us
 the opportunity to add what we call opportuntistic encryption. This
 means that any two FreeS/WAN gateways will be able to encrypt their
 traffic, even if the two gateway administrators have had no prior
 contact and neither system has any preset information about the other.</P>
<P>Both systems pick up the authentication information they need from
 the<A href="#DNS"> DNS</A> (domain name service), the service they
 already use to look up IP addresses. Of course the administrators must
 put that information in the DNS, and must set up their gateways with
 opportunistic encryption enabled. Once that is done, everything is
 automatic. The gateways look for opportunities to encrypt, and encrypt
 whatever they can. Whether they also accept unencrypted communication
 is a policy decision the administrator can make.</P>
<P>This technique can give two large payoffs:</P>
<UL>
<LI>It reduces the administrative overhead for IPsec enormously. You
 configure your gateway and thereafter everything is automatic. The need
 to configure the system on a per-tunnel basis disappears. Of course,
 FreeS/WAN allows specifically configured tunnels to co-exist with
 opportunistic encryption, but we hope to make them unnecessary in most
 cases.</LI>
<LI>It moves us toward a more secure Internet, allowing users to create
 an environment where message privacy is the default. All messages can
 be encrypted, provided the other end is willing to co-operate. See our<A
href="#politics"> history and politics of cryptography</A> section for
 discussion of why we think this is needed.</LI>
</UL>
<P>Opportunistic encryption is not (yet?) a standard part of the IPsec
 protocols, but an extension we are proposing and demonstrating. For
 details of our design, see<A href="#applied"> links</A> below.</P>
<P>Only one current product we know of implements a form of
 opportunistic encryption.<A href="#ssmail"> Secure sendmail</A> will
 automatically encrypt server-to-server mail transfers whenever
 possible.</P>
<H3><A name="types">The need to authenticate gateways</A></H3>
<P>A complication, which applies to any type of connection -- VPN, Road
 Warrior or opportunistic -- is that a secure connection cannot be
 created magically.<EM> There must be some mechanism which enables the
 gateways to reliably identify each other.</EM> Without this, they
 cannot sensibly trust each other and cannot create a genuinely secure
 link.</P>
<P>Any link they do create without some form of<A href="#authentication">
 authentication</A> will be vulnerable to a<A href="#middle">
 man-in-the-middle attack</A>. If<A href="#alicebob"> Alice and Bob</A>
 are the people creating the connection, a villian who can re-route or
 intercept the packets can pose as Alice while talking to Bob and pose
 as Bob while talking to Alice. Alice and Bob then both talk to the man
 in the middle, thinking they are talking to each other, and the villain
 gets everything sent on the bogus &quot;secure&quot; connection.</P>
<P>There are two ways to build links securely, both of which exclude the
 man-in-the middle:</P>
<UL>
<LI>with<STRONG> manual keying</STRONG>, Alice and Bob share a secret
 key (which must be transmitted securely, perhaps in a note or via PGP
 or SSH) to encrypt their messages. For FreeS/WAN, such keys are stored
 in the<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf(5)</A> file. Of
 course, if an enemy gets the key, all is lost.</LI>
<LI>with<STRONG> automatic keying</STRONG>, the two systems authenticate
 each other and negotiate their own secret keys. The keys are
 automatically changed periodically.</LI>
</UL>
<P>Automatic keying is much more secure, since if an enemy gets one key
 only messages between the previous re-keying and the next are exposed.
 It is therefore the usual mode of operation for most IPsec deployment,
 and the mode we use in our setup examples. FreeS/WAN does support
 manual keying for special circumstanes. See this<A href="#prodman">
 section</A>.</P>
<P>For automatic keying, the two systems must authenticate each other
 during the negotiations. There is a choice of methods for this:</P>
<UL>
<LI>a<STRONG> shared secret</STRONG> provides authentication. If Alice
 and Bob are the only ones who know a secret and Alice recives a message
 which could not have been created without that secret, then Alice can
 safely believe the message came from Bob.</LI>
<LI>a<A href="#public"> public key</A> can also provide authentication.
 If Alice receives a message signed with Bob's private key (which of
 course only he should know) and she has a trustworthy copy of his
 public key (so that she can verify the signature), then she can safely
 believe the message came from Bob.</LI>
</UL>
<P>Public key techniques are much preferable, for reasons discussed<A href="#choose">
 later</A>, and will be used in all our setup examples. FreeS/WAN does
 also support auto-keying with shared secret authentication. See this<A href="#prodsecrets">
 section</A>.</P>
<H2><A name="project">The FreeS/WAN project</A></H2>
<P>For complete information on the project, see our web site,<A href="http://liberty.freeswan.org">
 freeswan.org</A>.</P>
<P>In summary, we are implementing the<A href="#IPSEC"> IPsec</A>
 protocols for Linux and extending them to do<A href="#carpediem">
 opportunistic encryption</A>.</P>
<H3><A name="goals">Project goals</A></H3>
<P>Our overall goal in FreeS/WAN is to make the Internet more secure and
 more private.</P>
<P>Our IPsec implementation supports VPNs and Road Warriors of course.
 Those are important applications. Many users will want FreeS/WAN to
 build corporate VPNs or to provide secure remote access.</P>
<P>However, our goals in building it go beyond that. We are trying to
 help<STRONG> build security into the fabric of the Internet</STRONG> so
 that anyone who choses to communicate securely can do so, as easily as
 they can do anything else on the net.</P>
<P>More detailed objectives are:</P>
<UL>
<LI>extend IPsec to do<A href="#carpediem"> opportunistic encryption</A>
 so that
<UL>
<LI>any two systems can secure their communications without a
 pre-arranged connection</LI>
<LI><STRONG>secure connections can be the default</STRONG>, falling back
 to unencrypted connections only if:
<UL>
<LI><EM>both</EM> the partner is not set up to co-operate on securing
 the connection</LI>
<LI><EM>and</EM> your policy allows insecure connections</LI>
</UL>
</LI>
<LI>a significant fraction of all Internet traffic is encrypted</LI>
<LI>wholesale monitoring of the net (<A href="#intro.poli">examples</A>)
 becomes difficult or impossible</LI>
</UL>
</LI>
<LI>help make IPsec widespread by providing an implementation with no
 restrictions:
<UL>
<LI>freely available in source code under the<A href="#GPL"> GNU General
 Public License</A></LI>
<LI>running on a range of readily available hardware</LI>
<LI>not subject to US or other nations'<A href="#exlaw"> export
 restrictions</A>.
<BR> Note that in order to avoid<EM> even the appearance</EM> of being
 subject to those laws, the project cannot accept software contributions
 --<EM> not even one-line bug fixes</EM> -- from US residents or
 citizens.</LI>
</UL>
</LI>
<LI>provide a high-quality IPsec implementation for Linux
<UL>
<LI>portable to all CPUs Linux supports:<A href="#CPUs"> (current list)</A>
</LI>
<LI>interoperable with other IPsec implementations:<A href="#interop">
 (current list)</A></LI>
</UL>
</LI>
</UL>
<P>If we can get opportunistic encryption implemented and widely
 deployed, then it becomes impossible for even huge well-funded agencies
 to monitor the net.</P>
<P>See also our section on<A href="#politics"> history and politics</A>
 of cryptography, which includes our project leader's<A href="#gilmore">
 rationale</A> for starting the project.</P>
<H3><A name="staff">Project team</A></H3>
<P>Two of the team are from the US and can therefore contribute no code:</P>
<UL>
<LI>John Gilmore: founder and policy-maker (<A href="http://www.toad.com/gnu/">
home page</A>)</LI>
<LI>Hugh Daniel: project manager, Most Demented Tester, and occasionally
 Pointy-Haired Boss</LI>
</UL>
<P>The rest of the team are Canadians, working in Canada. (<A href="#status">
Why Canada?</A>)</P>
<UL>
<LI>Hugh Redelmeier:<A href="#Pluto"> Pluto daemon</A> programmer</LI>
<LI>Richard Guy Briggs:<A href="#KLIPS"> KLIPS</A> programmer</LI>
<LI>Michael Richardson: hacker without portfolio</LI>
<LI>Claudia Schmeing: documentation</LI>
<LI>Sam Sgro: technical support via the<A href="#lists"> mailing lists</A>
</LI>
</UL>
<P>The project is funded by civil libertarians who consider our goals
 worthwhile. Most of the team are paid for this work.</P>
<P>People outside this core team have made substantial contributions.
 See</P>
<UL>
<LI>our<A href="../CREDITS"> CREDITS</A> file</LI>
<LI>the<A href="#patch"> patches and add-ons</A> section of our web
 references file</LI>
<LI>lists below of user-written<A href="#howto"> HowTos</A> and<A href="#applied">
 other papers</A></LI>
</UL>
<P>Additional contributions are welcome. See the<A href="#contrib.faq">
 FAQ</A> for details.</P>
<H2><A name="products">Products containing FreeS/WAN</A></H2>
<P>Unfortunately the<A href="#exlaw"> export laws</A> of some countries
 restrict the distribution of strong cryptography. FreeS/WAN is
 therefore not in the standard Linux kernel and not in all CD or web
 distributions.</P>
<P>FreeS/WAN is, however, quite widely used. Products we know of that
 use it are listed below. We would appreciate hearing, via the<A href="#lists">
 mailing lists</A>, of any we don't know of.</P>
<H3><A name="distwith">Full Linux distributions</A></H3>
<P>FreeS/WAN is included in various general-purpose Linux distributions,
 mostly from countries (shown in brackets) with more sensible laws:</P>
<UL>
<LI><A href="http://www.suse.com/">SuSE Linux</A> (Germany)</LI>
<LI><A href="http://www.conectiva.com">Conectiva</A> (Brazil)</LI>
<LI><A href="http://www.linux-mandrake.com/en/">Mandrake</A> (France)</LI>
<LI><A href="http://www.debian.org">Debian</A></LI>
<LI>the<A href="http://www.pld.org.pl/"> Polish(ed) Linux Distribution</A>
 (Poland)</LI>
<LI><A>Best Linux</A> (Finland)</LI>
</UL>
<P>For distributions which do not include FreeS/WAN and are not Redhat
 (which we develop and test on), there is additional information in our<A
href="#otherdist"> compatibility</A> section.</P>
<P>The server edition of<A href="http://www.corel.com"> Corel</A> Linux
 (Canada) also had FreeS/WAN, but Corel have dropped that product line.</P>
<H3><A name="kernel_dist">Linux kernel distributions</A></H3>
<UL>
<LI><A href="http://sourceforge.net/projects/wolk/">Working Overloaded
 Linux Kernel (WOLK)</A></LI>
</UL>
<H3><A name="office_dist">Office server distributions</A></H3>
<P>FreeS/WAN is also included in several distributions aimed at the
 market for turnkey business servers:</P>
<UL>
<LI><A href="http://www.e-smith.com/">e-Smith</A> (Canada), which has
 recently been acquired and become the Network Server Solutions group of<A
href="http://www.mitel.com/"> Mitel Networks</A> (Canada)</LI>
<LI><A href="http://www.clarkconnect.org/">ClarkConnect</A> from Point
 Clark Networks (Canada)</LI>
<LI><A href="http://www.trustix.net/">Trustix Secure Linux</A> (Norway)</LI>
</UL>
<H3><A name="fw_dist">Firewall distributions</A></H3>
<P>Several distributions intended for firewall and router applications
 include FreeS/WAN:</P>
<UL>
<LI>The<A href="http://www.linuxrouter.org/"> Linux Router Project</A>
 produces a Linux distribution that will boot from a single floppy. The<A
href="http://leaf.sourceforge.net"> LEAF</A> firewall project provides
 several different LRP-based firewall packages. At least one of them,
 Charles Steinkuehler's Dachstein, includes FreeS/WAN with X.509
 patches.</LI>
<LI>there are several distributions bootable directly from CD-ROM,
 usable on a machine without hard disk.
<UL>
<LI>Dachstein (see above) can be used this way</LI>
<LI><A href="http://www.gibraltar.at/">Gibraltar</A> is based on Debian
 GNU/Linux.</LI>
<LI>at time of writing,<A href="www.xiloo.com"> Xiloo</A> is available
 only in Chinese. An English version is expected.</LI>
</UL>
</LI>
<LI><A href="http://www.astaro.com/products/index.html">Astaro Security
 Linux</A> includes FreeS/WAN. It has some web-based tools for managing
 the firewall that include FreeS/WAN configuration management.</LI>
<LI><A href="http://www.linuxwall.de">Linuxwall</A></LI>
<LI><A href="http://www.smoothwall.org/">Smoothwall</A></LI>
<LI><A href="http://www.devil-linux.org/">Devil Linux</A></LI>
<LI>Coyote Linux has a<A href="http://embedded.coyotelinux.com/wolverine/index.php">
 Wolverine</A> firewall/VPN server</LI>
</UL>
<P>There are also several sets of scripts available for managing a
 firewall which is also acting as a FreeS/WAN IPsec gateway. See this<A href="#rules.pub">
 list</A>.</P>
<H3><A name="turnkey">Firewall and VPN products</A></H3>
<P>Several vendors use FreeS/WAN as the IPsec component of a turnkey
 firewall or VPN product.</P>
<P>Software-only products:</P>
<UL>
<LI><A href="http://www.linuxmagic.com/vpn/index.html">Linux Magic</A>
 offer a VPN/Firewall product using FreeS/WAN</LI>
<LI>The Software Group's<A href="http://www.wanware.com/sentinet/">
 Sentinet</A> product uses FreeS/WAN</LI>
<LI><A href="http://www.merilus.com">Merilus</A> use FreeS/WAN in their
 Gateway Guardian firewall product</LI>
</UL>
<P>Products that include the hardware:</P>
<UL>
<LI>The<A href="http://www.lasat.com"> LASAT SafePipe[tm]</A> series. is
 an IPsec box based on an embedded MIPS running Linux with FreeS/WAN and
 a web-config front end. This company also host our freeswan.org web
 site.</LI>
<LI>Merilus<A href="http://www.merilus.com/products/fc/index.shtml">
 Firecard</A> is a Linux firewall on a PCI card.</LI>
<LI><A href="http://www.kyzo.com/">Kyzo</A> have a &quot;pizza box&quot; product
 line with various types of server, all running from flash. One of them
 is an IPsec/PPTP VPN server</LI>
<LI><A href="http://www.pfn.com">PFN</A> use FreeS/WAN in some of their
 products</LI>
</UL>
<P><A href="www.rebel.com">Rebel.com</A>, makers of the Netwinder Linux
 machines (ARM or Crusoe based), had a product that used FreeS/WAN. The
 company is in receivership so the future of the Netwinder is at best
 unclear.<A href="#patch"> PKIX patches</A> for FreeS/WAN developed at
 Rebel are listed in our web links document.</P>
<H2><A name="docs">Information sources</A></H2>
<H3><A name="docformats">This HowTo, in multiple formats</A></H3>
<P>FreeS/WAN documentation up to version 1.5 was available only in HTML.
 Now we ship two formats:</P>
<UL>
<LI>as HTML, one file for each doc section plus a global<A href="toc.html">
 Table of Contents</A></LI>
<LI><A href="HowTo.html">one big HTML file</A> for easy searching</LI>
</UL>
<P>and provide a Makefile to generate other formats if required:</P>
<UL>
<LI><A href="HowTo.pdf">PDF</A></LI>
<LI><A href="HowTo.ps">Postscript</A></LI>
<LI><A href="HowTo.txt">ASCII text</A></LI>
</UL>
<P>The Makefile assumes the htmldoc tool is available. You can download
 it from<A href="http://www.easysw.com"> Easy Software</A>.</P>
<P>All formats should be available at the following websites:</P>
<UL>
<LI><A href="http://www.freeswan.org/doc.html">FreeS/WAN project</A></LI>
<LI><A href="http://www.linuxdoc.org">Linux Documentation Project</A></LI>
</UL>
<P>The distribution tarball has only the two HTML formats.</P>
<P><STRONG>Note:</STRONG> If you need the latest doc version, for
 example to see if anyone has managed to set up interoperation between
 FreeS/WAN and whatever, then you should download the current snapshot.
 What is on the web is documentation as of the last release. Snapshots
 have all changes I've checked in to date.</P>
<H3><A name="rtfm">RTFM (please Read The Fine Manuals)</A></H3>
<P>As with most things on any Unix-like system, most parts of Linux
 FreeS/WAN are documented in online manual pages. We provide a list of<A href="/mnt/floppy/manpages.html">
 FreeS/WAN man pages</A>, with links to HTML versions of them.</P>
<P>The man pages describing configuration files are:</P>
<UL>
<LI><A href="/mnt/floppy/manpage.d/ipsec.conf.5.html">ipsec.conf(5)</A></LI>
<LI><A href="/mnt/floppy/manpage.d/ipsec.secrets.5.html">
ipsec.secrets(5)</A></LI>
</UL>
<P>Man pages for common commands include:</P>
<UL>
<LI><A href="/mnt/floppy/manpage.d/ipsec.8.html">ipsec(8)</A></LI>
<LI><A href="/mnt/floppy/manpage.d/ipsec_pluto.8.html">ipsec_pluto(8)</A>
</LI>
<LI><A href="/mnt/floppy/manpage.d/ipsec_newhostkey.8.html">
ipsec_newhostkey(8)</A></LI>
<LI><A href="/mnt/floppy/manpage.d/ipsec_auto.8.html">ipsec_auto(8)</A></LI>
</UL>
<P>You can read these either in HTML using the links above or with the<VAR>
 man(1)</VAR> command.</P>
<P>In the event of disagreement between this HTML documentation and the
 man pages, the man pages are more likely correct since they are written
 by the implementers. Please report any such inconsistency on the<A href="#lists">
 mailing list</A>.</P>
<H3><A name="text">Other documents in the distribution</A></H3>
<P>Text files in the main distribution directory are README, INSTALL,
 CREDITS, CHANGES, BUGS and COPYING.</P>
<P>The Libdes encryption library we use has its own documentation. You
 can find it in the library directory..</P>
<H3><A name="assumptions">Background material</A></H3>
<P>Throughout this documentation, I write as if the reader had at least
 a general familiarity with Linux, with Internet Protocol networking,
 and with the basic ideas of system and network security. Of course that
 will certainly not be true for all readers, and quite likely not even
 for a majority.</P>
<P>However, I must limit amount of detail on these topics in the main
 text. For one thing, I don't understand all the details of those topics
 myself. Even if I did, trying to explain everything here would produce
 extremely long and almost completely unreadable documentation.</P>
<P>If one or more of those areas is unknown territory for you, there are
 plenty of other resources you could look at:</P>
<DL>
<DT>Linux</DT>
<DD>the<A href="http://www.linuxdoc.org"> Linux Documentation Project</A>
 or a local<A href="http://www.linux.org/groups/"> Linux User Group</A>
 and these<A href="#linux.link"> links</A></DD>
<DT>IP networks</DT>
<DD>Rusty Russell's<A href="http://netfilter.samba.org/unreliable-guides/networking-concepts-HOWTO/index.html">
 Networking Concepts HowTo</A> and these<A href="#IP.background"> links</A>
</DD>
<DT>Security</DT>
<DD>Schneier's book<A href="#secrets"> Secrets and Lies</A> and these<A href="#crypto.link">
 links</A></DD>
</DL>
<P>Also, I do make an effort to provide some background material in
 these documents. All the basic ideas behind IPsec and FreeS/WAN are
 explained here. Explanations that do not fit in the main text, or that
 not everyone will need, are often in the<A href="#ourgloss"> glossary</A>
, which is the largest single file in this document set. There is also a<A
href="#background"> background</A> file containing various explanations
 too long to fit in glossary definitions. All files are heavily
 sprinkled with links to each other and to the glossary.<STRONG> If some
 passage makes no sense to you, try the links</STRONG>.</P>
<P>For other reference material, see the<A href="#biblio"> bibliography</A>
 and our collection of<A href="web.html#weblinks"> web links</A>.</P>
<P>Of course, no doubt I get this (and other things) wrong sometimes.
 Feedback via the<A href="#lists"> mailing lists</A> is welcome.</P>
<H3><A name="archives">Archives of the project mailing list</A></H3>
<P>Until quite recently, there was only one FreeS/WAN mailing list, and
 archives of it were:</P>
<UL>
<LI><A href="http://www.sandelman.ottawa.on.ca/linux-ipsec">Canada</A></LI>
<LI><A href="http://www.nexial.com">Holland</A></LI>
</UL>
 The two archives use completely different search engines. You might
 want to try both.
<P>More recently we have expanded to five lists, each with its own
 archive.</P>
<P><A href="#lists">More information</A> on mailing lists.</P>
<H3><A name="howto">User-written HowTo information</A></H3>
<P>Various user-written HowTo documents are available. The ones covering
 FreeS/WAN-to-FreeS/WAN connections are:</P>
<UL>
<LI>Jean-Francois Nadeau's<A href="http://jixen.tripod.com/"> practical
 configurations</A> document</LI>
<LI>Jens Zerbst's HowTo on<A href="http://dynipsec.tripod.com/"> Using
 FreeS/WAN with dynamic IP addresses</A>.</LI>
<LI>an entry in Kurt Seifried's<A href="http://www.securityportal.com/lskb/kben00000013.html">
 Linux Security Knowledge Base</A>.</LI>
<LI>a section of David Ranch's<A href="http://www.ecst.csuchico.edu/~dranch/LINUX/index-linux.html#trinityos">
 Trinity OS Guide</A></LI>
<LI>a section in David Bander's book<A href="#bander"> Linux Security
 Toolkit</A></LI>
</UL>
<P>User-wriiten HowTo material may be<STRONG> especially helpful if you
 need to interoperate with another IPsec implementation</STRONG>. We
 have neither the equipment nor the manpower to test such
 configurations. Users seem to be doing an admirable job of filling the
 gaps.</P>
<UL>
<LI>list of user-written<A href="interop.html#otherpub"> interoperation
 HowTos</A> in our interop document</LI>
</UL>
<P>Check what version of FreeS/WAN user-written documents cover. The
 software is under active development and the current version may be
 significantly different from what an older document describes.</P>
<H3><A name="applied">Papers on FreeS/WAN</A></H3>
<P>Two design documents show team thinking on new developments:</P>
<UL>
<LI><A href="opportunism.spec">Opportunistic Encryption</A> by technical
 lead Henry Spencer and Pluto programmer Hugh Redelemeier</LI>
<LI>discussion of<A href="http://www.sandelman.ottawa.on.ca/SSW/freeswan/klips2req/">
 KLIPS redesign</A></LI>
</UL>
<P>Both documents are works in progress and are frequently revised. For
 the latest version, see the<A href="#lists"> design mailing list</A>.
 Comments should go to that list.</P>
<P>There is now an<A href="http://www.ietf.org/internet-drafts/draft-richardson-ipsec-opportunistic-06.txt">
 Internet Draft on Opportunistic Encryption</A> by Michael Richardson,
 Hugh Redelmeier and Henry Spencer. This is a first step toward getting
 the protocol standardised so there can be multiple implementations of
 it. Discussion of it takes place on the<A href="http://www.ietf.org/html.charters/ipsec-charter.html">
 IETF IPsec Working Group</A> mailing list.</P>
<P>A number of papers giving further background on FreeS/WAN, or
 exploring its future or its applications, are also available:</P>
<UL>
<LI>Both Henry and Richard gave talks on FreeS/WAN at the 2000<A href="http://www.linuxsymposium.org">
 Ottawa Linux Symposium</A>.
<UL>
<LI>Richard's<A href="http://www.conscoop.ottawa.on.ca/rgb/freeswan/ols2k/">
 slides</A></LI>
<LI>Henry's paper</LI>
<LI>MP3 audio of their talks is available from the<A href="http://www.linuxsymposium.org/">
 conference page</A></LI>
</UL>
</LI>
<LI><CITE>Moat: A Virtual Private Network Appliances and Services
 Platform</CITE> is a paper about large-scale (a few 100 links) use of
 FreeS/WAN in a production application at AT&amp;T Research. It is available
 in Postscript or PDF from co-author Steve Bellovin's<A href="http://www.research.att.com/~smb/papers/index.html">
 papers list page</A>.</LI>
<LI>One of the Moat co-authors, John Denker, has also written
<UL>
<LI>a<A href="http://www.av8n.com/vpn/ipsec+routing.htm"> proposal</A>
 for how future versions of FreeS/WAN might interact with routing
 protocols</LI>
<LI>a<A href="http://www.av8n.com/vpn/wishlist.htm"> wishlist</A> of
 possible new features</LI>
</UL>
</LI>
<LI>Bart Trojanowski's web page has a draft design for<A href="http://www.jukie.net/~bart/linux-ipsec/">
 hardware acceleration</A> of FreeS/WAN</LI>
</UL>
<P>Several of these provoked interesting discussions on the mailing
 lists, worth searching for in the<A href="#archive"> archives</A>.</P>
<P>There are also several papers in languages other than English, see
 our<A href="#otherlang"> web links</A>.</P>
<H3><A name="licensing">License and copyright information</A></H3>
<P>All code and documentation written for this project is distributed
 under either the GNU General Public License (<A href="#GPL">GPL</A>) or
 the GNU Library General Public License. For details see the COPYING
 file in the distribution.</P>
<P>Not all code in the distribution is ours, however. See the CREDITS
 file for details. In particular, note that the<A href="#LIBDES"> Libdes</A>
 library and the version of<A href="#MD5"> MD5</A> that we use each have
 their own license.</P>
<H2><A name="sites">Distribution sites</A></H2>
<P>FreeS/WAN is available from a number of sites.</P>
<H3><A NAME="1_5_1">Primary site</A></H3>
<P>Our primary site, is at xs4all (Thanks, folks!) in Holland:</P>
<UL>
<LI><A href="http://www.xs4all.nl/~freeswan">HTTP</A></LI>
<LI><A href="ftp://ftp.xs4all.nl/pub/crypto/freeswan">FTP</A></LI>
</UL>
<H3><A name="mirrors">Mirrors</A></H3>
<P>There are also mirror sites all over the world:</P>
<UL>
<LI><A href="http://www.flora.org/freeswan">Eastern Canada</A> (limited
 resouces)</LI>
<LI><A href="ftp://ludwig.doculink.com/pub/freeswan/">Eastern Canada</A>
 (has older versions too)</LI>
<LI><A href="ftp://ntsc.notBSD.org/pub/crypto/freeswan/">Eastern Canada</A>
 (has older versions too)</LI>
<LI><A href="ftp://ftp.kame.net/pub/freeswan/">Japan</A></LI>
<LI><A href="ftp://ftp.futuredynamics.com/freecrypto/FreeSWAN/">Hong
 Kong</A></LI>
<LI><A href="ftp://ipsec.dk/pub/freeswan/">Denmark</A></LI>
<LI><A href="ftp://ftp.net.lut.ac.uk/freeswan">the UK</A></LI>
<LI><A href="http://storm.alert.sk/comp/mirrors/freeswan/">Slovak
 Republic</A></LI>
<LI><A href="http://the.wiretapped.net/security/vpn-tunnelling/freeswan/">
Australia</A></LI>
<LI><A href="http://freeswan.technolust.cx/">technolust</A></LI>
<LI><A href="http://freeswan.devguide.de/">Germany</A></LI>
<LI>Ivan Moore's<A href="http://snowcrash.tdyc.com/freeswan/"> site</A></LI>
<LI>the<A href="http://www.cryptoarchive.net/"> Crypto Archive</A> on
 the<A href="http://www.securityportal.com/"> Security Portal</A> site</LI>
<LI><A href="http://www.wiretapped.net/">Wiretapped.net</A> in Australia</LI>
</UL>
<P>Thanks to those folks as well.</P>
<H3><A name="munitions">The &quot;munitions&quot; archive of Linux crypto software</A>
</H3>
<P>There is also an archive of Linux crypto software called &quot;munitions&quot;,
 with its own mirrors in a number of countries. It includes FreeS/WAN,
 though not always the latest version. Some of its sites are:</P>
<UL>
<LI><A href="http://munitions.vipul.net/">Germany</A></LI>
<LI><A href="http://munitions.iglu.cjb.net/">Italy</A></LI>
<LI><A href="http://munitions2.xs4all.nl/">Netherlands</A></LI>
</UL>
<P>Any of those will have a list of other &quot;munitions&quot; mirrors. There is
 also a CD available.</P>
<H2><A NAME="1_6">Links to other sections</A></H2>
<P>For more detailed background information, see:</P>
<UL>
<LI><A href="#politics">history and politics</A> of cryptography</LI>
<LI><A href="#ipsec.detail">IPsec protocols</A></LI>
</UL>
<P>To begin working with FreeS/WAN, go to our<A href="quickstart.html#quick.guide">
 quickstart</A> guide.</P>
<HR>
<A NAME="upgrading"></A>
<H1><A NAME="2">Upgrading to FreeS/WAN 2.x</A></H1>
<H2><A NAME="2_1">New! Built in Opportunistic connections</A></H2>
<P>Out of the box, FreeS/WAN 2.x will attempt to encrypt all your IP
 traffic. It will try to establish IPsec connections for:</P>
<UL>
<LI> IP traffic from the Linux box on which you have installed
 FreeS/WAN, and</LI>
<LI> outbound IP traffic routed through that Linux box (eg. from a
 protected subnet).</LI>
</UL>
<P>FreeS/WAN 2.x uses<STRONG> hidden, automatically enabled<VAR>
 ipsec.conf</VAR> connections</STRONG> to do this.</P>
<P>This behaviour is part of our campaign to get Opportunistic
 Encryption (OE) widespread in the Linux world, so that any two Linux
 boxes can encrypt to one another without prearrangement. There's one
 catch, however: you must<A HREF="#quickstart"> set up a few DNS records</A>
 to distribute RSA public keys and (if applicable) IPsec gateway
 information.</P>
<P>If you start FreeS/WAN before you have set up these DNS records, your
 connectivity will be slow, and messages relating to the built in
 connections will clutter your logs. If you are unable to set up DNS for
 OE, you will wish to<A HREF="#disable_policygroups"> disable the hidden
 connections</A>.</P>
<A NAME="upgrading.flagday"></A>
<H3><A NAME="2_1_1">Upgrading Opportunistic Encryption to 2.01 (or
 later)</A></H3>
<P>As of FreeS/WAN 2.01, Opportunistic Encryption (OE) uses DNS TXT
 resource records (RRs) only (rather than TXT with KEY). This change
 causes a &quot;flag day&quot;. Users of FreeS/WAN 2.00 (or earlier) OE who are
 upgrading may need to post additional resource records.</P>
<P>If you are running<A HREF="#initiate-only"> initiate-only OE</A>, you<EM>
 must</EM> put up a TXT record in any forward domain as per our<A HREF="#opp.client">
 quickstart instructions</A>. This replaces your old forward KEY.</P>
<P> If you are running full OE, you require no updates. You already have
 the needed TXT record in the reverse domain. However, to facilitate
 future features, you may also wish to publish that TXT record in a
 forward domain as instructed<A HREF="#opp.incoming"> here</A>.</P>
<P>If you are running OE on a gateway (and encrypting on behalf of
 subnetted boxes) you require no updates. You already have the required
 TXT record in your gateway's reverse map, and the TXT records for any
 subnetted boxes require no updating. However, to facilitate future
 features, you may wish to publish your gateway's TXT record in a
 forward domain as shown<A HREF="#opp.incoming"> here</A>.</P>
<P> During the transition, you may wish to leave any old KEY records up
 for some time. They will provide limited backward compatibility.
<!--
For more
detail on that compatibility, see <A HREF="oe.known-issues">Known Issues with
OE</A>.
-->
</P>
<H2><A NAME="2_2">New! Policy Groups</A></H2>
<P>We want to make it easy for you to declare security policy as it
 applies to IPsec connections.</P>
<P>Policy Groups make it simple to say:</P>
<UL>
<LI>These are the folks I want to talk to in the clear.</LI>
<LI>These spammers' domains -- I don't want to talk to them at all.</LI>
<LI>To talk to the finance department, I must use IPsec.</LI>
<LI>For any other communication, try to encrypt, but it's okay if we
 can't.</LI>
</UL>
<P>FreeS/WAN then implements these policies, creating OE connections if
 and when needed. You can use Policy Groups along with connections you
 explicitly define in ipsec.conf.</P>
<P>For more information, see our<A HREF="policygroups.html"> Policy
 Group HOWTO</A>.</P>
<H2><A NAME="2_3">New! Packetdefault Connection</A></H2>
<P>Free/SWAN 2.x ships with the<STRONG> automatically enabled, hidden
 connection</STRONG><VAR> packetdefault</VAR>. This configures a
 FreeS/WAN box as an OE gateway for any hosts located behind it. As
 mentioned above, you must configure some<A HREF="quickstart.html"> DNS
 records</A> for OE to work.</P>
<P>As the name implies, this connection functions as a default. If you
 have more specific connections, such as policy groups which configure
 your FreeS/WAN box as an OE gateway for a local subnet, these will
 apply before<VAR> packetdefault</VAR>. You can view<VAR> packetdefault</VAR>
's specifics in<A HREF="manpage.d/ipsec.conf.5.html"> man ipsec.conf</A>
.</P>
<H2><A NAME="2_4">FreeS/WAN now disables Reverse Path Filtering</A></H2>
<P>FreeS/WAN often doesn't work with reverse path filtering. At start
 time, FreeS/WAN now turns rp_filter off, and logs a warning.</P>
<P>FreeS/WAN does not turn it back on again. You can do this yourself
 with a command like:</P>
<PRE>   echo 1 &gt; /proc/sys/net/ipv4/conf/eth0/rp_filter</PRE>
<P>For eth0, substitute the interface which FreeS/WAN was affecting.</P>
<A NAME="ipsec.conf_v2"></A>
<H2><A NAME="2_5">Revised<VAR> ipsec.conf</VAR></A></H2>
<H3><A NAME="2_5_1">No promise of compatibility</A></H3>
<P>The FreeS/WAN team promised config-file compatibility throughout the
 1.x series. That means a 1.5 config file can be directly imported into
 a fresh 1.99 install with no problems.</P>
<P>With FreeS/WAN 2.x, we've given ourselves permission to make the
 config file easier to use. The cost: some FreeS/WAN 1.x configurations
 will not work properly. Many of the new features are, however, backward
 compatible.</P>
<H3><A NAME="2_5_2">Most<VAR> ipsec.conf</VAR> files will work fine</A></H3>
<P>... so long as you paste this line,<STRONG> with no preceding
 whitespace</STRONG>, at the top of your config file:</P>
<PRE>    version 2</PRE>
<H3><A NAME="2_5_3">Backward compatibility patch</A></H3>
<P>If the new defaults bite you, use<A HREF="ipsec.conf.2_to_1"> this<VAR>
 ipsec.conf</VAR> fragment</A> to simulate the old default values.</P>
<H3><A NAME="2_5_4">Details</A></H3>
<P> We've obsoleted various directives which almost no one was using:</P>
<PRE>    dump
    plutobackgroundload
    no_eroute_pass
    lifetime
    rekeystart
    rekeytries</PRE>
<P>For most of these, there is some other way to elicit the desired
 behaviour. See<A HREF="http://lists.freeswan.org/pipermail/design/2002-August/003243.html">
 this post</A>.</P>
<P> We've made some settings, which almost everyone was using, defaults.
 For example:</P>
<PRE>    interfaces=%defaultroute
    plutoload=%search
    plutostart=%search
    uniqueids=yes</PRE>
<P>We've also changed some default values to help with OE and Policy
 Groups:</P>
<PRE>    authby=rsasig   ## not secret!!!
    leftrsasigkey=%dnsondemand ## looks up missing keys in DNS when needed.
    rightrsasigkey=%dnsondemand</PRE>
<P> Of course, you can still override any defaults by explictly
 declaring something else in your connection.</P>
<P><A HREF="http://lists.freeswan.org/pipermail/design/2002-August/003243.html">
 A post with a list of many ipsec.conf changes.</A>
<BR><A HREF="manpage.d/ipsec.conf.5.html"> Current ipsec.conf manual.</A>
</P>
<A NAME="upgrading.rpms"></A>
<H3><A NAME="2_5_5">Upgrading from 1.x RPMs to 2.x RPMs</A></H3>
<P>Note: When upgrading from 1-series to 2-series RPMs,<VAR> rpm -U</VAR>
 will not work.</P>
<P>You must instead erase the 1.x RPMs, then install the 2.x set:</P>
<PRE>    rpm -e freeswan</PRE>
<PRE>    rpm -e freeswan-module</PRE>
<P>On erasing, your old<VAR> ipsec.conf</VAR> should be moved to<VAR>
 ipsec.conf.rpmsave</VAR>. Keep this. You will probably want to copy
 your existing connections to the end of your new 2.x file.</P>
<P>Install the RPMs suitable for your kernel version, such as:</P>
<PRE>    rpm -ivh freeswan-module-2.04_2.4.20_20.9-0.i386.rpm</PRE>
<PRE>    rpm -ivh freeswan-userland-2.04_2.4.20_20.9-0.i386.rpm</PRE>
<P>Or, to splice the files:</P>
<PRE>    cat /etc/ipsec.conf /etc/ipsec.conf.rpmsave &gt; /etc/ipsec.conf.tmp
    mv /etc/ipsec.conf.tmp /etc/ipsec.conf</PRE>
<P>Then, remove the redundant<VAR> conn %default</VAR> and<VAR> config
 setup</VAR> sections. Unless you have done any special configuring
 here, you'll likely want to remove the 1.x versions. Remove<VAR> conn
 OEself</VAR>, if present.</P>
<HR>
<H1><A name="quickstart">Quickstart Guide to Opportunistic Encryption</A>
</H1>
<A name="quick_guide"></A>
<H2><A name="opp.setup">Purpose</A></H2>
<P>This page will get you started using Linux FreeS/WAN with
 opportunistic encryption (OE). OE enables you to set up IPsec tunnels
 without co-ordinating with another site administrator, and without hand
 configuring each tunnel. If enough sites support OE, a &quot;FAX effect&quot;
 occurs, and many of us can communicate without eavesdroppers.</P>
<H3><A NAME="3_1_1">OE &quot;flag day&quot;</A></H3>
<P>As of FreeS/WAN 2.01, OE uses DNS TXT resource records (RRs) only
 (rather than TXT with KEY). This change causes a<A href="http://jargon.watson-net.com/jargon.asp?w=flag+day">
 &quot;flag day&quot;</A>. Users of FreeS/WAN 2.00 (or earlier) OE who are
 upgrading may require additional resource records, as detailed in our<A href="#upgrading.flagday">
 upgrading document</A>. OE setup instructions here are for 2.02 or
 later.</P>
<H2><A name="opp.dns">Requirements</A></H2>
<P>To set up opportunistic encryption, you will need:</P>
<UL>
<LI>a Linux box. For OE to the public Internet, this box must NOT be
 behind<A HREF="#NAT.gloss"> Network Address Translation</A> (NAT).</LI>
<LI>to install Linux FreeS/WAN 2.02 or later</LI>
<LI>either control over your reverse DNS (for full opportunism) or the
 ability to write to some forward domain (for initiator-only).<A HREF="http://www.fdns.net">
 This free DNS service</A> explicitly supports forward TXT records for
 FreeS/WAN use.</LI>
<LI>(for full opportunism) a static IP</LI>
</UL>
<P>Note: Currently, only Linux FreeS/WAN supports opportunistic
 encryption.</P>
<H2><A name="easy.install">RPM install</A></H2>
<P>Our instructions are for a recent Red Hat with a 2.4-series stock or
 Red Hat updated kernel. For other ways to install, see our<A href="#install">
 install document</A>.</P>
<H3><A NAME="3_3_1">Download RPMs</A></H3>
<P>If we have prebuilt RPMs for your Red Hat system, this command will
 get them:</P>
<PRE>    ncftpget ftp://ftp.xs4all.nl/pub/crypto/freeswan/binaries/RedHat-RPMs/`uname -r | tr -d 'a-wy-z'`/\*</PRE>
<P>If that fails, you will need to try<A HREF="install.html"> another
 install method</A>. Our kernel modules<B> will only work on the Red Hat
 kernel they were built for</B>, since they are very sensitive to small
 changes in the kernel.</P>
<P>If it succeeds, you will have userland tools, a kernel module, and an
 RPM signing key:</P>
<PRE>    freeswan-module-2.04_2.4.20_20.9-0.i386.rpm
    freeswan-userland-2.04_2.4.20_20.9-0.i386.rpm
    freeswan-rpmsign.asc</PRE>
<H3><A NAME="3_3_2">Check signatures</A></H3>
<P>If you're running RedHat 8.x or later, import the RPM signing key
 into the RPM database:</P>
<PRE>    rpm --import freeswan-rpmsign.asc</PRE>
<P>For RedHat 7.x systems, you'll need to add it to your<A HREF="#PGP">
 PGP</A> keyring:</P>
<PRE>    pgp -ka freeswan-rpmsign.asc</PRE>
<P>Check the digital signatures on both RPMs using:</P>
<PRE>    rpm --checksig freeswan*.rpm </PRE>
<P>You should see that these signatures are good:</P>
<PRE>    freeswan-module-2.04_2.4.20_20.9-0.i386.rpm: pgp md5 OK
    freeswan-userland-2.04_2.4.20_20.9-0.i386.rpm: pgp md5 OK</PRE>
<H3><A NAME="3_3_3">Install the RPMs</A></H3>
<P>Become root:</P>
<PRE>    su</PRE>
<P>Install your RPMs with:</P>
<P></P>
<PRE>    rpm -ivh freeswan*.rpm</PRE>
<P>If you're upgrading from FreeS/WAN 1.x RPMs, and have problems with
 that command, see<A HREF="#upgrading.rpms"> this note</A>.</P>
<P>Then, start FreeS/WAN:</P>
<PRE>    service ipsec start</PRE>
<H3><A name="testinstall">Test</A></H3>
<P>To check that you have a successful install, run:</P>
<PRE>    ipsec verify</PRE>
<P>You should see as part of the<VAR> verify</VAR> output:</P>
<PRE>
    Checking your system to see if IPsec got installed and started correctly
    Version check and ipsec on-path                             [OK]
    Checking for KLIPS support in kernel                        [OK]
    Checking for RSA private key (/etc/ipsec.secrets)           [OK]
    Checking that pluto is running                              [OK]
    ...</PRE>
<P>If any of these first four checks fails, see our<A href="#install.check">
 troubleshooting guide</A>.</P>
<H2><A name="opp.setups.list">Our Opportunistic Setups</A></H2>
<H3><A NAME="3_4_1">Full or partial opportunism?</A></H3>
<P>Determine the best form of opportunism your system can support.</P>
<UL>
<LI>For<A HREF="#opp.incoming"> full opportunism</A>, you'll need a
 static IP and and either control over your reverse DNS or an ISP that
 can add the required TXT record for you.</LI>
<LI>If you have a dynamic IP, and/or write access to forward DNS only,
 you can do<A HREF="#opp.client"> initiate-only opportunism</A></LI>
<LI>To protect traffic bound for real IPs behind your gateway, use<A HREF="#opp.gate">
 this form of full opportunism</A>.</LI>
</UL>
<H2><A name="opp.client">Initiate-only setup</A></H2>
<H3><A NAME="3_5_1">Restrictions</A></H3>
<P>When you set up initiate-only Opportunistic Encryption (iOE):</P>
<UL>
<LI>there will be<STRONG> no incoming connection requests</STRONG>; you
 can initiate all the IPsec connections you need.</LI>
<LI><STRONG>only one machine is visible</STRONG> on your end of the
 connection.</LI>
<LI>iOE also protects traffic on behalf of<A HREF="#NAT.gloss"> NATted</A>
 hosts behind the iOE box.</LI>
</UL>
<P>You cannot network a group of initiator-only machines if none of
 these is capable of responding to OE. If one is capable of responding,
 you may be able to create a hub topology using routing.</P>
<H3><A name="forward.dns">Create and publish a forward DNS record</A></H3>
<H4><A NAME="3_5_2_1">Find a domain you can use</A></H4>
<P>Find a DNS forward domain (e.g. example.com) where you can publish
 your key. You'll need access to the DNS zone files for that domain.
 This is common for a domain you own. Some free DNS providers, such as<A HREF="http://www.fdns.net">
 this one</A>, also provide this service.</P>
<P>Dynamic IP users take note: the domain where you place your key need
 not be associated with the IP address for your system, or even with
 your system's usual hostname.</P>
<H4><A NAME="3_5_2_2">Choose your ID</A></H4>
<P>Choose a name within that domain which you will use to identify your
 machine. It's convenient if this can be the same as your hostname:</P>
<PRE>    [root@xy root]# hostname --fqdn
    xy.example.com</PRE>
<P>This name in FQDN (fully-qualified domain name) format will be your
 ID, for DNS key lookup and IPsec negotiation.</P>
<H4><A NAME="3_5_2_3">Create a forward TXT record</A></H4>
<P>Generate a forward TXT record containing your system's public key
 with a command like:</P>
<PRE>    ipsec showhostkey --txt @xy.example.com</PRE>
<P>using your chosen ID in place of xy.example.com. This command takes
 the contents of /etc/ipsec.secrets and reformats it into something
 usable by ISC's BIND. The result should look like this (with the key
 data trimmed down for clarity):</P>
<PRE>
    ; RSA 2192 bits   xy.example.com   Thu Jan  2 12:41:44 2003
        IN      TXT     &quot;X-IPsec-Server(10)=@xy.example.com&quot; 
    &quot;AQOF8tZ2... ...+buFuFn/&quot;
</PRE>
<H4><A NAME="3_5_2_4">Publish the forward TXT record</A></H4>
<P>Insert the record into DNS, or have a system adminstrator do it for
 you. It may take up to 48 hours for the record to propagate, but it's
 usually much quicker.</P>
<H3><A NAME="3_5_3">Test that your key has been published</A></H3>
<P>Check your DNS work</P>
<PRE>    ipsec verify --host xy.example.com</PRE>
<P>As part of the<VAR> verify</VAR> output, you ought to see something
 like:</P>
<PRE>    ...
    Looking for TXT in forward map: xy.example.com          [OK]
    ...</PRE>
<P>For this type of opportunism, only the forward test is relevant; you
 can ignore the tests designed to find reverse records.</P>
<H3><A NAME="3_5_4">Configure, if necessary</A></H3>
<P> If your ID is the same as your hostname, you're ready to go.
 FreeS/WAN will use its<A HREF="policygroups.html"> built-in connections</A>
 to create your iOE functionality.</P>
<P>If you have chosen a different ID, you must tell FreeS/WAN about it
 via<A HREF="manpage.d/ipsec.conf.5.html"><VAR> ipsec.conf</VAR></A>:</P>
<PRE>    config setup
        myid=@myname.freedns.example.com</PRE>
<P>and restart FreeS/WAN:</P>
<PRE>    service ipsec restart</PRE>
<P>The new ID will be applied to the built-in connections.</P>
<P>Note: you can create more complex iOE configurations as explained in
 our<A HREF="#policygroups"> policy groups document</A>, or disable OE
 using<A HREF="#disable_policygroups"> these instructions</A>.</P>
<H3><A NAME="3_5_5">Test</A></H3>
<P>That's it!<A HREF="#opp.test"> Test your connections</A>.</P>
<A name="opp.incoming"></A>
<H2><A NAME="3_6">Full Opportunism</A></H2>
<P>Full opportunism allows you to initiate and receive opportunistic
 connections on your machine.</P>
<A name="incoming.opp.dns"></A>
<H3><A NAME="3_6_1">Put a TXT record in a Forward Domain</A></H3>
<P>To set up full opportunism, first<A HREF="#forward.dns"> set up a
 forward TXT record</A> as for<A HREF="#opp.client"> initiator-only OE</A>
, using an ID (for example, your hostname) that resolves to your IP. Do
 not configure<VAR> /etc/ipsec.conf</VAR>, but continue with the
 instructions for full opportunism, below.</P>
<P>Note that this forward record is not currently necessary for full OE,
 but will facilitate future features.</P>
<A name="incoming.opp.dns"></A>
<H3><A NAME="3_6_2">Put a TXT record in Reverse DNS</A></H3>
<P>You must be able to publish your DNS RR directly in the reverse
 domain. FreeS/WAN will not follow a PTR which appears in the reverse,
 since a second lookup at connection start time is too costly.</P>
<H4><A NAME="3_6_2_1">Create a Reverse DNS TXT record</A></H4>
<P>This record serves to publicize your FreeS/WAN public key. In
 addition, it lets others know that this machine can receive
 opportunistic connections, and asserts that the machine is authorized
 to encrypt on its own behalf.</P>
<P>Use the command:</P>
<PRE>    ipsec showhostkey --txt 192.0.2.11</PRE>
<P>where you replace 192.0.2.11 with your public IP.</P>
<P>The record (with key shortened) looks like:</P>
<PRE>    ; RSA 2048 bits  xy.example.com   Sat Apr 15 13:53:22 2000
    IN TXT  &quot;X-IPsec-Server(10)=192.0.2.11&quot; &quot; AQOF8tZ2...+buFuFn/&quot;</PRE>
<H4><A NAME="3_6_2_2">Publish your TXT record</A></H4>
<P>Send these records to your ISP, to be published in your IP's reverse
 map. It may take up to 48 hours for these to propagate, but usually
 takes much less time.</P>
<H3><A NAME="3_6_3">Test your DNS record</A></H3>
<P>Check your DNS work with</P>
<PRE>    ipsec verify --host xy.example.com</PRE>
<P>As part of the<VAR> verify</VAR> output, you ought to see something
 like:</P>
<PRE>    ...
    Looking for TXT in reverse map: 11.2.0.192.in-addr.arpa [OK]
    ...</PRE>
<P>which indicates that you've passed the reverse-map test.</P>
<H3><A NAME="3_6_4">No Configuration Needed</A></H3>
<P>FreeS/WAN 2.x ships with full OE enabled, so you don't need to
 configure anything. To enable OE out of the box, FreeS/WAN 2.x uses the
 policy group<VAR> private-or-clear</VAR>, which creates IPsec
 connections if possible (using OE if needed), and allows traffic in the
 clear otherwise. You can create more complex OE configurations as
 described in our<A HREF="#policygroups"> policy groups document</A>, or
 disable OE using<A HREF="#disable_policygroups"> these instructions</A>
.</P>
<P>If you've previously configured for initiator-only opportunism,
 remove<VAR> myid=</VAR> from<VAR> config setup</VAR>, so that peer
 FreeS/WANs will look up your key by IP. Restart FreeS/WAN so that your
 change will take effect, with</P>
<PRE>    service ipsec restart</PRE>
<H3><A NAME="3_6_5">Consider Firewalling</A></H3>
<P>If you are running a default install of RedHat 8.x, take note: you
 will need to alter your iptables rule setup to allow IPSec traffic
 through your firewall. See<A HREF="#simple.rules"> our firewall
 document</A> for sample<VAR> iptables</VAR> rules.</P>
<H3><A NAME="3_6_6">Test</A></H3>
<P>That's it. Now,<A HREF="#opp.test"> test your connection</A>.</P>
<H3><A NAME="3_6_7">Test</A></H3>
<P>Instructions are in the next section.</P>
<H2><A NAME="opp.test">Testing opportunistic connections</A></H2>
<P>Be sure IPsec is running. You can see whether it is with:</P>
<PRE>    ipsec setup status</PRE>
<P>If need be, you can restart it with:</P>
<PRE>    service ipsec restart</PRE>
<P>Load a FreeS/WAN test website from the host on which you're running
 FreeS/WAN. Note: the feds may be watching these sites. Type one of:</P>
<P></P>
<PRE>   links oetest.freeswan.org</PRE>
<PRE>   links oetest.freeswan.nl</PRE>

<!--<PRE>   links oetest.freeswan.ca</PRE>-->
<P>A positive result looks like this:</P>
<PRE>
   You  seem  to  be  connecting  from:  192.0.2.11 which DNS says is:
   gateway.example.com
     _________________________________________________________________

   Status E-route
   OE    enabled    16    192.139.46.73/32    -&gt;    192.0.2.11/32   =&gt;
   tun0x2097@192.0.2.11
   OE    enabled    176    192.139.46.77/32    -&gt;   192.0.2.11/32   =&gt;
   tun0x208a@192.0.2.11
</PRE>
<P>If you see this, congratulations! Your OE host or gateway will now
 encrypt its own traffic whenever it can. For more OE tests, please see
 our<A HREF="#test.oe"> testing document</A>. If you have difficulty,
 see our<A HREF="#oe.trouble"> OE troubleshooting tips</A>.</P>
<H2><A NAME="3_8">Now what?</A></H2>
<P>Please see our<A HREF="policygroups.html"> policy groups document</A>
 for more ways to set up Opportunistic Encryption.</P>
<P>You may also wish to make some<A HREF="config.html"> pre-configured
 connections</A>.</P>
<H2><A NAME="3_9">Notes</A></H2>
<UL>
<LI>We assume some facts about your system in order to make
 Opportunistic Encryption easier to configure. For example, we assume
 that you wish to have FreeS/WAN secure your default interface.</LI>
<LI>You may change this, and other settings, by altering the<VAR> config
 setup</VAR> section in<VAR> /etc/ipsec.conf</VAR>.</LI>
<LI>Note that the built-in connections used to build policy groups do
 not inherit from<VAR> conn default</VAR>.</LI>

<!--
<LI>If you do not define your local identity
(eg. <VAR>leftid</VAR>), this will be the IP address of your default
FreeS/WAN interface.  
-->
<LI> If you fail to define your local identity and do not fill in your
 reverse DNS entry, you will not be able to use OE.</LI>
</UL>
<A NAME="oe.trouble"></A>
<H2><A NAME="3_10">Troubleshooting OE</A></H2>
<P>See the OE troubleshooting hints in our<A HREF="#oe.trouble">
 troubleshooting guide</A>.</P>
<A NAME="oe.known-issues"></A>
<H2><A NAME="3_11">Known Issues</A></H2>
<P>Please see<A HREF="opportunism.known-issues"> this list</A> of known
 issues with Opportunistic Encryption.</P>
<HR>
<H1><A NAME="4">How to Configure Linux FreeS/WAN with Policy Groups</A></H1>
<A NAME="policygroups"></A>
<H2><A NAME="4_1">What are Policy Groups?</A></H2>
<P><STRONG>Policy Groups</STRONG> are an elegant general mechanism to
 configure FreeS/WAN. They are useful for many FreeS/WAN users.</P>
<P>In previous FreeS/WAN versions, you needed to configure each IPsec
 connection explicitly, on both local and remote hosts. This could
 become complex.</P>
<P>By contrast, Policy Groups allow you to set local IPsec policy for
 lists of remote hosts and networks, simply by listing the hosts and
 networks which you wish to have special treatment in one of several
 Policy Group files. FreeS/WAN then internally creates the connections
 needed to implement each policy.</P>
<P>In the next section we describe our five Base Policy Groups, which
 you can use to configure IPsec in many useful ways. Later, we will show
 you how to create an IPsec VPN using one line of configuration for each
 remote host or network.</P>
<A NAME="builtin_policygroups"></A>
<H3><A NAME="4_1_1">Built-In Security Options</A></H3>
<P>FreeS/WAN offers these Base Policy Groups:</P>
<DL>
<DT>private</DT>
<DD> FreeS/WAN only communicates privately with the listed<A HREF="#CIDR">
 CIDR</A> blocks. If needed, FreeS/WAN attempts to create a connection
 opportunistically. If this fails, FreeS/WAN blocks communication.
 Inbound blocking is assumed to be done by the firewall. FreeS/WAN
 offers firewall hooks but no modern firewall rules to help with inbound
 blocking.</DD>
<DT>private-or-clear</DT>
<DD> FreeS/WAN prefers private communication with the listed CIDR
 blocks. If needed, FreeS/WAN attempts to create a connection
 opportunistically. If this fails, FreeS/WAN allows traffic in the
 clear.</DD>
<DT>clear-or-private</DT>
<DD> FreeS/WAN communicates cleartext with the listed CIDR blocks, but
 also accepts inbound OE connection requests from them. Also known as<A HREF="#passive.OE">
 passive OE (pOE)</A>, this policy may be used to create an<A HREF="#responder">
 opportunistic responder</A>.</DD>
<DT>clear</DT>
<DD> FreeS/WAN only communicates cleartext with the listed CIDR blocks.</DD>
<DT>block</DT>
<DD>FreeS/WAN blocks traffic to and from and the listed CIDR blocks.
 Inbound blocking is assumed to be done by the firewall. FreeS/WAN
 offers firewall hooks but no modern firewall rules to help with inbound
 blocking.
<!-- also called "blockdrop".-->
</DD>
</DL>
<A NAME="policy.group.notes"></A>
<P>Notes:</P>
<UL>
<LI>Base Policy Groups apply to communication with this host only.</LI>
<LI>The most specific rule (whether policy or pre-configured connection)
 applies. This has several practical applications:
<UL>
<LI>If CIDR blocks overlap, FreeS/WAN chooses the most specific
 applicable block.</LI>
<LI>This decision also takes into account any pre-configured connections
 you may have.</LI>
<LI>If the most specific connection is a pre-configured connection, the
 following procedure applies. If that connection is up, it will be used.
 If it is routed, it will be brought up. If it is added, no action will
 be taken.</LI>
</UL>
</LI>
<LI>Base Policy Groups are created using built-in connections. Details
 in<A HREF="manpage.d/ipsec.conf.5.html"> man ipsec.conf</A>.</LI>
<LI>All Policy Groups are bidirectional.<A HREF="src/policy-groups-table.html">
 This chart</A> shows some technical details. FreeS/WAN does not support
 one-way encryption, since it can give users a false sense of security.</LI>
</UL>
<H2><A NAME="4_2">Using Policy Groups</A></H2>
<P>The Base Policy Groups which build IPsec connections rely on
 Opportunistic Encryption. To use the following examples, you must first
 become OE-capable, as described in our<A HREF="#quickstart"> quickstart
 guide</A>.<A NAME="example1"></A></P>
<H3><A NAME="4_2_1">Example 1: Using a Base Policy Group</A></H3>
<P>Simply place CIDR blocks (<A HREF="#dnswarning">names</A>, IPs or IP
 ranges) in /etc/ipsec.d/policies/<VAR>[groupname]</VAR>, and reread the
 policy group files.</P>
<P>For example, the<VAR> private-or-clear</VAR> policy tells FreeS/WAN
 to prefer encrypted communication to the listed CIDR blocks. Failing
 that, it allows talk in the clear.</P>
<P>To make this your default policy, place<A HREF="#fullnet"> fullnet</A>
 in the<VAR> private-or-clear</VAR> policy group file:</P>
<PRE>    [root@xy root]# cat /etc/ipsec.d/policies/private-or-clear
    # This file defines the set of CIDRs (network/mask-length) to which
    # communication should be private, if possible, but in the clear otherwise.
    ....
    0.0.0.0/0</PRE>
<P>and reload your policies with</P>
<PRE>    ipsec auto --rereadgroups</PRE>
<P>Use<A HREF="#opp.test"> this test</A> to verify opportunistic
 connections.</P>
<A NAME="example2"></A>
<H3><A NAME="4_2_2">Example 2: Defining IPsec Security Policy with
 Groups</A></H3>
<P>Defining IPsec security policy with Base Policy Groups is like
 creating a shopping list: just put CIDR blocks in the appropriate group
 files. For example:</P>
<PRE>    [root@xy root]# cd /etc/ipsec.d/policies
    [root@xy policies]# cat private
        192.0.2.96/27              # The finance department
        192.0.2.192/29             # HR
	192.0.2.12                 # HR gateway
        irc.private.example.com    # Private IRC server
  
    [root@xy policies]# cat private-or-clear
        0.0.0.0/0                  # My default policy: try to encrypt.

    [root@xy policies]# cat clear
        192.0.2.18/32              # My POP3 server
        192.0.2.19/32              # My Web proxy

    [root@xy policies]# cat block
        spamsource.example.com</PRE>
<P>To make these settings take effect, type:</P>
<PRE>    ipsec auto --rereadgroups</PRE>
<P>Notes:</P>
<UL>
<LI>For opportunistic connection attempts to succeed, all participating
 FreeS/WAN hosts and gateways must be configured for OE.</LI>
<LI>Examples 3 through 5 show how to implement a detailed<VAR> private</VAR>
 policy.</LI>
<LI><A NAME="dnswarning"></A><FONT COLOR="RED"> Warning:</FONT> Using
 DNS names in policy files and ipsec.conf can be tricky. If the name
 does not resolve, the policy will not be implemented for that name. It
 is therefore safer either to use IPs, or to put any critical names in
 /etc/hosts. We plan to implement periodic DNS retry to help with this.
<BR> Names are resolved at FreeS/WAN startup, or when the policies are
 reloaded. Unfortunately, name lookup can hold up the startup process.
 If you have fast DNS servers, the problem may be less severe.</LI>
</UL>
<A HREF="example3"></A>
<H3><A NAME="4_2_3">Example 3: Creating a Simple IPsec VPN with the<VAR>
 private</VAR> Group</A></H3>
<P>You can create an IPsec VPN between several hosts, with only one line
 of configuration per host, using the<VAR> private</VAR> policy group.</P>
<P>First, use our<A HREF="quickstart.html"> quickstart guide</A> to set
 up each participating host with a FreeS/WAN install and OE.</P>
<P>In one host's<VAR> /etc/ipsec.d/policies/private</VAR>, list the
 peers to which you wish to protect traffic. For example:</P>
<PRE>    [root@xy root]# cd /etc/ipsec.d/policies
    [root@xy policies]# cat private
        192.0.2.9              # several hosts at example.com
        192.0.2.11             
        192.0.2.12                 
        irc.private.example.com 
</PRE>
<P>Copy the<VAR> private</VAR> file to each host. Remove the local host,
 and add the initial host.</P>
<PRE>    scp2 /etc/ipsec.d/policies/private root@192.0.2.12:/etc/ipsec.d/policies/private</PRE>
<P>On each host, reread the policy groups with</P>
<PRE>    ipsec auto --rereadgroups</PRE>
<P>That's it! You're configured.</P>
<P>Test by pinging between two hosts. After a second or two, traffic
 should flow, and</P>
<PRE>    ipsec eroute</PRE>
<P>should yield something like</P>
<PRE>    192.0.2.11/32   -&gt; 192.0.2.8/32  =&gt; tun0x149f@192.0.2.8</PRE>
<P>where your host IPs are substituted for 192.0.2.11 and 192.0.2.8.</P>
<P>If traffic does not flow, there may be an error in your OE setup.
 Revisit our<A HREF="quickstart.html"> quickstart guide</A>.</P>
<P>Our next two examples show you how to add subnets to this IPsec VPN.</P>
<A NAME="example4"></A>
<H3><A NAME="4_2_4">Example 4: New Policy Groups to Protect a Subnet</A></H3>
<P>To protect traffic to a subnet behind your FreeS/WAN gateway, you'll
 need additional DNS records, and new policy groups. To set up the DNS,
 see our<A HREF="#opp.gate"> quickstart guide</A>. To create five new
 policy groups for your subnet, copy these connections to<VAR>
 /etc/ipsec.conf</VAR>. Substitute your subnet's IPs for 192.0.2.128/29.</P>
<PRE>
conn private-net
    also=private  # inherits settings (eg. auto=start) from built in conn
    leftsubnet=192.0.2.128/29  # your subnet's IPs here

conn private-or-clear-net
    also=private-or-clear
    leftsubnet=192.0.2.128/29

conn clear-or-private-net
    also=clear-or-private
    leftsubnet=192.0.2.128/29

conn clear-net
    also=clear
    leftsubnet=192.0.2.128/29

conn block-net
    also=block
    leftsubnet=192.0.2.128/29
</PRE>
<P>Copy the gateway's files to serve as the initial policy group files
 for the new groups:</P>
<PRE>
    cp -p /etc/ipsec.d/policies/private /etc/ipsec.d/policies/private-net
    cp -p /etc/ipsec.d/policies/private-or-clear /etc/ipsec.d/policies/private-or-clear-net
    cp -p /etc/ipsec.d/policies/clear-or-private /etc/ipsec.d/policies/clear-or-private-net
    cp -p /etc/ipsec.d/policies/clear /etc/ipsec.d/policies/clear-net
    cp -p /etc/ipsec.d/policies/block /etc/ipsec.d/policies/block
</PRE>
<P><STRONG>Tip: Since a missing policy group file is equivalent to a
 file with no entries, you need only create files for the connections
 you'll use.</STRONG></P>
<P>To test one of your new groups, place the fullnet 0.0.0.0/0 in<VAR>
 private-or-clear-net</VAR>. Perform the subnet test in<A HREF="#opp.test">
 our quickstart guide</A>. You should see a connection, and</P>
<PRE>    ipsec eroute</PRE>
<P>should include an entry which mentions the subnet node's IP and the
 OE test site IP, like this:</P>
<PRE>    192.0.2.131/32   -&gt; 192.139.46.77/32  =&gt; tun0x149f@192.0.2.11</PRE>
<A HREF="example5"></A>
<H3><A NAME="4_2_5">Example 5: Adding a Subnet to the VPN</A></H3>
<P>Suppose you wish to secure traffic to a subnet 192.0.2.192/29 behind
 a FreeS/WAN box 192.0.2.12.</P>
<P>First, add DNS entries to configure 192.0.2.12 as an opportunistic
 gateway for that subnet. Instructions are in our<A HREF="#opp.gate">
 quickstart guide</A>. Next, create a<VAR> private-net</VAR> group on
 192.0.2.12 as described in<A HREF="#example4"> Example 4</A>.</P>
<P>On each other host, add the subnet 192.0.2.192/29 to<VAR> private</VAR>
, yielding for example</P>
<PRE>    [root@xy root]# cd /etc/ipsec.d/policies
    [root@xy policies]# cat private
        192.0.2.9              # several hosts at example.com
        192.0.2.11
        192.0.2.12             # HR department gateway
        192.0.2.192/29         # HR subnet
        irc.private.example.com
</PRE>
<P>and reread policy groups with</P>
<PRE>    ipsec auto --rereadgroups</PRE>
<P>That's all the configuration you need.</P>
<P>Test your VPN by pinging from a machine on 192.0.2.192/29 to any
 other host:</P>
<PRE>    [root@192.0.2.194]# ping 192.0.2.11</PRE>
<P>After a second or two, traffic should flow, and</P>
<PRE>    ipsec eroute</PRE>
<P>should yield something like</P>
<PRE>    192.0.2.11/32   -&gt; 192.0.2.194/32  =&gt; tun0x149f@192.0.2.12
</PRE>
<P>Key:</P>
<TABLE>
<TR><TD>1.</TD><TD>192.0.2.11/32</TD><TD>Local start point of the
 protected traffic.</TD></TR>
<TR><TD>2.</TD><TD>192.0.2.194/32</TD><TD>Remote end point of the
 protected traffic.</TD></TR>
<TR><TD>3.</TD><TD>192.0.2.12</TD><TD>Remote FreeS/WAN node (gateway or
 host). May be the same as (2).</TD></TR>
<TR><TD>4.</TD><TD>[not shown]</TD><TD>Local FreeS/WAN node (gateway or
 host), where you've produced the output. May be the same as (1).</TD></TR>
</TABLE>
<P>For additional assurance, you can verify with a packet sniffer that
 the traffic is being encrypted.</P>
<P>Note</P>
<UL>
<LI>Because strangers may also connect via OE, this type of VPN may
 require a stricter firewalling policy than a conventional VPN.</LI>
</UL>
<H2><A NAME="4_3">Appendix</A></H2>
<A NAME="hiddenconn"></A>
<H3><A NAME="4_3_1">Our Hidden Connections</A></H3>
<P>Our Base Policy Groups are created using hidden connections. These
 are spelled out in<A HREF="manpage.d/ipsec.conf.5.html"> man ipsec.conf</A>
 and defined in<VAR> /usr/local/lib/ipsec/_confread</VAR>.</P>
<A NAME="custom_policygroups"></A>
<H3><A NAME="4_3_2">Custom Policy Groups</A></H3>
<P>A policy group is built using a special connection description in<VAR>
 ipsec.conf</VAR>, which:</P>
<UL>
<LI>is<STRONG> generic</STRONG>. It uses<VAR>
 right=[%group|%opportunisticgroup]</VAR> rather than specific IPs. The
 connection is cloned for every name or IP range listed in its Policy
 Group file.</LI>
<LI>often has a<STRONG> failure rule</STRONG>. This rule, written<VAR>
 failureshunt=[passthrough|drop|reject|none]</VAR>, tells FreeS/WAN what
 to do with packets for these CIDRs if it fails to establish the
 connection. Default is<VAR> none</VAR>.</LI>
</UL>
<P>To create a new group:</P>
<OL>
<LI>Create its connection definition in<VAR> ipsec.conf</VAR>.</LI>
<LI>Create a Policy Group file in<VAR> /etc/ipsec.d/policies</VAR> with
 the same name as your connection.</LI>
<LI>Put a CIDR block in that file.</LI>
<LI>Reread groups with<VAR> ipsec auto --rereadgroups</VAR>.</LI>
<LI>Test:<VAR> ping</VAR> to activate any OE connection, and view
 results with<VAR> ipsec eroute</VAR>.</LI>
</OL>
<A NAME="disable_oe"></A><A NAME="disable_policygroups"></A>
<H3><A NAME="4_3_3">Disabling Opportunistic Encryption</A></H3>
<P>To disable OE (eg. policy groups and packetdefault), cut and paste
 the following lines to<VAR> /etc/ipsec.conf</VAR>:</P>
<PRE>conn block
    auto=ignore

conn private
    auto=ignore

conn private-or-clear
    auto=ignore

conn clear-or-private
    auto=ignore

conn clear
    auto=ignore

conn packetdefault
    auto=ignore</PRE>
<P>Restart FreeS/WAN so that the changes take effect:</P>
<PRE>    ipsec setup restart</PRE>
<HR>
<H1><A NAME="5">FreeS/WAN FAQ</A></H1>
<P>This is a collection of questions and answers, mostly taken from the
 FreeS/WAN<A href="mail.html"> mailing list</A>. See the project<A href="http://www.freeswan.org/">
 web site</A> for more information. All the FreeS/WAN documentation is
 online there.</P>
<P>Contributions to the FAQ are welcome. Please send them to the project<A
href="mail.html"> mailing list</A>.</P>
<HR>
<H2><A name="questions">Index of FAQ questions</A></H2>
<UL>
<LI><A href="#whatzit">What is FreeS/WAN?</A></LI>
<LI><A href="#problems">How do I report a problem or seek help?</A></LI>
<LI><A href="#generic">Can I get ...</A>
<UL>
<LI><A href="#lemme_out">... an off-the-shelf system that includes
 FreeS/WAN?</A></LI>
<LI><A href="#contractor">... contractors or staff who know FreeS/WAN?</A>
</LI>
<LI><A href="#commercial">... commercial support?</A></LI>
</UL>
</LI>
<LI><A href="#release">Release questions</A>
<UL>
<LI><A href="#rel.current">What is the current release?</A></LI>
<LI><A href="#relwhen">When is the next release?</A></LI>
<LI><A href="#rel.bugs">Are there known bugs in the current release?</A></LI>
</UL>
</LI>
<LI><A href="mod_cons">Modifications and contributions</A>
<UL>
<LI><A href="#modify.faq">Can I modify FreeS/WAN to ...?</A></LI>
<LI><A href="#contrib.faq">Can I contribute to the project?</A></LI>
<LI><A href="#ddoc.faq">Is there detailed design documentation?</A></LI>
</UL>
</LI>
<LI><A href="#interact">Will FreeS/WAN work in my environment?</A>
<UL>
<LI><A href="#interop.faq">Can FreeS/WAN talk to ... ?</A></LI>
<LI><A href="#old_to_new">Can different FreeS/WAN versions talk to each
 other?</A></LI>
<LI><A href="#faq.bandwidth">Is there a limit on throughput?</A></LI>
<LI><A href="#faq.number">Is there a limit on number of connections?</A></LI>
<LI><A href="#faq.speed">Is a ... fast enough to handle FreeS/WAN with
 my loads?</A></LI>
</UL>
</LI>
<LI><A href="#work_on">Will FreeS/WAN work on ...</A>
<UL>
<LI><A href="#versions">... my version of Linux?</A></LI>
<LI><A href="#nonIntel.faq">... non-Intel CPUs?</A></LI>
<LI><A href="#multi.faq">... multiprocessors?</A></LI>
<LI><A href="#k.old">... an older kernel?</A></LI>
<LI><A href="#k.versions">... the latest kernel version?</A></LI>
<LI><A href="#interface.faq">... unusual network hardware?</A></LI>
<LI><A href="#vlan">... a VLAN (802.1q) network?</A></LI>
</UL>
</LI>
<LI><A href="#features.faq">Does FreeS/WAN support ...</A>
<UL>
<LI><A href="#VPN.faq">... site-to-site VPN applications</A></LI>
<LI><A href="#warrior.faq">... remote users connecting to a LAN</A></LI>
<LI><A href="#road.shared.possible">... remote users using shared secret
 authentication?</A></LI>
<LI><A href="#wireless.faq">... wireless networks</A></LI>
<LI><A href="#PKIcert">... X.509 or other PKI certificates?</A></LI>
<LI><A href="#Radius">... user authentication (Radius, SecureID, Smart
 Card ...)?</A></LI>
<LI><A href="#NATtraversal">... NAT traversal</A></LI>
<LI><A href="#virtID">... assigning a &quot;virtual identity&quot; to a remote
 system?</A></LI>
<LI><A href="#noDES.faq">... single DES encryption?</A></LI>
<LI><A href="#AES.faq">... AES encryption?</A></LI>
<LI><A href="#other.cipher">... other encryption algorithms?</A></LI>
</UL>
</LI>
<LI><A href="#canI">Can I ...</A>
<UL>
<LI><A href="#policy.preconfig">...use policy groups along with
 explicitly configured connections?</A></LI>
<LI><A href="#policy.off">...turn off policy groups?</A></LI>

<!--
      <li><a href="#policy.otherinterface">...use policy groups
      on an interface other than <VAR>%defaultroute</VAR>?</a></li>
-->
<LI><A href="#reload">... reload connection info without restarting?</A></LI>
<LI><A href="#masq.faq">... use several masqueraded subnets?</A></LI>
<LI><A href="#dup_route">... use subnets masqueraded to the same
 addresses?</A></LI>
<LI><A href="#road.masq">... assign a road warrior an address on my net
 (a virtual identity)?</A></LI>
<LI><A href="#road.many">... support many road warriors with one
 gateway?</A></LI>
<LI><A href="#road.PSK">... have many road warriors using shared secret
 authentication?</A></LI>
<LI><A href="#QoS">... use Quality of Service routing with FreeS/WAN?</A>
</LI>
<LI><A href="#deadtunnel">... recognise dead tunnels and shut them down?</A>
</LI>
<LI><A href="#demanddial">... build IPsec tunnels over a demand-dialed
 link?</A></LI>
<LI><A href="#GRE">... build GRE, L2TP or PPTP tunnels over IPsec?</A></LI>
<LI><A href="#NetBIOS">... use Network Neighborhood (Samba, NetBIOS)
 over IPsec?</A></LI>
</UL>
</LI>
<LI><A href="#setup.faq">Life's little mysteries</A>
<UL>
<LI><A href="#cantping">I cannot ping ....</A></LI>
<LI><A href="#forever">It takes forever to ...</A></LI>
<LI><A href="#route">I send packets to the tunnel with route(8) but they
 vanish</A></LI>
<LI><A href="#down_route">When a tunnel goes down, packets vanish</A></LI>
<LI><A href="#firewall_ate">The firewall ate my packets!</A></LI>
<LI><A href="#dropconn">Dropped connections</A></LI>
<LI><A href="#defaultroutegone">Disappearing %defaultroute</A></LI>
<LI><A href="#tcpdump.faq">TCPdump on the gateway shows strange things</A>
</LI>
<LI><A href="#no_trace">Traceroute does not show anything between the
 gateways</A></LI>
</UL>
</LI>
<LI><A href="#man4debug">Testing in stages (or .... works but ...
 doesn't)</A>
<UL>
<LI><A href="#nomanual">Manually keyed connections don't work</A></LI>
<LI><A href="#spi_error">One manual connection works, but second one
 fails</A></LI>
<LI><A href="#man_no_auto">Manual connections work, but automatic keying
 doesn't</A></LI>
<LI><A href="#nocomp">IPsec works, but connections using compression
 fail</A></LI>
<LI><A href="#pmtu.broken">Small packets work, but large transfers fail</A>
</LI>
<LI><A href="#subsub">Subnet-to-subnet works, but tests from the
 gateways don't</A></LI>
</UL>
</LI>
<LI><A href="#compile.faq">Compilation problems</A>
<UL>
<LI><A href="#gmp.h_missing">gmp.h: No such file or directory</A></LI>
<LI><A href="#noVM">... virtual memory exhausted</A></LI>
</UL>
</LI>
<LI><A href="#error">Interpreting error messages</A>
<UL>
<LI><A href="#route-client">route-client (or host) exited with status 7</A>
</LI>
<LI><A href="#unreachable">SIOCADDRT:Network is unreachable</A></LI>
<LI><A href="#modprobe">ipsec_setup: modprobe: Can't locate moduleipsec</A>
</LI>
<LI><A href="#noKLIPS">ipsec_setup: Fatal error, kernel appears to lack
 KLIPS</A></LI>
<LI><A href="#noDNS">ipsec_setup: ... failure to fetch key for ... from
 DNS</A></LI>
<LI><A href="#dup_address">ipsec_setup: ... interfaces ... and ... share
 address ...</A></LI>
<LI><A href="#kflags">ipsec_setup: Cannot adjust kernel flags</A></LI>
<LI><A href="#message_num">Message numbers (MI3, QR1, et cetera) in
 Pluto messages</A></LI>
<LI><A href="#conn_name">Connection names in Pluto error messages</A></LI>
<LI><A href="#cantorient">Pluto: ... can't orient connection</A></LI>
<LI><A href="#no.interface">... we have no ipsecN interface for either
 end of this connection</A></LI>
<LI><A href="#noconn">Pluto: ... no connection is known</A></LI>
<LI><A href="#nosuit">Pluto: ... no suitable connection ...</A></LI>
<LI><A href="#noconn.auth">Pluto: ... no connection has been authorized</A>
</LI>
<LI><A href="#noDESsupport">Pluto: ... OAKLEY_DES_CBC is not supported.</A>
</LI>
<LI><A href="#notransform">Pluto: ... no acceptable transform</A></LI>
<LI><A href="#rsasigkey">rsasigkey dumps core</A></LI>
<LI><A href="#sig4">!Pluto failure!: ... exited with ... signal 4</A></LI>
<LI><A href="#econnrefused">ECONNREFUSED error message</A></LI>
<LI><A href="#no_eroute">klips_debug: ... no eroute!</A></LI>
<LI><A href="#SAused">... trouble writing to /dev/ipsec ... SA already
 in use</A></LI>
<LI><A href="#ignore">... ignoring ... payload</A></LI>
<LI><A href="#unknown_rightcert">unknown parameter name &quot;rightcert&quot;</A></LI>
</UL>
</LI>
<LI><A href="#spam">Why don't you restrict the mailing lists to reduce
 spam?</A></LI>
</UL>
<HR>
<H2><A name="whatzit">What is FreeS/WAN?</A></H2>
<P>FreeS/WAN is a Linux implementation of the<A href="#IPSEC"> IPsec</A>
 protocols, providing security services at the IP (Internet Protocol)
 level of the network.</P>
<P>For more detail, see our<A href="intro.html"> introduction</A>
 document or the FreeS/WAN project<A href="http://www.freeswan.org/">
 web site</A>.</P>
<P>To start setting it up, go to our<A href="quickstart.html">
 quickstart guide</A>.</P>
<P>Our<A href="web.html"> web links</A> document has information on<A href="#implement">
 IPsec for other systems</A>.</P>
<H2><A name="problems">How do I report a problem or seek help?</A></H2>
<DL>
<DT>Read our<A href="trouble.html"> troubleshooting</A> document.</DT>
<DD>
<P>It may guide you to a solution. If not, see its<A href="#prob.report">
 problem reporting</A> section.</P>
<P>Basically, what it says is<STRONG> give us the output from<VAR> ipsec
 barf</VAR> from both gateways</STRONG>. Without full information, we
 cannot diagnose a problem. However,<VAR> ipsec barf</VAR> produces a
 lot of output. If at all possible,<STRONG> please make barfs accessible
 via the web or FTP</STRONG> rather than sending enormous mail messages.</P>
</DD>
<DT><STRONG>Use the<A href="mail.html"> users mailing list</A> for
 problem reports</STRONG>, rather than mailing developers directly.</DT>
<DD>
<UL>
<LI>This gives you access to more expertise, including users who may
 have encountered and solved the same problems.</LI>
<LI>It is more likely to get a quick response. Developers may get behind
 on email, or even ignore it entirely for a while, but a list message
 (given a reasonable Subject: line) is certain to be read by a fair
 number of people within hours.</LI>
<LI>It may also be important because of<A href="#exlaw"> cryptography
 export laws</A>. A US citizen who provides technical assistance to
 foreign cryptographic work might be charged under the arms export
 regulations. Such a charge would be easier to defend if the discussion
 took place on a public mailing list than if it were done in private
 mail.</LI>
</UL>
</DD>
<DT>Try irc.freenode.net#freeswan.</DT>
<DD>
<P>FreeS/WAN developers, volunteers and users can often be found there.
 Be patient and be prepared to provide lots of information to support
 your question.</P>
<P>If your question was really interesting, and you found an answer,
 please share that with the class by posting to the<A href="mail.html">
 users mailing list</A>. That way others with the same problem can find
 your answer in the archives.</P>
</DD>
<DT>Premium support is also available.</DT>
<DD>
<P>See the next several questions.</P>
</DD>
</DL>
<H2><A name="generic">Can I get ...</A></H2>
<H3><A name="lemme_out">Can I get an off-the-shelf system that includes
 FreeS/WAN?</A></H3>
<P>There are a number of Linux distributions or firewall products which
 include FreeS/WAN. See this<A href="#products"> list</A>. Using one of
 these, chosen to match your requirements and budget, may save you
 considerable time and effort.</P>
<P>If you don't know your requirements, start by reading Schneier's<A href="#secrets">
 Secrets and Lies</A>. That gives the best overview of security issues I
 have seen. Then consider hiring a consultant (see next question) to
 help define your requirements.</P>
<H3><A name="consultant">Can I hire consultants or staff who know
 FreeS/WAN?</A></H3>
<P>If you want the help of a contractor, or to hire staff with FreeS/WAN
 expertise, you could:</P>
<UL>
<LI>check availability in your area through your local Linux User Group
 (<A href="http://lugww.counter.li.org/">LUG Index</A>)</LI>
<LI>try asking on our<A href="mail.html"> mailing list</A></LI>
</UL>
<P>For companies offerring support, see the next question.</P>
<H3><A name="commercial">Can I get commercial support?</A></H3>
<P>Many of the distributions or firewall products which include
 FreeS/WAN (see this<A href="#products"> list</A>) come with commercial
 support or have it available as an option.</P>
<P>Various companies specialize in commercial support of open source
 software. Our project leader was a founder of the first such company,
 Cygnus Support. It has since been bought by<A href="http://www.redhat.com">
 Redhat</A>. Another such firm is<A href="http://www.linuxcare.com">
 Linuxcare</A>.</P>
<H2><A name="release">Release questions</A></H2>
<H3><A name="rel.current">What is the current release?</A></H3>
<P>The current release is the highest-numbered tarball on our<A href="ftp://ftp.xs4all.nl/pub/crypto/freeswan">
 distribution site</A>. Almost always, any of<A href="#mirrors"> the
 mirrors</A> will have the same file, though perhaps not for a day or so
 after a release.</P>
<P>Unfortunately, the web site is not always updated as quickly as it
 should be.</P>
<H3><A name="relwhen">When is the next release?</A></H3>
<P>We try to do a release approximately every six to eight weeks.</P>
<P>If pre-release tests fail and the fix appears complex, or more
 generally if the code does not appear stable when a release is
 scheduled, we will just skip that release.</P>
<P>For serious bugs, we may bring out an extra bug-fix release. These
 get numbers in the normal release series. For example, there was a bug
 found in FreeS/WAN 1.6, so we did another release less than two weeks
 later. The bug-fix release was called 1.7.</P>
<H3><A name="rel.bugs">Are there known bugs in the current release?</A></H3>
<P>Any problems we are aware of at the time of a release are documented
 in the<A href="../BUGS"> BUGS</A> file for that release. You should
 also look at the<A href="../CHANGES"> CHANGES</A> file.</P>
<P>Bugs discovered after a release are discussed on the<A href="mail.html">
 mailing lists</A>. The easiest way to check for any problems in the
 current code would be to peruse the<A href="http://lists.freeswan.org/pipermail/briefs">
 List In Brief</A>.</P>
<H2><A name="mod_cons">Modifications and contributions</A></H2>
<H3><A name="modify.faq">Can I modify FreeS/WAN to ...?</A></H3>
<P>You are free to modify FreeS/WAN in any way. See the discussion of<A href="#licensing">
 licensing</A> in our introduction document.</P>
<P>Before investing much energy in any such project, we suggest that you</P>
<UL>
<LI>check the list of<A href="#patch"> existing patches</A></LI>
<LI>post something about your project to the<A href="mail.html"> design
 mailing list</A></LI>
</UL>
<P>This may prevent duplicated effort, or lead to interesting
 collaborations.</P>
<H3><A name="contrib.faq">Can I contribute to the project?</A></H3>
 In general, we welcome contributions from the community. Various
 contributed patches, either to fix bugs or to add features, have been
 incorporated into our distribution. Other patches, not yet included in
 the distribution, are listed in our<A href="#patch"> web links</A>
 section.
<P>Users have also contributed heavily to documentation, both by
 creating their own<A href="#howto"> HowTos</A> and by posting things on
 the<A href="mail.html"> mailing lists</A> which I have quoted in these
 HTML docs.</P>
<P>There are, however, some caveats.</P>
<P>FreeS/WAN is being implemented in Canada, by Canadians, largely to
 ensure that is it is entirely free of export restrictions. See this<A href="#status">
 discussion</A>. We<STRONG> cannot accept code contributions from US
 residents or citizens</STRONG>, not even one-line bugs fixes. The
 reasons for this were recently discussed extensively on the mailing
 list, in a thread starting<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/01/msg00111.html">
 here</A>.</P>
<P>Not all contributions are of interest to us. The project has a set of
 fairly ambitious and quite specific goals, described in our<A href="#goals">
 introduction</A>. Contributions that lead toward these goals are likely
 to be welcomed enthusiastically. Other contributions may be seen as
 lower priority, or even as a distraction.</P>
<P>Discussion of possible contributions takes place on the<A href="mail.html">
 design mailing list</A>.</P>
<H3><A name="ddoc.faq">Is there detailed design documentation?</A></H3>
 There are:
<UL>
<LI><A href="rfc.html">RFCs</A> specifying the protocols we implement</LI>
<LI><A href="manpages.html">man pages</A> for our utilities, library
 functions and file formats</LI>
<LI>comments in the source code</LI>
<LI><A href="index.html">HTML documentation</A> written primarily for
 users</LI>
<LI>archived discussions from the<A href="mail.html"> mailing lists</A></LI>
<LI>other papers mentioned in our<A href="#applied"> introduction</A></LI>
</UL>
<P>The only formal design documents are a few papers in the last
 category above. All the other categories, however, have things to say
 about design as well.</P>
<H2><A name="interact">Will FreeS/WAN work in my environment?</A></H2>
<H3><A name="interop.faq">Can FreeS/WAN talk to ...?</A></H3>
<P>The IPsec protocols are designed to support interoperation. In
 theory, any two IPsec implementations should be able to talk to each
 other. In practice, it is considerably more complex. We have a whole<A href="interop.html">
 interoperation document</A> devoted to this problem.</P>
<P>An important part of that document is links to the many<A href="interop.html#otherpub">
 user-written HowTos</A> on interoperation between FreeS/WAN and various
 other implementations. Often the users know more than the developers
 about these issues (and almost always more than me :-), so these
 documents may be your best resource.</P>
<H3><A name="old_to_new">Can different FreeS/WAN versions talk to each
 other?</A></H3>
<P>Linux FreeS/WAN can interoperate with many IPsec implementations,
 including earlier versions of Linux FreeS/WAN itself.</P>
<P>In a few cases, there are some complications. See our<A href="interop.html#oldswan">
 interoperation</A> document for details.</P>
<H3><A name="faq.bandwidth">Is there a limit on throughput?</A></H3>
<P>There is no hard limit, but see below.</P>
<H3><A name="faq.number">Is there a limit on number of tunnels?</A></H3>
<P>There is no hard limit, but see next question.</P>
<H3><A name="faq.speed">Is a ... fast enough to handle FreeS/WAN with my
 loads?</A></H3>
<P>A quick summary:</P>
<DL>
<DT>Even a limited machine can be useful</DT>
<DD>A 486 can handle a T1, ADSL or cable link, though the machine may be
 breathing hard.</DD>
<DT>A mid-range PC (say 800 MHz with good network cards) can do a lot of
 IPsec</DT>
<DD>With up to roughly 50 tunnels and aggregate bandwidth of 20 Megabits
 per second, it willl have cycles left over for other tasks.</DD>
<DT>There are limits</DT>
<DD>Even a high end CPU will not come close to handling a fully loaded
 100 Mbit/second Ethernet link.
<P>Beyond about 50 tunnels it needs careful management.</P>
</DD>
</DL>
<P>See our<A href="performance.html"> FreeS/WAN performance</A> document
 for details.</P>
<H2><A name="work_on">Will FreeS/WAN work on ... ?</A></H2>
<H3><A name="versions">Will FreeS/WAN run on my version of Linux?</A></H3>
<P>We build and test on Redhat distributions, but FreeS/WAN runs just
 fine on several other distributions, sometimes with minor fiddles to
 adapt to the local environment. Details are in our<A href="#otherdist">
 compatibility</A> document. Also, some distributions or products come
 with<A href="#products"> FreeS/WAN included</A>.</P>
<H3><A name="nonIntel.faq">Will FreeS/WAN run on non-Intel CPUs?</A></H3>
<P>FreeS/WAN is<STRONG> intended to run on all CPUs Linux supports</STRONG>
. We know of it being used in production on x86, ARM, Alpha and MIPS. It
 has also had successful tests on PPC and SPARC, though we don't know of
 actual use there. Details are in our<A href="#CPUs"> compatibility</A>
 document.</P>
<H3><A name="multi.faq">Will FreeS/WAN run on multiprocessors?</A></H3>
<P>FreeS/WAN is designed to work on any SMP architecture Linux supports,
 and has been tested successfully on at least dual processor Intel
 architecture machines. Details are in our<A href="#multiprocessor">
 compatibility</A> document.</P>
<H3><A name="k.old">Will FreeS/WAN work on an older kernel?</A></H3>
<P>It might, but we strongly recommend using a recent 2.2 or 2.4 series
 kernel. Sometimes the newer versions include security fixes which can
 be quite important on a gateway.</P>
<P>Also, we use recent kernels for development and testing, so those are
 better tested and, if you do encounter a problem, more easily
 supported. If something breaks applying recent FreeS/WAN patches to an
 older kernel, then &quot;update your kernel&quot; is almost certain to be the
 first thing we suggest. It may be the only suggestion we have.</P>
<P>The precise kernel versions supported by a particular FreeS/WAN
 release are given in the<A href="XX"> README</A> file of that release.</P>
<P>See the following question for more on kernels.</P>
<H3><A name="k.versions">Will FreeS/WAN run on the latest kernel
 version?</A></H3>
<P>Sometimes yes, but quite often, no.</P>
<P>Kernel versions supported are given in the<A href="../README"> README</A>
 file of each FreeS/WAN release. Typically, they are whatever production
 kernels were current at the time of our release (or shortly before; we
 might release for kernel<VAR> n</VAR> just as Linus releases<VAR> n+1</VAR>
). Often FreeS/WAN will work on slightly later kernels as well, but of
 course this cannot be guaranteed.</P>
<P>For example, FreeS/WAN 1.91 was released for kernels 2.2.19 or 2.4.5,
 the current kernels at the time. It also worked on 2.4.6, 2.4.7 and
 2.4.8, but 2.4.9 had changes that caused compilation errors if it was
 patched with FreeS/WAN 1.91.</P>
<P>When such changes appear, we put a fix in the FreeS/WAN snapshots,
 and distribute it with our next release. However, this is not a high
 priority for us, and it may take anything from a few days to several
 weeks for such a problem to find its way to the top of our kernel
 programmer's To-Do list. In the meanwhile, you have two choices:</P>
<UL>
<LI>either stick with a slightly older kernel, even if it is not the
 latest and greatest. This is recommended for production systems; new
 versions may have new bugs.</LI>
<LI>or fix the problem yourself and send us a patch, via the<A href="mail.html">
 Users mailing list</A>.</LI>
</UL>
<P>We don't even try to keep up with kernel changes outside the main 2.2
 and 2.4 branches, such as the 2.4.x-ac patched versions from Alan Cox
 or the 2.5 series of development kernels. We'd rather work on
 developing the FreeS/WAN code than on chasing these moving targets. We
 are, however, happy to get patches for problems discovered there.</P>
<P>See also the<A href="install.html#choosek"> Choosing a kernel</A>
 section of our installation document.</P>
<H3><A name="interface.faq">Will FreeS/WAN work on unusual network
 hardware?</A></H3>
<P>IPsec is designed to work over any network that IP works over, and
 FreeS/WAN is intended to work over any network interface hardware that
 Linux supports.</P>
<P>If you have working IP on some unusual interface -- perhaps Arcnet,
 Token Ring, ATM or Gigabit Ethernet -- then IPsec should &quot;just work&quot;.</P>
<P>That said, practice is sometimes less tractable than theory. Our
 testing is done almost entirely on:</P>
<UL>
<LI>10 or 100 Mbit Ethernet</LI>
<LI>ADSL or cable connections, with and without PPPoE</LI>
<LI>IEEE 802.11 wireless LANs (see<A href="#wireless.faq"> below</A>)</LI>
</UL>
<P>If you have some other interface, especially an uncommon one, it is
 entirely possible you will get bitten either by a FreeS/WAN bug which
 our testing did not turn up, or by a bug in the driver that shows up
 only with our loads.</P>
<P>If IP works on your interface and FreeS/WAN doesn't, seek help on the<A
href="mail.html"> mailing lists</A>.</P>
<P>Another FAQ section describes<A href="#pmtu.broken"> MTU problems</A>
. These are a possibility for some interfaces.</P>
<H3><A name="vlan">Will FreeS/WAN work on a VLAN (802.1q) network?</A></H3>
<P> Yes, FreeSwan works fine, though some network drivers have problems
 with jumbo sized ethernet frames. If you used interfaces=%defaultroute
 you do not need to change anything, but if you specified an interface
 (eg eth0) then remember you must change that to reflect the VLAN
 interface (eg eth0.2 for VLAN ID 2).</P>
<P> The &quot;eepro100&quot; module is known to be broken, use the e100 driver for
 those cards instead (included in 2.4 as 'alternative driver' for the
 Intel EtherExpressPro/100.</P>
<P> You do not need to change any MTU setting (those are workarounds
 that are only needed for buggy drivers)</P>
<P><EM>This FAQ contributed by Paul Wouters.</EM></P>
<H2><A name="features.faq">Does FreeS/WAN support ...</A></H2>
<P>For a discussion of which parts of the IPsec specifications FreeS/WAN
 does and does not implement, see our<A href="#spec"> compatibility</A>
 document.</P>
<P>For information on some often-requested features, see below.</P>
<H3><A name="VPN.faq"></A>Does FreeS/WAN support site-to-site VPN (<A HREF="#VPN">
Virtual Private Network</A>) applications?</H3>
<P>Absolutely. See this FreeS/WAN-FreeS/WAN<A HREF="config.html">
 configuration example</A>. If only one site is using FreeS/WAN, there
 may be a relevant HOWTO on our<A HREF="interop.html"> interop page</A>.</P>
<H3><A name="warrior.faq">Does FreeS/WAN support remote users connecting
 to a LAN?</A></H3>
<P>Yes. We call the remote users &quot;Road Warriors&quot;. Check out our
 FreeS/WAN-FreeS/WAN<A HREF="#config.rw"> Road Warrior Configuration
 Example</A>.</P>
<P>If your Road Warrior is a Windows or Mac PC, you may need to install
 an IPsec implementation on that machine. Our<A HREF="interop.html">
 interop</A> page lists many available brands, and features links to
 several HOWTOs.</P>
<H3><A name="road.shared.possible">Does FreeS/WAN support remote users
 using shared secret authentication?</A></H3>
<P><STRONG>Yes, but</STRONG> there are severe restrictions, so<STRONG>
 we strongly recommend using</STRONG><A href="#RSA"><STRONG> RSA</STRONG>
</A><STRONG> keys for</STRONG><A href="#authentication"><STRONG>
 authentication</STRONG></A><STRONG> instead</STRONG>.</P>
<P>See this<A href="#road.PSK"> FAQ question</A>.</P>
<H3><A name="wireless.faq">Does FreeS/WAN support wireless networks?</A></H3>
<P>Yes, it is a common practice to use IPsec over wireless networks
 because their built-in encryption,<A href="#WEP"> WEP</A>, is insecure.</P>
<P>There is some<A href="#wireless.config"> discussion</A> in our
 advanced configuration document. See also the<A HREF="http://www.wavesec.org">
 WaveSEC site</A>.</P>
<H3><A name="PKIcert">Does FreeS/WAN support X.509 or other PKI
 certificates?</A></H3>
<P>Vanilla FreeS/WAN does not support X.509, but Andreas Steffen and
 others have provided a popular, well-supported X.509 patch.</P>
<UL>
<LI><A HREF="http://www.strongsec.com/freeswan">patch</A></LI>
<LI><A HREF="http://www.freeswan.ca">Super FreeS/WAN</A> incorporates
 this and other user-contributed patches.</LI>
<LI> Kai Martius'<A HREF="http://www.strongsec.com/freeswan/install.htm">
 X.509 Installation and Configuration Guide</A></LI>
</UL>
<P> Linux FreeS/WAN features<A HREF="quickstart.html"> Opportunistic
 Encryption</A>, an alternative Public Key Infrastructure based on
 Secure DNS.</P>
<H3><A name="Radius">Does FreeS/WAN support user authentication (Radius,
 SecureID, Smart Card...)?</A></H3>
<P>Andreas Steffen's<A HREF="http://www.strongsec.com/freeswan"> X.509
 patch</A> (v. 1.42+) supports Smart Cards. The patch does not ship with
 vanilla FreeS/WAN, but will be incorporated into<A HREF="http://www.freeswan.ca/">
 Super FreeS/WAN 2.01+</A>. The patch implements the PCKS#15
 Cryptographic Token Information Format Standard, using the OpenSC
 smartcard library functions.</P>
<P>Older news:</P>
<P>A user-supported patch to FreeS/WAN 1.3, for smart card style
 authentication, is available on<A HREF="http://alcatraz.webcriminals.com/~bastiaan/ipsec">
 Bastiaan's site</A>. It supports skeyid and ibutton. This patch is not
 part of Super FreeS/WAN.</P>
<P>For a while progress on this front was impeded by a lack of standard.
 The IETF<A href="http://www.ietf.org/html.charters/ipsra-charter.html">
 working group</A> has now nearly completed its recommended solution to
 the problem; meanwhile several vendors have implemented various things.</P>

<!--
<p>The <a href="web.html#patch">patches</a> section of our web links document
has links to some user work on this.</p>
-->
<P>Of course, there are various ways to avoid any requirement for user
 authentication in IPsec. Consider the situation where road warriors
 build IPsec tunnels to your office net and you are considering
 requiring user authentication during tunnel negotiation. Alternatives
 include:</P>
<UL>
<LI>If you can trust the road warrior machines, then set them up so that
 only authorised users can create tunnels. If your road warriors use
 laptops, consider the possibility of theft.</LI>
<LI>If the tunnel only provides access to particular servers and you can
 trust those servers, then set the servers up to require user
 authentication.</LI>
</UL>
<P>If either of those is trustworthy, it is not clear that you need user
 authentication in IPsec.</P>
<H3><A name="NATtraversal">Does FreeS/WAN support NAT traversal?</A></H3>
<P>Vanilla FreeS/WAN does not, but thanks to Mathieu Lafon and Arkoon
 Network Security, there's a patch to support this.</P>
<UL>
<LI><A HREF="http://open-source.arkoon.net">patch and documentation</A></LI>
<LI><A HREF="http://www.freeswan.ca">Super FreeS/WAN</A> incorporates
 this and other user-contributed patches.</LI>
</UL>
<P>The NAT traversal patch has some issues with PSKs, so you may wish to
 authenticate with RSA keys, or X.509 (requires a patch which is also
 included in Super FreeS/WAN). Doing the latter also has advantages when
 dealing with large numbers of clients who may be behind NAT; instead of
 having to make an individual Roadwarrior connection for each virtual
 IP, you can use the &quot;rightsubnetwithin&quot; parameter to specify a range.
 See<A HREF="http://www.strongsec.com/freeswan/install.htm#section_4.4">
 these<VAR> rightsubnetwithin</VAR> instructions</A>.</P>
<H3><A name="virtID">Does FreeS/WAN support assigning a &quot;virtual
 identity&quot; to a remote system?</A></H3>
<P>Some IPsec implementations allow you to make the source address on
 packets sent by a Road Warrior machine be something other than the
 address of its interface to the Internet. This is sometimes described
 as assigning a virtual identity to that machine.</P>
<P>FreeS/WAN does not directly support this, but it can be done. See
 this<A href="#road.masq"> FAQ question</A>.</P>
<H3><A name="noDES.faq">Does FreeS/WAN support single DES encryption?</A>
</H3>
<P><STRONG>No</STRONG>, single DES is not used either at the<A href="#IKE">
 IKE</A> level for negotiating connections or at the<A href="#IPSEC">
 IPsec</A> level for actually building them.</P>
<P>Single DES is<A href="#desnotsecure"> insecure</A>. As we see it, it
 is more important to deliver real security than to comply with a
 standard which has been subverted into allowing use of inadequate
 methods. See this<A href="#weak"> discussion</A>.</P>
<P>If you want to interoperate with an IPsec implementation which offers
 only DES, see our<A href="interop.html#noDES"> interoperation</A>
 document.</P>
<H3><A name="AES.faq">Does FreeS/WAN support AES encryption?</A></H3>
<P><A href="#AES">AES</A> is a new US government<A href="#block"> block
 cipher</A> standard to replace the obsolete<A href="#DES"> DES</A>.</P>
<P>At time of writing (March 2002), the FreeS/WAN distribution does not
 yet support AES but user-written<A href="#patch"> patches</A> are
 available to add it. Our kernel programmer is working on integrating
 those patches into the distribution, and there is active discussion of
 this on the design mailimg list.</P>
<H3><A name="other.cipher">Does FreeS/WAN support other encryption
 algorithms?</A></H3>
<P>Currently<A href="#3DES"> triple DES</A> is the only cipher
 supported. AES will almost certainly be added (see previous question),
 and it is likely that in the process we will also add the other two AES
 finalists with open licensing, Twofish and Serpent.</P>
<P>We are extremely reluctant to add other ciphers. This would make both
 use and maintenance of FreeS/WAN more complex without providing any
 clear benefit. Complexity is emphatically not desirable in a security
 product.</P>
<P>Various users have written patches to add other ciphers. We provide<A href="#patch">
 links</A> to these.</P>
<H2><A name="canI">Can I ...</A></H2>
<H3><A name="policy.preconfig">Can I use policy groups along with
 explicitly configured connections?</A></H3>
<P>Yes, you can, so long as you pay attention to the selection rule,
 which can be summarized &quot;the most specific connection wins&quot;. We
 describe the rule in our<A HREF="#policy.group.notes"> policy groups</A>
 document, and provide a more technical explanation in<A HREF="manpage.d/ipsec.conf.5.html">
 man ipsec.conf</A>.</P>
<P>A good guideline: If you have a regular connection defined in<VAR>
 ipsec.conf</VAR>, ensure that a subset of that connection is not listed
 in a less restrictive policy group. Otherwise, FreeS/WAN will use the
 subset, with its more specific source/destination pair.</P>
<P>Here's an example. Suppose you are the system administrator at
 192.0.2.2. You have this connection in ipsec.conf:<VAR> ipsec.conf</VAR>
:</P>
<PRE>conn net-to-net
    left=192.0.2.2           # you are here
    right=192.0.2.8
    rightsubnet=192.0.2.96/27
    ....
</PRE>
<P>If you then place a host or net within<VAR> rightsubnet</VAR>, (let's
 say 192.0.2.98) in<VAR> private-or-clear</VAR>, you may find that
 192.0.2.2 at times communicates in the clear with 192.0.2.98. That's
 consistent with the rule, but may be contrary to your expectations.</P>
<P>On the other hand, it's safe to put a larger subnet in a less
 restrictive policy group file. If<VAR> private-or-clear</VAR> contains
 192.0.2.0/24, then the more specific<VAR> net-to-net</VAR> connection
 is used for any communication to 192.0.2.96/27. The more general policy
 applies only to communication with hosts or subnets in 192.0.2.0/24
 without a more specific policy or connection.</P>
<H3><A name="policy.off">Can I turn off policy groups?</A></H3>
<P>Yes. Use<A HREF="#disable_policygroups"> these instructions</A>.</P>

<!--
<h3><a name="policy.otherinterface">Can I use policy groups
 on an interface other than <VAR>%defaultroute</VAR>?</a></h3>

<p>??<p>
-->
<H3><A name="reload">Can I reload connection info without restarting?</A>
</H3>
<P>Yes, you can do this. Here are the details, in a mailing list message
 from Pluto programmer Hugh Redelmeier:</P>
<PRE>| How can I reload config's without restarting all of pluto and klips?  I am using
| FreeSWAN -&gt; PGPNet in a medium sized production environment, and would like to be
| able to add new connections ( i am using include config/* ) without dropping current
| SA's.
| 
| Can this be done?
| 
| If not, are there plans to add this kind of feature?

        ipsec auto --add whatever
This will look in the usual place (/etc/ipsec.conf) for a conn named
whatever and add it.

If you added new secrets, you need to do
        ipsec auto --rereadsecrets
before Pluto needs to know those secrets.

| I have looked (perhaps not thoroughly enough tho) to see how to do this:

There may be more bits to look for, depending on what you are trying
to do.</PRE>
<P>Another useful command here is<VAR> ipsec auto --replace &lt;conn_name&gt;</VAR>
 which re-reads data for a named connection.</P>
<H3><A name="masq.faq">Can I use several masqueraded subnets?</A></H3>
<P>Yes. This is done all the time. See the discussion in our<A href="config.html#route_or_not">
 setup</A> document. The only restriction is that the subnets on the two
 ends must not overlap. See the next question.</P>
<P>Here is a mailing list message on the topic. The user incorrectly
 thinks you need a 2.4 kernel for this -- actually various people have
 been doing it on 2.0 and 2.2 for quite some time -- but he has it right
 for 2.4.</P>
<PRE>Subject: Double NAT and freeswan working :)
   Date: Sun, 11 Mar 2001
   From: Paul Wouters &lt;paul@xtdnet.nl&gt;

Just to share my pleasure, and make an entry for people who are searching
the net on how to do this. Here's the very simple solution to have a double
NAT'ed network working with freeswan. (Not sure if this is old news, but I'm
not on the list (too much spam) and I didn't read this in any HOWTO/FAQ/doc
on the freeswan site yet (Sandy, put it in! :)

10.0.0.0/24 --- 10.0.0.1 a.b.c.d  ---- a.b.c.e {internet} ----+
                                                              |
10.0.1.0/24 --- 10.0.1.1 f.g.h.i  ---- f.g.h.j {internet} ----+

the goal is to have the first network do a VPN to the second one, yet also
have NAT in place for connections not destinated for the other side of the
NAT. Here the two Linux security gateways have one real IP number (cable
modem, dialup, whatever.

The problem with NAT is you don't want packets from 10.*.*.* to 10.*.*.*
to be NAT'ed. While with Linux 2.2, you can't, with Linux 2.4 you can.

(This has been tested and works for 2.4.2 with Freeswan snapshot2001mar8b)

relevant parts of /etc/ipsec.conf:

        left=f.g.h.i
        leftsubnet=10.0.1.0/24
        leftnexthop=f.g.h.j
        leftfirewall=yes
        leftid=@firewall.netone.nl
        leftrsasigkey=0x0........
        right=a.b.c.d
        rightsubnet=10.0.0.0/24
        rightnexthop=a.b.c.e
        rightfirewall=yes
        rightid=@firewall.nettwo.nl
        rightrsasigkey=0x0......
        # To authorize this connection, but not actually start it, at startup,
        # uncomment this.
        auto=add

and now the real trick. Setup the NAT correctly on both sites:

iptables -t nat -F
iptables -t nat -A POSTROUTING -o eth0 -d \! 10.0.0.0/8 -j MASQUERADE

This tells the NAT code to only do NAT for packets with destination other then
10.* networks. note the backslash to mask the exclamation mark to protect it
against the shell.

Happy painting :)

Paul</PRE>
<H3><A name="dup_route">Can I use subnets masqueraded to the same
 addresses?</A></H3>
<P><STRONG>No.</STRONG> The notion that IP addresses are unique is one
 of the fundamental principles of the IP protocol. Messing with it is
 exceedingly perilous.</P>
<P>Fairly often a situation comes up where a company has several
 branches, all using the same<A href="#non-routable"> non-routable
 addresses</A>, perhaps 192.168.0.0/24. This works fine as long as those
 nets are kept distinct. The<A href="#masq"> IP masquerading</A> on
 their firewalls ensures that packets reaching the Internet carry the
 firewall address, not the private address.</P>
<P>This can break down when IPsec enters the picture. FreeS/WAN builds a
 tunnel that pokes through both masquerades and delivers packets from<VAR>
 leftsubnet</VAR> to<VAR> rightsubnet</VAR> and vice versa. For this to
 work, the two subnets<EM> must</EM> be distinct.</P>
<P>There are several solutions to this problem.</P>
<P>Usually, you<STRONG> re-number the subnets</STRONG>. Perhaps the
 Vancouver office becomes 192.168.101.0/24, Calgary 192.168.102.0/24 and
 so on. FreeS/WAN can happily handle this. With, for example<VAR>
 leftsubnet=192.168.101.0/24</VAR> and<VAR> rightsubnet=192.168.102.0/24</VAR>
 in a connection description, any machine in Calgary can talk to any
 machine in Vancouver. If you want to be more restrictive and use
 something like<VAR> leftsubnet=192.168.101.128/25</VAR> and<VAR>
 rightsubnet=192.168.102.240/28</VAR> so only certain machines on each
 end have access to the tunnel, that's fine too.</P>
<P>You could also<STRONG> split the subnet</STRONG> into smaller ones,
 for example using<VAR> 192.168.1.0/25</VAR> in Vancouver and<VAR>
 rightsubnet=192.168.0.128/25</VAR> in Calgary.</P>
<P>Alternately, you can just<STRONG> give up routing</STRONG> directly
 to machines on the subnets. Omit the<VAR> leftsubnet</VAR> and<VAR>
 rightsubnet</VAR> parameters from your connection descriptions. Your
 IPsec tunnels will then run between the public interfaces of the two
 firewalls. Packets will be masqueraded both before they are put into
 tunnels and after they emerge. Your Vancouver client machines will see
 only one Calgary machine, the firewall.</P>
<H3><A name="road.masq">Can I assign a road warrior an address on my net
 (a virtual identity)?</A></H3>
<P>Often it would be convenient to be able to give a Road Warrior an IP
 address which appears to be on the local network. Some IPsec
 implementations have support for this, sometimes calling the feature
 &quot;virtual identity&quot;.</P>
<P>Currently (Sept 2002) FreeS/WAN does not support this, and we have no
 definite plans to add it. The difficulty is that is not yet a standard
 mechanism for it. There is an Internet Draft for a method of doing it
 using<A href="#DHCP"> DHCP</A> which looks promising. FreeS/WAN may
 support that in a future release.</P>
<P>In the meanwhile, you can do it yourself using the Linux iproute2(8)
 facilities. Details are in<A href="http://www.av8n.com/vpn/iproute2.htm">
 this paper</A>.</P>
<P>Another method has also been discussed on the mailing list.:</P>
<UL>
<LI>You can use a variant of the<A href="#extruded.config"> extruded
 subnet</A> procedure.</LI>
<LI>You have to avoid having the road warrior's assigned address within
 the range you actually use at home base. See previous question.</LI>
<LI>On the other hand, you want the roadwarrior's address to be within
 the range that<EM> seems</EM> to be on your network.</LI>
</UL>
<P>For example, you might have:</P>
<DL>
<DT>leftsubnet=a.b.c.0/25</DT>
<DD>head office network</DD>
<DT>rightsubnet=a.b.c.129/32</DT>
<DD>extruded to a road warrior. Note that this is not in a.b.c.0/25</DD>
<DT>a.b.c.0/24</DT>
<DD>whole network, including both the above</DD>
</DL>
<P>You then set up routing so that the office machines use the IPsec
 gateway as their route to a.b.c.128/25. The leftsubnet parameter tells
 the road warriors to use tunnels to reach a.b.c.0/25, so you should
 have two-way communication. Depending or your network and applications,
 there may be some additional work to do on DNS or Windows configuration</P>
<H3><A name="road.many">Can I support many road warriors with one
 gateway?</A></H3>
<P>Yes. This is easily done, using</P>
<DL>
<DT>either RSA authentication</DT>
<DD>standard in the FreeS/WAN distribution</DD>
<DT>or X.509 certificates</DT>
<DD>requires<A href="#PKIcert"> Super FreeS/WAN or a patch</A>.</DD>
</DL>
<P>In either case, each Road Warrior must have a different key or
 certificate.</P>
<P>It is also possible using pre-shared key authentication, though we
 don't recommend this; see the<A href="#road.PSK"> next question</A> for
 details.</P>
<P>If you expect to have more than a few dozen Road Warriors connecting
 simultaneously, you may need a fairly powerful gateway machine. See our
 document on<A href="performance.html"> FreeS/WAN performance</A>.</P>
<H3><A name="road.PSK">Can I have many road warriors using shared secret
 authentication?</A></H3>
<P><STRONG>Yes, but avoid it if possible</STRONG>.</P>
<P>You can have multiple Road Warriors using shared secret
 authentication<STRONG> only if they all use the same secret</STRONG>.
 You must also set:</P>
<P></P>
<PRE>   uniqueids=no   </PRE>
<P>in the connection definition.</P>
<P>Why it's less secure:</P>
<UL>
<LI>If you have many users, it becomes almost certain the secret will
 leak</LI>
<LI>The secret becomes quite valuable to an attacker</LI>
<LI>All users authenticate the same way, so the gateway cannot tell them
 apart for logging or access control purposes</LI>
<LI>Changing the secret is difficult. You have to securely notify all
 users.</LI>
<LI>If you find out the secret has been compromised, you can change it,
 but then what? None of your users can connect without the new secret.
 How will you notify them all, quickly and securely, without using the
 VPN?</LI>
</UL>
<P>This is a designed-in limitation of the<A href="#IKE"> IKE</A> key
 negotiation protocol, not a problem with our implementation.</P>
<P><STRONG>We very strongly recommend that you avoid using shared secret
 authentication for multiple Road Warriors.</STRONG> Use RSA
 authentication instead.</P>
<P>The longer story: When using shared secrets, the protocol requires
 that the responding gateway be able to determine which secret to use at
 a time when all it knows about the initiator is an IP address. This
 works fine if you know the initiator's address in advance and can use
 it to look up the appropiriate secret. However, it fails for Road
 Warriors since the gateway cannot know their IP addresses in advance.</P>
<P>With RSA signatures (or certificates) the protocol is slightly
 different. The initiator provides an identifier early in the exchange
 and the responder can use that identifier to look up the correct key or
 certificate. See<A href="#road.many"> above</A>.</P>
<H3><A name="QoS">Can I use Quality of Service routing with FreeS/WAN?</A>
</H3>
<P>From project technical lead Henry Spencer:</P>
<PRE>&gt; Do QoS add to FreeS/WAN?
&gt; For example integrating DiffServ and FreeS/WAN?

With a current version of FreeS/WAN, you will have to add hidetos=no to
the config-setup section of your configuration file.  By default, the TOS
field of tunnel packets is zeroed; with hidetos=no, it is copied from the
packet inside.  (This is a modest security hole, which is why it is no
longer the default.)

DiffServ does not interact well with tunneling in general.  Ways of
improving this are being studied.</PRE>
<P>Copying the<A href="#TOS"> TOS</A> (type of service) information from
 the encapsulated packet to the outer header reveals the TOS information
 to an eavesdropper. This does not tell him much, but it might be of use
 in<A href="#traffic"> traffic analysis</A>. Since we do not have to
 give it to him, our default is not to.</P>
<P>Even with the TOS hidden, you can still:</P>
<UL>
<LI>apply QOS rules to the tunneled (ESP) packets; for example, by
 giving ESP packets a certain priority.</LI>
<LI>apply QOS rules to the packets as they enter or exit the tunnel via
 an IPsec virtual interface (eg.<VAR> ipsec0</VAR>).</LI>
</UL>
<P>See<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf(5)</A> for more
 on the<VAR> hidetos=</VAR> parameter.</P>
<H3><A name="deadtunnel">Can I recognise dead tunnels and shut them
 down?</A></H3>
<P>There is no general mechanism to do this is in the IPsec protocols.</P>
<P>From time to time, there is discussion on the IETF Working Group<A href="#ietf">
 mailing list</A> of adding a &quot;keep-alive&quot; mechanism (which some say
 should be called &quot;make-dead&quot;), but it is a fairly complex problem and
 no consensus has been reached on whether or how it should be done.</P>
<P>The protocol does have optional<A href="#ignore"> delete-SA</A>
 messages which one side can send when it closes a connection in hopes
 this will cause the other side to do the same. FreeS/WAN does not
 currently support these. In any case, they would not solve the problem
 since:</P>
<UL>
<LI>a gateway that crashes or hangs would not send the messages</LI>
<LI>the sender is not required to send them</LI>
<LI>they are not authenticated, so any receiver that trusts them leaves
 itself open to a<A href="#DOS"> denial of service</A> attack</LI>
<LI>the receiver is not required to do anything about them</LI>
<LI>the receiver cannot acknowledge them; the protocol provides no
 mechanism for that</LI>
<LI>since they are not acknowledged, the sender cannot rely on them</LI>
</UL>
<P>However, connections do have limited lifetimes and you can control
 how many attempts your gateway makes to rekey before giving up. For
 example, you can set:</P>
<PRE>conn default
        keyingtries=3
        keylife=30m</PRE>
<P>With these settings old connections will be cleaned up. Within 30
 minutes of the other end dying, rekeying will be attempted. If it
 succeeds, the new connection replaces the old one. If it fails, no new
 connection is created. Either way, the old connection is taken down
 when its lifetime expires.</P>
<P>Here is a mailing list message on the topic from FreeS/WAN tech
 support person Claudia Schmeing:</P>
<PRE>You ask how to determine whether a tunnel is redundant:

&gt; Can anybody explain the best way to determine this. Esp when a RW has
&gt; disconnected? I thought 'ipsec auto --status' might be one way.

If a tunnel goes down from one end, Linux FreeS/WAN on the
other end has no way of knowing this until it attempts to rekey.
Once it tries to rekey and fails, it will 'know' that the tunnel is 
down.

Because it doesn't have a way of knowing the state until this point, 
it will also not be able to tell you the state via ipsec auto --status.

&gt; However, comparing output from a working tunnel with that of one that
&gt; was closed 
&gt; did not show clearly show tunnel status.

If your tunnel is down but not 'unrouted' (see man ipsec_auto), you
should not be able to ping the opposite side of the tunnel. You can
use this as an indicator of tunnel status.

On a related note, you may be interested to know that as of 1.7, 
redundant tunnels caused by RW disconnections are likely to be 
less of a pain. From doc/CHANGES:

    There is a new configuration parameter, uniqueids, to control a new Pluto
    option:  when a new connection is negotiated with the same ID as an old
    one, the old one is deleted immediately.  This should help eliminate
    dangling Road Warrior connections when the same Road Warrior reconnects. 
    It thus requires that IDs not be shared by hosts (a previously legal but
    probably useless capability).  NOTE WELL:  the sample ipsec.conf now has
    uniqueids=yes in its config-setup section.


Cheers,

Claudia</PRE>
<H3><A name="demanddial">Can I build IPsec tunnels over a demand-dialed
 link?</A></H3>
<P>This is possible, but not easy. FreeS/WAN technical lead Henry
 Spencer wrote:</P>
<PRE>&gt; 5. If the ISDN link goes down in between and is reestablished, the SAs
&gt; are still up but the eroute are deleted and the IPsec interface shows
&gt; garbage (with ifconfig)
&gt; 6. Only restarting IPsec will bring the VPN back online.

This one is awkward to solve.  If the real interface that the IPsec
interface is mounted on goes down, it takes most of the IPsec machinery
down with it, and a restart is the only good way to recover. 

The only really clean fix, right now, is to split the machines in two: 

1. A minimal machine serves as the network router, and only it is aware
that the link goes up and down. 

2. The IPsec is done on a separate gateway machine, which thinks it has
a permanent network connection, via the router.

This is clumsy but it does work.  Trying to do both functions within a
single machine is tricky.  There is a software package (diald) which will
give the illusion of a permanent connection for demand-dialed modem
connections; I don't know whether it's usable for ISDN, or whether it can
be made to cooperate properly with FreeS/WAN. 

Doing a restart each time the interface comes up *does* work, although it
is a bit painful.  I did that with PPP when I was running on a modem link;
it wasn't hard to arrange the PPP scripts to bring IPsec up and down at
the right times.  (I'd meant to investigate diald but never found time.)

In principle you don't need to do a complete restart on reconnect, but you
do have to rebuild some things, and we have no nice clean way of doing
only the necessary parts.</PRE>
<P>In the same thread, one user commented:</P>
<PRE>Subject: Re: linux-ipsec: IPsec and Dial Up Connections
   Date: Wed, 22 Nov 2000
   From: Andy Bradford &lt;andyb@calderasystems.com&gt;

On Wed, 22 Nov 2000 19:47:11 +0100, Philip Reetz wrote:

&gt; Are there any ideas what might be the cause of the problem and any way
&gt; to work around it.
&gt; Any help is highly appreciated.

On my laptop, when using ppp there is a ip-up script in /etc/ppp that 
will be executed each time that the ppp interface is brought up.  
Likewise there is an ip-down script that is called when it is taken 
down.  You might consider custimzing those to stop and start FreeS/WAN 
with each connection.  I believe that ISDN uses the same files, though 
I could be wrong---there should be something similar though.</PRE>
<H3><A name="GRE">Can I build GRE, L2TP or PPTP tunnels over IPsec?</A></H3>
<P>Yes. Normally this is not necessary, but it is useful in a few
 special cases. For example, if you must route non-IP packets such as
 IPX, you will need to use a tunneling protocol that can route these
 packets. IPsec can be layered around it for extra security. Another
 example: you can provide failover protection for high availability (HA)
 environments by combining IPsec with other tools. Ken Bantoft describes
 one such setup in<A HREF="http://www.freeswan.ca/docs/HA"> Using
 FreeS/WAN with Linux-HA, GRE, OSPF and BGP for enterprise grade VPN
 solutions</A>.</P>
<P>GRE over IPsec is covered as part of<A HREF="http://www.freeswan.ca/docs/HA">
 that document</A>.<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/07/msg00209.html">
 Here are links</A> to other GRE resources. Jacco de Leuw has created<A HREF="http://www.jacco2.dds.nl/networking/">
 this page on L2TP over IPsec</A> with instructions for FreeS/WAN and
 several other brands of IPsec software.</P>
<P>Please let us know of other useful links via the<A HREF="mail.html">
 mailing lists</A>.</P>
<H3><A name="NetBIOS">... use Network Neighborhood (Samba, NetBIOS) over
 IPsec?</A></H3>
<P>Your local PC needs to know how to translate NetBIOS names to IP
 addresses. It may do this either via a local LMHOSTS file, or using a
 local or remote WINS server. The WINS server is preferable since it
 provides a centralized source of the information to the entire network.
 To use a WINS server over the<A HREF="#VPN"> VPN</A> (or any IP-based
 network), you must enable &quot;NetBIOS over TCP&quot;.</P>
<P><A HREF="http://www.samba.org">Samba</A> can emulate a WINS server on
 Linux.</P>
<P> See also several discussions in our<A HREF="http://lists.freeswan.org/pipermail/users/2002-September/thread.html">
 September 2002 Users archives</A></P>
<H2><A name="setup.faq">Life's little mysteries</A></H2>
<P>FreeS/WAN is a fairly complex product. (Neither the networks it runs
 on nor the protocols it uses are simple, so it could hardly be
 otherwise.) It therefore sometimes exhibits behaviour which can be
 somewhat confusing, or has problems which are not easy to diagnose.
 This section tries to explain those problems.</P>
<P>Setup and configuration of FreeS/WAN are covered in other
 documentation sections:</P>
<UL>
<LI><A href="quickstart.html">basic setup and configuration</A></LI>
<LI><A href="adv_config.html">advanced configuration</A></LI>
<LI><A href="trouble.html">Troubleshooting</A></LI>
</UL>
<P>However, we also list some of the commonest problems here.</P>
<H3><A name="cantping">I cannot ping ....</A></H3>
<P>This question is dealt with in the advanced configuration section
 under the heading<A href="#multitunnel"> multiple tunnels</A>.</P>
<P>The standard subnet-to-subnet tunnel protects traffic<STRONG> only
 between the subnets</STRONG>. To test it, you must use pings that go
 from one subnet to the other.</P>
<P>For example, suppose you have:</P>
<PRE>      subnet a.b.c.0/24
             |
      eth1 = a.b.c.1
         gate1
      eth0 = 192.0.2.8
             |

       ~ internet ~

             |
      eth0 = 192.0.2.11
         gate2
      eth1 = x.y.z.1
              |
       subnet x.y.z.0/24</PRE>
<P>and the connection description:</P>
<PRE>conn abc-xyz
     left=192.0.2.8
     leftsubnet=a.b.c.0/24
     right=192.0.2.11
     rightsubnet=x.y.z.0/24</PRE>
<P>You can test this connection description only by sending a ping that
 will actually go through the tunnel. Assuming you have machines at
 addresses a.b.c.2 and x.y.z.2, pings you might consider trying are:</P>
<DL>
<DT>ping from x.y.z.2 to a.b.c.2 or vice versa</DT>
<DD>Succeeds if tunnel is working. This is the<STRONG> only valid test
 of the tunnel</STRONG>.</DD>
<DT>ping from gate2 to a.b.c.2 or vice versa</DT>
<DD><STRONG>Does not use tunnel</STRONG>. gate2 is not on protected
 subnet.</DD>
<DT>ping from gate1 to x.y.z.2 or vice versa</DT>
<DD><STRONG>Does not use tunnel</STRONG>. gate1 is not on protected
 subnet.</DD>
<DT>ping from gate1 to gate2 or vice versa</DT>
<DD><STRONG>Does not use tunnel</STRONG>. Neither gate is on a protected
 subnet.</DD>
</DL>
<P>Only the first of these is a useful test of this tunnel. The others
 do not use the tunnel. Depending on other details of your setup and
 routing, they:</P>
<UL>
<LI>either fail, telling you nothing about the tunnel</LI>
<LI>or succeed, telling you nothing about the tunnel since these packets
 use some other route</LI>
</UL>
<P>In some cases, you may be able to get around this. For the example
 network above, you could use:</P>
<PRE>        ping -I a.b.c.1 x.y.z.1</PRE>
<P>Both the adresses given are within protected subnets, so this should
 go through the tunnel.</P>
<P>If required, you can build additional tunnels so that all the
 machines involved can talk to all the others. See<A href="#multitunnel">
 multiple tunnels</A> in the advanced configuration document for
 details.</P>
<H3><A name="forever">It takes forever to ...</A></H3>
<P>Users fairly often report various problems involving long delays,
 sometimes on tunnel setup and sometimes on operations done through the
 tunnel, occasionally on simple things like ping or more often on more
 complex operations like doing NFS or Samba through the tunnel.</P>
<P>Almost always, these turn out to involve failure of a DNS lookup. The
 timeouts waiting for DNS are typically set long so that you won't time
 out when a query involves multiple lookups or long paths. Genuine
 failures therefore produce long delays before they are detected.</P>
<P>A mailing list message from project technical lead Henry Spencer:</P>
<PRE>&gt; ... when i run /etc/rc.d/init.d/ipsec start, i get:
&gt; ipsec_setup: Starting FreeS/WAN IPsec 1.5...
&gt; and it just sits there, doesn't give back my bash prompt.

Almost certainly, the problem is that you're using DNS names in your
ipsec.conf, but DNS lookups are not working for some reason.  You will
get your prompt back... eventually.  But the DNS timeouts are long.
Doing something about this is on our list, but it is not easy.</PRE>
<P>In the meanwhile, we recommend that connection descriptions in<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A> use numeric IP addresses rather than names which will
 require a DNS lookup.</P>
<P>Names that do not require a lookup are fine. For example:</P>
<UL>
<LI>a road warrior might use the identity<VAR>
 rightid=@lancelot.example.org</VAR></LI>
<LI>the gateway might use<VAR> leftid=@camelot.example.org</VAR></LI>
</UL>
<P>These are fine. The @ sign prevents any DNS lookup. However, do not
 attempt to give the gateway address as<VAR> left=camelot.example.org</VAR>
. That requires a lookup.</P>
<P>A post from one user after solving a problem with long delays:</P>
<PRE>Subject: Final Answer to Delay!!!
   Date: Mon, 19 Feb 2001
   From: &quot;Felippe Solutions&quot; &lt;felippe@solutionstecnologia.com.br&gt;

Sorry people, but seems like the Delay problem had nothing to do with
freeswan.

The problem was DNS as some people sad from the beginning, but not the way
they thought it was happening. Samba, ssh, telnet and other apps try to
reverse lookup addresses when you use IP numbers (Stupid that ahh).

I could ping very fast because I always ping with &quot;-n&quot; option, but I don't
know the option on the other apps to stop reverse addressing so I don't use
it.</PRE>
<P>This post is fairly typical. These problems are often tricky and
 frustrating to diagnose, and most turn out to be DNS-related.</P>
<P>One suggestion for diagnosis: test with both names and addresses if
 possible. For example, try all of:</P>
<UL>
<LI>ping<VAR> address</VAR></LI>
<LI>ping -n<VAR> address</VAR></LI>
<LI>ping<VAR> name</VAR></LI>
</UL>
<P>If these behave differently, the problem must be DNS-related since
 the three commands do exactly the same thing except for DNS lookups.</P>
<H3><A name="route">I send packets to the tunnel with route(8) but they
 vanish</A></H3>
<P>IPsec connections are designed to carry only packets travelling
 between pre-defined connection endpoints. As project technical lead
 Henry Spencer put it:</P>
<BLOCKQUOTE> IPsec tunnels are not just virtual wires; they are virtual
 wires with built-in access controls. Negotiation of an IPsec tunnel
 includes negotiation of access rights for it, which don't include
 packets to/from other IP addresses. (The protocols themselves are quite
 inflexible about this, so there are limits to what we can do about it.)</BLOCKQUOTE>
<P>For fairly obvious security reasons, and to comply with the IPsec
 RFCs,<A href="#KLIPS"> KLIPS</A> drops any packets it receives that are
 not allowed on the tunnels currently defined. So if you send it packets
 with<VAR> route(8)</VAR>, and suitable tunnels are not defined, the
 packets vanish. Whether this is reported in the logs depends on the
 setting of<VAR> klipsdebug</VAR> in your<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A> file.</P>
<P>To rescue vanishing packets, you must ensure that suitable tunnels
 for them exist, by editing the connection descriptions in<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A>. For example, supposing you have a simple setup:</P>
<PRE>         leftsubnet -- leftgateway === internet === roadwarrior</PRE>
<P>If you want to give the roadwarrior access to some resource that is
 located behind the left gateway but is not in the currently defined
 left subnet, then the usual procedure is to define an additional tunnel
 for those packets by creating a new connection description.</P>
<P>In some cases, it may be easier to alter an existing connection
 description, enlarging the definition of<VAR> leftsubnet</VAR>. For
 example, instead of two connection descriptions with 192.168.8.0/24 and
 192.168.9.0/24 as their<VAR> leftsubnet</VAR> parameters, you can use a
 single description with 192.168.8.0/23.</P>
<P>If you have multiple endpoints on each side, you need to ensure that
 there is a route for each pair of endpoints. See this<A href="#multitunnel">
 example</A>.</P>
<H3><A name="down_route">When a tunnel goes down, packets vanish</A></H3>
<P>This is a special case of the vanishing packet problem described in
 the previous question. Whenever KLIPS sees packets for which it does
 not have a tunnel, it drops them.</P>
<P>When a tunnel goes away, either because negotiations with the other
 gateway failed or because you gave an<VAR> ipsec auto --down</VAR>
 command, the route to its other end is left pointing into KLIPS, and
 KLIPS will drop packets it has no tunnel for.</P>
<P>This is a documented design decision, not a bug. FreeS/WAN must not
 automatically adjust things to send packets via another route. The
 other route might be insecure.</P>
<P>Of course, re-routing may be necessary in many cases. In those cases,
 you have to do it manually or via scripts. We provide the<VAR> ipsec
 auto --unroute</VAR> command for these cases.</P>
<P>From<A href="manpage.d/ipsec_auto.8.html"> ipsec_auto(8)</A>:</P>
<BLOCKQUOTE> Normally, pluto establishes a route to the destination
 specified for a connection as part of the --up operation. However, the
 route and only the route can be established with the --route operation.
 Until and unless an actual connection is established, this discards any
 packets sent there, which may be preferable to having them sent
 elsewhere based on a more general route (e.g., a default route).</BLOCKQUOTE><BLOCKQUOTE>
 Normally, pluto's route to a destination remains in place when a --down
 operation is used to take the connection down (or if connection setup,
 or later automatic rekeying, fails). This permits establishing a new
 connection (perhaps using a different specification; the route is
 altered as necessary) without having a ``window'' in which packets
 might go elsewhere based on a more general route. Such a route can be
 removed using the --unroute operation (and is implicitly removed by
 --delete).</BLOCKQUOTE>
<P>See also this mailing list<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/11/msg00523.html">
 message</A>.</P>
<H3><A name="firewall_ate">The firewall ate my packets!</A></H3>
<P>If firewalls filter out:</P>
<UL>
<LI>either the UDP port 500 packets used in IKE negotiations</LI>
<LI>or the ESP and AH (protocols 50 and 51) packets used to implement
 the IPsec tunnel</LI>
</UL>
<P>then IPsec cannot work. The first thing to check if packets seem to
 be vanishing is the firewall rules on the two gateway machines and any
 other machines along the path that you have access to.</P>
<P>For details, see our document on<A href="firewall.html"> firewalls</A>
.</P>
<P>Some advice from technical lead Henry Spencer on diagnosing such
 problems:</P>
<PRE>&gt; &gt; Packets vanishing between the hardware interface and the ipsecN interface
&gt; &gt; is usually the result of firewalls not being configured to let them in...
&gt; 
&gt; Thanks for the suggestion. If only it were that simple! My ipchains startup
&gt; script does take care of that, but just in case I manually inserted rules 
&gt; accepting everything from london on dublin. No difference.

The other thing to check is whether the &quot;RX packets dropped&quot; count on the
ipsecN interface (run &quot;ifconfig ipsecN&quot;, for N=1 or whatever, to see the
counts) is rising.  If so, then there's some sort of configuration mismatch
between the two ends, and IPsec itself is rejecting them.  If none of the
ipsecN counts is rising, then the packets are never reaching the IPsec
machinery, and the problem is almost certainly in firewalls etc.</PRE>
<H3><A name="dropconn">Dropped connections</A></H3>
<P>Networks being what they are, IPsec connections can be broken for any
 number of reasons, ranging from hardware failures to various software
 problems such as the path MTU problems discussed<A href="#pmtu.broken">
 elsewhere in the FAQ</A>. Fortunately, various diagnostic tools exist
 that help you sort out many of the possible problems.</P>
<P>There is one situation, however, where FreeS/WAN (using default
 settings) may destroy a connection for no readily apparent reason. This
 occurs when things are<STRONG> misconfigured</STRONG> so that<STRONG>
 two tunnels</STRONG> from the same gateway expect<STRONG> the same
 subnet on the far end</STRONG>.</P>
<P>In this situation, the first tunnel comes up fine and works until the
 second is established. At that point, because of the way we track
 connections internally, the first tunnel ceases to exist as far as this
 gateway is concerned. Of course the far end does not know that, and a
 storm of error messages appears on both systems as it tries to use the
 tunnel.</P>
<P>If the far end gives up, goes back to square one and negotiates a new
 tunnel, then that wipes out the second tunnel and ...</P>
<P>The solution is simple.<STRONG> Do not build multiple conn
 descriptions with the same remote subnet</STRONG>.</P>
<P>This is actually intended to be a feature, rather than a bug.
 Consider the situation where a single remote system goes down, then
 comes back up and reconnects to the gateway. It is useful to have the
 gateway tear down the old tunnel and recover resources when the
 reconnection is made. It recognises that situation by checking the
 remote subnet for each tunnel it builds and discarding duplicates. This
 works fine as long as you don't configure multiple tunnels with the
 same remote subnet.</P>
<P>If this behaviour is inconvenient for you, you can disable it by
 setting<VAR> uniqueids=no</VAR> in<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A>.</P>
<H3><A name="defaultroutegone">Disappearing %defaultroute</A></H3>
<P>When an underlying connection (eg. ppp) goes down, FreeS/WAN will not
 recover properly without a little help. Here are the symptoms that
 FreeS/WAN user Michael Carmody noticed:</P>
<PRE>
&gt; After about 24 hours the freeswan connection takes over the default route.
&gt; 
&gt; i.e instead of deafult gateway pointing to the router via eth0, it becomes a 
&gt; pointer to the router via ipsec0.
 
&gt; All internet access is then lost as all replies (and not just the link I 
&gt; wanted) are routed out ipsec0 and the router doesn't respond to the ipsec 
&gt; traffic.
</PRE>
<P>If you're using a FreeS/WAN 2.x/KLIPS system, simply re-attach the
 IPsec virtual interface with<EM> ipsec tnconfig</EM> command such as:</P>
<PRE>    ipsec tnconfig --attach --virtual ipsec0 --physical ppp0</PRE>
<P>In your command, name the physical and virtual interfaces as they
 appear paired on your system during regular uptime. For a system with
 several physical/virtual interface pairs on flaky links, you'll need
 more than one such command. If you're using FreeS/WAN 1.x, you must
 restart FreeS/WAN, which is more time consuming.</P>
<P><A href="http://lists.freeswan.org/pipermail/design/2002-July/003070.html">
 Here</A> is a script which can help to automate the process of
 FreeS/WAN restart at need. It could easily be adapted to use tnconfig
 instead.</P>
<H3><A name="tcpdump.faq">TCPdump on the gateway shows strange things</A>
</H3>
 As another user pointed out, keeping the connect
<P>Attempting to look at IPsec packets by running monitoring tools on
 the IPsec gateway machine can produce silly results. That machine is
 mangling the packets for IPsec, and possibly for firewall or NAT
 purposes as well. If the internals of the machine's IP stack are not
 what the monitoring tool expects, then the tool can misinterpret them
 and produce nonsense output.</P>
<P>See our<A href="#tcpdump.test"> testing</A> document for more detail.</P>
<H3><A name="no_trace">Traceroute does not show anything between the
 gateways</A></H3>
<P>As far as traceroute can see, the two gateways are one hop apart; the
 data packet goes directly from one to the other through the tunnel. Of
 course the outer packets that implement the tunnel pass through
 whatever lies between the gateways, but those packets are built and
 dismantled by the gateways. Traceroute does not see them and cannot
 report anything about their path.</P>
<P>Here is a mailing list message with more detail.</P>
<PRE>Date: Mon, 14 May 2001
To: linux-ipsec@freeswan.org
From: &quot;John S. Denker&quot; &lt;jsd@research.att.com&lt;
Subject: Re: traceroute: one virtual hop

At 02:20 PM 5/14/01 -0400, Claudia Schmeing wrote:
&gt;
&gt;&gt; &gt; A bonus question: traceroute in subnet to subnet enviroment looks like:
&gt;&gt; &gt; 
&gt;&gt; &gt; traceroute to andris.dmz (172.20.24.10), 30 hops max, 38 byte packets
&gt;&gt; &gt; 1  drama (172.20.1.1)  0.716 ms  0.942 ms  0.434 ms
&gt;&gt; &gt; 2  * * *
&gt;&gt; &gt; 3  andris.dmz (172.20.24.10)  73.576 ms  78.858 ms  79.434 ms
&gt;&gt; &gt; 
&gt;&gt; &gt; Why aren't there the other hosts which take part in the delivery during 
&gt;    * * * ?
&gt;
&gt;If there is an ipsec tunnel between GateA and Gate B, this tunnel forms a 
&gt;'virtual wire'.  When it is tunneled, the original packet becomes an inner 
&gt;packet, and new ESP and/or AH headers are added to create an outer packet 
&gt;around it. You can see an example of how this is done for AH at 
&gt;doc/ipsec.html#AH . For ESP it is similar.
&gt;
&gt;Think about the packet's path from the inner packet's perspective.
&gt;It leaves the subnet, goes into the tunnel, and re-emerges in the second
&gt;subnet. This perspective is also the only one available to the
&gt;'traceroute' command when the IPSec tunnel is up.

Claudia got this exactly right.  Let me just expand on a couple of points:

*) GateB is exactly one (virtual) hop away from GateA.  This is how it
would be if there were a physically private wire from A to B.  The
virtually private connection should work the same, and it does.

*) While the information is in transit from GateA to GateB, the hop count
of the outer header (the &quot;envelope&quot;) is being decremented.  The hop count
of the inner header (the &quot;contents&quot; of the envelope) is not decremented and
should not be decremented.  The hop count of the outer header is not
derived from and should not be derived from the hop count of the inner header.

Indeed, even if the packets did time out in transit along the tunnel, there
would be no way for traceroute to find out what happened.  Just as
information cannot leak _out_ of the tunnel to the outside, information
cannot leak _into_ the tunnel from outside, and this includes ICMP messages
from routers along the path.

There are some cases where one might wish for information about what is
happening at the IP layer (below the tunnel layer) -- but the protocol
makes no provision for this.  This raises all sorts of conceptual issues.
AFAIK nobody has ever cared enough to really figure out what _should_
happen, let alone implement it and standardize it.

*) I consider the &quot;* * *&quot; to be a slight bug.  One might wish for it to be
replaced by &quot;GateB GateB GateB&quot;.  It has to do with treating host-to-subnet
traffic different from subnet-to-subnet traffic (and other gory details).
I fervently hope KLIPS2 will make this problem go away.

*) If you want to ask questions about the link from GateA to GateB at the
IP level (below the tunnel level), you have to ssh to GateA and launch a
traceroute from there.</PRE>
<H2><A name="man4debug">Testing in stages</A></H2>
<P>It is often useful in debugging to test things one at a time:</P>
<UL>
<LI>disable IPsec entirely, for example by turning it off with
 chkconfig(8), and make sure routing works</LI>
<LI>Once that works, try a manually keyed connection. This does not
 require key negotiation between Pluto and the key daemon on the other
 end.</LI>
<LI>Once that works, try automatically keyed connections</LI>
<LI>Once IPsec works, add packet compression</LI>
<LI>Once everything seems to work, try stress tests with large
 transfers, many connections, frequent re-keying, ...</LI>
</UL>
<P>FreeS/WAN releases are tested for all of these, so you can be
 reasonably certain they<EM> can</EM> do them all. Of course, that does
 not mean they<EM> will</EM> on the first try, especially if you have
 some unusual configuration.</P>
<P>The rest of this section gives information on diagnosing the problem
 when each of the above steps fails.</P>
<H3><A name="nomanual">Manually keyed connections don't work</A></H3>
<P>Suspect one of:</P>
<UL>
<LI>mis-configuration of IPsec system in the /etc/ipsec.conf file
<BR> common errors are incorrect interface or next hop information</LI>
<LI>mis-configuration of manual connection in the /etc/ipsec.conf file</LI>
<LI>routing problems causing IPsec packets to be lost</LI>
<LI>bugs in KLIPS</LI>
<LI>mismatch between the transforms we support and those another IPsec
 implementation offers.</LI>
</UL>
<H3><A name="spi_error">One manual connection works, but second one
 fails</A></H3>
<P>This is a fairly common problem when attempting to configure multiple
 manually keyed connections from a single gateway.</P>
<P>Each connection must be identified by a unique<A href="#SPI"> SPI</A>
 value. For automatic connections, these values are assigned
 automatically. For manual connections, you must set them with<VAR> spi=</VAR>
 statements in<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf(5)</A>.</P>
<P>Each manual connection must have a unique SPI value in the range
 0x100 to 0x999. Two or more with the same value will fail. For details,
 see our doc section<A href="#prodman"> Using manual keying in
 production</A> and the man page<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A>.</P>
<H3><A name="man_no_auto">Manual connections work, but automatic keying
 doesn't</A></H3>
<P>The most common reason for this behaviour is a firewall dropping the
 UDP port 500 packets used in key negotiation.</P>
<P>Other possibilities:</P>
<UL>
<LI>mis-configuration of auto connection in the /etc/ipsec.conf file.
<P>One common configuration error is forgetting that you need<VAR>
 auto=add</VAR> to load the connection description on the receiving end
 so it recognises the connection when the other end asks for it.</P>
</LI>
<LI>error in shared secret in /etc/ipsec.secrets</LI>
<LI>one gateway lacks a route to the other so Pluto's UDP packets are
 lost</LI>
<LI>bugs in Pluto</LI>
<LI>incompatibilities between Pluto's<A href="#IKE"> IKE</A>
 implementation and the IKE at the other end of the tunnel.
<P>Some possibile problems are discussed in out<A href="interop.html#interop.problem">
 interoperation</A> document.</P>
</LI>
</UL>
<H3><A name="nocomp">IPsec works, but connections using compression fail</A>
</H3>
<P>When we first added compression, we saw some problems:</P>
<UL>
<LI>compatibility issues with other implementations. We followed the
 RFCs and omitted some extra material that many compression libraries
 add by default. Some other implementations left the extras in</LI>
<LI>bugs in assembler compression routines on non-Intel CPUs. The
 workaround is to use C code instead of possibly problematic assembler.</LI>
</UL>
<P>We have not seen either problem in some time (at least six months as
 I write in March 2002), but if you have some unusual configuration then
 you may see them.</P>
<H3><A name="pmtu.broken">Small packets work, but large transfers fail</A>
</H3>
<P>If tests with ping(1) and a small packet size succeed, but tests or
 transfers with larger packet sizes fail, suspect problems with packet
 fragmentation and perhaps<A href="#pathMTU"> path MTU discovery</A>.</P>
<P>Our<A href="#bigpacket"> troubleshooting document</A> covers these
 problems. Information on the underlying mechanism is in our<A href="#MTU.trouble">
 background</A> document.</P>
<H3><A name="subsub">Subnet-to-subnet works, but tests from the gateways
 don't</A></H3>
<P>This is described under<A href="#cantping"> I cannot ping...</A>
 above.</P>
<H2><A name="compile.faq">Compilation problems</A></H2>
<H3><A name="gmp.h_missing">gmp.h: No such file or directory</A></H3>
<P>Pluto needs the GMP (<STRONG>G</STRONG>NU</P>
<P><STRONG>M</STRONG>ulti-<STRONG>P</STRONG>recision) library for the
 large integer calculations it uses in<A href="#public"> public key</A>
 cryptography. This error message indicates a failure to find the
 library. You must install it before Pluto will compile.</P>
<P>The GMP library is included in most Linux distributions. Typically,
 there are two RPMs, libgmp and libgmp-devel, You need to<EM> install
 both</EM>, either from your distribution CDs or from your vendor's web
 site.</P>
<P>On Debian, a mailing list message reports that the command to give is<VAR>
 apt-get install gmp2</VAR>.</P>
<P>For more information and the latest version, see the<A href="http://www.swox.com/gmp/">
 GMP home page</A>.</P>
<H3><A name="noVM">... virtual memory exhausted</A></H3>
<P>We have had several reports of this message appearing, all on SPARC
 Linux. Here is a mailing message on a solution:</P>
<PRE>&gt; ipsec_sha1.c: In function `SHA1Transform':
&gt; ipsec_sha1.c:95: virtual memory exhausted

I'm seeing exactly the same problem on an Ultra with 256MB ram and 500
MB swap.  Except I am compiling version 1.5 and its Red Hat 6.2.

I can get around this by using -O instead of -O2 for the optimization
level.  So it is probably a bug in the optimizer on the sparc complier. 
I'll try and chase this down on the sparc lists.</PRE>
<H2><A name="error">Interpreting error messages</A></H2>
<H3><A name="route-client">route-client (or host) exited with status 7</A>
</H3>
<P>Here is a discussion of this error from FreeS/WAN &quot;listress&quot; (mailing
 list tech support person) Claudia Schmeing. The &quot;FAQ on the network
 unreachable error&quot; which she refers to is the next question below.</P>
<PRE>&gt; I reached the point where the two boxes (both on dial-up connections, but
&gt; treated as static IPs by getting the IP and editing ipsec.conf after the
&gt; connection is established) to the point where they exchange some info, but I
&gt; get an error like &quot;route-client command exited with status 7 \n internal
&gt; error&quot;.
&gt; Where can I find a description of this error?

In general, if the FAQ doesn't cover it, you can search the mailing list 
archives - I like to use
http://www.sandelman.ottawa.on.ca/linux-ipsec/
but you can see doc/mail.html for different archive formats.


Your error comes from the _updown script, which performs some
routing and firewall functions to help Linux FreeS/WAN. More info
is available at doc/firewall.html and man ipsec.conf. Its routing
is integral to the health of Linux FreeS/WAN; it also provides facility
to insert custom firewall rules to be executed when you create or destroy
a connection.

Yours is, of course, a routing error. You can be fairly sure the routing 
machinery is saying &quot;network is unreachable&quot;. There's a FAQ on the 
&quot;network is unreachable&quot; error, but more information is available now; read on.

If your _updown script is recent (for example if it shipped with 
Linux FreeS/WAN 1.91), you will see another debugging line in your logs 
that looks something like this:

&gt; output: /usr/local/lib/ipsec/_updown: `route add -net 128.174.253.83 
&gt; netmask 255.255.255.255 dev ipsec0 gw 66.92.93.161' failed

This is, of course, the system route command that exited with status 7, 
(ie. failed). Man route for details. Seeing the command typed out yields 
more information. If your _updown script is older, you may wish to update 
it to show the command explicitly.

Three parameters fed to the route command: net, netmask and gw [gateway] 
are derived from things you've put in ipsec.conf.

Net and netmask are derived from the peer's IP and mask. In more detail:

You may see a routing error when routing to a client (ie. subnet), or 
to a host (IPSec gateway or freestanding host; a box that does IPSec for
itself). In _updown, the &quot;route-client&quot; section  is responsible to set up 
the route for IPSec'd (usually, read 'tunneled') packets headed to a 
peer subnet. Similarly, route-host routes IPSec'd packets to a peer host
or IPSec gateway.

When routing to a 'client', net and netmask are ipsec.conf's left- or 
rightsubnet (whichever is not local). Similarly, when routing to a 
'host' the net is left or right. Host netmask is always /32, indicating a 
single machine.

Gw is nexthop's value. Again, the value in question is left- or rightnexthop,
whichever is local. Where left/right or left-/rightnexthop has the special 
value %defaultroute (described in man ipsec.conf), gw will automagically get
the value of the next hop on the default route.

Q: &quot;What's a nexthop and why do I need one?&quot;

A: 'nexthop' is a routing kluge; its value is the next hop away
   from the machine that's doing IPSec, and toward your IPSec peer. 
   You need it to get the processed packets out of the local system and 
   onto the wire. While we often route other packets through the machine 
   that's now doing IPSec, and are done with it, this does not suffice here. 
   After packets are processed with IPSec, this machine needs to know where 
   they go next. Of course using the 'IPSec gateway' as their routing gateway 
   would cause an infinite loop! [To visualize this, see the packet flow 
   diagram at doc/firewall.html.] To avoid this, we route packets through 
   the next hop down their projected path.

Now that you know the background, consider:
1. Did you test routing between the gateways in the absence of Linux
   FreeS/WAN, as recommended? You need to ensure the two machines that
   will be running Linux FreeS/WAN can route to one another before trying to 
   make a secure connection.
2. Is there anything obviously wrong with the sense of your route command?

Normally, this problem is caused by an incorrect local nexthop parameter.
Check out the use of %defaultroute, described in man ipsec.conf. This is
a simple way to set nexthop for most people. To figure nexthop out by hand,
traceroute in-the-clear to your IPSec peer. Nexthop is the traceroute's 
first hop after your IPSec gateway.</PRE>
<H3><A name="unreachable">SIOCADDRT:Network is unreachable</A></H3>
<P>This message is not from FreeS/WAN, but from the Linux IP stack
 itself. That stack is seeing packets it has no route for, either
 because your routing was broken before FreeS/WAN started or because
 FreeS/WAN's changes broke it.</P>
<P>Here is a message from Claudia suggesting ways to diagnose and fix
 such problems:</P>
<PRE>You write,
&gt; I have correctly installed freeswan-1.8 on RH7.0 kernel 2.2.17, but when 
&gt; I setup a VPN connection with the other machine(RH5.2 Kernel 2.0.36 
&gt; freeswan-1.0, it works well.) it told me that 
&gt; &quot;SIOCADDRT:Network is unreachable&quot;!  But the network connection is no 
&gt; problem.

Often this error is the result of a misconfiguration. 

Be sure that you can route successfully in the absence of Linux
FreeS/WAN. (You say this is no problem, so proceed to the next step.)

Use a custom copy of the default updownscript. Do not change the route 
commands, but add a diagnostic message revealing the exact text of the 
route command. Is there a problem with the sense of the route command
that you can see? If so, then re-examine those ipsec.conf settings
that are being sent to the route command. 

You may wish to use the ipsec auto --route and --unroute commands to 
troubleshoot the problem. See man ipsec_auto for details.</PRE>
<P>Since the above message was written, we have modified the updown
 script to provide a better diagnostic for this problem. Check<VAR>
 /var/log/messages</VAR>.</P>
<P>See also the FAQ question<A href="#route-client"> route-client (or
 host) exited with status 7</A>.</P>
<H3><A name="modprobe">ipsec_setup: modprobe: Can't locate module ipsec</A>
</H3>
<H3><A name="noKLIPS">ipsec_setup: Fatal error, kernel appears to lack
 KLIPS</A></H3>
<P>These messages indicate an installation failure. The kernel you are
 running does not contain the<A href="#KLIPS"> KLIPS (kernel IPsec)</A>
 code.</P>
<P>Note that the &quot;modprobe: Can't locate module ipsec&quot; message appears
 even if you are not using modules. If there is no KLIPS in your kernel,
 FreeS/WAN tries to load it as a module. If that fails, you get this
 message.</P>
<P>Commands you can quickly try are:</P>
<DL>
<DT><VAR>uname -a</VAR></DT>
<DD>to get details, including compilation date and time, of the
 currently running kernel</DD>
<DT><VAR>ls /</VAR></DT>
<DT><VAR>ls /boot</VAR></DT>
<DD>to ensure a new kernel is where it should be. If kernel compilation
 puts it in<VAR> /</VAR> but<VAR> lilo</VAR> wants it in<VAR> /boot</VAR>
, then you should uncomment the<VAR> INSTALL_PATH=/boot</VAR> line in
 the kernel<VAR> Makefile</VAR>.</DD>
<DT><VAR>more /etc/lilo.conf</VAR></DT>
<DD>to see that<VAR> lilo</VAR> has correct information</DD>
<DT><VAR>lilo</VAR></DT>
<DD>to ensure that information in<VAR> /etc/lilo.conf</VAR> has been
 transferred to the boot sector</DD>
</DL>
<P>If those don't find the problem, you have to go back and check
 through the<A href="install.html"> install</A> procedure to see what
 was missed.</P>
<P>Here is one of Claudia's messages on the topic:</P>
<PRE>&gt; I tried to install freeswan 1.8 on my mandrake 7.2 test box. ...

&gt; It does show version and some output for whack.

Yes, because the Pluto (daemon) part of ipsec is installed correctly, but
as we see below the kernel portion is not.

&gt; However, I get the following from /var/log/messages:
&gt; 
&gt; Mar 11 22:11:55 pavillion ipsec_setup: Starting FreeS/WAN IPsec 1.8...
&gt; Mar 11 22:12:02 pavillion ipsec_setup: modprobe: Can't locate module ipsec
&gt; Mar 11 22:12:02 pavillion ipsec_setup: Fatal error, kernel appears to lack
&gt; KLIPS.

This is your problem. You have not successfully installed a kernel with
IPSec machinery in it. 

Did you build Linux FreeS/WAN as a module? If so, you need to ensure that 
your new module has been installed in the directory where your kernel 
loader normally finds your modules. If not, you need to ensure
that the new IPSec-enabled kernel is being loaded correctly.

See also doc/install.html, and INSTALL in the distro.</PRE>
<H3><A name="noDNS">ipsec_setup: ... failure to fetch key for ... from
 DNS</A></H3>
<P>Quoting Henry:</P>
<PRE>Note that by default, FreeS/WAN is now set up to
     (a) authenticate with RSA keys, and
     (b) fetch the public key of the far end from DNS.
Explicit attention to  ipsec.conf will be needed if you want
to do something different.</PRE>
<P>and Claudia, responding to the same user:</P>
<PRE>You write,

&gt;       My current setup in ipsec.conf is leftrsasigkey=%dns I have 
&gt; commented this and authby=rsasig out. I am able to get ipsec running, 
&gt; but what I find is that the documentation only specifies for %dns are 
&gt; there any other values that can be placed in this variable other than 
&gt; %dns and the key? I am also assuming that this is where I would place 
&gt; my public key for the left and right side as well is this correct?

Valid values for authby= are rsasig and secret, which entail authentication
by RSA signature or by shared secret, respectively. Because you have 
commented authby=rsasig out, you are using the default value of authby=secret. 

When using RSA signatures, there are two ways to get the public key for the
IPSec peer: either copy it directly into *rsasigkey= in ipsec.conf, or
fetch it from dns. The magic value %dns for *rsasigkey parameters says to 
try to fetch the peer's key from dns.

For any parameters, you may find their significance and special values in
man ipsec.conf. If you are setting up keys or secrets, be sure also to
reference man ipsec.secrets.</PRE>
<H3><A name="dup_address">ipsec_setup: ... interfaces ... and ... share
 address ...</A></H3>
<P>This is a fatal error. FreeS/WAN cannot cope with two or more
 interfaces using the same IP address. You must re-configure to avoid
 this.</P>
<P>A mailing list message on the topic from Pluto developer Hugh
 Redelmeier:</P>
<PRE>| I'm trying to get freeswan working between two machine where one has a ppp
| interface.
| I've already suceeded with  two machines with ethernet ports but  the ppp
| interface is causing me problems.
|  basically when I run ipsec start  i get
| ipsec_setup: Starting FreeS/WAN IPsec 1.7...
| ipsec_setup: 003 IP interfaces ppp1 and ppp0 share address 192.168.0.10!
| ipsec_setup: 003 IP interfaces ppp1 and ppp2 share address 192.168.0.10!
| ipsec_setup: 003 IP interfaces ppp0 and ppp2 share address 192.168.0.10!
| ipsec_setup: 003 no public interfaces found
|
| followed by lots of cannot work out interface for connection messages
|
| now I can specify the interface in ipsec.conf to be ppp0 , but this does
| not affect the above behaviour. A quick look in server.c indicates that the
| interfaces value  is not used but some sort of raw detect happens.
|
| I guess I could prevent the formation of the extra ppp interfaces or
| allocate them different ip but I'd  rather not. if at all possible. Any
| suggestions please.

Pluto won't touch an interface that shares an IP address with another.
This will eventually change, but it probably won't happen soon.

For now, you will have to give the ppp1 and ppp2 different addresses.</PRE>
<H3><A name="kflags">ipsec_setup: Cannot adjust kernel flags</A></H3>
<P>A mailing list message form technical lead Henry Spencer:</P>
<PRE>&gt; When FreeS/WAN IPsec 1.7 is starting on my 2.0.38 Linux kernel the following
&gt; error message is generated:
&gt; ipsec_setup: Cannot adjust kernel flags, no /proc/sys/net/ipsec directory!
&gt; What is supposed to create this directory and how can I fix this problem?

I think that directory is a 2.2ism, although I'm not certain (I don't have
a 2.0.xx system handy any more for testing).  Without it, some of the
ipsec.conf config-setup flags won't work, but otherwise things should
function. </PRE>
<P>You also need to enable the<VAR> /proc</VAR> filesystem in your
 kernel configuration for these operations to work.</P>
<H3><A name="message_num">Message numbers (MI3, QR1, et cetera) in Pluto
 messages</A></H3>
<P>Pluto messages often indicate where Pluto is in the IKE protocols.
 The letters indicate<STRONG> M</STRONG>ain mode or<STRONG> Q</STRONG>
uick mode and<STRONG> I</STRONG>nitiator or<STRONG> R</STRONG>esponder.
 The numerals are message sequence numbers. For more detail, see our<A href="#sequence">
 IPsec section</A>.</P>
<H3><A name="conn_name">Connection names in Pluto error messages</A></H3>
<P>From Pluto programmer Hugh Redelmeier:</P>
<PRE>| Jan 17 16:21:10 remus Pluto[13631]: &quot;jumble&quot; #1: responding to Main Mode from Road Warrior 130.205.82.46
| Jan 17 16:21:11 remus Pluto[13631]: &quot;jumble&quot; #1: no suitable connection for peer @banshee.wittsend.com
| 
|     The connection &quot;jumble&quot; has nothing to do with the incoming
| connection requests, which were meant for the connection &quot;banshee&quot;.

You are right.  The message tells you which Connection Pluto is
currently using, which need not be the right one.  It need not be the
right one now for the negotiation to eventually succeed!  This is
described in ipsec_pluto(8) in the section &quot;Road Warrior Support&quot;.

There are two times when Pluto will consider switching Connections for
a state object.  Both are in response to receiving ID payloads (one in
Phase 1 / Main Mode and one in Phase 2 / Quick Mode).  The second is
not unique to Road Warriors.  In fact, neither is the first any more
(two connections for the same pair of hosts could differ in Phase 1 ID
payload; probably nobody else has tried this).</PRE>
<H3><A name="cantorient">Pluto: ... can't orient connection</A></H3>
<P>Older versions of FreeS/WAN used this message. The same error now
 gives the &quot;we have no ipsecN ...&quot; error described just below.</P>
<H3><A name="no.interface">... we have no ipsecN interface for either
 end of this connection</A></H3>
<P>Your tunnel has no IP address which matches the IP address of any of
 the available IPsec interfaces. Either you've misconfigured the
 connection, or you need to define an appropriate IPsec interface
 connection.<VAR> interfaces=%defaultroute</VAR> works in many cases.</P>
<P>A longer story: Pluto needs to know whether it is running on the
 machine which the connection description calls<VAR> left</VAR> or on<VAR>
 right</VAR>. It figures that out by:</P>
<UL>
<LI>looking at the interfaces given in<VAR> interfaces=</VAR> lines in
 the<VAR> config setup</VAR> section</LI>
<LI>discovering the IP addresses for those interfaces</LI>
<LI>searching for a match between those addresses and the ones given in<VAR>
 left=</VAR> or<VAR> right=</VAR> lines.</LI>
</UL>
<P>Normally a match is found. Then Pluto knows where it is and can set
 up other things (for example, if it is<VAR> left</VAR>) using
 parameters such as<VAR> leftsubnet</VAR> and<VAR> leftnexthop</VAR>,
 and sending its outgoing packets to<VAR> right</VAR>.</P>
<P>If no match is found, it emits the above error message.</P>
<H3><A name="noconn">Pluto: ... no connection is known</A></H3>
<P>This error message occurs when a remote system attempts to negotiate
 a connection and Pluto does not have a connection description that
 matches what the remote system has requested. The most common cause is
 a configuration error on one end or the other.</P>
<P>Parameters involved in this match are<VAR> left</VAR>,<VAR> right</VAR>
,<VAR> leftsubnet</VAR> and<VAR> rightsubnet</VAR>.</P>
<P><STRONG>The match must be exact</STRONG>. For example, if your left
 subnet is a.b.c.0/24 then neither a single machine in that net nor a
 smaller subnet such as a.b.c.64/26 will be considered a match.</P>
<P>The message can also occur when an appropriate description exists but
 Pluto has not loaded it. Use an<VAR> auto=add</VAR> statement in the
 connection description, or an<VAR> ipsec auto --add &lt;conn_name&gt;</VAR>
 command, to correct this.</P>
<P>An explanation from the Pluto developer:</P>
<PRE>| Jul 12 15:00:22 sohar58 Pluto[574]: &quot;corp_road&quot; #2: cannot respond to IPsec
| SA request because no connection is known for
| 216.112.83.112/32===216.112.83.112...216.67.25.118

This is the first message from the Pluto log showing a problem.  It
means that PGPnet is trying to negotiate a set of SAs with this
topology:

216.112.83.112/32===216.112.83.112...216.67.25.118
^^^^^^^^^^^^^^^^^   ^^^^^^^^^^^^^^   ^^^^^^^^^^^^^
client on our side  our host         PGPnet host, no client

None of the conns you showed look like this.

Use
        ipsec auto --status
to see a snapshot of what connections are in pluto, what
negotiations are going on, and what SAs are established.

The leftsubnet= (client) in your conn is 216.112.83.64/26.  It must
exactly match what pluto is looking for, and it does not.</PRE>
<H3><A name="nosuit">Pluto: ... no suitable connection ...</A></H3>
<P>This is similar to the<A href="#noconn"> no connection known</A>
 error, but occurs at a different point in Pluto processing.</P>
<P>Here is one of Claudia's messages explaining the problem:</P>
<PRE>You write,

&gt; What could be the reason of the following error? 
&gt; &quot;no suitable connection for peer '@xforce'&quot;

When a connection is initiated by the peer, Pluto must choose which entry in 
the conf file best matches the incoming connection. A preliminary choice is 
made on the basis of source and destination IPs, since that information is 
available at that time. 

A payload containing an ID arrives later in the negotiation. Based on this
id and the *id= parameters, Pluto refines its conn selection. ...

The message &quot;no suitable connection&quot; indicates that in this refining step,
Pluto does not find a connection that matches that ID.

Please see &quot;Selecting a connection when responding&quot; in man ipsec_pluto for
more details.</PRE>
<P>See also<A href="#conn_name"> Connection names in Pluto error
 messages</A>.</P>
<H3><A name="noconn.auth">Pluto: ... no connection has been authorized</A>
</H3>
<P>Here is one of Claudia's messages discussing this problem:</P>
<PRE>You write,

&gt;  May 22 10:46:31 debian Pluto[25834]: packet from x.y.z.p:10014: 
&gt;  initial Main Mode message from x.y.z.p:10014 
                            but no connection has been authorized

This error occurs early in the connection negotiation process,
at the first step of IKE negotiation (Main Mode), which is itself the 
first of two negotiation phases involved in creating an IPSec connection.

Here, Linux FreeS/WAN receives a packet from a potential peer, which 
requests that they begin discussing a connection.

The &quot;no connection has been authorized&quot; means that there is no connection 
description in Linux FreeS/WAN's internal database that can be used to 
link your ipsec interface with that peer.

&quot;But of course I configured that connection!&quot; 

It may be that the appropriate connection description exists in ipsec.conf 
but has not been added to the database with ipsec auto --add myconn or the 
auto=add method. Or, the connection description may be misconfigured.

The only parameters that are relevant in this decision are left= and right= .
Local and remote ports are also taken into account -- we see that the port 
is printed in the message above -- but there is no way to control these
in ipsec.conf.


Failure at &quot;no connection has been authorized&quot; is similar to the
&quot;no connection is known for...&quot; error in the FAQ, and the &quot;no suitable
connection&quot; error described in the snapshot's FAQ. In all three cases,
Linux FreeS/WAN is trying to match parameters received in the
negotiation with the connection description in the local config file.

As it receives more information, its matches take more parameters into 
account, and become more precise:  first the pair of potential peers,
then the peer IDs, then the endpoints (including any subnets).

The &quot;no suitable connection for peer *&quot; occurs toward the end of IKE 
(Main Mode) negotiation, when the IDs are matched.

&quot;no connection is known for a/b===c...d&quot; is seen at the beginning of IPSec 
(Quick Mode, phase 2) negotiation, when the connections are matched using
left, right, and any information about the subnets.</PRE>
<H3><A name="noDESsupport">Pluto: ... OAKLEY_DES_CBC is not supported.</A>
</H3>
<P>This message occurs when the other system attempts to negotiate a
 connection using<A href="#DES"> single DES</A>, which we do not support
 because it is<A href="#desnotsecure"> insecure</A>.</P>
<P>Our interoperation document has suggestions for<A href="interop.html#noDES">
 how to deal with</A> systems that attempt to use single DES.</P>
<H3><A name="notransform">Pluto: ... no acceptable transform</A></H3>
<P>This message means that the other gateway has made a proposal for
 connection parameters, but nothing they proposed is acceptable to
 Pluto. Possible causes include:</P>
<UL>
<LI>misconfiguration on either end</LI>
<LI>policy incompatibilities, for example we require encrypted
 connections but they are trying to create one with just authentication</LI>
<LI>interoperation problems, for example they offer only single DES and
 FreeS/WAN does not support that. See<A href="interop.html#interop.problem">
 discussion</A> in our interoperation document.</LI>
</UL>
<P>A more detailed explanation, from Pluto programmer Hugh Redelmeier:</P>
<PRE>Background:

When one IKE system (for example, Pluto) is negotiating with another
to create an SA, the Initiator proposes a bunch of choices and the
Responder replies with one that it has selected.

The structure of the choices is fairly complicated.  An SA payload
contains a list of lists of &quot;Proposals&quot;.  The outer list is a set of
choices: the selection must be from one element of this list.

Each of these elements is a list of Proposals.  A selection must be
made from each of the elements of the inner list.  In other words,
*all* of them apply (that is how, for example, both AH and ESP can
apply at once).

Within each of these Proposals is a list of Transforms.  For each
Proposal selected, one Transform must be selected (in other words,
each Proposal provides a choice of Transforms).

Each Transform is made up of a list of Attributes describing, well,
attributes.  Such as lifetime of the SA.  Such as algorithm to be
used.  All the Attributes apply to a Transform.

You will have noticed a pattern here: layers alternate between being
disjunctions (&quot;or&quot;) and conjunctions (&quot;and&quot;).

For Phase 1 / Main Mode (negotiating an ISAKMP SA), this structure is
cut back.  There must be exactly one Proposal.  So this degenerates to
a list of Transforms, one of which must be chosen.

In your case, no proposal was considered acceptable to Pluto (the
Responder).  So negotiation ceased.  Pluto logs the reason it rejects
each Transform.  So look back in the log to see what is going wrong.</PRE>
<H3><A name="rsasigkey">rsasigkey dumps core</A></H3>
 A comment on this error from Henry:
<PRE>On Fri, 29 Jun 2001, Rodrigo Gruppelli wrote:
&gt; ...Well, it seem that there's
&gt; another problem with it. When I try to generate a pair of RSA keys,
&gt; rsasigkey cores dump...

*That* is a neon sign flashing &quot;GMP LIBRARY IS BROKEN&quot;.  Rsasigkey calls
GMP a lot, and our own library a little bit, and that's very nearly all it
does.  Barring bugs in its code or our library -- which have happened, but
not very often -- a problem in rsasigkey is a problem in GMP.</PRE>
<P>See the next question for how to deal with GMP errors.</P>
<H3><A name="sig4">!Pluto failure!: ... exited with ... signal 4</A></H3>
<P>Pluto has died. Signal 4 is SIGILL, illegal instruction.</P>
<P>The most likely cause is that your<A href="#GMP"> GMP</A> (GNU
 multi-precision) library is compiled for a different processor than
 what you are running on. Pluto uses that library for its public key
 calculations.</P>
<P>Try getting the GMP sources and recompile for your processor type.
 Most Linux distributions will include this source, or you can download
 it from the<A href="http://www.swox.com/gmp/"> GMP home page</A>.</P>
<H3><A name="econnrefused">ECONNREFUSED error message</A></H3>
<P>From John Denker, on the mailing list:</P>
<PRE>1)  The log message
  some IKE message we sent has been rejected with 
  ECONNREFUSED (kernel supplied no details)
is much more suitable than the previous version.  Thanks.

2) Minor suggestion for further improvement: it might be worth mentioning
that the command
  tcpdump -i eth1 icmp[0] != 8 and icmp[0] != 0
is useful for tracking down the details in question.  We shouldn't expect
all IPsec users to figure that out on their own.  The log message might
even provide a hint as to where to look in the docs.</PRE>
<P>Reply From Pluto developer Hugh Redelmeier</P>
<PRE>Good idea.

I've added a bit pluto(8)'s BUGS section along these lines.
I didn't have the heart to lengthen this message.</PRE>
<H3><A name="no_eroute">klips_debug: ... no eroute!</A></H3>
<P>This message means<A href="#KLIPS"> KLIPS</A> has received a packet
 for which no IPsec tunnel has been defined.</P>
<P>Here is a more detailed duscussion from the team's tech support
 person Claudia Schmeing, responding to a query on the mailing list:</P>
<PRE>&gt; Why ipsec reports no eroute! ???? IP Masq... is disabled.

In general, more information is required so that people on the list may
give you informed input. See doc/prob.report.</PRE>
<P>The document she refers to has since been replaced by a<A href="#prob.report">
 section</A> of the troubleshooting document.</P>
<PRE>However, I can make some general comments on this type of error.

This error usually looks something like this (clipped from an archived
message):

&gt; ttl:64 proto:1 chk:45459 saddr:192.168.1.2 daddr:192.168.100.1
&gt; ... klips_debug:ipsec_findroute: 192.168.1.2-&gt;192.168.100.1
&gt; ... klips_debug:rj_match: * See if we match exactly as a host destination
&gt; ... klips_debug:rj_match: ** try to match a leaf, t=0xc1a260b0
&gt; ... klips_debug:rj_match: *** start searching up the tree, t=0xc1a260b0
&gt; ... klips_debug:rj_match: **** t=0xc1a260c8
&gt; ... klips_debug:rj_match: **** t=0xc1fe5960
&gt; ... klips_debug:rj_match: ***** not found.
&gt; ... klips_debug:ipsec_tunnel_start_xmit: Original head/tailroom: 2, 28
&gt; ... klips_debug:ipsec_tunnel_start_xmit: no eroute!: ts=47.3030, dropping.


What does this mean?
- --------------------

&quot;eroute&quot; stands for &quot;extended route&quot;, and is a special type of route 
internal to Linux FreeS/WAN. For more information about this type of route, 
see the section of man ipsec_auto on ipsec auto --route.

&quot;no eroute!&quot; here means, roughly, that Linux FreeS/WAN cannot find an 
appropriate tunnel that should have delivered this packet. Linux 
FreeS/WAN therefore drops the packet, with the message &quot;no eroute! ...
dropping&quot;, on the assumption that this packet is not a legitimate 
transmission through a properly constructed tunnel.


How does this situation come about?
- -----------------------------------

Linux FreeS/WAN has a number of connection descriptions defined in 
ipsec.conf. These must be successfully brought &quot;up&quot; to form actual tunnels.
(see doc/setup.html's step 15, man ipsec.conf and man ipsec_auto 
for details).

Such connections are often specific to the endpoints' IPs. However, in 
some cases they may be more general, for example in the case of 
Road Warriors where left or right is the special value %any.

When Linux FreeS/WAN receives a packet, it verifies that the packet has
come through a legitimate channel, by checking that there is an
appropriate tunnel through which this packet might legitimately have
arrived. This is the process we see above.

First, it checks for an eroute that exactly matches the packet. In the 
example above, we see it checking for a route that begins at 192.168.1.2
and ends at 192.168.100.1. This search favours the most specific match that
would apply to the route between these IPs. So, if there is a connection 
description exactly matching these IPs, the search will end there. If not, 
the code will search for a more general description matching the IPs.
If there is no match, either specific or general, the packet will be
dropped, as we see, above.

Unless you are working with Road Warriors, only the first, specific part 
of the matching process is likely to be relevant to you.


&quot;But I defined the tunnel, and it came up, why do I have this error?&quot;
- ---------------------------------------------------------------------

One of the most common causes of this error is failure to specify enough
connection descriptions to cover all needed tunnels between any two 
gateways and their respective subnets. As you have noticed, troubleshooting
this error may be complicated by the use of IP Masq. However, this error is
not limited to cases where IP Masq is used. 

See doc/configuration.html#multitunnel for a detailed example of the 
solution to this type of problem.</PRE>
<P>The documentation section she refers to is now<A href="#multitunnel">
 here</A>.</P>
<H3><A name="SAused">... trouble writing to /dev/ipsec ... SA already in
 use</A></H3>
<P>This error message occurs when two manual connections are set up with
 the same SPI value.</P>
<P>See the FAQ for<A href="#spi_error"> One manual connection works, but
 second one fails</A>.</P>
<H3><A name="ignore">... ignoring ... payload</A></H3>
<P>This message is harmless. The IKE protocol provides for a number of
 optional messages types:</P>
<UL>
<LI>delete SA</LI>
<LI>initial contact</LI>
<LI>vendor ID</LI>
<LI>...</LI>
</UL>
<P>An implementation is never required to send these, but they are
 allowed to. The receiver is not required to do anything with them.
 FreeS/WAN ignores them, but notifies you via the logs.</P>
<P>For the &quot;ignoring delete SA Payload&quot; message, see also our discussion
 of cleaning up<A href="#deadtunnel"> dead tunnels</A>.</P>
<H3><A name="unknown_rightcert">unknown parameter name &quot;rightcert&quot;</A></H3>
<P>This message can appear when you've upgraded an X.509-enabled Linux
 FreeS/WAN with a vanilla Linux FreeS/WAN. To use your X.509 configs you
 will need to overwrite the new install with<A HREF="http://www.freeswan.ca">
 Super FreeS/WAN</A>, or add the<A HREF="http://www.strongsec.ca/freeswan">
 X.509 patch</A> by hand.</P>
<H2><A name="spam">Why don't you restrict the mailing lists to reduce
 spam?</A></H2>
<P>As a matter of policy, some of our<A href="mail.html"> mailing lists</A>
 need to be open to non-subscribers. Project management feel strongly
 that maintaining this openness is more important than blocking spam.</P>
<UL>
<LI>Users should be able to get help or report bugs without subscribing.</LI>
<LI>Even a user who is subscribed may not have access to his or her
 subscribed account when he or she needs help, miles from home base in
 the middle of setting up a client's gateway.</LI>
<LI>There is arguably a legal requirement for this policy. A US resident
 or citizen could be charged under munitions export laws for providing
 technical assistance to a foreign cryptographic project. Such a charge
 would be more easily defended if the discussion takes place in public,
 on an open list.</LI>
</UL>
<P>This has been discussed several times at some length on the list. See
 the<A href="#archive"> list archives</A>. Bringing the topic up again
 is unlikely to be useful. Please don't. Or at the very least, please
 don't without reading the archives and being certain that whatever you
 are about to suggest has not yet been discussed.</P>
<P>Project technical lead Henry Spencer summarised one discussion:</P>
<BLOCKQUOTE> For the third and last time: this list *will* *not* do
 address-based filtering. This is a policy decision, not an
 implementation problem. The decision is final, and is not open to
 discussion. This needs to be communicated better to people, and steps
 are being taken to do that.</BLOCKQUOTE>
<P>Adding this FAQ section is one of the steps he refers to.</P>
<P>You have various options other than just putting up with the spam,
 filtering it yourself, or unsubscribing:</P>
<UL>
<LI>subscribe only to one or both of our lists with restricted posting
 rules:
<UL>
<LI><A href="mailto:briefs@lists.freeswan.org?body=subscribe">briefs</A>
, weekly list summaries</LI>
<LI><A href="mailto:announce@lists.freeswan.org?body=subscribe">announce</A>
, project-related announcements</LI>
</UL>
</LI>
<LI>read the other lists via the<A href="#archive"> archives</A></LI>
</UL>
<P>A number of tools are available to filter mail.</P>
<UL>
<LI>Many mail readers include some filtering capability.</LI>
<LI>Many Linux distributions include<A href="http://www.procmail.org/">
 procmail(8)</A> for server-side filtering.</LI>
<LI>The<A href="http://www.spambouncer.org/"> Spam Bouncer</A> is a set
 of procmail(8) filters designed to combat spam.</LI>
<LI>Roaring Penguin have a<A href="http://www.roaringpenguin.com/mimedefang/">
 MIME defanger</A> that removes potentially dangerous attachments.</LI>
</UL>
<P>If you use your ISP's mail server rather than running your own,
 consider suggesting to the ISP that they tag suspected spam as<A href="http://www.msen.com/1997/spam.html#SUSPECTED">
 this ISP</A> does. They could just refuse mail from dubious sources,
 but that is tricky and runs some risk of losing valuable mail or
 senselessly annoying senders and their admins. However, they can safely
 tag and deliver dubious mail. The tags can greatly assist your
 filtering.</P>
<P>For information on tracking down spammers, see these<A href="http://www.rahul.net/falk/#howtos">
 HowTos</A>, or the<A href="http://www.sputum.com/index2.html"> Sputum</A>
 site. Sputum have a Linux anti-spam screensaver available for download.</P>
<P>Here is a more detailed message from Henry:</P>
<PRE>On Mon, 15 Jan 2001, Jay Vaughan wrote:
&gt; I know I'm flogging a dead horse here, but I'm curious as to the reasons for
&gt; an aversion for a subscriber-only mailing list?

Once again:  for legal reasons, it is important that discussions of these
things be held in a public place -- the list -- and we do not want to
force people to subscribe to the list just to ask one question, because
that may be more than merely inconvenient for them.  There are also real
difficulties with people who are temporarily forced to use alternate
addresses; that is precisely the time when they may be most in need of
help, yet a subscribers-only policy shuts them out.

These issues do not apply to most mailing lists, but for a list that is
(necessarily) the primary user support route for a crypto package, they
are very important.  This is *not* an ordinary mailing list; it has to
function under awkward constraints that make various simplistic solutions
inapplicable or undesirable. 

&gt; We're *ALL* sick of hearing about list management problems, not just you
&gt; old-timers, so why don't you DO SOMETHING EFFECTIVE ABOUT IT...

Because it's a lot harder than it looks, and many existing &quot;solutions&quot;
have problems when examined closely.

&gt; A suggestion for you, based on 10 years of experience with management of my
&gt; own mailing lists would be to use mailman, which includes pretty much every
&gt; feature under the sun that you guys need and want, plus some.  The URL for
&gt; mailman...

I assure you, we're aware of mailman.  Along with a whole bunch of others,
including some you almost certainly have never heard of (I hadn't!).

&gt; As for the argument that the list shouldn't be configured to enforce
&gt; subscription - I contend that it *SHOULD* AT LEAST require manual address
&gt; verification in order for posts to be redirected.

You do realize, I hope, that interposing such a manual step might cause
your government to decide that this is not truly a public forum, and thus
you could go to jail if you don't get approval from them before mailing to
it?  If you think this sounds irrational, your government is noted for
making irrational decisions in this area; we can't assume that they will
suddenly start being sensible.  See above about awkward constraints.  You
may be willing to take the risk, but we can't, in good conscience, insist
that all users with problems do so. 

                                                          Henry Spencer
                                                       henry@spsystems.net</PRE>
<P>and a message on the topic from project leader John Gilmore:</P>
<PRE>Subject: Re: The linux-ipsec list's topic
   Date: Sat, 30 Dec 2000
   From: John Gilmore &lt;gnu@toad.com&gt;

I'll post this single message, once only, in this discussion, and then
not burden the list with any further off-topic messages.  I encourage
everyone on the list to restrain themself from posting ANY off-topic
messages to the linux-ipsec list.

The topic of the linux-ipsec mailing list is the FreeS/WAN software.

I frequently see &quot;discussions about spam on a list&quot; overwhelm the
volume of &quot;actual spam&quot; on a list. BOTH kinds of messages are
off-topic messages.  Twenty anti-spam messages take just as long to
detect and discard as twenty spam messages.

The Linux-ipsec list encourages on-topic messages from people who have
not joined the list itself.  We will not censor messages to the list
based on where they originate, or what return address they contain.
In other words, non-subscribers ARE allowed to post, and this will not
change.  My own valid contributions have been rejected out-of-hand by
too many other mailing lists for me to want to impose that censorship
on anybody else's contributions.  And every day I see the damage that
anti-spam zeal is causing in many other ways; that zeal is far more
damaging to the culture of the Internet than the nuisance of spam.

In general, it is the responsibility of recipients to filter,
prioritize, or otherwise manage the handling of email that comes to
them.  It is not the responsibility of the rest of the Internet
community to refrain from sending messages to recipients that they
might not want to see.  If your software infrastructure for managing
your incoming email is insufficient, then improve it.  If you think
the signal-to-noise ratio on linux-ipsec is too poor, then please
unsubscribe.  But don't further increase the noise by posting to the
linux-ipsec list about those topics.

        John Gilmore
        founder &amp; sponsor, FreeS/WAN project</PRE>
<HR>
<H1><A name="manpages">FreeS/WAN manual pages</A></H1>
<P>The various components of Linux FreeS/WAN are of course documented in
 standard Unix manual pages, accessible via the man(1) command.</P>
<P>Links here take you to an HTML version of the man pages.</P>
<H2><A name="man.file">Files</A></H2>
<DL>
<DT><A href="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</A></DT>
<DD>IPsec configuration and connections</DD>
<DT><A href="manpage.d/ipsec.secrets.5.html">ipsec.secrets(5)</A></DT>
<DD>secrets for IKE authentication, either pre-shared keys or RSA
 private keys</DD>
</DL>
<P>These files are also discussed in the<A href="config.html">
 configuration</A> section.</P>
<H2><A name="man.command">Commands</A></H2>
<P>Many users will never give most of the FreeS/WAN commands directly.
 Configure the files listed above correctly and everything should be
 automatic.</P>
<P>The exceptions are commands for mainpulating the<A href="#RSA"> RSA</A>
 keys used in Pluto authentication:</P>
<DL>
<DT><A href="manpage.d/ipsec_rsasigkey.8.html">ipsec_rsasigkey(8)</A></DT>
<DD>generate keys</DD>
<DT><A href="manpage.d/ipsec_newhostkey.8.html">ipsec_newhostkey(8)</A></DT>
<DD>generate keys in a convenient format</DD>
<DT><A href="manpage.d/ipsec_showhostkey.8.html">ipsec_showhostkey(8)</A>
</DT>
<DD>extract<A href="#RSA"> RSA</A> keys from<A href="manpage.d/ipsec.secrets.5.html">
 ipsec.secrets(5)</A> (or optionally, another file) and format them for
 insertion in<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf(5)</A> or
 in DNS records</DD>
</DL>
<P>Note that:</P>
<UL>
<LI>These keys are for<STRONG> authentication only</STRONG>. They are<STRONG>
 not secure for encryption</STRONG>.</LI>
<LI>The utility uses random(4) as a source of<A href="#random"> random
 numbers</A>. This may block for some time if there is not enough
 activity on the machine to provide the required entropy. You may want
 to give it some bogus activity such as random mouse movements or some
 command such as<NOBR> <TT>du /usr &gt; /dev/null &amp;</TT>.</LI>
</UL>
<P>The following commands are fairly likely to be used, if only for
 testing and status checks:</P>
<DL>
<DT><A href="manpage.d/ipsec.8.html">ipsec(8)</A></DT>
<DD>invoke IPsec utilities</DD>
<DT><A href="manpage.d/ipsec_setup.8.html">ipsec_setup(8)</A></DT>
<DD>control IPsec subsystem</DD>
<DT><A href="manpage.d/ipsec_auto.8.html">ipsec_auto(8)</A></DT>
<DD>control automatically-keyed IPsec connections</DD>
<DT><A href="manpage.d/ipsec_manual.8.html">ipsec_manual(8)</A></DT>
<DD>take manually-keyed IPsec connections up and down</DD>
<DT><A href="manpage.d/ipsec_ranbits.8.html">ipsec_ranbits(8)</A></DT>
<DD>generate random bits in ASCII form</DD>
<DT><A href="manpage.d/ipsec_look.8.html">ipsec_look(8)</A></DT>
<DD>show minimal debugging information</DD>
<DT><A href="manpage.d/ipsec_barf.8.html">ipsec_barf(8)</A></DT>
<DD>spew out collected IPsec debugging information</DD>
</DL>
<P>The lower-level utilities listed below are normally invoked via
 scripts listed above, but they can also be used directly when required.</P>
<DL>
<DT><A href="manpage.d/ipsec_eroute.8.html">ipsec_eroute(8)</A></DT>
<DD>manipulate IPsec extended routing tables</DD>
<DT><A href="manpage.d/ipsec_klipsdebug.8.html">ipsec_klipsdebug(8)</A></DT>
<DD>set Klips (kernel IPsec support) debug features and level</DD>
<DT><A href="manpage.d/ipsec_pluto.8.html">ipsec_pluto(8)</A></DT>
<DD>IPsec IKE keying daemon</DD>
<DT><A href="manpage.d/ipsec_spi.8.html">ipsec_spi(8)</A></DT>
<DD>manage IPsec Security Associations</DD>
<DT><A href="manpage.d/ipsec_spigrp.8.html">ipsec_spigrp(8)</A></DT>
<DD>group/ungroup IPsec Security Associations</DD>
<DT><A href="manpage.d/ipsec_tncfg.8.html">ipsec_tncfg(8)</A></DT>
<DD>associate IPsec virtual interface with real interface</DD>
<DT><A href="manpage.d/ipsec_whack.8.html">ipsec_whack(8)</A></DT>
<DD>control interface for IPsec keying daemon</DD>
</DL>
<H2><A name="man.lib">Library routines</A></H2>
<DL>
<DT><A href="manpage.d/ipsec_atoaddr.3.html">ipsec_atoaddr(3)</A></DT>
<DT><A href="manpage.d/ipsec_addrtoa.3.html">ipsec_addrtoa(3)</A></DT>
<DD>convert Internet addresses to and from ASCII</DD>
<DT><A href="manpage.d/ipsec_atosubnet.3.html">ipsec_atosubnet(3)</A></DT>
<DT><A href="manpage.d/ipsec_subnettoa.3.html">ipsec_subnettoa(3)</A></DT>
<DD>convert subnet/mask ASCII form to and from addresses</DD>
<DT><A href="manpage.d/ipsec_atoasr.3.html">ipsec_atoasr(3)</A></DT>
<DD>convert ASCII to Internet address, subnet, or range</DD>
<DT><A href="manpage.d/ipsec_rangetoa.3.html">ipsec_rangetoa(3)</A></DT>
<DD>convert Internet address range to ASCII</DD>
<DT>ipsec_atodata(3)</DT>
<DT><A href="manpage.d/ipsec_datatoa.3.html">ipsec_datatoa(3)</A></DT>
<DD>convert binary data from and to ASCII formats</DD>
<DT><A href="manpage.d/ipsec_atosa.3.html">ipsec_atosa(3)</A></DT>
<DT><A href="manpage.d/ipsec_satoa.3.html">ipsec_satoa(3)</A></DT>
<DD>convert IPsec Security Association IDs to and from ASCII</DD>
<DT><A href="manpage.d/ipsec_atoul.3.html">ipsec_atoul(3)</A></DT>
<DT><A href="manpage.d/ipsec_ultoa.3.html">ipsec_ultoa(3)</A></DT>
<DD>convert unsigned-long numbers to and from ASCII</DD>
<DT><A href="manpage.d/ipsec_goodmask.3.html">ipsec_goodmask(3)</A></DT>
<DD>is this Internet subnet mask a valid one?</DD>
<DT><A href="manpage.d/ipsec_masktobits.3.html">ipsec_masktobits(3)</A></DT>
<DD>convert Internet subnet mask to bit count</DD>
<DT><A href="manpage.d/ipsec_bitstomask.3.html">ipsec_bitstomask(3)</A></DT>
<DD>convert bit count to Internet subnet mask</DD>
<DT><A href="manpage.d/ipsec_optionsfrom.3.html">ipsec_optionsfrom(3)</A>
</DT>
<DD>read additional ``command-line'' options from file</DD>
<DT><A href="manpage.d/ipsec_subnetof.3.html">ipsec_subnetof(3)</A></DT>
<DD>given Internet address and subnet mask, return subnet number</DD>
<DT><A href="manpage.d/ipsec_hostof.3.html">ipsec_hostof(3)</A></DT>
<DD>given Internet address and subnet mask, return host part</DD>
<DT><A href="manpage.d/ipsec_broadcastof.3.html">ipsec_broadcastof(3)</A>
</DT>
<DD>given Internet address and subnet mask, return broadcast address</DD>
</DL>
<HR>
<H1><A name="firewall">FreeS/WAN and firewalls</A></H1>
<P>FreeS/WAN, or other IPsec implementations, frequently run on gateway
 machines, the same machines running firewall or packet filtering code.
 This document discusses the relation between the two.</P>
<P>The firewall code in 2.4 and later kernels is called Netfilter. The
 user-space utility to manage a firewall is iptables(8). See the<A href="http://netfilter.samba.org">
 netfilter/iptables web site</A> for details.</P>
<H2><A name="filters">Filtering rules for IPsec packets</A></H2>
<P>The basic constraint is that<STRONG> an IPsec gateway must have
 packet filters that allow IPsec packets</STRONG>, at least when talking
 to other IPsec gateways:</P>
<UL>
<LI>UDP port 500 for<A href="#IKE"> IKE</A> negotiations</LI>
<LI>protocol 50 if you use<A href="#ESP"> ESP</A> encryption and/or
 authentication (the typical case)</LI>
<LI>protocol 51 if you use<A href="#AH"> AH</A> packet-level
 authentication</LI>
</UL>
<P>Your gateway and the other IPsec gateways it communicates with must
 be able to exchange these packets for IPsec to work. Firewall rules
 must allow UDP 500 and at least one of<A href="#AH"> AH</A> or<A href="#ESP">
 ESP</A> on the interface that communicates with the other gateway.</P>
<P>For nearly all FreeS/WAN applications, you must allow UDP port 500
 and the ESP protocol.</P>
<P>There are two ways to set this up:</P>
<DL>
<DT>easier but less flexible</DT>
<DD>Just set up your firewall scripts at boot time to allow IPsec
 packets to and from your gateway. Let FreeS/WAN reject any bogus
 packets.</DD>
<DT>more work, giving you more precise control</DT>
<DD>Have the<A href="manpage.d/ipsec_pluto.8.html"> ipsec_pluto(8)</A>
 daemon call scripts to adjust firewall rules dynamically as required.
 This is done by naming the scripts in the<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A> variables<VAR> prepluto=</VAR>,<VAR> postpluto=</VAR>
,<VAR> leftupdown=</VAR> and<VAR> rightupdown=</VAR>.</DD>
</DL>
<P>Both methods are described in more detail below.</P>
<H2><A name="examplefw">Firewall configuration at boot</A></H2>
<P>It is possible to set up both firewalling and IPsec with appropriate
 scripts at boot and then not use<VAR> leftupdown=</VAR> and<VAR>
 rightupdown=</VAR>, or use them only for simple up and down operations.</P>
<P>Basically, the technique is</P>
<UL>
<LI>allow IPsec packets (typically, IKE on UDP port 500 plus ESP,
 protocol 50)
<UL>
<LI>incoming, if the destination address is your gateway (and
 optionally, only from known senders)</LI>
<LI>outgoing, with the from address of your gateway (and optionally,
 only to known receivers)</LI>
</UL>
</LI>
<LI>let<A href="#Pluto"> Pluto</A> deal with IKE</LI>
<LI>let<A href="#KLIPS"> KLIPS</A> deal with ESP</LI>
</UL>
<P>Since Pluto authenticates its partners during the negotiation, and
 KLIPS drops packets for which no tunnel has been negotiated, this may
 be all you need.</P>
<H3><A name="simple.rules">A simple set of rules</A></H3>
<P>In simple cases, you need only a few rules, as in this example:</P>
<PRE># allow IPsec
#
# IKE negotiations
iptables -I INPUT  -p udp --sport 500 --dport 500 -j ACCEPT
iptables -I OUTPUT -p udp --sport 500 --dport 500 -j ACCEPT
# ESP encryption and authentication
iptables -I INPUT  -p 50 -j ACCEPT
iptables -I OUTPUT -p 50 -j ACCEPT
</PRE>
<P>This should be all you need to allow IPsec through<VAR> lokkit</VAR>,
 which ships with Red Hat 9, on its medium security setting. Once you've
 tweaked to your satisfaction, save your active rule set with:</P>
<PRE>service iptables save</PRE>
<H3><A name="complex.rules">Other rules</A></H3>
 You can add additional rules, or modify existing ones, to work with
 IPsec and with your network and policies. We give a some examples in
 this section.
<P>However, while it is certainly possible to create an elaborate set of
 rules yourself (please let us know via the<A href="mail.html"> mailing
 list</A> if you do), it may be both easier and more secure to use a set
 which has already been published and tested.</P>
<P>The published rule sets we know of are described in the<A href="#rules.pub">
 next section</A>.</P>
<H4><A NAME="7_2_2_1">Adding additional rules</A></H4>
 If necessary, you can add additional rules to:
<DL>
<DT>reject IPsec packets that are not to or from known gateways</DT>
<DD>This possibility is discussed in more detail<A href="#unknowngate">
 later</A></DD>
<DT>allow systems behind your gateway to build IPsec tunnels that pass
 through the gateway</DT>
<DD>This possibility is discussed in more detail<A href="#through">
 later</A></DD>
<DT>filter incoming packets emerging from KLIPS.</DT>
<DD>Firewall rules can recognise packets emerging from IPsec. They are
 marked as arriving on an interface such as<VAR> ipsec0</VAR>, rather
 than<VAR> eth0</VAR>,<VAR> ppp0</VAR> or whatever.</DD>
</DL>
<P>It is therefore reasonably straightforward to filter these packets in
 whatever way suits your situation.</P>
<H4><A NAME="7_2_2_2">Modifying existing rules</A></H4>
<P>In some cases rules that work fine before you add IPsec may require
 modification to work with IPsec.</P>
<P>This is especially likely for rules that deal with interfaces on the
 Internet side of your system. IPsec adds a new interface; often the
 rules must change to take account of that.</P>
<P>For example, consider the rules given in<A href="http://www.netfilter.org/documentation/HOWTO//packet-filtering-HOWTO-5.html">
 this section</A> of the Netfilter documentation:</P>
<PRE>Most people just have a single PPP connection to the Internet, and don't
want anyone coming back into their network, or the firewall:

    ## Insert connection-tracking modules (not needed if built into kernel).
    # insmod ip_conntrack
    # insmod ip_conntrack_ftp

    ## Create chain which blocks new connections, except if coming from inside.
    # iptables -N block
    # iptables -A block -m state --state ESTABLISHED,RELATED -j ACCEPT
    # iptables -A block -m state --state NEW -i ! ppp0 -j ACCEPT
    # iptables -A block -j DROP

    ## Jump to that chain from INPUT and FORWARD chains.
    # iptables -A INPUT -j block
    # iptables -A FORWARD -j block</PRE>
<P>On an IPsec gateway, those rules may need to be modified. The above
 allows new connections from<EM> anywhere except ppp0</EM>. That means
 new connections from ipsec0 are allowed.</P>
<P>Do you want to allow anyone who can establish an IPsec connection to
 your gateway to initiate TCP connections to any service on your
 network? Almost certainly not if you are using opportunistic
 encryption. Quite possibly not even if you have only explicitly
 configured connections.</P>
<P>To disallow incoming connections from ipsec0, change the middle
 section above to:</P>
<PRE>    ## Create chain which blocks new connections, except if coming from inside.
    # iptables -N block
    # iptables -A block -m state --state ESTABLISHED,RELATED -j ACCEPT
    # iptables -A block -m state --state NEW -i ppp+ -j DROP
    # iptables -A block -m state --state NEW -i ipsec+ -j DROP
    # iptables -A block -m state --state NEW -i -j ACCEPT
    # iptables -A block -j DROP</PRE>
<P>The original rules accepted NEW connections from anywhere except
 ppp0. This version drops NEW connections from any PPP interface (ppp+)
 and from any ipsec interface (ipsec+), then accepts the survivors.</P>
<P>Of course, these are only examples. You will need to adapt them to
 your own situation.</P>
<H3><A name="rules.pub">Published rule sets</A></H3>
<P>Several sets of firewall rules that work with FreeS/WAN are
 available.</P>
<H4><A name="Ranch.trinity">Scripts based on Ranch's work</A></H4>
<P>One user, Rob Hutton, posted his boot time scripts to the mailing
 list, and we included them in previous versions of this documentation.
 They are still available from our<A href="http://www.freeswan.org/freeswan_trees/freeswan-1.5/doc/firewall.html#examplefw">
 web site</A>. However, they were for an earlier FreeS/WAN version so we
 no longer recommend them. Also, they had some bugs. See this<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/04/msg00316.html">
 message</A>.</P>
<P>Those scripts were based on David Ranch's scripts for his &quot;Trinity
 OS&quot; for setting up a secure Linux. Check his<A href="http://www.ecst.csuchico.edu/~dranch/LINUX/index-linux.html">
 home page</A> for the latest version and for information on his<A href="#ranch">
 book</A> on securing Linux. If you are going to base your firewalling
 on Ranch's scripts, we recommend using his latest version, and sending
 him any IPsec modifications you make for incorporation into later
 versions.</P>
<H4><A name="seawall">The Seattle firewall</A></H4>
<P>We have had several mailing lists reports of good results using
 FreeS/WAN with Seawall (the Seattle Firewall). See that project's<A href="http://seawall.sourceforge.net/">
 home page</A> on Sourceforge.</P>
<H4><A name="rcf">The RCF scripts</A></H4>
<P>Another set of firewall scripts with IPsec support are the RCF or
 rc.firewall scripts. See their<A href="http://jsmoriss.mvlan.net/linux/rcf.html">
 home page</A>.</P>
<H4><A name="asgard">Asgard scripts</A></H4>
<P><A href="http://heimdall.asgardsrealm.net/linux/firewall/">Asgard's
 Realm</A> has set of firewall scripts with FreeS/WAN support, for 2.4
 kernels and iptables.</P>
<H4><A name="user.scripts">User scripts from the mailing list</A></H4>
<P>One user gave considerable detail on his scripts, including
 supporting<A href="#IPX"> IPX</A> through the tunnel. His message was
 too long to conveniently be quoted here, so I've put it in a<A href="user_examples.html">
 separate file</A>.</P>
<H2><A name="updown">Calling firewall scripts, named in ipsec.conf(5)</A>
</H2>
<P>The<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf(5)</A>
 configuration file has three pairs of parameters used to specify an
 interface between FreeS/WAN and firewalling code.</P>
<P>Note that using these is not required if you have a static firewall
 setup. In that case, you just set your firewall up at boot time (in a
 way that permits the IPsec connections you want) and do not change it
 thereafter. Omit all the FreeS/WAN firewall parameters and FreeS/WAN
 will not attempt to adjust firewall rules at all. See<A href="#examplefw">
 above</A> for some information on appropriate scripts.</P>
<P>However, if you want your firewall rules to change when IPsec
 connections change, then you need to use these parameters.</P>
<H3><A name="pre_post">Scripts called at IPsec start and stop</A></H3>
<P>One pair of parmeters are set in the<VAR> config setup</VAR> section
 of the<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf(5)</A> file and
 affect all connections:</P>
<DL>
<DT>prepluto=</DT>
<DD>script to be called before<A href="manpage.d/ipsec_pluto.8.html">
 pluto(8)</A> IKE daemon is started.</DD>
<DT>postpluto=</DT>
<DD>script to be called after<A href="manpage.d/ipsec_pluto.8.html">
 pluto(8)</A> IKE daemon is stopped.</DD>
</DL>
 These parameters allow you to change firewall parameters whenever IPsec
 is started or stopped.
<P>They can also be used in other ways. For example, you might have<VAR>
 prepluto</VAR> add a module to your kernel for the secure network
 interface or make a dialup connection, and then have<VAR> postpluto</VAR>
 remove the module or take the connection down.</P>
<H3><A name="up_down">Scripts called at connection up and down</A></H3>
<P>The other parameters are set in connection descriptions. They can be
 set in individual connection descriptions, and could even call
 different scripts for each connection for maximum flexibility. In most
 applications, however, it makes sense to use only one script and to
 call it from<VAR> conn %default</VAR> section so that it applies to all
 connections.</P>
<P>You can:</P>
<DL>
<DT><STRONG>either</STRONG></DT>
<DD>set<VAR> leftfirewall=yes</VAR> or<VAR> rightfirewall=yes</VAR> to
 use our supplied default script</DD>
<DT><STRONG>or</STRONG></DT>
<DD>assign a name in a<VAR> leftupdown=</VAR> or<VAR> rightupdown=</VAR>
 line to use your own script</DD>
</DL>
<P>Note that<STRONG> only one of these should be used</STRONG>. You
 cannot sensibly use both. Since<STRONG> our default script is obsolete</STRONG>
 (designed for firewalls using<VAR> ipfwadm(8)</VAR> on 2.0 kernels),
 most users who need this service will<STRONG> need to write a custom
 script</STRONG>.</P>
<H4><A name="fw.default">The default script</A></H4>
<P>We supply a default script named<VAR> _updown</VAR>.</P>
<DL>
<DT>leftfirewall=</DT>
<DD></DD>
<DT>rightfirewall=</DT>
<DD>indicates that the gateway is doing firewalling and that<A href="manpage.d/ipsec_pluto.8.html">
 pluto(8)</A> should poke holes in the firewall as required.</DD>
</DL>
<P>Set these to<VAR> yes</VAR> and Pluto will call our default script<VAR>
 _updown</VAR> with appropriate arguments whenever it:</P>
<UL>
<LI>starts or stops IPsec services</LI>
<LI>brings a connection up or down</LI>
</UL>
<P>The supplied default<VAR> _updown</VAR> script is appropriate for
 simple cases using the<VAR> ipfwadm(8)</VAR> firewalling package.</P>
<H4><A name="userscript">User-written scripts</A></H4>
<P>You can also write your own script and have Pluto call it. Just put
 the script's name in one of these<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A> lines:</P>
<DL>
<DT>leftupdown=</DT>
<DD></DD>
<DT>rightupdown=</DT>
<DD>specifies a script to call instead of our default script<VAR>
 _updown</VAR>.</DD>
</DL>
<P>Your script should take the same arguments and use the same
 environment variables as<VAR> _updown</VAR>. See the &quot;updown command&quot;
 section of the<A href="manpage.d/ipsec_pluto.8.html"> ipsec_pluto(8)</A>
 man page for details.</P>
<P>Note that<STRONG> you should not modify our _updown script in place</STRONG>
. If you did that, then upgraded FreeS/WAN, the upgrade would install a
 new default script, overwriting your changes.</P>
<H3><A name="ipchains.script">Scripts for ipchains or iptables</A></H3>
<P>Our<VAR> _updown</VAR> is for firewalls using<VAR> ipfwadm(8)</VAR>,
 the firewall code for the 2.0 series of Linux kernels. If you are using
 the more recent packages<VAR> ipchains(8)</VAR> (for 2.2 kernels) or<VAR>
 iptables(8)</VAR> (2.4 kernels), then you must do one of:</P>
<UL>
<LI>use static firewall rules which are set up at boot time as described<A
href="#examplefw"> above</A> and do not need to be changed by Pluto</LI>
<LI>limit yourself to ipchains(8)'s ipfwadm(8) emulation mode in order
 to use our script</LI>
<LI>write your own script and call it with<VAR> leftupdown</VAR> and<VAR>
 rightupdown</VAR>.</LI>
</UL>
<P>You can write a script to do whatever you need with firewalling.
 Specify its name in a<VAR> [left|right]updown=</VAR> parameter in<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A> and Pluto will automatically call it for you.</P>
<P>The arguments Pluto passes such a script are the same ones it passes
 to our default _updown script, so the best way to build yours is to
 copy ours and modify the copy.</P>
<P>Note, however, that<STRONG> you should not modify our _updown script
 in place</STRONG>. If you did that, then upgraded FreeS/WAN, the
 upgrade would install a new default script, overwriting your changes.</P>
<H2><A name="NAT">A complication: IPsec vs. NAT</A></H2>
<P><A href="#NAT.gloss">Network Address Translation</A>, also known as
 IP masquerading, is a method of allocating IP addresses dynamically,
 typically in circumstances where the total number of machines which
 need to access the Internet exceeds the supply of IP addresses.</P>
<P>Any attempt to perform NAT operations on IPsec packets<EM> between
 the IPsec gateways</EM> creates a basic conflict:</P>
<UL>
<LI>IPsec wants to authenticate packets and ensure they are unaltered on
 a gateway-to-gateway basis</LI>
<LI>NAT rewrites packet headers as they go by</LI>
<LI>IPsec authentication fails if packets are rewritten anywhere between
 the IPsec gateways</LI>
</UL>
<P>For<A href="#AH"> AH</A>, which authenticates parts of the packet
 header including source and destination IP addresses, this is fatal. If
 NAT changes those fields, AH authentication fails.</P>
<P>For<A href="#IKE"> IKE</A> and<A href="#ESP"> ESP</A> it is not
 necessarily fatal, but is certainly an unwelcome complication.</P>
<H3><A name="nat_ok">NAT on or behind the IPsec gateway works</A></H3>
<P>This problem can be avoided by having the masquerading take place<EM>
 on or behind</EM> the IPsec gateway.</P>
<P>This can be done physically with two machines, one physically behind
 the other. A picture, using SG to indicate IPsec<STRONG> S</STRONG>
ecurity<STRONG> G</STRONG>ateways, is:</P>
<PRE>      clients --- NAT ----- SG ---------- SG
                  two machines</PRE>
<P>In this configuration, the actual client addresses need not be given
 in the<VAR> leftsubnet=</VAR> parameter of the FreeS/WAN connection
 description. The security gateway just delivers packets to the NAT box;
 it needs only that machine's address. What that machine does with them
 does not affect FreeS/WAN.</P>
<P>A more common setup has one machine performing both functions:</P>
<PRE>      clients ----- NAT/SG ---------------SG
                  one machine</PRE>
<P>Here you have a choice of techniques depending on whether you want to
 make your client subnet visible to clients on the other end:</P>
<UL>
<LI>If you want the single gateway to behave like the two shown above,
 with your clients hidden behind the NAT, then omit the<VAR> leftsubnet=</VAR>
 parameter. It then defaults to the gateway address. Clients on the
 other end then talk via the tunnel only to your gateway. The gateway
 takes packets emerging from the tunnel, applies normal masquerading,
 and forwards them to clients.</LI>
<LI>If you want to make your client machines visible, then give the
 client subnet addresses as the<VAR> leftsubnet=</VAR> parameter in the
 connection description and
<DL>
<DT>either</DT>
<DD>set<VAR> leftfirewall=yes</VAR> to use the default<VAR> updown</VAR>
 script</DD>
<DT>or</DT>
<DD>use your own script by giving its name in a<VAR> leftupdown=</VAR>
 parameter</DD>
</DL>
 These scripts are described in their own<A href="#updown"> section</A>.
<P>In this case, no masquerading is done. Packets to or from the client
 subnet are encrypted or decrypted without any change to their client
 subnet addresses, although of course the encapsulating packets use
 gateway addresses in their headers. Clients behind the right security
 gateway see a route via that gateway to the left subnet.</P>
</LI>
</UL>
<H3><A name="nat_bad">NAT between gateways is problematic</A></H3>
<P>We recommend not trying to build IPsec connections which pass through
 a NAT machine. This setup poses problems:</P>
<PRE>      clients --- SG --- NAT ---------- SG</PRE>
<P>If you must try it, some references are:</P>
<UL>
<LI>Jean_Francois Nadeau's document on doing<A href="http://jixen.tripod.com/#NATed gateways">
 IPsec behind NAT</A></LI>
<LI><A href="#VPN.masq">VPN masquerade patches</A> to make a Linux NAT
 box handle IPsec packets correctly</LI>
</UL>
<H3><A name="NAT.ref">Other references on NAT and IPsec</A></H3>
<P>Other documents which may be relevant include:</P>
<UL>
<LI>an Internet Draft on<A href="http://search.ietf.org/internet-drafts/draft-aboba-nat-ipsec-04.txt">
 IPsec and NAT</A> which may eventually evolve into a standard solution
 for this problem.</LI>
<LI>an informational<A href="http://www.cis.ohio-state.edu/rfc/rfc2709.txt">
 RFC</A>,<CITE> Security Model with Tunnel-mode IPsec for NAT Domains</CITE>
.</LI>
<LI>an<A href="http://www.cisco.com/warp/public/759/ipj_3-4/ipj_3-4_nat.html">
 article</A> in Cisco's<CITE> Internet Protocol Journal</CITE></LI>
</UL>
<H2><A name="complications">Other complications</A></H2>
<P>Of course simply allowing UDP 500 and ESP packets is not the whole
 story. Various other issues arise in making IPsec and packet filters
 co-exist and even co-operate. Some of them are summarised below.</P>
<H3><A name="through">IPsec<EM> through</EM></A> the gateway</H3>
<P>Basic IPsec packet filtering rules deal only with packets addressed
 to or sent from your IPsec gateway.</P>
<P>It is a separate policy decision whether to permit such packets to
 pass through the gateway so that client machines can build end-to-end
 IPsec tunnels of their own. This may not be practical if you are using<A
href="#NAT"> NAT (IP masquerade)</A> on your gateway, and may conflict
 with some corporate security policies.</P>
<P>Where possible, allowing this is almost certainly a good idea. Using
 IPsec on an end-to-end basis is more secure than gateway-to-gateway.</P>
<P>Doing it is quite simple. You just need firewall rules that allow UDP
 port 500 and protocols 50 and 51 to pass through your gateway. If you
 wish, you can of course restrict this to certain hosts.</P>
<H3><A name="ipsec_only">Preventing non-IPsec traffic</A></H3>
 You can also filter<EM> everything but</EM> UDP port 500 and ESP or AH
 to restrict traffic to IPsec only, either for anyone communicating with
 your host or just for specific partners.
<P>One application of this is for the telecommuter who might have:</P>
<PRE>     Sunset==========West------------------East ================= firewall --- the Internet
         home network      untrusted net        corporate network</PRE>
<P>The subnet on the right is 0.0.0.0/0, the whole Internet. The West
 gateway is set up so that it allows only IPsec packets to East in or
 out.</P>
<P>This configuration is used in AT&amp;T Research's network. For details,
 see the<A href="#applied"> papers</A> links in our introduction.</P>
<P>Another application would be to set up firewall rules so that an
 internal machine, such as an employees-only web server, could not talk
 to the outside world except via specific IPsec tunnels.</P>
<H3><A name="unknowngate">Filtering packets from unknown gateways</A></H3>
<P>It is possible to use firewall rules to restrict UDP 500, ESP and AH
 packets so that these packets are accepted only from known gateways.
 This is not strictly necessary since FreeS/WAN will discard packets
 from unknown gateways. You might, however, want to do it for any of a
 number of reasons. For example:</P>
<UL>
<LI>Arguably, &quot;belt and suspenders&quot; is the sensible approach to
 security. If you can block a potential attack in two ways, use both.
 The only question is whether to look for a third way after implementing
 the first two.</LI>
<LI>Some admins may prefer to use the firewall code this way because
 they prefer firewall logging to FreeS/WAN's logging.</LI>
<LI>You may need it to implement your security policy. Consider an
 employee working at home, and a policy that says traffic from the home
 system to the Internet at large must go first via IPsec to the
 corporate LAN and then out to the Internet via the corporate firewall.
 One way to do that is to make<VAR> ipsec0</VAR> the default route on
 the home gateway and provide exceptions only for UDP 500 and ESP to the
 corporate gateway. Everything else is then routed via the tunnel to the
 corporate gateway.</LI>
</UL>
<P>It is not possible to use only static firewall rules for this
 filtering if you do not know the other gateways' IP addresses in
 advance, for example if you have &quot;road warriors&quot; who may connect from a
 different address each time or if want to do<A href="#carpediem">
 opportunistic encryption</A> to arbitrary gateways. In these cases, you
 can accept UDP 500 IKE packets from anywhere, then use the<A href="#updown">
 updown</A> script feature of<A href="manpage.d/ipsec_pluto.8.html">
 pluto(8)</A> to dynamically adjust firewalling for each negotiated
 tunnel.</P>
<P>Firewall packet filtering does not much reduce the risk of a<A href="#DOS">
 denial of service attack</A> on FreeS/WAN. The firewall can drop
 packets from unknown gateways, but KLIPS does that quite efficiently
 anyway, so you gain little. The firewall cannot drop otherwise
 legitmate packets that fail KLIPS authentication, so it cannot protect
 against an attack designed to exhaust resources by making FreeS/WAN
 perform many expensive authentication operations.</P>
<P>In summary, firewall filtering of IPsec packets from unknown gateways
 is possible but not strictly necessary.</P>
<H2><A name="otherfilter">Other packet filters</A></H2>
<P>When the IPsec gateway is also acting as your firewall, other packet
 filtering rules will be in play. In general, those are outside the
 scope of this document. See our<A href="#firewall.linux"> Linux
 firewall links</A> for information. There are a few types of packet,
 however, which can affect the operation of FreeS/WAN or of diagnostic
 tools commonly used with it. These are discussed below.</P>
<H3><A name="ICMP">ICMP filtering</A></H3>
<P><A href="#ICMP.gloss">ICMP</A> is the<STRONG> I</STRONG>nternet<STRONG>
 C</STRONG>ontrol<STRONG> M</STRONG>essage<STRONG> P</STRONG>rotocol. It
 is used for messages between IP implementations themselves, whereas IP
 used is used between the clients of those implementations. ICMP is,
 unsurprisingly, used for control messages. For example, it is used to
 notify a sender that a desination is not reachable, or to tell a router
 to reroute certain packets elsewhere.</P>
<P>ICMP handling is tricky for firewalls.</P>
<UL>
<LI>You definitely want some ICMP messages to get through; things won't
 work without them. For example, your clients need to know if some
 destination they ask for is unreachable.</LI>
<LI>On the other hand, you do equally definitely do not want untrusted
 folk sending arbitrary control messages to your machines. Imagine what
 someone moderately clever and moderately malicious could do to you,
 given control of your network's routing.</LI>
</UL>
<P>ICMP does not use ports. Messages are distinguished by a &quot;message
 type&quot; field and, for some types, by an additional &quot;code&quot; field. The
 definitive list of types and codes is on the<A href="http://www.iana.org">
 IANA</A> site.</P>
<P>One expert uses this definition for ICMP message types to be dropped
 at the firewall.</P>
<PRE># ICMP types which lack socially redeeming value.
#  5     Redirect
#  9     Router Advertisement
# 10     Router Selection
# 15     Information Request
# 16     Information Reply
# 17     Address Mask Request
# 18     Address Mask Reply

badicmp='5 9 10 15 16 17 18'</PRE>
<P>A more conservative approach would be to make a list of allowed types
 and drop everything else.</P>
<P>Whichever way you do it, your ICMP filtering rules on a FreeS/WAN
 gateway should allow at least the following ICMP packet types:</P>
<DL>
<DT>echo (type 8)</DT>
<DD></DD>
<DT>echo reply (type 0)</DT>
<DD>These are used by ping(1). We recommend allowing both types through
 the tunnel and to or from your gateway's external interface, since
 ping(1) is an essential testing tool.
<P>It is fairly common for firewalls to drop ICMP echo packets addressed
 to machines behind the firewall. If that is your policy, please create
 an exception for such packets arriving via an IPsec tunnel, at least
 during intial testing of those tunnels.</P>
</DD>
<DT>destination unreachable (type 3)</DT>
<DD>This is used, with code 4 (Fragmentation Needed and Don't Fragment
 was Set) in the code field, to control<A href="#pathMTU"> path MTU
 discovery</A>. Since IPsec processing adds headers, enlarges packets
 and may cause fragmentation, an IPsec gateway should be able to send
 and receive these ICMP messages<STRONG> on both inside and outside
 interfaces</STRONG>.</DD>
</DL>
<H3><A name="traceroute">UDP packets for traceroute</A></H3>
<P>The traceroute(1) utility uses UDP port numbers from 33434 to
 approximately 33633. Generally, these should be allowed through for
 troubleshooting.</P>
<P>Some firewalls drop these packets to prevent outsiders exploring the
 protected network with traceroute(1). If that is your policy, consider
 creating an exception for such packets arriving via an IPsec tunnel, at
 least during intial testing of those tunnels.</P>
<H3><A name="l2tp">UDP for L2TP</A></H3>
<P> Windows 2000 does, and products designed for compatibility with it
 may, build<A href="#l2tp"> L2TP</A> tunnels over IPsec connections.</P>
<P>For this to work, you must allow UDP protocol 1701 packets coming out
 of your tunnels to continue to their destination. You can, and probably
 should, block such packets to or from your external interfaces, but
 allow them from<VAR> ipsec0</VAR>.</P>
<P>See also our Windows 2000<A href="interop.html#win2k"> interoperation
 discussion</A>.</P>
<H2><A name="packets">How it all works: IPsec packet details</A></H2>
<P>IPsec uses three main types of packet:</P>
<DL>
<DT><A href="#IKE">IKE</A> uses<STRONG> the UDP protocol and port 500</STRONG>
.</DT>
<DD>Unless you are using only (less secure, not recommended) manual
 keying, you need IKE to negotiate connection parameters, acceptable
 algorithms, key sizes and key setup. IKE handles everything required to
 set up, rekey, repair or tear down IPsec connections.</DD>
<DT><A href="#ESP">ESP</A> is<STRONG> protocol number 50</STRONG></DT>
<DD>This is required for encrypted connections.</DD>
<DT><A href="#AH">AH</A> is<STRONG> protocol number 51</STRONG></DT>
<DD>This can be used where only authentication, not encryption, is
 required.</DD>
</DL>
<P>All of those packets should have appropriate IPsec gateway addresses
 in both the to and from IP header fields. Firewall rules can check this
 if you wish, though it is not strictly necessary. This is discussed in
 more detail<A href="#unknowngate"> later</A>.</P>
<P>IPsec processing of incoming packets authenticates them then removes
 the ESP or AH header and decrypts if necessary. Successful processing
 exposes an inner packet which is then delivered back to the firewall
 machinery, marked as having arrived on an<VAR> ipsec[0-3]</VAR>
 interface. Firewall rules can use that interface label to distinguish
 these packets from unencrypted packets which are labelled with the
 physical interface they arrived on (or perhaps with a non-IPsec virtual
 interface such as<VAR> ppp0</VAR>).</P>
<P>One of our users sent a mailing list message with a<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/12/msg00006.html">
 diagram</A> of the packet flow.</P>
<H3><A name="noport">ESP and AH do not have ports</A></H3>
<P>Some protocols, such as TCP and UDP, have the notion of ports. Others
 protocols, including ESP and AH, do not. Quite a few IPsec newcomers
 have become confused on this point. There are no ports<EM> in</EM> the
 ESP or AH protocols, and no ports used<EM> for</EM> them. For these
 protocols,<EM> the idea of ports is completely irrelevant</EM>.</P>
<H3><A name="header">Header layout</A></H3>
<P>The protocol numbers for ESP or AH are used in the 'next header'
 field of the IP header. On most non-IPsec packets, that field would
 have one of:</P>
<UL>
<LI>1 for ICMP</LI>
<LI>4 for IP-in-IP encapsulation</LI>
<LI>6 for TCP</LI>
<LI>17 for UDP</LI>
<LI>... or one of about 100 other possibilities listed by<A href="http://www.iana.org">
 IANA</A></LI>
</UL>
<P>Each header in the sequence tells what the next header will be. IPsec
 adds headers for ESP or AH near the beginning of the sequence. The
 original headers are kept and the 'next header' fields adjusted so that
 all headers can be correctly interpreted.</P>
<P>For example, using<STRONG> [</STRONG><STRONG> ]</STRONG> to indicate
 data protected by ESP and unintelligible to an eavesdropper between the
 gateways:</P>
<UL>
<LI>a simple packet might have only IP and TCP headers with:
<UL>
<LI>IP header says next header --&gt; TCP</LI>
<LI>TCP header port number --&gt; which process to send data to</LI>
<LI>data</LI>
</UL>
</LI>
<LI>with ESP<A href="#transport"> transport mode</A> encapsulation, that
 packet would have:
<UL>
<LI>IP header says next header --&gt; ESP</LI>
<LI>ESP header<STRONG> [</STRONG> says next --&gt; TCP</LI>
<LI>TCP header port number --&gt; which process to send data to</LI>
<LI>data<STRONG> ]</STRONG></LI>
</UL>
 Note that the IP header is outside ESP protection, visible to an
 attacker, and that the final destination must be the gateway.</LI>
<LI>with ESP in<A href="#tunnel"> tunnel mode</A>, we might have:
<UL>
<LI>IP header says next header --&gt; ESP</LI>
<LI>ESP header<STRONG> [</STRONG> says next --&gt; IP</LI>
<LI>IP header says next header --&gt; TCP</LI>
<LI>TCP header port number --&gt; which process to send data to</LI>
<LI>data<STRONG> ]</STRONG></LI>
</UL>
 Here the inner IP header is protected by ESP, unreadable by an
 attacker. Also, the inner header can have a different IP address than
 the outer IP header, so the decrypted packet can be routed from the
 IPsec gateway to a final destination which may be another machine.</LI>
</UL>
<P>Part of the ESP header itself is encrypted, which is why the<STRONG>
 [</STRONG> indicating protected data appears in the middle of some
 lines above. The next header field of the ESP header is protected. This
 makes<A href="#traffic"> traffic analysis</A> more difficult. The next
 header field would tell an eavesdropper whether your packet was UDP to
 the gateway, TCP to the gateway, or encapsulated IP. It is better not
 to give this information away. A clever attacker may deduce some of it
 from the pattern of packet sizes and timings, but we need not make it
 easy.</P>
<P>IPsec allows various combinations of these to match local policies,
 including combinations that use both AH and ESP headers or that nest
 multiple copies of these headers.</P>
<P>For example, suppose my employer has an IPsec VPN running between two
 offices so all packets travelling between the gateways for those
 offices are encrypted. If gateway policies allow it (The admins could
 block UDP 500 and protocols 50 and 51 to disallow it), I can build an
 IPsec tunnel from my desktop to a machine in some remote office. Those
 packets will have one ESP header throughout their life, for my
 end-to-end tunnel. For part of the route, however, they will also have
 another ESP layer for the corporate VPN's encapsulation. The whole
 header scheme for a packet on the Internet might be:</P>
<UL>
<LI>IP header (with gateway address) says next header --&gt; ESP</LI>
<LI>ESP header<STRONG> [</STRONG> says next --&gt; IP</LI>
<LI>IP header (with receiving machine address) says next header --&gt; ESP</LI>
<LI>ESP header<STRONG> [</STRONG> says next --&gt; TCP</LI>
<LI>TCP header port number --&gt; which process to send data to</LI>
<LI>data<STRONG> ]]</STRONG></LI>
</UL>
<P>The first ESP (outermost) header is for the corporate VPN. The inner
 ESP header is for the secure machine-to-machine link.</P>
<H3><A name="dhr">DHR on the updown script</A></H3>
<P>Here are some mailing list comments from<A href="manpage.d/ipsec_pluto.8.html">
 pluto(8)</A> developer Hugh Redelmeier on an earlier draft of this
 document:</P>
<PRE>There are many important things left out

- firewalling is important but must reflect (implement) policy.  Since
  policy isn't the same for all our customers, and we're not experts,
  we should concentrate on FW and MASQ interactions with FreeS/WAN.

- we need a diagram to show packet flow WITHIN ONE MACHINE, assuming
  IKE, IPsec, FW, and MASQ are all done on that machine.  The flow is
  obvious if the components are run on different machines (trace the
  cables).

  IKE input:
        + packet appears on public IF, as UDP port 500
        + input firewalling rules are applied (may discard)
        + Pluto sees the packet.

  IKE output:
        + Pluto generates the packet &amp; writes to public IF, UDP port 500
        + output firewalling rules are applied (may discard)
        + packet sent out public IF

  IPsec input, with encapsulated packet, outer destination of this host:
        + packet appears on public IF, protocol 50 or 51.  If this
          packet is the result of decapsulation, it will appear
          instead on the paired ipsec IF.
        + input firewalling rules are applied (but packet is opaque)
        + KLIPS decapsulates it, writes result to paired ipsec IF
        + input firewalling rules are applied to resulting packet
          as input on ipsec IF
        + if the destination of the packet is this machine, the
          packet is passed on to the appropriate protocol handler.
          If the original packet was encapsulated more than once
          and the new outer destination is this machine, that
          handler will be KLIPS.
        + otherwise:
          * routing is done for the resulting packet.  This may well
            direct it into KLIPS for encoding or encrypting.  What
            happens then is described elsewhere.
          * forwarding firewalling rules are applied
          * output firewalling rules are applied
          * the packet is sent where routing specified

 IPsec input, with encapsulated packet, outer destination of another host:
        + packet appears on some IF, protocol 50 or 51
        + input firewalling rules are applied (but packet is opaque)
        + routing selects where to send the packet
        + forwarding firewalling rules are applied (but packet is opaque)
        + packet forwarded, still encapsulated

  IPsec output, from this host or from a client:
        + if from a client, input firewalling rules are applied as the
          packet arrives on the private IF
        + routing directs the packet to an ipsec IF (this is how the
          system decides KLIPS processing is required)
        + if from a client, forwarding firewalling rules are applied
        + KLIPS eroute mechanism matches the source and destination
          to registered eroutes, yielding a SPI group.  This dictates
          processing, and where the resulting packet is to be sent
          (the destinations SG and the nexthop).
        + output firewalling is not applied to the resulting
          encapsulated packet

- Until quite recently, KLIPS would double encapsulate packets that
  didn't strictly need to be.  Firewalling should be prepared for
  those packets showing up as ESP and AH protocol input packets on
  an ipsec IF.

- MASQ processing seems to be done as if it were part of the
  forwarding firewall processing (this should be verified).

- If a firewall is being used, it is likely the case that it needs to
  be adjusted whenever IPsec SAs are added or removed.  Pluto invokes
  a script to do this (and to adjust routing) at suitable times.  The
  default script is only suitable for ipfwadm-managed firewalls.  Under
  LINUX 2.2.x kernels, ipchains can be managed by ipfwadm (emulation),
  but ipchains more powerful if manipulated using the ipchains command.
  In this case, a custom updown script must be used.

  We think that the flexibility of ipchains precludes us supplying an
  updown script that would be widely appropriate.</PRE>
<HR>
<H1><A NAME="trouble"></A>Linux FreeS/WAN Troubleshooting Guide</H1>
<H2><A NAME="overview"></A>Overview</H2>
<P> This document covers several general places where you might have a
 problem:</P>
<OL>
<LI><A HREF="#install">During install</A>.</LI>
<LI><A HREF="#negotiation">During the negotiation process</A>.</LI>
<LI><A HREF="#use">Using an established connection</A>.</LI>
</OL>
<P>This document also contains<A HREF="#notes"> notes</A> which expand
 on points made in these sections, and tips for<A HREF="#prob.report">
 problem reporting</A>. If the other end of your connection is not
 FreeS/WAN, you'll also want to read our<A HREF="interop.html#interop.problem">
 interoperation</A> document.</P>
<H2><A NAME="install"></A>1. During Install</H2>
<H3><A NAME="8_2_1">1.1 RPM install gotchas</A></H3>
<P>With the RPM method:</P>
<UL>
<LI>Be sure you have installed both the userland tools and the kernel
 components. One will not work without the other. For example, when
 using FreeS/WAN-produced RPMs for our 2.04 release, you need both:
<PRE>    freeswan-userland-2.04_2.4.20_20.9-0.i386.rpm
    freeswan-module-2.04_2.4.20_20.9-0.i386.rpm
</PRE>
</LI>
</UL>
<H3><A NAME="8_2_2">1.2 Problems installing from source</A></H3>
<P>When installing from source, you may find these problems:</P>
<UL>
<LI>Missing library. See<A HREF="#gmp.h_missing"> this</A> FAQ.</LI>
<LI>Missing utilities required for compile. See this<A HREF="install.html#tool.lib">
 checklist</A>.</LI>
<LI>Kernel version incompatibility. See<A HREF="#k.versions"> this</A>
 FAQ.</LI>
<LI>Another compile problem. Find information in the out.* files, ie.
 out.kpatch, out.kbuild, created at compile time in the top-level Linux
 FreeS/WAN directory. Error messages generated by KLIPS during the boot
 sequence are accessible with the<VAR> dmesg</VAR> command.
<BR> Check the list archives and the List in Brief to see if this is a
 known issue. If it is not, report it to the bugs list as described in
 our<A HREF="#prob.report"> problem reporting</A> section. In some
 cases, you may be asked to provide debugging information using gdb;
 details<A HREF="#gdb"> below</A>.</LI>
<LI>If your kernel compiles but you fail to install your new
 FreeS/WAN-enabled kernel, review the sections on<A HREF="install.html#newk">
 installing the patched kernel</A>, and<A HREF="#testinstall"> testing</A>
 to see if install succeeded.</LI>
</UL>
<H3><A NAME="install.check"></A>1.3 Install checks</H3>
<P><VAR>ipsec verify</VAR> checks a number of FreeS/WAN essentials. Here
 are some hints on what do to when your system doesn't check out:</P>
<P></P>
<TABLE border="1">
<TR><TD><STRONG>Problem</STRONG></TD><TD><STRONG>Status</STRONG></TD><TD>
<STRONG>Action</STRONG></TD></TR>
<TR><TD><VAR>ipsec</VAR> not on-path</TD><TD>&nbsp;</TD><TD>
<P>Add<VAR> /usr/local/sbin</VAR> to your PATH.</P>
</TD></TR>
<TR><TD>Missing KLIPS support</TD><TD><FONT COLOR="#FF0000">critical</FONT>
</TD><TD>See<A HREF="#noKLIPS"> this FAQ.</A></TD></TR>
<TR><TD>No RSA private key</TD><TD>&nbsp;</TD><TD>
<P>Follow<A HREF="install.html#genrsakey"> these instructions</A> to
 create an RSA key pair for your host. RSA keys are:</P>
<UL>
<LI>required for opportunistic encryption, and</LI>
<LI>our preferred method to authenticate pre-configured connections.</LI>
</UL>
</TD></TR>
<TR><TD><VAR>pluto</VAR> not running</TD><TD><FONT COLOR="#FF0000">
critical</FONT></TD><TD>
<PRE>service ipsec start</PRE>
</TD></TR>
<TR><TD>No port 500 hole</TD><TD><FONT COLOR="#FF0000">critical</FONT></TD><TD>
Open port 500 for IKE negotiation.</TD></TR>
<TR><TD>Port 500 check N/A</TD><TD>&nbsp;</TD><TD>Check that port 500 is open
 for IKE negotiation.</TD></TR>
<TR><TD>Failed DNS checks</TD><TD>&nbsp;</TD><TD>Opportunistic encryption
 requires information from DNS. To set this up, see<A HREF="#opp.setup">
 our instructions</A>.</TD></TR>
<TR><TD>No public IP address</TD><TD>&nbsp;</TD><TD>Check that the interface
 which you want to protect with IPSec is up and running.</TD></TR>
</TABLE>
<H3><A NAME="oe.trouble"></A>1.3 Troubleshooting OE</H3>
<P>OE should work with no local configuration, if you have posted DNS
 TXT records according to the instructions in our<A HREF="quickstart.html">
 quickstart guide</A>. If you encounter trouble, try these hints. We
 welcome additional hints via the<A HREF="mail.html"> users' mailing
 list</A>.</P>
<TABLE border="1">
<TR><TD><STRONG>Symptom</STRONG></TD><TD><STRONG>Problem</STRONG></TD><TD>
<STRONG>Action</STRONG></TD></TR>
<TR><TD> You're running FreeS/WAN 2.01 (or later), and initiating a
 connection to FreeS/WAN 2.00 (or earlier). In your logs, you see a
 message like:
<PRE>no RSA public key known for '192.0.2.13';
DNS search for KEY failed (no KEY record
for 13.2.0.192.in-addr.arpa.)</PRE>
 The older FreeS/WAN logs no error.</TD><TD><A NAME="oe.trouble.flagday">
</A> A protocol level incompatibility between 2.01 (or later) and 2.00
 (or earlier) causes this error. It occurs when a FreeS/WAN 2.01 (or
 later) box for which no KEY record is posted attempts to initiate an OE
 connection to older FreeS/WAN versions (2.00 and earlier). Note that
 older versions can initiate to newer versions without this error.</TD><TD>
If you control the peer host, upgrade its FreeS/WAN to 2.01 (or later),
 and post new style TXT records for it. If not, but if you know its
 sysadmin, perhaps a quick note is in order. If neither option is
 possible, you can ease the transition by posting an old style KEY
 record (created with a command like &quot;ipsec&nbsp;showhostkey&nbsp;--key&quot;) to the
 reverse map for the FreeS/WAN 2.01 (or later) box.</TD></TR>
<TR><TD>OE host is very slow to contact other hosts.</TD><TD>Slow DNS
 service while running OE.</TD><TD>It's a good idea to run a caching DNS
 server on your OE host, as outlined in<A HREF="http://lists.freeswan.org/pipermail/design/2003-January/004205.html">
 this mailing list message</A>. If your DNS servers are elsewhere, put
 their IPs in the<VAR> clear</VAR> policy group, and re-read groups with
<PRE>ipsec auto --rereadgroups</PRE>
</TD></TR>
<TR><TD>
<PRE>Can't Opportunistically initiate for
192.0.2.2 to 192.0.2.3: no TXT record
for 13.2.0.192.in-addr.arpa.</PRE>
</TD><TD>Peer is not set up for OE.</TD><TD>
<P>None. Plenty of hosts on the Internet do not run OE. If, however, you
 have set OE up on that peer, this may indicate that you need to wait up
 to 48 hours for its DNS records to propagate.</P>
</TD></TR>
<TR><TD><VAR>ipsec verify</VAR> does not find DNS records:
<PRE>...
Looking for TXT in forward map:
                xy.example.com...[FAILED]
Looking for TXT in reverse map...[FAILED]
...</PRE>
 You also experience authentication failure:
<BR>
<PRE>Possible authentication failure:
no acceptable response to our
first encrypted message</PRE>
</TD><TD>DNS records are not posted or have not propagated.</TD><TD>Did
 you post the DNS records necessary for OE? If not, do so using the
 instructions in our<A HREF="#quickstart"> quickstart guide</A>. If so,
 wait up to 48 hours for the DNS records to propagate.</TD></TR>
<TR><TD><VAR>ipsec verify</VAR> does not find DNS records, and you
 experience authentication failure.</TD><TD>For iOE, your ID does not
 match location of forward DNS record.</TD><TD>In<VAR> config setup</VAR>
, change<VAR> myid=</VAR> to match the forward DNS where you posted the
 record. Restart FreeS/WAN. For reference, see our<A HREF="#opp.client">
 iOE instructions</A>.</TD></TR>
<TR><TD><VAR>ipsec verify</VAR> finds DNS records, yet there is still
 authentication failure. ( ? )</TD><TD>DNS records are malformed.</TD><TD>
Re-create the records and send new copies to your DNS administrator.</TD>
</TR>
<TR><TD><VAR>ipsec verify</VAR> finds DNS records, yet there is still
 authentication failure. ( ? )</TD><TD>DNS records show different keys
 for a gateway vs. its subnet hosts.</TD><TD>All TXT records for boxes
 protected by an OE gateway must contain the gateway's public key.
 Re-create and re-post any incorrect records using<A HREF="#opp.incoming">
 these instructions</A>.</TD></TR>
<TR><TD>OE gateway loses connectivity to its subnet. The gateway's
 routing table shows routes to the subnet through IPsec interfaces.</TD><TD>
The subnet is part of the<VAR> private</VAR> or<VAR> block</VAR> policy
 group on the gateway.</TD><TD>Remove the subnet from the group, and
 reread groups with
<PRE>ipsec auto --rereadgroups</PRE>
</TD></TR>
<TR><TD>OE does not work to hosts on the local LAN.</TD><TD>This is a
 known issue.</TD><TD>See<A HREF="opportunism.known-issues"> this list</A>
 of known issues with OE.</TD></TR>
<TR><TD>FreeS/WAN does not seem to be executing your default policy. In
 your logs, you see a message like:
<PRE>/etc/ipsec.d/policies/iprivate-or-clear&quot;
line 14: subnet &quot;0.0.0.0/0&quot;,
source 192.0.2.13/32,
already &quot;private-or-clear&quot;</PRE>
</TD><TD><A HREF="#fullnet">Fullnet</A> in a policy group file defines
 your default policy. Fullnet should normally be present in only one
 policy group file. The fine print: you can have two default policies
 defined so long as they protect different local endpoints (e.g. the
 FreeS/WAN gateway and a subnet).</TD><TD> Find all policies which
 contain fullnet with:
<BR>
<PRE>grep -F 0.0.0.0/0 /etc/ipsec.d/policies/*</PRE>
 then remove the unwanted occurrence(s).</TD></TR>
</TABLE>
<H2><A NAME="negotiation"></A>2. During Negotiation</H2>
<P>When you fail to bring up a tunnel, you'll need to find out:</P>
<UL>
<LI><A HREF="#state">what your connection state is,</A> and often</LI>
<LI><A HREF="#find.pluto.error">an error message</A>.</LI>
</UL>
<P>before you can<A HREF="#interpret.pluto.error"> diagnose your problem</A>
.</P>
<H3><A NAME="state"></A>2.1 Determine Connection State</H3>
<H4><A NAME="8_3_1_1">Finding current state</A></H4>
<P>You can see connection states (STATE_MAIN_I1 and so on) when you
 bring up a connection on the command line. If you have missed this, or
 brought up your connection automatically, use:</P>
<PRE>ipsec auto --status</PRE>
<P>The most relevant state is the last one reached.</P>
<H4><A NAME="8_3_1_2"><VAR>What's this supposed to look like?</VAR></A></H4>
<P>Negotiations should proceed though various states, in the processes
 of:</P>
<OL>
<LI>IKE negotiations (aka Phase 1, Main Mode, STATE_MAIN_*)</LI>
<LI>IPSEC negotiations (aka Phase 2, Quick Mode, STATE_QUICK_*)</LI>
</OL>
<P>These are done and a connection is established when you see messages
 like:</P>
<PRE>    000 #21: &quot;myconn&quot; STATE_MAIN_I4 (ISAKMP SA established)...
    000 #2: &quot;myconn&quot; STATE_QUICK_I2 (sent QI2, IPsec SA established)...</PRE>
<P> Look for the key phrases are &quot;ISAKMP SA established&quot; and &quot;IPSec SA
 established&quot;, with the relevant connection name. Often, this happens at
 STATE_MAIN_I4 and STATE_QUICK_I2, respectively.</P>
<P><VAR>ipsec auto --status</VAR> will tell you what states<STRONG> have
 been achieved</STRONG>, rather than the current state. Since
 determining the current state is rather more difficult to do, current
 state information is not available from Linux FreeS/WAN. If you are
 actively bringing a connection up, the status report's last states for
 that connection likely reflect its current state. Beware, though, of
 the case where a connection was correctly brought up but is now downed:
 Linux FreeS/WAN will not notice this until it attempts to rekey.
 Meanwhile, the last known state indicates that the connection has been
 established.</P>
<P>If your connection is stuck at STATE_MAIN_I1, skip straight to<A HREF="#ikepath">
 here</A>.</P>
<H3><A NAME="find.pluto.error"></A>2.2 Finding error text</H3>
<P>Solving most errors will require you to find verbose error text,
 either on the command line or in the logs.</P>
<H4><A NAME="8_3_2_1">Verbose start for more information</A></H4>
<P> Note that you can get more detail from<VAR> ipsec auto</VAR> using
 the --verbose flag:</P>
<PRE STYLE="margin-bottom: 0.2in">    ipsec auto --verbose --up west-east</PRE>
<P> More complete information can be gleaned from the<A HREF="#logusage">
 log files</A>.</P>
<H4><A NAME="8_3_2_2">Debug levels count</A></H4>
<P>The amount of description you'll get here depends on ipsec.conf debug
 settings,<VAR> klipsdebug</VAR>= and<VAR> plutodebug</VAR>=. When
 troubleshooting, set at least one of these to<VAR> all</VAR>, and when
 done, reset it to<VAR> none</VAR> so your logs don't fill up. Note that
 you must have enabled the<VAR> klipsdebug</VAR><A HREF="install.html#allbut">
 compile-time option</A> for the<VAR> klipsdebug</VAR> configuration
 switch to work.</P>
<P>For negotiation problems<VAR> plutodebug</VAR> is most relevant.<VAR>
 klipsdebug</VAR> applies mainly to attempts to use an
 already-established connection. See also<A HREF="#parts"> this</A>
 description of the division of duties within Linux FreeS/WAN.</P>
<P>After raising your debug levels, restart Linux FreeS/WAN to ensure
 that ipsec.conf is reread, then recreate the error to generate verbose
 logs.</P>
<H4><A NAME="8_3_2_3"><VAR>ipsec barf</VAR> for lots of debugging
 information</A></H4>
<P><A HREF="manpage.d/ipsec_barf.8.html"><VAR> ipsec barf (8)</VAR></A>
 collects a bunch of useful debugging information, including these logs
 Use the command</P>
<PRE>
    ipsec barf &gt; barf.west
</PRE>
<P>to generate one.</P>
<H4><A NAME="8_3_2_4">Find the error</A></H4>
<P>Search out the failure point in your logs. Are there a handful of
 lines which succinctly describe how things are going wrong or contrary
 to your expectation? Sometimes the failure point is not immediately
 obvious: Linux FreeS/WAN's errors are usually not marked &quot;Error&quot;. Have
 a look in the<A HREF="faq.html"> FAQ</A> for what some common failures
 look like.</P>
<P>Tip: problems snowball. Focus your efforts on the first problem,
 which is likely to be the cause of later errors.</P>
<H4><A NAME="8_3_2_5">Play both sides</A></H4>
<P>Also find error text on the peer IPSec box. This gives you two
 perspectives on the same failure.</P>
<P>At times you will require information which only one side has. The
 peer can merely indicate the presence of an error, and its approximate
 point in the negotiations. If one side keeps retrying, it may be
 because there is a show stopper on the other side. Have a look at the
 other side and figure out what it doesn't like.</P>
<P>If the other end is not Linux FreeS/WAN, the principle is the same:
 replicate the error with its most verbose logging on, and capture the
 output to a file.</P>
<H3><A NAME="interpret.pluto.error"></A>2.3 Interpreting a Negotiation
 Error</H3>
<H4><A NAME="ikepath"></A>Connection stuck at STATE_MAIN_I1</H4>
<P>This error commonly happens because IKE (port 500) packets, needed to
 negotiate an IPSec connection, cannot travel freely between your IPSec
 gateways. See<A HREF="#packets"> our firewall document</A> for details.</P>
<H4><A NAME="8_3_3_2">Other errors</A></H4>
<P>Other errors require a bit more digging. Use the following resources:</P>
<UL>
<LI><A HREF="faq.html">the FAQ</A> . Since this document is constantly
 updated, the snapshot's FAQ may have a new entry relevant to your
 problem.</LI>
<LI>our<A HREF="background.html"> background document</A> . Special
 considerations which, while not central to Linux FreeS/WAN, are often
 tripped over. Includes problems with<A href="#MTU.trouble"> packet
 fragmentation</A>, and considerations for testing opportunism.</LI>
<LI>the<A HREF="#lists"> list archives</A>. Each of the searchable
 archives works differently, so it's worth checking each. Use a search
 term which is generic, but identifies your error, for example &quot;No
 connection is known for&quot;.
<BR> Often, you will find that your question has been answered in the
 past. Finding an archived answer is quicker than asking the list. You
 may, however, find similar questions without answers. If you do, send
 their URLs to the list with your trouble report. The additional
 examples may help the list tech support person find your answer.</LI>
<LI>Look into the code where the error is being generated. The pluto
 code is nicely documented with comments and meaningful variable names.</LI>
</UL>
<P>If you have failed to solve your problem with the help of these
 resources, send a detailed problem report to the users list, following
 these<A HREF="#prob.report"> guidelines</A>.</P>
<H2><A NAME="use"></A>3. Using a Connection</H2>
<H3><A NAME="8_4_1">3.1 Orienting yourself</A></H3>
<H4><A NAME="8_4_1_1"><VAR>How do I know if it works?</VAR></A></H4>
<P>Test your connection by sending packets through it. The simplest way
 to do this is with ping, but the ping needs to<STRONG> test the correct
 tunnel.</STRONG> See<A HREF="#testgates"> this example scenario</A> if
 you don't understand this.</P>
<P></P>
<P>If your ping returns, test any other connections you've brought u all
 check out, great. You may wish to<A HREF="#bigpacket"> test with large
 packets</A> for MTU problems.</P>
<H4><A NAME="8_4_1_2"><VAR>ipsec barf</VAR> is useful again</A></H4>
<P>If your ping fails to return, generate an ipsec barf debugging report
 on each IPSec gateway. On a non-Linux FreeS/WAN implementation, gather
 equivalent information. Use this, and the tips in the next sections, to
 troubleshoot. Are you sure that both endpoints are capable of hearing
 and responding to ping?</P>
<H3><A NAME="8_4_2">3.2 Those pesky configuration errors</A></H3>
<P>IPSec may be dropping your ping packets since they do not belong in
 the tunnels you have constructed:</P>
<UL>
<LI>Your ping may not test the tunnel you intend to test. For details,
 see our<A HREF="#cantping"> &quot;I can't ping&quot;</A> FAQ.</LI>
<LI> Alternately, you may have a configuration error. For example, you
 may have configured one of the four possible tunnels between two
 gateways, but not the one required to secure the important traffic
 you're now testing. In this case, add and start the tunnel, and try
 again.</LI>
</UL>
<P>In either case, you will often see a message like:</P>
<PRE>klipsdebug... no eroute</PRE>
<P>which we discuss in<A HREF="#no_eroute"> this FAQ</A>.</P>
<P>Note:</P>
<UL>
<LI><A HREF="#NAT.gloss">Network Address Translation (NAT)</A> and<A HREF="#masq">
 IP masquerade</A> may have an effect on which tunnels you need to
 configure.</LI>
<LI>When testing a tunnel that protects a multi-node subnet, try several
 subnet nodes as ping targets, in case one node is routing incorrectly.</LI>
</UL>
<H3><A NAME="route.firewall"></A>3.3 Check Routing and Firewalling</H3>
<P>If you've confirmed your configuration assumptions, the problem is
 almost certainly with routing or firewalling. Isolate the problem using
 interface statistics, firewall statistics, or a packet sniffer.</P>
<H4><A NAME="8_4_3_1">Background:</A></H4>
<UL>
<LI>Linux FreeS/WAN supplies all the special routing it needs; you need
 only route packets out through your IPSec gateway. Verify that on the<VAR>
 subnetted</VAR> machines you are using for your ping-test, your routing
 is as expected. I have seen a tunnel &quot;fail&quot; because the subnet machine
 sending packets out an alternate gateway (not our IPSec gateway) on
 their return path.</LI>
<LI>Linux FreeS/WAN requires particular<A HREF="firewall.html">
 firewalling considerations</A>. Check the firewall rules on your IPSec
 gateways and ensure that they allow IPSec traffic through. Be sure that
 no other machine - for example a router between the gateways - is
 blocking your IPSec packets.</LI>
</UL>
<H4><A NAME="ifconfig"></A>View Interface and Firewall Statistics</H4>
<P>Interface reports and firewall statistics can help you track down
 lost packets at a glance. Check any firewall statistics you may be
 keeping on your IPSec gateways, for dropped packets.</P>
<P><STRONG>Tip</STRONG>: You can take a snapshot of the packets
 processed by your firewall with:</P>
<PRE>    iptables -L -n -v</PRE>
<P>You can get creative with &quot;diff&quot; to find out what happens to a
 particular packet during transmission.</P>
<P>Both<VAR> cat /proc/net/dev</VAR> and<VAR> ifconfig</VAR> display
 interface statistics, and both are included in<VAR> ipsec barf</VAR>.
 Use either to check if any interface has dropped packets. If you find
 that one has, test whether this is related to your ping. While you ping
 continuously, print that interface's statistics several times. Does its
 drop count increase in proportion to the ping? If so, check why the
 packets are dropped there.</P>
<P>To do this, look at the firewall rules that apply to that interface.
 If the interface is an IPSec interface, more information may be
 available in the log. Grep for the word &quot;drop&quot; in a log which was
 created with<VAR> klipsdebug=all</VAR> as the error happened.</P>
<P>See also this<A HREF="#ifconfig1"> discussion</A> on interpreting<VAR>
 ifconfig</VAR> statistics.</P>
<H3><A NAME="sniff"></A>3.4 When in doubt, sniff it out</H3>
<P>If you have checked configuration assumptions, routing, and firewall
 rules, and your interface statistics yield no clue, it remains for you
 to investigate the mystery of the lost packet by the most thorough
 method: with a packet sniffer (providing, of course, that this is legal
 where you are working).</P>
<P>In order to detect packets on the ipsec virtual interfaces, you will
 need an up-to-date sniffer (tcpdump, ethereal, ksnuffle) on your IPSec
 gateway machines. You may also find it useful to sniff the ping
 endpoints.</P>
<H4><A NAME="8_4_4_1">Anticipate your packets' path</A></H4>
<P>Ping, and examine each interface along the projected path, checking
 for your ping's arrival. If it doesn't get to the the next stop, you
 have narrowed down where to look for it. In this way, you can isolate a
 problem area, and narrow your troubleshooting focus.</P>
<P>Within a machine running Linux FreeS/WAN, this<A HREF="#packets">
 packet flow diagram</A> will help you anticipate a packet's path.</P>
<P>Note that:</P>
<UL>
<LI> from the perspective of the tunneled packet, the entire tunnel is
 one hop. That's explained in<A HREF="#no_trace"> this</A> FAQ.</LI>
<LI> an encapsulated IPSec packet will look different, when sniffed,
 from the plaintext packet which generated it. You can see plaintext
 packets entering an IPSec interface and the resulting cyphertext
 packets as they emerge from the corresponding physical interface.</LI>
</UL>
<P>Once you isolate where the packet is lost, take a closer look at
 firewall rules, routing and configuration assumptions as they affect
 that specific area. If the packet is lost on an IPSec gateway, comb
 through<VAR> klipsdebug</VAR> output for anomalies.</P>
<P>If the packet goes through both gateways successfully and reaches the
 ping target, but does not return, suspect routing. Check that the ping
 target routes packets back to the IPSec gateway.</P>
<H3><A NAME="find.use.error"></A>3.5 Check your logs</H3>
<P>Here, too, log information can be useful. Start with the<A HREF="#find.pluto.error">
 guidelines above</A>.</P>
<P>For connection use problems, set<VAR> klipsdebug=all</VAR>. Note that
 you must have enabled the<VAR> klipsdebug</VAR><A HREF="install.html#allbut">
 compile-time option</A> to do this. Restart Linux FreeS/WAN so that it
 rereads<VAR> ipsec.conf</VAR>, then recreate the error condition. When
 searching through<VAR> klipsdebug</VAR> data, look especially for the
 keywords &quot;drop&quot; (as in dropped packets) and &quot;error&quot;.</P>
<P>Often the problem with connection use is not software error, but
 rather that the software is behaving contrary to expectation.</P>
<H4><A NAME="interpret.use.error"></A>Interpreting log text</H4>
<P>To interpret the Linux FreeS/WAN log text you've found, use the same
 resources as indicated for troubleshooting connection negotiation:<A HREF="faq.html">
 the FAQ</A> , our<A HREF="background.html"> background document</A>,
 and the<A HREF="#lists"> list archives</A>. Looking in the KLIPS code
 is only for the very brave.</P>
<P>If you are still stuck, send a<A HREF="#prob.report"> detailed
 problem report</A> to the users' list.</P>
<H3><A NAME="bigpacket"></A>3.6 More testing for the truly thorough</H3>
<H4><A NAME="8_4_6_1">Large Packets</A></H4>
<P>If each of your connections passed the ping test, you may wish to
 test by pinging with large packets (2000 bytes or larger). If it does
 not return, suspect MTU issues, and see this<A HREF="#MTU.trouble">
 discussion</A>.</P>
<H4><A NAME="8_4_6_2">Stress Tests</A></H4>
<P>In most users' view, a simple ping test, and perhaps a large-packet
 ping test suffice to indicate a working IPSec connection.</P>
<P>Some people might like to do additional stress tests prior to
 production use. They may be interested in this<A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/12/msg00224.html">
 testing protocol</A> we use at interoperation conferences, aka
 &quot;bakeoffs&quot;. We also have a<VAR> testing</VAR> directory that ships with
 the release.</P>
<H2><A NAME="prob.report"></A>4. Problem Reporting</H2>
<H3><A NAME="8_5_1">4.1 How to ask for help</A></H3>
<P>Ask for troubleshooting help on the users' mailing list,<A HREF="mailto:users@lists.freeswan.org">
 users@lists.freeswan.org</A>. While sometimes an initial query with a
 quick description of your intent and error will twig someone's memory
 of a similar problem, it's often necessary to send a second mail with a
 complete problem report.</P>
<P>When reporting problems to the mailing list(s), please include:</P>
<UL>
<LI>a brief description of the problem</LI>
<LI>if it's a compile problem, the actual output from make, showing the
 problem. Try to edit it down to only the relevant part, but when in
 doubt, be as complete as you can. If it's a kernel compile problem, any
 relevant out.* files</LI>
<LI>if it's a run-time problem, pointers to where we can find the
 complete output from &quot;ipsec barf&quot; from BOTH ENDS (not just one of
 them). Remember that it's common outside the US and Canada to pay for
 download volume, so if you can't post barfs on the web and send the URL
 to the mailing list, at least compress them with tar or gzip.
<BR> If you can, try to simplify the case that is causing the problem.
 In particular, if you clear your logs, start FreeS/WAN with no other
 connections running, cause the problem to happen, and then do<VAR>
 ipsec barf</VAR> on both ends immediately, that gives the smallest and
 least cluttered output.</LI>
<LI>any other error messages, complaints, etc. that you saw. Please send
 the complete text of the messages, not just a summary.</LI>
<LI>what your network setup is. Include subnets, gateway addresses, etc.
 A schematic diagram is a good format for this information.</LI>
<LI>exactly what you were trying to do with Linux FreeS/WAN, and exactly
 what went wrong</LI>
<LI>a fix, if you have one. But remember, you are sending mail to people
 all over the world; US residents and US citizens in particular, please
 read doc/exportlaws.html before sending code -- even small bug fixes --
 to the list or to us.</LI>
<LI>When in doubt about whether to include some seemingly-trivial item
 of information, include it. It is rare for problem reports to have too
 much information, and common for them to have too little.</LI>
</UL>
<P>Here are some good general guidelines on bug reporting:<A href="http://tuxedo.org/~esr/faqs/smart-questions.html">
 How To Ask Questions The Smart Way</A> and<A href="http://www.chiark.greenend.org.uk/~sgtatham/bugs.html">
 How to Report Bugs Effectively</A>.</P>
<H3><A NAME="8_5_2">4.2 Where to ask</A></H3>
<P>To report a problem, send mail about it to the users' list. If you
 are certain that you have found a bug, report it to the bugs list. If
 you encounter a problem while doing your own coding on the Linux
 FreeS/WAN codebase and think it is of interest to the design team,
 notify the design list. When in doubt, default to the users' list. More
 information about the mailing lists is found<A HREF="#lists"> here</A>.</P>
<P>For a number of reasons -- including export-control regulations
 affecting almost any<STRONG> private</STRONG> discussion of encryption
 software -- we prefer that problem reports and discussions go to the
 lists, not directly to the team. Beware that the list goes worldwide;
 US citizens, read this important information about your<A HREF="#exlaw">
 export laws</A>. If you're using this software, you really should be on
 the lists. To get onto them, visit<A HREF="http://lists.freeswan.org/">
 lists.freeswan.org</A>.</P>
<P>If you do send private mail to our coders or want a private reply
 from them, please make sure that the return address on your mail (From
 or Reply-To header) is a valid one. They have more important things to
 do than to unravel addresses that have been mangled in an attempt to
 confuse spammers.</P>
<H2><A NAME="notes"></A>5. Additional Notes on Troubleshooting</H2>
<P>The following sections supplement the Guide:<A HREF="#system.info">
 information available on your system</A>;<A HREF="#testgates"> testing
 between security gateways</A>;<A HREF="#ifconfig1"> ifconfig reports
 for KLIPS debugging</A>;<A HREF="#gdb"> using GDB on Pluto</A>.</P>
<H3><A NAME="system.info"></A>5.1 Information available on your system</H3>
<H4><A NAME="logusage"></A>Logs used</H4>
<P>Linux FreeS/WAN logs to:</P>
<UL>
<LI>/var/log/secure (or, on Debian, /var/log/auth.log)</LI>
<LI>/var/log/messages</LI>
</UL>
<P>Check both places to get full information. If you find nothing, check
 your<VAR> syslogd.conf(5)</VAR> to see where your /etc/syslog.conf or
 equivalent is directing<VAR> authpriv</VAR> messages.</P>
<H4><A NAME="pages"></A>man pages provided</H4>
<DL>
<DT><A HREF="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</A></DT>
<DD> Manual page for IPSEC configuration file.</DD>
<DT><A HREF="manpage.d/ipsec.8.html"> ipsec(8)</A></DT>
<DD STYLE="margin-bottom: 0.2in"> Primary man page for ipsec utilities.</DD>
</DL>
<P> Other man pages are on<A HREF="manpages.html"> this list</A> and in</P>
<UL>
<LI>/usr/local/man/man3</LI>
<LI>/usr/local/man/man5</LI>
<LI>/usr/local/man/man8/ipsec_*</LI>
</UL>
<H4><A NAME="statusinfo"></A>Status information</H4>
<DL>
<DT>ipsec auto --status</DT>
<DD> Command to get status report from running system. Displays Pluto's
 state. Includes the list of connections which are currently &quot;added&quot; to
 Pluto's internal database; lists state objects reflecting ISAKMP and
 IPsec SAs being negotiated or installed.</DD>
<DT> ipsec look</DT>
<DD> Brief status info.</DD>
<DT> ipsec barf</DT>
<DD STYLE="margin-bottom: 0.2in"> Copious debugging info.</DD>
</DL>
<H3><A NAME="testgates"></A> 5.2 Testing between security gateways</H3>
<P>Sometimes you need to test a subnet-subnet tunnel. This is a tunnel
 between two security gateways, which protects traffic on behalf of the
 subnets behind these gateways. On this network:</P>
<PRE>     Sunset==========West------------------East=========Sunrise
                     IPSec gateway         IPSec gateway
           local net       untrusted net       local net</PRE>
<P> you might name this tunnel sunset-sunrise. You can test this tunnel
 by having a machine behind one gateway ping a machine behind the other
 gateway, but this is not always convenient or even possible.</P>
<P>Simply pinging one gateway from the other is not useful. Such a ping
 does not normally go through the tunnel.<STRONG> The tunnel handles
 traffic between the two protected subnets, not between the gateways</STRONG>
 . Depending on the routing in place, a ping might</P>
<UL>
<LI>either succeed by finding an unencrypted route</LI>
<LI>or fail by finding no route. Packets without an IPSEC eroute are
 discarded.</LI>
</UL>
<P><STRONG>Neither event tells you anything about the tunnel</STRONG>.
 You can explicitly create an eroute to force such packets through the
 tunnel, or you can create additional tunnels as described in our<A HREF="#multitunnel">
 configuration document</A>, but those may be unnecessary complications
 in your situation.</P>
<P>The trick is to explicitly test between<STRONG> both gateways'
 private-side IP addresses</STRONG>. Since the private-side interfaces
 are on the protected subnets, the resulting packets do go via the
 tunnel. Use either ping -I or traceroute -i, both of which allow you to
 specify a source interface. (Note: unsupported on older Linuxes). The
 same principles apply for a road warrior (or other) case where only one
 end of your tunnel is a subnet.</P>
<H3><A NAME="ifconfig1"></A>5.3 ifconfig reports for KLIPS debugging</H3>
<P>When diagnosing problems using ifconfig statistics, you may wonder
 what type of activity increments a particular counter for an ipsecN
 device. Here's an index, posted by KLIPS developer Richard Guy Briggs:</P>
<PRE>Here is a catalogue of the types of errors that can occur for which
statistics are kept when transmitting and receiving packets via klips.
I notice that they are not necessarily logged in the right counter.
. . .

Sources of ifconfig statistics for ipsec devices

rx-errors:
- packet handed to ipsec_rcv that is not an ipsec packet.
- ipsec packet with payload length not modulo 4.
- ipsec packet with bad authenticator length.
- incoming packet with no SA.
- replayed packet.
- incoming authentication failed.
- got esp packet with length not modulo 8.

tx_dropped:
- cannot process ip_options.
- packet ttl expired.
- packet with no eroute.
- eroute with no SA.
- cannot allocate sk_buff.
- cannot allocate kernel memory.
- sk_buff internal error.


The standard counters are:

struct enet_statistics
{
        int        rx_packets;                /* total packets received */
        int        tx_packets;                /* total packets transmitted */
        int        rx_errors;                /* bad packets received */
        int        tx_errors;                /* packet transmit problems */
        int        rx_dropped;                /* no space in linux buffers */
        int        tx_dropped;                /* no space available in linux */
        int        multicast;                /* multicast packets received */
        int        collisions;

        /* detailed rx_errors: */
        int        rx_length_errors;
        int        rx_over_errors;                /* receiver ring buff overflow */
        int        rx_crc_errors;                /* recved pkt with crc error */
        int        rx_frame_errors;        /* recv'd frame alignment error */
        int        rx_fifo_errors;                /* recv'r fifo overrun */
        int        rx_missed_errors;        /* receiver missed packet */

        /* detailed tx_errors */
        int        tx_aborted_errors;
        int        tx_carrier_errors;
        int        tx_fifo_errors;
        int        tx_heartbeat_errors;
        int        tx_window_errors;
};

of which I think only the first 6 are useful.</PRE>
<H3><A NAME="gdb"></A> 5.4 Using GDB on Pluto</H3>
<P>You may need to use the GNU debugger, gdb(1), on Pluto. This should
 be necessary only in unusual cases, for example if you encounter a
 problem which the Pluto developer cannot readily reproduce or if you
 are modifying Pluto.</P>
<P>Here are the Pluto developer's suggestions for doing this:</P>
<PRE>Can you get a core dump and use gdb to find out what Pluto was doing
when it died?

To get a core dump, you will have to set dumpdir to point to a
suitable directory (see <A HREF="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</A>).

To get gdb to tell you interesting stuff:
        $ script
        $ cd dump-directory-you-chose
        $ gdb /usr/local/lib/ipsec/pluto core
        (gdb) where
        (gdb) quit
        $ exit

The resulting output will have been captured by the script command in
a file called &quot;typescript&quot;.  Send it to the list.

Do not delete the core file.  I may need to ask you to print out some
more relevant stuff.</PRE>
<P> Note that the<VAR> dumpdir</VAR> parameter takes effect only when
 the IPsec subsystem is restarted -- reboot or ipsec setup restart.</P>
<P>
<BR>
<BR></P>
<HR>
<H1><A name="compat">Linux FreeS/WAN Compatibility Guide</A></H1>
<P>Much of this document is quoted directly from the Linux FreeS/WAN<A href="mail.html">
 mailing list</A>. Thanks very much to the community of testers,
 patchers and commenters there, especially the ones quoted below but
 also various contributors we haven't quoted.</P>
<H2><A name="spec">Implemented parts of the IPsec Specification</A></H2>
<P>In general, do not expect Linux FreeS/WAN to do everything yet. This
 is a work-in-progress and some parts of the IPsec specification are not
 yet implemented.</P>
<H3><A name="in">In Linux FreeS/WAN</A></H3>
<P>Things we do, as of version 1.96:</P>
<UL>
<LI>key management methods
<DL>
<DT>manually keyed</DT>
<DD>using keys stored in /etc/ipsec.conf</DD>
<DT>automatically keyed</DT>
<DD>Automatically negotiating session keys as required. All connections
 are automatically re-keyed periodically. The<A href="#Pluto"> Pluto</A>
 daemon implements this using the<A href="#IKE"> IKE</A> protocol.</DD>
</DL>
</LI>
<LI>Methods of authenticating gateways for IKE
<DL>
<DT>shared secrets</DT>
<DD>stored in<A href="manpage.d/ipsec.secrets.5.html"> ipsec.secrets(5)</A>
</DD>
<DT><A href="#RSA">RSA</A> signatures</DT>
<DD>For details, see<A href="manpage.d/ipsec_pluto.8.html"> pluto(8)</A>
.</DD>
<DT>looking up RSA authentication keys from<A href="#DNS"> DNS</A>.</DT>
<DD>Note that this technique cannot be fully secure until<A href="#SDNS">
 secure DNS</A> is widely deployed.</DD>
</DL>
</LI>
<LI>groups for<A href="#DH"> Diffie-Hellman</A> key negotiation
<DL>
<DT>group 2, modp 1024-bit</DT>
<DT>group 5, modp 1536-bit</DT>
<DD>We implement these two groups.
<P>In negotiating a keying connection (ISAKMP SA, Phase 1) we propose
 both groups when we are the initiator, and accept either when a peer
 proposes them. Once the keying connection is made, we propose only the
 alternative agreed there for data connections (IPsec SA's, Phase 2)
 negotiated over that keying connection.</P>
</DD>
</DL>
</LI>
<LI>encryption transforms
<DL>
<DT><A href="#DES">DES</A></DT>
<DD>DES is in the source code since it is needed to implement 3DES, but
 single DES is not made available to users because<A href="#desnotsecure">
 DES is insecure</A>.</DD>
<DT><A href="#3DES">Triple DES</A></DT>
<DD>implemented, and used as the default encryption in Linux FreeS/WAN.</DD>
</DL>
</LI>
<LI>authentication transforms
<DL>
<DT><A href="#HMAC">HMAC</A> using<A href="#MD5"> MD5</A></DT>
<DD>implemented, may be used in IKE or by by AH or ESP transforms.</DD>
<DT><A href="#HMAC">HMAC</A> using<A href="#SHA"> SHA</A></DT>
<DD>implemented, may be used in IKE or by AH or ESP transforms.</DD>
</DL>
<P>In negotiations, we propose both of these and accept either.</P>
</LI>
<LI>compression transforms
<DL>
<DT>IPComp</DT>
<DD>IPComp as described in RFC 2393 was added for FreeS/WAN 1.6. Note
 that Pluto becomes confused if you ask it to do IPComp when the kernel
 cannot.</DD>
</DL>
</LI>
</UL>
<P>All combinations of implemented transforms are supported. Note that
 some form of packet-level<STRONG> authentication is required whenever
 encryption is used</STRONG>. Without it, the encryption will not be
 secure.</P>
<H3><A name="dropped">Deliberately omitted</A></H3>
 We do not implement everything in the RFCs because some of those things
 are insecure. See our discussions of avoiding<A href="#weak"> bogus
 security</A>.
<P>Things we deliberately omit which are required in the RFCs are:</P>
<UL>
<LI>null encryption (to use ESP as an authentication-only service)</LI>
<LI>single DES</LI>
<LI>DH group 1, a 768-bit modp group</LI>
</UL>
<P>Since these are the only encryption algorithms and DH group the RFCs
 require, it is possible in theory to have a standards-conforming
 implementation which will not interpoperate with FreeS/WAN. Such an
 implementation would be inherently insecure, so we do not consider this
 a problem.</P>
<P>Anyway, most implementations sensibly include more secure options as
 well, so dropping null encryption, single DES and Group 1 does not
 greatly hinder interoperation in practice.</P>
<P>We also do not implement some optional features allowed by the RFCs:</P>
<UL>
<LI>aggressive mode for negotiation of the keying channel or ISAKMP SA.
 This mode is a little faster than main mode, but exposes more
 information to an eavesdropper.</LI>
</UL>
<P>In theory, this should cause no interoperation problems since all
 implementations are required to support the more secure main mode,
 whether or not they also allow aggressive mode.</P>
<P>In practice, it does sometimes produce problems with implementations
 such as Windows 2000 where aggressive mode is the default. Typically,
 these are easily solved with a configuration change that overrides that
 default.</P>
<H3><A name="not">Not (yet) in Linux FreeS/WAN</A></H3>
<P>Things we don't yet do, as of version 1.96:</P>
<UL>
<LI>key management methods
<UL>
<LI>authenticate key negotiations via local<A href="#PKI"> PKI</A>
 server, but see links to user<A href="#patch"> patches</A></LI>
<LI>authenticate key negotiations via<A href="#SDNS"> secure DNS</A></LI>
<LI>unauthenticated key management, using<A href="#DH"> Diffie-Hellman</A>
 key agreement protocol without authentication. Arguably, this would be
 worth doing since it is secure against all passive attacks. On the
 other hand, it is vulnerable to an active<A href="#middle">
 man-in-the-middle attack</A>.</LI>
</UL>
</LI>
<LI>encryption transforms
<P>Currently<A href="#3DES"> Triple DES</A> is the only encryption
 method Pluto will negotiate.</P>
<P>No additional encryption transforms are implemented, though the RFCs
 allow them and some other IPsec implementations support various of
 them. We are not eager to add more. See this<A href="#other.cipher">
 FAQ question</A>.</P>
<P><A href="#AES">AES</A>, the successor to the DES standard, is an
 excellent candidate for inclusion in FreeS/WAN, see links to user<A href="#patch">
 patches</A>.</P>
</LI>
<LI>authentication transforms
<P>No optional additional authentication transforms are currently
 implemented. Likely<A href="#SHA-256"> SHA-256, SHA-384 and SHA-512</A>
 will be added when AES is.</P>
</LI>
<LI>Policy checking on decrypted packets
<P>To fully comply with the RFCs, it is not enough just to accept only
 packets which survive any firewall rules in place to limit what IPsec
 packets get in, and then pass KLIPS authentication. That is what
 FreeS/WAN currently does.</P>
<P>We should also apply additional tests, for example ensuring that all
 packets emerging from a particular tunnel have source and destination
 addresses that fall within the subnets defined for that tunnel, and
 that packets with those addresses that did not emerge from the
 appropriate tunnel are disallowed.</P>
<P>This will be done as part of a KLIPS rewrite. See these<A href="#applied">
 links</A> and the<A href="mail.html"> design mailing list</A> for
 discussion.</P>
</LI>
</UL>
<H2><A name="pfkey">Our PF-Key implementation</A></H2>
<P>We use PF-key Version Two for communication between the KLIPS kernel
 code and the Pluto Daemon. PF-Key v2 is defined by<A href="http://www.normos.org/ietf/rfc/rfc2367.txt">
 RFC 2367</A>.</P>
<P>The &quot;PF&quot; stands for Protocol Family. PF-Inet defines a
 kernel/userspace interface for the TCP/IP Internet protocols (TCP/IP),
 and other members of the PF series handle Netware, Appletalk, etc.
 PF-Key is just a PF for key-related matters.</P>
<H3><A name="pfk.port">PF-Key portability</A></H3>
<P>PF-Key came out of Berkeley Unix work and is used in the various BSD
 IPsec implementations, and in Solaris. This means there is some hope of
 porting our Pluto(8) to one of the BSD distributions, or of running
 their photurisd(8) on Linux if you prefer<A href="#photuris"> Photuris</A>
 key management over IKE.</P>
<P>It is, however, more complex than that. The PK-Key RFC deliberately
 deals only with keying, not policy management. The three PF-Key
 implementations we have looked at -- ours, OpenBSD and KAME -- all have
 extensions to deal with security policy, and the extensions are
 different. There have been discussions aimed at sorting out the
 differences, perhaps for a version three PF-Key spec. All players are
 in favour of this, but everyone involved is busy and it is not clear
 whether or when these discussions might bear fruit.</P>
<H2><A name="otherk">Kernels other than the latest 2.2.x and 2.4.y</A></H2>
<P>We develop and test on Redhat Linux using the most recent kernel in
 the 2.2 and 2.4 series. In general, we recommend you use the latest
 kernel in one of those series. Complications and caveats are discussed
 below.</P>
<H3><A name="kernel.2.0">2.0.x kernels</A></H3>
<P>Consider upgrading to the 2.2 kernel series. If you want to stay with
 the 2.0 series, then we strongly recommend 2.0.39. Some useful security
 patches were added in 2.0.38.</P>
<P>Various versions of the code have run at various times on most 2.0.xx
 kernels, but the current version is only lightly tested on 2.0.39, and
 not at all on older kernels.</P>
<P>Some of our patches for older kernels are shipped in 2.0.37 and
 later, so they are no longer provided in FreeS/WAN. This means recent
 versions of FreeS/WAN will probably not compile on anything earlier
 than 2.0.37.</P>
<H3><A name="kernel.production">2.2 and 2.4 kernels</A></H3>
<DL>
<DT>FreeS/WAN 1.0</DT>
<DD>ran only on 2.0 kernels</DD>
<DT>FreeS/WAN 1.1 to 1.8</DT>
<DD>ran on 2.0 or 2.2 kernels
<BR> ran on some development kernels, 2.3 or 2.4-test</DD>
<DT>FreeS/WAN 1.9 to 1.96</DT>
<DD>runs on 2.0, 2.2 or 2.4 kernels</DD>
</DL>
<P>In general,<STRONG> we suggest the latest 2.2 kernel or 2.4 for
 production use</STRONG>.</P>
<P>Of course no release can be guaranteed to run on kernels more recent
 than it is, so quite often there will be no stable FreeS/WAN for the
 absolute latest kernel. See the<A href="#k.versions"> FAQ</A> for
 discussion.</P>
<H2><A name="otherdist">Intel Linux distributions other than Redhat</A></H2>
<P>We develop and test on Redhat 6.1 for 2.2 kernels, and on Redhat 7.1
 or 7.2 for 2.4, so minor changes may be required for other
 distributions.</P>
<H3><A name="rh7">Redhat 7.0</A></H3>
<P>There are some problems with FreeS/WAN on Redhat 7.0. They are
 soluble, but we recommend you upgrade to a later Redhat instead..</P>
<P>Redhat 7 ships with two compilers.</P>
<UL>
<LI>Their<VAR> gcc</VAR> is version 2.96. Various people, including the
 GNU compiler developers and Linus, have said fairly emphatically that
 using this was a mistake. 2.96 is a development version, not intended
 for production use. In particular, it will not compile a Linux kernel.</LI>
<LI>Redhat therefore also ship a separate compiler, which they call<VAR>
 kgcc</VAR>, for compiling kernels.</LI>
</UL>
<P>Kernel Makefiles have<VAR> gcc</VAR> as a default, and must be
 adjusted to use<VAR> kgcc</VAR> before a kernel will compile on 7.0.
 This mailing list message gives details:</P>
<PRE>Subject: Re: AW: Installing IPsec on Redhat 7.0
   Date: Thu, 1 Feb 2001 14:32:52 -0200 (BRST)
  From: Mads Rasmussen &lt;mads@cit.com.br&gt;
 
&gt; From www.redhat.com/support/docs/gotchas/7.0/gotchas-7-6.html#ss6.1

cd to /usr/src/linux and open the Makefile in your favorite editor. You
will need to look for a line similar to this:

CC = $(CROSS_COMPILE)gcc -D__KERNEL__ -I$(HPATH)

This line specifies which C compiler to use to build the kernel. It should
be changed to:

CC = $(CROSS_COMPILE)kgcc -D__KERNEL__ -I$(HPATH)

for Red Hat Linux 7. The kgcc compiler is egcs 2.91.66. From here you can
proceed with the typical compiling steps.</PRE>
<P>Check the<A href="mail.html"> mailing list</A> archive for more
 recent news.</P>
<H3><A name="suse">SuSE Linux</A></H3>
<P>SuSE 6.3 and later versions, at least in Europe, ship with FreeS/WAN
 included.</P>
<P>FreeS/WAN packages distributed for SuSE 7.0-7.2 were somehow
 miscompiled. You can find fixed packages on<A HREF="http://www.suse.de/~garloff/linux/FreeSWAN">
 Kurt Garloff's page</A>.</P>
<P>Here are some notes for an earlier SuSE version.</P>
<H4><A NAME="9_4_2_1">SuSE Linux 5.3</A></H4>
<PRE>Date: Mon, 30 Nov 1998
From: Peter Onion &lt;ponion@srd.bt.co.uk&gt;

... I got Saturdays snapshot working between my two SUSE5.3 machines at home.

The mods to the install process are quite simple.  From memory and looking at
the files on the SUSE53 machine here at work....

And extra link in each of the /etc/init.d/rc?.d directories called K35ipsec
which SUSE use to shut a service down.

A few mods in /etc/init.d/ipsec  to cope with the different places that SUSE
put config info, and remove the inculsion of /etc/rc.d/init.d/functions and .
/etc/sysconfig/network as they don't exists and 1st one isn't needed anyway.

insert &quot;. /etc/rc.config&quot; to pick up the SUSE config info and use 

  if test -n &quot;$NETCONFIG&quot; -a &quot;$NETCONFIG&quot; != &quot;YAST_ASK&quot; ; then

to replace 

  [ ${NETWORKING} = &quot;no&quot; ] &amp;&amp; exit 0

Create /etc/sysconfig  as SUSE doesn't have one.

I think that was all (but I prob forgot something)....</PRE>
<P>You may also need to fiddle initialisation scripts to ensure that<VAR>
 /var/run/pluto.pid</VAR> is removed when rebooting. If this file is
 present, Pluto does not come up correctly.</P>
<H3><A name="slack">Slackware</A></H3>
<PRE>Subject: Re: linux-IPsec: Slackware distribution
  Date:  Thu, 15 Apr 1999 12:07:01 -0700
  From:  Evan Brewer &lt;dmessiah@silcon.com&gt;

&gt; Very shortly, I will be needing to install IPsec on at least gateways that
&gt; are running Slackware. . . .

The only trick to getting it up is that on the slackware dist there is no
init.d directory in /etc/rc.d .. so create one.  Then, what I do is take the
IPsec startup script which normally gets put into the init.d directory, and
put it in /etc/rc.d and name ir rc.ipsec .. then I symlink it to the file
in init.d.  The only file in the dist you need to really edit is the
utils/Makefile, setup4:

Everything else should be just fine.</PRE>
<P>A year or so later:</P>
<PRE>Subject: Re: HTML Docs- Need some cleanup?
   Date: Mon, 8 Jan 2001
   From: Jody McIntyre &lt;jodym@oeone.com&gt;

I have successfully installed FreeS/WAN on several Slackware 7.1 machines.
FreeS/WAN installed its rc.ipsec file in /etc/rc.d.  I had to manually call
this script from rc.inet2.  This seems to be an easier method than Evan
Brewer's.</PRE>
<H3><A name="deb">Debian</A></H3>
<P>A recent (Nov 2001) mailing list points to a<A href="http://www.thing.dyndns.org/debian/vpn.htm">
 web page</A> on setting up several types of tunnel, including IPsec, on
 Debian.</P>
<P>Some older information:</P>
<PRE>Subject: FreeS/WAN 1.0 on Debian 2.1
   Date: Tue, 20 Apr 1999
  From:  Tim Miller &lt;cerebus+counterpane@haybaler.sackheads.org&gt;

        Compiled and installed without error on a Debian 2.1 system
with kernel-source-2.0.36 after pointing RCDIR in utils/Makefile to
/etc/init.d.

        /var/lock/subsys/ doesn't exist on Debian boxen, needs to be
created; not a fatal error.

        Finally, IPsec scripts appear to be dependant on GNU awk
(gawk); the default Debian awk (mawk-1.3.3-2) had fatal difficulties.
With gawk installed and /etc/alternatives/awk linked to /usr/bin/gawk
operation appears flawless.</PRE>
<P>The scripts in question have been modified since this was posted. Awk
 versions should no longer be a problem.</P>
<H3><A name="caldera">Caldera</A></H3>
<PRE>Subject: Re: HTML Docs- Need some cleanup?
   Date: Mon, 08 Jan 2001
   From: Andy Bradford &lt;andyb@calderasystems.com&gt;

On Sun, 07 Jan 2001 22:59:05 EST, Sandy Harris wrote:

&gt;     Intel Linux distributions other than Redhat 5.x and 6.x 
&gt;         Redhat 7.0 
&gt;         SuSE Linux 
&gt;             SuSE Linux 5.3 
&gt;         Slackware 
&gt;         Debian 

Can you please include Caldera in this list?  I have tested it since 
FreeS/Wan 1.1 and it works great with our systems---provided one 
follows the FreeS/Wan documentation. :-)

Thank you,
Andy</PRE>
<H2><A name="CPUs">CPUs other than Intel</A></H2>
<P>FreeS/WAN has been run sucessfully on a number of different CPU
 architectures. If you have tried it on one not listed here, please post
 to the<A href="mail.html"> mailing list</A>.</P>
<H3><A name=" strongarm">Corel Netwinder (StrongARM CPU)</A></H3>
<PRE>Subject: linux-ipsec: Netwinder diffs
Date: Wed, 06 Jan 1999
From: rhatfield@plaintree.com

I had a mistake in my IPsec-auto, so I got things working this morning.

Following are the diffs for my changes.  Probably not the best and cleanest way 
of doing it, but it works. . . . </PRE>
<P>These diffs are in the 0.92 and later distributions, so these should
 work out-of-the-box on Netwinder.</P>
<H3><A name="yellowdog">Yellow Dog Linux on Power PC</A></H3>
<PRE>Subject:  Compiling FreeS/WAN 1.1 on YellowDog Linux (PPC)
   Date:  11 Dec 1999
   From:  Darron Froese &lt;darron@fudgehead.com&gt;

I'm summarizing here for the record - because it's taken me many hours to do
this (multiple times) and because I want to see IPsec on more linuxes than
just x86.

Also, I can't remember if I actually did summarize it before... ;-) I'm
working too many late hours.

That said - here goes.

1. Get your linux kernel and unpack into /usr/src/linux/ - I used 2.2.13.
&lt;http://www.kernel.org/pub/linux/kernel/v2.2/linux-2.2.13.tar.bz2&gt;

2. Get FreeS/WAN and unpack into /usr/src/freeswan-1.1
&lt;ftp://ftp.xs4all.nl/pub/crypto/freeswan/freeswan-1.1.tar.gz&gt;

3. Get the gmp src rpm from here:
&lt;ftp://ftp.yellowdoglinux.com//pub/yellowdog/champion-1.1/SRPMS/SRPMS/gmp-2.0.2-9a.src.rpm&gt;

4. Su to root and do this: rpm --rebuild gmp-2.0.2-9a.src.rpm

You will see a lot of text fly by and when you start to see the rpm
recompiling like this:

Executing: %build
+ umask 022
+ cd /usr/src/redhat/BUILD
+ cd gmp-2.0.2
+ libtoolize --copy --force
Remember to add `AM_PROG_LIBTOOL' to `configure.in'.
You should add the contents of `/usr/share/aclocal/libtool.m4' to
`aclocal.m4'.
+ CFLAGS=-O2 -fsigned-char
+ ./configure --prefix=/usr

Hit Control-C to stop the rebuild. NOTE: We're doing this because for some
reason the gmp source provided with FreeS/WAN 1.1 won't build properly on
ydl.

cd /usr/src/redhat/BUILD/
cp -ar gmp-2.0.2 /usr/src/freeswan-1.1/
cd /usr/src/freeswan-1.1/
rm -rf gmp
mv gmp-2.0.2 gmp

5. Open the freeswan Makefile and change the line that says:
KERNEL=$(b)zimage (or something like that) to
KERNEL=vmlinux

6. cd ../linux/

7. make menuconfig
Select an option or two and then exit - saving your changes.

8. cd ../freeswan-1.1/ ; make menugo

That will start the whole process going - once that's finished compiling,
you have to install your new kernel and reboot.

That should build FreeS/WAN on ydl (I tried it on 1.1).</PRE>
 And a later message on the same topic:
<PRE>Subject: Re: FreeS/WAN, PGPnet and E-mail
   Date: Sat, 22 Jan 2000
   From: Darron Froese &lt;darron@fudgehead.com&gt;

on 1/22/00 6:47 PM, Philip Trauring at philip@trauring.com wrote:

&gt; I have a PowerMac G3 ...

The PowerMac G3 can run YDL 1.1 just fine. It should also be able to run
FreeS/WAN 1.2patch1 with a couple minor modifications:

1. In the Makefile it specifies a bzimage for the kernel compile - you have
to change that to vmlinux for the PPC.

2. The gmp source that comes with FreeS/WAN (for whatever reason) fails to
compile. I have gotten around this by getting the gmp src rpm from here:

ftp://ftp.yellowdoglinux.com//pub/yellowdog/champion-1.1/SRPMS/SRPMS/gmp-2.0.2-9a.src.rpm

If you rip the source out of there - and place it where the gmp source
resides it will compile just fine.</PRE>
<P>FreeS/WAN no longer includes GMP source.</P>
<H3><A name="mklinux">Mklinux</A></H3>
<P>One user reports success on the Mach-based<STRONG> m</STRONG>icro<STRONG>
k</STRONG>ernel Linux.</P>
<PRE>Subject: Smiles on sparc and ppc
   Date: Fri, 10 Mar 2000
   From: Jake Hill &lt;jah@alien.bt.co.uk&gt;

You may or may not be interested to know that I have successfully built
FreeS/WAN on a number of non intel alpha architectures; namely on ppc
and sparc and also on osfmach3/ppc (MkLinux). I can report that it just
works, mostly, with few changes.</PRE>
<H3><A name="alpha">Alpha 64-bit processors</A></H3>
<PRE>Subject: IT WORKS (again) between intel &amp; alpha :-)))))
   Date: Fri, 29 Jan 1999
   From: Peter Onion &lt;ponion@srd.bt.co.uk&gt;

Well I'm happy to report that I've got an IPsec connection between by intel &amp; alpha machines again :-))

If you look back on this list to 7th of December I wrote...

-On 07-Dec-98 Peter Onion wrote:
-&gt; 
-&gt; I've about had enuf of wandering around inside the kernel trying to find out
-&gt; just what is corrupting outgoing packets...
-
-Its 7:30 in the evening .....
-
-I FIXED IT  :-))))))))))))))))))))))))))))))))
-
-It was my own fault :-((((((((((((((((((
-
-If you ask me very nicly I'll tell you where I was a little too over keen to
-change unsigned long int __u32 :-)  OPSE ...
-
-So tomorrow it will full steam ahead to produce a set of diffs/patches against
-0.91 
-
-Peter Onion.</PRE>
<P>In general (there have been some glitches), FreeS/WAN has been
 running on Alphas since then.</P>
<H3><A name="SPARC">Sun SPARC processors</A></H3>
<P>Several users have reported success with FreeS/WAN on SPARC Linux.
 Here is one mailing list message:</P>
<PRE>Subject: Smiles on sparc and ppc
   Date: Fri, 10 Mar 2000
   From: Jake Hill &lt;jah@alien.bt.co.uk&gt;

You may or may not be interested to know that I have successfully built
FreeS/WAN on a number of non intel alpha architectures; namely on ppc
and sparc and also on osfmach3/ppc (MkLinux). I can report that it just
works, mostly, with few changes.

I have a question, before I make up some patches. I need to hack
gmp/mpn/powerpc32/*.s to build them. Is this ok? The changes are
trivial, but could I also use a different version of gmp? Is it vanilla
here?

I guess my only real headache is from ipchains, which appears to stop
running when IPsec has been started for a while. This is with 2.2.14 on
sparc.</PRE>
<P>This message, from a different mailing list, may be relevant for
 anyone working with FreeS/WAN on Suns:</P>
<PRE>Subject: UltraSPARC DES assembler
   Date: Thu, 13 Apr 2000
   From: svolaf@inet.uni2.dk (Svend Olaf Mikkelsen)
     To: coderpunks@toad.com

An UltraSPARC assembler version of the LibDES/SSLeay/OpenSSL des_enc.c
file is available at http://inet.uni2.dk/~svolaf/des.htm.

This brings DES on UltraSPARC from slower than Pentium at the same
clock speed to significantly faster.</PRE>
<H3><A name="mips">MIPS processors</A></H3>
<P>We know FreeS/WAN runs on at least some MIPS processors because<A href="http://www.lasat.com">
 Lasat</A> manufacture an IPsec box based on an embedded MIPS running
 Linux with FreeS/WAN. We have no details.</P>
<H3><A name="crusoe">Transmeta Crusoe</A></H3>
<P>The Merilus<A href="http://www.merilus.com/products/fc/index.shtml">
 Firecard</A>, a Linux firewall on a PCI card, is based on a Crusoe
 processor and supports FreeS/WAN.</P>
<H3><A name="coldfire">Motorola Coldfire</A></H3>
<PRE>Subject: Re: Crypto hardware support
   Date: Mon, 03 Jul 2000
   From: Dan DeVault &lt;devault@tampabay.rr.com&gt;

.... I have been running
uClinux with FreeS/WAN 1.4 on a system built by Moreton Bay  (
http://www.moretonbay.com )  and it was using a Coldfire processor
and was able to do the Triple DES encryption at just about
1 mbit / sec rate.......  they put a Hi/Fn 7901 hardware encryption
chip on their board and now their system does over 25 mbit of 3DES
encryption........ pretty significant increase if you ask me.</PRE>
<H2><A name="multiprocessor">Multiprocessor machines</A></H2>
<P>FreeS/WAN is designed to work on SMP (symmetric multi-processing)
 Linux machines and is regularly tested on dual processor x86 machines.</P>
<P>We do not know of any testing on multi-processor machines with other
 CPU architectures or with more than two CPUs. Anyone who does test
 this, please report results to the<A href="mail.html"> mailing list</A>
.</P>
<P>The current design does not make particularly efficient use of
 multiprocessor machines; some of the kernel work is single-threaded.</P>
<H2><A name="hardware">Support for crypto hardware</A></H2>
<P>Supporting hardware cryptography accelerators has not been a high
 priority for the development team because it raises a number of fairly
 complex issues:</P>
<UL>
<LI>Can you trust the hardware? If it is not Open Source, how do you
 audit its security? Even if it is, how do you check that the design has
 no concealed traps?</LI>
<LI>If an interface is added for such hardware, can that interface be
 subverted or misused?</LI>
<LI>Is hardware acceleration actually a performance win? It clearly is
 in many cases, but on a fast machine it might be better to use the CPU
 for the encryption than to pay the overheads of moving data to and from
 a crypto board.</LI>
<LI>the current KLIPS code does not provide a clean interface for
 hardware accelerators</LI>
</UL>
<P>That said, we have a<A href="#coldfire"> report</A> of FreeS/WAN
 working with one crypto accelerator and some work is going on to modify
 KLIPS to create a clean generic interface to such products. See this<A href="http://www.jukie.net/~bart/linux-ipsec/">
 web page</A> for some of the design discussion.</P>
<P>More recently, a patch to support some hardware accelerators has been
 posted:</P>
<PRE>Subject: [Design] [PATCH] H/W acceleration patch
   Date: Tue, 18 Sep 2001
   From: &quot;Martin Gadbois&quot; &lt;martin.gadbois@colubris.com&gt;
 
Finally!!
Here's a web site with H/W acceleration patch for FreeS/WAN 1.91, including
S/W and Hifn 7901 crypto support.

http://sources.colubris.com/

Martin Gadbois</PRE>
<P>Hardware accelerators could take performance well beyond what
 FreeS/WAN can do in software (discussed<A href="performance.html"> here</A>
). Here is some discussion off the IETF IPsec list, October 2001:</P>
<PRE> ... Currently shipping chips deliver, 600 mbps throughput on a single
 stream of 3DES IPsec traffic.  There are also chips that use multiple
 cores to do 2.4 gbps.  We (Cavium) and others have announced even faster
 chips. ... Mid 2002 versions will handle at line rate (OC48 and OC192)
 IPsec and SSL/TLS traffic not only 3DES CBC but also AES and arc4.</PRE>
<P>The patches to date support chips that have been in production for
 some time, not the state-of-the-art latest-and-greatest devices
 described in that post. However, they may still outperform software and
 they almost certainly reduce CPU overhead.</P>
<H2><A name="ipv6">IP version 6 (IPng)</A></H2>
<P>The Internet currently runs on version four of the IP protocols. IPv4
 is what is in the standard Linux IP stack, and what FreeS/WAN was built
 for. In IPv4, IPsec is an optional feature.</P>
<P>The next version of the IP protocol suite is version six, usually
 abbreviated either as &quot;IPv6&quot; or as &quot;IPng&quot; for &quot;IP: the next
 generation&quot;. For IPv6, IPsec is a required feature. Any machine doing
 IPv6 is required to support IPsec, much as any machine doing (any
 version of) IP is required to support ICMP.</P>
<P>There is a Linux implementation of IPv6 in Linux kernels 2.2 and
 above. For details, see the<A href="http://www.cs-ipv6.lancs.ac.uk/ipv6/systems/linux/faq/">
 FAQ</A>. It does not yet support IPsec. The<A href="http://www.linux-ipv6.org/">
 USAGI</A> project are also working on IPv6 for Linux.</P>
<P>FreeS/WAN was originally built for the current standard, IPv4, but we
 are interested in seeing it work with IPv6. Some progress has been
 made, and a patched version with IPv6 support is<A href="http://www.ipv6.iabg.de/downloadframe/index.html">
 available</A>. For more recent information, check the<A href="mail.html">
 mailing list</A>.</P>
<H3><A name="v6.back">IPv6 background</A></H3>
<P>IPv6 has been specified by an IETF<A href="http://www.ietf.org/html.charters/ipngwg-charter.html">
 working group</A>. The group's page lists over 30 RFCs to date, and
 many Internet Drafts as well. The overview is<A href="http://www.ietf.org/rfc/rfc2460.txt">
 RFC 2460</A>. Major features include:</P>
<UL>
<LI>expansion of the address space from 32 to 128 bits,</LI>
<LI>changes to improve support for
<UL>
<LI>mobile IP</LI>
<LI>automatic network configuration</LI>
<LI>quality of service routing</LI>
<LI>...</LI>
</UL>
</LI>
<LI>improved security via IPsec</LI>
</UL>
<P>A number of projects are working on IPv6 implementation. A prominent
 Open Source effort is<A href="http://www.kame.net/"> KAME</A>, a
 collaboration among several large Japanese companies to implement IPv6
 for Berkeley Unix. Other major players are also working on IPv6. For
 example, see pages at:</P>
<UL>
<LI><A href="http://playground.sun.com/pub/ipng/html/ipng-main.html">Sun</A>
</LI>
<LI><A href="http://www.cisco.com/warp/public/732/ipv6/index.html">Cisco</A>
</LI>
<LI><A href="http://www.microsoft.com/windows2000/techinfo/howitworks/communications/networkbasics/IPv6.asp">
Microsoft</A></LI>
</UL>
<P>The<A href="http://www.6bone.net/"> 6bone</A> (IPv6 backbone) testbed
 network has been up for some time. There is an active<A href="http://www.ipv6.org/">
 IPv6 user group</A>.</P>
<P>One of the design goals for IPv6 was that it must be possible to
 convert from v4 to v6 via a gradual transition process. Imagine the
 mess if there were a &quot;flag day&quot; after which the entire Internet used
 v6, and all software designed for v4 stopped working. Almost every
 computer on the planet would need major software changes! There would
 be huge costs to replace older equipment. Implementers would be worked
 to death before &quot;the day&quot;, systems administrators and technical support
 would be completely swamped after it. The bugs in every implementation
 would all bite simultaneously. Large chunks of the net would almost
 certainly be down for substantial time periods. ...</P>
<P>Fortunately, the design avoids any &quot;flag day&quot;. It is therefore a
 little tricky to tell how quickly IPv6 will take over. The transition
 has certainly begun. For examples, see announcements from<A href="http://www.mailbase.ac.uk/lists/internet2/2000-03/0016.html">
 NTT</A> and<A href="http://www.vnunet.com/News/1102383"> Nokia</A>.
 However, it is not yet clear how quickly the process will gain
 momentum, or when it will be completed. Likely large parts of the
 Internet will remain with IPv4 for years to come.</P>
<HR>
<A NAME="interop"></A>
<H1><A NAME="10">Interoperating with FreeS/WAN</A></H1>
<P>The FreeS/WAN project needs you! We rely on the user community to
 keep up to date. Mail users@lists.freeswan.org with your interop
 success stories.</P>
<P><STRONG>Please note</STRONG>: Most of our interop examples feature
 Linux FreeS/WAN 1.x config files. You can convert them to 2.x files
 fairly easily with the patch in our<A HREF="#ipsec.conf_v2"> Upgrading
 Guide</A>.</P>
<H2><A NAME="10_1">Interop at a Glance</A></H2>
<TABLE BORDER="1">
<TR><TD>&nbsp;</TD><TD colspan="5">FreeS/WAN VPN</TD><TD>Road Warrior</TD><TD>
OE</TD></TR>
<TR><TD>&nbsp;</TD><TD>PSK</TD><TD>RSA Secret</TD><TD>X.509
<BR><SMALL><A HREF="#interoprules">(requires patch)</A></SMALL></TD><TD>
NAT-Traversal
<BR><SMALL><A HREF="#interoprules">(requires patch)</A></SMALL></TD><TD>
Manual
<BR>Keying</TD><TD>&nbsp;</TD><TD>&nbsp;</TD></TR>
<TR><TD colspan="8">More Compatible</TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#freeswan">FreeS/WAN</A><A NAME="freeswan.top"> &nbsp;</A></TD><TD>
<FONT color="#00cc00">Yes</FONT></TD><TD><FONT color="#00cc00">Yes</FONT>
</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD><FONT color="#00cc00">Yes</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#isakmpd">isakmpd (OpenBSD)</A><A NAME="isakmpd.top"> &nbsp;</A>
</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>
<FONT color="#cc0000">No&nbsp;&nbsp;&nbsp;&nbsp;</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#kame">Kame (FreeBSD,
<BR> NetBSD, MacOSX)
<BR> <SMALL>aka racoon</SMALL></A><A NAME="kame.top"> &nbsp;</A></TD><TD><FONT
color="#00cc00">Yes</FONT></TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>
<FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#mcafee">McAfee VPN
<BR><SMALL>was PGPNet</SMALL></A><A NAME="mcafee.top"> &nbsp;</A></TD><TD><FONT
color="#00cc00">Yes</FONT></TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>
<FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#microsoft">Microsoft
<BR> Windows 2000/XP</A><A NAME="microsoft.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD><FONT color="#cc0000">
No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#ssh">SSH Sentinel</A><A NAME="ssh.top"> &nbsp;</A></TD><TD><FONT
color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT>
</TD><TD><FONT color="#cccc00">Maybe</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#safenet">Safenet SoftPK
<BR>/SoftRemote</A><A NAME="safenet.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD><FONT color="#cc0000">
No</FONT></TD></TR>
<TR><TD colspan="8">Other</TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#6wind">6Wind</A><A NAME="6wind.top"> &nbsp;</A></TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
<FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#alcatel">Alcatel Timestep</A><A NAME="alcatel.top"> &nbsp;</A>
</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#apple">Apple Macintosh
<BR>System 10+</A><A NAME="apple.top"> &nbsp;</A></TD><TD><FONT color="#cccc00">
Maybe</FONT></TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD><FONT color="#cccc00">
Maybe</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#cccc00">Maybe</FONT></TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#ashleylaurent">AshleyLaurent
<BR> VPCom</A><A NAME="ashleylaurent.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT
color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#borderware">Borderware</A><A NAME="borderware.top"> &nbsp;</A>
</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD><TD><FONT color="#cc0000">
No</FONT></TD></TR>

<!--
http://www.cequrux.com/vpn-guides.php3
"coming soon" guide to connect with FreeS/WAN.
-->

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#checkpoint">Check Point FW-1/VPN-1</A><A NAME="checkpoint.top">
 &nbsp;</A></TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>
<FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#cisco">Cisco with 3DES</A><A NAME="cisco.top"> &nbsp;</A></TD><TD>
<FONT color="#00cc00">Yes</FONT></TD><TD><FONT color="#cccc00">Maybe</FONT>
</TD><TD>&nbsp;</TD><TD><FONT color="#cccc00">Maybe</FONT></TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#equinux">Equinux VPN Tracker
<BR> (for Mac OS X)</A><A NAME="equinux.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#cccc00">Maybe</FONT></TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#fsecure">F-Secure</A><A NAME="fsecure.top"> &nbsp;</A></TD><TD>
<FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#cccc00">
Maybe</FONT></TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#gauntlet">Gauntlet GVPN</A><A NAME="gauntlet.top"> &nbsp;</A>
</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">
No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#aix">IBM AIX</A><A NAME="aix.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#cccc00">Maybe</FONT></TD><TD>
&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#as400">IBM AS/400</A><A NAME="as400"> &nbsp;</A></TD><TD><FONT
color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#intel">Intel Shiva
<BR>LANRover/Net Structure</A><A NAME="intel.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT
color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#lancom">LanCom (formerly ELSA)</A><A NAME="lancom.top">
 &nbsp;</A></TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#linksys">Linksys</A><A NAME="linksys.top"> &nbsp;</A></TD><TD>
<FONT color="#cccc00">Maybe</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">
No</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>
<FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#lucent">Lucent</A><A NAME="lucent.top"> &nbsp;</A></TD><TD><FONT
color="#cccc00">Partial</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#netasq">Netasq</A><A NAME="netasq.top"> &nbsp;</A></TD><TD>
&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#netcelo">netcelo</A><A NAME="netcelo.top"> &nbsp;</A></TD><TD>
&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#netgear">Netgear fvs318</A><A NAME="netgear.top"> &nbsp;</A>
</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#netscreen">Netscreen 100
<BR>or 5xp</A><A NAME="netscreen.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#cccc00">
Maybe</FONT></TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#nortel">Nortel Contivity</A><A NAME="nortel.top"> &nbsp;</A>
</TD><TD><FONT color="#cccc00">Partial</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD><FONT color="#cccc00">Maybe</FONT></TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#radguard">RadGuard</A><A NAME="radguard.top"> &nbsp;</A></TD><TD>
<FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#raptor">Raptor</A><A NAME="raptor"> &nbsp;</A></TD><TD><FONT
color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#redcreek">Redcreek Ravlin</A><A NAME="redcreek.top"> &nbsp;</A>
</TD><TD><FONT color="#00cc00">Yes</FONT><FONT color="#cccc00">/Partial</FONT>
</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">
No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#sonicwall">SonicWall</A><A NAME="sonicwall.top"> &nbsp;</A></TD><TD>
<FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT
color="#cccc00">Maybe</FONT></TD><TD><FONT color="#cc0000">No</FONT></TD><TD>
<FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#sun">Sun Solaris</A><A NAME="sun.top"> &nbsp;</A></TD><TD><FONT
color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT>
</TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT
color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#symantec">Symantec</A><A NAME="symantec.top"> &nbsp;</A></TD><TD>
<FONT color="#00cc00">Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>
&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#watchguard">Watchguard
<BR> Firebox</A><A NAME="watchguard.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD><FONT color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#xedia">Xedia Access Point
<BR>/QVPN</A><A NAME="xedia.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT
color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
<TR><TD><A HREF="#zyxel">Zyxel Zywall
<BR>/Prestige</A><A NAME="zyxel.top"> &nbsp;</A></TD><TD><FONT color="#00cc00">
Yes</FONT></TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD>&nbsp;</TD><TD><FONT
color="#cc0000">No</FONT></TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE


<TR>
<TD><A HREF="#sample">sample</A></TD>
<TD>&nbsp;</TD>
<TD>&nbsp;</TD>
<TD>&nbsp;</TD>
<TD>&nbsp;</TD>
<TD>&nbsp;</TD>
<TD>&nbsp;</TD>
<TD><FONT color="#cc0000">No</FONT></TD>
</TR>

-->
<TR><TD>&nbsp;</TD><TD>PSK</TD><TD>RSA Secret</TD><TD>X.509
<BR><SMALL><A HREF="#interoprules">(requires patch)</A></SMALL></TD><TD>
NAT-Traversal
<BR><SMALL><A HREF="#interoprules">(requires patch)</A></SMALL></TD><TD>
Manual
<BR>Keying</TD><TD>&nbsp;</TD><TD>&nbsp;</TD></TR>
<TR><TD>&nbsp;</TD><TD colspan="5">FreeS/WAN VPN</TD><TD>Road Warrior</TD><TD>
OE</TD></TR>

<!-- PSK  RSA  X.509  NAT-T  Manual  RW  OE -->
</TABLE>
<H3><A NAME="10_1_1">Key</A></H3>
<TABLE BORDER="1">
<TR><TD><FONT color="#00cc00">Yes</FONT></TD><TD>People report that this
 works for them.</TD></TR>
<TR><TD>[Blank]</TD><TD>We don't know.</TD></TR>
<TR><TD><FONT color="#cc0000">No</FONT></TD><TD>We have reason to
 believe it was, at some point, not possible to get this to work.</TD></TR>
<TR><TD><FONT color="#cccc00">Partial</FONT></TD><TD>Partial success.
 For example, a connection can be created from one end only.</TD></TR>
<TR><TD><FONT color="#00cc00">Yes</FONT><FONT color="#cccc00">/Partial</FONT>
</TD><TD>Mixed reports.</TD></TR>
<TR><TD><FONT color="#cccc00">Maybe</FONT></TD><TD>We think the answer
 is &quot;yes&quot;, but need confirmation.</TD></TR>
</TABLE>
<A NAME="interoprules"></A>
<H2><A NAME="10_2">Basic Interop Rules</A></H2>
<P>Vanilla FreeS/WAN implements<A HREF="#compat"> these parts</A> of the
 IPSec specifications. You can add more with<A HREF="http://www.freeswan.ca">
 Super FreeS/WAN</A>, but what we offer may be enough for many users.</P>
<UL>
<LI> To use X.509 certificates with FreeS/WAN, you will need the<A HREF="http://www.strongsec.org/freeswan">
 X.509 patch</A> or<A HREF="http://www.freeswan.ca"> Super FreeS/WAN</A>
, which includes that patch.</LI>
<LI> To use<A HREF="#NAT.gloss"> Network Address Translation</A> (NAT)
 traversal with FreeS/WAN, you will need Arkoon Network Security's<A HREF="http://open-source.arkoon.net">
 NAT traversal patch</A> or<A HREF="http://www.freeswan.ca"> Super
 FreeS/WAN</A>, which includes it.</LI>
</UL>
<P>We offer a set of proposals which is not user-adjustable, but covers
 all combinations that we can offer. FreeS/WAN always proposes triple
 DES encryption and Perfect Forward Secrecy (PFS). In addition, we
 propose Diffie Hellman groups 5 and 2 (in that order), and MD5 and
 SHA-1 hashes. We accept the same proposals, in the same order of
 preference.</P>
<P>Other interop notes:</P>
<UL>
<LI> A<A HREF="http://lists.freeswan.org/archives/users/2003-September/msg00462.html">
 SHA-1 bug in FreeS/WAN 2.00, 2.01 and 2.02</A> may affect some interop
 scenarios. It does not affect 1.x versions, and is fixed in 2.03 and
 later.</LI>
<LI> Some other implementations will close a connection with FreeS/WAN
 after some time. This may be a problem with rekey lifetimes. Please see<A
HREF="http://lists.freeswan.org/archives/users/2003-October/msg00293.html">
 this tip</A> and<A HREF="http://lists.freeswan.org/pipermail/users/2001-December/005758.html">
 this workaround</A>.</LI>
</UL>
<H2><A NAME="10_3">Longer Stories</A></H2>
<H3><A NAME="10_3_1">For<EM> More Compatible</EM> Implementations</A></H3>
<H4><A NAME="freeswan">FreeS/WAN</A></H4>
<P> See our documentation at<A HREF="http://www.freeswan.org">
 freeswan.org</A> and the Super FreeS/WAN docs at<A HREF="http://www.freeswan.ca">
 freeswan.ca</A>. Some user-written HOWTOs for FreeS/WAN-FreeS/WAN
 connections are listed in<A HREF="#howto"> our Introduction</A>.</P>
<P>See also:</P>
<UL>
<LI><A HREF="http://lugbe.ch/action/reports/ipsec_htbe.phtml"> A German
 FreeS/WAN-FreeS/WAN page by Markus Wernig (X.509)</A></LI>
</UL>
<P><A HREF="#freeswan.top">Back to chart</A></P>
<H4><A NAME="isakmpd">isakmpd (OpenBSD)</A></H4>
<P><A HREF="http://www.openbsd.org/faq/faq13.html">OpenBSD FAQ: Using
 IPsec</A>
<BR><A HREF="http://www.rommel.stw.uni-erlangen.de/~hshoexer/ipsec-howto/HOWTO.html">
 Hans-Joerg Hoexer's interop Linux-OpenBSD (PSK)</A>
<BR><A HREF="http://www.segfault.net/ipsec/"> Skyper's configuration
 (PSK)</A>
<BR><A HREF="http://www.hsc.fr/ressources/ipsec/ipsec2001/#config">
 French page with configs (X.509)</A></P>
<P><A HREF="#isakmpd.top">Back to chart</A></P>
<H4><A NAME="kame">Kame</A></H4>
<UL>
<LI>For FreeBSD and NetBSD. Ships with Mac OS X; see also our<A HREF="#apple">
 Mac</A> section.</LI>
<LI>Also known as<EM> racoon</EM>, its keying daemon.</LI>
</UL>
<P><A HREF="http://www.kame.net">Kame homepage, with FAQ</A>
<BR><A HREF="http://www.netbsd.org/Documentation/network/ipsec">
 NetBSD's IPSec FAQ</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/12/msg00560.html">
 Ghislaine's post explaining some interop peculiarities</A></P>
<P><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/09/msg00511.html">
 Itojun's Kame-FreeS/WAN interop tips (PSK)</A>
<BR><A HREF="http://www.hsc.fr/ressources/ipsec/ipsec2000"> Ghislaine
 Labouret's French page with links to matching FreeS/WAN and Kame
 configs (RSA)</A>
<BR><A HREF="http://lugbe.ch/lostfound/contrib/freebsd_router/"> Markus
 Wernig's HOWTO (X.509, BSD gateway)</A>
<BR><A HREF="http://web.morgul.net/~frodo/docs/kame+freeswan_interop.html">
 Frodo's Kame-FreeS/WAN interop (X.509)</A>
<BR><A HREF="http://www.wavesec.org/kame.phtml"> Kame as a WAVEsec
 client.</A></P>
<P><A HREF="#kame.top">Back to chart</A></P>
<H4><A NAME="mcafee">PGPNet/McAfee</A></H4>
<P></P>
<UL>
<LI>Now called McAfee VPN Client.</LI>
<LI>PGPNet also came in a freeware version which did not support subnets</LI>
<LI>To support dhcp-over-ipsec, you need the X.509 patch, which is
 included in<A HREF="http://www.freeswan.ca"> Super FreeS/WAN</A>.</LI>
</UL>
<P><A HREF="http://www.freeswan.ca/docs/WindowsInterop"> Tim Carr's
 Windows Interop Guide (X.509)</A>
<BR><A HREF="http://www.rommel.stw.uni-erlangen.de/~hshoexer/ipsec-howto/HOWTO.html#Interop2">
 Hans-Joerg Hoexer's Guide for Linux-PGPNet (PSK)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/04/msg00339.html">
 Kai Martius' instructions using RSA Key-Extractor Tool (RSA)</A>
<BR> &nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://www.zengl.net/freeswan/english.html">Christian
 Zeng's page (RSA)</A> based on Kai's work. English or German.
<BR><A HREF="http://tirnanog.ls.fi.upm.es/CriptoLab/Biblioteca/InfTech/InfTech_CriptoLab.htm">
 Oscar Delgado's PDF (X.509, no configs)</A>
<BR><A HREF="http://www-ec.njit.edu/~rxt1077/Howto.txt"> Ryan's HOWTO
 for FreeS/WAN-PGPNet (X.509)</A>. Through a Linksys Router with IPsec
 Passthru enabled.
<BR><A HREF="http://jixen.tripod.com/#RW-PGP-to-Fwan"> Jean-Francois
 Nadeau's Practical Configuration (Road Warrior with PSK)</A>
<BR><A HREF="http://www.evolvedatacom.nl/freeswan.html#toc"> Wouter
 Prins' HOWTO (Road Warrior with X.509)</A>
<BR></P>
<P><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/01/msg00271.html">
 Rekeying problem with FreeS/WAN and older PGPNets</A>
<BR></P>
<P><A HREF="http://www.strongsec.com/freeswan/dhcprelay/index.htm"> DHCP
 over IPSEC HOWTO for FreeS/WAN (requires X.509 and dhcprelay patches)</A>
</P>
<P><A HREF="#mcafee.top">Back to chart</A></P>
<H4><A NAME="microsoft">Microsoft Windows 2000/XP</A></H4>
<UL>
<LI>IPsec comes with Win2k, and with XP Support Tools. May require<A HREF="http://www.microsoft.com/windows2000/downloads/recommended/encryption/default.asp">
 High Encryption Pack</A>. WinXP users have also reported better results
 with Service Pack 1.</LI>
<LI>The Road Warrior setup works either way round. Windows (XP or 2K)
 IPsec can connect as a Road Warrior to FreeS/WAN. However, FreeS/WAN
 can also successfully connect as a Road Warrior to Windows IPsec (see
 Nate Carlson's configs below).</LI>
<LI>FreeS/WAN version 1.92 or later is required to avoid an
 interoperation problem with Windows native IPsec. Earlier FreeS/WAN
 versions did not process the Commit Bit as Windows native IPsec
 expected.</LI>
</UL>
<P><A HREF="http://www.freeswan.ca/docs/WindowsInterop"> Tim Carr's
 Windows Interop Guide (X.509)</A>
<BR><A HREF="http://ipsec.math.ucla.edu/services/ipsec.html"> James
 Carter's instructions (X.509, NAT-T)</A>
<BR><A HREF="http://jixen.tripod.com/#Win2000-Fwan"> Jean-Francois
 Nadeau's Net-net Configuration (PSK)</A>
<BR><A HREF="http://security.nta.no/freeswan-w2k.html"> Telenor's
 Node-node Config (Transport-mode PSK)</A>
<BR><A HREF="http://vpn.ebootis.de"> Marcus Mueller's HOWTO using his
 VPN config tool (X.509).</A> Tool also works with PSK.
<BR><A HREF="http://www.natecarlson.com/include/showpage.php?cat=linux&page=ipsec-x509">
 Nate Carlson's HOWTO using same tool (Road Warrior with X.509)</A>.
 Unusually, FreeS/WAN is the Road Warrior here.
<BR><A HREF="http://tirnanog.ls.fi.upm.es/CriptoLab/Biblioteca/InfTech/InfTech_CriptoLab.htm">
 Oscar Delgado's PDF (X.509, no configs)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2003-July/022425.html">
 Tim Scannell's Windows XP Additional Checklist (X.509)</A>
<BR></P>

<!-- Note to self: Include L2TP references? -->
<P><A HREF="http://www.microsoft.com/windows2000/en/server/help/default.asp?url=/windows2000/en/server/help/sag_TCPIP_ovr_secfeatures.htm">
 Microsoft's page on Win2k TCP/IP security features</A>
<BR><A HREF="http://support.microsoft.com/support/kb/articles/Q257/2/25.ASP">
 Microsoft's Win2k IPsec debugging tips</A>
<BR>
<!-- Alt-URL http://support.microsoft.com/default.aspx?scid=kb;EN-US;q257225
Perhaps newer? -->
<A HREF="http://www.wired.com/news/technology/0,1282,36336,00.html">
 MS VPN may fall back to 1DES</A></P>
<P><A HREF="#microsoft.top">Back to chart</A></P>
<H4><A NAME="ssh">SSH Sentinel</A></H4>
<UL>
<LI>Popular and well tested.</LI>
<LI>Also rebranded in<A HREF="http://www.zyxel.com"> Zyxel Zywall</A>.
 Our Zyxel interop notes are<A HREF="#zyxel"> here</A>.</LI>
<LI> SSH supports IPsec-over-UDP NAT traversal.</LI>
<LI>There is this<A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/12/msg00370.html">
 potential problem</A> if you're not using the Legacy Proposal option.</LI>
</UL>
<P><A HREF="http://www.ssh.com/support/sentinel/documents.cfm"> SSH's
 Sentinel-FreeSWAN interop PDF (X.509)</A>
<BR><A HREF="http://www.nadmm.com/show.php?story=articles/vpn.inc">
 Nadeem Hassan's SUSE-to-Sentinel article (Road warrior with X.509)</A>
<BR><A HREF="http://www.zerozone.it/documents/Linux/HowTo/VPN-IPsec-Freeswan-HOWTO.html">
 O-Zone's Italian HOWTO (Road Warrior, X.509, DHCP)</A>
<BR></P>
<P><A HREF="#ssh.top">Back to chart</A></P>
<H4><A NAME="safenet">Safenet SoftPK/SoftRemote</A></H4>
<UL>
<LI>People recommend SafeNet as a low cost Windows client.</LI>
<LI>SoftRemote seems to be the newer name for SoftPK.</LI>
</UL>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2001-November/005061.html">
 Whit Blauvelt's SoftRemote tips</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-October/015591.html">
 Tim Wilson's tips (X.509)</A><A HREF="http://lists.freeswan.org/archives/users/2003-October/msg00607.html">
 Workaround for a &quot;gotcha&quot;</A></P>
<P><A HREF="http://jixen.tripod.com/#Rw-IRE-to-Fwan"> Jean-Francois
 Nadeau's Practical Configuration (Road Warrior with PSK)</A>
<BR><A HREF="http://www.terradoncommunications.com/security/whitepapers/safe_net-to-free_swan.pdf">
 Terradon Communications' PDF (Road Warrior with PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-October/?????.html">
 Seaan.net's PDF (Road Warrior to Subnet, with PSK)</A>
<BR><A HREF="http://www.redbaronconsulting.com/freeswan/fswansafenet.pdf">
 Red Baron Consulting's PDF (Road Warrior with X.509)</A></P>
<P><A HREF="#safenet.top">Back to chart</A></P>
<H3><A NAME="10_3_2">For<EM> Other Implementations</EM></A></H3>
<H4><A NAME="6wind">6Wind</A></H4>
<P><A HREF="http://www.hsc.fr/ressources/ipsec/ipsec2001/#config">
 French page with configs (X.509)</A></P>
<P><A HREF="#6wind.top">Back to chart</A></P>
<H4><A NAME="alcatel">Alcatel Timestep</A></H4>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2002-June/011878.html">
 Alain Sabban's settings (PSK or PSK road warrior; through static NAT)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/1999/06/msg00100.html">
 Derick Cassidy's configs (PSK)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/1999/08/msg00194.html">
 David Kerry's Timestep settings (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-August/013711.html">
 Kevin Gerbracht's ipsec.conf (X.509)</A></P>
<P><A HREF="#alcatel.top">Back to chart</A></P>
<H4><A NAME="apple">Apple Macintosh System 10+</A></H4>
<UL>
<LI>Since the system is based on FreeBSD, this should interoperate<A HREF="#kame">
 just like FreeBSD</A>.</LI>
<LI> To use Appletalk over IPsec tunnels,<A HREF="http://lists.freeswan.org/pipermail/users/2001-November/005116.html">
 run it over TCP/IP</A>, or use Open Door Networks' Shareway IP tool,<A HREF="http://lists.freeswan.org/pipermail/users/2001-November/005426.html">
 described here.</A></LI>
<LI>See also the<A HREF="#equinux"> Equinux VPN Tracker</A> for Mac OS
 X.</LI>
</UL>
<P><A HREF="http://ipsec.math.ucla.edu/services/ipsec.html"> James
 Carter's instructions (X.509, NAT-T)</A></P>
<P><A HREF="#apple.top">Back to chart</A></P>
<H4><A NAME="ashleylaurent">AshleyLaurent VPCom</A></H4>
<P><A HREF="http://www.ashleylaurent.com/newsletter/01-28-00.htm">
 Successful interop report, no details</A></P>
<P><A HREF="#ashleylaurent.top">Back to chart</A></P>
<H4><A NAME="borderware">Borderware</A></H4>
<UL>
<LI>I suspect the Borderware client is a rebranded Safenet. If that's
 true, our<A HREF="#safenet"> Safenet section</A> will help.</LI>
</UL>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2002-March/008288.html">
 Philip Reetz' configs (PSK)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/09/msg00217.html">
 Borderware server does not support FreeS/WAN road warriors</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-February/007733.html">
 Older Borderware may not support Diffie Hellman groups 2, 5</A>
<BR></P>
<P><A HREF="#borderware.top">Back to chart</A></P>
<H4><A NAME="checkpoint">Check Point VPN-1 or FW-1</A></H4>
<UL>
<LI><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/02/msg00099.html">
 Caveat about IP-range inclusion on Check Point.</A></LI>
<LI> Some versions of Check Point may require an aggressive mode patch
 to interoperate with FreeS/WAN.
<BR><A HREF="http://www.freeswan.ca/code/super-freeswan"> Super
 FreeS/WAN</A> now features this patch.
<!--
<A HREF="http://www.freeswan.ca/patches/aggressivemode">Steve Harvey's 
aggressive mode patch for FreeS/WAN 1.5</A>
-->
</LI>
<LI></LI>
<LI>A Linux FreeS/WAN-Checkpoint connection may close after some time.
 Try<A HREF="http://lists.freeswan.org/archives/users/2003-October/msg00293.html">
 this tip</A> toward a workaround.</LI>
</UL>
<P><A HREF="http://www.fw-1.de/aerasec/ng/vpn-freeswan/CPNG+Linux-FreeSWAN.html">
 AERAsec's Firewall-1 NG site (PSK, X.509, Road Warrior with X.509,
 other algorithms)</A>
<BR> &nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://www.fw-1.de/aerasec/ng/vpn-freeswan/CPNG+Linux-FreeSWAN.html#support-matrix">
 AERAsec's detailed Check Point-FreeS/WAN support matrix</A>
<BR><A HREF="http://support.checkpoint.com/kb/docs/public/firewall1/4_1/pdf/fw-linuxvpn.pdf">
 Checkpoint.com PDF: Linux as a VPN Client to FW-1 (PSK)</A>
<BR><A HREF="http://www.phoneboy.com"> PhoneBoy's Check Point FAQ (on
 Check Point only, not FreeS/WAN)</A>
<BR></P>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2001-August/002351.html">
 Chris Harwell's tips FreeS/WAN configs (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-April/009362.html">
 Daniel Tombeil's configs (PSK)</A></P>
<P><A HREF="#checkpoint.top">Back to chart</A></P>
<H4><A NAME="cisco">Cisco</A></H4>
<UL>
<LI> Cisco supports IPsec-over-UDP NAT traversal.</LI>
<LI>Cisco VPN Client appears to use nonstandard IPsec and does not work
 with FreeS/WAN.<A HREF="https://mj2.freeswan.org/archives/2003-August/maillist.html">
 This message</A> concerns Cisco VPN Client 4.01.
<!-- fix link -->
</LI>
<LI>A Linux FreeS/WAN-Cisco connection may close after some time.<A HREF="http://lists.freeswan.org/pipermail/users/2001-December/005758.html">
 Here</A> is a workaround, and<A HREF="http://lists.freeswan.org/archives/users/2003-October/msg00293.html">
 here</A> is another comment on the same subject.</LI>
<LI><A HREF="http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120t/120t2/3desips.htm">
Older Ciscos</A> purchased outside the United States may not have 3DES,
 which FreeS/WAN requires.</LI>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2001-June/000406.html">
RSA keying may not be possible between Cisco and FreeS/WAN.</A></LI>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2001-October/004357.html">
In ipsec.conf, VPN3000 DN (distinguished name) must be in binary (X.509
 only)</A></LI>
</UL>
<P><A HREF="http://rr.sans.org/encryption/cisco_router.php"> SANS
 Institute HOWTO (PSK).</A> Detailed, with extensive references.
<BR><A HREF="http://www.worldbank.ro/IPSEC/cisco-linux.txt"> Short HOWTO
 (PSK)</A>
<BR><A HREF="http://www.hsc.fr/ressources/ipsec/ipsec2001/#config">
 French page with configs for Cisco IOS, PIX and VPN 3000 (X.509)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2001-August/002966.html">
 Dave McFerren's sample configs (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2001-September/003422.html">
 Wolfgang Tremmel's sample configs (PSK road warrior)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/11/msg00578.html">
 Old doc from Pete Davis, with William Watson's updated Tips (PSK)</A>
<BR></P>
<P><STRONG>Some PIX specific information:</STRONG>
<BR><A HREF="http://www.wlug.org.nz/FreeSwanToCiscoPix"> Waikato Linux
 Users' Group HOWTO. Nice detail (PSK)</A>
<BR><A HREF="http://www.johnleach.co.uk/documents/freeswan-pix/freeswan-pix.html">
 John Leach's configs (PSK)</A>
<BR><A HREF="http://www.diverdown.cc/vpn/freeswanpix.html"> Greg
 Robinson's settings (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-February/007901.html">
 Scott's ipsec.conf for PIX (PSK, FreeS/WAN side only)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2001-October/003949.html">
 Rick Trimble's PIX and FreeS/WAN settings (PSK)</A>
<BR></P>
<P><A href="http://www.cisco.com/public/support/tac"> Cisco VPN support
 page</A>
<BR><A href="http://www.ieng.com/warp/public/707/index.shtml#ipsec">
 Cisco IPsec information page</A></P>
<P><A HREF="#cisco.top">Back to chart</A></P>
<H4><A NAME="equinux">Equinux VPN tracker (for Mac OS X)</A></H4>
<UL>
<LI>Graphical configurator for Mac OS X IPsec. May be an interface to
 the<A HREF="#apple"> native Mac OS X IPsec</A>, which is essentially<A HREF="#kame">
 KAME</A>.</LI>
<LI>To use Appletalk over IPsec tunnels,<A HREF="http://lists.freeswan.org/pipermail/users/2001-November/005116.html">
 run it over TCP/IP</A>, or use Open Door Networks' Shareway IP tool,<A HREF="http://lists.freeswan.org/pipermail/users/2001-November/005426.html">
 described here.</A></LI>
</UL>
<P> Equinux provides<A HREF="http://www.equinux.com/download/HowTo_FreeSWAN.pdf">
 this excellent interop PDF</A> (PSK, RSA, X.509).</P>
<P><A HREF="#equinux.top">Back to chart</A></P>
<H4><A NAME="fsecure">F-Secure</A></H4>
<UL>
<LI>
<!-- <A HREF="http://lists.freeswan.org/pipermail/users/2002-February/007596.html"> -->
 F-Secure supports IPsec-over-UDP NAT traversal.</LI>
</UL>
<P><A HREF="http://www.pingworks.de/tech/vpn/vpn.txt">pingworks.de's
 &quot;Connecting F-Secure's VPN+ to Linux FreeS/WAN&quot; (PSK road warrior)</A>
<BR> &nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://www.pingworks.de/tech/vpn/vpn.pdf">Same thing
 as PDF</A>
<BR><A HREF="http://www.exim.org/pipermail/linux-ipsec/Week-of-Mon-20010122/000061.html">
 Success report, no detail (PSK)</A>
<BR><A HREF="http://www.exim.org/pipermail/linux-ipsec/Week-of-Mon-20010122/000041.html">
 Success report, no detail (Manual)</A></P>

<!-- Other NAT traversers:
http://lists.freeswan.org/pipermail/users/2002-April/009136.html
and ssh sentinel:
http://lists.freeswan.org/pipermail/users/2001-September/003108.html
-->
<P><A HREF="#fsecure.top">Back to chart</A></P>
<H4><A NAME="gauntlet">Gauntlet GVPN</A></H4>
<P><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/11/msg00535.html">
 Richard Reiner's ipsec.conf (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-June/011434.html">
 Might work without that pesky firewall... (PSK)</A>
<BR>
<!-- insert archive link -->
 In late July, 2003 Alexandar Antik reported success interoperating
 with Gauntlet 6.0 for Solaris (X.509). Unfortunately the message is not
 properly archived at this time.</P>
<P><A HREF="#gauntlet.top">Back to chart</A></P>
<H4><A NAME="aix">IBM AIX</A></H4>
<P><A HREF="http://www-1.ibm.com/servers/esdd/articles/security.html">
 IBM's &quot;Built-In Network Security with AIX&quot; (PSK, X.509)</A>
<BR><A HREF="http://www-1.ibm.com/servers/aix/products/ibmsw/security/vpn/faqandtips/#ques20">
 IBM's tip: importing Linux FreeS/WAN settings into AIX's<VAR> ikedb</VAR>
 (PSK)</A></P>
<P><A HREF="#aix.top">Back to chart</A></P>
<H4><A NAME="as400">IBM AS/400</A></H4>
<UL>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2002-April/009106.html">
 Road Warriors may act flaky</A>.</LI>
</UL>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2002-September/014264.html">
 Richard Welty's tips and tricks</A>
<BR></P>
<P><A HREF="#as400.top">Back to chart</A></P>
<H4><A NAME="intel">Intel Shiva LANRover / Net Structure</A></H4>
<UL>
<LI>Intel Shiva LANRover is now known as Intel Net Structure.</LI>
<LI><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/01/msg00298.html">
 Shiva seems to have two modes: IPsec or the proprietary &quot;Shiva Tunnel&quot;.</A>
 Of course, FreeS/WAN will only create IPsec tunnels.</LI>
<LI><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/02/msg00293.html">
 AH may not work for Shiva-FreeS/WAN.</A> That's OK, since FreeS/WAN has
 phased out the use of AH.</LI>
</UL>
<P><A HREF="http://snowcrash.tdyc.com/freeswan/"> Snowcrash's configs
 (PSK)</A>
<BR><A HREF="http://www.opus1.com/vpn/index.html"> Old configs from an
 interop (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2001-October/003831.html">
 The day Shiva tickled a Pluto bug (PSK)</A>
<BR> &nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://lists.freeswan.org/pipermail/users/2001-October/004270.html">
 Follow up: success!</A></P>
<P><A HREF="#intel.top">Back to chart</A></P>
<H4><A NAME="lancom">LanCom (formerly ELSA)</A></H4>
<UL>
<LI>This router is popular in Germany.</LI>
</UL>
<P> Jakob Curdes successfully created a PSK connection with the LanCom
 1612 in August 2003.
<!-- add ML link when it appears -->
</P>
<P><A HREF="#lancom.top">Back to chart</A></P>
<H4><A NAME="linksys">Linksys</A></H4>
<UL>
<LI>Linksys may be used as an IPsec tunnel endpoint,<STRONG> OR</STRONG>
 as a router in &quot;IPsec passthrough&quot; mode, so that the IPsec tunnel
 passes through the Linksys.</LI>
</UL>
<H5>As tunnel endpoint</H5>
<P><A HREF="http://www.freeswan.ca/docs/BEFVP41/"> Ken Bantoft's
 instructions (Road Warrior with PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-February/007814.html">
 Nate Carlson's caveats</A></P>
<H5>In IPsec passthrough mode</H5>
<P><A HREF="http://www-ec.njit.edu/~rxt1077/Howto.txt"> Sample HOWTO
 through a Linksys Router</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2002/02/msg00114.html">
 Nadeem Hasan's configs</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2002/02/msg00180.html">
 Brock Nanson's tips</A>
<BR></P>
<P><A HREF="#linksys.top">Back to chart</A></P>
<H4><A NAME="lucent">Lucent</A></H4>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2002-May/010976.html">
 Partial success report; see also the next message in thread</A></P>

<!-- section done -->
<P><A HREF="#lucent.top">Back to chart</A></P>
<H4><A NAME="netasq">Netasq</A></H4>
<P><A HREF="http://www.hsc.fr/ressources/ipsec/ipsec2001/#config">
 French page with configs (X.509)</A></P>

<!-- section done -->
<P><A HREF="#netasq.top">Back to chart</A></P>
<H4><A NAME="netcelo">Netcelo</A></H4>
<P><A HREF="http://www.hsc.fr/ressources/ipsec/ipsec2001/#config">
 French page with configs (X.509)</A>
<!-- section done -->
</P>
<P><A HREF="#netcelo.top">Back to chart</A></P>
<H4><A NAME="netgear">Netgear fvs318</A></H4>
<UL>
<LI>With a recent Linux FreeS/WAN, you will require the latest (12/2002)
 Netgear firmware, which supports Diffie-Hellman (DH) group 2. For
 security reasons, we phased out DH 1 after Linux FreeS/WAN 1.5.</LI>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2002-June/011833.html">
 This message</A> reports the incompatibility between Linux FreeS/WAN
 1.6+ and Netgear fvs318 without the firmware upgrade.</LI>
<LI>We believe Linux FreeS/WAN 1.5 and earlier will interoperate with
 any NetGear firmware.</LI>
</UL>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2003-February/017891.html">
 John Morris' setup (PSK)</A></P>
<P><A HREF="#netgear.top">Back to chart</A></P>
<H4><A NAME="netscreen">Netscreen 100 or 5xp</A></H4>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2002-August/013409.html">
 Errol Neal's settings (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-October/015265.html">
 Corey Rogers' configs (PSK, no PFS)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-August/013051.html">
 Jordan Share's configs (PSK, 2 subnets, through static NAT)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/08/msg00404.html">
 Set src proxy_id to your protected subnet/mask</A>
<BR><A HREF="http://www.hsc.fr/ressources/ipsec/ipsec2001/#config">
 French page with ipsec.conf, Netscreen screen shots (X.509, may need to
 revert to PSK...)</A></P>
<P><A HREF="http://archives.neohapsis.com/archives/sf/linux/2001-q2/0123.html">
 A report of a company using Netscreen with FreeS/WAN on a large scale
 (FreeS/WAN road warriors?)</A></P>
<P><A HREF="#netscreen.top">Back to chart</A></P>
<H4><A NAME="nortel">Nortel Contivity</A></H4>
<UL>
<LI> Nortel supports IPsec-over-UDP NAT traversal.</LI>
<LI><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/02/msg00417.html">
 Some older versions of Contivity and FreeS/WAN will not communicate.</A>
</LI>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2002-May/010924.html">
 FreeS/WAN cannot be used as a &quot;client&quot; to a Nortel Contivity server,
 but can be used as a branch-office tunnel.</A></LI>

<!--  Probably obsoleted by Ken's post
<LI>
(Matthias siebler from old interop)
At one point you could not configure Nortel-FreeS/WAN tunnels as 
"Client Tunnels" since FreeS/WAN does not support Aggressive Mode.
Current status of this problem: unknown.
<LI>
<A HREF="http://lists.freeswan.org/pipermail/users/2001-November/004612.html">
How do we map group and user passwords onto the data that FreeS/WAN wants?
</A>
</LI>
-->
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2002-October/015455.html">
 Contivity does not send Distinguished Names in the order FS wants them
 (X.509).</A></LI>
<LI><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/03/msg00137.html">
 Connections may time out after 30-40 minutes idle.</A></LI>
</UL>
<P><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/03/msg00137.html">
 JJ Streicher-Bremer's mini HOWTO for old new software. (PSK with two
 subnets)</A>
<BR><A HREF="http://www.hsc.fr/ressources/ipsec/ipsec2001/#config">
 French page with configs (X.509)</A>. This succeeds using the above
 X.509 tip.</P>

<!-- I could do more searching but this is a solid start. -->
<P><A HREF="#nortel.top">Back to chart</A></P>
<H4><A NAME="radguard">Radguard</A></H4>
<P><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/05/msg00009.html">
 Marko Hausalo's configs (PSK).</A> Note: These do create a connection,
 as you can see by &quot;IPsec SA established&quot;.
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-October/???.html">
 Claudia Schmeing's comments</A></P>
<P><A HREF="#radguard.top">Back to chart</A></P>
<H4><A NAME="raptor">Raptor (NT or Solaris)</A></H4>
<P></P>
<UL>
<LI>Now known as Symantec Enterprise Firewall.</LI>
<LI>The Raptor does not normally come with X.509, but this may be
 available as an add-on.</LI>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2002-May/010256.html">
 Raptor requires alphanumberic PSK values, whereas FreeS/WAN uses hex.</A>
</LI>
<LI>Raptor's tunnel endpoint may be a host, subnet or group of subnets
 (see<A HREF="http://lists.freeswan.org/pipermail/design/2001-November/001295.html">
 this message</A> ). FreeS/WAN cannot handle the group of subnets; you
 must create separate connections for each in order to interoperate.</LI>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2002-May/010113.html">
 Some versions of Raptor accept only single DES.</A> According to this
 German message,<A HREF="http://radawana.cg.tuwien.ac.at/mail-archives/lll/200012/msg00065.html">
 the Raptor Mobile Client demo offers single DES only.</A></LI>
</UL>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2002-January/006935.html">
 Peter Mazinger's settings (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2001-November/005522.html">
 Peter Gerland's configs (PSK)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/07/msg00597.html">
 Charles Griebel's configs (PSK).</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-July/012275.html">
 Lumir Srch's tips (PSK)</A></P>
<P><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/05/msg00214.html">
 John Hardy's configs (Manual)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/01/msg00236.html">
 Older Raptors want 3DES keys in 3 parts (Manual).</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/06/msg00480.html">
 Different keys for each direction? (Manual)</A>
<BR></P>
<P><A HREF="#raptor.top">Back to chart</A></P>
<H4><A NAME="redcreek">Redcreek Ravlin</A></H4>
<UL>
<LI>Known issue #1: The Ravlin expects a quick mode renegotiation right
 after every Main Mode negotiation.</LI>
<LI> Known issue #2: The Ravlin tries to negotiate a zero connection
 lifetime, which it takes to mean &quot;infinite&quot;.<A HREF="http://www.bear-cave.org.uk/linux/ravlin/">
 Jim Hague's patch</A> addresses both issues.</LI>
<LI><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/03/msg00191.html">
 Interop works with Ravlin Firmware &gt; 3.33. Includes tips (PSK).</A></LI>
</UL>
<P><A HREF="#redcreek.top">Back to chart</A></P>
<H4><A NAME="sonicwall">SonicWall</A></H4>
<UL>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2001-June/000998.html">
 Sonicwall cannot be used for Road Warrior setups</A></LI>
<LI> At one point,<A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/05/msg00217.html">
 only Sonicwall PRO supported triple DES</A>.</LI>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2002-March/008600.html">
 Older Sonicwalls (before Nov 2001) feature Diffie Hellman group 1 only</A>
.</LI>
</UL>
<P><A HREF="http://www.xinit.cx/docs/freeswan.html"> Paul Wouters'
 config (PSK)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/02/msg00073.html">
 Dilan Arumainathan's configuration (PSK)</A>
<BR><A HREF="http://www.gravitas.co.uk/vpndebug"> Dariush's setup...
 only opens one way (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2003-July/022302.html">
 Andreas Steffen's tips (X.509)</A>
<BR></P>
<P><A HREF="#sonicwall.top">Back to chart</A></P>
<H4><A NAME="sun">Sun Solaris</A></H4>
<UL>
<LI> Solaris 8+ has a native (in kernel) IPsec implementation.</LI>
<LI><A HREF="http://lists.freeswan.org/pipermail/users/2002-May/010503.html">
 Solaris does not seem to support tunnel mode, but you can make IP-in-IP
 tunnels instead, like this.</A></LI>
</UL>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2003-June/022216.html">
 Reports of some successful interops</A> from a fellow @sun.com. See
 also<A HREF="http://lists.freeswan.org/pipermail/users/2003-July/022247.html">
 these follow up posts</A>.
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/03/msg00332.html">
 Aleks Shenkman's configs (Manual in transport mode)</A>
<BR>
<!--sparc 64 stuff goes where?-->
</P>
<P><A HREF="#solaris.top">Back to chart</A></P>
<H4><A NAME="symantec">Symantec</A></H4>
<UL>
<LI>The Raptor, covered<A HREF="#raptor"> above</A>, is now known as
 Symantec Enterprise Firewall.</LI>
<LI>Symantec's &quot;distinguished name&quot; is a KEY_ID. See Andreas Steffen's
 post, below.</LI>
</UL>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2002-April/009037.html">
 Andreas Steffen's configs for Symantec 200R (PSK)</A></P>
<P><A HREF="#symantec.top">Back to chart</A></P>
<H4><A NAME="watchguard">Watchguard Firebox</A></H4>
<UL>
<LI>Automatic keying works with WatchGuard 5.0+ only.</LI>
<LI>Seen to interoperate with WatchGuard 1000, II, III; firmware v. 5,
 6..</LI>
<LI>For manual keying, Watchguard's Policy Manager expects SPI numbers
 and encryption and authentication keys in decimal (not hex).</LI>
</UL>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2002-July/012595.html">
 WatchGuard's HOWTO (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-August/013342.html">
 Ronald C. Riviera's Settings (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/archives/users/2003-October/msg00179.html">
 Walter Wickersham's Notes (PSK)</A>
<BR><A HREF="http://lists.freeswan.org/pipermail/users/2002-October/015587.html">
 Max Enders' Configs (Manual)</A></P>
<P><A HREF="http://lists.freeswan.org/pipermail/users/2002-April/009404.html">
 Old known issue with auto keying</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/02/msg00124.html">
 Tips on key generation and format (Manual)</A>
<BR></P>
<P><A HREF="#watchguard.top">Back to chart</A></P>
<H4><A NAME="xedia">Xedia Access Point/QVPN</A></H4>
<P><A HREF="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/12/msg00520.html">
 Hybrid IPsec/L2TP connection settings (X.509)</A>
<BR><A HREF="http://www.sandelman.ottawa.on.ca/ipsec/1999/08/msg00140.html">
 Xedia's LAN-LAN links don't use multiple tunnels</A>
<BR> &nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://www.sandelman.ottawa.on.ca/ipsec/1999/08/msg00140.html">
 That explanation, continued</A></P>
<P><A HREF="#xedia.top">Back to chart</A></P>
<H4><A NAME="zyxel">Zyxel</A></H4>
<UL>
<LI>The Zyxel Zywall is a rebranded SSH Sentinel box. See also our
 section on<A HREF="#ssh"> SSH</A>.</LI>
<LI>There seems to be a problem with keeping this connection alive. This
 is caused at the Zyxel end. See this brief<A HREF="http://lists.freeswan.org/archives/users/2003-October/msg00141.html">
 discussion and solution.</A></LI>
</UL>
<P><A HREF="http://www.zyxel.com/support/supportnote/zywall/app/zw_freeswan.htm">
 Zyxel's Zywall to FreeS/WAN instructions (PSK)</A>
<BR><A HREF="http://www.zyxel.com/support/supportnote/p652/app/zw_freeswan.htm">
 Zyxel's Prestige to FreeS/WAN instructions (PSK)</A>. Note: not all
 Prestige versions include VPN software.
<BR><A HREF="http://www.lancry.net/techdocs/freeswan-zyxel.txt"> Fabrice
 Cahen's HOWTO (PSK)</A>
<BR> &nbsp;&nbsp;&nbsp;&nbsp;</P>
<P><A HREF="#zyxel.top">Back to chart</A></P>

<!-- SAMPLE ENTRY

<H4><A NAME="timestep">Timestep</A></H4>

<P>Text goes here.
</P>

-->
<HR>
<H1><A name="performance">Performance of FreeS/WAN</A></H1>
 The performance of FreeS/WAN is adequate for most applications.
<P>In normal operation, the main concern is the overhead for encryption,
 decryption and authentication of the actual IPsec (<A href="#ESP">ESP</A>
 and/or<A href="#AH"> AH</A>) data packets. Tunnel setup and rekeying
 occur so much less frequently than packet processing that, in general,
 their overheads are not worth worrying about.</P>
<P>At startup, however, tunnel setup overheads may be significant. If
 you reboot a gateway and it needs to establish many tunnels, expect
 some delay. This and other issues for large gateways are discussed<A href="#biggate">
 below</A>.</P>
<H2><A name="pub.bench">Published material</A></H2>
<P>The University of Wales at Aberystwyth has done quite detailed speed
 tests and put<A href="http://tsc.llwybr.org.uk/public/reports/SWANTIME/">
 their results</A> on the web.</P>
<P>Davide Cerri's<A href="http://www.linux.it/~davide/doc/"> thesis (in
 Italian)</A> includes performance results for FreeS/WAN and for<A href="#TLS">
 TLS</A>. He posted an<A href="http://lists.freeswan.org/pipermail/users/2001-December/006303.html">
 English summary</A> on the mailing list.</P>
<P>Steve Bellovin used one of AT&amp;T Research's FreeS/WAN gateways as his
 data source for an analysis of the cache sizes required for key
 swapping in IPsec. Available as<A href="http://www.research.att.com/~smb/talks/key-agility.email.txt">
 text</A> or<A href="http://www.research.att.com/~smb/talks/key-agility.pdf">
 PDF slides</A> for a talk on the topic.</P>
<P>See also the NAI work mentioned in the next section.</P>
<H2><A name="perf.estimate">Estimating CPU overheads</A></H2>
<P>We can come up with a formula that roughly relates CPU speed to the
 rate of IPsec processing possible. It is far from exact, but should be
 usable as a first approximation.</P>
<P>An analysis of authentication overheads for high-speed networks,
 including some tests using FreeS/WAN, is on the<A href="http://www.pgp.com/research/nailabs/cryptographic/adaptive-cryptographic.asp">
 NAI Labs site</A>. In particular, see figure 3 in this<A href="http://download.nai.com/products/media/pgp/pdf/acsa_final_report.pdf">
 PDF document</A>. Their estimates of overheads, measured in Pentium II
 cycles per byte processed are:</P>
<TABLE align="center" border="1"><TBODY></TBODY>
<TR><TH></TH><TH>IPsec</TH><TH>authentication</TH><TH>encryption</TH><TH>
cycles/byte</TH></TR>
<TR><TD>Linux IP stack alone</TD><TD>no</TD><TD>no</TD><TD>no</TD><TD align="right">
5</TD></TR>
<TR><TD>IPsec without crypto</TD><TD>yes</TD><TD>no</TD><TD>no</TD><TD align="right">
11</TD></TR>
<TR><TD>IPsec, authentication only</TD><TD>yes</TD><TD>SHA-1</TD><TD>no</TD><TD
align="right">24</TD></TR>
<TR><TD>IPsec with encryption</TD><TD>yes</TD><TD>yes</TD><TD>yes</TD><TD
align="right">not tested</TD></TR>
</TABLE>
<P>Overheads for IPsec with encryption were not tested in the NAI work,
 but Antoon Bosselaers'<A href="http://www.esat.kuleuven.ac.be/~bosselae/fast.html">
 web page</A> gives cost for his optimised Triple DES implementation as
 928 Pentium cycles per block, or 116 per byte. Adding that to the 24
 above, we get 140 cycles per byte for IPsec with encryption.</P>
<P>At 140 cycles per byte, a 140 MHz machine can handle a megabyte -- 8
 megabits -- per second. Speeds for other machines will be proportional
 to this. To saturate a link with capacity C megabits per second, you
 need a machine running at<VAR> C * 140/8 = C * 17.5</VAR> MHz.</P>
<P>However, that estimate is not precise. It ignores the differences
 between:</P>
<UL>
<LI>NAI's test packets and real traffic</LI>
<LI>NAI's Pentium II cycles, Bosselaers' Pentium cycles, and your
 machine's cycles</LI>
<LI>different 3DES implementations</LI>
<LI>SHA-1 and MD5</LI>
</UL>
<P>and does not account for some overheads you will almost certainly
 have:</P>
<UL>
<LI>communication on the client-side interface</LI>
<LI>switching between multiple tunnels -- re-keying, cache reloading and
 so on</LI>
</UL>
<P>so we suggest using<VAR> C * 25</VAR> to get an estimate with a bit
 of a built-in safety factor.</P>
<P>This covers only IP and IPsec processing. If you have other loads on
 your gateway -- for example if it is also working as a firewall -- then
 you will need to add your own safety factor atop that.</P>
<P>This estimate matches empirical data reasonably well. For example,
 Metheringham's tests, described<A href="#klips.bench"> below</A>, show
 a 733 topping out between 32 and 36 Mbit/second, pushing data as fast
 as it can down a 100 Mbit link. Our formula suggests you need at least
 an 800 to handle a fully loaded 32 Mbit link. The two results are
 consistent.</P>
<P>Some examples using this estimation method:</P>
<TABLE align="center" border="1"><TBODY></TBODY>
<TR><TH colspan="2">Interface</TH><TH colspan="3">Machine speed in MHz</TH>
</TR>
<TR><TH>Type</TH><TH>Mbit per
<BR> second</TH><TH>Estimate
<BR> Mbit*25</TH><TH>Minimum IPSEC gateway</TH><TH>Minimum with other
 load
<P>(e.g. firewall)</P>
</TH></TR>
<TR><TD>DSL</TD><TD align="right">1</TD><TD align="right">25 MHz</TD><TD rowspan="2">
whatever you have</TD><TD rowspan="2">133, or better if you have it</TD></TR>
<TR><TD>cable modem</TD><TD align="right">3</TD><TD align="right">75 MHz</TD>
</TR>
<TR><TD><STRONG>any link, light load</STRONG></TD><TD align="right"><STRONG>
5</STRONG></TD><TD align="right">125 MHz</TD><TD>133</TD><TD>200+,<STRONG>
 almost any surplus machine</STRONG></TD></TR>
<TR><TD>Ethernet</TD><TD align="right">10</TD><TD align="right">250 MHz</TD><TD>
surplus 266 or 300</TD><TD>500+</TD></TR>
<TR><TD><STRONG>fast link, moderate load</STRONG></TD><TD align="right"><STRONG>
20</STRONG></TD><TD align="right">500 MHz</TD><TD>500</TD><TD>800+,<STRONG>
 any current off-the-shelf PC</STRONG></TD></TR>
<TR><TD>T3 or E3</TD><TD align="right">45</TD><TD align="right">1125 MHz</TD><TD>
1200</TD><TD>1500+</TD></TR>
<TR><TD>fast Ethernet</TD><TD align="right">100</TD><TD align="right">
2500 MHz</TD><TD align="center" colspan="2" rowspan="2">// not feasible
 with 3DES in software on current machines //</TD></TR>
<TR><TD>OC3</TD><TD align="right">155</TD><TD align="right">3875 MHz</TD>
</TR>
</TABLE>
<P>Such an estimate is far from exact, but should be usable as minimum
 requirement for planning. The key observations are:</P>
<UL>
<LI>older<STRONG> surplus machines</STRONG> are fine for IPsec gateways
 at loads up to<STRONG> 5 megabits per second</STRONG> or so</LI>
<LI>a<STRONG> mid-range new machine</STRONG> can handle IPsec at rates
 up to<STRONG> 20 megabits per second</STRONG> or more</LI>
</UL>
<H3><A name="perf.more">Higher performance alternatives</A></H3>
<P><A href="#AES">AES</A> is a new US government block cipher standard,
 designed to replace the obsolete<A href="#DES"> DES</A>. If FreeS/WAN
 using<A href="#3DES"> 3DES</A> is not fast enough for your application,
 the AES<A href="#patch"> patch</A> may help.</P>
<P>To date (March 2002) we have had only one<A href="http://lists.freeswan.org/pipermail/users/2002-February/007771.html">
 mailing list report</A> of measurements with the patch applied. It
 indicates that, at least for the tested load on that user's network,<STRONG>
 AES roughly doubles IPsec throughput</STRONG>. If further testing
 confirms this, it may prove possible to saturate an OC3 link in
 software on a high-end box.</P>
<P>Also, some work is being done toward support of<A href="#hardware">
 hardware IPsec acceleration</A> which might extend the range of
 requirements FreeS/WAN could meet.</P>
<H3><A NAME="11_2_2">Other considerations</A></H3>
<P>CPU speed may be the main issue for IPsec performance, but of course
 it isn't the only one.</P>
<P>You need good ethernet cards or other network interface hardware to
 get the best performance. See this<A href="http://www.ethermanage.com/ethernet/ethernet.html">
 ethernet information</A> page and this<A href="http://www.scyld.com/diag">
 Linux network driver</A> page.</P>
<P>The current FreeS/WAN kernel code is largely single-threaded. It is
 SMP safe, and will run just fine on a multiprocessor machine (<A href="#multiprocessor">
discussion</A>), but the load within the kernel is not shared
 effectively. This means that, for example to saturate a T3 -- which
 needs about a 1200 MHz machine -- you cannot expect something like a
 dual 800 to do the job.</P>
<P>On the other hand, SMP machines do tend to share loads well so --
 provided one CPU is fast enough for the IPsec work -- a multiprocessor
 machine may be ideal for a gateway with a mixed load.</P>
<H2><A name="biggate">Many tunnels from a single gateway</A></H2>
<P>FreeS/WAN allows a single gateway machine to build tunnels to many
 others. There may, however, be some problems for large numbers as
 indicated in this message from the mailing list:</P>
<PRE>Subject: Re: Maximum number of ipsec tunnels?
   Date: Tue, 18 Apr 2000
   From: &quot;John S. Denker&quot; &lt;jsd@research.att.com&gt;

Christopher Ferris wrote:

&gt;&gt; What are the maximum number ipsec tunnels FreeS/WAN can handle??

Henry Spencer wrote:

&gt;There is no particular limit.  Some of the setup procedures currently
&gt;scale poorly to large numbers of connections, but there are (clumsy)
&gt;workarounds for that now, and proper fixes are coming.

1) &quot;Large&quot; numbers means anything over 50 or so.  I routinely run boxes
with about 200 tunnels.  Once you get more than 50 or so, you need to worry
about several scalability issues:

a) You need to put a &quot;-&quot; sign in syslogd.conf, and rotate the logs daily
not weekly.

b) Processor load per tunnel is small unless the tunnel is not up, in which
case a new half-key gets generated every 90 seconds, which can add up if
you've got a lot of down tunnels.

c) There's other bits of lore you need when running a large number of
tunnels.  For instance, systematically keeping the .conf file free of
conflicts requires tools that aren't shipped with the standard freeswan
package.

d) The pluto startup behavior is quadratic.  With 200 tunnels, this eats up
several minutes at every restart.   I'm told fixes are coming soon.

2) Other than item (1b), the CPU load depends mainly on the size of the
pipe attached, not on the number of tunnels.
</PRE>
<P>It is worth noting that item (1b) applies only to repeated attempts
 to re-key a data connection (IPsec SA, Phase 2) over an established
 keying connection (ISAKMP SA, Phase 1). There are two ways to reduce
 this overhead using settings in<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A>:</P>
<UL>
<LI>set<VAR> keyingtries</VAR> to some small value to limit repetitions</LI>
<LI>set<VAR> keylife</VAR> to a short time so that a failing data
 connection will be cleaned up when the keying connection is reset.</LI>
</UL>
<P>The overheads for establishing keying connections (ISAKMP SAs, Phase
 1) are lower because for these Pluto does not perform expensive
 operations before receiving a reply from the peer.</P>
<P>A gateway that does a lot of rekeying -- many tunnels and/or low
 settings for tunnel lifetimes -- will also need a lot of<A href="#random">
 random numbers</A> from the random(4) driver.</P>
<H2><A name="low-end">Low-end systems</A></H2>
<P><EM>Even a 486 can handle a T1 line</EM>, according to this mailing
 list message:</P>
<PRE>Subject: Re: linux-ipsec: IPSec Masquerade
   Date: Fri, 15 Jan 1999 11:13:22 -0500
   From: Michael Richardson 

. . . A 486/66 has been clocked by Phil Karn to do
10Mb/s encryption.. that uses all the CPU, so half that to get some CPU,
and you have 5Mb/s. 1/3 that for 3DES and you get 1.6Mb/s....</PRE>
<P>and a piece of mail from project technical lead Henry Spencer:</P>
<PRE>Oh yes, and a new timing point for Sandy's docs...  A P60 -- yes, a 60MHz
Pentium, talk about antiques -- running a host-to-host tunnel to another
machine shows an FTP throughput (that is, end-to-end results with a real
protocol) of slightly over 5Mbit/s either way.  (The other machine is much
faster, the network is 100Mbps, and the ether cards are good ones... so
the P60 is pretty definitely the bottleneck.)</PRE>
<P>From the above, and from general user experience as reported on the
 list, it seems clear that a cheap surplus machine -- a reasonable 486,
 a minimal Pentium box, a Sparc 5, ... -- can easily handle a home
 office or a small company connection using any of:</P>
<UL>
<LI>ADSL service</LI>
<LI>cable modem</LI>
<LI>T1</LI>
<LI>E1</LI>
</UL>
<P>If available, we suggest using a Pentium 133 or better. This should
 ensure that, even under maximum load, IPsec will use less than half the
 CPU cycles. You then have enough left for other things you may want on
 your gateway -- firewalling, web caching, DNS and such.</P>
<H2><A name="klips.bench">Measuring KLIPS</A></H2>
<P>Here is some additional data from the mailing list.</P>
<PRE>Subject: FreeSWAN (specically KLIPS) performance measurements
   Date: Thu, 01 Feb 2001
   From: Nigel Metheringham &lt;Nigel.Metheringham@intechnology.co.uk&gt;

I've spent a happy morning attempting performance tests against KLIPS 
(this is due to me not being able to work out the CPU usage of KLIPS so 
resorting to the crude measurements of maximum throughput to give a 
baseline to work out loading of a box).

Measurements were done using a set of 4 boxes arranged in a line, each 
connected to the next by 100Mbit duplex ethernet.  The inner 2 had an 
ipsec tunnel between them (shared secret, but I was doing measurements 
when the tunnel was up and running - keying should not be an issue 
here).  The outer pair of boxes were traffic generators or traffic sink.

The crypt boxes are Compaq DL380s - Uniprocessor PIII/733 with 256K 
cache.  They have 128M main memory.  Nothing significant was running on 
the boxes other than freeswan.  The kernel was a 2.2.19pre7 patched 
with freeswan and ext3.

Without an ipsec tunnel in the chain (ie the 2 inner boxes just being 
100BaseT routers), throughput (measured with ttcp) was between 10644 
and 11320 KB/sec

With an ipsec tunnel in place, throughput was between 3268 and 3402 
KB/sec

These measurements are for data pushed across a TCP link, so the 
traffic on the wire between the 2 ipsec boxes would have been higher 
than this....

vmstat (run during some other tests, so not affecting those figures) on 
the encrypting box shows approx 50% system &amp; 50% idle CPU - which I 
don't believe at all.  Interactive feel of the box was significantly 
sluggish.

I also tried running the kernel profiler (see man readprofile) during 
test runs.

A box doing primarily decrypt work showed basically nothing happening - 
I assume interrupts were off.
A box doing encrypt work showed the following:-
 Ticks Function                                   Load
 ~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~    ~~~~~~
   956 total                                      0.0010
   532 des_encrypt2                               0.1330
   110 MD5Transform                               0.0443
    97 kmalloc                                    0.1880
    39 des_encrypt3                               0.1336
    23 speedo_interrupt                           0.0298
    14 skb_copy_expand                            0.0250
    13 ipsec_tunnel_start_xmit                    0.0009
    13 Decode                                     0.1625
    11 handle_IRQ_event                           0.1019
    11 .des_ncbc_encrypt_end                      0.0229
    10 speedo_start_xmit                          0.0188
     9 satoa                                      0.0225
     8 kfree                                      0.0118
     8 ip_fragment                                0.0121
     7 ultoa                                      0.0365
     5 speedo_rx                                  0.0071
     5 .des_encrypt2_end                          5.0000
     4 _stext                                     0.0140
     4 ip_fw_check                                0.0035
     2 rj_match                                   0.0034
     2 ipfw_output_check                          0.0200
     2 inet_addr_type                             0.0156
     2 eth_copy_and_sum                           0.0139
     2 dev_get                                    0.0294
     2 addrtoa                                    0.0143
     1 speedo_tx_buffer_gc                        0.0024
     1 speedo_refill_rx_buf                       0.0022
     1 restore_all                                0.0667
     1 number                                     0.0020
     1 net_bh                                     0.0021
     1 neigh_connected_output                     0.0076
     1 MD5Final                                   0.0083
     1 kmem_cache_free                            0.0016
     1 kmem_cache_alloc                           0.0022
     1 __kfree_skb                                0.0060
     1 ipsec_rcv                                  0.0001
     1 ip_rcv                                     0.0014
     1 ip_options_fragment                        0.0071
     1 ip_local_deliver                           0.0023
     1 ipfw_forward_check                         0.0139
     1 ip_forward                                 0.0011
     1 eth_header                                 0.0040
     1 .des_encrypt3_end                          0.0833
     1 des_decrypt3                               0.0034
     1 csum_partial_copy_generic                  0.0045
     1 call_out_firewall                          0.0125

Hope this data is helpful to someone... however the lack of visibility 
into the decrypt side makes things less clear</PRE>
<H2><A name="speed.compress">Speed with compression</A></H2>
<P>Another user reported some results for connections with and without
 IP compression:</P>
<PRE>Subject: [Users] Speed with compression
   Date: Fri, 29 Jun 2001
   From: John McMonagle &lt;johnm@advocap.org&gt;

Did a couple tests with compression using the new 1.91 freeswan.

Running between 2 sites with cable modems.  Both  using approximately
130 mhz pentium.

Transferred files with ncftp.

Compressed file was a 6mb compressed  installation file.
Non compressed was 18mb /var/lib/rpm/packages.rpm

                            Compressed vpn          regular vpn
Compress file                42.59 kBs               42.08 kBs
regular file                110.84 kBs               41.66 kBs

Load  was about 0 either way.
Ping times were very similar  a bit above 9 ms.

Compression looks attractive to me.</PRE>
 Later in the same thread, project technical lead Henry Spencer added:
<PRE>&gt; is there a reason not to switch compression on?  I have large gateway boxes
&gt; connecting 3 connections, one of them with a measly DS1 link...

Run some timing tests with and without, with data and loads representative
of what you expect in production.  That's the definitive way to decide. 
If compression is a net loss, then obviously, leave it turned off.  If it
doesn't make much difference, leave it off for simplicity and hence
robustness.  If there's a substantial gain, by all means turn it on. 

If both ends support compression and can successfully negotiate a
compressed connection (trivially true if both are FreeS/WAN 1.91), then
the crucial question is CPU cycles. 

Compression has some overhead, so one question is whether *your* data
compresses well enough to save you more CPU cycles (by reducing the volume
of data going through CPU-intensive encryption/decryption) than it costs
you.  Last time I ran such tests on data that was reasonably compressible
but not deliberately contrived to be so, this generally was not true --
compression cost extra CPU cycles -- so compression was worthwhile only if
the link, not the CPU, was the bottleneck.  However, that was before the
slow-compression bug was fixed.  I haven't had a chance to re-run those
tests yet, but it sounds like I'd probably see a different result. </PRE>
 The bug he refers to was a problem with the compression libraries that
 had us using C code, rather than assembler, for compression. It was
 fixed before 1.91.
<H2><A name="methods">Methods of measuring</A></H2>
<P>If you want to measure the loads FreeS/WAN puts on a system, note
 that tools such as top or measurements such as load average are
 more-or-less useless for this. They are not designed to measure
 something that does most of its work inside the kernel.</P>
<P>Here is a message from FreeS/WAN kernel programmer Richard Guy Briggs
 on this:</P>
<PRE>&gt; I have a batch of boxes doing Freeswan stuff.
&gt; I want to measure the CPU loading of the Freeswan tunnels, but am 
&gt; having trouble seeing how I get some figures out...
&gt; 
&gt;  - Keying etc is in userspace so will show up on the per-process
&gt;    and load average etc (ie pluto's load)

Correct.

&gt;  - KLIPS is in the kernel space, and does not show up in load average
&gt;    I think also that the KLIPS per-packet processing stuff is running
&gt;    as part of an interrupt handler so it does not show up in the
&gt;    /proc/stat system_cpu or even idle_cpu figures

It is not running in interrupt handler.  It is in the bottom half.
This is somewhere between user context (careful, this is not
userspace!) and hardware interrupt context.

&gt; Is this correct, and is there any means of instrumenting how much the 
&gt; cpu is being loaded - I don't like the idea of a system running out of 
&gt; steam whilst still showing 100% idle CPU :-)

vmstat seems to do a fairly good job, but use a running tally to get a
good idea.  A one-off call to vmstat gives different numbers than a
running stat.  To do this, put an interval on your vmstat command
line.</PRE>
 and another suggestion from the same thread:
<PRE>Subject: Re: Measuring the CPU usage of Freeswan
   Date: Mon, 29 Jan 2001
   From: Patrick Michael Kane &lt;modus@pr.es.to&gt;
 
The only truly accurate way to accurately track FreeSWAN CPU usage is to use
a CPU soaker. You run it on an unloaded system as a benchmark, then start up
FreeSWAN and take the difference to determine how much FreeSWAN is eating.
I believe someone has done this in the past, so you may find something in
the FreeSWAN archives.  If not, someone recently posted a URL to a CPU
soaker benchmark tool on linux-kernel.</PRE>
<HR>
<H1><A name="test.freeswan">Testing FreeS/WAN</A></H1>
 This document discusses testing FreeS/WAN.
<P>Not all types of testing are described here. Other parts of the
 documentation describe some tests:</P>
<DL>
<DT><A href="#testinstall">installation</A> document</DT>
<DD>testing for a successful install</DD>
<DT><A href="config.html#testsetup">configuration</A> document</DT>
<DD>basic tests for a working configuration</DD>
<DT><A href="#interop.web">web links</A> document</DT>
<DD>General information on tests for interoperability between various
 IPsec implementations. This includes links to several test sites.</DD>
<DT><A href="interop.html">interoperation</A> document.</DT>
<DD>More specific information on FreeS/WAN interoperation with other
 implementations.</DD>
<DT><A href="performance.html">performance</A> document</DT>
<DD>performance measurements</DD>
</DL>
<P>The test setups and procedures described here can also be used in
 other testing, but this document focuses on testing the IPsec
 functionality of FreeS/WAN.</P>
<H2><A NAME="test.oe">Testing opportunistic connections</A></H2>
<P>This section teaches you how to test your opportunistically encrypted
 (OE) connections. To set up OE, please see the easy instructions in our<A
HREF="quickstart.html"> quickstart guide</A>.</P>
<H3><A NAME="12_1_1">Basic OE Test</A></H3>
<P>This test is for basic OE functionality.
<!-- You may use it on an 
<A HREF="quickstart.html#oppo.client">initiate-only OE</A> box or a 
<A HREF="quickstart.html#opp.incoming">full OE</A> box. -->
 For additional tests, keep
 reading.</P>
<P>Be sure IPsec is running. You can see whether it is with:</P>
<PRE>    ipsec setup status</PRE>
<P>If need be, you can restart it with:</P>
<PRE>    service ipsec restart</PRE>
<P>Load a FreeS/WAN test website from the host on which you're running
 FreeS/WAN. Note: the feds may be watching these sites. Type one of:</P>
<P></P>
<PRE>   links oetest.freeswan.org</PRE>
<PRE>   links oetest.freeswan.nl</PRE>

<!--<PRE>   links oetest.freeswan.ca</PRE>-->
<P>A positive result looks like this:</P>
<PRE>
   You  seem  to  be  connecting  from:  192.0.2.11 which DNS says is:
   gateway.example.com
     _________________________________________________________________
                                                                                
   Status E-route
   OE    enabled    16    192.139.46.73/32    -&gt;    192.0.2.11/32   =&gt;
   tun0x2097@192.0.2.11
   OE    enabled    176    192.139.46.77/32    -&gt;   192.0.2.11/32   =&gt;
   tun0x208a@192.0.2.11
</PRE>
<P>If you see this, congratulations! Your OE box will now encrypt its
 own traffic whenever it can. If you have difficulty, see our<A HREF="#oe.trouble">
 OE troubleshooting tips</A>.</P>
<H3><A NAME="12_1_2">OE Gateway Test</A></H3>
<P>If you've set up FreeS/WAN to protect a subnet behind your gateway,
 you'll need to run another simple test, which can be done from a
 machine running any OS. That's right, your Windows box can be protected
 by opportunistic encryption without any FreeS/WAN install or
 configuration on that box. From<STRONG> each protected subnet node</STRONG>
, load the FreeS/WAN website with:</P>
<PRE>   links oetest.freeswan.org</PRE>
<PRE>   links oetest.freeswan.nl</PRE>
<P>A positive result looks like this:</P>
<PRE>
   You  seem  to  be  connecting  from:  192.0.2.98 which DNS says is:
   box98.example.com
     _________________________________________________________________
                                                                                
   Status E-route
   OE    enabled    16    192.139.46.73/32    -&gt;    192.0.2.98/32   =&gt;
   tun0x134ed@192.0.2.11
   OE    enabled    176    192.139.46.77/32    -&gt;   192.0.2.11/32   =&gt;
   tun0x134d2@192.0.2.11
</PRE>
<P>If you see this, congratulations! Your OE gateway will now encrypt
 traffic for this subnet node whenever it can. If you have difficulty,
 see our<A HREF="#oe.trouble"> OE troubleshooting tips</A>.</P>
<H3><A NAME="12_1_3">Additional OE tests</A></H3>
<P>When testing OE, you will often find it useful to execute this
 command on the FreeS/WAN host:</P>
<PRE>   ipsec eroute</PRE>
<P>If you have established a connection (either for or for a subnet
 node) you will see a result like:</P>
<PRE>    192.0.2.11/32   -&gt; 192.139.46.73/32  =&gt; tun0x149f@192.139.46.38
</PRE>
<P>Key:</P>
<TABLE>
<TR><TD>1.</TD><TD>192.0.2.11/32</TD><TD>Local start point of the
 protected traffic.</TD></TR>
<TR><TD>2.</TD><TD>192.0.2.194/32</TD><TD>Remote end point of the
 protected traffic.</TD></TR>
<TR><TD>3.</TD><TD>192.0.48.38</TD><TD>Remote FreeS/WAN node (gateway or
 host). May be the same as (2).</TD></TR>
<TR><TD>4.</TD><TD>[not shown]</TD><TD>Local FreeS/WAN node (gateway or
 host), where you've produced the output. May be the same as (1).</TD></TR>
</TABLE>
<P>For extra assurance, you may wish to use a packet sniffer such as<A HREF="http://www.tcpdump.org">
 tcpdump</A> to verify that packets are being encrypted. You should see
 output that indicates<STRONG> ESP</STRONG> encrypted data, for example:</P>
<PRE>    02:17:47.353750 PPPoE  [ses 0x1e12] IP 154: xy.example.com &gt; oetest.freeswan.org: ESP(spi=0x87150d16,seq=0x55)</PRE>
<H2><A name="test.uml">Testing with User Mode Linux</A></H2>
<P><A href="http://user-mode-linux.sourceforge.net/">User Mode Linux</A>
 allows you to run Linux as a user process on another Linux machine.</P>
<P>As of 1.92, the distribution has a new directory named testing. It
 contains a collection of test scripts and sample configurations. Using
 these, you can bring up several copies of Linux in user mode and have
 them build tunnels to each other. This lets you do some testing of a
 FreeS/WAN configuration on a single machine.</P>
<P>You need a moderately well-endowed machine for this to work well.
 Each UML wants about 16 megs of memory by default, which is plenty for
 FreeS/WAN usage. Typical regression testing only occasionally uses as
 many as 4 UMLs. If one is doing nothing else with the machine (in
 particular, not running X on it), then 128 megs and a 500MHz CPU are
 fine.</P>
 Documentation on these scripts is<A href="umltesting.html"> here</A>.
 There is also documentation on automated testing<A href="makecheck.html">
 here</A>.
<H2><A name="testnet">Configuration for a testbed network</A></H2>
<P>A common test setup is to put a machine with dual Ethernet cards in
 between two gateways under test. You need at least five machines; two
 gateways, two clients and a testing machine in the middle.</P>
<P>The central machine both routes packets and provides a place to run
 diagnostic software for checking IPsec packets. See next section for
 discussion of<A href="#tcpdump.faq"> using tcpdump(8)</A> for this.</P>
<P>This makes things more complicated than if you just connected the two
 gateway machines directly to each other, but it also makes your test
 setup much more like the environment you actually use IPsec in. Those
 environments nearly always involve routing, and quite a few apparent
 IPsec failures turn out to be problems with routing or with firewalls
 dropping packets. This approach lets you deal with those problems on
 your test setup.</P>
<P>What you end up with looks like:</P>
<H3><A name="testbed">Testbed network</A></H3>
<PRE>      subnet a.b.c.0/24
             |
      eth1 = a.b.c.1
         gate1
      eth0 = 192.168.p.1
             |
             |
      eth0 = 192.168.p.2
         route/monitor box
      eth1 = 192.168.q.2
             |
             |
      eth0 = 192.168.q.1
         gate2
      eth1 = x.y.z.1
              |
       subnet x.y.z.0/24</PRE>
<PRE>Where p and q are any convenient values that do not interfere with other
routes you may have. The ipsec.conf(5) file then has, among other things:</PRE>
<PRE>conn abc-xyz
      left=192.168.p.1
      leftnexthop=192.168.p.2
      right=192.168.q.1
      rightnexthop=192.168.q.2</PRE>
<P>Once that works, you can remove the &quot;route/monitor box&quot;, and connect
 the two gateways to the Internet. The only parameters in ipsec.conf(5)
 that need to change are the four shown above. You replace them with
 values appropriate for your Internet connection, and change the eth0 IP
 addresses and the default routes on both gateways.</P>
<P>Note that nothing on either subnet needs to change. This lets you
 test most of your IPsec setup before connecting to the insecure
 Internet.</P>
<H3><A name="tcpdump.test">Using packet sniffers in testing</A></H3>
<P>A number of tools are available for looking at packets. We will
 discuss using<A href="http://www.tcpdump.org/"> tcpdump(8)</A>, a
 common Linux tool included in most distributions. Alternatives
 offerring more-or-less the same functionality include:</P>
<DL>
<DT><A href="http://www.ethereal.com">Ethereal</A></DT>
<DD>Several people on our mailing list report a preference for this over
 tcpdump.</DD>
<DT><A href="http://netgroup-serv.polito.it/windump/">windump</A></DT>
<DD>a Windows version of tcpdump(8), possibly handy if you have Windows
 boxes in your network</DD>
<DT><A href="http://reptile.rug.ac.be/~coder/sniffit/sniffit.html">
Sniffit</A></DT>
<DD>A linux sniffer that we don't know much about. If you use it, please
 comment on our mailing list.</DD>
</DL>
<P>See also this<A href="http://www.tlsecurity.net/unix/ids/sniffer/">
 index</A> of packet sniffers.</P>
<P>tcpdump(8) may misbehave if run on the gateways themselves. It is
 designed to look into a normal IP stack and may become confused if you
 ask it to display data from a stack which has IPsec in play.</P>
<P>At one point, the problem was quite severe. Recent versions of
 tcpdump, however, understand IPsec well enough to be usable on a
 gateway. You can get the latest version from<A href="http://www.tcpdump.org/">
 tcpdump.org</A>.</P>
<P>Even with a recent tcpdump, some care is required. Here is part of a
 post from Henry on the topic:</P>
<PRE>&gt; a) data from sunset to sunrise or the other way is not being
&gt; encrypted (I am using tcpdump (ver. 3.4) -x/ping -p to check
&gt; packages) 

What *interface* is tcpdump being applied to?  Use the -i option to
control this.  It matters!  If tcpdump is looking at the ipsecN
interfaces, e.g. ipsec0, then it is seeing the packets before they are
encrypted or after they are decrypted, so of course they don't look
encrypted.  You want to have tcpdump looking at the actual hardware
interfaces, e.g. eth0. 

Actually, the only way to be *sure* what you are sending on the wire is to
have a separate machine eavesdropping on the traffic.  Nothing you can do
on the machines actually running IPsec is 100% guaranteed reliable in this
area (although tcpdump is a lot better now than it used to be).</PRE>
<P>The most certain way to examine IPsec packets is to look at them on
 the wire. For security, you need to be certain, so we recommend doing
 that. To do so, you need a<STRONG> separate sniffer machine located
 between the two gateways</STRONG>. This machine can be routing IPsec
 packets, but it must not be an IPsec gateway. Network configuration for
 such testing is discussed<A href="#testnet"> above</A>.</P>
<P>Here's another mailing list message with advice on using tcpdump(8):</P>
<PRE>Subject: RE: [Users] Encrypted???
   Date: Thu, 29 Nov 2001
   From: &quot;Joe Patterson&quot; &lt;jpatterson@asgardgroup.com&gt;

tcpdump -nl -i $EXT-IF proto 50

-nl tells it not to buffer output or resolve names (if you don't do that it
may confuse you by not outputing anything for a while), -i $EXT-IF (replace
with your external interface) tells it what interface to listen on, and
proto 50 is ESP.  Use &quot;proto 51&quot; if for some odd reason you're using AH, and
&quot;udp port 500&quot; if you want to see the isakmp key exchange/tunnel setup
packets.

You can also run `tcpdump -nl -i ipsec0` to see what traffic is on that
virtual interface.  Anything you see there *should* be either encrypted or
dropped (unless you've turned on some strange options in your ipsec.conf
file)

Another very handy thing is ethereal (http://www.ethereal.com/) which runs
on just about anything, has a nice gui interface (or a nice text-based
interface), and does a great job of protocol  breakdown.  For ESP and AH
it'll basically just tell you that there's a packet of that protocol, and
what the spi is, but for isakmp it'll actually show you a lot of the tunnel
setup information (until it gets to the point in the protocol where isakmp
is encrypted....)</PRE>
<H2><A name="verify.crypt">Verifying encryption</A></H2>
<P>The question of how to verify that messages are actually encrypted
 has been extensively discussed on the mailing list. See this<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/07/msg00262.html">
 thread</A>.</P>
<P>If you just want to verify that packets are encrypted, look at them
 with a packet sniffer (see<A href="#tcpdump.test"> previous section</A>
) located between the gateways. The packets should, except for some of
 the header information, be utterly unintelligible.<STRONG> The output
 of good encryption looks<EM> exactly</EM> like random noise</STRONG>.</P>
<P>A packet sniffer can only tell you that the data you looked at was
 encrypted. If you have stronger requirements -- for example if your
 security policy requires verification that plaintext is not leaked
 during startup or under various anomolous conditions -- then you will
 need to devise much more thorough tests. If you do that, please post
 any results or methodological details which your security policy allows
 you to make public.</P>
<P>You can put recognizable data into ping packets with something like:</P>
<PRE>        ping -p feedfacedeadbeef 11.0.1.1</PRE>
<P>&quot;feedfacedeadbeef&quot; is a legal hexadecimal pattern that is easy to
 pick out of hex dumps.</P>
<P>For other protocols, you may need to check if you have encrypted data
 or ASCII text. Encrypted data has approximately equal frequencies for
 all 256 possible characters. ASCII text has most characters in the
 printable range 0x20-0x7f, a few control characters less than 0x20, and
 none at all in the range 0x80-0xff. 0x20, space, is a good character to
 look for. In normal English text space occurs about once in seven
 characters, versus about once in 256 for random or encrypted data.</P>
<P>One thing to watch for: the output of good compression, like that of
 good encryption, looks just like random noise. You cannot tell just by
 looking at a data stream whether it has been compressed, encrypted, or
 both. You need a little care not to mistake compressed data for
 encrypted data in your testing.</P>
<P>Note also that weak encryption also produces random-looking output.
 You cannot tell whether the encryption is strong by looking at the
 output. To be sure of that, you would need to have both the algorithms
 and the implementation examined by experts.</P>
<P>For IPsec, you can get partial assurance from interoperability tests.
 See our<A href="interop.html"> interop</A> document. When twenty
 products all claim to implement<A href="#3DES"> 3DES</A>, and they all
 talk to each other, you can be fairly sure they have it right. Of
 course, you might wonder whether all the implementers are consipring to
 trick you or, more plausibly, whether some implementations might have
 &quot;back doors&quot; so they can get also it wrong when required.. If you're
 seriously worried about things like that, you need to get the code you
 use audited (good luck if it is not Open Source), or perhaps to talk to
 a psychiatrist about treatments for paranoia.</P>
<H2><A name="mail.test">Mailing list pointers</A></H2>
<P>Additional information on testing can be found in these<A href="mail.html">
 mailing list</A> messages:</P>
<UL>
<LI>a user's detailed<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/11/msg00571.html">
 setup diary</A> for his testbed network</LI>
<LI>a FreeS/WAN team member's<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/11/msg00425.html">
 notes</A> from testing at an IPsec interop &quot;bakeoff&quot;</LI>
</UL>
<HR>
<H1><A name="kernelconfig">Kernel configuration for FreeS/WAN</A></H1>
<P> This section lists many of the options available when configuring a
 Linux kernel, and explains how they should be set on a FreeS/WAN IPsec
 gateway.</P>
<H2><A name="notall">Not everyone needs to worry about kernel
 configuration</A></H2>
<P>Note that in many cases you do not need to mess with these.</P>
<P> You may have a Linux distribution which comes with FreeS/WAN
 installed (see this<A href="#products"> list</A>). In that case, you
 need not do a FreeS/WAN installation or a kernel configuration. Of
 course, you might still want to configure and rebuild your kernel to
 improve performance or security. This can be done with standard tools
 described in the<A href="http://www.linuxdoc.org/HOWTO/Kernel-HOWTO.html">
 Kernel HowTo</A>.</P>
<P>If you need to install FreeS/WAN, then you do need to configure a
 kernel. However, you may choose to do that using the simplest
 procedure:</P>
<UL>
<LI>Configure, build and test a kernel for your system before adding
 FreeS/WAN. See the<A href="http://www.linuxdoc.org/HOWTO/Kernel-HOWTO.html">
 Kernel HowTo</A> for details.<STRONG> This step cannot be skipped</STRONG>
. FreeS/WAN needs the results of your configuration.</LI>
<LI>Then use FreeS/WAN's<VAR> make oldgo</VAR> command. This sets
 everything FreeS/WAN needs and retains your values everywhere else.</LI>
</UL>
<P> This document is for those who choose to configure their FreeS/WAN
 kernel themselves.</P>
<H2><A name="assume">Assumptions and notation</A></H2>
<P> Help text for most kernel options is included with the kernel files,
 and is accessible from within the configuration utilities. We assume
 you will refer to that, and to the<A href="http://www.linuxdoc.org/HOWTO/Kernel-HOWTO.html">
 Kernel HowTo</A>, as necessary. This document covers only the
 FreeS/WAN-specific aspects of the problem.</P>
<P> To avoid duplication, this document section does not cover settings
 for the additional IPsec-related kernel options which become available
 after you have patched your kernel with FreeS/WAN patches. There is
 help text for those available from within the configuration utility.</P>
<P> We assume a common configuration in which the FreeS/WAN IPsec
 gateway is also doing ipchains(8) firewalling for a local network, and
 possibly masquerading as well.</P>
<P> Some suggestions below are labelled as appropriate for &quot;a true
 paranoid&quot;. By this we mean they may cause inconvenience and it is not
 entirely clear they are necessary, but they appear to be the safest
 choice. Not using them might entail some risk. Of course one suggested
 mantra for security administrators is: &quot;I know I'm paranoid. I wonder
 if I'm paranoid enough.&quot;</P>
<H3><A name="labels">Labels used</A></H3>
<P> Six labels are used to indicate how options should be set. We mark
 the labels with [square brackets]. For two of these labels, you have no
 choice:</P>
<DL>
<DT>[required]</DT>
<DD>essential for FreeS/WAN operation.</DD>
<DT>[incompatible]</DT>
<DD>incompatible with FreeS/WAN.</DD>
</DL>
<P>those must be set correctly or FreeS/WAN will not work</P>
<P>FreeS/WAN should work with any settings of the others, though of
 course not all combinations have been tested. We do label these in
 various ways, but<EM> these labels are only suggestions</EM>.</P>
<DL>
<DT>[recommended]</DT>
<DD>useful on most FreeS/WAN gateways</DD>
<DT>[disable]</DT>
<DD>an unwelcome complication on a FreeS/WAN gateway.</DD>
<DT>[optional]</DT>
<DD>Your choice. We outline issues you might consider.</DD>
<DT>[anything]</DT>
<DD>This option has no direct effect on FreeS/WAN and related tools, so
 you should be able to set it as you please.</DD>
</DL>
<P> Of course complexity is an enemy in any effort to build secure
 systems.<STRONG> For maximum security, any feature that can reasonably
 be turned off should be</STRONG>. &quot;If in doubt, leave it out.&quot;</P>
<H2><A name="kernelopt">Kernel options for FreeS/WAN</A></H2>
<P> Indentation is based on the nesting shown by 'make menuconfig' with
 a 2.2.16 kernel for the i386 architecture.</P>
<DL>
<DT><A name="maturity">Code maturity and level options</A></DT>
<DD>
<DL>
<DT><A name="devel">Prompt for development ... code/drivers</A></DT>
<DD>[optional] If this is<VAR> no</VAR>, experimental drivers are not
 shown in later menus.
<P>For most FreeS/WAN work,<VAR> no</VAR> is the preferred setting.
 Using new or untested components is too risky for a security gateway.</P>
<P>However, for some hardware (such as the author's network cards) the
 only drivers available are marked<VAR> new/experimental</VAR>. In such
 cases, you must enable this option or your cards will not appear under
 &quot;network device support&quot;. A true paranoid would leave this option off
 and replace the cards.</P>
</DD>
<DT>Processor type and features</DT>
<DD>[anything]</DD>
<DT>Loadable module support</DT>
<DD>
<DL>
<DT>Enable loadable module support</DT>
<DD>[optional] A true paranoid would disable this. An attacker who has
 root access to your machine can fairly easily install a bogus module
 that does awful things, provided modules are enabled. A common tool for
 attackers is a &quot;rootkit&quot;, a set of tools the attacker uses once he or
 she has become root on your system. The kit introduces assorted
 additional compromises so that the attacker will continue to &quot;own&quot; your
 system despite most things you might do to recovery the situation. For
 Linux, there is a tool called<A href="http://www.sans.org/newlook/resources/IDFAQ/knark.htm">
 knark</A> which is basically a rootkit packaged as a kernel module.
<P>With modules disabled, an attacker cannot install a bogus module. The
 only way he can achieve the same effects is to install a new kernel and
 reboot. This is considerably more likely to be noticed.</P>
<P>Many FreeS/WAN gateways run with modules enabled. This simplifies
 some administrative tasks and some ipchains features are available only
 as modules. Once an enemy has root on your machine your security is
 nil, so arguably defenses which come into play only in that situation
 are pointless.</P>
<P></P>
</DD>
<DT>Set version information ....</DT>
<DD>[optional] This provides a check to prevent loading modules compiled
 for a different kernel.</DD>
<DT>Kernel module loader</DT>
<DD>[disable] It gives little benefit on a typical FreeS/WAN gate and
 entails some risk.</DD>
</DL>
</DD>
<DT>General setup</DT>
<DD>We list here only the options that matter for FreeS/WAN.
<DL>
<DT>Networking support</DT>
<DD>[required]</DD>
<DT>Sysctl interface</DT>
<DD>[optional] If this option is turned on and the<VAR> /proc</VAR>
 filesystem installed, then you can control various system behaviours by
 writing to files under<VAR> /proc/sys</VAR>. For example:
<PRE>        echo 1 &gt; /proc/sys/net/ipv4/ipforward</PRE>
 turns IP forwarding on.
<P>Disabling this option breaks many firewall scripts. A true paranoid
 would disable it anyway since it might conceivably be of use to an
 attacker.</P>
</DD>
</DL>
</DD>
<DT>Plug and Play support</DT>
<DD>[anything]</DD>
<DT>Block devices</DT>
<DD>[anything]</DD>
<DT>Networking options</DT>
<DD>
<DL>
<DT>Packet socket</DT>
<DD>[optional] This kernel feature supports tools such as tcpdump(8)
 which communicate directly with network hardware, bypassing kernel
 protocols. This is very much a two-edged sword:
<UL>
<LI>such tools can be very useful to the firewall admin, especially
 during initial testing</LI>
<LI>should an evildoer breach your firewall, such tools could give him
 or her a great deal of information about the rest of your network</LI>
</UL>
 We recommend disabling this option on production gateways.</DD>
<DT><A name="netlink">Kernel/User netlink socket</A></DT>
<DD>[optional] Required if you want to use<A href="#adv"> advanced
 router</A> features.</DD>
<DT>Routing messages</DT>
<DD>[optional]</DD>
<DT>Netlink device emulation</DT>
<DD>[optional]</DD>
<DT>Network firewalls</DT>
<DD>[recommended] You need this if the IPsec gateway also functions as a
 firewall.
<P>Even if the IPsec gateway is not your primary firewall, we suggest
 setting this so that you can protect the gateway with at least basic
 local packet filters.</P>
</DD>
<DT>Socket filtering</DT>
<DD>[disable] This enables an older filtering interface. We suggest
 using ipchains(8) instead. To do that, set the &quot;Network firewalls&quot;
 option just above, and not this one.</DD>
<DT>Unix domain sockets</DT>
<DD>[required] These sockets are used for communication between the<A href="manpage.d/ipsec.8.html">
 ipsec(8)</A> commands and the<A href="manpage.d/ipsec_pluto.8.html">
 ipsec_pluto(8)</A> daemon.</DD>
<DT>TCP/IP networking</DT>
<DD>[required]
<DL>
<DT>IP: multicasting</DT>
<DD>[anything]</DD>
<DT><A name="adv">IP: advanced router</A></DT>
<DD>[optional] This gives you policy routing, which some people have
 used to good advantage in their scripts for FreeS/WAN gateway
 management. It is not used in our distributed scripts, so not required
 unless you want it for custom scripts. It requires the<A href="#netlink">
 netlink</A> interface between kernel code and the iproute2(8) command.</DD>
<DT>IP: kernel level autoconfiguration</DT>
<DD>[disable] It gives little benefit on a typical FreeS/WAN gate and
 entails some risk.</DD>
<DT>IP: firewall packet netlink device</DT>
<DD>[disable]</DD>
<DT>IP: transparent proxy support</DT>
<DD>[optional] This is required in some firewall configurations, but
 should be disabled unless you have a definite need for it.</DD>
<DT>IP: masquerading</DT>
<DD>[optional] Required if you want to use<A href="#non-routable">
 non-routable</A> private IP addresses for your local network.</DD>
<DT>IP: Optimize as router not host</DT>
<DD>[recommended]</DD>
<DT>IP: tunneling</DT>
<DD>[required]</DD>
<DT>IP: GRE tunnels over IP</DT>
<DD>[anything]</DD>
<DT>IP: aliasing support</DT>
<DD>[anything]</DD>
<DT>IP: ARP daemon support (EXPERIMENTAL)</DT>
<DD>Not required on most systems, but might prove useful on
 heavily-loaded gateways.</DD>
<DT>IP: TCP syncookie support</DT>
<DD>[recommended] It provides a defense against a<A href="#DOS"> denial
 of service attack</A> which uses bogus TCP connection requests to waste
 resources on the victim machine.</DD>
<DT>IP: Reverse ARP</DT>
<DD></DD>
<DT>IP: large window support</DT>
<DD>[recommended] unless you have less than 16 meg RAM</DD>
</DL>
</DD>
<DT>IPv6</DT>
<DD>[optional] FreeS/WAN does not currently support IPv6, though work on
 integrating FreeS/WAN with the Linux IPv6 stack has begun.<A href="#ipv6">
 Details</A>.
<P> It should be possible to use IPv4 FreeS/WAN on a machine which also
 does IPv6. This combination is not yet well tested. We would be quite
 interested in hearing results from anyone expermenting with it, via the<A
href="mail.html"> mailing list</A>.</P>
<P> We do not recommend using IPv6 on production FreeS/WAN gateways
 until more testing has been done.</P>
</DD>
<DT>Novell IPX</DT>
<DD>[disable]</DD>
<DT>Appletalk</DT>
<DD>[disable] Quite a few Linux installations use IP but also have some
 other protocol, such as Appletalk or IPX, for communication with local
 desktop machines. In theory it should be possible to configure IPsec
 for the IP side of things without interfering with the second protocol.
<P>We do not recommend this. Keep the software on your gateway as simple
 as possible. If you need a Linux-based Appletalk or IPX server, use a
 separate machine.</P>
</DD>
</DL>
</DD>
<DT>Telephony support</DT>
<DD>[anything]</DD>
<DT>SCSI support</DT>
<DD>[anything]</DD>
<DT>I2O device support</DT>
<DD>[anything]</DD>
<DT>Network device support</DT>
<DD>[anything] should work, but there are some points to note.
<P>The development team test almost entirely on 10 or 100 megabit
 Ethernet and modems. In principle, any device that can do IP should be
 just fine for IPsec, but in the real world any device that has not been
 well-tested is somewhat risky. By all means try it, but don't bet your
 project on it until you have solid test results.</P>
<P>If you disabled experimental drivers in the<A href="#maturity"> Code
 maturity</A> section above, then those drivers will not be shown here.
 Check that option before going off to hunt for missing drivers.</P>
<P>If you want Linux to automatically find more than one ethernet
 interface at boot time, you need to:</P>
<UL>
<LI>compile the appropriate driver(s) into your kernel. Modules will not
 work for this</LI>
<LI>add a line such as
<PRE>
   append=&quot;ether=0,0,eth0 ether=0,0,eth1&quot;
</PRE>
 to your /etc/lilo.conf file. In some cases you may need to specify
 parameters such as IRQ or base address. The example uses &quot;0,0&quot; for
 these, which tells the system to search. If the search does not succeed
 on your hardware, then you should retry with explicit parameters. See
 the lilo.conf(5) man page for details.</LI>
<LI>run lilo(8)</LI>
</UL>
 Having Linux find the cards this way is not necessary, but is usually
 more convenient than loading modules in your boot scripts.</DD>
<DT>Amateur radio support</DT>
<DD>[anything]</DD>
<DT>IrDA (infrared) support</DT>
<DD>[anything]</DD>
<DT>ISDN subsystem</DT>
<DD>[anything]</DD>
<DT>Old CDROM drivers</DT>
<DD>[anything]</DD>
<DT>Character devices</DT>
<DD>The only required character device is:
<DL>
<DT>random(4)</DT>
<DD>[required] This is a source of<A href="#random"> random</A> numbers
 which are required for many cryptographic protocols, including several
 used in IPsec.
<P>If you are comfortable with C source code, it is likely a good idea
 to go in and adjust the<VAR> #define</VAR> lines in<VAR>
 /usr/src/linux/drivers/char/random.c</VAR> to ensure that all sources
 of randomness are enabled. Relying solely on keyboard and mouse
 randomness is dubious procedure for a gateway machine. You could also
 increase the randomness pool size from the default 512 bytes (128
 32-bit words).</P>
</DD>
</DL>
</DD>
<DT>Filesystems</DT>
<DD>[anything] should work, but we suggest limiting a gateway machine to
 the standard Linux ext2 filesystem in most cases.</DD>
<DT>Network filesystems</DT>
<DD>[disable] These systems are an unnecessary risk on an IPsec gateway.</DD>
<DT>Console drivers</DT>
<DD>[anything]</DD>
<DT>Sound</DT>
<DD>[anything] should work, but we suggest enabling sound only if you
 plan to use audible alarms for firewall problems.</DD>
<DT>Kernel hacking</DT>
<DD>[disable] This might be enabled on test machines, but should not be
 on production gateways.</DD>
</DL>
</DD>
</DL>
<HR>
<H1><A name="adv_config">Other configuration possibilities</A></H1>
<P>This document describes various options for FreeS/WAN configuration
 which are less used or more complex (often both) than the standard
 cases described in our<A href="#config"> config</A> and<A href="#quick_guide">
 quickstart</A> documents.</P>
<H2><A name="thumb">Some rules of thumb about configuration</A></H2>
<H3><A name="cheap.tunnel">Tunnels are cheap</A></H3>
<P>Nearly all of the overhead in IPsec processing is in the encryption
 and authentication of packets. Our<A href="performance.html">
 performance</A> document discusses these overheads.</P>
<P>Beside those overheads, the cost of managing additional tunnels is
 trivial. Whether your gateway supports one tunnel or ten just does not
 matter. A hundred might be a problem; there is a<A href="#biggate">
 section</A> on this in the performance document.</P>
<P>So, in nearly all cases, if using multiple tunnels gives you a
 reasonable way to describe what you need to do, you should describe it
 that way in your configuration files.</P>
<P>For example, one user recently asked on a mailing list about this
 network configuration:</P>
<PRE>        netA---gwA---gwB---netB
                            |----netC

   netA and B are secured netC not.
   netA and gwA can not access netC</PRE>
<P>The user had constructed only one tunnel, netA to netB, and wanted to
 know how to use ip-route to get netC packets into it. This is entirely
 unnecessary. One of the replies was:</P>
<PRE>  The simplest way and indeed the right way to
  solve this problem is to set up two connections:

        leftsubnet=NetA
        left=gwA
        right=gwB
        rightsubnet=NetB
  and
        leftsubnet=NetA
        left=gwA
        right=gwB
        rightsubnet=NetC</PRE>
<P>This would still be correct even if we added nets D, E, F, ... to the
 above diagram and needed twenty tunnels.</P>
<P>Of course another possibility would be to just use one tunnel, with a
 subnet mask that includes both netB and netC (or B, C, D, ...). See
 next section.</P>
<P>In general, you can construct as many tunnels as you need. Networks
 like netC in this example that do not connect directly to the gateway
 are fine, as long as the gateway can route to them.</P>
<P>The number of tunnels can become an issue if it reaches 50 or so.
 This is discussed in the<A href="#biggate"> performance</A> document.
 Look there for information on supporting hundreds of Road Warriors from
 one gateway.</P>
<P>If you find yourself with too many tunnels for some reason like
 having eight subnets at one location and nine at another so you end up
 with 9*8=72 tunnels, read the next section here.</P>
<H3><A name="subnet.size">Subnet sizes</A></H3>
<P>The subnets used in<VAR> leftsubnet</VAR> and<VAR> rightsubnet</VAR>
 can be of any size that fits your needs, and they need not correspond
 to physical networks.</P>
<P>You adjust the size by changing the<A href="#subnet"> subnet mask</A>
, the number after the slash in the subnet description. For example</P>
<UL>
<LI>in 192.168.100.0/24 the /24 mask says 24 bits are used to designate
 the network. This leave 8 bits to label machines. This subnet has 256
 addresses. .0 and .255 are reserved, so it can have 254 machines.</LI>
<LI>A subnet with a /23 mask would be twice as large, 512 addresses.</LI>
<LI>A subnet with a /25 mask would be half the size, 128 addresses.</LI>
<LI>/0 is the whole Internet</LI>
<LI>/32 is a single machine</LI>
</UL>
<P>As an example of using these in connection descriptions, suppose your
 company's head office has four physical networks using the address
 ranges:</P>
<DL>
<DT>192.168.100.0/24</DT>
<DD>development</DD>
<DT>192.168.101.0/24</DT>
<DD>production</DD>
<DT>192.168.102.0/24</DT>
<DD>marketing</DD>
<DT>192.168.103.0/24</DT>
<DD>administration</DD>
</DL>
<P>You can use exactly those subnets in your connection descriptions, or
 use larger subnets to grant broad access if required:</P>
<DL>
<DT>leftsubnet=192.168.100.0/24</DT>
<DD>remote hosts can access only development</DD>
<DT>leftsubnet=192.168.100.0/23</DT>
<DD>remote hosts can access development or production</DD>
<DT>leftsubnet=192.168.102.0/23</DT>
<DD>remote hosts can access marketing or administration</DD>
<DT>leftsubnet=192.168.100.0/22</DT>
<DD>remote hosts can access any of the four departments</DD>
</DL>
<P>or use smaller subnets to restrict access:</P>
<DL>
<DT>leftsubnet=192.168.103.0/24</DT>
<DD>remote hosts can access any machine in administration</DD>
<DT>leftsubnet=192.168.103.64/28</DT>
<DD>remote hosts can access only certain machines in administration.</DD>
<DT>leftsubnet=192.168.103.42/32</DT>
<DD>remote hosts can access only one particular machine in
 administration</DD>
</DL>
<P>To be exact, 192.68.103.64/28 means all addresses whose top 28 bits
 match 192.168.103.64. There are 16 of these because there are 16
 possibilities for the remainingg 4 bits. Their addresses are
 192.168.103.64 to 192.168.103.79.</P>
<P>Each connection description can use a different subnet if required.</P>
<P>It is possible to use all the examples above on the same FreeS/WAN
 gateway, each in a different connection description, perhaps for
 different classes of user or for different remote offices.</P>
<P>It is also possible to have multiple tunnels using different<VAR>
 leftsubnet</VAR> descriptions with the same<VAR> right</VAR>. For
 example, when the marketing manager is on the road he or she might have
 access to:</P>
<DL>
<DT>leftsubnet=192.168.102.0/24</DT>
<DD>all machines in marketing</DD>
<DT>192.168.101.32/29</DT>
<DD>some machines in production</DD>
<DT>leftsubnet=192.168.103.42/32</DT>
<DD>one particular machine in administration</DD>
</DL>
<P>This takes three tunnels, but tunnels are cheap. If the laptop is set
 up to build all three tunnels automatically, then he or she can access
 all these machines concurrently, perhaps from different windows.</P>
<H3><A name="example.more">Other network layouts</A></H3>
<P>Here is the usual network picture for a site-to-site VPN::</P>
<PRE>     Sunset==========West------------------East=========Sunrise
           local net       untrusted net       local net</PRE>
<P>and for the Road Warrior::</P>
<PRE>                                           telecommuter's PC or
                                           traveller's laptop
     Sunset==========West------------------East
         corporate LAN     untrusted net</PRE>
<P>Other configurations are also possible.</P>
<H4><A name="internet.subnet">The Internet as a big subnet</A></H4>
<P>A telecommuter might have:</P>
<PRE>     Sunset==========West------------------East ================= firewall --- the Internet
         home network      untrusted net        corporate network</PRE>
<P>This can be described as a special case of the general
 subnet-to-subnet connection. The subnet on the right is 0.0.0.0/0, the
 whole Internet.</P>
<P>West (the home gateway) can have its firewall rules set up so that
 only IPsec packets to East are allowed out. It will then behave as if
 its only connection to the world was a wire to East.</P>
<P>When machines on the home network need to reach the Internet, they do
 so via the tunnel, East and the corporate firewall. From the viewpoint
 of the Internet (perhaps of some EvilDoer trying to break in!), those
 home office machines are behind the firewall and protected by it.</P>
<H4><A name="wireless.config">Wireless</A></H4>
<P>Another possible configuration comes up when you do not trust the
 local network, either because you have very high security standards or
 because your are using easily-intercepted wireless signals.</P>
<P>Some wireless networks have built-in encryption called<A href="#WEP">
 WEP</A>, but its security is dubious. It is a fairly common practice to
 use IPsec instead.</P>
<P>In this case, part of your network may look like this:</P>
<PRE>          West-----------------------------East == the rest of your network
     workstation   untrusted wireless net</PRE>
<P>Of course, there would likely be several wireless workstations, each
 with its own IPsec tunnel to the East gateway.</P>
<P>The connection descriptions look much like Road Warrior descriptions:</P>
<UL>
<LI>each workstation should have its own unique
<UL>
<LI>identifier for IPsec</LI>
<LI>RSA key</LI>
<LI>connection description.</LI>
</UL>
</LI>
<LI>on the gateway, use<VAR> left=%any</VAR>, or the workstation IP
 address</LI>
<LI>on workstations,<VAR> left=%defaultroute</VAR>, or the workstation
 IP address</LI>
<LI><VAR>leftsubnet=</VAR> is not used.</LI>
</UL>
<P>The<VAR> rightsubnet=</VAR> parameter might be set in any of several
 ways:</P>
<DL>
<DT>rightsubnet=0.0.0.0/0</DT>
<DD>allowing workstations to access the entire Internet (see<A href="#internet.subnet">
 above</A>)</DD>
<DT>rightsubnet=a.b.c.0/24</DT>
<DD>allowing access to your entire local network</DD>
<DT>rightsubnet=a.b.c.d/32</DT>
<DD>restricting the workstation to connecting to a particular server</DD>
</DL>
<P>Of course you can mix and match these as required. For example, a
 university might allow faculty full Internet access while letting
 student laptops connect only to a group of lab machines.</P>
<H2><A name="choose">Choosing connection types</A></H2>
<P>One choice you need to make before configuring additional connections
 is what type or types of connections you will use. There are several
 options, and you can use more than one concurrently.</P>
<H3><A name="man-auto">Manual vs. automatic keying</A></H3>
<P>IPsec allows two types of connections, with manual or automatic
 keying. FreeS/WAN starts them with commands such as:</P>
<PRE>        ipsec manual --up <VAR>name</VAR>
        ipsec auto --up <VAR>name</VAR></PRE>
<P>The difference is in how they are keyed.</P>
<DL>
<DT><A href="#manual">Manually keyed</A> connections</DT>
<DD>use keys stored in<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf</A>
.</DD>
<DT><A href="#auto">Automatically keyed</A> connections</DT>
<DD>use keys automatically generated by the Pluto key negotiation
 daemon. The key negotiation protocol,<A href="#IKE"> IKE</A>, must
 authenticate the other system. (It is vulnerable to a<A href="#middle">
 man-in-the-middle attack</A> if used without authentication.) We
 currently support two authentication methods:
<UL>
<LI>using shared secrets stored in<A href="manpage.d/ipsec.secrets.5.html">
 ipsec.secrets</A>.</LI>
<LI>RSA<A href="#public"> public key</A> authentication, with our
 machine's private key in<A href="manpage.d/ipsec.secrets.5.html">
 ipsec.secrets</A>. Public keys for other machines may either be placed
 in<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf</A> or provided via
 DNS.</LI>
</UL>
<P>A third method, using RSA keys embedded in<A href="#X509"> X.509</A>
 certtificates, is provided by user<A href="#patch"> patches</A>.</P>
</DD>
</DL>
<P><A href="#manual">Manually keyed</A> connections provide weaker
 security than<A href="#auto"> automatically keyed</A> connections. An
 opponent who reads ipsec.secrets(5) gets your encryption key and can
 read all data encrypted by it. If he or she has an archive of old
 messages, all of them back to your last key change are also readable.</P>
<P>With automatically-(re)-keyed connections, an opponent who reads
 ipsec.secrets(5) gets the key used to authenticate your system in IKE
 -- the shared secret or your private key, depending what authentication
 mechanism is in use. However, he or she does not automatically gain
 access to any encryption keys or any data.</P>
<P>An attacker who has your authentication key can mount a<A href="#middle">
 man-in-the-middle attack</A> and, if that succeeds, he or she will get
 encryption keys and data. This is a serious danger, but it is better
 than having the attacker read everyting as soon as he or she breaks
 into ipsec.secrets(5).. Moreover, the keys change often so an opponent
 who gets one key does not get a large amount of data. To read all your
 data, he or she would have to do a man-in-the-middle attack at every
 key change.</P>
<P>We discuss using<A href="#prodman"> manual keying in production</A>
 below, but this is<STRONG> not recommended</STRONG> except in special
 circumstances, such as needing to communicate with some implementation
 that offers no auto-keyed mode compatible with FreeS/WAN.</P>
<P>Manual keying may also be useful for testing. There is some
 discussion of this in our<A href="#man4debug"> FAQ</A>.</P>
<H3><A name="auto-auth">Authentication methods for auto-keying</A></H3>
<P>The IKE protocol which Pluto uses to negotiate connections between
 gateways must use some form of authentication of peers. A gateway must
 know who it is talking to before it can create a secure connection. We
 support two basic methods for this authentication:</P>
<UL>
<LI>shared secrets, stored in<A href="manpage.d/ipsec.secrets.5.html">
 ipsec.secrets(5)</A></LI>
<LI>RSA authentication</LI>
</UL>
<P>There are, howver, several variations on the RSA theme, using
 different methods of managing the RSA keys:</P>
<UL>
<LI>our RSA private key in<A href="manpage.d/ipsec.secrets.5.html">
 ipsec.secrets(5)</A> with other gateways' public keys
<DL>
<DT>either</DT>
<DD>stored in<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf(5)</A></DD>
<DT>or</DT>
<DD>looked up via<A href="#DNS"> DNS</A></DD>
</DL>
</LI>
<LI>authentication with<A href="#X509"> x.509</A> certificates.; See our<A
href="#patch"> links section</A> for information on user-contributed
 patches for this.:</LI>
</UL>
<P>Public keys in<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf(5</A>
) give a reasonably straightforward method of specifying keys for
 explicitly configured connections.</P>
<P>Putting public keys in DNS allows us to support<A href="#carpediem">
 opportunistic encryption</A>. Any two FreeS/WAN gateways can provide
 secure communication, without either of them having any preset
 information about the other.</P>
<P>X.509 certificates may be required to interface to various<A href="#PKI">
 PKI</A>s.</P>
<H3><A name="adv-pk">Advantages of public key methods</A></H3>
<P>Authentication with a<A href="#public"> public key</A> method such as<A
href="#RSA"> RSA</A> has some important advantages over using shared
 secrets.</P>
<UL>
<LI>no problem of secure transmission of secrets
<UL>
<LI>A shared secret must be shared, so you have the problem of
 transmitting it securely to the other party. If you get this wrong, you
 have no security.</LI>
<LI>With a public key technique, you transmit only your public key. The
 system is designed to ensure that it does not matter if an enemy
 obtains public keys. The private key never leaves your machine.</LI>
</UL>
</LI>
<LI>easier management
<UL>
<LI>Suppose you have 20 branch offices all connecting to one gateway at
 head office, and all using shared secrets. Then the head office admin
 has 20 secrets to manage. Each of them must be kept secret not only
 from outsiders, but also from 19 of the branch office admins. The
 branch office admins have only one secret each to manage.
<P>If the branch offices need to talk to each other, this becomes
 problematic. You need another 20*19/2 = 190 secrets for
 branch-to-branch communication, each known to exactly two branches. Now
 all the branch admins have the headache of handling 20 keys, each
 shared with exactly one other branch or with head office.</P>
<P>For larger numbers of branches, the number of connections and secrets
 increases quadratically and managing them becomes a nightmare. A
 1000-gateway fully connected network needs 499,500 secrets, each known
 to exactly two players. There are ways to reduce this problem, for
 example by introducing a central key server, but these involve
 additional communication overheads, more administrative work, and new
 threats that must be carefully guarded against.</P>
</LI>
<LI>With public key techniques, the<EM> only</EM> thing you have to keep
 secret is your private key, and<EM> you keep that secret from everyone</EM>
.
<P>As network size increaes, the number of public keys used increases
 linearly with the number of nodes. This still requires careful
 administration in large applications, but is nothing like the disaster
 of a quadratic increase. On a 1000-gateway network, you have 1000
 private keys, each of which must be kept secure on one machine, and
 1000 public keys which must be distributed. This is not a trivial
 problem, but it is manageable.</P>
</LI>
</UL>
</LI>
<LI>does not require fixed IP addresses
<UL>
<LI>When shared secrets are used in IPsec, the responder must be able to
 tell which secret to use by looking at the IP address on the incoming
 packets. When the other parties do not have a fixed IP address to be
 identified by (for example, on nearly all dialup ISP connections and
 many cable or ADSL links), this does not work well -- all must share
 the same secret!</LI>
<LI>When RSA authentication is in use, the initiator can identify itself
 by name before the key must be determined. The responder then checks
 that the message is signed with the public key corresponding to that
 name.</LI>
</UL>
</LI>
</UL>
<P>There is also a disadvantage:</P>
<UL>
<LI>your private key is a single point of attack, extremely valuable to
 an enemy
<UL>
<LI>with shared secrets, an attacker who steals your ipsec.secrets file
 can impersonate you or try<A href="#middle"> man-in-the-middle</A>
 attacks, but can only attack connections described in that file</LI>
<LI>an attacker who steals your private key gains the chance to attack
 not only existing connections<EM> but also any future connections</EM>
 created using that key</LI>
</UL>
</LI>
</UL>
<P>This is partly counterbalanced by the fact that the key is never
 transmitted and remains under your control at all times. It is likely
 necessary, however, to take account of this in setting security policy.
 For example, you should change gateway keys when an administrator
 leaves the company, and should change them periodically in any case.</P>
<P>Overall, public key methods are<STRONG> more secure, more easily
 managed and more flexible</STRONG>. We recommend that they be used for
 all connections, unless there is a compelling reason to do otherwise.</P>
<H2><A name="prodsecrets">Using shared secrets in production</A></H2>
<P>Generally, public key methods are preferred for reasons given above,
 but shared secrets can be used with no loss of security, just more work
 and perhaps more need to take precautions.</P>
<P>What I call &quot;shared secrets&quot; are sometimes also called &quot;pre-shared
 keys&quot;. They are used only for for authentication, never for encryption.
 Calling them &quot;pre-shared keys&quot; has confused some users into thinking
 they were encryption keys, so I prefer to avoid the term..</P>
<P>If you are interoperating with another IPsec implementation, you may
 find its documentation calling them &quot;passphrases&quot;.</P>
<H3><A name="secrets">Putting secrets in ipsec.secrets(5)</A></H3>
<P>If shared secrets are to be used to<A href="#authentication">
 authenticate</A> communication for the<A href="#DH"> Diffie-Hellman</A>
 key exchange in the<A href="#IKE"> IKE</A> protocol, then those secrets
 must be stored in<VAR> /etc/ipsec.secrets</VAR>. For details, see the<A href="manpage.d/ipsec.secrets.5.html">
 ipsec.secrets(5)</A> man page.</P>
<P>A few considerations are vital:</P>
<UL>
<LI>make the secrets long and unguessable. Since they need not be
 remembered by humans, very long ugly strings may be used. We suggest
 using our<A href="manpage.d/ipsec_ranbits.8.html"> ipsec_ranbits(8)</A>
 utility to generate long (128 bits or more) random strings.</LI>
<LI>transmit secrets securely. You have to share them with other
 systems, but you lose if they are intercepted and used against you. Use<A
href="#PGP"> PGP</A>,<A href="#ssh"> SSH</A>, hand delivery of a floppy
 disk which is then destroyed, or some other trustworthy method to
 deliver them.</LI>
<LI>store secrets securely, in root-owned files with permissions
 rw------.</LI>
<LI>limit sharing of secrets. Alice, Bob, Carol and Dave may all talk to
 each other, but only Alice and Bob should know the secret for an
 Alice-Bob link.</LI>
<LI><STRONG>do not share private keys</STRONG>. The private key for RSA
 authentication of your system is stored in<A href="manpage.d/ipsec.secrets.5.html">
 ipsec.secrets(5)</A>, but it is a different class of secret from the
 pre-shared keys used for the &quot;shared secret&quot; authentication. No-one but
 you should have the RSA private key.</LI>
</UL>
<P>Each line has the IP addresses of the two gateways plus the secret.
 It should look something like this:</P>
<PRE>        10.0.0.1 11.0.0.1 : PSK &quot;jxTR1lnmSjuj33n4W51uW3kTR55luUmSmnlRUuWnkjRj3UuTV4T3USSu23Uk55nWu5TkTUnjT&quot;</PRE>
<P><VAR>PSK</VAR> indicates the use of a<STRONG> p</STRONG>re-<STRONG>s</STRONG>
hared<STRONG> k</STRONG>ey. The quotes and the whitespace shown are
 required.</P>
<P>You can use any character string as your secret. For security, it
 should be both long and extremely hard to guess. We provide a utility
 to generate such strings,<A href="manpage.d/ipsec_ranbits.8.html">
 ipsec_ranbits(8)</A>.</P>
<P>You want the same secret on the two gateways used, so you create a
 line with that secret and the two gateway IP addresses. The
 installation process supplies an example secret, useful<EM> only</EM>
 for testing. You must change it for production use.</P>
<H3><A name="securing.secrets">File security</A></H3>
<P>You must deliver this file, or the relevant part of it, to the other
 gateway machine by some<STRONG> secure</STRONG> means.<EM> Don't just
 FTP or mail the file!</EM> It is vital that the secrets in it remain
 secret. An attacker who knew those could easily have<EM> all the data
 on your &quot;secure&quot; connection</EM>.</P>
<P>This file must be owned by root and should have permissions<VAR>
 rw-------</VAR>.</P>
<H3><A name="notroadshared">Shared secrets for road warriors</A></H3>
<P>You can use a shared secret to support a single road warrior
 connecting to your gateway, and this is a reasonable thing to do in
 some circumstances. Public key methods have advantages, discussed<A href="#choose">
 above</A>, but they are not critical in this case.</P>
<P>To do this, the line in ipsec.secrets(5) is something like:</P>
<PRE>        10.0.0.1 0.0.0.0 : PSK &quot;jxTR1lnmSjuj33n4W51uW3kTR55luUmSmnlRUuWnkjRj3UuTV4T3USSu23Uk55nWu5TkTUnjT&quot;</PRE>
 where the<VAR> 0.0.0.0</VAR> means that any IP address is acceptable.
<P><STRONG>For more than one road warrior, shared secrets are<EM> not</EM>
 recommended.</STRONG> If shared secrets are used, then when the
 responder needs to look up the secret, all it knows about the sender is
 an IP address. This is fine if the sender is at a fixed IP address
 specified in the config file. It is also fine if only one road warrior
 uses the wildcard<VAR> 0.0.0.0</VAR> address. However, if you have more
 than one road warrior using shared secret authentication, then they
 must all use that wildcard and therefore<STRONG> all road warriors
 using PSK autentication must use the same secret</STRONG>. Obviously,
 this is insecure.</P>
<P><STRONG>For multiple road warriors, use public key authentication.</STRONG>
 Each roadwarrior can then have its own identity (our<VAR> leftid=</VAR>
 or<VAR> rightid=</VAR> parameters), its own public/private key pair,
 and its own secure connection.</P>
<H2><A name="prodman">Using manual keying in production</A></H2>
<P>Generally,<A href="#auto"> automatic keying</A> is preferred over<A href="#manual">
 manual keying</A> for production use because it is both easier to
 manage and more secure. Automatic keying frees the admin from much of
 the burden of managing keys securely, and can provide<A href="#PFS">
 perfect forward secrecy</A>. This is discussed in more detail<A href="#man-auto">
 above</A>.</P>
<P>However, it is possible to use manual keying in production if that is
 what you want to do. This might be necessary, for example, in order to
 interoperate with some device that either does not provide automatic
 keying or provides it in some version we cannot talk to.</P>
<P>Note that with manual keying<STRONG> all security rests with the keys</STRONG>
. If an adversary acquires your keys, you've had it. He or she can read
 everything ever sent with those keys, including old messages he or she
 may have archived.</P>
<P>You need to<STRONG> be really paranoid about keys</STRONG> if you're
 going to rely on manual keying for anything important.</P>
<UL>
<LI>keep keys in files with 600 permissions, owned by root</LI>
<LI>be extremely careful about security of your gateway systems. Anyone
 who breaks into a gateway and gains root privileges can get all your
 keys and read everything ever encrypted with those keys, both old
 messages he has archived and any new ones you may send.</LI>
<LI>change keys regularly. This can be a considerable bother, (and
 provides an excellent reason to consider automatic keying instead), but
 it is<EM> absolutely essential</EM> for security. Consider a manually
 keyed system in which you leave the same key in place for months:
<UL>
<LI>an attacker can have a very large sample of text sent with that key
 to work with. This makes various cryptographic attacks much more likely
 to succeed.</LI>
<LI>The chances of the key being compromised in some non-cryptographic
 manner -- a spy finds it on a discarded notepad, someone breaks into
 your server or your building and steals it, a staff member is bribed,
 tricked, seduced or coerced into revealing it, etc. -- also increase
 over time.</LI>
<LI>a successful attacker can read everything ever sent with that key.
 This makes any successful attack extremely damaging.</LI>
</UL>
 It is clear that you must change keys often to have any useful
 security. The only question is how often.</LI>
<LI>use<A href="#PGP"> PGP</A> or<A href="#ssh"> SSH</A> for all key
 transfers</LI>
<LI>don't edit files with keys in them when someone can look over your
 shoulder</LI>
<LI>worry about network security; could someone get keys by snooping
 packets on the LAN between your X desktop and the gateway?</LI>
<LI>lock up your backup tapes for the gateway system</LI>
<LI>... and so on</LI>
</UL>
<P>Linux FreeS/WAN provides some facilities to help with this. In
 particular, it is good policy to<STRONG> keep keys in separate files</STRONG>
 so you can edit configuration information in /etc/ipsec.conf without
 exposing keys to &quot;shoulder surfers&quot; or network snoops. We support this
 with the<VAR> also=</VAR> and<VAR> include</VAR> syntax in<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A>.</P>
<P>See the last example in our<A href="examples"> examples</A> file. In
 the /etc/ipsec.conf<VAR> conn samplesep</VAR> section, it has the line:</P>
<PRE>        also=samplesep-keys</PRE>
<P>which tells the &quot;ipsec manual&quot; script to insert the configuration
 description labelled &quot;samplesep-keys&quot; if it can find it. The
 /etc/ipsec.conf file must also have a line such as:</P>
<PRE>include ipsec.*.conf</PRE>
<P>which tells it to read other files. One of those other files then
 might contain the additional data:</P>
<PRE>conn samplesep-keys
  spi=0x200
  esp=3des-md5-96
  espenckey=0x01234567_89abcdef_02468ace_13579bdf_12345678_9abcdef0
  espauthkey=0x12345678_9abcdef0_2468ace0_13579bdf</PRE>
<P>The first line matches the label in the &quot;also=&quot; line, so the indented
 lines are inserted. The net effect is exactly as if the inserted lines
 had occurred in the original file in place of the &quot;also=&quot; line.</P>
<P>Variables set here are:</P>
<DL>
<DT>spi</DT>
<DD>A number needed by the manual keying code. Any 3-digit hex number
 will do, but if you have more than one manual connection then<STRONG>
 spi must be different</STRONG> for each connection.</DD>
<DT>esp</DT>
<DD>Options for<A href="#ESP"> ESP</A> (Encapsulated Security Payload),
 the usual IPsec encryption mode. Settings here are for<A href="#encryption">
 encryption</A> using<A href="#3DES"> triple DES</A> and<A href="#authentication">
 authentication</A> using<A href="#MD5"> MD5</A>. Note that encryption
 without authentication should not be used; it is insecure.</DD>
<DT>espenkey</DT>
<DD>Key for ESP encryption. Here, a 192-bit hex number for triple DES.</DD>
<DT>espauthkey</DT>
<DD>Key for ESP authentication. Here, a 128-bit hex number for MD5.</DD>
</DL>
<P><STRONG>Note</STRONG> that the<STRONG> example keys we supply</STRONG>
 are intended<STRONG> only for testing</STRONG>. For real use, you
 should go to automatic keying. If that is not possible, create your own
 keys for manual mode and keep them secret</P>
<P>Of course, any files containing keys<STRONG> must</STRONG> have 600
 permissions and be owned by root.</P>
<P>If you connect in this way to multiple sites, we recommend that you
 keep keys for each site in a separate file and adopt some naming
 convention that lets you pick them all up with a single &quot;include&quot; line.
 This minimizes the risk of losing several keys to one error or attack
 and of accidentally giving another site admin keys which he or she has
 no business knowing.</P>
<P>Also note that if you have multiple manually keyed connections on a
 single machine, then the<VAR> spi</VAR> parameter must be different for
 each one. Any 3-digit hex number is OK, provided they are different for
 each connection. We reserve the range 0x100 to 0xfff for manual
 connections. Pluto assigns SPIs from 0x1000 up for automatically keyed
 connections.</P>
<P>If<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf(5)</A> contains
 keys for manual mode connections, then it too must have permissions<VAR>
 rw-------</VAR>. We recommend instead that, if you must manual keying
 in production, you keep the keys in separate files.</P>
<P>Note also that<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf</A>
 is installed with permissions<VAR> rw-r--r--</VAR>. If you plan to use
 manually keyed connections for anything more than initial testing, you<B>
 must</B>:</P>
<UL>
<LI>either change permissions to<VAR> rw-------</VAR></LI>
<LI>or store keys separately in secure files and access them via include
 statements in<A href="manpage.d/ipsec.conf.5.html"> ipsec.conf</A>.</LI>
</UL>
<P>We recommend the latter method for all but the simplest
 configurations.</P>
<H3><A name="ranbits">Creating keys with ranbits</A></H3>
<P>You can create new<A href="#random"> random</A> keys with the<A href="manpage.d/ipsec_ranbits.8.html">
 ranbits(8)</A> utility. For example, the commands:</P>
<PRE>      umask 177
      ipsec ranbits 192  &gt; temp
      ipsec ranbits 128 &gt;&gt; temp</PRE>
<P>create keys in the sizes needed for our default algorithms:</P>
<UL>
<LI>192-bit key for<A href="#3DES"> 3DES</A> encryption
<BR> (only 168 bits are used; parity bits are ignored)</LI>
<LI>128-bit key for keyed<A href="#MD5"> MD5</A> authentication</LI>
</UL>
<P>If you want to use<A href="#SHA"> SHA</A> instead of<A href="#MD5">
 MD5</A>, that requires a 160-bit key</P>
<P>Note that any<STRONG> temporary files</STRONG> used must be kept<STRONG>
 secure</STRONG> since they contain keys. That is the reason for the
 umask command above. The temporary file should be deleted as soon as
 you are done with it. You may also want to change the umask back to its
 default value after you are finished working on keys.</P>
<P>The ranbits utility may pause for a few seconds if not enough entropy
 is available immediately. See ipsec_ranbits(8) and random(4) for
 details. You may wish to provide some activity to feed entropy into the
 system. For example, you might move the mouse around, type random
 characters, or do<VAR> du /usr &gt; /dev/null</VAR> in the background.</P>
<H2><A name="boot">Setting up connections at boot time</A></H2>
<P>You can tell the system to set up connections automatically at boot
 time by putting suitable stuff in /etc/ipsec.conf on both systems. The
 relevant section of the file is labelled by a line reading<VAR> config
 setup</VAR>.</P>
<P>Details can be found in the<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A> man page. We also provide a file of<A href="examples">
 example configurations</A>.</P>
<P>The most likely options are something like:</P>
<DL>
<DT>interfaces=&quot;ipsec0=eth0 ipsec1=ppp0&quot;</DT>
<DD>Tells KLIPS which interfaces to use. Up to four interfaces numbered
 ipsec[0-3] are supported. Each interface can support an arbitrary
 number of tunnels.
<P>Note that for PPP, you give the ppp[0-9] device name here, not the
 underlying device such as modem (or eth1 if you are using PPPoE).</P>
</DD>
<DT>interfaces=%defaultroute</DT>
<DD>Alternative setting, useful in simple cases. KLIPS will pick up both
 its interface and the next hop information from the settings of the
 Linux default route.</DD>
<DT>forwardcontrol=no</DT>
<DD>Normally &quot;no&quot;. Set to &quot;yes&quot; if the IP forwarding option is disabled
 in your network configuration. (This can be set as a kernel
 configuration option or later. e.g. on Redhat, it's in
 /etc/sysconfig/network and on SuSE you can adjust it with Yast.) Linux
 FreeS/WAN will then enable forwarding when starting up and turn it off
 when going down. This is used to ensure that no packets will be
 forwarded before IPsec comes up and takes control.</DD>
<DT>syslog=daemon.error</DT>
<DD>Used in messages to the system logging daemon (syslogd) to specify
 what type of software is sending the messages. If the settings are
 &quot;daemon.error&quot; as in our example, then syslogd treats the messages as
 error messages from a daemon.
<P>Note that<A href="#Pluto"> Pluto</A> does not currently pay attention
 to this variable. The variable controls setup messages only.</P>
</DD>
<DT>klipsdebug=</DT>
<DD>Debug settings for<A href="#KLIPS"> KLIPS</A>.</DD>
<DT>plutodebug=</DT>
<DD>Debug settings for<A href="#Pluto"> Pluto</A>.</DD>
<DT>... for both the above DEBUG settings</DT>
<DD>Normally, leave empty as shown above for no debugging output.
<BR> Use &quot;all&quot; for maximum information.
<BR> See ipsec_klipsdebug(8) and ipsec_pluto(8) man page for other
 options. Beware that if you set /etc/ipsec.conf to enable debug output,
 your system's log files may get large quickly.</DD>
<DT>dumpdir=/safe/directory</DT>
<DD>Normally, programs started by ipsec setup don't crash. If they do,
 by default, no core dump will be produced because such dumps would
 contain secrets. If you find you need to debug such crashes, you can
 set dumpdir to the name of a directory in which to collect the core
 file.</DD>
<DT>manualstart=</DT>
<DD>List of manually keyed connections to be automatically started at
 boot time. Useful for testing, but not for long term use. Connections
 which are automatically started should also be automatically re-keyed.</DD>
<DT>pluto=yes</DT>
<DD>Whether to start<A href="#Pluto"> Pluto</A> when ipsec startup is
 done.
<BR> This parameter is optional and defaults to &quot;yes&quot; if not present.
<P>&quot;yes&quot; is strongly recommended for production use so that the keying
 daemon (Pluto) will automatically re-key the connections regularly. The
 ipsec-auto parameters ikelifetime, ipseclifetime and reykeywindow give
 you control over frequency of rekeying.</P>
</DD>
<DT>plutoload=&quot;reno-van reno-adam reno-nyc&quot;</DT>
<DD>List of tunnels (by name, e.g. fred-susan or reno-van in our
 examples) to be loaded into Pluto's internal database at startup. In
 this example, Pluto loads three tunnels into its database when it is
 started.
<P>If plutoload is &quot;%search&quot;, Pluto will load any connections whose
 description includes &quot;auto=add&quot; or &quot;auto=start&quot;.</P>
</DD>
<DT>plutostart=&quot;reno-van reno-adam reno-nyc&quot;</DT>
<DD>List of tunnels to attempt to negotiate when Pluto is started.
<P>If plutostart is &quot;%search&quot;, Pluto will start any connections whose
 description includes &quot;auto=start&quot;.</P>
<P>Note that, for a connection intended to be permanent,<STRONG> both
 gateways should be set try to start</STRONG> the tunnel. This allows
 quick recovery if either gateway is rebooted or has its IPsec
 restarted. If only one gateway is set to start the tunnel and the other
 gateway restarts, the tunnel may not be rebuilt.</P>
</DD>
<DT>plutowait=no</DT>
<DD>Controls whether Pluto waits for one tunnel to be established before
 starting to negotiate the next. You might set this to &quot;yes&quot;
<UL>
<LI>if your gateway is a very limited machine and you need to conserve
 resources.</LI>
<LI>for debugging; the logs are clearer if only one connection is
 brought up at a time</LI>
</UL>
 For a busy and resource-laden production gateway, you likely want &quot;no&quot;
 so that connections are brought up in parallel and the whole process
 takes less time.</DD>
</DL>
<P>The example assumes you are at the Reno office and will use IPsec to
 Vancouver, New York City and Amsterdam.</P>
<H2><A name="multitunnel">Multiple tunnels between the same two gateways</A>
</H2>
<P>Consider a pair of subnets, each with a security gateway, connected
 via the Internet:</P>
<PRE>         192.168.100.0/24           left subnet
              |
         192.168.100.1
         North Gateway
         101.101.101.101            left
              |
         101.101.101.1              left next hop
         [Internet]
         202.202.202.1              right next hop
              |
         202.202.202.202            right
         South gateway
         192.168.200.1
              |
         192.168.200.0/24           right subnet</PRE>
<P>A tunnel specification such as:</P>
<PRE>conn northnet-southnet
      left=101.101.101.101
      leftnexthop=101.101.101.1
      leftsubnet=192.168.100.0/24
      leftfirewall=yes
      right=202.202.202.202
      rightnexthop=202.202.202.1
      rightsubnet=192.168.200.0/24
      rightfirewall=yes</PRE>
 will allow machines on the two subnets to talk to each other. You might
 test this by pinging from polarbear (192.168.100.7) to penguin
 (192.168.200.5).
<P>However,<STRONG> this does not cover other traffic you might want to
 secure</STRONG>. To handle all the possibilities, you might also want
 these connection descriptions:</P>
<PRE>conn northgate-southnet
      left=101.101.101.101
      leftnexthop=101.101.101.1
      right=202.202.202.202
      rightnexthop=202.202.202.1
      rightsubnet=192.168.200.0/24
      rightfirewall=yes

conn northnet-southgate
      left=101.101.101.101
      leftnexthop=101.101.101.1
      leftsubnet=192.168.100.0/24
      leftfirewall=yes
      right=202.202.202.202
      rightnexthop=202.202.202.1</PRE>
<P>Without these, neither gateway can do IPsec to the remote subnet.
 There is no IPsec tunnel or eroute set up for the traffic.</P>
<P>In our example, with the non-routable 192.168.* addresses used,
 packets would simply be discarded. In a different configuration, with
 routable addresses for the remote subnet,<STRONG> they would be sent
 unencrypted</STRONG> since there would be no IPsec eroute and there
 would be a normal IP route.</P>
<P>You might also want:</P>
<PRE>conn northgate-southgate
      left=101.101.101.101
      leftnexthop=101.101.101.1
      right=202.202.202.202
      rightnexthop=202.202.202.1</PRE>
<P>This is required if you want the two gateways to speak IPsec to each
 other.</P>
<P>This requires a lot of duplication of details. Judicious use of<VAR>
 also=</VAR> and<VAR> include</VAR> can reduce this problem.</P>
<P>Note that, while FreeS/WAN supports all four tunnel types, not all
 implementations do. In particular, some versions of Windows 2000 and
 the freely downloadable version of PGP provide only &quot;client&quot;
 functionality. You cannot use them as gateways with a subnet behind
 them. To get that functionality, you must upgrade to Windows 2000
 server or the commercially available PGP products.</P>
<H3><A name="advroute">One tunnel plus advanced routing</A></H3>
 It is also possible to use the new routing features in 2.2 and later
 kernels to avoid most needs for multple tunnels. Here is one mailing
 list message on the topic:
<PRE>Subject: Re: linux-ipsec: IPSec packets not entering tunnel?
   Date: Mon, 20 Nov 2000
   From: Justin Guyett &lt;jfg@sonicity.com&gt;

On Mon, 20 Nov 2000, Claudia Schmeing wrote:

&gt; Right                                                         Left
&gt;                      &quot;home&quot;                &quot;office&quot;
&gt; 10.92.10.0/24 ---- 24.93.85.110 ========= 216.175.164.91 ---- 10.91.10.24/24
&gt;
&gt; I've created all four tunnels, and can ping to test each of them,
&gt; *except* homegate-officenet.

I keep wondering why people create all four tunnels.  Why not route
traffic generated from home to 10.91.10.24/24 out ipsec0 with iproute2?
And 99% of the time you don't need to access &quot;office&quot; directly, which
means you can eliminate all but the subnet&lt;-&gt;subnet connection.</PRE>
 and FreeS/WAN technical lead Henry Spencer's comment:
<PRE>&gt; I keep wondering why people create all four tunnels.  Why not route
&gt; traffic generated from home to 10.91.10.24/24 out ipsec0 with iproute2?

This is feasible, given some iproute2 attention to source addresses, but
it isn't something we've documented yet... (partly because we're still
making some attempt to support 2.0.xx kernels, which can't do this, but
mostly because we haven't caught up with it yet).

&gt; And 99% of the time you don't need to access &quot;office&quot; directly, which
&gt; means you can eliminate all but the subnet&lt;-&gt;subnet connection.

Correct in principle, but people will keep trying to ping to or from the
gateways during testing, and sometimes they want to run services on the
gateway machines too.</PRE>

<!-- Is this in the right spot in this document? -->
<H2><A name="opp.gate">An Opportunistic Gateway</A></H2>
<H3><A NAME="14_7_1">Start from full opportunism</A></H3>
<P>Full opportunism allows you to initiate and receive opportunistic
 connections on your machine. The remaining instructions in this section
 assume you have first set up full opportunism on your gateway using<A HREF="#opp.incoming">
 these instructions</A>. Both sets of instructions require mailing DNS
 records to your ISP. Collect DNS records for both the gateway (above)
 and the subnet nodes (below) before contacting your ISP.</P>
<H3><A NAME="14_7_2">Reverse DNS TXT records for each protected machine</A>
</H3>
<P>You need these so that your Opportunistic peers can:</P>
<UL>
<LI>discover the gateway's address, knowing only the IP address that
 packets are bound for</LI>
<LI>verify that the gateway is authorised to encrypt for that endpoint</LI>
</UL>
<P>On the gateway, generate a TXT record with:</P>
<PRE>    ipsec showhostkey --txt 192.0.2.11</PRE>
<P>Use your gateway address in place of 192.0.2.11.</P>
<P>You should see (keys are trimmed for clarity throughout our example):</P>
<PRE>    ; RSA 2048 bits  gateway.example.com   Sat Apr 15 13:53:22 2000
    IN TXT  &quot;X-IPsec-Server(10)=192.0.2.11&quot; &quot; AQOF8tZ2...+buFuFn/&quot;</PRE>
<P><B>This MUST BE the same key as in your gateway's TXT record, or
 nothing will work.</B></P>
<P>In a text file, make one copy of this TXT record for each subnet
 node:</P>
<PRE>    ; RSA 2048 bits  gateway.example.com   Sat Apr 15 13:53:22 2000
    IN TXT  &quot;X-IPsec-Server(10)=192.0.2.11&quot; &quot; AQOF8tZ2...+buFuFn/&quot;
                                                                                
    ; RSA 2048 bits  gateway.example.com   Sat Apr 15 13:53:22 2000
    IN TXT  &quot;X-IPsec-Server(10)=192.0.2.11&quot; &quot; AQOF8tZ2...+buFuFn/&quot;
                                                                                
    ; RSA 2048 bits  gateway.example.com   Sat Apr 15 13:53:22 2000
    IN TXT  &quot;X-IPsec-Server(10)=192.0.2.11&quot; &quot; AQOF8tZ2...+buFuFn/&quot;</PRE>
<P>Above each entry, insert a line like this:</P>
<PRE>    98.2.0.192.in-addr.arpa. IN PTR arthur.example.com.</PRE>
<P>It must include:</P>
<UL>
<LI>The subnet node's address in reverse map format. For example,
 192.0.2.120 becomes<VAR> 120.2.0.192.in-addr.arpa.</VAR>. Note the
 final period.</LI>
<LI><VAR>IN PTR</VAR></LI>
<LI>The node's name, ie.<VAR> arthur.example.com.</VAR>. Note the final
 period.</LI>
</UL>
<P>The result will be a file of TXT records, like this:</P>
<PRE>    98.2.0.192.in-addr.arpa. IN PTR arthur.example.com.
    ; RSA 2048 bits  gateway.example.com   Sat Apr 15 13:53:22 2000
    IN TXT  &quot;X-IPsec-Server(10)=192.0.2.11&quot; &quot; AQOF8tZ2...+buFuFn/&quot;
                                                                                
    99.2.0.192.in-addr.arpa. IN PTR ford.example.com.
    ; RSA 2048 bits  gateway.example.com   Sat Apr 15 13:53:22 2000
    IN TXT  &quot;X-IPsec-Server(10)=192.0.2.11&quot; &quot; AQOF8tZ2...+buFuFn/&quot;
                                                                                
    100.2.0.192.in-addr.arpa. IN PTR trillian.example.com.
    ; RSA 2048 bits  gateway.example.com   Sat Apr 15 13:53:22 2000
    IN TXT  &quot;X-IPsec-Server(10)=192.0.2.11&quot; &quot; AQOF8tZ2...+buFuFn/&quot;</PRE>
<H3><A NAME="14_7_3">Publish your records</A></H3>
<P>Ask your ISP to publish all the reverse DNS records you have
 collected. There may be a delay of up to 48 hours as the records
 propagate.</P>
<H3><A NAME="14_7_4">...and test them</A></H3>
<P>Check a couple of records with commands like this one:</P>
<PRE>    ipsec verify --host ford.example.com
    ipsec verify --host trillian.example.com</PRE>
<P>The<VAR> verify</VAR> command checks for TXT records for both the
 subnet host and its gateway. You should see output like:</P>
<PRE>    ...
    Looking for TXT in reverse map: 99.2.0.192.in-addr.arpa [OK]
    ...
    Looking for TXT in reverse map: 11.2.0.192.in-addr.arpa   [OK]
    ...
    Looking for TXT in reverse map: 100.2.0.192.in-addr.arpa [OK]
    ...
    Looking for TXT in reverse map: 11.2.0.192.in-addr.arpa   [OK]
    ...</PRE>
<H3><A NAME="14_7_5">No Configuration Needed</A></H3>
<P>FreeS/WAN 2.x ships with a built-in, automatically enabled OE
 connection<VAR> conn packetdefault</VAR> which applies OE, if possible,
 to all outbound traffic routed through the FreeS/WAN box. The<A HREF="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5) manual</A> describes this connection in detail. While the
 effect is much the same as<VAR> private-or-clear</VAR>, the
 implementation is different: notably, it does not use policy groups.</P>
<P>You can create more complex OE configurations for traffic forwarded
 through a FreeS/WAN box, as explained in our<A HREF="#policygroups">
 policy groups document</A>, or disable OE using<A HREF="#disable_policygroups">
 these instructions</A>.</P>
<H2><A name="extruded.config">Extruded Subnets</A></H2>
<P>What we call<A href="glossary.html#extruded"> extruded subnets</A>
 are a special case of<A href="glossary.html#VPN.gloss"> VPNs</A>.</P>
<P>If your buddy has some unused IP addresses, in his subnet far off at
 the other side of the Internet, he can loan them to you... provided
 that the connection between you and him is fast enough to carry all the
 traffic between your machines and the rest of the Internet. In effect,
 he &quot;extrudes&quot; a part of his address space over the network to you, with
 your Internet traffic appearing to originate from behind his Internet
 gateway.</P>
<P>As far as the Internet is concerned, your new extruded net is behind
 your buddy's gateway. You route all your packets for the Internet at
 large out his gateway, and receive return packets the same way. You
 route your local packets locally.</P>
<P>Suppose your friend has a.b.c.0/24 and wants to give you
 a.b.c.240/28. The initial situation is:</P>
<PRE>    subnet           gateway          Internet
  a.b.c.0/24    a.b.c.1    p.q.r.s</PRE>
 where anything from the Internet destined for any machine in a.b.c.0/24
 is routed via p.q.r.s and that gateway knows what to do from there.
<P>Of course it is quite normal for various smaller subnets to exist
 behind your friend's gateway. For example, your friend's company might
 have a.b.c.16/28=development, a.b.c.32/28=marketing and so on. The
 Internet neither knows not cares about this; it just delivers packets
 to the p.q.r.s and lets the gateway do whatever needs to be done from
 there.</P>
<P>What we want to do is take a subnet, perhaps a.b.c.240/28, out of
 your friend's physical location<EM> while still having your friend's
 gateway route to it</EM>. As far as the Internet is concerned, you
 remain behind that gateway.</P>
<PRE>    subnet           gateway          Internet       your gate  extruded

  a.b.c.0/24   a.b.c.1     p.q.r.s              d.e.f.g         a.b.c.240/28                

                           ========== tunnel ==========</PRE>
<P>The extruded addresses have to be a complete subnet.</P>
<P>In our example, the friend's security gateway is also his Internet
 gateway, but this is not necessary. As long as all traffic from the
 Internet to his addresses passes through the Internet gate, the
 security gate could be a machine behind that. The IG would need to
 route all traffic for the extruded subnet to the SG, and the SG could
 handle the rest.</P>
<P>First, configure your subnet using the extruded addresses. Your
 security gateway's interface to your subnet needs to have an extruded
 address (possibly using a Linux<A href="#virtual"> virtual interface</A>
, if it also has to have a different address). Your gateway needs to
 have a route to the extruded subnet, pointing to that interface. The
 other machines at your site need to have addresses in that subnet, and
 default routes pointing to your gateway.</P>
<P>If any of your friend's machines need to talk to the extruded subnet,<EM>
 they</EM> need to have a route for the extruded subnet, pointing at his
 gateway.</P>
<P>Then set up an IPsec subnet-to-subnet tunnel between your gateway and
 his, with your subnet specified as the extruded subnet, and his subnet
 specified as &quot;0.0.0.0/0&quot;.</P>
<P>The tunnel description should be:</P>
<PRE>conn extruded
        left=p.q.r.s
        leftsubnet=0.0.0.0/0
        right=d.e.f.g
        rightsubnet=a.b.c.0/28</PRE>
<P>If either side was doing firewalling for the extruded subnet before
 the IPsec connection is set up, you'll need to poke holes in your<A HREF="#firewall">
 firewall</A> to allow packets through.</P>
<P>And it all just works. Your SG routes traffic for 0.0.0.0/0 -- that
 is, the whole Internet -- through the tunnel to his SG, which then
 sends it onward as if it came from his subnet. When traffic for the
 extruded subnet arrives at his SG, it gets sent through the tunnel to
 your SG, which passes it to the right machine.</P>
<P>Remember that when ipsec_manual or ipsec_auto takes a connection
 down, it<EM> does not undo the route</EM> it made for that connection.
 This lets you take a connection down and bring up a new one, or a
 modified version of the old one, without having to rebuild the route it
 uses and without any risk of packets which should use IPsec
 accidentally going out in the clear. Because the route always points
 into KLIPS, the packets will always go there. Because KLIPS temporarily
 has no idea what to do with them (no eroute for them), they will be
 discarded.</P>
<P>If you<EM> do</EM> want to take the route down, this is what the
 &quot;unroute&quot; operation in manual and auto is for. Just do an unroute after
 doing the down.</P>
<P>Note that the route for a connection may have replaced an existing
 non-IPsec route. Nothing in Linux FreeS/WAN will put that pre-IPsec
 route back. If you need it back, you have to create it with the route
 command.</P>
<H2><A name="roadvirt">Road Warrior with virtual IP address</A></H2>
<P>Please note that<A HREF="http://www.freeswan.ca/download.php"> Super
 FreeS/WAN</A> now features DHCP-over-IPsec, which is an alternate
 procedure for Virtual IP address assignment.</P>
<P></P>
<P>Here is a mailing list message about another way to configure for
 road warrior support:</P>
<PRE>Subject: Re: linux-ipsec: understanding the vpn
   Date: Thu, 28 Oct 1999 10:43:22 -0400
   From: Irving Reid &lt;irving@nevex.com&gt;

&gt;  local-------linux------internet------mobile
&gt;  LAN        box                         user
&gt;  ...

&gt;  now when the mobile user connects to the linux box
&gt;  it is given a virtual IP address, i have configured it to
&gt;  be in the 10.x.x.x range. mobile user and linux box 
&gt;  have a tunnel between them with these IP addresses.

&gt;   Uptil this all is fine.

If it is possible to configure your mobile client software *not* to
use a virtual IP address, that will make your life easier. It is easier
to configure FreeS/WAN to use the actual address the mobile user gets
from its ISP.

Unfortunately, some Windows clients don't let you choose.

&gt;  what i would like to know is that how does the mobile
&gt;  user communicate with other computers on the local
&gt;  LAN , of course with the vpn ?

&gt;   what IP address should the local LAN 
&gt;  computers have ? I guess their default gateway 
&gt;  should be the linux box ? and does the linux box need
&gt;  to be a 2 NIC card box or one is fine.

As someone else stated, yes, the Linux box would usually be the default
IP gateway for the local lan.

However...

If you mobile user has software that *must* use a virtual IP address,
the whole picture changes. Nobody has put much effort into getting
FreeS/WAN to play well in this environment, but here's a sketch of one
approach:

Local Lan 1.0.0.0/24
    |
    +- Linux FreeS/WAN 1.0.0.2
    |
    | 1.0.0.1
 Router
    | 2.0.0.1
    |
Internet
    |
    | 3.0.0.1
Mobile User
      Virtual Address: 1.0.0.3

Note that the Local Lan network (1.0.0.x) can be registered, routable
addresses.

Now, the Mobile User sets up an IPSec security association with the
Linux box (1.0.0.2); it should ESP encapsulate all traffic to the
network 1.0.0.x **EXCEPT** UDP port 500. 500/udp is required for the key
negotiation, which needs to work outside of the IPSec tunnel.

On the Linux side, there's a bunch of stuff you need to do by hand (for
now). FreeS/WAN should correctly handle setting up the IPSec SA and
routes, but I haven't tested it so this may not work...

The FreeS/WAN conn should look like:

conn mobile
        right=1.0.0.2
        rightsubnet=1.0.0.0/24
        rightnexthop=1.0.0.1
        left=0.0.0.0  # The infamous &quot;road warrior&quot;
        leftsubnet=1.0.0.3/32

Note that the left subnet contains *only* the remote host's virtual
address.

Hopefully the routing table on the FreeS/WAN box ends up looking like
this:

% netstat -rn
Kernel IP routing table
Destination     Gateway      Genmask         Flags   MSS Window  irtt Iface
1.0.0.0         0.0.0.0      255.255.255.0   U      1500 0          0 eth0
127.0.0.0       0.0.0.0      255.0.0.0       U      3584 0          0 lo
0.0.0.0         1.0.0.1      0.0.0.0         UG     1500 0          0 eth0
1.0.0.3         1.0.0.1      255.255.255.255 UG     1433 0          0 ipsec0

So, if anybody sends a packet for 1.0.0.3 to the Linux box, it should
get bundled up and sent through the tunnel. To get the packets for
1.0.0.3 to the Linux box in the first place, you need to use &quot;proxy
ARP&quot;.

How this works is: when a host or router on the local Ethernet segment
wants to send a packet to 1.0.0.3, it sends out an Ethernet level
broadcast &quot;ARP request&quot;. If 1.0.0.3 was on the local LAN, it would
reply, saying &quot;send IP packets for 1.0.0.3 to my Ethernet address&quot;.

Instead, you need to set up the Linux box so that _it_ answers ARP
requests for 1.0.0.3, even though that isn't its IP address. That
convinces everyone else on the lan to send 1.0.0.3 packets to the Linux
box, where the usual FreeS/WAN processing and routing take over.

% arp -i eth0 -s 1.0.0.3 -D eth0 pub

This says, if you see an ARP request on interface eth0 asking for
1.0.0.3, respond with the Ethernet address of interface eth0.

Now, as I said at the very beginning, if it is *at all* possible to
configure your client *not* to use the virtual IP address, you can avoid
this whole mess.</PRE>
<H2><A name="dynamic">Dynamic Network Interfaces</A></H2>
<P>Sometimes you have to cope with a situation where the network
 interface(s) aren't all there at boot. The common example is notebooks
 with PCMCIA.</P>
<H3><A name="basicdyn">Basics</A></H3>
<P>The key issue here is that the<VAR> config setup</VAR> section of the<VAR>
 /etc/ipsec.conf</VAR> configuration file lists the connection between
 ipsecN and hardware interfaces, in the<VAR> interfaces=</VAR> variable.
 At any time when<VAR> ipsec setup start</VAR> or<VAR> ipsec setup
 restart</VAR> is run this variable<STRONG> must</STRONG> correspond to
 the current real situation. More precisely, it<STRONG> must not</STRONG>
 mention any hardware interfaces which don't currently exist. The
 difficulty is that an<VAR> ipsec setup start</VAR> command is normally
 run at boot time so interfaces that are not up then are mis-handled.</P>
<H3><A name="bootdyn">Boot Time</A></H3>
<P>Normally, an<VAR> ipsec setup start</VAR> is run at boot time.
 However, if the hardware situation at boot time is uncertain, one of
 two things must be done.</P>
<UL>
<LI>One possibility is simply not to have IPsec brought up at boot time.
 To do this:
<PRE>        chkconfig --level 2345 ipsec off</PRE>
 That's for modern Red Hats or other Linuxes with chkconfig. Systems
 which lack this will require fiddling with symlinks in /etc/rc.d/rc?.d
 or the equivalent.</LI>
<LI>Another possibility is to bring IPsec up with no interfaces, which
 is less aesthetically satisfying but simpler. Just put
<PRE>        interfaces=</PRE>
 in the configuration file. KLIPS and Pluto will be started, but won't
 do anything.</LI>
</UL>
<H3><A name="changedyn">Change Time</A></H3>
<P>When the hardware *is* in place, IPsec has to be made aware of it.
 Someday there may be a nice way to do this.</P>
<P>Right now, the way to do it is to fix the<VAR> /etc/ipsec.conf</VAR>
 file appropriately, so<VAR> interfaces</VAR> reflects the new
 situation, and then restart the IPsec subsystem. This does break any
 existing IPsec connections.</P>
<P>If IPsec wasn't brought up at boot time, do</P>
<PRE>        ipsec setup start</PRE>
 while if it was, do
<PRE>        ipsec setup restart</PRE>
 which won't be as quick.
<P>If some of the hardware is to be taken out, before doing that, amend
 the configuration file so interfaces no longer includes it, and do</P>
<PRE>        ipsec setup restart</PRE>
<P>Again, this breaks any existing connections.</P>
<H2><A name="unencrypted">Unencrypted tunnels</A></H2>
<P>Sometimes you might want to create a tunnel without encryption. Often
 this is a bad idea, even if you have some data which need not be
 private. See this<A href="#traffic.resist"> discussion</A>.</P>
<P>The IPsec protocols provide two ways to do build such tunnels:</P>
<DL>
<DT>using ESP with null encryption</DT>
<DD>not supported by FreeS/WAN</DD>
<DT>using<A href="#AH"> AH</A> without<A href="#ESP"> ESP</A></DT>
<DD>supported for manually keyed connections</DD>
<DD>possible with explicit commands via<A href="manpage.d/ipsec_whack.8.html">
 ipsec_whack(8)</A> (see this<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/02/msg00190.html">
 list message</A>)</DD>
<DD>not supported in the<A href="manpage.d/ipsec_auto.8.html">
 ipsec_auto(8)</A> scripts.</DD>
</DL>
 One situation in which this comes up is when otherwise some data would
 be encrypted twice. Alice wants a secure tunnel from her machine to
 Bob's. Since she's behind one security gateway and he's behind another,
 part of the tunnel that they build passes through the tunnel that their
 site admins have built between the gateways. All of Alice and Bob's
 messages are encrypted twice.
<P>There are several ways to handle this.</P>
<UL>
<LI>Just accept the overhead of double encryption. The site admins might
 choose this if any of the following apply:
<UL>
<LI>policy says encrypt everything (usually, it should)</LI>
<LI>they don't entirely trust Alice and Bob (usually, if they don't have
 to, they shouldn't)</LI>
<LI>if they don't feel the saved cycles are worth the time they'd need
 to build a non-encrypted tunnel for Alice and Bob's packets (often,
 they aren't)</LI>
</UL>
</LI>
<LI>Use a plain IP-in-IP tunnel. These are not well documented. A good
 starting point is in the Linux kernel source tree, in
 /usr/src/linux/drivers/net/README.tunnel.</LI>
<LI>Use a manually-keyed AH-only tunnel.</LI>
</UL>
<P>Note that if Alice and Bob want end-to-end security, they must build
 a tunnel end-to-end between their machines or use some other end-to-end
 tool such as PGP or SSL that suits their data. The only question is
 whether the admins build some special unencrypted tunnel for those
 already-encrypted packets.</P>
<HR>
<H1><A name="install">Installing FreeS/WAN</A></H1>
<P>This document will teach you how to install Linux FreeS/WAN. If your
 distribution comes with Linux FreeS/WAN, we offer tips to get you
 started.</P>
<H2><A NAME="15_1">Requirements</A></H2>
<P>To install FreeS/WAN you must:</P>
<UL>
<LI>be running Linux with the 2.4 or 2.2 kernel series. See this<A HREF="http://www.freeswan.ca/download.php#contact">
 kernel compatibility table</A>.
<BR>We also have experimental support for 2.6 kernels. Here are two
 basic approaches:
<UL>
<LI> install FreeS/WAN, including its<A HREF="#parts"> KLIPS</A> kernel
 code. This will remove the native IPsec stack and replace it with
 KLIPS.</LI>
<LI> install the FreeS/WAN<A HREF="#parts"> userland tools</A> (keying
 daemon and supporting scripts) for use with<A HREF="http://lartc.org/howto/lartc.ipsec.html">
 2.6 kernel native IPsec</A>,</LI>
</UL>
 See also these<A HREF="2.6.known-issues"> known issues with 2.6</A>.</LI>
<LI>have root access to your Linux box</LI>
<LI>choose the version of FreeS/WAN you wish to install based on<A HREF="http://www.freeswan.org/mail.html">
 mailing list reports</A>
<!-- or 
our updates page (coming soon)-->
</LI>
</UL>
<H2><A NAME="15_2">Choose your install method</A></H2>
<P>There are three basic ways to get FreeS/WAN onto your system:</P>
<UL>
<LI>activating and testing a FreeS/WAN that<A HREF="#distroinstall">
 shipped with your Linux distribution</A></LI>
<LI><A HREF="#rpminstall">RPM install</A></LI>
<LI><A HREF="#srcinstall">Install from source</A></LI>
</UL>
<A NAME="distroinstall"></A>
<H2><A NAME="15_3">FreeS/WAN ships with some Linuxes</A></H2>
<P>FreeS/WAN comes with<A HREF="#distwith"> these distributions</A>.</P>
<P>If you're running one of these, include FreeS/WAN in the choices you
 make during installation, or add it later using the distribution's
 tools.</P>
<H3><A NAME="15_3_1">FreeS/WAN may be altered...</A></H3>
<P>Your distribution may have integrated extra features, such as Andreas
 Steffen's X.509 patch, into FreeS/WAN. It may also use custom startup
 script locations or directory names.</P>
<H3><A NAME="15_3_2">You might need to create an authentication keypair</A>
</H3>
<P>If your FreeS/WAN came with your distribution, you may wish to
 generate a fresh RSA key pair. FreeS/WAN will use these keys for
 authentication.</P>
<P> To do this, become root, and type:</P>
<PRE>    ipsec newhostkey --output /etc/ipsec.secrets --hostname xy.example.com
    chmod 600 /etc/ipsec.secrets</PRE>
<P>where you replace xy.example.com with your machine's fully-qualified
 domain name. Generate some randomness, for example by wiggling your
 mouse, to speed the process.</P>
<P>The resulting ipsec.secrets looks like:</P>
<PRE>: RSA   {
        # RSA 2192 bits   xy.example.com   Sun Jun 8 13:42:19 2003
        # for signatures only, UNSAFE FOR ENCRYPTION
        #pubkey=0sAQOFppfeE3cC7wqJi...
        Modulus: 0x85a697de137702ef0...
        # everything after this point is secret
        PrivateExponent: 0x16466ea5033e807...
        Prime1: 0xdfb5003c8947b7cc88759065...
        Prime2: 0x98f199b9149fde11ec956c814...
        Exponent1: 0x9523557db0da7a885af90aee...
        Exponent2: 0x65f6667b63153eb69db8f300dbb...
        Coefficient: 0x90ad00415d3ca17bebff123413fc518...
        }
# do not change the indenting of that &quot;}&quot;</PRE>
<P>In the actual file, the strings are much longer.</P>
<H3><A NAME="15_3_3">Start and test FreeS/WAN</A></H3>
<P>You can now<A HREF="#starttest"> start FreeS/WAN and test whether
 it's been successfully installed.</A>.</P>
<A NAME="rpminstall"></A>
<H2><A NAME="15_4">RPM install</A></H2>
<P>These instructions are for a recent Red Hat with a stock Red Hat
 kernel. We know that Mandrake and SUSE also produce FreeS/WAN RPMs. If
 you're running either, install using your distribution's tools.</P>
<H3><A NAME="15_4_1">Download RPMs</A></H3>
<P>Decide which functionality you need:</P>
<UL>
<LI>standard FreeS/WAN RPMs. Use these shortcuts:
<BR>
<UL>
<LI>(for 2.6 kernels: userland only)
<BR> ncftpget
 ftp://ftp.xs4all.nl/pub/crypto/freeswan/binaries/RedHat-RPMs/\*userland*
</LI>
<LI>(for 2.4 kernels)
<BR> ncftpget
 ftp://ftp.xs4all.nl/pub/crypto/freeswan/binaries/RedHat-RPMs/`uname -r
 | tr -d 'a-wy-z'`/\*</LI>
<LI> or view all the offerings at our<A href="ftp://ftp.xs4all.nl/pub/crypto/freeswan/binaries/RedHat-RPMs">
 FTP site</A>.</LI>
</UL>
</LI>
<LI>unofficial<A href="http://www.freeswan.ca/download.php"> Super
 FreeS/WAN</A> RPMs, which include Andreas Steffen's X.509 patch and
 more. Super FreeS/WAN RPMs do not currently include<A HREF="#NAT.gloss">
 Network Address Translation</A> (NAT) traversal, but Super FreeS/WAN
 source does.</LI>
</UL>
<A NAME="2.6.rpm"></A>
<P>For 2.6 kernels, get the latest FreeS/WAN userland RPM, for example:</P>
<PRE>    freeswan-userland-2.04.9-0.i386.rpm</PRE>
<P>Note: FreeS/WAN's support for 2.6 kernel IPsec is preliminary. Please
 see<A HREf="2.6.known-issues"> 2.6.known-issues</A>, and the latest<A HREF="http://www.freeswan.org/mail.html">
 mailing list reports</A>.</P>
<P>Change to your new FreeS/WAN directory, and make and install the</P>
<P>For 2.4 kernels, get both kernel and userland RPMs. Check your kernel
 version with</P>
<PRE>    uname -r</PRE>
<P>Get a kernel module which matches that version. For example:</P>
<PRE>    freeswan-module-2.04_2.4.20_20.9-0.i386.rpm</PRE>
<P>Note: These modules<B> will only work on the Red Hat kernel they were
 built for</B>, since they are very sensitive to small changes in the
 kernel.</P>
<P>Get FreeS/WAN utilities to match. For example:</P>
<PRE>    freeswan-userland-2.04_2.4.20_20.9-0.i386.rpm</PRE>
<H3><A NAME="15_4_2">For freeswan.org RPMs: check signatures</A></H3>
<P>While you're at our ftp site, grab the RPM signing key</P>
<PRE>    freeswan-rpmsign.asc</PRE>
<P>If you're running RedHat 8.x or later, import this key into the RPM
 database:</P>
<PRE>    rpm --import freeswan-rpmsign.asc</PRE>
<P>For RedHat 7.x systems, you'll need to add it to your<A HREF="#PGP">
 PGP</A> keyring:</P>
<PRE>    pgp -ka freeswan-rpmsign.asc</PRE>
<P>Check the digital signatures on both RPMs using:</P>
<PRE>    rpm --checksig freeswan*.rpm </PRE>
<P>You should see that these signatures are good:</P>
<PRE>    freeswan-module-2.04_2.4.20_20.9-0.i386.rpm: pgp md5 OK
    freeswan-userland-2.04_2.4.20_20.9-0.i386.rpm: pgp md5 OK</PRE>
<H3><A NAME="15_4_3">Install the RPMs</A></H3>
<P>Become root:</P>
<PRE>    su</PRE>
<P>For a first time install, use:</P>
<PRE>    rpm -ivh freeswan*.rpm</PRE>
<P>To upgrade existing RPMs (and keep all .conf files in place), use:</P>
<PRE>    rpm -Uvh freeswan*.rpm</PRE>
<P>If you're upgrading from FreeS/WAN 1.x to 2.x RPMs, and encounter
 problems, see<A HREF="#upgrading.rpms"> this note</A>.</P>
<H3><A NAME="15_4_4">Start and Test FreeS/WAN</A></H3>
<P>Now,<A HREF="#starttest"> start FreeS/WAN and test your install</A>.</P>
<A NAME="srcinstall"></A>
<H2><A NAME="15_5">Install from Source</A></H2>

<!-- Most of this section, along with "Start and Test", can replace 
INSTALL. -->
<H3><A NAME="15_5_1">Decide what functionality you need</A></H3>
<P>Your choices are:</P>
<UL>
<LI><A HREF="ftp://ftp.xs4all.nl/pub/crypto/freeswan">standard FreeS/WAN</A>
,</LI>
<LI>standard FreeS/WAN plus any of these<A HREF="#patch"> user-supported
 patches</A>, or</LI>
<LI><A HREF="http://www.freeswan.ca/download">Super FreeS/WAN</A>, an
 unofficial FreeS/WAN pre-patched with many of the above. Provides
 additional algorithms, X.509, SA deletion, dead peer detection, and<A HREF="#NAT.gloss">
 Network Address Translation</A> (NAT) traversal.</LI>
</UL>
<H3><A NAME="15_5_2">Download FreeS/WAN</A></H3>
<P>Download the source tarball you've chosen, along with any patches.</P>
<H3><A NAME="15_5_3">For freeswan.org source: check its signature</A></H3>
<P>While you're at our ftp site, get our source signing key</P>
<PRE>    freeswan-sigkey.asc</PRE>
<P>Add it to your PGP keyring:</P>
<PRE>    pgp -ka freeswan-sigkey.asc</PRE>
<P>Check the signature using:</P>
<PRE>    pgp freeswan-2.04.tar.gz.sig freeswan-2.04.tar.gz</PRE>
<P>You should see something like:</P>
<PRE>    Good signature from user &quot;Linux FreeS/WAN Software Team (build@freeswan.org)&quot;.
    Signature made 2002/06/26 21:04 GMT using 2047-bit key, key ID 46EAFCE1</PRE>

<!-- Note to self: build@freeswan.org has angled brackets in the original.
     Changed because it conflicts with HTML tags. -->
<H3><A NAME="15_5_4">Untar, unzip</A></H3>
<P>As root, unpack your FreeS/WAN source into<VAR> /usr/src</VAR>.</P>
<PRE>    su
    mv freeswan-2.04.tar.gz /usr/src
    cd /usr/src
    tar -xzf freeswan-2.04.tar.gz
</PRE>
<H3><A NAME="15_5_5">Patch if desired</A></H3>
<P>Now's the time to add any patches. The contributor may have special
 instructions, or you may simply use the patch command.</P>
<H3><A NAME="15_5_6">... and Make</A></H3>
<P>Choose one of the methods below.</P>
<H4><A NAME="15_5_6_1">Userland-only Install for 2.6 kernels</A></H4>
<A NAME="2.6.src"></A>
<P>Note: FreeS/WAN's support for 2.6 kernel IPsec is preliminary. Please
 see<A HREf="2.6.known-issues"> 2.6.known-issues</A>, and the latest<A HREF="http://www.freeswan.org/mail.html">
 mailing list reports</A>.</P>
<P>Change to your new FreeS/WAN directory, and make and install the
 FreeS/WAN userland tools.</P>
<PRE>    cd /usr/src/freeswan-2.04
    make programs
    make install</PRE>
<P>Now,<A HREF="#starttest"> start FreeS/WAN and test your install</A>.</P>
<H4><A NAME="15_5_6_2">KLIPS install for 2.2, 2.4, or 2.6 kernels</A></H4>
<A NAME="modinstall"></A>
<P>To make a modular version of KLIPS, along with other FreeS/WAN
 programs you'll need, use the command sequence below. This will change
 to your new FreeS/WAN directory, make the FreeS/WAN module (and other
 stuff), and install it all.</P>
<PRE>    cd /usr/src/freeswan-2.04
    make oldmod
    make minstall</PRE>
<P><A HREF="#starttest">Start FreeS/WAN and test your install</A>.</P>
<P>To link KLIPS statically into your kernel (using your old kernel
 settings), and install other FreeS/WAN components, do:</P>
<PRE>    cd /usr/src/freeswan-2.04
    make oldmod
    make minstall</PRE>
<P>Reboot your system and<A HREF="#testonly"> test your install</A>.</P>
<P>For other ways to compile KLIPS, see our Makefile.</P>
<A name="starttest"></A>
<H2><A NAME="15_6">Start FreeS/WAN and test your install</A></H2>
<P>Bring FreeS/WAN up with:</P>
<PRE>    service ipsec start</PRE>
<P>This is not necessary if you've rebooted.</P>
<A name="testonly"></A>
<H2><A NAME="15_7">Test your install</A></H2>
<P>To check that you have a successful install, run:</P>
<PRE>    ipsec verify</PRE>
<P>You should see at least:</P>
<PRE>
    Checking your system to see if IPsec got installed and started correctly
    Version check and ipsec on-path                             [OK]
    Checking for KLIPS support in kernel                        [OK]
    Checking for RSA private key (/etc/ipsec.secrets)           [OK]
    Checking that pluto is running                              [OK]
</PRE>
<P>If any of these first four checks fails, see our<A href="#install.check">
 troubleshooting guide</A>.</P>
<H2><A NAME="15_8">Making FreeS/WAN play well with others</A></H2>
<P>There are at least a couple of things on your system that might
 interfere with FreeS/WAN, and now's a good time to check these:</P>
<UL>
<LI>Firewalling. You need to allow UDP 500 through your firewall, plus
 ESP (protocol 50) and AH (protocol 51). For more information, see our
 updated firewalls document (coming soon).</LI>
<LI>Network address translation. Do not NAT the packets you will be
 tunneling.</LI>
</UL>
<H2><A NAME="15_9">Configure for your needs</A></H2>
<P>You'll need to configure FreeS/WAN for your local site. Have a look
 at our<A HREF="quickstart.html"> opportunism quickstart guide</A> to
 see if that easy method is right for your needs. Or, see how to<A HREF="config.html">
 configure a network-to-network or Road Warrior style VPN</A>.</P>
<HR>
<H1><A NAME="config">How to configure FreeS/WAN</A></H1>
<P>This page will teach you how to configure a simple network-to-network
 link or a Road Warrior connection between two Linux FreeS/WAN boxes.</P>
<P>See also these related documents:</P>
<UL>
<LI>our<A HREF="#quickstart"> quickstart</A> guide to<A HREF="#carpediem">
 opportunistic encryption</A></LI>
<LI>our guide to configuration with<A HREF="#policygroups"> policy
 groups</A></LI>
<LI>our<A HREF="#adv_config"> advanced configuration</A> document</LI>
</UL>
<P> The network-to-network setup allows you to connect two office
 networks into one Virtual Private Network, while the Road Warrior
 connection secures a laptop's telecommute to work. Our examples also
 show the basic procedure on the Linux FreeS/WAN side where another
 IPsec peer is in play.</P>
<P> Shortcut to<A HREF="#config.netnet"> net-to-net</A>.
<BR> Shortcut to<A HREF="#config.rw"> Road Warrior</A>.</P>
<H2><A NAME="16_1">Requirements</A></H2>
<P>To configure the network-to-network connection you must have:</P>
<UL>
<LI>two Linux gateways with static IPs</LI>
<LI>a network behind each gate. Networks must have non-overlapping IP
 ranges.</LI>
<LI>Linux FreeS/WAN<A HREF="#install"> installed</A> on both gateways</LI>
<LI><A HREF="http://www.tcpdump.org"><VAR>tcpdump</VAR></A> on the local
 gate, to test the connection</LI>
</UL>
<P>For the Road Warrior you need:</P>
<UL>
<LI>one Linux box with a static IP</LI>
<LI>a Linux laptop with a dynamic IP</LI>
<LI>Linux FreeS/WAN installed on both</LI>
<LI>for testing,<VAR> tcpdump</VAR> on your gateway or laptop</LI>
</UL>
<P>If both IPs are dynamic, your situation is a bit trickier. Your best
 bet is a variation on the<A HREF="#config.rw"> Road Warrior</A>, as
 described in<A HREF="http://lists.freeswan.org/archives/users/2003-October/msg00282.html">
 this mailing list message</A>.</P>
<H2><A name="config.netnet"></A>Net-to-Net connection</H2>
<H3><A name="netnet.info.ex">Gather information</A></H3>
<P>For each gateway, compile the following information:</P>
<UL>
<LI>gateway IP</LI>
<LI>IP range of the subnet you will be protecting. This doesn't have to
 be your whole physical subnet.</LI>
<LI>a name by which that gateway can identify itself for IPsec
 negotiations. Its form is a Fully Qualified Domain Name preceded by an
 @ sign, ie. @xy.example.com.
<BR> It does not need to be within a domain that you own. It can be a
 made-up name.</LI>
</UL>
<H4><A NAME="16_2_1_1">Get your leftrsasigkey</A></H4>
<P>On your local Linux FreeS/WAN gateway, print your IPsec public key:</P>
<PRE>    ipsec showhostkey --left</PRE>
<P>The output should look like this (with the key shortened for easy
 reading):</P>
<PRE>    # RSA 2048 bits   xy.example.com   Fri Apr 26 15:01:41 2002
    leftrsasigkey=0sAQOnwiBPt...</PRE>
<P>Don't have a key? Use<A HREF="manpage.d/ipsec_newhostkey.8.html"><VAR>
 ipsec newhostkey</VAR></A> to create one.</P>
<H4><A NAME="16_2_1_2">...and your rightrsasigkey</A></H4>
<P>Get a console on the remote side:</P>
<PRE>    ssh2 ab.example.com</PRE>
<P>In that window, type:</P>
<PRE>    ipsec showhostkey --right</PRE>
<P>You'll see something like:</P>
<PRE>    # RSA 2192 bits   ab.example.com   Thu May 16 15:26:20 2002
    rightrsasigkey=0sAQOqH55O...</PRE>
<H3><A NAME="16_2_2">Edit<VAR> /etc/ipsec.conf</VAR></A></H3>
<P>Back on the local gate, copy our template to<VAR> /etc/ipsec.conf</VAR>
. (on Mandrake,<VAR> /etc/freeswan/ipsec.conf</VAR>). Substitute the
 information you've gathered for our example data.</P>
<PRE>conn net-to-net
    left=192.0.2.2                 # Local vitals
    leftsubnet=192.0.2.128/29      # 
    leftid=@xy.example.com         #   
    leftrsasigkey=0s1LgR7/oUM...   #
    leftnexthop=%defaultroute      # correct in many situations 
    right=192.0.2.9                # Remote vitals
    rightsubnet=10.0.0.0/24        #
    rightid=@ab.example.com        # 
    rightrsasigkey=0sAQOqH55O...   #
    rightnexthop=%defaultroute     # correct in many situations
    auto=add                       # authorizes but doesn't start this 
                                   # connection at startup</PRE>
<P> &quot;Left&quot; and &quot;right&quot; should represent the machines that have FreeS/WAN
 installed on them, and &quot;leftsubnet&quot; and &quot;rightsubnet&quot; machines that are
 being protected. /32 is assumed for left/right and left/rightsubnet
 parameters.</P>
<P>Copy<VAR> conn net-to-net</VAR> to the remote-side /etc/ipsec.conf.
 If you've made no other modifications to either<VAR> ipsec.conf</VAR>,
 simply:</P>
<PRE>    scp2 ipsec.conf root@ab.example.com:/etc/ipsec.conf</PRE>
<H3><A NAME="16_2_3">Start your connection</A></H3>
<P>Locally, type:</P>
<PRE>    ipsec auto --up net-to-net</PRE>
<P>You should see:</P>
<PRE>    104 &quot;net-net&quot; #223: STATE_MAIN_I1: initiate
    106 &quot;net-net&quot; #223: STATE_MAIN_I2: sent MI2, expecting MR2
    108 &quot;net-net&quot; #223: STATE_MAIN_I3: sent MI3, expecting MR3
    004 &quot;net-net&quot; #223: STATE_MAIN_I4: ISAKMP SA established
    112 &quot;net-net&quot; #224: STATE_QUICK_I1: initiate
    004 &quot;net-net&quot; #224: STATE_QUICK_I2: sent QI2, IPsec SA established</PRE>
<P>The important thing is<VAR> IPsec SA established</VAR>. If you're
 unsuccessful, see our<A HREF="#trouble"> troubleshooting tips</A>.</P>
<H3><A NAME="16_2_4">Do not MASQ or NAT packets to be tunneled</A></H3>
<P>If you are using<A HREF="#masq"> IP masquerade</A> or<A HREF="#NAT.gloss">
 Network Address Translation (NAT)</A> on either gateway, you must now
 exempt the packets you wish to tunnel from this treatment. For example,
 if you have a rule like:</P>
<PRE>iptables -t nat -A POSTROUTING -o eth0 -s 10.0.0.0/24 -j MASQUERADE
</PRE>
<P>change it to something like:</P>
<PRE>iptables -t nat -A POSTROUTING -o eth0 -s 10.0.0.0/24 -d \! 192.0.2.128/29 -j MASQUERADE</PRE>
<P>This may be necessary on both gateways.</P>
<H3><A NAME="16_2_5">Test your connection</A></H3>
<P>Sit at one of your local subnet nodes (not the gateway), and ping a
 subnet node on the other (again, not the gateway).</P>
<PRE>    ping fileserver.toledo.example.com</PRE>
<P>While still pinging, go to the local gateway and snoop your outgoing
 interface, for example:</P>
<PRE>    tcpdump -i ppp0</PRE>
<P>You want to see ESP (Encapsulating Security Payload) packets moving<B>
 back and forth</B> between the two gateways at the same frequency as
 your pings:</P>
<PRE>    19:16:32.046220 192.0.2.2 &gt; 192.0.2.9: ESP(spi=0x3be6c4dc,seq=0x3)
    19:16:32.085630 192.0.2.9 &gt; 192.0.2.2: ESP(spi=0x5fdd1cf8,seq=0x6)</PRE>
<P>If you see this, congratulations are in order! You have a tunnel
 which will protect any IP data from one subnet to the other, as it
 passes between the two gates. If not, go and<A HREF="#trouble">
 troubleshoot</A>.</P>
<P>Note: your new tunnel protects only net-net traffic, not
 gateway-gateway, or gateway-subnet. If you need this (for example, if
 machines on one net need to securely contact a fileserver on the IPsec
 gateway), you'll need to create<A HREF="#adv_config"> extra connections</A>
.</P>
<H3><A NAME="16_2_6">Finishing touches</A></H3>
<P>Now that your connection works, name it something sensible, like:</P>
<PRE>conn winstonnet-toledonet</PRE>
<P>To have the tunnel come up on-boot, replace</P>
<PRE>    auto=add</PRE>
<P>with:</P>
<PRE>    auto=start</PRE>
<P>Copy these changes to the other side, for example:</P>
<PRE>    scp2 ipsec.conf root@ab.example.com:/etc/ipsec.conf</PRE>
<P>Enjoy!</P>
<H2><A name="config.rw"></A>Road Warrior Configuration</H2>
<H3><A name="rw.info.ex">Gather information</A></H3>
<P>You'll need to know:</P>
<UL>
<LI>the gateway's static IP</LI>
<LI>the IP range of the subnet behind that gateway</LI>
<LI>a name by which each side can identify itself for IPsec
 negotiations. Its form is a Fully Qualified Domain Name preceded by an
 @ sign, ie. @road.example.com.
<BR> It does not need to be within a domain that you own. It can be a
 made-up name.</LI>
</UL>
<H4><A NAME="16_3_1_1">Get your leftrsasigkey...</A></H4>
<P>On your laptop, print your IPsec public key:</P>
<PRE>    ipsec showhostkey --left</PRE>
<P>The output should look like this (with the key shortened for easy
 reading):</P>
<PRE>    # RSA 2192 bits   road.example.com   Sun Jun  9 02:45:02 2002
    leftrsasigkey=0sAQPIPN9uI...</PRE>
<P>Don't have a key? See<A HREF="old_config.html#genrsakey"> these
 instructions</A>.</P>
<H4><A NAME="16_3_1_2">...and your rightrsasigkey</A></H4>
<P>Get a console on the gateway:</P>
<PRE>    ssh2 xy.example.com</PRE>
<P>View the gateway's public key with:</P>
<PRE>    ipsec showhostkey --right</PRE>
<P>This will yield something like</P>
<PRE>    # RSA 2048 bits   xy.example.com   Fri Apr 26 15:01:41 2002
    rightrsasigkey=0sAQOnwiBPt...</PRE>
<H3><A NAME="16_3_2">Customize<VAR> /etc/ipsec.conf</VAR></A></H3>
<P>On your laptop, copy this template to<VAR> /etc/ipsec.conf</VAR>. (on
 Mandrake,<VAR> /etc/freeswan/ipsec.conf</VAR>). Substitute the
 information you've gathered for our example data.</P>
<PRE>conn road
    left=%defaultroute             # Picks up our dynamic IP 
    leftnexthop=%defaultroute      # 
    leftid=@road.example.com       # Local information
    leftrsasigkey=0sAQPIPN9uI...   #
    right=192.0.2.10               # Remote information
    rightsubnet=10.0.0.0/24        #
    rightid=@xy.example.com        # 
    rightrsasigkey=0sAQOnwiBPt...  #
    auto=add                       # authorizes but doesn't start this
                                   # connection at startup</PRE>
<P>The template for the gateway is different. Notice how it reverses<VAR>
 left</VAR> and<VAR> right</VAR>, in keeping with our convention that<STRONG>
 L</STRONG>eft is<STRONG> L</STRONG>ocal,<STRONG> R</STRONG>ight<STRONG>
 R</STRONG>emote. Be sure to switch your rsasigkeys in keeping with
 this.</P>
<PRE>    ssh2 xy.example.com
    vi /etc/ipsec.conf</PRE>
<P>and add:</P>
<PRE>conn road
    left=192.0.2.2                 # Gateway's information
    leftid=@xy.example.com         #
    leftsubnet=192.0.2.128/29      #
    leftrsasigkey=0sAQOnwiBPt...   #
    rightnexthop=%defaultroute     # correct in many situations
    right=%any                     # Wildcard: we don't know the laptop's IP
    rightid=@road.example.com      #
    rightrsasigkey=0sAQPIPN9uI...  #
    auto=add                       # authorizes but doesn't start this
                                   # connection at startup</PRE>
<H3><A NAME="16_3_3">Start your connection</A></H3>
<P>You must start the connection from the Road Warrior side. On your
 laptop, type:</P>
<PRE>    ipsec auto --start net-to-net</PRE>
<P>You should see:</P>
<PRE>104 &quot;net-net&quot; #223: STATE_MAIN_I1: initiate
106 &quot;road&quot; #301: STATE_MAIN_I2: sent MI2, expecting MR2
108 &quot;road&quot; #301: STATE_MAIN_I3: sent MI3, expecting MR3
004 &quot;road&quot; #301: STATE_MAIN_I4: ISAKMP SA established
112 &quot;road&quot; #302: STATE_QUICK_I1: initiate
004 &quot;road&quot; #302: STATE_QUICK_I2: sent QI2, IPsec SA established</PRE>
<P>Look for<VAR> IPsec SA established</VAR>. If you're unsuccessful, see
 our<A HREF="#trouble"> troubleshooting tips</A>.</P>
<H3><A NAME="16_3_4">Do not MASQ or NAT packets to be tunneled</A></H3>
<P>If you are using<A HREF="#masq"> IP masquerade</A> or<A HREF="#NAT.gloss">
 Network Address Translation (NAT)</A> on either gateway, you must now
 exempt the packets you wish to tunnel from this treatment. For example,
 if you have a rule like:</P>
<PRE>iptables -t nat -A POSTROUTING -o eth0 -s 10.0.0.0/24 -j MASQUERADE
</PRE>
<P>change it to something like:</P>
<PRE>iptables -t nat -A POSTROUTING -o eth0 -s 10.0.0.0/24 -d \! 192.0.2.128/29 -j MASQUERADE</PRE>
<H3><A NAME="16_3_5">Test your connection</A></H3>
<P>From your laptop, ping a subnet node behind the remote gateway. Do
 not choose the gateway itself for this test.</P>
<PRE>    ping ns.winston.example.com</PRE>
<P>Snoop the packets exiting the laptop, with a command like:</P>
<PRE>    tcpdump -i wlan0</PRE>
<P>You have success if you see (Encapsulating Security Payload) packets
 travelling<B> in both directions</B>:</P>
<PRE>    19:16:32.046220 192.0.2.2 &gt; 192.0.2.9: ESP(spi=0x3be6c4dc,seq=0x3)
    19:16:32.085630 192.0.2.9 &gt; 192.0.2.2: ESP(spi=0x5fdd1cf8,seq=0x6)</PRE>
<P>If you do, great! Traffic between your Road Warrior and the net
 behind your gateway is protected. If not, see our<A HREF="#trouble">
 troubleshooting hints</A>.</P>
<P>Your new tunnel protects only traffic addressed to the net, not to
 the IPsec gateway itself. If you need the latter, you'll want to make
 an<A HREF="#adv_config"> extra tunnel.</A>.</P>
<H3><A NAME="16_3_6">Finishing touches</A></H3>
<P>On both ends, name your connection wisely, like:</P>
<PRE>conn mike-to-office</PRE>
<P><B>On the laptop only,</B> replace</P>
<PRE>    auto=add</PRE>
<P>with:</P>
<PRE>    auto=start</PRE>
<P>so that you'll be connected on-boot.</P>
<P>Happy telecommuting!</P>
<H3><A NAME="16_3_7">Multiple Road Warriors</A></H3>
<P>If you're using RSA keys, as we did in this example, you can add as
 many Road Warriors as you like. The left/rightid parameter lets Linux
 FreeS/WAN distinguish between multiple Road Warrior peers, each with
 its own public key.</P>
<P>The situation is different for shared secrets (PSK). During a PSK
 negotiation, ID information is not available at the time Pluto is
 trying to determine which secret to use, so, effectively, you can only
 define one Roadwarrior connection. All your PSK road warriors must
 therefore share one secret.</P>
<H2><A NAME="16_4">What next?</A></H2>
<P>Using the principles illustrated here, you can try variations such
 as:</P>
<UL>
<LI>a telecommuter with a static IP</LI>
<LI>a road warrior with a subnet behind it</LI>
</UL>
<P>Or, look at some of our<A HREF="#adv_config"> more complex
 configuration examples.</A>.</P>
<HR>
<H1><A name="background">Linux FreeS/WAN background</A></H1>
<P>This section discusses a number of issues which have three things in
 common:</P>
<UL>
<LI>They are not specifically FreeS/WAN problems</LI>
<LI>You may have to understand them to get FreeS/WAN working right</LI>
<LI>They are not simple questions</LI>
</UL>
<P>Grouping them here lets us provide the explanations some users will
 need without unduly complicating the main text.</P>
<P>The explanations here are intended to be adequate for FreeS/WAN
 purposes (please comment to the<A href="mail.html"> users mailing list</A>
 if you don't find them so), but they are not trying to be complete or
 definitive. If you need more information, see the references provided
 in each section.</P>
<H2><A name="dns.background">Some DNS background</A></H2>
<P><A href="#carpediem">Opportunistic encryption</A> requires that the
 gateway systems be able to fetch public keys, and other IPsec-related
 information, from each other's DNS (Domain Name Service) records.</P>
<P><A href="#DNS">DNS</A> is a distributed database that maps names to
 IP addresses and vice versa.</P>
<P>Much good reference material is available for DNS, including:</P>
<UL>
<LI>the<A href="http://www.linuxdoc.org/HOWTO/DNS-HOWTO.html"> DNS HowTo</A>
</LI>
<LI>the standard<A href="#DNS.book"> DNS reference</A> book</LI>
<LI><A href="http://www.linuxdoc.org/LDP/nag2/index.html">Linux Network
 Administrator's Guide</A></LI>
<LI><A href="http://www.nominum.com/resources/whitepapers/bind-white-paper.html">
BIND overview</A></LI>
<LI><A href="http://www.nominum.com/resources/documentation/Bv9ARM.pdf">
BIND 9 Administrator's Reference</A></LI>
</UL>
<P>We give only a brief overview here, intended to help you use DNS for
 FreeS/WAN purposes.</P>
<H3><A name="forward.reverse">Forward and reverse maps</A></H3>
<P>Although the implementation is distributed, it is often useful to
 speak of DNS as if it were just two enormous tables:</P>
<UL>
<LI>the forward map: look up a name, get an IP address</LI>
<LI>the reverse map: look up an IP address, get a name</LI>
</UL>
<P>Both maps can optionally contain additional data. For opportunistic
 encryption, we insert the data need for IPsec authentication.</P>
<P>A system named gateway.example.com with IP address 10.20.30.40 should
 have at least two DNS records, one in each map:</P>
<DL>
<DT>gateway.example.com. IN A 10.20.30.40</DT>
<DD>used to look up the name and get an IP address</DD>
<DT>40.30.20.10.in-addr.arpa. IN PTR gateway.example.com.</DT>
<DD>used for reverse lookups, looking up an address to get the
 associated name. Notice that the digits here are in reverse order; the
 actual address is 10.20.30.40 but we use 40.30.20.10 here.</DD>
</DL>
<H3><A NAME="17_1_2">Hierarchy and delegation</A></H3>
<P>For both maps there is a hierarchy of DNS servers and a system of
 delegating authority so that, for example:</P>
<UL>
<LI>the DNS administrator for example.com can create entries of the form<VAR>
 name</VAR>.example.com</LI>
<LI>the example.com admin cannot create an entry for counterexample.com;
 only someone with authority for .com can do that</LI>
<LI>an admin might have authority for 20.10.in-addr.arpa.</LI>
<LI>in either map, authority can be delegated
<UL>
<LI>the example.com admin could give you authority for
 westcoast.example.com</LI>
<LI>the 20.10.in-addr.arpa admin could give you authority for
 30.20.10.in-addr.arpa</LI>
</UL>
</LI>
</UL>
<P>DNS zones are the units of delegation. There is a hierarchy of zones.</P>
<H3><A NAME="17_1_3">Syntax of DNS records</A></H3>
<P>Returning to the example records:</P>
<PRE>        gateway.example.com. IN A 10.20.30.40
        40.30.20.10.in-addr.arpa. IN PTR gateway.example.com.</PRE>
<P>some syntactic details are:</P>
<UL>
<LI>the IN indicates that these records are for<STRONG> In</STRONG>
ternet addresses</LI>
<LI>The final periods in '.com.' and '.arpa.' are required. They
 indicate the root of the domain name system.</LI>
</UL>
<P>The capitalised strings after IN indicate the type of record.
 Possible types include:</P>
<UL>
<LI><STRONG>A</STRONG>ddress, for forward lookups</LI>
<LI><STRONG>P</STRONG>oin<STRONG>T</STRONG>e<STRONG>R</STRONG>, for
 reverse lookups</LI>
<LI><STRONG>C</STRONG>anonical<STRONG> NAME</STRONG>, records to support
 aliasing, multiple names for one address</LI>
<LI><STRONG>M</STRONG>ail e<STRONG>X</STRONG>change, used in mail
 routing</LI>
<LI><STRONG>SIG</STRONG>nature, used in<A href="#SDNS"> secure DNS</A></LI>
<LI><STRONG>KEY</STRONG>, used in<A href="#SDNS"> secure DNS</A></LI>
<LI><STRONG>T</STRONG>e<STRONG>XT</STRONG>, a multi-purpose record type</LI>
</UL>
<P>To set up for opportunistic encryption, you add some TXT records to
 your DNS data. Details are in our<A href="quickstart.html"> quickstart</A>
 document.</P>
<H3><A NAME="17_1_4">Cacheing, TTL and propagation delay</A></H3>
<P>DNS information is extensively cached. With no caching, a lookup by
 your system of &quot;www.freeswan.org&quot; might involve:</P>
<UL>
<LI>your system asks your nameserver for &quot;www.freeswan.org&quot;</LI>
<LI>local nameserver asks root server about &quot;.org&quot;, gets reply</LI>
<LI>local nameserver asks .org nameserver about &quot;freeswan.org&quot;, gets
 reply</LI>
<LI>local nameserver asks freeswan.org nameserver about
 &quot;www.freeswan.org&quot;, gets reply</LI>
</UL>
<P>However, this can be a bit inefficient. For example, if you are in
 the Phillipines, the closest a root server is in Japan. That might send
 you to a .org server in the US, and then to freeswan.org in Holland. If
 everyone did all those lookups every time they clicked on a web link,
 the net would grind to a halt.</P>
<P>Nameservers therefore cache information they look up. When you click
 on another link at www.freeswan.org, your local nameserver has the IP
 address for that server in its cache, and no further lookups are
 required.</P>
<P>Intermediate results are also cached. If you next go to
 lists.freeswan.org, your nameserver can just ask the freeswan.org
 nameserver for that address; it does not need to query the root or .org
 nameservers because it has a cached address for the freeswan.org zone
 server.</P>
<P>Of course, like any cacheing mechanism, this can create problems of
 consistency. What if the administrator for freeswan.org changes the IP
 address, or the authentication key, for www.freeswan.org? If you use
 old information from the cache, you may get it wrong. On the other
 hand, you cannot afford to look up fresh information every time. Nor
 can you expect the freeswan.org server to notify you; that isn't in the
 protocols.</P>
<P>The solution that is in the protocols is fairly simple. Cacheable
 records are marked with Time To Live (TTL) information. When the time
 expires, the caching server discards the record. The next time someone
 asks for it, the server fetches a fresh copy. Of course, a server may
 also discard records before their TTL expires if it is running out of
 cache space.</P>
<P>This implies that there will be some delay before the new version of
 a changed record propagates around the net. Until the TTLs on all
 copies of the old record expire, some users will see it because that is
 what is in their cache. Other users may see the new record immediately
 because they don't have an old one cached.</P>
<H2><A name="MTU.trouble">Problems with packet fragmentation</A></H2>
<P>It seems, from mailing list reports, to be moderately common for
 problems to crop up in which small packets pass through the IPsec
 tunnels just fine but larger packets fail.</P>
<P>These problems are caused by various devices along the way
 mis-handling either packet fragments or<A href="#pathMTU"> path MTU
 discovery</A>.</P>
<P>IPsec makes packets larger by adding an ESP or AH header. This can
 tickle assorted bugs in fragment handling in routers and firewalls, or
 in path MTU discovery mechanisms, and cause a variety of symptoms which
 are both annoying and, often, quite hard to diagnose.</P>
<P>An explanation from project technical lead Henry Spencer:</P>
<PRE>The problem is IP fragmentation; more precisely, the problem is that the
second, third, etc. fragments of an IP packet are often difficult for
filtering mechanisms to classify.

Routers cannot rely on reassembling the packet, or remembering what was in
earlier fragments, because the fragments may be out of order or may even
follow different routes.  So any general, worst-case filtering decision
pretty much has to be made on each fragment independently.  (If the router
knows that it is the only route to the destination, so all fragments
*must* pass through it, reassembly would be possible... but most routers
don't want to bother with the complications of that.)

All fragments carry roughly the original IP header, but any higher-level
header is (for IP purposes) just the first part of the packet data... so
only the first fragment carries that.  So, for example, on examining the
second fragment of a TCP packet, you could tell that it's TCP, but not
what port number it is destined for -- that information is in the TCP
header, which appears in the first fragment only. 

The result of this classification difficulty is that stupid routers and
over-paranoid firewalls may just throw fragments away.  To get through
them, you must reduce your MTU enough that fragmentation will not occur.
(In some cases, they might be willing to attempt reassembly, but have very
limited resources to devote to it, meaning that packets must be small and
fragments few in number, leading to the same conclusion:  smaller MTU.)</PRE>
<P>In addition to the problem Henry describes, you may also have trouble
 with<A href="#pathMTU"> path MTU discovery</A>.</P>
<P>By default, FreeS/WAN uses a large<A href="#MTU"> MTU</A> for the
 ipsec device. This avoids some problems, but may complicate others.
 Here's an explanation from Claudia:</P>
<PRE>Here are a couple of pieces of background information. Apologies if you
have seen these already. An excerpt from one of my old posts:

    An MTU of 16260 on ipsec0 is usual. The IPSec device defaults to this 
    high MTU so that it does not fragment incoming packets before encryption 
    and encapsulation. If after IPSec processing packets are larger than 1500,
    [ie. the mtu of eth0] then eth0 will fragment them. 

    Adding IPSec headers adds a certain number of bytes to each packet. 
    The MTU of the IPSec interface refers to the maximum size of the packet
    before the IPSec headers are added. In some cases, people find it helpful 
    to set ipsec0's MTU to 1500-(IPSec header size), which IIRC is about 1430.

    That way, the resulting encapsulated packets don't exceed 1500. On most 
    networks, packets less than 1500 will not need to be fragmented.

and... (from Henry Spencer)

    The way it *ought* to work is that the MTU advertised by the ipsecN
    interface should be that of the underlying hardware interface, less a
    pinch for the extra headers needed. 

    Unfortunately, in certain situations this breaks many applications.
    There is a widespread implicit assumption that the smallest MTUs are 
    at the ends of paths, not in the middle, and another that MTUs are 
    never less than 1500.  A lot of code is unprepared to handle paths 
    where there is an &quot;interior minimum&quot; in the MTU, especially when it's 
    less than 1500. So we advertise a big MTU and just let the resulting 
    big packets fragment.

This usually works, but we do get bitten in cases where some intermediate
point can't handle all that fragmentation.  We can't win on this one.</PRE>
<P>The MTU can be changed with an<VAR> overridemtu=</VAR> statement in
 the<VAR> config setup</VAR> section of<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf.5</A>.</P>
<P>For a discussion of MTU issues and some possible solutions using
 Linux advanced routing facilities, see the<A href="http://www.linuxguruz.org/iptables/howto/2.4routing-15.html#ss15.6">
 Linux 2.4 Advanced Routing HOWTO</A>. For a discussion of MTU and NAT
 (Network Address Translation), see<A HREF="http://harlech.math.ucla.edu/services/ipsec.html">
 James Carter's MTU notes</A>.</P>
<H2><A name="nat.background">Network address translation (NAT)</A></H2>
<P><STRONG>N</STRONG>etwork<STRONG> A</STRONG>ddress<STRONG> T</STRONG>
ranslation is a service provided by some gateway machines. Calling it
 NAPT (adding the word<STRONG> P</STRONG>ort) would be more precise, but
 we will follow the widespread usage.</P>
<P>A gateway doing NAT rewrites the headers of packets it is forwarding,
 changing one or more of:</P>
<UL>
<LI>source address</LI>
<LI>source port</LI>
<LI>destination address</LI>
<LI>destination port</LI>
</UL>
<P>On Linux 2.4, NAT services are provided by the<A href="http://netfilter.samba.org">
 netfilter(8)</A> firewall code. There are several<A href="http://netfilter.samba.org/documentation/index.html#HOWTO">
 Netfilter HowTos</A> including one on NAT.</P>
<P>For older versions of Linux, this was referred to as &quot;IP masquerade&quot;
 and different tools were used. See this<A href="http://www.e-infomax.com/ipmasq/">
 resource page</A>.</P>
<P>Putting an IPsec gateway behind a NAT gateway is not recommended. See
 our<A href="#NAT"> firewalls document</A>.</P>
<H3><A NAME="17_3_1">NAT to non-routable addresses</A></H3>
<P>The most common application of NAT uses private<A href="#non-routable">
 non-routable</A> addresses.</P>
<P>Often a home or small office network will have:</P>
<UL>
<LI>one connection to the Internet</LI>
<LI>one assigned publicly visible IP address</LI>
<LI>several machines that all need access to the net</LI>
</UL>
<P>Of course this poses a problem since several machines cannot use one
 address. The best solution might be to obtain more addresses, but often
 this is impractical or uneconomical.</P>
<P>A common solution is to have:</P>
<UL>
<LI><A href="#non-routable">non-routable</A> addresses on the local
 network</LI>
<LI>the gateway machine doing NAT</LI>
<LI>all packets going outside the LAN rewritten to have the gateway as
 their source address</LI>
</UL>
<P>The client machines are set up with reserved<A href="#non-routable">
 non-routable</A> IP addresses defined in RFC 1918. The masquerading
 gateway, the machine with the actual link to the Internet, rewrites
 packet headers so that all packets going onto the Internet appear to
 come from one IP address, that of its Internet interface. It then gets
 all the replies, does some table lookups and more header rewriting, and
 delivers the replies to the appropriate client machines.</P>
<P>As far as anyone else on the Internet is concerned, the systems
 behind the gateway are completely hidden. Only one machine with one IP
 address is visible.</P>
<P>For IPsec on such a gateway, you can entirely ignore the NAT in:</P>
<UL>
<LI><A href="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</A></LI>
<LI>firewall rules affecting your Internet-side interface</LI>
</UL>
<P>Those can be set up exactly as they would be if your gateway had no
 other systems behind it.</P>
<P>You do, however, have to take account of the NAT in firewall rules
 which affect packet forwarding.</P>
<H3><A NAME="17_3_2">NAT to routable addresses</A></H3>
<P>NAT to routable addresses is also possible, but is less common and
 may make for rather tricky routing problems. We will not discuss it
 here. See the<A href="http://netfilter.samba.org/documentation/index.html#HOWTO">
 Netfilter HowTos</A>.</P>
<HR>
<H1><A name="user.examples">FreeS/WAN script examples</A></H1>
 This file is intended to hold a collection of user-written example
 scripts or configuration files for use with FreeS/WAN.
<P> So far it has only one entry.</P>
<H2><A name="poltorak">Poltorak's Firewall script</A></H2>
<PRE>
From: Poltorak Serguei &lt;poltorak@dataforce.net&gt;
Subject: [Users] Using FreeS/WAN
Date: Tue, 16 Oct 2001

Hello.

I'm using FreeS/WAN IPsec for half a year. I learned a lot of things about
it and I think it would be interesting for someone to see the result of my
experiments and usage of FreeS/WAN. If you find a mistake in this
file, please e-mail me. And excuse me for my english... I'm learning.. :)

I'll talk about vary simple configuration:

addresses prefix = 192.168

    lan1          sgw1     .0.0/24 (Internet)       sgw2            lan2
  .1.0/24---[ .1.1 ; .0.1 ]===================[ .0.10 ; . 2.10 ]---.2.0/24


We need to let lan1 see lan2 across Internet like it is behind sgw1. The
same for lan2. And we need to do IPX bridge for Novel Clients and NDS
synchronization.

my config:
------------------- ipsec.conf -------------------
conn lan1-lan2
        type=tunnel
        compress=yes
        #-------------------
        left=192.168.0.1
        leftsubnet=192.168.1.0/24
        #-------------------
        right=192.168.0.10
        rightsubnet=192.168.2.0/24
        #-------------------
        auth=esp
        authby=secret
--------------- end of ipsec.conf ----------------

ping .2.x from .1.y   (y != 1)
It works?? Fine. Let's continue...

Why y != 1 ?? Because kernel of sgw1 have 2 IP addresses and it will choose
the first IP (which is used to go to Internet) .0.1 and the packet won't go
through IPsec tunnel :(  But if do ping on .1.1 kernel will respond from
that address (.1.1) and the packet will be tunneled. The same problem occurred then
.2.x sends a packet to .1.2 which is down at the moment. What happens? .1.1
sends ARP requesting .1.2... after 3 tries it send to .2.x an destunreach,
but from his &quot;natural&quot; IP or .0.1 . So the error message won't be delivered!
It's a big problem...

Resolution... One can manipulate with ipsec0 or ipsec0:0 to solve the
problem (if ipsec0 has .1.1 kernel will send packets correctly), but there
are powerful and elegant iproute2 :) We simply need to change source address
of packet that goes to other secure lan. This is done with

ip route replace 192.168.2.0/24 via 192.168.0.10 dev ipsec0 src 192.168.1.1

Cool!! Now it works!!

The second step. We want install firewall on sgw1 and sgw2. Encryption of 
traffic without security isn't a good idea. I don't use {left|right}firewall, 
because I'm running firewall from init scripts.

We want IPsec data between lan1-lan2, some ICMP errors (destination
unreachable, TTL exceeded, parameter problem and source quench), replying on 
pings from both lans and Internet, ipxtunnel data for IPX and of course SSH
between sgw1 and sgw2 and from/to one specified host.

I'm using ipchains. With iptables there are some changes.

---------------- rc.firewall ---------------------
#!/bin/sh
#
# Firewall for IPsec lan1-lan2
#

IPC=/sbin/ipchains
ANY=0.0.0.0/0

# left
SGW1_EXT=192.168.0.1
SGW1_INT=192.168.1.1
LAN1=192.168.1.0/24

# right
SGW2_EXT=192.168.0.10
SGW2_INT=192.168.2.10
LAN2=192.168.2.0/24

# SSH from and to this host
SSH_PEER_HOST=_SOME_HOST_

# this is for left. exchange these values for right.
MY_EXT=$SGW1_EXT
MY_INT=$SGW1_INT
PEER_EXT=$SGW2_EXT
PEER_INT=$SGW2_INT
INT_IF=eth1
EXT_IF=eth0
IPSEC_IF=ipsec0
MY_LAN=$LAN1
PEER_LAN=$LAN2

$IPC -F
$IPC -P input DENY
$IPC -P forward DENY
$IPC -P output DENY

# Loopback traffic
$IPC -A input -i lo -j ACCEPT
$IPC -A output -i lo -j ACCEPT

# for IPsec SGW1-SGW2
## IKE
$IPC -A input -p udp -s $PEER_EXT 500 -d $MY_EXT 500 -i $EXT_IF -j ACCEPT
$IPC -A output -p udp -s $MY_EXT 500 -d $PEER_EXT 500 -i $EXT_IF -j ACCEPT
## ESP
$IPC -A input -p 50 -s $PEER_EXT -d $MY_EXT -i $EXT_IF -j ACCEPT
### we don't need this line ### $IPC -A output -p 50 -s $MY_EXT -d $PEER_EXT -i $EXT_IF -j ACCEPT
## forward LAN1-LAN2
$IPC -A forward -s $MY_LAN -d $PEER_LAN -i $IPSEC_IF -j ACCEPT
$IPC -A forward -s $PEER_LAN -d $MY_LAN -i $INT_IF -j ACCEPT
$IPC -A output -s $PEER_LAN -d $MY_LAN -i $INT_IF -j ACCEPT
$IPC -A input -s $PEER_LAN -d $MY_LAN -i $IPSEC_IF -j ACCEPT
$IPC -A input -s $MY_LAN -d $PEER_LAN -i $INT_IF -j ACCEPT
$IPC -A output -s $MY_LAN -d $PEER_LAN -i $IPSEC_IF -j ACCEPT

# ICMP
#
## Dest unreachable
### from/to Internet
$IPC -A input -p icmp --icmp-type destination-unreachable -s $ANY -d $MY_EXT -i $EXT_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type destination-unreachable -s $MY_EXT -d $ANY -i $EXT_IF -j ACCEPT
### from/to Lan
$IPC -A input -p icmp --icmp-type destination-unreachable -s $ANY -d $MY_INT -i $INT_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type destination-unreachable -s $MY_INT -d $ANY -i $INT_IF -j ACCEPT
### from/to Peer Lan
$IPC -A input -p icmp --icmp-type destination-unreachable -s $ANY -d $MY_INT -i $IPSEC_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type destination-unreachable -s $MY_INT -d $ANY -i $IPSEC_IF -j ACCEPT
#
## Source quench
### from/to Internet
$IPC -A input -p icmp --icmp-type source-quench -s $ANY -d $MY_EXT -i $EXT_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type source-quench -s $MY_EXT -d $ANY -i $EXT_IF -j ACCEPT
### from/to Lan
$IPC -A input -p icmp --icmp-type source-quench -s $ANY -d $MY_INT -i $INT_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type source-quench -s $MY_INT -d $ANY -i $INT_IF -j ACCEPT
### from/to Peer Lan
$IPC -A input -p icmp --icmp-type source-quench -s $ANY -d $MY_INT -i $IPSEC_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type source-quench -s $MY_INT -d $ANY -i $IPSEC_IF -j ACCEPT
#
## Parameter problem
### from/to Internet
$IPC -A input -p icmp --icmp-type parameter-problem -s $ANY -d $MY_EXT -i $EXT_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type parameter-problem -s $MY_EXT -d $ANY -i $EXT_IF -j ACCEPT
### from/to Lan
$IPC -A input -p icmp --icmp-type parameter-problem -s $ANY -d $MY_INT -i $INT_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type parameter-problem -s $MY_INT -d $ANY -i $INT_IF -j ACCEPT
### from/to Peer Lan
$IPC -A input -p icmp --icmp-type parameter-problem -s $ANY -d $MY_INT -i $IPSEC_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type parameter-problem -s $MY_INT -d $ANY -i $IPSEC_IF -j ACCEPT
#
## Time To Live exceeded
### from/to Internet
$IPC -A input -p icmp --icmp-type time-exceeded -s $ANY -d $MY_EXT -i $EXT_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type time-exceeded -s $MY_EXT -d $ANY -i $EXT_IF -j ACCEPT
### to Lan
$IPC -A input -p icmp --icmp-type time-exceeded -s $ANY -d $MY_INT -i $INT_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type time-exceeded -s $MY_INT -d $ANY -i $INT_IF -j ACCEPT
### to Peer Lan
$IPC -A input -p icmp --icmp-type time-exceeded -s $ANY -d $MY_INT -i $IPSEC_IF -j ACCEPT
$IPC -A output -p icmp --icmp-type time-exceeded -s $MY_INT -d $ANY -i $IPSEC_IF -j ACCEPT

# ICMP PINGs
## from Internet
$IPC -A input -p icmp -s $ANY -d $MY_EXT --icmp-type echo-request  -i $EXT_IF -j ACCEPT
$IPC -A output -p icmp -s $MY_EXT -d $ANY --icmp-type echo-reply  -i $EXT_IF -j ACCEPT
## from LAN
$IPC -A input -p icmp -s $ANY -d $MY_INT --icmp-type echo-request -i $INT_IF -j ACCEPT
$IPC -A output -p icmp -s $MY_INT -d $ANY --icmp-type echo-reply  -i $INT_IF -j ACCEPT
## from Peer LAN
$IPC -A input -p icmp -s $ANY -d $MY_INT --icmp-type echo-request -i $IPSEC_IF -j ACCEPT
$IPC -A output -p icmp -s $MY_INT -d $ANY --icmp-type echo-reply  -i $IPSEC_IF -j ACCEPT

# SSH
## from SSH_PEER_HOST
$IPC -A input -p tcp -s $SSH_PEER_HOST -d $MY_EXT 22 -i $EXT_IF -j ACCEPT
$IPC -A output -p tcp \! -y -s $MY_EXT 22 -d $SSH_PEER_HOST -i $EXT_IF -j ACCEPT
## to SSH_PEER_HOST
$IPC -A input -p tcp \! -y -s $SSH_PEER_HOST 22 -d $MY_EXT -i $EXT_IF -j ACCEPT
$IPC -A output -p tcp -s $MY_EXT -d $SSH_PEER_HOST 22 -i $EXT_IF -j ACCEPT
## from PEER
$IPC -A input -p tcp -s $PEER_EXT -d $MY_EXT 22 -i $EXT_IF -j ACCEPT
$IPC -A output -p tcp \! -y -s $MY_EXT 22 -d $PEER_EXT -i $EXT_IF -j ACCEPT
## to PEER
$IPC -A input -p tcp \! -y -s $PEER_EXT 22 -d $MY_EXT -i $EXT_IF -j ACCEPT
$IPC -A output -p tcp -s $MY_EXT -d $PEER_EXT 22 -i $EXT_IF -j ACCEPT

# ipxtunnel
$IPC -A input -p udp -s $PEER_INT 2005 -d $MY_INT 2005 -i $IPSEC_IF -j ACCEPT
$IPC -A output -p udp -s $MY_INT 2005 -d $PEER_INT 2005 -i $IPSEC_IF -j ACCEPT

---------------- end of rc.firewall ----------------------

To understand this we need to look on this scheme:

           ++-----------------------&lt;----------------------------+
           || ipsec0                                             |
           \/                                                    |
 eth0  +--------+    /---------/ yes  /---------/ yes +-----------------------+
------&gt;| INPUT  |--&gt;/ ?local? /-----&gt;/ ?IPsec? /-----&gt;| decrypt decapsulate |
 eth1  +--------+  /---------/      /---------/       +-----------------------+
                       || no            || no
                       \/               \/
                  +----------+      +---------+        +-------+
                  | routing  |      |  local  |        | local |
                  | decision |      | deliver |        | send  |
                  +----------+      +---------+        +-------+
                       ||                                 ||
                       \/                                 \/
                   +---------+                       +----------+
                   | forward |                       | routing  |
                   +---------+                       | decision |
                       ||                            +----------+
                       ||                                  ||
                       ++----------------&lt;-----------------++
                       ||
                       \/
                   +--------+ eth0
                   | OUTPUT | eth1
                   +--------+ ipsec0
                       ||
                       \/
                   /---------/ yes +-----------------------+
                  / ?IPsec? /-----&gt;| encrypt encapsulate |
                 /---------/       +-----------------------+
                      || no                    ||
                      ||                       ||
                      ||                       \/   eth0, eth1
                      ++-----------------------++--------------&gt;

This explain how a packet traverse TCP/IP stack in IPsec capable kernel.

FIX ME, please, if there are any errors

Test the new firewall now.


Now about IPX. I tried 3 programs for tunneling IPX: tipxd, SIB and ipxtunnel

tipxd didn't send packets.. :(
SIB and ipxtunnel worked fine :)
With ipxtunnel there was a little problem. In sources there are an error.

--------------------- in main.c ------------------------
&lt;       bytes += p.len;
---
&gt;       bytes += len;
--------------------------------------------------------

After this FIX everything goes right...

------------------- /etc/ipxtunnel.conf ----------------
port    2005
remote  192.168.101.97    2005
interface eth1
--------------- end of /etc/ipxtunnel.conf -------------

I use IPX tunnel between .1.1 and .2.10 so we don't need to encrypt nor
authenticate encapsulated IPX packets, it is done with IPsec.

If you don't wont to use iproute2 to change source IP you need to use SIB
(it is able to bind local address) or establish tunnel between .0.1 and
.0.10 (external IPs, you need to do encryption in the program, but it isn't
strong).

For now I'm using ipxtunnel.

I think that's all for the moment. If there are any error, please e-mail me: 
poltorak@df.ru . It would be cool if someone puts the scheme of TCP/IP in
kernel and firewall example on FreeS/WAN's manual pages.

PoltoS
</PRE>
<HR>
<H1><A name="makecheck">How to configure to use &quot;make check&quot;</A></H1>
<H2><A NAME="19_1">What is &quot;make check&quot;</A></H2>
<P> &quot;make check&quot; is a target in the top level makefile. It takes care of
 running a number of unit and system tests to confirm that FreeSWAN has
 been compiled correctly, and that no new bugs have been introduced.</P>
<P> As FreeSWAN contains both kernel and userspace components, doing
 testing of FreeSWAN requires that the kernel be simulated. This is
 typically difficult to do as a kernel requires that it be run on bare
 hardware. A technology has emerged that makes this simpler. This is<A HREF="http://user-mode-linux.sourceforge.net">
 User Mode Linux</A>.</P>
<P> User-Mode Linux is a way to build a Linux kernel such that it can
 run as a process under another Linux (or in the future other) kernel.
 Presently, this can only be done for 2.4 guest kernels. The host kernel
 can be 2.2 or 2.4.</P>
<P> &quot;make check&quot; expects to be able to build User-Mode Linux kernels
 with FreeSWAN included. To do this it needs to have some files
 downloaded and extracted prior to running &quot;make check&quot;. This is
 described in the<A HREF="umltesting.html"> UML testing</A> document.</P>
<P> After having run the example in the UML testing document and
 successfully brought up the four machine combination, you are ready to
 use &quot;make check&quot;</P>
<H2><A NAME="19_2">Running &quot;make check&quot;</A></H2>
<P> &quot;make check&quot; works by walking the FreeSWAN source tree invoking the
 &quot;check&quot; target at each node. At present there are tests defined only
 for the <CODE>klips</CODE> directory. These tests will use the UML
 infrastructure to test out pieces of the <CODE>klips</CODE> code.</P>
<P> The results of the tests can be recorded. If the environment
 variable <CODE>$REGRESSRESULTS</CODE> is non-null, then the results of
 each test will be recorded. This can be used as part of a nightly
 regression testing system, see<A HREF="nightly.html"> Nightly testing</A>
 for more details.</P>
<P> &quot;make check&quot; otherwise prints a minimal amount of output for each
 test, and indicates pass/fail status of each test as they are run.
 Failed tests do not cause failure of the target in the form of exit
 codes.</P>
<H1><A NAME="20">How to write a &quot;make check&quot; test</A></H1>
<H2><A NAME="20_1">Structure of a test</A></H2>
<P> Each test consists of a set of directories under <CODE>testing/</CODE>
. There are directories for <CODE>klips</CODE>, <CODE>pluto</CODE>, <CODE>
packaging</CODE> and <CODE>libraries</CODE>. Each directory has a list
 of tests to run is stored in a file called <CODE>TESTLIST</CODE> in
 that directory. e.g. <CODE>testing/klips/TESTLIST</CODE>.</P>
<H2 NAME="TESTLIST"><A NAME="20_2">The TESTLIST</A></H2>
<P> This isn't actually a shell script. It just looks like one. Some
 tools other than /bin/sh process it. Lines that start with # are
 comments.</P>
<PRE>
# test-kind     directory-containing-test       expectation     [PR#]
</PRE>
<P>The first word provides the test type, detailed below.</P>
<P> The second word is the name of the test to run. This the directory
 in which the test case is to be found..</P>
<P>The third word may be one of:</P>
<DL>
<DT> blank/good</DT>
<DD>the test is believed to function, report failure</DD>
<DT> bad</DT>
<DD> the test is known to fail, report unexpected success</DD>
<DT> suspended</DT>
<DD> the test should not be run</DD>
</DL>
<P> The fourth word may be a number, which is a PR# if the test is
 failing.</P>
<H2><A NAME="20_3">Test kinds</A></H2>
 The test types are:
<DL>
<DT>skiptest</DT>
<DD>means run no test.</DD>
<DT>ctltest</DT>
<DD>means run a single system without input/output.</DD>
<DT>klipstest</DT>
<DD>means run a single system with input/output networks</DD>
<DT><A HREF="#umlplutotest">umlplutotest</A></DT>
<DD>means run a pair of systems</DD>
<DT><A HREF="#umlXhost">umlXhost</A></DT>
<DD>run an arbitrary number of systems</DD>
<DT>suntest (TBD)</DT>
<DD>means run a quad of east/west/sunrise/sunset</DD>
<DT>roadtest (TBD)</DT>
<DD>means run a trio of east-sunrise + warrior</DD>
<DT>extrudedtest (TBD)</DT>
<DD>means run a quad of east-sunrise + warriorsouth + park</DD>
<DT>mkinsttest</DT>
<DD>a test of the &quot;make install&quot; machinery.</DD>
<DT>kernel_test_patch</DT>
<DD>a test of the &quot;make kernelpatch&quot; machinery.</DD>
</DL>
 Tests marked (TBD) have yet to be fully defined.
<P> Each test directory has a file in it called <CODE>testparams.sh</CODE>
. This file sets a number of environment variables to define the
 parameters of the test.</P>
<H2><A NAME="20_4">Common parameters</A></H2>
<DL>
<DT>TESTNAME</DT>
<DD>the name of the test (repeated for checking purposes)</DD>
<DT>TEST_TYPE</DT>
<DD>the type of the test (repeat of type type above)</DD>
<DT>TESTHOST</DT>
<DD>the name of the UML machine to run for the test, typically &quot;east&quot; or
 &quot;west&quot;</DD>
<DT>TEST_PURPOSE</DT>
<DD>The purpose of the test is one of:
<DL>
<DT>goal</DT>
<DD>The goal purpose is where a test is defined for code that is not yet
 finished. The test indicates when the goals have in fact been reached.</DD>
<DT>regress</DT>
<DD>This is a test to determine that a previously existing bug has been
 repaired. This test will initially be created to reproduce the bug in
 isolation, and then the bug will be fixed.</DD>
<DT>exploit</DT>
<DD>This is a set of packets/programs that causes a vulnerability to be
 exposed. It is a specific variation of the regress option.</DD>
</DL>
</DD>
<DT>TEST_GOAL_ITEM</DT>
<DT></DT>
<DD>in the case of a goal test, this is a reference to the requirements
 document</DD>
<DT>TEST_PROB_REPORT</DT>
<DD>in the case of regression test, this the problem report number from
 GNATS</DD>
<DT>TEST_EXPLOIT_URL</DT>
<DD>in the case of an exploit, this is a URL referencing the paper
 explaining the origin of the test and the origin of exploit software</DD>
<DT>REF_CONSOLE_OUTPUT</DT>
<DD>a file in the test directory that contains the sanitized console
 output against which to compare the output of the actual test.</DD>
<DT>REF_CONSOLE_FIXUPS</DT>
<DD>a list of scripts (found in <CODE>klips/test/fixups</CODE>) to apply
 to sanitize the console output of the machine under test. These are
 typically perl, awk or sed scripts that remove things in the kernel
 output that change each time the test is run and/or compiled.</DD>
<DT>INIT_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode prior to starting the tests. This file will usually
 set up any eroute's and SADB entries that are required for the test.</P>
<P>Lines beginning with # are skipped. Blank lines are skipped.
 Otherwise, a shell prompted is waited for each time (consisting of <CODE>
\n#</CODE>) and then the command is sent. Note that the prompt is waited
 for before the command and not after, so completion of the last command
 in the script is not required. This is often used to invoke a program
 to monitor the system, e.g. <CODE>ipsec pf_key</CODE>.</P>
</DD>
<DT>RUN_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode, before the packets are sent. On single machine tests,
 this script doesn't provide any more power than INIT_SCRIPT, but is
 implemented for consistency's sake.</P>
</DD>
<DT>FINAL_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode after the final packet is sent. Similar to
 INIT_SCRIPT, above. If not specified, then the single command &quot;halt&quot; is
 sent. If specified, then the script should end with a halt command to
 nicely shutdown the UML.</P>
</DD>
<DT>CONSOLEDIFFDEBUG</DT>
<DD>If set to &quot;true&quot; then the series of console fixups (see
 REF_CONSOLE_FIXUPS) will be output after it is constructed. (It should
 be set to &quot;false&quot;, or unset otherwise)</DD>
<DT>NETJIGDEBUG</DT>
<DD>If set to &quot;true&quot; then the series of console fixups (see
 REF_CONSOLE_FIXUPS) will be output after it is constructed. (It should
 be set to &quot;false&quot;, or unset otherwise)</DD>
<DT>NETJIGTESTDEBUG</DT>
<DD> If set to &quot;netjig&quot;, then the results of talking to the <CODE>
uml_netjig</CODE> will be printed to stderr during the test. In
 addition, the jig will be invoked with --debug, which causes it to log
 its process ID, and wait 60 seconds before continuing. This can be used
 if you are trying to debug the <CODE>uml_netjig</CODE> program itself.</DD>
<DT>HOSTTESTDEBUG</DT>
<DD> If set to &quot;hosttest&quot;, then the results of taling to the consoles of
 the UMLs will be printed to stderr during the test.</DD>
<DT>NETJIGWAITUSER</DT>
<DD> If set to &quot;waituser&quot;, then the scripts will wait forever for user
 input before they shut the tests down. Use this is if you are debugging
 through the kernel.</DD>
<DT>PACKETRATE</DT>
<DD> A number, in miliseconds (default is 500ms) at which packets will
 be replayed by the netjig.</DD>
</DL>
<H2><A NAME="20_5">KLIPStest paramaters</A></H2>
<P> The klipstest function starts a program (<CODE>
testing/utils/uml_netjig/uml_netjig</CODE>) to setup a bunch of I/O
 sockets (that simulate network interfaces). It then exports the
 references to these sockets to the environment and invokes (using
 system()) a given script. It waits for the script to finish.</P>

<!-- <IMG SRC="single_netjig.png" ALT="block diagram of uml_netjig"> -->
<P> The script invoked (<CODE>testing/utils/host-test.tcl</CODE>) is a
 TCL<A HREF="http://expect.nist.gov/"> expect</A> script that arranges
 to start the UML and configure it appropriately for the test. The
 configuration is done with the script given above for<VAR> INIT_SCRIPT</VAR>
. The TCL script then forks, leaves the UML in the background and exits.
 uml_netjig continues. It then starts listening to the simulated network
 answering ARPs and inserting packets as appropriate.</P>
<P> The klipstest function invokes <CODE>uml_netjig</CODE> with
 arguments to capture output from network interface(s) and insert
 packets as appropriate:</P>
<DL>
<DT>PUB_INPUT</DT>
<DD>a<A HREF="http://www.tcpdump.org/"> pcap</A> file to feed in on the
 public (encrypted) interface. (typically, eth1)</DD>
<DT>PRIV_INPUT</DT>
<DD>a pcap file to feed in on the private (plain-text) interface
 (typically, eth0).</DD>
<DT>REF_PUB_OUTPUT</DT>
<DD>a text file containing tcpdump output. Packets on the public (eth1)
 interface are captured to a<A HREF="http://www.tcpdump.org/"> pcap</A>
 file by <CODE>uml_netjig</CODE>. The klipstest function then uses
 tcpdump on the file to produce text output, which is compared to the
 file given.</DD>
<DT>REF_PUB_FILTER</DT>
<DD>a program that will filter the TCPDUMP output to do further
 processing. Defaults to &quot;cat&quot;.</DD>
<DT>REF_PRIV_OUTPUT</DT>
<DD>a text file containing tcpdump output. Packets on the private (eth0)
 interface are captured and compared after conversion by tcpdump, as
 with<VAR> REFPUBOUTPUT</VAR>.</DD>
<DT>REF_PRIV_FILTER</DT>
<DD>a program that will filter the TCPDUMP output to do further
 processing. Defaults to &quot;cat&quot;.</DD>
<DT>EXITONEMPTY</DT>
<DD>a flag for <CODE>uml_netjig</CODE>. It should contain
 &quot;--exitonempty&quot; of uml_netjig should exit when all of the input (<VAR>
PUBINPUT</VAR>,<VAR>PRIVINPUT</VAR>) packets have been injected.</DD>
<DT>ARPREPLY</DT>
<DD>a flag for <CODE>uml_netjig</CODE>. It should contain &quot;--arpreply&quot;
 if <CODE>uml_netjig</CODE> should reply to ARP requests. One will
 typically set this to avoid having to fudge the ARP cache manually.</DD>
<DT>TCPDUMPFLAGS</DT>
<DD>a set of flags for the tcpdump used when converting captured output.
 Typical values will include &quot;-n&quot; to turn off DNS, and often &quot;-E&quot; to set
 the decryption key (tcpdump 3.7.1 and higher only) for ESP packets. The
 &quot;-t&quot; flag (turn off timestamps) is provided automatically</DD>
<DT>NETJIG_EXTRA</DT>
<DD>additional comments to be sent to the netjig. This may arrange to
 record or create additional networks, or may toggle options.</DD>
</DL>
<H2><A NAME="20_6">mkinsttest paramaters</A></H2>
<P> The basic concept of the <CODE>mkinsttest</CODE> test type is that
 it performs a &quot;make install&quot; to a temporary $DESTDIR. The resulting
 tree can then be examined to determine if it was done properly. The
 files can be uninstalled to determine if the file list was correct, or
 the contents of files can be examined more precisely.</P>
<DL>
<DT>INSTALL_FLAGS</DT>
<DD>If set, then an install will be done. This provides the set of flags
 to provide for the install. The target to be used (usually &quot;install&quot;)
 must be among the flags.</DD>
<DT>POSTINSTALL_SCRIPT</DT>
<DD>If set, a script to run after initial &quot;make install&quot;. Two arguments
 are provided: an absolute path to the root of the FreeSWAN src tree,
 and an absolute path to the temporary installation area.</DD>
<DT>INSTALL2_FLAGS</DT>
<DD>If set, a second install will be done using these flags. Similarly
 to INSTALL_FLAGS, the target must be among the flags.</DD>
<DT>UNINSTALL_FLAGS</DT>
<DD>If set, an uninstall will be done using these flags. Similarly to
 INSTALL_FLAGS, the target (usually &quot;uninstall&quot;) must be among the
 flags.</DD>
<DT>REF_FIND_f_l_OUTPUT</DT>
<DD>If set, a <CODE>find $ROOT ( -type f -or -type -l )</CODE> will be
 done to get a list of a real files and symlinks. The resulting file
 will be compared to the file listed by this option.</DD>
<DT>REF_FILE_CONTENTS</DT>
<DD>If set, it should point to a file containing records for the form:
<PRE>
  
<!--VARIABLE-->
reffile</(null)>   
<!--VARIABLE-->
samplefile</(null)>
</PRE>
 one record per line. A diff between the provided reference file, and
 the sample file (located in the temporary installation root) will be
 done for each record.</DD>
</DL>
<H2><A NAME="20_7">rpm_build_install_test paramaters</A></H2>
<P> The <CODE>rpm_build_install_test</CODE> type is to verify that the
 proper packing list is produced by &quot;make rpm&quot;, and that the mechanisms
 for building the kernel modules produce consistent results.</P>
<DL>
<DT>RPM_KERNEL_SOURCE</DT>
<DD>Point to an extracted copy of the RedHat kernel source code.
 Variables from the environment may be used.</DD>
<DT>REF_RPM_CONTENTS</DT>
<DD>This is a file containing one record per line. Each record consists
 of a RPM name (may contain wildcards) and a filename to compare the
 contents to. The RPM will be located and a file list will be produced
 with rpm2cpio.</DD>
</DL>
<H2><A NAME="20_8">libtest paramaters</A></H2>
<P> The libtest test is for testing library routines. The library file
 is expected to provided an <CODE>#ifdef</CODE> by the name of<VAR>
 library</VAR>
<!--CODE_MAIN</CODE-->
. The libtest type invokes the C compiler to compile this
 file, links it against <CODE>libfreeswan.a</CODE> (to resolve any other
 dependancies) and runs the test with the <CODE>-r</CODE> argument to
 invoke a regression test.</(null)></P>
<P>The library test case is expected to do a self-test, exiting with
 status code 0 if everything is okay, and with non-zero otherwise. A
 core dump (exit code greater than 128) is noted specifically.</P>
<P> Unlike other tests, there are no subdirectories required, or other
 parameters to set.</P>
<H2 NAME="umlplutotest"><A NAME="20_9">umlplutotest paramaters</A></H2>
<P> The umlplutotest function starts a pair of user mode line processes.
 This is a 2-host version of umlXhost. The &quot;EAST&quot; and &quot;WEST&quot; slots are
 defined.</P>
<H2 NAME="umlXhost"><A NAME="20_10">umlXhost parameters</A></H2>
<P> The umlXtest function starts an arbitrary number of user mode line
 processes.</P>

<!-- <IMG SRC="single_netjig.png" ALT="block diagram of uml_netjig"> -->
<P> The script invoked (<CODE>testing/utils/Xhost-test.tcl</CODE>) is a
 TCL<A HREF="http://expect.nist.gov/"> expect</A> script that arranges
 to start each UML and configure it appropriately for the test. It then
 starts listening (using uml_netjig) to the simulated network answering
 ARPs and inserting packets as appropriate.</P>
<P> umlXtest has a series of slots, each of which should be filled by a
 host. The list of slots is controlled by the variable, XHOST_LIST. This
 variable should be set to a space seperated list of slots. The former
 umlplutotest is now implemented as a variation of the umlXhost test,
 with XHOST_LIST=&quot;EAST WEST&quot;.</P>
<P> For each host slot that is defined, a series of variables should be
 filled in, defining what configuration scripts to use for that host.</P>
<P> The following are used to control the console input and output to
 the system. Where the string ${host} is present, the host slot should
 be filled in. I.e. for the two host system with XHOST_LIST=&quot;EAST WEST&quot;,
 then the variables: EAST_INIT_SCRIPT and WEST_INIT_SCRIPT will exist.</P>
<DL>
<DT>${host}HOST</DT>
<DD>The name of the UML host which will fill this slot</DD>
<DT>${host}_INIT_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode prior to starting the tests. This file will usually
 set up any eroute's and SADB entries that are required for the test.
 Similar to INIT_SCRIPT, above.</P>
</DD>
<DT>${host}_RUN_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode, before the packets are sent. This set of commands is
 run after all of the virtual machines are initialized. I.e. after
 EAST_INIT_SCRIPT<B> AND</B> WEST_INIT_SCRIPT. This script can therefore
 do things that require that all machines are properly configured.</P>
</DD>
<DT>${host}_RUN2_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode, after the packets are sent. This set of commands is
 run before any of the virtual machines have been shut down. (I.e.
 before EAST_FINAL_SCRIPT<B> AND</B> WEST_FINAL_SCRIPT.) This script can
 therefore catch post-activity status reports.</P>
</DD>
<DT>${host}_FINAL_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode after the final packet is sent. Similar to
 INIT_SCRIPT, above. If not specified, then the single command &quot;halt&quot; is
 sent. Note that when this script is run, the other virtual machines may
 already have been killed. If specified, then the script should end with
 a halt command to nicely shutdown the UML.</P>
</DD>
<DT>REF_${host}_CONSOLE_OUTPUT</DT>
<DD>Similar to REF_CONSOLE_OUTPUT, above.</DD>
</DL>
<P>Some additional flags apply to all hosts:</P>
<DL>
<DT>REF_CONSOLE_FIXUPS</DT>
<DD>a list of scripts (found in <CODE>klips/test/fixups</CODE>) to apply
 to sanitize the console output of the machine under test. These are
 typically perl, awk or sed scripts that remove things in the kernel
 output that change each time the test is run and/or compiled.</DD>
</DL>
<P> In addition to input to the console, the networks may have input fed
 to them:</P>
<DL>
<DT>EAST_INPUT/WEST_INPUT</DT>
<DD>a<A HREF="http://www.tcpdump.org/"> pcap</A> file to feed in on the
 private network side of each network. The &quot;EAST&quot; and &quot;WEST&quot; here refer
 to the networks, not the hosts.</DD>
<DT>REF_PUB_FILTER</DT>
<DD>a program that will filter the TCPDUMP output to do further
 processing. Defaults to &quot;cat&quot;.</DD>
<DT>REF_EAST_FILTER/REF_WEST_FILTER</DT>
<DD>a program that will filter the TCPDUMP output to do further
 processing. Defaults to &quot;cat&quot;.</DD>
&lt;
<DT>TCPDUMPFLAGS</DT>
<DD>a set of flags for the tcpdump used when converting captured output.
 Typical values will include &quot;-n&quot; to turn off DNS, and often &quot;-E&quot; to set
 the decryption key (tcpdump 3.7.1 and higher only) for ESP packets. The
 &quot;-t&quot; flag (turn off timestamps) is provided automatically</DD>
<DT>REF_EAST_OUTPUT/REF_WEST_OUTPUT</DT>
<DD>a text file containing tcpdump output. Packets on the private (eth0)
 interface are captured and compared after conversion by tcpdump, as
 with<VAR> REF_PUB_OUTPUT</VAR>.</DD>
<P> There are two additional environment variables that may be set on
 the command line:</P>
<DL>
<DT> NETJIGVERBOSE=verbose export NETJIGVERBOSE</DT>
<DD> If set, then the test output will be &quot;chatty&quot;, and let you know
 what commands it is running, and as packets are sent. Without it set,
 the output is limited to success/failure messages.</DD>
<DT> NETJIGTESTDEBUG=netjig export NETJIGTESTDEBUG</DT>
<DD> This will enable debugging of the communication with uml_netjig,
 and turn on debugging in this utility. This does not imply
 NETJIGVERBOSE.</DD>
</DL>
<DT> HOSTTESTDEBUG=hosttest export HOSTTESTDEBUG</DT>
<DD> This will show all interactions with the user-mode-linux consoles</DD>
</DL>
<H2 NAME="kernelpatch"><A NAME="20_11">kernel_patch_test paramaters</A></H2>
<P> The kernel_patch_test function takes some kernel source, copies it
 with lndir, and then applies the patch as produced by &quot;make
 kernelpatch&quot;.</P>
<P> The following are used to control the input and output to the
 system:</P>
<DL>
<DT>KERNEL_NAME</DT>
<DD>the kernel name, typically something like &quot;linus&quot; or &quot;rh&quot;</DD>
<DT>KERNEL_VERSION</DT>
<DD>the kernel version number, as in &quot;2.2&quot; or &quot;2.4&quot;.</DD>
<DT>KERNEL_${KERNEL_NAME}${KERNEL_VERSION}_SRC</DT>
<DD>This variable should set in the environment, probably in
 ~/freeswan-regress-env.sh. Examples of this variables would be
 KERNEL_LINUS2_0_SRC or KERNEL_RH7_3_SRC. This variable should point to
 an extracted copy of the kernel source in question.</DD>
<DT>REF_PATCH_OUTPUT</DT>
<DD>a copy of the patch output to compare against</DD>
<DT>KERNEL_PATCH_LEAVE_SOURCE</DT>
<DD>If set to a non-empty string, then the patched kernel source is not
 removed at the end of the test. This will typically be set in the
 environment while debugging.</DD>
</DL>
<H2 NAME="modtest"><A NAME="20_12">module_compile paramaters</A></H2>
<P> The module_compile test attempts to build the KLIPS module against a
 given set of kernel source. This is also done by the RPM tests, but in
 a very specific manner.</P>
<P> There are two variations of this test - one where the kernel either
 doesn't need to be configured, or is already done, and tests were there
 is a local configuration file.</P>
<P> Where the kernel doesn't need to be configured, the kernel source
 that is found is simply used. It may be a RedHat-style kernel, where
 one can cause it to configure itself via rhconfig.h-style definitions.
 Or, it may just be a kernel tree that has been configured.</P>
<P> If the variable KERNEL_CONFIG_FILE is set, then a new directory is
 created for the kernel source. It is populated with lndir(1). The
 referenced file is then copied in as .config, and &quot;make oldconfig&quot; is
 used to configure the kernel. This resulting kernel is then used as the
 reference source.</P>
<P> In all cases, the kernel source is found the same was for the
 kernelpatch test, i.e. via KERNEL_VERSION/KERNEL_NAME and
 KERNEL_${KERNEL_NAME}${KERNEL_VERSION}_SRC.</P>
<P> Once there is kernel source, the module is compiled using the
 top-level &quot;make module&quot; target.</P>
<P> The test is considered successful if an executable is found in
 OUTPUT/module/ipsec.o at the end of the test.</P>
<DL>
<DT>KERNEL_NAME</DT>
<DD>the kernel name, typically something like &quot;linus&quot; or &quot;rh&quot;</DD>
<DT>KERNEL_VERSION</DT>
<DD>the kernel version number, as in &quot;2.2&quot; or &quot;2.4&quot;.</DD>
<DT>KERNEL_${KERNEL_NAME}${KERNEL_VERSION}_SRC</DT>
<DD>This variable should set in the environment, probably in
 ~/freeswan-regress-env.sh. Examples of this variables would be
 KERNEL_LINUS2_0_SRC or KERNEL_RH7_3_SRC. This variable should point to
 an extracted copy of the kernel source in question.</DD>
<DT>KERNEL_CONFIG_FILE</DT>
<DD>The configuration file for the kernel.</DD>
<DT>KERNEL_PATCH_LEAVE_SOURCE</DT>
<DD>If set to a non-empty string, then the configured kernel source is
 not removed at the end of the test. This will typically be set in the
 environment while debugging.</DD>
<DT>MODULE_DEF_INCLUDE</DT>
<DD>The include file that will be used to configure the KLIPS module,
 and possibly the kernel source.</DD>
</DL>
<H1><A NAME="21">Current pitfalls</A></H1>
<DL>
<DT> &quot;tcpdump dissector&quot; not available.</DT>
<DD> This is a non-fatal warning. If uml_netjig is invoked with the -t
 option, then it will attempt to use tcpdump's dissector to decode each
 packet that it processes. The dissector is presently not available, so
 this option it normally turned off at compile time. The dissector
 library will be released with tcpdump version 4.0.</DD>
</DL>
<HR>
<H1><A name="umltesting">User-Mode-Linux Testing guide</A></H1>
<P> User mode linux is a way to compile a linux kernel such that it can
 run as a process in another linux system (potentially as a *BSD or
 Windows process later). See<A HREF="http://user-mode-linux.sourceforge.net/">
 http://user-mode-linux.sourceforge.net/</A></P>
<P> UML is a good platform for testing and experimenting with FreeS/WAN.
 It allows several network nodes to be simulated on a single machine.
 Creating, configuring, installing, monitoring, and controling these
 nodes is generally easier and easier to script with UML than real
 hardware.</P>
<P> You'll need about 500Mb of disk space for a full
 sunrise-east-west-sunset setup. You can possibly get this down by 130Mb
 if you remove the sunrise/sunset kernel build. If you just want to run,
 then you can even remove the east/west kernel build.</P>
<P> Nothing need be done as super user. In a couple of steps, we note
 where super user is required to install commands in system-wide
 directories, but ~/bin could be used instead. UML seems to use a
 system-wide /tmp/uml directory so different users may interfere with
 one another. Later UMLs use ~/.uml instead, so multiple users running
 UML tests should not be a problem, but note that a single user running
 the UML tests will only be able run one set. Further, UMLs sometimes
 get stuck and hang around. These &quot;zombies&quot; (most will actually be in
 the &quot;T&quot; state in the process table) will interfere with subsequent
 tests.</P>
<H2><A NAME="22_1">Preliminary Notes on BIND</A></H2>
<P> As of 2003/3/1, the Light-Weight Resolver is used by pluto. This
 requires that BIND9 be running. It also requires that BIND9 development
 libraries be present in the build environment. The DNSSEC code is only
 truly functional in BIND9 snapshots. The library code could be 9.2.2,
 we believe. We are using BIND9 20021115 snapshot code from<A HREF="ftp://ftp.isc.org/isc/bind9/snapshots">
 ftp://ftp.isc.org/isc/bind9/snapshots</A>.</P>
<P> FreeS/WAN may well require a newer BIND than is on your system. Many
 distributions have moved to BIND9.2.2 recently due to a security
 advisory. BIND is five components.</P>
<OL>
<LI> named</LI>
<LI> dnssec-*</LI>
<LI> client side resolver libraries</LI>
<LI> client side utility libraries I thought there were lib and named
 parts to dnsssec...</LI>
<LI> dynamic DNS update utilities</LI>
</OL>
<P> The only piece that we need for *building* is #4. That's the only
 part that has to be on the build host. What is the difference between
 resolver and util libs? If you want to edit
 testing/baseconfigs/all/etc/bind, you'll need a snapshot version. The
 resolver library contains the resolver. FreeS/WAN has its own copy of
 that in lib/liblwres.</P>
<H2><A NAME="22_2">Steps to Install UML for FreeS/WAN</A></H2>
<OL>
<LI> Get the following files:
<OL type="a">
<LI> from<A HREF="http://www.sandelman.ottawa.on.ca/freeswan/uml/">
 http://www.sandelman.ottawa.on.ca/freeswan/uml/</A>
 umlfreeroot-15.1.tar.gz (or highest numbered one). This is a debian
 potato root file system. You can use this even on a Redhat host, as it
 has the newer GLIBC2.2 libraries as well.
<!-- If you are using
  Redhat 7.2 or newer as your development machine, you can create the
  image from your installation media. See <A HREF="uml-rhroot.html">Building a RedHat root"></A>.
  A future document will explain how to build this from .DEB files as well.
-->

<!--
<LI> umlfreesharemini.tar.gz    (or umlfreeshareall.tar.gz). 
  If you are a Debian potato user, you don't need it you can use your
  native /usr/share.
</UL>
-->
</LI>
<LI> From<A HREF="ftp://ftp.xs4all.nl/pub/crypto/freeswan/">
 ftp://ftp.xs4all.nl/pub/crypto/freeswan/</A> a snapshot or release
 (1.92 or better)</LI>
<LI> From a<A HREF="http://www.kernel.org/mirrors/">
 http://www.kernel.org mirror</A>, the virgin 2.4.19 kernel. Please
 realize that we have defaults in our tree for kernel configuration. We
 try to track the latest UML kernels. If you use a newer kernel, you may
 have faults in the kernel build process. You can see what the latest
 that is being regularly tested by visiting<A HREF="http://bugs.freeswan.org:81/regress/HEAD/lastgood/freeswan-regress-env.sh">
 freeswan-regress-env.sh</A>.</LI>
<LI>
<!-- Note: this step is refered to as "step 1d" below. -->
 Get<A HREF="http://ftp.nl.linux.org/uml/">
 http://ftp.nl.linux.org/uml/</A> uml-patch-2.4.19-47.bz2 or the one
 associated with your kernel. As of 2003/03/05, uml-patch-2.4.19-47.bz2
 works for us.<STRONG> More recent versions of the patch have not been
 tested by us.</STRONG></LI>
<LI> You'll probably want to visit<A HREF="http://user-mode-linux.sourceforge.net">
 http://user-mode-linux.sourceforge.net</A> and get the UML utilities.
 These are not needed for the build or interactive use (but
 recommended). They are necessary for the regression testing procedures
 used by &quot;make check&quot;. We currently use uml_utilities_20020212.tar.bz2.</LI>
<LI> You need tcpdump version 3.7.1 or better. This is newer than the
 version included in most LINUX distributions. You can check the version
 of an installed tcpdump with the --version flag. If you need a newer
 tcpdump fetch both tcpdump and libpcap source tar files from<A HREF="http://www.tcpdump.org/">
 http://www.tcpdump.org/</A> or a mirror.</LI>
</OL>
</LI>
<LI> Pick a suitable place, and extract the following files:
<OL type="a">
<LI>
<!-- Note: this step is refered to as "step 2a" later. -->
 2.4.19 kernel. For instance:
<PRE>
 <CODE>           cd /c2/kernel
           tar xzvf ../download/pub/linux/kernel/v2.4/linux-2.4.19.tar.gz
</CODE>
</PRE>
</LI>
<LI> extract the umlfreeroot file
<!-- (unless you <A HREF="uml-rhroot.html">built your own from RPMs</A>) -->

<PRE>
 <CODE>           mkdir -p /c2/user-mode-linux/basic-root
           cd /c2/user-mode-linux/basic-root
           tar xzvf ../download/umlfreeroot-15.1.tar.gz
</CODE>
</PRE>
</LI>
<LI> FreeSWAN itself (or checkout &quot;all&quot; from CVS)
<PRE>
 <CODE>           mkdir -p /c2/freeswan/sandbox
           cd /c2/freeswan/sandbox
           tar xzvf ../download/snapshot.tar.gz
</CODE>
</PRE>
</LI>
</OL>
</LI>
<LI> If you need to build a newer tcpdump:
<UL>
<LI> Make sure you have OpenSSL installed -- it is needed for
 cryptographic routines.</LI>
<LI> Unpack libpcap and tcpdump source in parallel directories (the
 tcpdump build procedures look for libpcap next door).</LI>
<LI> Change directory into the libpcap source directory and then build
 the library:
<PRE>
 <CODE>	./configure
	make
</CODE>
</PRE>
</LI>
<LI> Change into the tcpdump source directory, build tcpdump, and
 install it.
<PRE>
 <CODE>	./configure
	make
	# Need to be superuser to install in system directories.
	# Installing in ~/bin would be an alternative.
	su -c &quot;make install&quot;
</CODE>
</PRE>
</LI>
</UL>
</LI>
<LI> If you need the uml utilities, unpack them somewhere then build and
 install them:
<PRE>
 <CODE>	cd tools
	make all
	# Need to be superuser to install in system directories.
	# Installing in ~/bin would be an alternative.
	su -c &quot;make install BIN_DIR=/usr/local/bin&quot;
</CODE>
</PRE>
</LI>
<LI> set up the configuration file
<UL>
<LI> <CODE>cd /c2/freeswan/sandbox/freeswan-1.97/testing/utils</CODE></LI>
<LI> copy umlsetup-sample.sh to ../../umlsetup.sh: <CODE> cp
 umlsetup-sample.sh ../../umlsetup.sh</CODE></LI>
<LI> open up ../../umlsetup.sh in your favorite editor.</LI>
<LI> change POOLSPACE= to point to the place with at least 500Mb of
 disk. Best if it is on the same partition as the &quot;umlfreeroot&quot;
 extraction, as it will attempt to use hard links if possible to save
 disk space.</LI>
<LI> Set TESTINGROOT if you intend to run the script outside of the
 sandbox/snapshot/release directory. Otherwise, it will configure
 itself.</LI>
<LI> KERNPOOL should point to the directory with your 2.4.19 kernel
 tree. This tree should be unconfigured! This is the directory you used
 in step 2a.</LI>
<LI> UMLPATCH should point at the bz2 file you downloaded at 1d. If
 using a kernel that already includes the patch, set this to /dev/null.</LI>
<LI> FREESWANDIR should point at the directory where you unpacked the
 snapshot/release. Include the &quot;freeswan-snap2001sep16b&quot; or whatever in
 it. If you are running from CVS, then you point at the directory where
 top, klips, etc. are. The script will fix up the directory so that it
 can be used.</LI>
<LI> BASICROOT should be set to the directory used in 2b, or to the
 directory that you created with RPMs.</LI>
<LI> SHAREDIR should be set to the directory used in 2c, to /usr/share
 for Debian potato users, or to $BASICROOT/usr/share.</LI>
</UL>
</LI>
<LI>
<PRE> <CODE>cd $TESTINGROOT/utils
sh make-uml.sh
</CODE></PRE>
 It will grind for awhile. If there are errors it will bail. If so, run
 it under &quot;script&quot; and send the output to bugs@lists.freeswan.org.</LI>
<LI> You will have a bunch of stuff under $POOLSPACE. Open four xterms:
<PRE> <CODE>    for i in sunrise sunset east west
    do
        xterm -name $i -title $i -e $POOLSPACE/$i/start.sh     done
</CODE></PRE>
</LI>
<LI> Login as root. Password is &quot;root&quot; (Note, these virtual machines are
 networked together, but are not configured to talk to the rest of the
 world.)</LI>
<LI> verify that pluto started on east/west, run &quot;ipsec look&quot;</LI>
<LI> login to sunrise. run &quot;ping sunset&quot;</LI>
<LI> login to west. run &quot;tcpdump -p -i eth1 -n&quot; (tcpdump must be version
 3.7.1 or newer)</LI>
<LI> Closing a console xterm will shut down that UML.</LI>
<LI> You can &quot;make check&quot;, if you want to. It is run from
 /c2/freeswan/sandbox/freeswan-1.97.</LI>
</OL>
<H1><A NAME="23">Debugging the kernel with GDB</A></H1>
<P> With User-Mode-Linux, you can debug the kernel using GDB. See
<!--HREF="http://user-mode-linux.sourceforge.net/debugging.html"-->

 http://user-mode-linux.sourceforge.net/debugging.html.</(null)></P>
<P> Typically, one will want to address a test case for a failing
 situation. Running GDB from Emacs, or from other front ends is
 possible. First start GDB.</P>
<P> Tell it to open the UMLPOOL/swan/linux program.</P>
<P> Note the PID of GDB:</P>
<PRE>
marajade-[projects/freeswan/mgmt/planning] mcr 1029 %ps ax | grep gdb
 1659 pts/9    SN     0:00 /usr/bin/gdb -fullname -cd /mara4/freeswan/kernpatch/UMLPOOL/swan/ linux
</PRE>
<P> Set the following in the environment:</P>
<PRE>
UML_east_OPT=&quot;debug gdb-pid=1659&quot;
</PRE>
<P> Then start the user-mode-linux in the test scheme you wish:</P>
<PRE>
marajade-[kernpatch/testing/klips/east-icmp-02] mcr 1220 %../../utils/runme.sh
</PRE>
 The user-mode-linux will stop on boot, giving you a chance to attach to
 the process:
<PRE>
(gdb) file linux
Reading symbols from linux...done.
(gdb) attach 1
Attaching to program: /mara4/freeswan/kernpatch/UMLPOOL/swan/linux, process 1
0xa0118bc1 in kill () at hostfs_kern.c:770
</PRE>
<P> At this point, break points should be created as appropriate.</P>
<H2><A NAME="23_1">Other notes about debugging</A></H2>
<P> If you are running a standard test, after all the packets are sent,
 the UML will be shutdown. This can cause problems, because the UML may
 get terminated while you are debugging.</P>
<P> The environment variable <CODE>NETJIGWAITUSER</CODE> can be set to
 &quot;waituser&quot;. If so, then the testing system will prompt before exiting
 the test.</P>
<H1><A NAME="24">User-Mode-Linux mysteries</A></H1>
<UL>
<LI> running more than one UML of the same name (e.g. &quot;west&quot;) can cause
 problems.</LI>
<LI> running more than one UML from the same root file system is not a
 good idea.</LI>
<LI> all this means that running &quot;make check&quot; twice on the same machine
 is probably not a good idea.</LI>
<LI> occationally, UMLs will get stuck. This can happen like:
<!--BLOCK-->
 15134 ? T
 0:00 /spare/hugh/uml/uml2.4.18-sept5/umlbuild/east/linux (east)
 [/bin/sh] 15138 ? T 0:00
 /spare/hugh/uml/uml2.4.18-sept5/umlbuild/east/linux (east) [halt]</(null)>
 these will need to be killed. Note that they are in &quot;T&quot;racing mode.</LI>
<LI> UMLs can also hang, and will report &quot;Tracing myself and I can't get
 out&quot;. This is a bug in UML. There are ways to find out what is going on
 and report this to the UML people, but we don't know the magic right
 now.</LI>
</UL>
<H1><A NAME="25">Getting more info from uml_netjig</A></H1>
<P> uml_netjig can be compiled with a built-in tcpdump. This uses
 not-yet-released code from<A HREF="http://www.tcpdump.org/">
 www.tcpdump.org</A>. Please see the instructions in <CODE>
testing/utils/uml_netjig/Makefile</CODE>.</P>
<HR>
<H1><A name="politics">History and politics of cryptography</A></H1>
<P>Cryptography has a long and interesting history, and has been the
 subject of considerable political controversy.</P>
<H2><A name="intro.politics">Introduction</A></H2>
<H3><A NAME="26_1_1">History</A></H3>
<P>The classic book on the history of cryptography is David Kahn's<A href="#Kahn">
 The Codebreakers</A>. It traces codes and codebreaking from ancient
 Egypt to the 20th century.</P>
<P>Diffie and Landau<A href="#diffie"> Privacy on the Line: The Politics
 of Wiretapping and Encryption</A> covers the history from the First
 World War to the 1990s, with an emphasis on the US.</P>
<H4><A NAME="26_1_1_1">World War II</A></H4>
<P>During the Second World War, the British &quot;Ultra&quot; project achieved one
 of the greatest intelligence triumphs in the history of warfare,
 breaking many Axis codes. One major target was the Enigma cipher
 machine, a German device whose users were convinced it was unbreakable.
 The American &quot;Magic&quot; project had some similar triumphs against Japanese
 codes.</P>
<P>There are many books on this period. See our bibliography for
 several. Two I particularly like are:</P>
<UL>
<LI>Andrew Hodges has done a superb<A href="http://www.turing.org.uk/book/">
 biography</A> of Alan Turing, a key player among the Ultra
 codebreakers. Turing was also an important computer pioneer. The terms<A
href="http://www.abelard.org/turpap/turpap.htm"> Turing test</A> and<A href="http://plato.stanford.edu/entries/turing-machine/">
 Turing machine</A> are named for him, as is the<A href="http://www.acm.org">
 ACM</A>'s highest technical<A href="http://www.acm.org/awards/taward.html">
 award</A>.</LI>
<LI>Neal Stephenson's<A href="#neal"> Cryptonomicon</A> is a novel with
 cryptography central to the plot. Parts of it take place during WW II,
 other parts today.</LI>
</UL>
<P>Bletchley Park, where much of the Ultra work was done, now has a
 museum and a<A href="http://www.bletchleypark.org.uk/"> web site</A>.</P>
<P>The Ultra work introduced three major innovations.</P>
<UL>
<LI>The first break of Enigma was achieved by Polish Intelligence in
 1931. Until then most code-breakers had been linguists, but a different
 approach was needed to break machine ciphers. Polish Intelligence
 recruited bright young mathematicians to crack the &quot;unbreakable&quot;
 Enigma. When war came in 1939, the Poles told their allies about this,
 putting Britain on the road to Ultra. The British also adopted a
 mathematical approach.</LI>
<LI>Machines were extensively used in the attacks. First the Polish
 &quot;Bombe&quot; for attacking Enigma, then British versions of it, then
 machines such as Collosus for attacking other codes. By the end of the
 war, some of these machines were beginning to closely resemble digital
 computers. After the war, a team at Manchester University, several old
 Ultra hands included, built one of the world's first actual
 general-purpose digital computers.</LI>
<LI>Ultra made codebreaking a large-scale enterprise, producing
 intelligence on an industrial scale. This was not a &quot;black chamber&quot;,
 not a hidden room in some obscure government building with a small crew
 of code-breakers. The whole operation -- from wholesale interception of
 enemy communications by stations around the world, through large-scale
 code-breaking and analysis of the decrypted material (with an enormous
 set of files for cross-referencing), to delivery of intelligence to
 field commanders -- was huge, and very carefully managed.</LI>
</UL>
<P>So by the end of the war, Allied code-breakers were expert at
 large-scale mechanised code-breaking. The payoffs were enormous.</P>
<H4><A name="postwar">Postwar and Cold War</A></H4>
<P>The wartime innovations were enthusiastically adopted by post-war and
 Cold War signals intelligence agencies. Presumably many nations now
 have some agency capable of sophisticated attacks on communications
 security, and quite a few engage in such activity on a large scale.</P>
<P>America's<A href="#NSA"> NSA</A>, for example, is said to be both the
 world's largest employer of mathematicians and the world's largest
 purchaser of computer equipment. Such claims may be somewhat
 exaggerated, but beyond doubt the NSA -- and similar agencies in other
 countries -- have some excellent mathematicians, lots of powerful
 computers, sophisticated software, and the organisation and funding to
 apply them on a large scale. Details of the NSA budget are secret, but
 there are some published<A href="http://www.fas.org/irp/nsa/nsabudget.html">
 estimates</A>.</P>
<P>Changes in the world's communications systems since WW II have
 provided these agencies with new targets. Cracking the codes used on an
 enemy's military or diplomatic communications has been common practice
 for centuries. Extensive use of radio in war made large-scale attacks
 such as Ultra possible. Modern communications make it possible to go
 far beyond that. Consider listening in on cell phones, or intercepting
 electronic mail, or tapping into the huge volumes of data on new media
 such as fiber optics or satellite links. None of these targets existed
 in 1950. All of them can be attacked today, and almost certainly are
 being attacked.</P>
<P>The Ultra story was not made public until the 1970s. Much of the
 recent history of codes and code-breaking has not been made public, and
 some of it may never be. Two important books are:</P>
<UL>
<LI>Bamford's<A href="#puzzle"> The Puzzle Palace</A>, a history of the
 NSA</LI>
<LI>Hager's<A href="http://www.fas.org/irp/eprint/sp/index.html"> Secret
 Power</A>, about the<A href="http://sg.yahoo.com/government/intelligence/echelon_network/">
 Echelon</A> system -- the US, UK, Canada, Australia and New Zealand
 co-operating to monitor much of the world's communications.</LI>
</UL>
<P>Note that these books cover only part of what is actually going on,
 and then only the activities of nations open and democratic enough that
 (some of) what they are doing can be discovered. A full picture,
 including:</P>
<UL>
<LI>actions of the English-speaking democracies not covered in those
 books</LI>
<LI>actions of other more-or-less sane governments</LI>
<LI>the activities of various more-or-less insane governments</LI>
<LI>possibilities for unauthorized action by government employees</LI>
<LI>possible actions by large non-government organisations:
 corporations, criminals, or conspiracies</LI>
</UL>
<P>might be really frightening.</P>
<H4><A name="recent">Recent history -- the crypto wars</A></H4>
<P>Until quite recently, cryptography was primarily a concern of
 governments, especially of the military, of spies, and of diplomats.
 Much of it was extremely secret.</P>
<P>In recent years, that has changed a great deal. With computers and
 networking becoming ubiquitous, cryptography is now important to almost
 everyone. Among the developments since the 1970s:</P>
<UL>
<LI>The US gov't established the Data Encryption Standard,<A href="#DES">
 DES</A>, a<A href="#block"> block cipher</A> for cryptographic
 protection of unclassfied documents.</LI>
<LI>DES also became widely used in industry, especially regulated
 industries such as banking.</LI>
<LI>Other nations produced their own standards, such as<A href="glossary.html#GOST">
 GOST</A> in the Soviet Union.</LI>
<LI><A href="#public">Public key</A> cryptography was invented by Diffie
 and Hellman.</LI>
<LI>Academic conferences such as<A href="http://www-cse.ucsd.edu/users/mihir/crypto2k.html">
 Crypto</A> and<A href="http://www.esat.kuleuven.ac.be/cosic/eurocrypt2000/">
 Eurocrypt</A> began.</LI>
<LI>Several companies began offerring cryptographic products:<A href="#RSAco">
 RSA</A>,<A href="#PGPI"> PGP</A>, the many vendors with<A href="#PKI">
 PKI</A> products, ...</LI>
<LI>Cryptography appeared in other products: operating systems, word
 processors, ...</LI>
<LI>Network protocols based on crypto were developed:<A href="#ssh"> SSH</A>
,<A href="#SSL"> SSL</A>,<A href="#IPSEC"> IPsec</A>, ...</LI>
<LI>Crytography came into widespread use to secure bank cards,
 terminals, ...</LI>
<LI>The US government replaced<A href="#DES"> DES</A> with the much
 stronger Advanced Encryption Standard,<A href="#AES"> AES</A></LI>
</UL>
<P>This has led to a complex ongoing battle between various mainly
 government groups wanting to control the spread of crypto and various
 others, notably the computer industry and the<A href="http://online.offshore.com.ai/security/">
 cypherpunk</A> crypto advocates, wanting to encourage widespread use.</P>
<P>Steven Levy has written a fine history of much of this, called<A href="#crypto">
 Crypto: How the Code rebels Beat the Government -- Saving Privacy in
 the Digital Age</A>.</P>
<P>The FreeS/WAN project is to a large extent an outgrowth of cypherpunk
 ideas. Our reasons for doing the project can be seen in these quotes
 from the<A href="http://www.eff.org/pub/Privacy/Crypto_misc/cypherpunk.manifesto">
 Cypherpunk Manifesto</A>:</P>
<BLOCKQUOTE> Privacy is necessary for an open society in the electronic
 age. ...
<P>We cannot expect governments, corporations, or other large, faceless
 organizations to grant us privacy out of their beneficence. It is to
 their advantage to speak of us, and we should expect that they will
 speak. ...</P>
<P>We must defend our own privacy if we expect to have any. ...</P>
<P>Cypherpunks write code. We know that someone has to write software to
 defend privacy, and since we can't get privacy unless we all do, we're
 going to write it. We publish our code so that our fellow Cypherpunks
 may practice and play with it. Our code is free for all to use,
 worldwide. We don't much care if you don't approve of the software we
 write. We know that software can't be destroyed and that a widely
 dispersed system can't be shut down.</P>
<P>Cypherpunks deplore regulations on cryptography, for encryption is
 fundamentally a private act. ...</P>
<P>For privacy to be widespread it must be part of a social contract.
 People must come and together deploy these systems for the common good.
 ...</P>
</BLOCKQUOTE>
<P>To quote project leader John Gilmore:</P>
<BLOCKQUOTE> We are literally in a race between our ability to build and
 deploy technology, and their ability to build and deploy laws and
 treaties. Neither side is likely to back down or wise up until it has
 definitively lost the race.</BLOCKQUOTE>
<P>If FreeS/WAN reaches its goal of making<A href="#opp.intro">
 opportunistic encryption</A> widespread so that secure communication
 can become the default for a large part of the net, we will have struck
 a major blow.</P>
<H3><A name="intro.poli">Politics</A></H3>
<P>The political problem is that nearly all governments want to monitor
 their enemies' communications, and some want to monitor their citizens.
 They may be very interested in protecting some of their own
 communications, and often some types of business communication, but not
 in having everyone able to communicate securely. They therefore attempt
 to restrict availability of strong cryptography as much as possible.</P>
<P>Things various governments have tried or are trying include:</P>
<UL>
<LI>Echelon, a monitor-the-world project of the US, UK, NZ, Australian
 and Canadian<A href="#SIGINT"> signals intelligence</A> agencies. See
 this<A href="http://sg.yahoo.com/government/intelligence/echelon_network/">
 collection</A> of links and this<A href="http://www.zdnet.com/zdnn/stories/news/0,4586,2640682,00.html">
 story</A> on the French Parliament's reaction.</LI>
<LI>Others governments may well have their own Echelon-like projects. To
 quote the Dutch Minister of Defense, as reported in a German<A href="http://www.heise.de/tp/english/inhalt/te/4729/1.html">
 magazine</A>:<BLOCKQUOTE> The government believes not only the
 governments associated with Echelon are able to intercept communication
 systems, but that it is an activity of the investigative authorities
 and intelligence services of many countries with governments of
 different political signature.</BLOCKQUOTE> Even if they have nothing
 on the scale of Echelon, most intelligence agencies and police forces
 certainly have some interception capability.</LI>
<LI><A href="#NSA">NSA</A> tapping of submarine communication cables,
 described in<A href="http://www.zdnet.com/zdnn/stories/news/0,4586,2764372,00.html">
 this article</A></LI>
<LI>A proposal for international co-operation on<A href="http://www.heise.de/tp/english/special/enfo/4306/1.html">
 Internet surveillance</A>.</LI>
<LI>Alleged<A href="http://cryptome.org/nsa-sabotage.htm"> sabotage</A>
 of security products by the<A href="#NSA"> NSA</A> (the US signals
 intelligence agency).</LI>
<LI>The German armed forces and some government departments will stop
 using American software for fear of NSA &quot;back doors&quot;, according to this<A
href="http://www.theregister.co.uk/content/4/17679.html"> news story</A>
.</LI>
<LI>The British Regulation of Investigatory Powers bill. See this<A href="http://www.fipr.org/rip/index.html">
 web page.</A> and perhaps this<A href="http://ars.userfriendly.org/cartoons/?id=20000806&amp;mode=classic">
 cartoon</A>.</LI>
<LI>A Russian<A href="http://www.eff.org/pub/Privacy/Foreign_and_local/Russia/russian_crypto_ban_english.edict">
 ban</A> on cryptography</LI>
<LI>Chinese<A href="http://www.eff.org/pub/Misc/Publications/Declan_McCullagh/www/global/china">
 controls</A> on net use.</LI>
<LI>The FBI's carnivore system for covert searches of email. See this<A href="http://www.zdnet.com/zdnn/stories/news/0,4586,2601502,00.html">
 news coverage</A> and this<A href="http://www.crypto.com/papers/carnivore-risks.html">
 risk assessment</A>. The government had an external review of some
 aspects of this system done. See this<A href="http://www.crypto.com/papers/carnivore_report_comments.html">
 analysis</A> of that review. Possible defenses against Carnivore
 include:
<UL>
<LI><A href="#PGP">PGP</A> for end-to-end mail encryption</LI>
<LI><A href="http://www.home.aone.net.au/qualcomm/">secure sendmail</A>
 for server-to-server encryption</LI>
<LI>IPsec encryption on the underlying IP network</LI>
</UL>
</LI>
<LI>export laws restricting strong cryptography as a munition. See<A href="#exlaw">
 discussion</A> below.</LI>
<LI>various attempts to convince people that fundamentally flawed
 cryptography, such as encryption with a<A href="#escrow"> back door</A>
 for government access to data or with<A href="#shortkeys"> inadequate
 key lengths</A>, was adequate for their needs.</LI>
</UL>
<P>Of course governments are by no means the only threat to privacy and
 security on the net. Other threats include:</P>
<UL>
<LI>industrial espionage, as for example in this<A href="http://www.zdnet.com/zdnn/stories/news/0,4586,2626931,00.html">
 news story</A></LI>
<LI>attacks by organised criminals, as in this<A href="http://www.sans.org/newlook/alerts/NTE-bank.htm">
 large-scale attack</A></LI>
<LI>collection of personal data by various companies.
<UL>
<LI>for example, consider the various corporate winners of Privacy
 International's<A href="http://www.privacyinternational.org/bigbrother/">
 Big Brother Awards</A>.</LI>
<LI><A href="http://www.zeroknowledge.com">Zero Knowledge</A> sell tools
 to defend against this</LI>
</UL>
</LI>
<LI>individuals may also be a threat in a variety of ways and for a
 variety of reasons</LI>
<LI>in particular, an individual with access to government or industry
 data collections could do considerable damage using that data in
 unauthorized ways.</LI>
</UL>
<P>One<A href="http://www.zdnet.com/zdnn/stories/news/0,4586,2640674,00.html">
 study</A> enumerates threats and possible responses for small and
 medium businesses. VPNs are a key part of the suggested strategy.</P>
<P>We consider privacy a human right. See the UN's<A href="http://www.un.org/Overview/rights.html">
 Universal Declaration of Human Rights</A>, article twelve:</P>
<BLOCKQUOTE> No one shall be subjected to arbitrary interference with
 his privacy, family, home or correspondence, nor to attacks upon his
 honor and reputation. Everyone has the right to the protection of the
 law against such interference or attacks.</BLOCKQUOTE>
<P>Our objective is to help make privacy possible on the Internet using
 cryptography strong enough not even those well-funded government
 agencies are likely to break it. If we can do that, the chances of
 anyone else breaking it are negliible.</P>
<H3><A NAME="26_1_3">Links</A></H3>
<P>Many groups are working in different ways to defend privacy on the
 net and elsewhere. Please consider contributing to one or more of these
 groups:</P>
<UL>
<LI>the EFF's<A href="http://www.eff.org/crypto/"> Privacy Now!</A>
 campaign</LI>
<LI>the<A href="http://www.gilc.org"> Global Internet Liberty Campaign</A>
</LI>
<LI><A href="http://www.cpsr.org/program/privacy/privacy.html">Computer
 Professionals for Social Responsibility</A></LI>
</UL>
<P>For more on these issues see:</P>
<UL>
<LI>Steven Levy (Newsweek's chief technology writer and author of the
 classic &quot;Hackers&quot;) new book<A href="#crypto"> Crypto: How the Code
 Rebels Beat the Government--Saving Privacy in the Digital Age</A></LI>
<LI>Simson Garfinkel (Boston Globe columnist and author of books on<A href="#PGP">
 PGP</A> and<A href="#practical"> Unix Security</A>) book<A href="#Garfinkel">
 Database Nation: the death of privacy in the 21st century</A></LI>
</UL>
<P>There are several collections of<A href="#quotes"> crypto quotes</A>
 on the net.</P>
<P>See also the<A href="biblio.html"> bibliography</A> and our list of<A href="#policy">
 web references</A> on cryptography law and policy.</P>
<H3><A NAME="26_1_4">Outline of this section</A></H3>
<P>The remainder of this section includes two pieces of writing by our
 project leader</P>
<UL>
<LI>his<A href="#gilmore"> rationale</A> for starting this</LI>
<LI>another<A href="#policestate"> discussion</A> of project goals</LI>
</UL>
<P>and discussions of:</P>
<UL>
<LI><A href="#desnotsecure">why we do not use DES</A></LI>
<LI><A href="#exlaw">cryptography export laws</A></LI>
<LI>why<A href="#escrow"> government access to keys</A> is not a good
 idea</LI>
<LI>the myth that<A href="#shortkeys"> short keys</A> are adequate for
 some security requirements</LI>
</UL>
<P>and a section on<A href="#press"> press coverage of FreeS/WAN</A>.</P>
<H2><A name="leader">From our project leader</A></H2>
<P>FreeS/WAN project founder John Gilmore wrote a web page about why we
 are doing this. The version below is slightly edited, to fit this
 format and to update some links. For a version without these edits, see
 his<A href="http://www.toad.com/gnu/"> home page</A>.</P>
<CENTER>
<H3><A name="gilmore">Swan: Securing the Internet against Wiretapping</A>
</H3>
</CENTER>
<P>My project for 1996 was to<B> secure 5% of the Internet traffic
 against passive wiretapping</B>. It didn't happen in 1996, so I'm still
 working on it in 1997, 1998, and 1999! If we get 5% in 1999 or 2000, we
 can secure 20% the next year, against both active and passive attacks;
 and 80% the following year. Soon the whole Internet will be private and
 secure. The project is called S/WAN or S/Wan or Swan for Secure Wide
 Area Network; since it's free software, we call it FreeSwan to
 distinguish it from various commercial implementations.<A href="http://www.rsa.com/rsa/SWAN/">
 RSA</A> came up with the term &quot;S/WAN&quot;. Our main web site is at<A href="http://www.freeswan.org/">
 http://www.freeswan.org/</A>. Want to help?</P>
<P>The idea is to deploy PC-based boxes that will sit between your local
 area network and the Internet (near your firewall or router) which
 opportunistically encrypt your Internet packets. Whenever you talk to a
 machine (like a Web site) that doesn't support encryption, your traffic
 goes out &quot;in the clear&quot; as usual. Whenever you connect to a machine
 that does support this kind of encryption, this box automatically
 encrypts all your packets, and decrypts the ones that come in. In
 effect, each packet gets put into an &quot;envelope&quot; on one side of the net,
 and removed from the envelope when it reaches its destination. This
 works for all kinds of Internet traffic, including Web access, Telnet,
 FTP, email, IRC, Usenet, etc.</P>
<P>The encryption boxes are standard PC's that use freely available
 Linux software that you can download over the Internet or install from
 a cheap CDROM.</P>
<P>This wasn't just my idea; lots of people have been working on it for
 years. The encryption protocols for these boxes are called<A href="#IPSEC">
 IPSEC (IP Security)</A>. They have been developed by the<A href="http://www.ietf.cnri.reston.va.us/html.charters/ipsec-charter.html">
 IP Security Working Group</A> of the<A href="http://www.ietf.org/">
 Internet Engineering Task Force</A>, and will be a standard part of the
 next major version of the Internet protocols (<A href="http://playground.sun.com/pub/ipng/html/ipng-main.html">
IPv6</A>). For today's (IP version 4) Internet, they are an option.</P>
<P>The<A href="http://www.iab.org/iab"> Internet Architecture Board</A>
 and<A href="http://www.ietf.org/"> Internet Engineering Steering Group</A>
 have taken a<A href="iab-iesg.stmt"> strong stand</A> that the Internet
 should use powerful encryption to provide security and privacy. I think
 these protocols are the best chance to do that, because they can be
 deployed very easily, without changing your hardware or software or
 retraining your users. They offer the best security we know how to
 build, using the Triple-DES, RSA, and Diffie-Hellman algorithms.</P>
<P>This &quot;opportunistic encryption box&quot; offers the &quot;fax effect&quot;. As each
 person installs one for their own use, it becomes more valuable for
 their neighbors to install one too, because there's one more person to
 use it with. The software automatically notices each newly installed
 box, and doesn't require a network administrator to reconfigure it.
 Instead of &quot;virtual private networks&quot; we have a &quot;REAL private network&quot;;
 we add privacy to the real network instead of layering a
 manually-maintained virtual network on top of an insecure Internet.</P>
<H4><A NAME="26_2_1_1">Deployment of IPSEC</A></H4>
<P>The US government would like to control the deployment of IP Security
 with its<A href="#exlaw"> crypto export laws</A>. This isn't a problem
 for my effort, because the cryptographic work is happening outside the
 United States. A foreign philanthropist, and others, have donated the
 resources required to add these protocols to the Linux operating
 system.<A href="http://www.linux.org/"> Linux</A> is a complete, freely
 available operating system for IBM PC's and several kinds of
 workstation, which is compatible with Unix. It was written by Linus
 Torvalds, and is still maintained by a talented team of expert
 programmers working all over the world and coordinating over the
 Internet. Linux is distributed under the<A href="#GPL"> GNU Public
 License</A>, which gives everyone the right to copy it, improve it,
 give it to their friends, sell it commercially, or do just about
 anything else with it, without paying anyone for the privilege.</P>
<P>Organizations that want to secure their network will be able to put
 two Ethernet cards into an IBM PC, install Linux on it from a $30 CDROM
 or by downloading it over the net, and plug it in between their
 Ethernet and their Internet link or firewall. That's all they'll have
 to do to encrypt their Internet traffic everywhere outside their own
 local area network.</P>
<P>Travelers will be able to run Linux on their laptops, to secure their
 connection back to their home network (and to everywhere else that they
 connect to, such as customer sites). Anyone who runs Linux on a
 standalone PC will also be able to secure their network connections,
 without changing their application software or how they operate their
 computer from day to day.</P>
<P>There will also be numerous commercially available firewalls that use
 this technology.<A href="http://www.rsa.com/"> RSA Data Security</A> is
 coordinating the<A href="http://www.rsa.com/rsa/SWAN"> S/Wan (Secure
 Wide Area Network)</A> project among more than a dozen vendors who use
 these protocols. There's a<A href="http://www.rsa.com/rsa/SWAN/swan_test.htm">
 compatability chart</A> that shows which vendors have tested their
 boxes against which other vendors to guarantee interoperatility.</P>
<P>Eventually it will also move into the operating systems and
 networking protocol stacks of major vendors. This will probably take
 longer, because those vendors will have to figure out what they want to
 do about the export controls.</P>
<H4><A NAME="26_2_1_2">Current status</A></H4>
<P>My initial goal of securing 5% of the net by Christmas '96 was not
 met. It was an ambitious goal, and inspired me and others to work hard,
 but was ultimately too ambitious. The protocols were in an early stage
 of development, and needed a lot more protocol design before they could
 be implemented. As of April 1999, we have released version 1.0 of the
 software (<A href="ftp://ftp.xs4all.nl/freeswan/freeswan-1.0.tar.gz">
freeswan-1.0.tar.gz</A>), which is suitable for setting up Virtual
 Private Networks using shared secrets for authentication. It does not
 yet do opportunistic encryption, or use DNSSEC for authentication;
 those features are coming in a future release.</P>
<DL>
<DT>Protocols</DT>
<DD>The low-level encrypted packet formats are defined. The system for
 publishing keys and providing secure domain name service is defined.
 The IP Security working group has settled on an NSA-sponsored protocol
 for key agreement (called ISAKMP/Oakley), but it is still being worked
 on, as the protocol and its documentation is too complex and
 incomplete. There are prototype implementations of ISAKMP. The protocol
 is not yet defined to enable opportunistic encryption or the use of
 DNSSEC keys.</DD>
<DT>Linux Implementation</DT>
<DD>The Linux implementation has reached its first major release and is
 ready for production use in manually-configured networks, using Linux
 kernel version 2.0.36.</DD>
<DT>Domain Name System Security</DT>
<DD>There is now a release of BIND 8.2 that includes most DNS Security
 features.
<P>The first prototype implementation of Domain Name System Security was
 funded by<A href="#DARPA"> DARPA</A> as part of their<A href="http://www.darpa.mil/ito/research/is/index.html">
 Information Survivability program</A>.<A href="http://www.tis.com">
 Trusted Information Systems</A> wrote a modified version of<A href="http://www.isc.org/bind.html">
 BIND</A>, the widely-used Berkeley implementation of the Domain Name
 System.</P>
<P>TIS, ISC, and I merged the prototype into the standard version of
 BIND. The first production version that supports KEY and SIG records is<B>
 bind-4.9.5</B>. This or any later version of BIND will do for
 publishing keys. It is available from the<A href="http://www.isc.org/bind.html">
 Internet Software Consortium</A>. This version of BIND is not
 export-controlled since it does not contain any cryptography. Later
 releases starting with BIND 8.2 include cryptography for authenticating
 DNS records, which is also exportable. Better documentation is needed.</P>
</DD>
</DL>
<H4><A NAME="26_2_1_3">Why?</A></H4>
<P>Because I can. I have made enough money from several successful
 startup companies, that for a while I don't have to work to support
 myself. I spend my energies and money creating the kind of world that
 I'd like to live in and that I'd like my (future) kids to live in.
 Keeping and improving on the civil rights we have in the United States,
 as we move more of our lives into cyberspace, is a particular goal of
 mine.</P>
<H4><A NAME="26_2_1_4">What You Can Do</A></H4>
<DL>
<DT>Install the latest BIND at your site.</DT>
<DD>You won't be able to publish any keys for your domain, until you
 have upgraded your copy of BIND. The thing you really need from it is
 the new version of<I> named</I>, the Name Daemon, which knows about the
 new KEY and SIG record types. So, download it from the<A href="http://www.isc.org/bind.html">
 Internet Software Consortium</A> and install it on your name server
 machine (or get your system administrator, or Internet Service
 Provider, to install it). Both your primary DNS site and all of your
 secondary DNS sites will need the new release before you will be able
 to publish your keys. You can tell which sites this is by running the
 Unix command &quot;dig MYDOMAIN ns&quot; and seeing which sites are mentioned in
 your NS (name server) records.</DD>
<DT>Set up a Linux system and run a 2.0.x kernel on it</DT>
<DD>Get a machine running Linux (say the 5.2 release from<A href="http://www.redhat.com">
 Red Hat</A>). Give the machine two Ethernet cards.</DD>
<DT>Install the Linux IPSEC (Freeswan) software</DT>
<DD>If you're an experienced sysadmin or Linux hacker, install the
 freeswan-1.0 release, or any later release or snapshot. These releases
 do NOT provide automated &quot;opportunistic&quot; operation; they must be
 manually configured for each site you wish to encrypt with.</DD>
<DT>Get on the linux-ipsec mailing list</DT>
<DD>The discussion forum for people working on the project, and testing
 the code and documentation, is: linux-ipsec@clinet.fi. To join this
 mailing list, send email to<A href="mailto:linux-ipsec-REQUEST@clinet.fi">
 linux-ipsec-REQUEST@clinet.fi</A> containing a line of text that says
 &quot;subscribe linux-ipsec&quot;. (You can later get off the mailing list the
 same way -- just send &quot;unsubscribe linux-ipsec&quot;).</DD>
<P></P>
<DT>Check back at this web page every once in a while</DT>
<DD>I update this page periodically, and there may be new information in
 it that you haven't seen. My intent is to send email to the mailing
 list when I update the page in any significant way, so subscribing to
 the list is an alternative.</DD>
</DL>
<P>Would you like to help? I can use people who are willing to write
 documentation, install early releases for testing, write cryptographic
 code outside the United States, sell pre-packaged software or systems
 including this technology, and teach classes for network administrators
 who want to install this technology. To offer to help, send me email at
 gnu@toad.com. Tell me what country you live in and what your
 citizenship is (it matters due to the export control laws; personally I
 don't care). Include a copy of your resume and the URL of your home
 page. Describe what you'd like to do for the project, and what you're
 uniquely qualified for. Mention what other volunteer projects you've
 been involved in (and how they worked out). Helping out will require
 that you be able to commit to doing particular things, meet your
 commitments, and be responsive by email. Volunteer projects just don't
 work without those things.</P>
<H4><A NAME="26_2_1_5">Related projects</A></H4>
<DL>
<DT>IPSEC for NetBSD</DT>
<DD>This prototype implementation of the IP Security protocols is for
 another free operating system.<A href="ftp://ftp.funet.fi/pub/unix/security/net/ip/BSDipsec.tar.gz">
 Download BSDipsec.tar.gz</A>.</DD>
<DT>IPSEC for<A href="http://www.openbsd.org"> OpenBSD</A></DT>
<DD>This prototype implementation of the IP Security protocols is for
 yet another free operating system. It is directly integrated into the
 OS release, since the OS is maintained in Canada, which has freedom of
 speech in software.</DD>
</DL>
<H3><A name="policestate">Stopping wholesale monitoring</A></H3>
<P>From a message project leader John Gilmore posted to the mailing
 list:</P>
<PRE>John Denker wrote:

&gt; Indeed there are several ways in which the documentation overstates the 
&gt; scope of what this project does -- starting with the name 
&gt; FreeS/WAN.  There's a big difference between having an encrypted IP tunnel 
&gt; versus having a Secure Wide-Area Network.  This software does a fine job of 
&gt; the former, which is necessary but not sufficient for the latter.

The goal of the project is to make it very hard to tap your wide area
communications.  The current system provides very good protection
against passive attacks (wiretapping and those big antenna farms).
Active attacks, which involve the intruder sending packets to your
system (like packets that break into sendmail and give them a root
shell :-) are much harder to guard against.  Active attacks that
involve sending people (breaking into your house and replacing parts
of your computer with ones that transmit what you're doing) are also
much harder to guard against.  Though we are putting effort into
protecting against active attacks, it's a much bigger job than merely
providing strong encryption.  It involves general computer security,
and general physical security, which are two very expensive problems
for even a site to solve, let alone to build into a whole society.

The societal benefit of building an infrastructure that protects
well against passive attacks is that it makes it much harder to do
undetected bulk monitoring of the population.  It's a defense against
police-states, not against policemen.

Policemen can put in the effort required to actively attack sites that
they have strong suspicions about.  But police states won't be able to
build systems that automatically monitor everyone's communications.
Either they will be able to monitor only a small subset of the
populace (by targeting those who screwed up their passive security),
or their monitoring activities will be detectable by those monitored
(active attacks leave packet traces or footprints), which can then be
addressed through the press and through political means if they become
too widespread.

FreeS/WAN does not protect very well against traffic analysis, which
is a kind of widespread police-state style monitoring that still
reveals significant information (who's talking to who) without
revealing the contents of what was said.  Defenses against traffic
analysis are an open research problem.  Zero Knowledge Systems is
actively deploying a system designed to thwart it, designed by Ian
Goldberg.  The jury is out on whether it actually works; a lot more
experience with it will be needed.</PRE>
<P>Notes on things mentioned in that message:</P>
<UL>
<LI>Denker is a co-author of a<A href="#applied"> paper</A> on a large
 FreeS/WAN application.</LI>
<LI>Information on Zero Knowledge is on their<A href="http://www.zks.net/">
 web site</A>. Their Freedom product, designed to provide untracable
 pseudonyms for use on the net, is no longer marketed.</LI>
<LI>Another section of our documentation discusses ways to<A href="#traffic.resist">
 resist traffic analysis</A>.</LI>
</UL>
<H2><A name="weak">Government promotion of weak crypto</A></H2>
<P>Various groups, especially governments and especially the US
 government, have a long history of advocating various forms of bogus
 security.</P>
<P>We regard bogus security as extremely dangerous. If users are
 deceived into relying on bogus security, then they may be exposed to
 large risks. They would be better off having no security and knowing
 it. At least then they would be careful about what they said.</P>
<P><STRONG>Avoiding bogus security is a key design criterion for
 everything we do in FreeS/WAN</STRONG>. The most conspicuous example is
 our refusal to support<A href="#desnotsecure"> single DES</A>. Other
 IPsec &quot;features&quot; which we do not implement are discussed in our<A href="#dropped">
 compatibility</A> document.</P>
<H3><A name="escrow">Escrowed encryption</A></H3>
<P>Various governments have made persistent attempts to encourage or
 mandate &quot;escrowed encrytion&quot;, also called &quot;key recovery&quot;, or GAK for
 &quot;government access to keys&quot;. The idea is that cryptographic keys be
 held by some third party and turned over to law enforcement or security
 agencies under some conditions.</P>
<PRE>  Mary had a little key - she kept it in escrow,
  and every thing that Mary said,
  the feds were sure to know.</PRE>
<P>A<A href="#quotes"> crypto quotes</A> page attributes this to<A href="http://www.scramdisk.clara.net/">
 Sam Simpson</A>.</P>
<P>There is an excellent paper available on<A href="http://www.cdt.org/crypto/risks98/">
 Risks of Escrowed Encryption</A>, from a group of cryptographic
 luminaries which included our project leader.</P>
<P>Like any unnecessary complication, GAK tends to weaken security of
 any design it infects. For example:</P>
<UL>
<LI>Matt Blaze found a fatal flaw in the US government's Clipper chip
 shortly after design information became public. See his paper &quot;Protocol
 Failure in the Escrowed Encryption Standard&quot; on his<A href="http://www.crypto.com/papers/">
 papers</A> page.</LI>
<LI>a rather<A href="http://www.pgp.com/other/advisories/adk.asp"> nasty
 bug</A> was found in the &quot;additional decryption keys&quot; &quot;feature&quot; of some
 releases of<A href="#PGP"> PGP</A></LI>
</UL>
<P>FreeS/WAN does not support escrowed encryption, and never will.</P>
<H3><A name="shortkeys">Limited key lengths</A></H3>
<P>Various governments, and some vendors, have also made persistent
 attempts to convince people that:</P>
<UL>
<LI>weak systems are sufficient for some data</LI>
<LI>strong cryptography should be reserved for cases where the extra
 overheads are justified</LI>
</UL>
<P><STRONG>This is utter nonsense</STRONG>.</P>
<P>Weak systems touted include:</P>
<UL>
<LI>the ludicrously weak (deliberately crippled) 40-bit ciphers that
 until recently were all various<A href="#exlaw"> export laws</A>
 allowed</LI>
<LI>56-bit single DES, discussed<A href="#desnotsecure"> below</A></LI>
<LI>64-bit symmetric ciphers and 512-bit RSA, the maximums for
 unrestricted export under various current laws</LI>
</UL>
<P>The notion that choice of ciphers or keysize should be determined by
 a trade-off between security requirements and overheads is pure
 bafflegab.</P>
<UL>
<LI>For most<A href="#symmetric"> symmetric ciphers</A>, it is simply a
 lie. Any block cipher has some natural maximum keysize inherent in the
 design -- 128 bits for<A href="#IDEA"> IDEA</A> or<A href="#CAST128">
 CAST-128</A>, 256 for Serpent or Twofish, 448 for<A href="#Blowfish">
 Blowfish</A> and 2048 for<A href="#RC4"> RC4</A>. Using a key size
 smaller than that limit gives<EM> exactly zero</EM> savings in
 overhead. The crippled 40-bit or 64-bit version of the cipher provides<EM>
 no advantage whatsoever</EM>.</LI>
<LI><A href="#AES">AES</A> uses 10 rounds with 128-bit keys, 12 rounds
 for 192-bit and 14 rounds for 256-bit, so there actually is a small
 difference in overhead, but not enough to matter in most applications.</LI>
<LI>For<A href="#3DES"> triple DES</A> there is a grain of truth in the
 argument. 3DES is indeed three times slower than single DES. However,
 the solution is not to use the insecure single DES, but to pick a
 faster secure cipher.<A href="#CAST128"> CAST-128</A>,<A href="#Blowfish">
 Blowfish</A> and the<A href="#AES"> AES candidate</A> ciphers are are
 all considerably faster in software than DES (let alone 3DES!), and
 apparently secure.</LI>
<LI>For<A href="#public"> public key</A> techniques, there are extra
 overheads for larger keys, but they generally do not affect overall
 performance significantly. Practical public key applications are
 usually<A href="#hybrid"> hybrid</A> systems in which the bulk of the
 work is done by a symmetric cipher. The effect of increasing the cost
 of the public key operations is typically negligible because the public
 key operations use only a tiny fraction of total resources.
<P>For example, suppose public key operations use use 1% of the time in
 a hybrid system and you triple the cost of public key operations. The
 cost of symmetric cipher operations is unchanged at 99% of the original
 total cost, so the overall effect is a jump from 99 + 1 = 100 to 99 + 3
 = 102, a 2% rise in system cost.</P>
</LI>
</UL>
<P>In short,<STRONG> there has never been any technical reason to use
 inadequate ciphers</STRONG>. The only reason there has ever been for
 anyone to use such ciphers is that government agencies want weak
 ciphers used so that they can crack them. The alleged savings are
 simply propaganda.</P>
<PRE>   Mary had a little key (It's all she could export),
   and all the email that she sent was opened at the Fort.</PRE>
<P>A<A href="#quotes"> crypto quotes</A> page attributes this to<A href="http://theory.lcs.mit.edu:80/~rivest/">
 Ron Rivest</A>. NSA headquarters is at Fort Meade, Maryland.</P>
<P>Our policy in FreeS/WAN is to use only cryptographic components with
 adequate keylength and no known weaknesses.</P>
<UL>
<LI>We do not implement single DES because it is clearly<A href="#desnotsecure">
 insecure</A>, so implemeting it would violate our policy of avoiding
 bogus security. Our default cipher is<A href="#3DES"> 3DES</A></LI>
<LI>Similarly, we do not implement the 768-bit Group 1 for<A href="#DH">
 Diffie-Hellman</A> key negotiation. We provide only the 1024-bit Group
 2 and 1536-bit Group 5.</LI>
</UL>
<P>Detailed discussion of which IPsec features we implement or omit is
 in out<A href="compat.html"> compatibility document</A>.</P>
<P>These decisions imply that we cannot fully conform to the IPsec RFCs,
 since those have DES as the only required cipher and Group 1 as the
 only required DH group. (In our view, the standards were subverted into
 offerring bogus security.) Fortunately, we can still interoperate with
 most other IPsec implementations since nearly all implementers provide
 at least 3DES and Group 2 as well.</P>
<P>We hope that eventually the RFCs will catch up with our (and others')
 current practice and reject dubious components. Some of our team and a
 number of others are working on this in<A href="#ietf"> IETF</A>
 working groups.</P>
<H4><A NAME="26_3_2_1">Some real trade-offs</A></H4>
<P>Of course, making systems secure does involve costs, and trade-offs
 can be made between cost and security. However, the real trade-offs
 have nothing to do with using weaker ciphers.</P>
<P>There can be substantial hardware and software costs. There are often
 substantial training costs, both to train administrators and to
 increase user awareness of security issues and procedures. There are
 almost always substantial staff or contracting costs.</P>
<P>Security takes staff time for planning, implementation, testing and
 auditing. Some of the issues are subtle; you need good (hence often
 expensive) people for this. You also need people to monitor your
 systems and respond to problems. The best safe ever built is insecure
 if an attacker can work on it for days without anyone noticing. Any
 computer is insecure if the administrator is &quot;too busy&quot; to check the
 logs.</P>
<P>Moreover, someone in your organisation (or on contract to it) needs
 to spend considerable time keeping up with new developments. EvilDoers<EM>
 will</EM> know about new attacks shortly after they are found. You need
 to know about them before your systems are attacked. If your vendor
 provides a patch, you need to apply it. If the vendor does nothing, you
 need to complain or start looking for another vendor.</P>
<P>For a fairly awful example, see this<A href="http://www.sans.org/newlook/alerts/NTE-bank.htm">
 report</A>. In that case over a million credit card numbers were taken
 from e-commerce sites, using security flaws in Windows NT servers.
 Microsoft had long since released patches for most or all of the flaws,
 but the site administrators had not applied them.</P>
<P>At an absolute minimum, you must do something about such issues<EM>
 before</EM> an exploitation tool is posted to the net for downloading
 by dozens of &quot;script kiddies&quot;. Such a tool might appear at any time
 from the announcement of the security hole to several months later.
 Once it appears, anyone with a browser and an attitude can break any
 system whose administrators have done nothing about the flaw.</P>
<P>Compared to those costs, cipher overheads are an insignificant factor
 in the cost of security.</P>
<P>The only thing using a weak cipher can do for you is to cause all
 your other investment to be wasted.</P>
<H2><A name="exlaw">Cryptography Export Laws</A></H2>
<P>Many nations restrict the export of cryptography and some restrict
 its use by their citizens or others within their borders.</P>
<H3><A name="USlaw">US Law</A></H3>
<P>US laws, as currently interpreted by the US government, forbid export
 of most cryptographic software from the US in machine-readable form
 without government permission. In general, the restrictions apply even
 if the software is widely-disseminated or public-domain and even if it
 came from outside the US originally. Cryptography is legally a munition
 and export is tightly controlled under the<A href="#EAR"> EAR</A>
 Export Administration Regulations.</P>
<P>If you are a US citizen, your brain is considered US territory no
 matter where it is physically located at the moment. The US believes
 that its laws apply to its citizens everywhere, not just within the US.
 Providing technical assistance or advice to foreign &quot;munitions&quot;
 projects is illegal. The US government has very little sense of humor
 about this issue and does not consider good intentions to be sufficient
 excuse. Beware.</P>
<P>The<A href="http://www.bxa.doc.gov/Encryption/"> official website</A>
 for these regulations is run by the Commerce Department's Bureau of
 Export Administration (BXA).</P>
<P>The<A href="http://www.eff.org/bernstein/"> Bernstein case</A>
 challenges the export restrictions on Constitutional grounds. Code is
 speech so restrictions on export of code violate the First Amendment's
 free speech provisions. This argument has succeeded in two levels of
 court so far. It is quite likely to go on to the Supreme Court.</P>
<P>The regulations were changed substantially in January 2000,
 apparently as a government attempt to get off the hook in the Bernstein
 case. It is now legal to export public domain source code for
 encryption, provided you notify the<A href="#BXA"> BXA</A>.</P>
<P>There are, however, still restrictions in force. Moreover, the
 regulations can still be changed again whenever the government chooses
 to do so. Short of a Supreme Court ruling (in the Berstein case or
 another) that overturns the regulations completely, the problem of
 export regulation is not likely to go away in the forseeable future.</P>
<H4><A name="UScontrib">US contributions to FreeS/WAN</A></H4>
<P>The FreeS/WAN project<STRONG> cannot accept software contributions,<EM>
 not even small bug fixes</EM>, from US citizens or residents</STRONG>.
 We want it to be absolutely clear that our distribution is not subject
 to US export law. Any contribution from an American might open that
 question to a debate we'd prefer to avoid. It might also put the
 contributor at serious legal risk.</P>
<P>Of course Americans can still make valuable contributions (many
 already have) by reporting bugs, or otherwise contributing to
 discussions, on the project<A href="mail.html"> mailing list</A>. Since
 the list is public, this is clearly constitutionally protected free
 speech.</P>
<P>Note, however, that the export laws restrict Americans from providing
 technical assistance to foreign &quot;munitions&quot; projects. The government
 might claim that private discussions or correspondence with FreeS/WAN
 developers were covered by this. It is not clear what the courts would
 do with such a claim, so we strongly encourage Americans to use the
 list rather than risk the complications.</P>
<H3><A name="wrong">What's wrong with restrictions on cryptography</A></H3>
<P>Some quotes from prominent cryptography experts:</P>
<BLOCKQUOTE> The real aim of current policy is to ensure the continued
 effectiveness of US information warfare assets against individuals,
 businesses and governments in Europe and elsewhere.
<BR><A href="http://www.cl.cam.ac.uk/users/rja14"> Ross Anderson,
 Cambridge University</A></BLOCKQUOTE><BLOCKQUOTE> If the government
 were honest about its motives, then the debate about crypto export
 policy would have ended years ago.
<BR><A href="http://www.counterpane.com"> Bruce Schneier, Counterpane
 Systems</A></BLOCKQUOTE><BLOCKQUOTE> The NSA regularly lies to people
 who ask it for advice on export control. They have no reason not to;
 accomplishing their goal by any legal means is fine by them. Lying by
 government employees is legal.
<BR> John Gilmore.</BLOCKQUOTE>
<P>The Internet Architecture Board (IAB) and the Internet Engineering
 Steering Group (IESG) made a<A href="iab-iesg.stmt"> strong statement</A>
 in favour of worldwide access to strong cryptography. Essentially the
 same statement is in the appropriately numbered<A href="ftp://ftp.isi.edu/in-notes/rfc1984.txt">
 RFC 1984</A>. Two critical paragraphs are:</P>
<BLOCKQUOTE> ... various governments have actual or proposed policies on
 access to cryptographic technology ...
<P>(a) ... export controls ...
<BR> (b) ... short cryptographic keys ...
<BR> (c) ... keys should be in the hands of the government or ...
<BR> (d) prohibit the use of cryptology ...</P>
<P>We believe that such policies are against the interests of consumers
 and the business community, are largely irrelevant to issues of
 military security, and provide only a marginal or illusory benefit to
 law enforcement agencies, ...</P>
<P>The IAB and IESG would like to encourage policies that allow ready
 access to uniform strong cryptographic technology for all Internet
 users in all countries.</P>
</BLOCKQUOTE>
<P>Our goal in the FreeS/WAN project is to build just such &quot;strong
 cryptographic technology&quot; and to distribute it &quot;for all Internet users
 in all countries&quot;.</P>
<P>More recently, the same two bodies (IESG and IAB) have issued<A href="ftp://ftp.isi.edu/in-notes/rfc2804.txt">
 RFC 2804</A> on why the IETF should not build wiretapping capabilities
 into protocols for the convenience of security or law enforcement
 agenicies. The abstract from that document is:</P>
<BLOCKQUOTE> The Internet Engineering Task Force (IETF) has been asked
 to take a position on the inclusion into IETF standards-track documents
 of functionality designed to facilitate wiretapping.
<P>This memo explains what the IETF thinks the question means, why its
 answer is &quot;no&quot;, and what that answer means.</P>
</BLOCKQUOTE> A quote from the debate leading up to that RFC:<BLOCKQUOTE>
 We should not be building surveillance technology into standards. Law
 enforcement was not supposed to be easy. Where it is easy, it's called
 a police state.
<BR> Jeff Schiller of MIT, in a discussion of FBI demands for wiretap
 capability on the net, as quoted by<A href="http://www.wired.com/news/politics/0,1283,31895,00.html">
 Wired</A>.</BLOCKQUOTE>
<P>The<A href="http://www.ietf.org/mailman/listinfo/raven"> Raven</A>
 mailing list was set up for this IETF discussion.</P>
<P>Our goal is to go beyond that RFC and prevent Internet wiretapping
 entirely.</P>
<H3><A name="Wassenaar">The Wassenaar Arrangement</A></H3>
<P>Restrictions on the export of cryptography are not just US policy,
 though some consider the US at least partly to blame for the policies
 of other nations in this area.</P>
<P>A number of countries:</P>
<P>Argentina, Australia, Austria, Belgium, Bulgaria, Canada, Czech
 Republic, Denmark, Finland, France, Germany, Greece, Hungary, Ireland,
 Italy, Japan, Luxembourg, Netherlands, New Zealand, Norway, Poland,
 Portugal, Republic of Korea, Romania, Russian Federation, Slovak
 Republic, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom
 and United States</P>
<P>have signed the Wassenaar Arrangement which restricts export of
 munitions and other tools of war. Cryptographic sofware is covered
 there.</P>
<P>Wassenaar details are available from the<A href="http://www.wassenaar.org/">
 Wassenaar Secretariat</A>, and elsewhere in a more readable<A href="http://www.fitug.de/news/wa/index.html">
 HTML version</A>.</P>
<P>For a critique see the<A href="http://www.gilc.org/crypto/wassenaar">
 GILC site</A>:</P>
<BLOCKQUOTE> The Global Internet Liberty Campaign (GILC) has begun a
 campaign calling for the removal of cryptography controls from the
 Wassenaar Arrangement.
<P>The aim of the Wassenaar Arrangement is to prevent the build up of
 military capabilities that threaten regional and international security
 and stability . . .</P>
<P>There is no sound basis within the Wassenaar Arrangement for the
 continuation of any export controls on cryptographic products.</P>
</BLOCKQUOTE>
<P>We agree entirely.</P>
<P>An interesting analysis of Wassenaar can be found on the<A href="http://www.cyber-rights.org/crypto/wassenaar.htm">
 cyber-rights.org</A> site.</P>
<H3><A name="status">Export status of Linux FreeS/WAN</A></H3>
<P>We believe our software is entirely exempt from these controls since
 the Wassenaar<A href="http://www.wassenaar.org/list/GTN%20and%20GSN%20-%2099.pdf">
 General Software Note</A> says:</P>
<BLOCKQUOTE> The Lists do not control &quot;software&quot; which is either:
<OL>
<LI>Generally available to the public by . . . retail . . . or</LI>
<LI>&quot;In the public domain&quot;.</LI>
</OL>
</BLOCKQUOTE>
<P>There is a note restricting some of this, but it is a sub-heading
 under point 1, so it appears not to apply to public domain software.</P>
<P>Their glossary defines &quot;In the public domain&quot; as:</P>
<BLOCKQUOTE> . . . &quot;technology&quot; or &quot;software&quot; which has been made
 available without restrictions upon its further dissemination.
<P>N.B. Copyright restrictions do not remove &quot;technology&quot; or &quot;software&quot;
 from being &quot;in the public domain&quot;.</P>
</BLOCKQUOTE>
<P>We therefore believe that software freely distributed under the<A href="#GPL">
 GNU Public License</A>, such as Linux FreeS/WAN, is exempt from
 Wassenaar restrictions.</P>
<P>Most of the development work is being done in Canada. Our
 understanding is that the Canadian government accepts this
 interpretation.</P>
<UL>
<LI>A web statement of<A href="http://www.dfait-maeci.gc.ca/~eicb/notices/ser113-e.htm">
 Canadian policy</A> is available from the Department of Foreign Affairs
 and International Trade.</LI>
<LI>Another document from that department states that<A href="http://www.dfait-maeci.gc.ca/~eicb/export/gr1_e.htm">
 public domain software</A> is exempt from the export controls.</LI>
<LI>A researcher's<A href="http://insight.mcmaster.ca/org/efc/pages/doc/crypto-export.html">
 analysis</A> of Canadian policy is also available.</LI>
</UL>
<P>Recent copies of the freely modifiable and distributable source code
 exist in many countries. Citizens all over the world participate in its
 use and evolution, and guard its ongoing distribution. Even if Canadian
 policy were to change, the software would continue to evolve in
 countries which do not restrict exports, and would continue to be
 imported from there into unfree countries. &quot;The Net culture treats
 censorship as damage, and routes around it.&quot;</P>
<H3><A name="help">Help spread IPsec around</A></H3>
<P>You can help. If you don't know of a Linux FreeS/WAN archive in your
 own country, please download it now to your personal machine, and
 consider making it publicly accessible if that doesn't violate your own
 laws. If you have the resources, consider going one step further and
 setting up a mirror site for the whole<A href="#munitions"> munitions</A>
 Linux crypto software archive.</P>
<P>If you make Linux CD-ROMs, please consider including this code, in a
 way that violates no laws (in a free country, or in a domestic-only CD
 product).</P>
<P>Please send a note about any new archive mirror sites or CD
 distributions to linux-ipsec@clinet.fi so we can update the
 documentation.</P>
<P>Lists of current<A href="#sites"> mirror sites</A> and of<A href="#distwith">
 distributions</A> which include FreeS/WAN are in our introduction
 section.</P>
<H2><A name="desnotsecure">DES is Not Secure</A></H2>
<P>DES, the<STRONG> D</STRONG>ata<STRONG> E</STRONG>ncryption<STRONG> S</STRONG>
tandard, can no longer be considered secure. While no major flaws in its
 innards are known, it is fundamentally inadequate because its<STRONG>
 56-bit key is too short</STRONG>. It is vulnerable to<A href="#brute">
 brute-force search</A> of the whole key space, either by large
 collections of general-purpose machines or even more quickly by
 specialized hardware. Of course this also applies to<STRONG> any other
 cipher with only a 56-bit key</STRONG>. The only reason anyone could
 have for using a 56 or 64-bit key is to comply with various<A href="exportlaw.html">
 export laws</A> intended to ensure the use of breakable ciphers.</P>
<P>Non-government cryptologists have been saying DES's 56-bit key was
 too short for some time -- some of them were saying it in the 70's when
 DES became a standard -- but the US government has consistently
 ridiculed such suggestions.</P>
<P>A group of well-known cryptographers looked at key lengths in a<A href="http://www.counterpane.com/keylength.html">
 1996 paper</A>. They suggested a<EM> minimum</EM> of 75 bits to
 consider an existing cipher secure and a<EM> minimum of 90 bits for new
 ciphers</EM>. More recent papers, covering both<A href="#symmetric">
 symmetric</A> and<A href="#public"> public key</A> systems are at<A href="http://www.cryptosavvy.com/">
 cryptosavvy.com</A> and<A href="http://www.rsasecurity.com/rsalabs/bulletins/bulletin13.html">
 rsa.com</A>. For all algorithms, the minimum keylengths recommended in
 such papers are significantly longer than the maximums allowed by
 various export laws.</P>
<P>In a<A href="http://www.privacy.nb.ca/cryptography/archives/cryptography/html/1998-09/0095.html">
 1998 ruling</A>, a German court described DES as &quot;out-of-date and not
 safe enough&quot; and held a bank liable for using it.</P>
<H3><A name="deshware">Dedicated hardware breaks DES in a few days</A></H3>
<P>The question of DES security has now been settled once and for all.
 In early 1998, the<A href="http://www.eff.org/"> Electronic Frontier
 Foundation</A> built a<A href="http://www.eff.org/descracker.html">
 DES-cracking machine</A>. It can find a DES key in an average of a few
 days' search. The details of all this, including complete code listings
 and complete plans for the machine, have been published in<A href="#EFF">
<CITE> Cracking DES</CITE></A>, by the Electronic Frontier Foundation.</P>
<P>That machine cost just over $200,000 to design and build. &quot;Moore's
 Law&quot; is that machines get faster (or cheaper, for the same speed) by
 roughly a factor of two every 18 months. At that rate, their $200,000
 in 1998 becomes $50,000 in 2001.</P>
<P>However, Moore's Law is not exact and the $50,000 estimate does not
 allow for the fact that a copy based on the published EFF design would
 cost far less than the original. We cannot say exactly what such a
 cracker would cost today, but it would likely be somewhere between
 $10,000 and $100,000.</P>
<P>A large corporation could build one of these out of petty cash. The
 cost is low enough for a senior manager to hide it in a departmental
 budget and avoid having to announce or justify the project. Any
 government agency, from a major municipal police force up, could afford
 one. Or any other group with a respectable budget -- criminal
 organisations, political groups, labour unions, religious groups, ...
 Or any millionaire with an obsession or a grudge, or just strange taste
 in toys.</P>
<P>One might wonder if a private security or detective agency would have
 one for rent. They wouldn't need many clients to pay off that
 investment.</P>
<H3><A name="spooks">Spooks may break DES faster yet</A></H3>
<P>As for the security and intelligence agencies of various nations,
 they may have had DES crackers for years, and theirs may be much
 faster. It is difficult to make most computer applications work well on
 parallel machines, or to design specialised hardware to accelerate
 them. Cipher-cracking is one of the very few exceptions. It is entirely
 straightforward to speed up cracking by just adding hardware. Within
 very broad limits, you can make it as fast as you like if you have the
 budget. The EFF's $200,000 machine breaks DES in a few days. An<A href="http://www.planepage.com/">
 aviation website</A> gives the cost of a B1 bomber as $200,000,000.
 Spending that much, an intelligence agency could break DES in an
 average time of<EM> six and a half minutes</EM>.</P>
<P>That estimate assumes they use the EFF's 1998 technology and just
 spend more money. They may have an attack that is superior to brute
 force, they quite likely have better chip technology (Moore's law, a
 bigger budget, and whatever secret advances they may have made) and of
 course they may have spent the price of an aircraft carrier, not just
 one aircraft.</P>
<P>In short, we have<EM> no idea</EM> how quickly these organisations
 can break DES. Unless they're spectacularly incompetent or horribly
 underfunded, they can certainly break it, but we cannot guess how
 quickly. Pick any time unit between days and milliseconds; none is
 entirely unbelievable. More to the point, none of them is of any
 comfort if you don't want such organisations reading your
 communications.</P>
<P>Note that this may be a concern even if nothing you do is a threat to
 anyone's national security. An intelligence agency might well consider
 it to be in their national interest for certain companies to do well.
 If you're competing against such companies in a world market and that
 agency can read your secrets, you have a serious problem.</P>
<P>One might wonder about technology the former Soviet Union and its
 allies developed for cracking DES during the Cold War. They must have
 tried; the cipher was an American standard and widely used. Certainly
 those countries have some fine mathematicians, and those agencies had
 budget. How well did they succeed? Is their technology now for sale or
 rent?</P>
<H3><A name="desnet">Networks break DES in a few weeks</A></H3>
<P>Before the definitive EFF effort, DES had been cracked several times
 by people using many machines. See this<A href="http://www.distributed.net/pressroom/DESII-1-PR.html">
 press release</A> for example.</P>
<P>A major corporation, university, or government department could break
 DES by using spare cycles on their existing collection of computers, by
 dedicating a group of otherwise surplus machines to the problem, or by
 combining the two approaches. It might take them weeks or months,
 rather than the days required for the EFF machine, but they could do
 it.</P>
<P>What about someone working alone, without the resources of a large
 organisation? For them, cracking DES will not be easy, but it may be
 possible. A few thousand dollars buys a lot of surplus workstations. A
 pile of such machines will certainly heat your garage nicely and might
 break DES in a few months or years. Or enroll at a university and use
 their machines. Or use an employer's machines. Or crack security
 somewhere and steal the resources to crack a DES key. Or write a virus
 that steals small amounts of resources on many machines. Or . . .</P>
<P>None of these approaches are easy or break DES really quickly, but an
 attacker only needs to find one that is feasible and breaks DES quickly
 enough to be dangerous. How much would you care to bet that this will
 be impossible if the attacker is clever and determined? How valuable is
 your data? Are you authorised to risk it on a dubious bet?</P>
<H3><A name="no_des">We disable DES</A></H3>
<P>In short, it is now absolutely clear that<STRONG> DES is not secure</STRONG>
 against</P>
<UL>
<LI>any<STRONG> well-funded opponent</STRONG></LI>
<LI>any opponent (even a penniless one) with access (even stolen access)
 to<STRONG> enough general purpose computers</STRONG></LI>
</UL>
<P>That is why<STRONG> Linux FreeS/WAN disables all transforms which use
 plain DES</STRONG> for encryption.</P>
<P>DES is in the source code, because we need DES to implement our
 default encryption transform,<A href="#3DES"> Triple DES</A>.<STRONG>
 We urge you not to use single DES</STRONG>. We do not provide any easy
 way to enable it in FreeS/WAN, and our policy is to provide no
 assistance to anyone wanting to do so.</P>
<H3><A name="40joke">40-bits is laughably weak</A></H3>
<P>The same is true, in spades, of ciphers -- DES or others -- crippled
 by 40-bit keys, as many ciphers were required to be until recently
 under various<A href="#exlaw"> export laws</A>. A brute force search of
 such a cipher's keyspace is 2<SUP>16</SUP> times faster than a similar
 search against DES. The EFF's machine can do a brute-force search of a
 40-bit key space in<EM> seconds</EM>. One contest to crack a 40-bit
 cipher was won by a student<A href="http://catless.ncl.ac.uk/Risks/18.80.html#subj1">
 using a few hundred idle machines at his university</A>. It took only
 three and half hours.</P>
<P>We do not, and will not, implement any 40-bit cipher.</P>
<H3><A name="altdes">Triple DES is almost certainly secure</A></H3>
<P><A href="#3DES">Triple DES</A>, usually abbreviated 3DES, applies DES
 three times, with three different keys. DES seems to be basically an
 excellent cipher design; it has withstood several decades of intensive
 analysis without any disastrous flaws being found. It's only major flaw
 is that the small keyspace allows brute force attacks to succeeed.
 Triple DES enlarges the key space to 168 bits, making brute-force
 search a ridiculous impossibility.</P>
<P>3DES is currently the only block cipher implemented in FreeS/WAN.
 3DES is, unfortunately, about 1/3 the speed of DES, but modern CPUs
 still do it at quite respectable speeds. Some<A href="#benchmarks">
 speed measurements</A> for our code are available.</P>
<H3><A name="aes.ipsec">AES in IPsec</A></H3>
<P>The<A href="#AES"> AES</A> project has chosen a replacement for DES,
 a new standard cipher for use in non-classified US government work and
 in regulated industries such as banking. This cipher will almost
 certainly become widely used for many applications, including IPsec.</P>
<P>The winner, announced in October 2000 after several years of analysis
 and discussion, was the<A href="http://www.esat.kuleuven.ac.be/~rijmen/rijndael/">
 Rijndael</A> cipher from two Belgian designers.</P>
<P>It is almost certain that FreeS/WAN will add AES support.<A href="#patch">
 AES patches</A> are already available.</P>
<H2><A name="press">Press coverage of Linux FreeS/WAN:</A></H2>
<H3><A NAME="26_6_1">FreeS/WAN 1.0 press</A></H3>
<UL>
<LI><A href="http://www.wired.com/news/news/technology/story/19136.html">
Wired</A> &quot;Linux-Based Crypto Stops Snoops&quot;, James Glave April 15 1999</LI>
<LI><A href="http://slashdot.org/articles/99/04/15/1851212.shtml">
Slashdot</A></LI>
<LI><A href="http://dgl.com/itinfo/1999/it990415.html">DGL</A>, Damar
 Group Limited; looking at FreeS/WAN from a perspective of business
 computing</LI>
<LI><A href="http://linuxtoday.com/stories/5010.html">Linux Today</A></LI>
<LI><A href="http://www.tbtf.com/archive/1999-04-21.html#Tcep">TBTF</A>,
 Tasty Bits from the Technology Front</LI>
<LI><A href="http://www.salonmagazine.com/tech/log/1999/04/16/encryption/index.html">
Salon Magazine</A> &quot;Free Encryption Takes a Big Step&quot;</LI>
</UL>
<H3><A name="release">Press release for version 1.0</A></H3>
<PRE>        Strong Internet Privacy Software Free for Linux Users Worldwide

Toronto, ON, April 14, 1999 - 

The Linux FreeS/WAN project today released free software to protect
the privacy of Internet communications using strong encryption codes.
FreeS/WAN automatically encrypts data as it crosses the Internet, to
prevent unauthorized people from receiving or modifying it.  One
ordinary PC per site runs this free software under Linux to become a
secure gateway in a Virtual Private Network, without having to modify
users' operating systems or application software.  The project built
and released the software outside the United States, avoiding US
government regulations which prohibit good privacy protection.
FreeS/WAN version 1.0 is available immediately for downloading at
http://www.xs4all.nl/~freeswan/.

&quot;Today's FreeS/WAN release allows network administrators to build
excellent secure gateways out of old PCs at no cost, or using a cheap
new PC,&quot; said John Gilmore, the entrepreneur who instigated the
project in 1996.  &quot;They can build operational experience with strong
network encryption and protect their users' most important
communications worldwide.&quot;

&quot;The software was written outside the United States, and we do not
accept contributions from US citizens or residents, so that it can be
freely published for use in every country,&quot; said Henry Spencer, who
built the release in Toronto, Canada.  &quot;Similar products based in the
US require hard-to-get government export licenses before they can be
provided to non-US users, and can never be simply published on a Web
site.  Our product is freely available worldwide for immediate
downloading, at no cost.&quot;

FreeS/WAN provides privacy against both quiet eavesdropping (such as
&quot;packet sniffing&quot;) and active attempts to compromise communications
(such as impersonating participating computers).  Secure &quot;tunnels&quot; carry
information safely across the Internet between locations such as a
company's main office, distant sales offices, and roaming laptops.  This
protects the privacy and integrity of all information sent among those
locations, including sensitive intra-company email, financial transactions
such as mergers and acquisitions, business negotiations, personal medical
records, privileged correspondence with lawyers, and information about
crimes or civil rights violations.  The software will be particularly
useful to frequent wiretapping targets such as private companies competing
with government-owned companies, civil rights groups and lawyers,
opposition political parties, and dissidents. 

FreeS/WAN provides privacy for Internet packets using the proposed
standard Internet Protocol Security (IPSEC) protocols.  FreeS/WAN
negotiates strong keys using Diffie-Hellman key agreement with 1024-bit
keys, and encrypts each packet with 168-bit Triple-DES (3DES).  A modern
$500 PC can set up a tunnel in less than a second, and can encrypt
6 megabits of packets per second, easily handling the whole available
bandwidth at the vast majority of Internet sites.  In preliminary testing,
FreeS/WAN interoperated with 3DES IPSEC products from OpenBSD, PGP, SSH,
Cisco, Raptor, and Xedia.  Since FreeS/WAN is distributed as source code,
its innards are open to review by outside experts and sophisticated users,
reducing the chance of undetected bugs or hidden security compromises.

The software has been in development for several years.  It has been
funded by several philanthropists interested in increased privacy on
the Internet, including John Gilmore, co-founder of the Electronic
Frontier Foundation, a leading online civil rights group.

Press contacts:
Hugh Daniel,   +1 408 353 8124, hugh@toad.com
Henry Spencer, +1 416 690 6561, henry@spsystems.net

* FreeS/WAN derives its name from S/WAN, which is a trademark of RSA Data
  Security, Inc; used by permission.</PRE>
<HR>
<H1><A name="ipsec.detail">The IPsec protocols</A></H1>
<P>This section provides information on the IPsec protocols which
 FreeS/WAN implements. For more detail, see the<A href="rfc.html"> RFCs</A>
.</P>
<P>The basic idea of IPsec is to provide security functions,<A href="#authentication">
 authentication</A> and<A href="#encryption"> encryption</A>, at the IP
 (Internet Protocol) level. This requires a higher-level protocol (IKE)
 to set things up for the IP-level services (ESP and AH).</P>
<H2><A NAME="27_1">Protocols and phases</A></H2>
<P>Three protocols are used in an IPsec implementation:</P>
<DL>
<DT>ESP, Encapsulating Security Payload</DT>
<DD>Encrypts and/or authenticates data</DD>
<DT>AH, Authentication Header</DT>
<DD>Provides a packet authentication service</DD>
<DT>IKE, Internet Key Exchange</DT>
<DD>Negotiates connection parameters, including keys, for the other two</DD>
</DL>
<P>The term &quot;IPsec&quot; (also written as IPSEC) is slightly ambiguous. In
 some contexts, it includes all three of the above but in other contexts
 it refers only to AH and ESP.</P>
<P>There is more detail below, but a quick summary of how the whole
 thing works is:</P>
<DL>
<DT>Phase one IKE (main mode exchange)</DT>
<DD>sets up a keying channel (ISAKMP SA) between the two gateways</DD>
<DT>Phase two IKE (quick mode exchange)</DT>
<DD>sets up data channels (IPsec SAs)</DD>
<DT>IPsec proper</DT>
<DD>exchanges data using AH or ESP</DD>
</DL>
<P>Both phases of IKE are repeated periodically to automate re-keying.</P>
<H2><A name="others">Applying IPsec</A></H2>
<P>Authentication and encryption functions for network data can, of
 course, be provided at other levels. Many security protocols work at
 levels above IP.</P>
<UL>
<LI><A href="#PGP">PGP</A> encrypts and authenticates mail messages</LI>
<LI><A href="#ssh">SSH</A> authenticates remote logins and then encrypts
 the session</LI>
<LI><A href="#SSL">SSL</A> or<A href="#TLS"> TLS</A> provides security
 at the sockets layer, e.g. for secure web browsing</LI>
</UL>
<P>and so on. Other techniques work at levels below IP. For example,
 data on a communications circuit or an entire network can be encrypted
 by specialised hardware. This is common practice in high-security
 applications.</P>
<H3><A name="advantages">Advantages of IPsec</A></H3>
<P>There are, however, advantages to doing it at the IP level instead
 of, or as well as, at other levels.</P>
<P>IPsec is the<STRONG> most general way to provide these services for
 the Internet</STRONG>.</P>
<UL>
<LI>Higher-level services protect a<EM> single protocol</EM>; for
 example PGP protects mail.</LI>
<LI>Lower level services protect a<EM> single medium</EM>; for example a
 pair of encryption boxes on the ends of a line make wiretaps on that
 line useless unless the attacker is capable of breaking the encryption.</LI>
</UL>
<P>IPsec, however, can protect<EM> any protocol</EM> running above IP
 and<EM> any medium</EM> which IP runs over. More to the point, it can
 protect a mixture of application protocols running over a complex
 combination of media. This is the normal situation for Internet
 communication; IPsec is the only general solution.</P>
<P>IPsec can also provide some security services &quot;in the background&quot;,
 with<STRONG> no visible impact on users</STRONG>. To use<A href="#PGP">
 PGP</A> encryption and signatures on mail, for example, the user must
 at least:</P>
<UL>
<LI>remember his or her passphrase,</LI>
<LI>keep it secure</LI>
<LI>follow procedures to validate correspondents' keys</LI>
</UL>
<P>These systems can be designed so that the burden on users is not
 onerous, but any system will place some requirements on users. No such
 system can hope to be secure if users are sloppy about meeting those
 requirements. The author has seen username and password stuck on
 terminals with post-it notes in an allegedly secure environment, for
 example.</P>
<H3><A name="limitations">Limitations of IPsec</A></H3>
<P>IPsec is designed to secure IP links between machines. It does that
 well, but it is important to remember that there are many things it
 does not do. Some of the important limitations are:</P>
<DL>
<DT><A name="depends">IPsec cannot be secure if your system isn't</A></DT>
<DD>System security on IPsec gateway machines is an essential
 requirement if IPsec is to function as designed. No system can be
 trusted if the underlying machine has been subverted. See books on Unix
 security such as<A href="#practical"> Garfinkel and Spafford</A> or our
 web references for<A href="#linsec"> Linux security</A> or more general<A
href="#compsec"> computer security</A>.
<P>Of course, there is another side to this. IPsec can be a powerful
 tool for improving system and network security. For example, requiring
 packet authentication makes various spoofing attacks harder and IPsec
 tunnels can be extremely useful for secure remote administration of
 various things.</P>
</DD>
<DT><A name="not-end-to-end">IPsec is not end-to-end</A></DT>
<DD>IPsec cannot provide the same end-to-end security as systems working
 at higher levels. IPsec encrypts an IP connection between two machines,
 which is quite a different thing than encrypting messages between users
 or between applications.
<P>For example, if you need mail encrypted from the sender's desktop to
 the recipient's desktop and decryptable only by the recipient, use<A href="#PGP">
 PGP</A> or another such system. IPsec can encrypt any or all of the
 links involved -- between the two mail servers, or between either
 server and its clients. It could even be used to secure a direct IP
 link from the sender's desktop machine to the recipient's, cutting out
 any sort of network snoop. What it cannot ensure is end-to-end
 user-to-user security. If only IPsec is used to secure mail, then
 anyone with appropriate privileges on any machine where that mail is
 stored (at either end or on any store-and-forward servers in the path)
 can read it.</P>
<P>In another common setup, IPsec encrypts packets at a security gateway
 machine as they leave the sender's site and decrypts them on arrival at
 the gateway to the recipient's site. This does provide a useful
 security service -- only encrypted data is passed over the Internet --
 but it does not even come close to providing an end-to-end service. In
 particular, anyone with appropriate privileges on either site's LAN can
 intercept the message in unencrypted form.</P>
</DD>
<DT><A name="notpanacea">IPsec cannot do everything</A></DT>
<DD>IPsec also cannot provide all the functions of systems working at
 higher levels of the protocol stack. If you need a document
 electronically signed by a particular person, then you need his or her<A
href="#signature"> digital signature</A> and a<A href="#public"> public
 key cryptosystem</A> to verify it with.
<P>Note, however, that IPsec authentication of the underlying
 communication can make various attacks on higher-level protocols more
 difficult. In particular, authentication prevents<A href="#middle">
 man-in-the-middle attacks</A>.</P>
</DD>
<DT><A name="no_user">IPsec authenticates machines, not users</A></DT>
<DD>IPsec uses strong authentication mechanisms to control which
 messages go to which machines, but it does not have the concept of user
 ID, which is vital to many other security mechansims and policies. This
 means some care must be taken in fitting the various security
 mechansims on a network together. For example, if you need to control
 which users access your database server, you need some non-IPsec
 mechansim for that. IPsec can control which machines connect to the
 server, and can ensure that data transfer to those machines is done
 securely, but that is all. Either the machines themselves must control
 user access or there must be some form of user authentication to the
 database, independent of IPsec.</DD>
<DT><A name="DoS">IPsec does not stop denial of service attacks</A></DT>
<DD><A href="#DOS">Denial of service</A> attacks aim at causing a system
 to crash, overload, or become confused so that legitimate users cannot
 get whatever services the system is supposed to provide. These are
 quite different from attacks in which the attacker seeks either to use
 the service himself or to subvert the service into delivering incorrect
 results.
<P>IPsec shifts the ground for DoS attacks; the attacks possible against
 systems using IPsec are different than those that might be used against
 other systems. It does not, however, eliminate the possibility of such
 attacks.</P>
</DD>
<DT><A name="traffic">IPsec does not stop traffic analysis</A></DT>
<DD><A href="#traffic">Traffic analysis</A> is the attempt to derive
 intelligence from messages without regard for their contents. In the
 case of IPsec, it would mean analysis based on things visible in the
 unencrypted headers of encrypted packets -- source and destination
 gateway addresses, packet size, et cetera. Given the resources to
 acquire such data and some skill in analysing it (both of which any
 national intelligence agency should have), this can be a very powerful
 technique.
<P>IPsec is not designed to defend against this. Partial defenses are
 certainly possible, and some are<A href="#traffic.resist"> described
 below</A>, but it is not clear that any complete defense can be
 provided.</P>
</DD>
</DL>
<H3><A name="uses">IPsec is a general mechanism for securing IP</A></H3>
<P>While IPsec does not provide all functions of a mail encryption
 package, it can encrypt your mail. In particular, it can ensure that
 all mail passing between a pair or a group of sites is encrypted. An
 attacker looking only at external traffic, without access to anything
 on or behind the IPsec gateway, cannot read your mail. He or she is
 stymied by IPsec just as he or she would be by<A href="#PGP"> PGP</A>.</P>
<P>The advantage is that IPsec can provide the same protection for<STRONG>
 anything transmitted over IP</STRONG>. In a corporate network example,
 PGP lets the branch offices exchange secure mail with head office. SSL
 and SSH allow them to securely view web pages, connect as terminals to
 machines, and so on. IPsec can support all those applications, plus
 database queries, file sharing (NFS or Windows), other protocols
 encapsulated in IP (Netware, Appletalk, ...), phone-over-IP,
 video-over-IP, ... anything-over-IP. The only limitation is that IP
 Multicast is not yet supported, though there are Internet Draft
 documents for that.</P>
<P>IPsec creates<STRONG> secure tunnels through untrusted networks</STRONG>
. Sites connected by these tunnels form VPNs,<A href="#VPN"> Virtual
 Private Networks</A>.</P>
<P>IPsec gateways can be installed wherever they are required.</P>
<UL>
<LI>One organisation might choose to install IPsec only on firewalls
 between their LANs and the Internet. This would allow them to create a
 VPN linking several offices. It would provide protection against anyone
 outside their sites.</LI>
<LI>Another might install IPsec on departmental servers so everything on
 the corporate backbone net was encrypted. This would protect messages
 on that net from everyone except the sending and receiving department.</LI>
<LI>Another might be less concerned with information secrecy and more
 with controlling access to certain resources. They might use IPsec
 packet authentication as part of an access control mechanism, with or
 without also using the IPsec encryption service.</LI>
<LI>It is even possible (assuming adequate processing power and an IPsec
 implementation in each node) to make every machine its own IPsec
 gateway so that everything on a LAN is encrypted. This protects
 information from everyone outside the sending and receiving machine.</LI>
<LI>These techniques can be combined in various ways. One might, for
 example, require authentication everywhere on a network while using
 encryption only for a few links.</LI>
</UL>
<P>Which of these, or of the many other possible variants, to use is up
 to you.<STRONG> IPsec provides mechanisms; you provide the policy</STRONG>
.</P>
<P><STRONG>No end user action is required</STRONG> for IPsec security to
 be used; they don't even have to know about it. The site
 administrators, of course, do have to know about it and to put some
 effort into making it work. Poor administration can compromise IPsec as
 badly as the post-it notes mentioned above. It seems reasonable,
 though, for organisations to hope their system administrators are
 generally both more security-conscious than end users and more able to
 follow computer security procedures. If not, at least there are fewer
 of them to educate or replace.</P>
<P>IPsec can be, and often should be, used with along with security
 protocols at other levels. If two sites communicate with each other via
 the Internet, then IPsec is the obvious way to protect that
 communication. If two others have a direct link between them, either
 link encryption or IPsec would make sense. Choose one or use both.
 Whatever you use at and below the IP level, use other things as
 required above that level. Whatever you use above the IP level,
 consider what can be done with IPsec to make attacks on the higher
 levels harder. For example,<A href="#middle"> man-in-the-middle attacks</A>
 on various protocols become difficult if authentication at packet level
 is in use on the potential victims' communication channel.</P>
<H3><A name="authonly">Using authentication without encryption</A></H3>
<P>Where appropriate, IPsec can provide authentication without
 encryption. One might do this, for example:</P>
<UL>
<LI>where the data is public but one wants to be sure of getting the
 right data, for example on some web sites</LI>
<LI>where encryption is judged unnecessary, for example on some company
 or department LANs</LI>
<LI>where strong encryption is provided at link level, below IP</LI>
<LI>where strong encryption is provided in other protocols, above IP
<BR> Note that IPsec authentication may make some attacks on those
 protocols harder.</LI>
</UL>
<P>Authentication has lower overheads than encryption.</P>
<P>The protocols provide four ways to build such connections, using
 either an AH-only connection or ESP using null encryption, and in
 either manually or automatically keyed mode. FreeS/WAN supports only
 one of these, manually keyed AH-only connections, and<STRONG> we do not
 recommend using that</STRONG>. Our reasons are discussed under<A href="#traffic.resist">
 Resisting traffic analysis</A> a few sections further along.</P>
<H3><A name="encnoauth">Encryption without authentication is dangerous</A>
</H3>
<P>Originally, the IPsec encryption protocol<A href="#ESP"> ESP</A>
 didn't do integrity checking. It only did encryption. Steve Bellovin
 found many ways to attack ESP used without authentication. See his
 paper<A href="http://www.research.att.com/~smb/papers/badesp.ps">
 Problem areas for the IP Security Protocols</A>. To make a secure
 connection, you had to add an<A href="#AH"> AH</A> Authentication
 Header as well as ESP. Rather than incur the overhead of several layers
 (and rather than provide an ESP layer that didn't actually protect the
 traffic), the IPsec working group built integrity and replay checking
 directly into ESP.</P>
<P>Today, typical usage is one of:</P>
<UL>
<LI>ESP for encryption and authentication</LI>
<LI>AH for authentication alone</LI>
</UL>
<P>Other variants are allowed by the standard, but not much used:</P>
<DL>
<DT>ESP encryption without authentication</DT>
<DD><STRONG>Bellovin has demonstrated fatal flaws in this. Do not use.</STRONG>
</DD>
<DT>ESP encryption with AH authentication</DT>
<DD>This has higher overheads than using the authentication in ESP, and
 no obvious benefit in most cases. The exception might be a network
 where AH authentication was widely or universally used. If you're going
 to do AH to conform with network policy, why authenticate again in the
 ESP layer?</DD>
<DT>Authenticate twice, with AH and with ESP</DT>
<DD>Why? Of course, some folk consider &quot;belt and suspenders&quot; the
 sensible approach to security. If you're among them, you might use both
 protocols here. You might also use both to satisfy different parts of a
 security policy. For example, an organisation might require AH
 authentication everywhere but two users within the organisation might
 use ESP as well.</DD>
<DT>ESP authentication without encryption</DT>
<DD>The standard allows this, calling it &quot;null encryption&quot;. FreeS/WAN
 does not support it. We recommend that you use AH instead if
 authentication is all you require. AH authenticates parts of the IP
 header, which ESP-null does not do.</DD>
</DL>
<P>Some of these variants cannot be used with FreeS/WAN because we do
 not support ESP-null and do not support automatic keying of AH-only
 connections.</P>
<P>There are fairly frequent suggestions that AH be dropped entirely
 from the IPsec specifications since ESP and null encryption can handle
 that situation. It is not clear whether this will occur. My guess is
 that it is unlikely.</P>
<H3><A name="multilayer">Multiple layers of IPsec processing are
 possible</A></H3>
<P>The above describes combinations possible on a single IPsec
 connection. In a complex network you may have several layers of IPsec
 in play, with any of the above combinations at each layer.</P>
<P>For example, a connection from a desktop machine to a database server
 might require AH authentication. Working with other host, network and
 database security measures, AH might be just the thing for access
 control. You might decide not to use ESP encryption on such packets,
 since it uses resources and might complicate network debugging. Within
 the site where the server is, then, only AH would be used on those
 packets.</P>
<P>Users at another office, however, might have their whole connection
 (AH headers and all) passing over an IPsec tunnel connecting their
 office to the one with the database server. Such a tunnel should use
 ESP encryption and authentication. You need authentication in this
 layer because without authentication the encryption is vulnerable and
 the gateway cannot verify the AH authentication. The AH is between
 client and database server; the gateways aren't party to it.</P>
<P>In this situation, some packets would get multiple layers of IPsec
 applied to them, AH on an end-to-end client-to-server basis and ESP
 from one office's security gateway to the other.</P>
<H3><A name="traffic.resist">Resisting traffic analysis</A></H3>
<P><A href="#traffic">Traffic analysis</A> is the attempt to derive
 useful intelligence from encrypted traffic without breaking the
 encryption.</P>
<P>Is your CEO exchanging email with a venture capital firm? With
 bankruptcy trustees? With an executive recruiting agency? With the
 holder of some important patents? If an eavesdropper learns about any
 of those, then he has interesting intelligence on your company, whether
 or not he can read the messages themselves.</P>
<P>Even just knowing that there is network traffic between two sites may
 tell an analyst something useful, especially when combined with
 whatever other information he or she may have. For example, if you know
 Company A is having cashflow problems and Company B is looking for
 aquisitions, then knowing that packets are passing between the two is
 interesting. It is more interesting if you can tell it is email, and
 perhaps yet more if you know the sender and recipient.</P>
<P>Except in the simplest cases, traffic analysis is hard to do well. It
 requires both considerable resources and considerable analytic skill.
 However, intelligence agencies of various nations have been doing it
 for centuries and many of them are likely quite good at it by now.
 Various commercial organisations, especially those working on &quot;targeted
 marketing&quot; may also be quite good at analysing certain types of
 traffic.</P>
<P>In general, defending against traffic analysis is also difficult.
 Inventing a really good defense could get you a PhD and some
 interesting job offers.</P>
<P>IPsec is not designed to stop traffic analysis and we know of no
 plausible method of extending it to do so. That said, there are ways to
 make traffic analysis harder. This section describes them.</P>
<H4><A name="extra">Using &quot;unnecessary&quot; encryption</A></H4>
<P>One might choose to use encryption even where it appears unnecessary
 in order to make analysis more difficult. Consider two offices which
 pass a small volume of business data between them using IPsec and also
 transfer large volumes of Usenet news. At first glance, it would seem
 silly to encrypt the newsfeed, except possibly for any newsgroups that
 are internal to the company. Why encrypt data that is all publicly
 available from many sites?</P>
<P>However, if we encrypt a lot of news and send it down the same
 connection as our business data, we make<A href="#traffic"> traffic
 analysis</A> much harder. A snoop cannot now make inferences based on
 patterns in the volume, direction, sizes, sender, destination, or
 timing of our business messages. Those messages are hidden in a mass of
 news messages encapsulated in the same way.</P>
<P>If we're going to do this we need to ensure that keys change often
 enough to remain secure even with high volumes and with the adversary
 able to get plaintext of much of the data. We also need to look at
 other attacks this might open up. For example, can the adversary use a
 chosen plaintext attack, deliberately posting news articles which, when
 we receive and encrypt them, will help break our encryption? Or can he
 block our business data transmission by flooding us with silly news
 articles? Or ...</P>
<P>Also, note that this does not provide complete protection against
 traffic analysis. A clever adversary might still deduce useful
 intelligence from statistical analysis (perhaps comparing the input
 newsfeed to encrypted output, or comparing the streams we send to
 different branch offices), or by looking for small packets which might
 indicate establishment of TCP connections, or ...</P>
<P>As a general rule, though, to improve resistance to traffic analysis,
 you should<STRONG> encrypt as much traffic as possible, not just as
 much as seems necessary.</STRONG></P>
<H4><A name="multi-encrypt">Using multiple encryption</A></H4>
<P>This also applies to using multiple layers of encryption. If you have
 an IPsec tunnel between two branch offices, it might appear silly to
 send<A href="#PGP"> PGP</A>-encrypted email through that tunnel.
 However, if you suspect someone is snooping your traffic, then it does
 make sense:</P>
<UL>
<LI>it protects the mail headers; they cannot even see who is mailing
 who</LI>
<LI>it protects against user bungles or software malfunctions that
 accidentally send messages in the clear</LI>
<LI>it makes any attack on the mail encryption much harder; they have to
 break IPsec or break into your network before they can start on the
 mail encryption</LI>
</UL>
<P>Similar arguments apply for<A href="#SSL"> SSL</A>-encrypted web
 traffic or<A href="#ssh"> SSH</A>-encrypted remote login sessions, even
 for end-to-end IPsec tunnels between systems in the two offices.</P>
<H4><A name="fewer">Using fewer tunnels</A></H4>
<P>It may also help to use fewer tunnels. For example, if all you
 actually need encrypted is connections between:</P>
<UL>
<LI>mail servers at branch and head offices</LI>
<LI>a few branch office users and the head office database server</LI>
</UL>
<P>You might build one tunnel per mail server and one per remote
 database user, restricting traffic to those applications. This gives
 the traffic analyst some information, however. He or she can
 distinguish the tunnels by looking at information in the ESP header
 and, given that distinction and the patterns of tunnel usage, might be
 able to figure out something useful. Perhaps not, but why take the
 risk?</P>
<P>We suggest instead that you build one tunnel per branch office,
 encrypting everything passing from head office to branches. This has a
 number of advantages:</P>
<UL>
<LI>it is easier to build and administer</LI>
<LI>it resists traffic analysis somewhat better</LI>
<LI>it provides security for whatever you forgot. For example, if some
 user at a remote office browses proprietary company data on some head
 office web page (that the security people may not even know about!),
 then that data is encrypted before it reaches the Internet.</LI>
</UL>
<P>Of course you might also want to add additional tunnels. For example,
 if some of the database data is confidential and should not be exposed
 even within the company, then you need protection from the user's
 desktop to the database server. We suggest you do that in whatever way
 seems appropriate -- IPsec, SSH or SSL might fit -- but, whatever you
 choose, pass it between locations via a gateway-to-gateway IPsec tunnel
 to provide some resistance to traffic analysis.</P>
<H2><A name="primitives">Cryptographic components</A></H2>
<P>IPsec combines a number of cryptographic techniques, all of them
 well-known and well-analyzed. The overall design approach was
 conservative; no new or poorly-understood components were included.</P>
<P>This section gives a brief overview of each technique. It is intended
 only as an introduction. There is more information, and links to
 related topics, in our<A href="glossary.html"> glossary</A>. See also
 our<A href="biblio.html"> bibliography</A> and cryptography<A href="#crypto.link">
 web links</A>.</P>
<H3><A name="block.cipher">Block ciphers</A></H3>
<P>The<A href="#encryption"> encryption</A> in the<A href="#ESP"> ESP</A>
 encapsulation protocol is done with a<A href="#block"> block cipher</A>
.</P>
<P>We do not implement<A href="#DES"> single DES</A>. It is<A href="#desnotsecure">
 insecure</A>. Our default, and currently only, block cipher is<A href="#3DES">
 triple DES</A>.</P>
<P>The<A href="#rijndael"> Rijndael</A> block cipher has won the<A href="#AES">
 AES</A> competition to choose a relacement for DES. It will almost
 certainly be added to FreeS/WAN and to other IPsec implementations.<A href="#patch">
 Patches</A> are already available.</P>
<H3><A name="hash.ipsec">Hash functions</A></H3>
<H4><A name="hmac.ipsec">The HMAC construct</A></H4>
<P>IPsec packet authentication is done with the<A href="#HMAC"> HMAC</A>
 construct. This is not just a hash of the packet data, but a more
 complex operation which uses both a hashing algorithm and a key. It
 therefore does more than a simple hash would. A simple hash would only
 tell you that the packet data was not changed in transit, or that
 whoever changed it also regenerated the hash. An HMAC also tells you
 that the sender knew the HMAC key.</P>
<P>For IPsec HMAC, the output of the hash algorithm is truncated to 96
 bits. This saves some space in the packets. More important, it prevents
 an attacker from seeing all the hash output bits and perhaps creating
 some sort of attack based on that knowledge.</P>
<H4><A NAME="27_3_2_2">Choice of hash algorithm</A></H4>
<P>The IPsec RFCs require two hash algorithms --<A href="#MD5"> MD5</A>
 and<A href="#SHA"> SHA-1</A> -- both of which FreeS/WAN implements.</P>
<P>Various other algorithms -- such as RIPEMD and Tiger -- are listed in
 the RFCs as optional. None of these are in the FreeS/WAN distribution,
 or are likely to be added, although user<A href="#patch"> patches</A>
 exist for several of them.</P>
<P>Additional hash algorithms --<A href="#SHA-256"> SHA-256, SHA-384 and
 SHA-512</A> -- may be required to give hash strength matching the
 strength of<A href="#AES"> AES</A>. These are likely to be added to
 FreeS/WAN along with AES.</P>
<H3><A name="DH.keying">Diffie-Hellman key agreement</A></H3>
<P>The<A href="#DH"> Diffie-Hellman</A> key agreement protocol allows
 two parties (A and B or<A href="#alicebob"> Alice and Bob</A>) to agree
 on a key in such a way that an eavesdropper who intercepts the entire
 conversation cannot learn the key.</P>
<P>The protocol is based on the<A href="#dlog"> discrete logarithm</A>
 problem and is therefore thought to be secure. Mathematicians have been
 working on that problem for years and seem no closer to a solution,
 though there is no proof that an efficient solution is impossible.</P>
<H3><A name="RSA.auth">RSA authentication</A></H3>
<P>The<A href="#RSA"> RSA</A> algorithm (named for its inventors --
 Rivest, Shamir and Adleman) is a very widely used<A href="glossary.html#">
 public key</A> cryptographic technique. It is used in IPsec as one
 method of authenticating gateways for Diffie-Hellman key negotiation.</P>
<H2><A name="structure">Structure of IPsec</A></H2>
<P>There are three protocols used in an IPsec implementation:</P>
<DL>
<DT>ESP, Encapsulating Security Payload</DT>
<DD>Encrypts and/or authenticates data</DD>
<DT>AH, Authentication Header</DT>
<DD>Provides a packet authentication service</DD>
<DT>IKE, Internet Key Exchange</DT>
<DD>Negotiates connection parameters, including keys, for the other two</DD>
</DL>
<P>The term &quot;IPsec&quot; is slightly ambiguous. In some contexts, it includes
 all three of the above but in other contexts it refers only to AH and
 ESP.</P>
<H3><A name="IKE.ipsec">IKE (Internet Key Exchange)</A></H3>
<P>The IKE protocol sets up IPsec (ESP or AH) connections after
 negotiating appropriate parameters (algorithms to be used, keys,
 connection lifetimes) for them. This is done by exchanging packets on
 UDP port 500 between the two gateways.</P>
<P>IKE (RFC 2409) was the outcome of a long, complex process in which
 quite a number of protocols were proposed and debated. Oversimplifying
 mildly, IKE combines:</P>
<DL>
<DT>ISAKMP (RFC 2408)</DT>
<DD>The<STRONG> I</STRONG>nternet<STRONG> S</STRONG>ecurity<STRONG> A</STRONG>
ssociation and<STRONG> K</STRONG>ey<STRONG> M</STRONG>anagement<STRONG>
 P</STRONG>rotocol manages negotiation of connections and defines<A href="#SA">
 SA</A>s (Security Associations) as a means of describing connection
 properties.</DD>
<DT>IPsec DOI for ISAKMP (RFC 2407)</DT>
<DD>A<STRONG> D</STRONG>omain<STRONG> O</STRONG>f<STRONG> I</STRONG>
nterpretation fills in the details necessary to turn the rather abstract
 ISAKMP protocol into a more tightly specified protocol, so it becomes
 applicable in a particular domain.</DD>
<DT>Oakley key determination protocol (RFC 2412)</DT>
<DD>Oakley creates keys using the<A href="#DH"> Diffie-Hellman</A> key
 agreement protocol.</DD>
</DL>
<P>For all the details, you would need to read the four<A href="rfc.html">
 RFCs</A> just mentioned (over 200 pages) and a number of others. We
 give a summary below, but it is far from complete.</P>
<H4><A name="phases">Phases of IKE</A></H4>
<P>IKE negotiations have two phases.</P>
<DL>
<DT>Phase one</DT>
<DD>The two gateways negotiate and set up a two-way ISAKMP SA which they
 can then use to handle phase two negotiations. One such SA between a
 pair of gateways can handle negotiations for multiple tunnels.</DD>
<DT>Phase two</DT>
<DD>Using the ISAKMP SA, the gateways negotiate IPsec (ESP and/or AH)
 SAs as required. IPsec SAs are unidirectional (a different key is used
 in each direction) and are always negotiated in pairs to handle two-way
 traffic. There may be more than one pair defined between two gateways.</DD>
</DL>
<P>Both of these phases use the UDP protocol and port 500 for their
 negotiations.</P>
<P>After both IKE phases are complete, you have IPsec SAs to carry your
 encrypted data. These use the ESP or AH protocols. These protocols do
 not have ports. Ports apply only to UDP or TCP.</P>
<P>The IKE protocol is designed to be extremely flexible. Among the
 things that can be negotiated (separately for each SA) are:</P>
<UL>
<LI>SA lifetime before rekeying</LI>
<LI>encryption algorithm used. We currently support only<A href="#3DES">
 triple DES</A>. Single DES is<A href="#desnotsecure"> insecure</A>. The
 RFCs say you MUST do DES, SHOULD do 3DES and MAY do various others. We
 do not do any of the others.</LI>
<LI>authentication algorithms. We support<A href="#MD5"> MD5</A> and<A href="#SHA">
 SHA</A>. These are the two the RFCs require.</LI>
<LI>choice of group for<A href="#DH"> Diffie-Hellman</A> key agreement.
 We currently support Groups 2 and 5 (which are defined modulo primes of
 various lengths) and do not support Group 1 (defined modulo a shorter
 prime, and therefore cryptographically weak) or groups 3 and 4 (defined
 using elliptic curves). The RFCs require only Group 1.</LI>
</UL>
<P>The protocol also allows implementations to add their own encryption
 algorithms, authentication algorithms or Diffie-Hellman groups. We do
 not support any such extensions, but there are some<A href="#patch">
 patches</A> that do.</P>
<P>There are a number of complications:</P>
<UL>
<LI>The gateways must be able to authenticate each other's identities
 before they can create a secure connection. This host authentication is
 part of phase one negotiations, and is a required prerequisite for
 packet authentication used later. Host authentication can be done in a
 variety of ways. Those supported by FreeS/WAN are discussed in our<A href="#auto-auth">
 advanced configuration</A> document.</LI>
<LI>Phase one can be done in two ways.
<UL>
<LI>Main Mode is required by the RFCs and supported in FreeS/WAN. It
 uses a 6-packet exzchange.</LI>
<LI>Aggressive Mode is somewhat faster (only 3 packets) but reveals more
 to an eavesdropper. This is optional in the RFCs, not currently
 supported by FreeS/WAN, and not likely to be.</LI>
</UL>
</LI>
<LI>A new group exchange may take place after phase one but before phase
 two, defining an additional group for use in the<A href="#DH">
 Diffie-Hellman</A> key agreement part of phase two. FreeS/WAN does not
 currently support this.</LI>
<LI>Phase two always uses Quick Mode, but there are two variants of
 that:
<UL>
<LI>One variant provides<A href="#PFS"> Perfect Forward Secrecy (PFS)</A>
. An attacker that obtains your long-term host authentication key does
 not immediately get any of your short-term packet encryption of packet
 authentication keys. He must conduct another successful attack each
 time you rekey to get the short-term keys. Having some short-term keys
 does not help him learn others. In particular, breaking your system
 today does not let him read messages he archived yestarday, assuming
 you've changed short-term keys in the meanwhile. We enable PFS as the
 default.</LI>
<LI>The other variant disables PFS and is therefore slightly faster. We
 do not recommend this since it is less secure, but FreeS/WAN does
 support it. You can enable it with a<VAR> pfs=no</VAR> statement in<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A>.</LI>
<LI>The protocol provides no way to negotiate which variant will be
 used. If one gateway is set for PFS and the other is not, the
 negotiation fails. This has proved a fairly common source of
 interoperation problems.</LI>
</UL>
</LI>
<LI>Several types of notification message may be sent by either side
 during either phase, or later. FreeS/WAN does not currently support
 these, but they are a likely addition in future releases.</LI>
<LI>There is a commit flag which may optionally be set on some messages.
 The<A href="http://www.lounge.org/ike_doi_errata.html"> errata</A> page
 for the RFCs includes two changes related to this, one to clarify the
 description of its use and one to block a<A href="#DOS"> denial of
 service</A> attack which uses it. We currently do not implement this
 feature.</LI>
</UL>
<P>These complications can of course lead to problems, particularly when
 two different implementations attempt to interoperate. For example, we
 have seen problems such as:</P>
<UL>
<LI>Some implementations (often products crippled by<A href="#exlaw">
 export laws</A>) have the insecure DES algorithm as their only
 supported encryption method. Other parts of our documentation discuss
 the<A href="#desnotsecure"> reasons we do not implement single DES</A>,
 and<A href="interop.html#noDES"> how to cope with crippled products</A>
.</LI>
<LI>Windows 2000 IPsec tries to negotiate using Aggressive Mode, which
 we don't support. Later on, it uses the commit bit, which we also don't
 support.</LI>
<LI>Various implementations disable PFS by default, and therefore will
 not talk to FreeS/WAN until you either turn on PFS on their end or turn
 it off in FreeS/WAN with a<VAR> pfs=no</VAR> entry in the connection
 description.</LI>
<LI>FreeS/WAN's interaction with PGPnet is complicated by their use of
 notification messages we do not yet support.</LI>
</UL>
<P>Despite this, we do interoperate successfully with many
 implementations, including both Windows 2000 and PGPnet. Details are in
 our<A href="interop.html"> interoperability</A> document.</P>
<H4><A name="sequence">Sequence of messages in IKE</A></H4>
<P>Each phase (see<A href="#phases"> previous section</A>)of IKE
 involves a series of messages. In Pluto error messages, these are
 abbreviated using:</P>
<DL>
<DT>M</DT>
<DD><STRONG>M</STRONG>ain mode, settting up the keying channel (ISAKMP
 SA)</DD>
<DT>Q</DT>
<DD><STRONG>Q</STRONG>uick mode, setting up the data channel (IPsec SA)</DD>
<DT>I</DT>
<DD><STRONG>I</STRONG>nitiator, the machine that starts the negotiation</DD>
<DT>R</DT>
<DD><STRONG>R</STRONG>esponder</DD>
</DL>
<P>For example, the six messages of a main mode negotiation, in
 sequence, are labelled:</P>
<PRE>       MI1 ----------&gt;
           &lt;---------- MR1
       MI2 ----------&gt; 
           &lt;---------- MR2
       MI3 ----------&gt;
           &lt;---------- MR3</PRE>
<H4><A name="struct.exchange">Structure of IKE messages</A></H4>
<P>Here is our Pluto developer explaining some of this on the mailing
 list:</P>
<PRE>When one IKE system (for example, Pluto) is negotiating with another
to create an SA, the Initiator proposes a bunch of choices and the
Responder replies with one that it has selected.

The structure of the choices is fairly complicated.  An SA payload
contains a list of lists of &quot;Proposals&quot;.  The outer list is a set of
choices: the selection must be from one element of this list.

Each of these elements is a list of Proposals.  A selection must be
made from each of the elements of the inner list.  In other words,
*all* of them apply (that is how, for example, both AH and ESP can
apply at once).

Within each of these Proposals is a list of Transforms.  For each
Proposal selected, one Transform must be selected (in other words,
each Proposal provides a choice of Transforms).

Each Transform is made up of a list of Attributes describing, well,
attributes.  Such as lifetime of the SA.  Such as algorithm to be
used.  All the Attributes apply to a Transform.

You will have noticed a pattern here: layers alternate between being
disjunctions (&quot;or&quot;) and conjunctions (&quot;and&quot;).

For Phase 1 / Main Mode (negotiating an ISAKMP SA), this structure is
cut back.  There must be exactly one Proposal.  So this degenerates to
a list of Transforms, one of which must be chosen.</PRE>
<H3><A name="services">IPsec Services, AH and ESP</A></H3>
<P>IPsec offers two services,<A href="#authentication"> authentication</A>
 and<A href="#encryption"> encryption</A>. These can be used separately
 but are often used together.</P>
<DL>
<DT>Authentication</DT>
<DD>Packet-level authentication allows you to be confident that a packet
 came from a particular machine and that its contents were not altered
 en route to you. No attempt is made to conceal or protect the contents,
 only to assure their integrity. Packet authentication can be provided
 separately using an<A href="#AH"> Authentication Header</A>, described
 just below, or it can be included as part of the<A href="#ESP"> ESP</A>
 (Encapsulated Security Payload) service, described in the following
 section. That service offers encryption as well as authentication. In
 either case, the<A href="#HMAC"> HMAC</A> construct is used as the
 authentication mechanism.
<P>There is a separate authentication operation at the IKE level, in
 which each gateway authenticates the other. This can be done in a
 variety of ways.</P>
</DD>
<DT>Encryption</DT>
<DD>Encryption allows you to conceal the contents of a message from
 eavesdroppers.
<P>In IPsec this is done using a<A href="#block"> block cipher</A>
 (normally<A href="#3DES"> Triple DES</A> for Linux). In the most used
 setup, keys are automatically negotiated, and periodically
 re-negotiated, using the<A href="#IKE"> IKE</A> (Internet Key Exchange)
 protocol. In Linux FreeS/WAN this is handled by the Pluto Daemon.</P>
<P>The IPsec protocol offering encryption is<A href="#ESP"> ESP</A>,
 Encapsulated Security Payload. It can also include a packet
 authentication service.</P>
</DD>
</DL>
<P>Note that<STRONG> encryption should always be used with some packet
 authentication service</STRONG>. Unauthenticated encryption is
 vulnerable to<A href="#middle"> man-in-the-middle attacks</A>. Also
 note that encryption does not prevent<A href="#traffic"> traffic
 analysis</A>.</P>
<H3><A name="AH.ipsec">The Authentication Header (AH)</A></H3>
<P>Packet authentication can be provided separately from encryption by
 adding an authentication header (AH) after the IP header but before the
 other headers on the packet. This is the subject of this section.
 Details are in RFC 2402.</P>
<P>Each of the several headers on a packet header contains a &quot;next
 protocol&quot; field telling the system what header to look for next. IP
 headers generally have either TCP or UDP in this field. When IPsec
 authentication is used, the packet IP header has AH in this field,
 saying that an Authentication Header comes next. The AH header then has
 the next header type -- usually TCP, UDP or encapsulated IP.</P>
<P>IPsec packet authentication can be added in transport mode, as a
 modification of standard IP transport. This is shown in this diagram
 from the RFC:</P>
<PRE>                  BEFORE APPLYING AH
            ----------------------------
      IPv4  |orig IP hdr  |     |      |
            |(any options)| TCP | Data |
            ----------------------------

                  AFTER APPLYING AH
            ---------------------------------
      IPv4  |orig IP hdr  |    |     |      |
            |(any options)| AH | TCP | Data |
            ---------------------------------
            ||
                 except for mutable fields</PRE>
<P>Athentication can also be used in tunnel mode, encapsulating the
 underlying IP packet beneath AH and an additional IP header.</P>
<PRE>                         ||
IPv4  | new IP hdr* |    | orig IP hdr*  |    |      |
      |(any options)| AH | (any options) |TCP | Data |
      ------------------------------------------------
      ||
      |           in the new IP hdr                  |</PRE>
<P>This would normally be used in a gateway-to-gateway tunnel. The
 receiving gateway then strips the outer IP header and the AH header and
 forwards the inner IP packet.</P>
<P>The mutable fields referred to are things like the time-to-live field
 in the IP header. These cannot be included in authentication
 calculations because they change as the packet travels.</P>
<H4><A name="keyed">Keyed MD5 and Keyed SHA</A></H4>
<P>The actual authentication data in the header is typically 96 bits and
 depends both on a secret shared between sender and receiver and on
 every byte of the data being authenticated. The technique used is<A href="#HMAC">
 HMAC</A>, defined in RFC 2104.</P>
<P>The algorithms involved are the<A href="#MD5"> MD5</A> Message Digest
 Algorithm or<A href="#SHA"> SHA</A>, the Secure Hash Algorithm. For
 details on their use in this application, see RFCs 2403 and 2404
 respectively.</P>
<P>For descriptions of the algorithms themselves, see RFC 1321 for MD5
 and<A href="#FIPS"> FIPS</A> (Federal Information Processing Standard)
 number 186 from<A href="#NIST"> NIST</A>, the US National Institute of
 Standards and Technology for SHA.<A href="#schneier"><CITE> Applied
 Cryptography</CITE></A> covers both in some detail, MD5 starting on
 page 436 and SHA on 442.</P>
<P>These algorithms are intended to make it nearly impossible for anyone
 to alter the authenticated data in transit. The sender calculates a
 digest or hash value from that data and includes the result in the
 authentication header. The recipient does the same calculation and
 compares results. For unchanged data, the results will be identical.
 The hash algorithms are designed to make it extremely difficult to
 change the data in any way and still get the correct hash.</P>
<P>Since the shared secret key is also used in both calculations, an
 interceptor cannot simply alter the authenticated data and change the
 hash value to match. Without the key, he or she (or even the dreaded
 They) cannot produce a usable hash.</P>
<H4><A name="sequence">Sequence numbers</A></H4>
<P>The authentication header includes a sequence number field which the
 sender is required to increment for each packet. The receiver can
 ignore it or use it to check that packets are indeed arriving in the
 expected sequence.</P>
<P>This provides partial protection against<A href="#replay"> replay
 attacks</A> in which an attacker resends intercepted packets in an
 effort to confuse or subvert the receiver. Complete protection is not
 possible since it is necessary to handle legitmate packets which are
 lost, duplicated, or delivered out of order, but use of sequence
 numbers makes the attack much more difficult.</P>
<P>The RFCs require that sequence numbers never cycle, that a new key
 always be negotiated before the sequence number reaches 2^32-1. This
 protects both against replays attacks using packets from a previous
 cyclce and against<A href="#birthday"> birthday attacks</A> on the the
 packet authentication algorithm.</P>
<P>In Linux FreeS/WAN, the sequence number is ignored for manually keyed
 connections and checked for automatically keyed ones. In manual mode,
 there is no way to negotiate a new key, or to recover from a sequence
 number problem, so we don't use sequence numbers.</P>
<H3><A name="ESP.ipsec">Encapsulated Security Payload (ESP)</A></H3>
<P>The ESP protocol is defined in RFC 2406. It provides one or both of
 encryption and packet authentication. It may be used with or without AH
 packet authentication.</P>
<P>Note that<STRONG> some form of packet authentication should<EM>
 always</EM> be used whenever data is encrypted</STRONG>. Without
 authentication, the encryption is vulnerable to active attacks which
 may allow an enemy to break the encryption. ESP should<STRONG> always</STRONG>
 either include its own authentication or be used with AH
 authentication.</P>
<P>The RFCs require support for only two mandatory encryption algorithms
 --<A href="#DES"> DES</A>, and null encryption -- and for two
 authentication methods -- keyed MD5 and keyed SHA. Implementers may
 choose to support additional algorithms in either category.</P>
<P>The authentication algorithms are the same ones used in the IPsec<A href="#AH">
 authentication header</A>.</P>
<P>We do not implement single DES since<A href="#desnotsecure"> DES is
 insecure</A>. Instead we provide<A href="#3DES"> triple DES or 3DES</A>
. This is currently the only encryption algorithm supported.</P>
<P>We do not implement null encryption since it is obviously insecure.</P>
<H2><A name="modes">IPsec modes</A></H2>
<P>IPsec can connect in two modes. Transport mode is a host-to-host
 connection involving only two machines. In tunnel mode, the IPsec
 machines act as gateways and trafiic for any number of client machines
 may be carried.</P>
<H3><A name="tunnel.ipsec">Tunnel mode</A></H3>
<P>Security gateways are required to support tunnel mode connections. In
 this mode the gateways provide tunnels for use by client machines
 behind the gateways. The client machines need not do any IPsec
 processing; all they have to do is route things to gateways.</P>
<H3><A name="transport.ipsec">Transport mode</A></H3>
<P>Host machines (as opposed to security gateways) with IPsec
 implementations must also support transport mode. In this mode, the
 host does its own IPsec processing and routes some packets via IPsec.</P>
<H2><A name="parts">FreeS/WAN parts</A></H2>
<H3><A name="KLIPS.ipsec">KLIPS: Kernel IPsec Support</A></H3>
<P>KLIPS is<STRONG> K</STRONG>erne<STRONG>L</STRONG><STRONG> IP</STRONG>
SEC<STRONG> S</STRONG>upport, the modifications necessary to support
 IPsec within the Linux kernel. KILPS does all the actual IPsec
 packet-handling, including</P>
<UL>
<LI>encryption</LI>
<LI>packet authentication calculations</LI>
<LI>creation of ESP and AH headers for outgoing packets</LI>
<LI>interpretation of those headers on incoming packets</LI>
</UL>
<P>KLIPS also checks all non-IPsec packets to ensure they are not
 bypassing IPsec security policies.</P>
<H3><A name="Pluto.ipsec">The Pluto daemon</A></H3>
<P><A href="manpage.d/ipsec_pluto.8.html">Pluto(8)</A> is a daemon which
 implements the IKE protocol. It</P>
<UL>
<LI>handles all the Phase one ISAKMP SAs</LI>
<LI>performs host authentication and negotiates with other gateways</LI>
<LI>creates IPsec SAs and passes the data required to run them to KLIPS</LI>
<LI>adjust routing and firewall setup to meet IPsec requirements. See
 our<A href="firewall.html"> IPsec and firewalling</A> document for
 details.</LI>
</UL>
<P>Pluto is controlled mainly by the<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A> configuration file.</P>
<H3><A name="command">The ipsec(8) command</A></H3>
<P>The<A href="manpage.d/ipsec.8.html"> ipsec(8)</A> command is a front
 end shellscript that allows control over IPsec activity.</P>
<H3><A name="ipsec.conf">Linux FreeS/WAN configuration file</A></H3>
<P>The configuration file for Linux FreeS/WAN is</P>
<PRE>        /etc/ipsec.conf</PRE>
<P>For details see the<A href="manpage.d/ipsec.conf.5.html">
 ipsec.conf(5)</A> manual page .</P>
<H2><A name="key">Key management</A></H2>
<P>There are several ways IPsec can manage keys. Not all are implemented
 in Linux FreeS/WAN.</P>
<H3><A name="current">Currently Implemented Methods</A></H3>
<H4><A name="manual">Manual keying</A></H4>
<P>IPsec allows keys to be manually set. In Linux FreeS/WAN, such keys
 are stored with the connection definitions in /etc/ipsec.conf.</P>
<P><A href="#manual">Manual keying</A> is useful for debugging since it
 allows you to test the<A href="#KLIPS"> KLIPS</A> kernel IPsec code
 without the<A href="#Pluto"> Pluto</A> daemon doing key negotiation.</P>
<P>In general, however, automatic keying is preferred because it is more
 secure.</P>
<H4><A name="auto">Automatic keying</A></H4>
<P>In automatic keying, the<A href="#Pluto"> Pluto</A> daemon negotiates
 keys using the<A href="#IKE"> IKE</A> Internet Key Exchange protocol.
 Connections are automatically re-keyed periodically.</P>
<P>This is considerably more secure than manual keying. In either case
 an attacker who acquires a key can read every message encrypted with
 that key, but automatic keys can be changed every few hours or even
 every few minutes without breaking the connection or requiring
 intervention by the system administrators. Manual keys can only be
 changed manually; you need to shut down the connection and have the two
 admins make changes. Moreover, they have to communicate the new keys
 securely, perhaps with<A href="#PGP"> PGP</A> or<A href="#ssh"> SSH</A>
. This may be possible in some cases, but as a general solution it is
 expensive, bothersome and unreliable. Far better to let<A href="#Pluto">
 Pluto</A> handle these chores; no doubt the administrators have enough
 to do.</P>
<P>Also, automatic keying is inherently more secure against an attacker
 who manages to subvert your gateway system. If manual keying is in use
 and an adversary acquires root privilege on your gateway, he reads your
 keys from /etc/ipsec.conf and then reads all messages encrypted with
 those keys.</P>
<P>If automatic keying is used, an adversary with the same privileges
 can read /etc/ipsec.secrets, but this does not contain any keys, only
 the secrets used to authenticate key exchanges. Having an adversary
 able to authenticate your key exchanges need not worry you overmuch.
 Just having the secrets does not give him any keys. You are still
 secure against<A href="#passive"> passive</A> attacks. This property of
 automatic keying is called<A href="#PFS"> perfect forward secrecy</A>,
 abbreviated PFS.</P>
<P>Unfortunately, having the secrets does allow an<A href="#active">
 active attack</A>, specifically a<A href="#middle"> man-in-the-middle</A>
 attack. Losing these secrets to an attacker may not be quite as
 disastrous as losing the actual keys, but it is<EM> still a serious
 security breach</EM>. These secrets should be guarded as carefully as
 keys.</P>
<H3><A name="notyet">Methods not yet implemented</A></H3>
<H4><A name="noauth">Unauthenticated key exchange</A></H4>
<P>It would be possible to exchange keys without authenticating the
 players. This would support<A href="#carpediem"> opportunistic
 encryption</A> -- allowing any two systems to encrypt their
 communications without requiring a shared PKI or a previously
 negotiated secret -- and would be secure against<A href="#passive">
 passive attacks</A>. It would, however, be highly vulnerable to active<A
href="#middle"> man-in-the-middle</A> attacks. RFC 2408 therefore
 specifies that all<A href="#ISAKMP"> ISAKMP</A> key management
 interactions<EM> must</EM> be authenticated.</P>
<P>There is room for debate here. Should we provide immediate security
 against<A href="#passive"> passive attacks</A> and encourage widespread
 use of encryption, at the expense of risking the more difficult<A href="#active">
 active attacks</A>? Or should we wait until we can implement a solution
 that can both be widespread and offer security against active attacks?</P>
<P>So far, we have chosen the second course, complying with the RFCs and
 waiting for secure DNS (see<A href="#DNS"> below</A>) so that we can do<A
href="#carpediem"> opportunistic encryption</A> right.</P>
<H4><A name="DNS">Key exchange using DNS</A></H4>
<P>The IPsec RFCs allow key exchange based on authentication services
 provided by<A href="#SDNS"> Secure DNS</A>. Once Secure DNS service
 becomes widely available, we expect to make this the<EM> primary key
 management method for Linux FreeS/WAN</EM>. It is the best way we know
 of to support<A href="#carpediem"> opportunistic encryption</A>,
 allowing two systems without a common PKI or previous negotiation to
 secure their communication.</P>
<P>We currently have code to acquire RSA keys from DNS but do not yet
 have code to validate Secure DNS signatures.</P>
<H4><A name="PKI">Key exchange using a PKI</A></H4>
<P>The IPsec RFCs allow key exchange based on authentication services
 provided by a<A href="#PKI"> PKI</A> or Public Key Infrastructure. With
 many vendors selling such products and many large organisations
 building these infrastructures, this will clearly be an important
 application of IPsec and one Linux FreeS/WAN will eventually support.</P>
<P>On the other hand, this is not as high a priority for Linux FreeS/WAN
 as solutions based on<A href="#SDNS"> secure DNS</A>. We do not expect
 any PKI to become as universal as DNS.</P>
<P>Some<A href="#patch"> patches</A> to handle authentication with X.509
 certificates, which most PKIs use, are available.</P>
<H4><A name="photuris">Photuris</A></H4>
<P><A href="#photuris">Photuris</A> is another key management protocol,
 an alternative to IKE and ISAKMP, described in RFCs 2522 and 2523 which
 are labelled &quot;experimental&quot;. Adding Photuris support to Linux FreeS/WAN
 might be a good project for a volunteer. The likely starting point
 would be the OpenBSD photurisd code.</P>
<H4><A name="skip">SKIP</A></H4>
<P><A href="#SKIP">SKIP</A> is yet another key management protocol,
 developed by Sun. At one point it was fairly widely used, but it now
 seems moribund, displaced by IKE. Sun now (as of Solaris 8.0) ship an
 IPsec implementation using IKE. We have no plans to implement SKIP. If
 a user were to implement it, we would almost certainly not want to add
 the code to our distribution.</P>
<HR>
<H1><A name="lists">Mailing lists and newsgroups</A></H1>
<H2><A name="list.fs">Mailing lists about FreeS/WAN</A></H2>
<H3><A name="projlist">The project mailing lists</A></H3>
<P>The Linux FreeS/WAN project has several email lists for user support,
 bug reports and software development discussions.</P>
<P>We had a single list on clinet.fi for several years (Thanks, folks!),
 then one list on freeswan.org, but now we've split into several lists:</P>
<DL>
<DT><A href="mailto:users-request@lists.freeswan.org?body=subscribe">
users</A></DT>
<DD>
<UL>
<LI>The general list for discussing use of the software</LI>
<LI>The place for seeking<STRONG> help with problems</STRONG> (but
 please check the<A href="faq.html"> FAQ</A> first).</LI>
<LI>Anyone can post.</LI>
</UL>
</DD>
<DT><A href="mailto:bugs-request@lists.freeswan.org?body=subscribe">bugs</A>
</DT>
<DD>
<UL>
<LI>For<STRONG> bug reports</STRONG>.</LI>
<LI>If you are not certain what is going on -- could be a bug, a
 configuration error, a network problem, ... -- please post to the users
 list instead.</LI>
<LI>Anyone can post.</LI>
</UL>
</DD>
<DT><A href="mailto:design-request@lists.freeswan.org?body=subscribe">
design</A></DT>
<DD>
<UL>
<LI><STRONG>Design discussions</STRONG>, for people working on FreeS/WAN
 development or others with an interest in design and security issues.</LI>
<LI>It would be a good idea to read the existing design papers (see this<A
href="#applied"> list</A>) before posting.</LI>
<LI>Anyone can post.</LI>
</UL>
</DD>
<DT><A href="mailto:announce-request@lists.freeswan.org?body=subscribe">
announce</A></DT>
<DD>
<UL>
<LI>A<STRONG> low-traffic</STRONG> list.</LI>
<LI><STRONG>Announcements</STRONG> about FreeS/WAN and related software.</LI>
<LI>All posts here are also sent to the users list. You need not
 subscribe to both.</LI>
<LI>Only the FreeS/WAN team can post.</LI>
<LI>If you have something you feel should go on this list, send it to<VAR>
 announce-admin@lists.freeswan.org</VAR>. Unless it is obvious, please
 include a short note explaining why we should post it.</LI>
</UL>
</DD>
<DT><A href="mailto:briefs-request@lists.freeswan.org?body=subscribe">
briefs</A></DT>
<DD>
<UL>
<LI>A<STRONG> low-traffic</STRONG> list.</LI>
<LI><STRONG>Weekly summaries</STRONG> of activity on the users list.</LI>
<LI>All posts here are also sent to the users list. You need not
 subscribe to both.</LI>
<LI>Only the FreeS/WAN team can post.</LI>
</UL>
</DD>
</DL>
<P>To subscribe to any of these, you can:</P>
<UL>
<LI>just follow the links above</LI>
<LI>use our<A href="http://www.freeswan.org/mail.html"> web interface</A>
</LI>
<LI>send mail to<VAR> listname</VAR>-request@lists.freeswan.org with a
 one-line message body &quot;subscribe&quot;</LI>
</UL>
<P>Archives of these lists are available via the<A href="http://www.freeswan.org/mail.html">
 web interface</A>.</P>
<H4><A name="which.list">Which list should I use?</A></H4>
<P>For most questions, please check the<A href="faq.html"> FAQ</A>
 first, and if that does not have an answer, ask on the users list. &quot;My
 configuration doesn't work.&quot; does not belong on the bugs list, and &quot;Can
 FreeS/WAN do such-and-such&quot; or &quot;How do I configure it to...&quot; do not
 belong in design discussions.</P>
<P>Cross-posting the same message to two or more of these lists is
 discouraged. Quite a few people read more than one list and getting
 multiple copies is annoying.</P>
<H4><A name="policy.list">List policies</A></H4>
<P><STRONG>US citizens or residents are asked not to post code to the
 lists, not even one-line bug fixes</STRONG>. The project cannot accept
 code which might entangle it in US<A href="#exlaw"> export restrictions</A>
.</P>
<P>Non-subscribers can post to some of these lists. This is necessary;
 someone working on a gateway install who encounters a problem may not
 have access to a subscribed account.</P>
<P>Some spam turns up on these lists from time to time. For discussion
 of why we do not attempt to filter it, see the<A href="#spam"> FAQ</A>.
 Please do not clutter the lists with complaints about this.</P>
<H3><A name="archive">Archives of the lists</A></H3>
<P>Searchable archives of the old single list have existed for some
 time. At time of writing, it is not yet clear how they will change for
 the new multi-list structure.</P>
<UL>
<LI><A href="http://www.sandelman.ottawa.on.ca/linux-ipsec">Canada</A></LI>
<LI><A href="http://www.nexial.com">Holland</A></LI>
</UL>
<P>Note that these use different search engines. Try both.</P>
<P>Archives of the new lists are available via the<A href="http://www.freeswan.org/mail.html">
 web interface</A>.</P>
<H2><A name="indexes">Indexes of mailing lists</A></H2>
<P><A href="http://paml.net/">PAML</A> is the standard reference for<STRONG>
 P</STRONG>ublicly<STRONG> A</STRONG>ccessible<STRONG> M</STRONG>ailing<STRONG>
 L</STRONG>ists. When we last checked, it had over 7500 lists on an
 amazing variety of topics. It also has FAQ information and a search
 engine.</P>
<P>There is an index of<A href="http://oslab.snu.ac.kr/~djshin/linux/mail-list/index.shtml">
 Linux mailing lists</A> available.</P>
<P>A list of<A href="http://xforce.iss.net/maillists/otherlists.php">
 computer security mailing lists</A>, with descriptions.</P>
<H2><A name="otherlists">Lists for related software and topics</A></H2>
<P>Most links in this section point to subscription addresses for the
 various lists. Send the one-line message &quot;subscribe<VAR> list_name</VAR>
&quot; to subscribe to any of them.</P>
<H3><A NAME="28_3_1">Products that include FreeS/WAN</A></H3>
<P>Our introduction document gives a<A href="#products"> list of
 products that include FreeS/WAN</A>. If you have, or are considering,
 one of those, check the supplier's web site for information on mailing
 lists for their users.</P>
<H3><A name="linux.lists">Linux mailing lists</A></H3>
<UL>
<LI><A href="mailto:majordomo@vger.kernel.org">
linux-admin@vger.kernel.org</A>, for Linux system administrators</LI>
<LI><A href="mailto:netfilter-request@lists.samba.org">
netfilter@lists.samba.org</A>, about Netfilter, which replaces IPchains
 in kernels 2.3.15 and later</LI>
<LI><A href="mailto:security-audit-request@ferret.lmh.ox.ac.uk">
security-audit@ferret.lmh.ox.ac.uk</A>, for people working on security
 audits of various Linux programs</LI>
<LI><A href="mailto:securedistros-request@humbolt.geo.uu.nl">
securedistros@humbolt.geo.uu.nl</A>, for discussion of issues common to
 all the half dozen projects working on secure Linux distributions.</LI>
</UL>
<P>Each of the scure distribution projects also has its own web site and
 mailing list. Some of the sites are:</P>
<UL>
<LI><A href="http://bastille-linux.org/">Bastille Linux</A> scripts to
 harden Redhat, e.g. by changing permissions and modifying inialisation
 scripts</LI>
<LI><A href="http://immunix.org/">Immunix</A> take a different approach,
 using a modified compiler to build kernel and utilities with better
 resistance to various types of overflow and exploit</LI>
<LI>the<A href="#NSA"> NSA</A> have contractors working on a<A href="#SElinux">
 Security Enhanced Linux</A>, primarily adding stronger access control
 mechanisms. You can download the current version (which interestingly
 is under GPL and not export resrtricted) or subscribe to the mailing
 list from the<A href="http://www.nsa.gov/selinux"> project web page</A>
.</LI>
</UL>
<H3><A name="ietf">Lists for IETF working groups</A></H3>
<P>Each<A href="#ietf"> IETF</A> working group has an associated mailing
 list where much of the work takes place.</P>
<UL>
<LI><A href="mailto:majordomo@lists.tislabs.com">ipsec@lists.tislabs.com</A>
, the IPsec<A href="http://www.ietf.org/html.charters/ipsec-charter.html">
 working group</A>. This is where the protocols are discussed, new
 drafts announced, and so on. By now, the IPsec working group is winding
 down since the work is essentially complete. A<A href="http://www.sandelman.ottawa.on.ca/ipsec/">
 list archive</A> is available.</LI>
<LI><A href="mailto:ipsec-policy-request@vpnc.org">IPsec policy</A>
 list, and its<A href="http://www.vpnc.org/ipsec-policy/"> archive</A></LI>
<LI><A href="mailto:ietf-ipsra-request@vpnc.org">IP secure remote access</A>
 list, and its<A href="http://www.vpnc.org/ietf-ipsra/mail-archive/">
 archive</A></LI>
</UL>
<H3><A name="other">Other mailing lists</A></H3>
<UL>
<LI><A href="mailto:ipc-announce-request@privacy.org">
ipc-announce@privacy.org</A> a low-traffic list with announcements of
 developments in privacy, encryption and online civil rights</LI>
<LI>a VPN mailing list's<A href="http://kubarb.phsx.ukans.edu/~tbird/vpn.html">
 home page</A></LI>
</UL>
<H2><A name="newsgroups">Usenet newsgroups</A></H2>
<UL>
<LI>sci.crypt</LI>
<LI>sci.crypt.research</LI>
<LI>comp.dcom.vpn</LI>
<LI>talk.politics.crypto</LI>
</UL>
<HR>
<H1><A name="weblink">Web links</A></H1>
<H2><A name="freeswan">The Linux FreeS/WAN Project</A></H2>
<P>The main project web site is<A href="http://www.freeswan.org/">
 www.freeswan.org</A>.</P>
<P>Links to other project-related<A href="#sites"> sites</A> are
 provided in our introduction section.</P>
<H3><A name="patch">Add-ons and patches for FreeS/WAN</A></H3>
<P>Some user-contributed patches have been integrated into the FreeS/WAN
 distribution. For a variety of reasons, those listed below have not.</P>
<P>Note that not all patches are a good idea.</P>
<UL>
<LI>There are a number of &quot;features&quot; of IPsec which we do not implement
 because they reduce security. See this<A href="#dropped"> discussion</A>
. We do not recommend using patches that implement these. One example is
 aggressive mode.</LI>
<LI>We do not recommend adding &quot;features&quot; of any sort unless they are
 clearly necessary, or at least have clear benefits. For example,
 FreeS/WAN would not become more secure if it offerred a choice of 14
 ciphers. If even one was flawed, it would certainly become less secure
 for anyone using that cipher. Even with 14 wonderful ciphers, it would
 be harder to maintain and administer, hence more vulnerable to various
 human errors.</LI>
</UL>
<P>This is not to say that patches are necessarily bad, only that using
 them requires some deliberation. For example, there might be perfectly
 good reasons to add a specific cipher in your application: perhaps GOST
 to comply with government standards in Eastern Europe, or AES for
 performance benefits.</P>
<H4><A NAME="29_1_1_1">Current patches</A></H4>
<P>Patches believed current::</P>
<UL>
<LI>patches for<A href="http://www.strongsec.com/freeswan/"> X.509
 certificate support</A>, also available from a<A href="http://www.twi.ch/~sna/strongsec/freeswan/">
 mirror site</A></LI>
<LI>patches to add<A href="http://www.irrigacion.gov.ar/juanjo/ipsec">
 AES and other ciphers</A>. There is preliminary data indicating AES
 gives a substantial<A href="#perf.more"> performance gain</A>.</LI>
</UL>
<P>There is also one add-on that takes the form of a modified FreeS/WAN
 distribution, rather than just patches to the standard distribution:</P>
<UL>
<LI><A href="http://www.ipv6.iabg.de/downloadframe/index.html">IPv6
 support</A></LI>
</UL>
<P>Before using any of the above,, check the<A href="mail.html"> mailing
 lists</A> for news of newer versions and to see whether they have been
 incorporated into more recent versions of FreeS/WAN.</P>
<H4><A NAME="29_1_1_2">Older patches</A></H4>
<UL>
<LI><A href="http://sources.colubris.com/en/projects/FreeSWAN/">hardware
 acceleration</A></LI>
<LI>a<A href="http://tzukanov.narod.ru/"> series</A> of patches that
<UL>
<LI>provide GOST, a Russian gov't. standard cipher, in MMX assembler</LI>
<LI>add GOST to OpenSSL</LI>
<LI>add GOST to the International kernel patch</LI>
<LI>let FreeS/WAN use International kernel patch ciphers</LI>
</UL>
</LI>
<LI>Neil Dunbar's patches for<A href="ftp://hplose.hpl.hp.com/pub/nd/pluto-openssl.tar.gz">
 certificate support</A>, using code from<A href="http://www.openssl.org">
 Open SSL</A>.</LI>
<LI>Luc Lanthier's<A href="ftp://ftp.netwinder.org/users/f/firesoul/">
 patches</A> for<A href="#PKIX"> PKIX</A> support.</LI>
<LI><A href="ftp://ftp.heise.de/pub/ct/listings/9916-180.tgz">patches</A>
 to add<A href="#Blowfish"> Blowfish</A>,<A href="#IDEA"> IDEA</A> and<A href="#CAST128">
 CAST-128</A> to FreeS/WAN</LI>
<LI>patches for FreeS/WAN 1.3, Pluto support for<A href="http://alcatraz.webcriminals.com/~bastiaan/ipsec/">
 external authentication</A>, for example with a smartcard or SKEYID.</LI>
<LI><A href="http://www.zengl.net/freeswan/download/">patches and
 utilities</A> for using FreeS/WAN with PGPnet</LI>
<LI><A href="http://www.freelith.com/lithworks/crypto/freeswan_patch.htm">
Blowfish encryption and Tiger hash</A></LI>
<LI><A href="http://www.cendio.se/~bellman/aggressive-pluto.snap.tar.gz">
patches</A> for aggressive mode support</LI>
</UL>
<P>These patches are for older versions of FreeS/WAN and will likely not
 work with the current version. Older versions of FreeS/WAN may be
 available on some of the<A href="#sites"> distribution sites</A>, but
 we recommend using the current release.</P>
<H4><A name="VPN.masq">VPN masquerade patches</A></H4>
<P>Finally, there are some patches to other code that may be useful with
 FreeS/WAN:</P>
<UL>
<LI>a<A href="ftp://ftp.rubyriver.com/pub/jhardin/masquerade/ip_masq_vpn.html">
 patch</A> to make IPsec, PPTP and SSH VPNs work through a Linux
 firewall with<A href="#masq"> IP masquerade</A>.</LI>
<LI><A href="http://www.linuxdoc.org/HOWTO/VPN-Masquerade-HOWTO.html">
Linux VPN Masquerade HOWTO</A></LI>
</UL>
<P>Note that this is not required if the same machine does IPsec and
 masquerading, only if you want a to locate your IPsec gateway on a
 masqueraded network. See our<A href="#NAT"> firewalls</A> document for
 discussion of why this is problematic.</P>
<P>At last report, this patch could not co-exist with FreeS/WAN on the
 same machine.</P>
<H3><A name="dist">Distributions including FreeS/WAN</A></H3>
<P>The introductory section of our document set lists several<A href="#distwith">
 Linux distributions</A> which include FreeS/WAN.</P>
<H3><A name="used">Things FreeS/WAN uses or could use</A></H3>
<UL>
<LI><A href="http://openpgp.net/random">/dev/random</A> support page,
 discussion of and code for the Linux<A href="#random"> random number
 driver</A>. Out-of-date when we last checked (January 2000), but still
 useful.</LI>
<LI>other programs related to random numbers:
<UL>
<LI><A href="http://www.mindrot.org/audio-entropyd.html">audio entropy
 daemon</A> to gather noise from a sound card and feed it into
 /dev/random</LI>
<LI>an<A href="http://www.lothar.com/tech/crypto/"> entropy-gathering
 daemon</A></LI>
<LI>a driver for the random number generator in recent<A href="http://sourceforge.net/projects/gkernel/">
 Intel chipsets</A>. This driver is included as standard in 2.4 kernels.</LI>
</UL>
</LI>
<LI>a Linux<A href="http://www.marko.net/l2tp/"> L2TP Daemon</A> which
 might be useful for communicating with Windows 2000 which builds L2TP
 tunnels over its IPsec connections</LI>
<LI>to use opportunistic encryption, you need a recent version of<A href="#BIND">
 BIND</A>. You can get one from the<A href="http://www.isc.org">
 Internet Software Consortium</A> who maintain BIND.</LI>
</UL>
<H3><A name="alternatives">Other approaches to VPNs for Linux</A></H3>
<UL>
<LI>other Linux<A href="#linuxipsec"> IPsec implementations</A></LI>
<LI><A href="http://www.tik.ee.ethz.ch/~skip/">ENskip</A>, a free
 implementation of Sun's<A href="#SKIP"> SKIP</A> protocol</LI>
<LI><A href="http://sunsite.auc.dk/vpnd/">vpnd</A>, a non-IPsec VPN
 daemon for Linux which creates tunnels using<A href="#Blowfish">
 Blowfish</A> encryption</LI>
<LI><A href="http://www.winton.org.uk/zebedee/">Zebedee</A>, a simple
 GPLd tunnel-building program with Linux and Win32 versions. The name is
 from<STRONG> Z</STRONG>lib compression,<STRONG> B</STRONG>lowfish
 encryption and<STRONG> D</STRONG>iffie-Hellman key exchange.</LI>
<LI>There are at least two PPTP implementations for Linux
<UL>
<LI>Moreton Bay's<A href="http://www.moretonbay.com/vpn/pptp.html">
 PoPToP</A></LI>
<LI><A href="http://cag.lcs.mit.edu/~cananian/Projects/PPTP/">PPTP-Linux</A>
</LI>
</UL>
</LI>
<LI><A href="http://sites.inka.de/sites/bigred/devel/cipe.html">CIPE</A>
 (crypto IP encapsulation) project, using their own lightweight protocol
 to encrypt between routers</LI>
<LI><A href="http://tinc.nl.linux.org/">tinc</A>, a VPN Daemon</LI>
</UL>
<P>There is a list of<A href="http://www.securityportal.com/lskb/10000000/kben10000005.html">
 Linux VPN</A> software in the<A href="http://www.securityportal.com/lskb/kben00000001.html">
 Linux Security Knowledge Base</A>.</P>
<H2><A name="ipsec.link">The IPsec Protocols</A></H2>
<H3><A name="general">General IPsec or VPN information</A></H3>
<UL>
<LI>The<A href="http://www.vpnc.org"> VPN Consortium</A> is a group for
 vendors of IPsec products. Among other things, they have a good
 collection of<A href="http://www.vpnc.org/white-papers.html"> IPsec
 white papers</A>.</LI>
<LI>A VPN mailing list with a<A href="http://kubarb.phsx.ukans.edu/~tbird/vpn.html">
 home page</A>, a FAQ, some product comparisons, and many links.</LI>
<LI><A href="http://www.opus1.com/vpn/index.html">VPN pointer page</A></LI>
<LI>a<A href="http://www.epm.ornl.gov/~dunigan/vpn.html"> collection</A>
 of VPN links, and some explanation</LI>
</UL>
<H3><A name="overview">IPsec overview documents or slide sets</A></H3>
<UL>
<LI>the FreeS/WAN<A href="ipsec.html"> document section</A> on these
 protocols</LI>
</UL>
<H3><A name="otherlang">IPsec information in languages other than
 English</A></H3>
<UL>
<LI><A href="http://www.imib.med.tu-dresden.de/imib/Internet/Literatur/ipsec-docu.html">
German</A></LI>
<LI><A href="http://www.kame.net/index-j.html">Japanese</A></LI>
<LI>Feczak Szabolcs' thesis in<A href="http://feczo.koli.kando.hu/vpn/">
 Hungarian</A></LI>
<LI>Davide Cerri's thesis and some presentation slides<A href="http://www.linux.it/~davide/doc/">
 Italian</A></LI>
</UL>
<H3><A name="RFCs1">RFCs and other reference documents</A></H3>
<UL>
<LI><A href="rfc.html">Our document</A> listing the RFCs relevant to
 Linux FreeS/WAN and giving various ways of obtaining both RFCs and
 Internet Drafts.</LI>
<LI><A href="http://www.vpnc.org/vpn-standards.html">VPN Standards</A>
 page maintained by<A href="#VPNC"> VPNC</A>. This covers both RFCs and
 Drafts, and classifies them in a fairly helpful way.</LI>
<LI><A href="http://www.rfc-editor.org">RFC archive</A></LI>
<LI><A href="http://www.ietf.org/ids.by.wg/ipsec.html">Internet Drafts</A>
 related to IPsec</LI>
<LI>US government<A href="http://www.itl.nist.gov/div897/pubs"> site</A>
 with their<A href="#FIPS"> FIPS</A> standards</LI>
<LI>Archives of the ipsec@tis.com mailing list where discussion of
 drafts takes place.
<UL>
<LI><A href="http://www.sandelman.ottawa.on.ca/ipsec">Eastern Canada</A></LI>
<LI><A href="http://www.vpnc.org/ietf-ipsec">California</A>.</LI>
</UL>
</LI>
</UL>
<H3><A name="analysis">Analysis and critiques of IPsec protocols</A></H3>
<UL>
<LI>Counterpane's<A href="http://www.counterpane.com/ipsec.pdf">
 evaluation</A> of the protocols</LI>
<LI>Simpson's<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/1999/06/msg00319.html">
 IKE Considered Dangerous</A> paper. Note that this is a link to an
 archive of our mailing list. There are several replies in addition to
 the paper itself.</LI>
<LI>Fate Labs<A href="http://www.fatelabs.com/loki-vpn.pdf"> Virual
 Private Problems: the Broken Dream</A></LI>
<LI>Catherine Meadows' paper<CITE> Analysis of the Internet Key Exchange
 Protocol Using the NRL Protocol Analyzer</CITE>, in<A href="http://chacs.nrl.navy.mil/publications/CHACS/1999/1999meadows-IEEE99.pdf">
 PDF</A> or<A href="http://chacs.nrl.navy.mil/publications/CHACS/1999/1999meadows-IEEE99.ps">
 Postscript</A>.</LI>
<LI>Perlman and Kaufmnan
<UL>
<LI><A href="http://snoopy.seas.smu.edu/ee8392_summer01/week7/perlman2.pdf">
Key Exchange in IPsec</A></LI>
<LI>a newer<A href="http://sec.femto.org/wetice-2001/papers/radia-paper.pdf">
 PDF paper</A>,<CITE> Analysis of the IPsec Key Exchange Standard</CITE>
.</LI>
</UL>
</LI>
<LI>Bellovin's<A href="http://www.research.att.com/~smb/papers/index.html">
 papers</A> page including his:
<UL>
<LI><CITE>Security Problems in the TCP/IP Protocol Suite</CITE> (1989)</LI>
<LI><CITE>Problem Areas for the IP Security Protocols</CITE> (1996)</LI>
<LI><CITE>Probable Plaintext Cryptanalysis of the IP Security Protocols</CITE>
 (1997)</LI>
</UL>
</LI>
<LI>An<A href="http://www.lounge.org/ike_doi_errata.html"> errata list</A>
 for the IPsec RFCs.</LI>
</UL>
<H3><A name="IP.background">Background information on IP</A></H3>
<UL>
<LI>An<A href="http://ipprimer.windsorcs.com/"> IP tutorial</A> that
 seems to be written mainly for Netware or Microsoft LAN admins entering
 a new world</LI>
<LI><A href="http://www.iana.org">IANA</A>, Internet Assigned Numbers
 Authority</LI>
<LI><A href="http://public.pacbell.net/dedicated/cidr.html">CIDR</A>,
 Classless Inter-Domain Routing</LI>
<LI>Also see our<A href="biblio.html"> bibliography</A></LI>
</UL>
<H2><A name="implement">IPsec Implementations</A></H2>
<H3><A name="linuxprod">Linux products</A></H3>
<P>Vendors using FreeS/WAN in turnkey firewall or VPN products are
 listed in our<A href="#turnkey"> introduction</A>.</P>
<P>Other vendors have Linux IPsec products which, as far as we know, do
 not use FreeS/WAN</P>
<UL>
<LI><A href="http://www.redcreek.com/products/shareware.html">Redcreek</A>
 provide an open source Linux driver for their PCI hardware VPN card.
 This card has a 100 Mbit Ethernet port, an Intel 960 CPU plus more
 specialised crypto chips, and claimed encryption performance of 45
 Mbit/sec. The PC sees it as an Ethernet board.</LI>
<LI><A href="http://linuxtoday.com/stories/8428.html?nn">Paktronix</A>
 offer a Linux-based VPN with hardware encryption</LI>
<LI><A href="http://www.watchguard.com/">Watchguard</A> use Linux in
 their Firebox product.</LI>
<LI><A href="http://www.entrust.com">Entrust</A> offer a developers'
 toolkit for using their<A href="#PKI"> PKI</A> for IPsec authentication</LI>
<LI>According to a report on our mailing list,<A href="http://www.axent.com">
 Axent</A> have a Linux version of their product.</LI>
</UL>
<H3><A name="router">IPsec in router products</A></H3>
<P>All the major router vendors support IPsec, at least in some models.</P>
<UL>
<LI><A href="http://www.cisco.com/warp/public/707/16.html">Cisco</A>
 IPsec information</LI>
<LI>Ascend, now part of<A href="http://www.lucent.com/"> Lucent</A>,
 have some IPsec-based products</LI>
<LI><A href="http://www.nortelnetworks.com/">Bay Networks</A>, now part
 of Nortel, use IPsec in their Contivity switch product line</LI>
<LI><A href="http://www.3com.com/products/enterprise.html">3Com</A> have
 a number of VPN products, some using IPsec</LI>
</UL>
<H3><A name="fw.web">IPsec in firewall products</A></H3>
<P>Many firewall vendors offer IPsec, either as a standard part of their
 product, or an optional extra. A few we know about are:</P>
<UL>
<LI><A href="http://www.borderware.com/">Borderware</A></LI>
<LI><A href="http://www.ashleylaurent.com/vpn/ipsec_vpn.htm">Ashley
 Laurent</A></LI>
<LI><A href="http://www.watchguard.com">Watchguard</A></LI>
<LI><A href="http://www.fx.dk/firewall/ipsec.html">Injoy</A> for OS/2</LI>
</UL>
<P>Vendors using FreeS/WAN in turnkey firewall products are listed in
 our<A href="#turnkey"> introduction</A>.</P>
<H3><A name="ipsecos">Operating systems with IPsec support</A></H3>
<P>All the major open source operating systems support IPsec. See below
 for details on<A href="#BSD"> BSD-derived</A> Unix variants.</P>
<P>Among commercial OS vendors, IPsec players include:</P>
<UL>
<LI><A href="http://msdn.microsoft.com/isapi/msdnlib.idc?theURL=/library/backgrnd/html/msdn_ip_security.htm">
Microsoft</A> have put IPsec in their Windows 2000 and XP products</LI>
<LI><A href="http://www.s390.ibm.com/stories/1999/os390v2r8_pr.html">IBM</A>
 announce a release of OS390 with IPsec support via a crypto
 co-processor</LI>
<LI><A href="http://www.sun.com/solaris/ds/ds-security/ds-security.pdf">
Sun</A> include IPsec in Solaris 8</LI>
<LI><A href="http://www.hp.com/security/products/extranet-security.html">
Hewlett Packard</A> offer IPsec for their Unix machines</LI>
<LI>Certicom have IPsec available for the<A href="http://www.certicom.com/products/movian/movianvpn_tech.html">
 Palm</A>.</LI>
<LI>There were reports before the release that Apple's Mac OS X would
 have IPsec support built in, but it did not seem to be there when we
 last checked. If you find, it please let us know via the<A href="mail.html">
 mailing list</A>.</LI>
</UL>
<H3><A NAME="29_3_5">IPsec on network cards</A></H3>
<P>Network cards with built-in IPsec acceleration are available from at
 least Intel, 3Com and Redcreek.</P>
<H3><A name="opensource">Open source IPsec implementations</A></H3>
<H4><A name="linuxipsec">Other Linux IPsec implementations</A></H4>
<P>We like to think of FreeS/WAN as<EM> the</EM> Linux IPsec
 implementation, but it is not the only one. Others we know of are:</P>
<UL>
<LI><A href="http://www.enst.fr/~beyssac/pipsec/">pipsecd</A>, a
 lightweight implementation of IPsec for Linux. Does not require kernel
 recompilation.</LI>
<LI>Petr Novak's<A href="ftp://ftp.eunet.cz/icz/ipnsec/"> ipnsec</A>,
 based on the OpenBSD IPsec code and using<A href="#photuris"> Photuris</A>
 for key management</LI>
<LI>A now defunct project at<A href="http://www.cs.arizona.edu/security/hpcc-blue/linux.html">
 U of Arizona</A> (export controlled)</LI>
<LI><A href="http://snad.ncsl.nist.gov/cerberus">NIST Cerebus</A>
 (export controlled)</LI>
</UL>
<H4><A name="BSD">IPsec for BSD Unix</A></H4>
<UL>
<LI><A href="http://www.kame.net/project-overview.html">KAME</A>,
 several large Japanese companies co-operating on IPv6 and IPsec</LI>
<LI><A href="http://web.mit.edu/network/isakmp">US Naval Research Lab</A>
 implementation of IPv6 and of IPsec for IPv4 (export controlled)</LI>
<LI><A href="http://www.openbsd.org">OpenBSD</A> includes IPsec as a
 standard part of the distribution</LI>
<LI><A href="http://www.r4k.net/ipsec">IPsec for FreeBSD</A></LI>
<LI>a<A href="http://www.netbsd.org/Documentation/network/ipsec/"> FAQ</A>
 on NetBSD's IPsec implementation</LI>
</UL>
<H4><A name="misc">IPsec for other systems</A></H4>
<UL>
<LI><A href="http://www.tcm.hut.fi/Tutkimus/IPSEC/">Helsinki U of
 Technolgy</A> have implemented IPsec for Solaris, Java and Macintosh</LI>
</UL>
<H3><A name="interop.web">Interoperability</A></H3>
<P>The IPsec protocols are designed so that different implementations
 should be able to work together. As they say &quot;the devil is in the
 details&quot;. IPsec has a lot of details, but considerable success has been
 achieved.</P>
<H4><A name="result">Interoperability results</A></H4>
<P>Linux FreeS/WAN has been tested for interoperability with many other
 IPsec implementations. Results to date are in our<A href="interop.html">
 interoperability</A> section.</P>
<P>Various other sites have information on interoperability between
 various IPsec implementations:</P>
<UL>
<LI><A href="http://www.opus1.com/vpn/atl99display.html">interop results</A>
 from a bakeoff in Atlanta, September 1999.</LI>
<LI>a French company, HSC's,<A href="http://www.hsc.fr/ressources/presentations/ipsec99/index.html.en">
 interoperability</A> test data covers FreeS/WAN, Open BSD, KAME, Linux
 pipsecd, Checkpoint, Red Creek Ravlin, and Cisco IOS</LI>
<LI><A href="http://www.icsa.net/">ICSA</A> offer certification programs
 for various security-related products. See their list of<A href="http://www.icsa.net/html/communities/ipsec/certification/certified_products/index.shtml">
 certified IPsec</A> products. Linux FreeS/WAN is not currently on that
 list, but several products with which we interoperate are.</LI>
<LI>VPNC have a page on why they are not yet doing<A href="http://www.vpnc.org/interop.html">
 interoperability</A> testing and a page on the<A href="http://www.vpnc.org/conformance.html">
 spec conformance</A> testing that they are doing</LI>
<LI>a<A href="http://www.commweb.com/article/COM20000912S0009"> review</A>
 comparing a dozen commercial IPsec implemetations. Unfortunately, the
 reviewers did not look at Open Source implementations such as FreeS/WAN
 or OpenBSD.</LI>
<LI><A href="http://www.tanu.org/~sakane/doc/public/report-ike-interop0007.html">
results</A> from interoperability tests at a conference. FreeS/WAN was
 not tested there.</LI>
<LI>test results from the<A href="http://www.hsc.fr/ressources/veille/ipsec/ipsec2000/">
 IPSEC 2000</A> conference</LI>
</UL>
<H4><A name="test1">Interoperability test sites</A></H4>
<UL>
<LI><A href="http://www.tahi.org/">TAHI</A>, a Japanese IPv6 testing
 project with free IPsec validation software</LI>
<LI><A href="http://ipsec-wit.antd.nist.gov">National Institute of
 Standards and Technology</A></LI>
<LI><A href="http://isakmp-test.ssh.fi/">SSH Communications Security</A></LI>
</UL>
<H2><A name="linux.link">Linux links</A></H2>
<H3><A name="linux.basic">Basic and tutorial Linux information</A></H3>
<UL>
<LI>Linux<A href="http://linuxcentral.com/linux/LDP/LDP/gs/gs.html">
 Getting Started</A> HOWTO document</LI>
<LI>A getting started guide from the<A href="http://darkwing.uoregon.edu/~cchome/linuxgettingstarted.html">
 U of Oregon</A></LI>
<LI>A large<A href="http://www.herring.org/techie.html"> link collection</A>
 which includes a lot of introductory and tutorial material on Unix,
 Linux, the net, . . .</LI>
</UL>
<H3><A name="general">General Linux sites</A></H3>
<UL>
<LI><A href="http://www.freshmeat.net">Freshmeat</A> Linux news</LI>
<LI><A href="http://slashdot.org">Slashdot</A> &quot;News for Nerds&quot;</LI>
<LI><A href="http://www.linux.org">Linux Online</A></LI>
<LI><A href="http://www.linuxhq.com">Linux HQ</A></LI>
<LI><A href="http://www.tux.org">tux.org</A></LI>
</UL>
<H3><A name="docs.ldp">Documentation</A></H3>
<P>Nearly any Linux documentation you are likely to want can be found at
 the<A href="http://metalab.unc.edu/LDP"> Linux Documentation Project</A>
 or LDP.</P>
<UL>
<LI><A href="http://metalab.unc.edu/LDP/HOWTO/META-FAQ.html">Meta-FAQ</A>
 guide to Linux information sources</LI>
<LI>The LDP's HowTo documents are a standard Linux reference. See this<A href="http://www.linuxdoc.org/docs.html#howto">
 list</A>. Documents there most relevant to a FreeS/WAN gateway are:
<UL>
<LI><A href="http://metalab.unc.edu/LDP/HOWTO/Kernel-HOWTO.html">Kernel
 HOWTO</A></LI>
<LI><A href="http://metalab.unc.edu/LDP/HOWTO/Networking-Overview-HOWTO.html">
Networking Overview HOWTO</A></LI>
<LI><A href="http://metalab.unc.edu/LDP/HOWTO/Security-HOWTO.html">
Security HOWTO</A></LI>
</UL>
</LI>
<LI>The LDP do a series of Guides, book-sized publications with more
 detail (and often more &quot;why do it this way?&quot;) than the HowTos. See this<A
href="http://www.linuxdoc.org/guides.html"> list</A>. Documents there
 most relevant to a FreeS/WAN gateway are:
<UL>
<LI><A href="http://www.tml.hut.fi/~viu/linux/sag/">System
 Administrator's Guide</A></LI>
<LI><A href="http://www.linuxdoc.org/LDP/nag2/index.html">Network
 Adminstrator's Guide</A></LI>
<LI><A href="http://www.seifried.org/lasg/">Linux Administrator's
 Security Guide</A></LI>
</UL>
</LI>
</UL>
<P>You may not need to go to the LDP to get this material. Most Linux
 distributions include the HowTos on their CDs and several include the
 Guides as well. Also, most of the Guides and some collections of HowTos
 are available in book form from various publishers.</P>
<P>Much of the LDP material is also available in languages other than
 English. See this<A href="http://www.linuxdoc.org/links/nenglish.html">
 LDP page</A>.</P>
<H3><A name="advroute.web">Advanced routing</A></H3>
<P>The Linux IP stack has some new features in 2.4 kernels. Some HowTos
 have been written:</P>
<UL>
<LI>several HowTos for the<A href="http://netfilter.samba.org/unreliable-guides/">
 netfilter</A> firewall code in newer kernels</LI>
<LI><A href="http://www.ds9a.nl/2.4Networking/HOWTO//cvs/2.4routing/output/2.4networking.html">
2.4 networking</A> HowTo</LI>
<LI><A href="http://www.ds9a.nl/2.4Networking/HOWTO//cvs/2.4routing/output/2.4routing.html">
2.4 routing</A> HowTo</LI>
</UL>
<H3><A name="linsec">Security for Linux</A></H3>
<P>See also the<A href="#docs.ldp"> LDP material</A> above.</P>
<UL>
<LI><A href="http://www.ecst.csuchico.edu/~dranch/LINUX/index-linux.html#trinityos">
Trinity OS guide to setting up Linux</A></LI>
<LI><A href="http://www.deter.com/unix">Unix security</A> page</LI>
<LI><A href="http://linux01.gwdg.de/~alatham/">PPDD</A> encrypting
 filesystem</LI>
<LI><A href="http://EncryptionHOWTO.sourceforge.net/">Linux Encryption
 HowTo</A> (outdated when last checked, had an Oct 2000 revision date in
 March 2002)</LI>
</UL>
<H3><A name="firewall.linux">Linux firewalls</A></H3>
<P>Our<A href="firewall.html"> FreeS/WAN and firewalls</A> document
 includes links to several sets of<A href="#examplefw"> scripts</A>
 known to work with FreeS/WAN.</P>
<P>Other information sources:</P>
<UL>
<LI><A href="http://ipmasq.cjb.net/">IP Masquerade resource page</A></LI>
<LI><A href="http://netfilter.samba.org/unreliable-guides/">netfilter</A>
 firewall code in 2.4 kernels</LI>
<LI>Our list of general<A href="#firewall.web"> firewall references</A>
 on the web</LI>
<LI><A href="http://users.dhp.com/~whisper/mason/">Mason</A>, a tool for
 automatically configuring Linux firewalls</LI>
<LI>the web cache software<A href="http://www.squid-cache.org/"> squid</A>
 and<A href="http://www.squidguard.org/"> squidguard</A> which turns
 Squid into a filtering web proxy</LI>
</UL>
<H3><A name="linux.misc">Miscellaneous Linux information</A></H3>
<UL>
<LI><A href="http://lwn.net/current/dists.php3">Linux distribution
 vendors</A></LI>
<LI><A href="http://www.linux.org/groups/">Linux User Groups</A></LI>
</UL>
<H2><A name="crypto.link">Crypto and security links</A></H2>
<H3><A name="security">Crypto and security resources</A></H3>
<H4><A name="std.links">The standard link collections</A></H4>
<P>Two enormous collections of links, each the standard reference in its
 area:</P>
<DL>
<DT>Gene Spafford's<A href="http://www.cerias.purdue.edu/coast/hotlist/">
 COAST hotlist</A></DT>
<DD>Computer and network security.</DD>
<DT>Peter Gutmann's<A href="http://www.cs.auckland.ac.nz/~pgut001/links.html">
 Encryption and Security-related Resources</A></DT>
<DD>Cryptography.</DD>
</DL>
<H4><A name="FAQ">Frequently Asked Question (FAQ) documents</A></H4>
<UL>
<LI><A href="http://www.faqs.org/faqs/cryptography-faq/">Cryptography
 FAQ</A></LI>
<LI><A href="http://www.interhack.net/pubs/fwfaq">Firewall FAQ</A></LI>
<LI><A href="http://www.whitefang.com/sup/secure-faq.html">Secure Unix
 Programming FAQ</A></LI>
<LI>FAQs for specific programs are listed in the<A href="#tools"> tools</A>
 section below.</LI>
</UL>
<H4><A name="cryptover">Tutorials</A></H4>
<UL>
<LI>Gary Kessler's<A href="http://www.garykessler.net/library/crypto.html">
 Overview of Cryptography</A></LI>
<LI>Terry Ritter's<A href="http://www.ciphersbyritter.com/LEARNING.HTM">
 introduction</A></LI>
<LI>Peter Gutman's<A href="http://www.cs.auckland.ac.nz/~pgut001/tutorial/index.html">
 cryptography</A> tutorial (500 slides in PDF format)</LI>
<LI>Amir Herzberg of IBM's sildes for his course<A href="http://www.hrl.il.ibm.com/mpay/course.html">
 Introduction to Cryptography and Electronic Commerce</A></LI>
<LI>the<A href="http://www.gnupg.org/gph/en/manual/c173.html"> concepts
 section</A> of the<A href="#GPG"> GNU Privacy Guard</A> documentation</LI>
<LI>Bruce Schneier's self-study<A href="http://www.counterpane.com/self-study.html">
 cryptanalysis</A> course</LI>
</UL>
<P>See also the<A href="#interesting"> interesting papers</A> section
 below.</P>
<H4><A name="standards">Crypto and security standards</A></H4>
<UL>
<LI><A href="http://csrc.nist.gov/cc">Common Criteria</A>, new
 international computer and network security standards to replace the
 &quot;Rainbow&quot; series</LI>
<LI>AES<A href="http://csrc.nist.gov/encryption/aes/aes_home.htm">
 Advanced Encryption Standard</A> which will replace DES</LI>
<LI><A href="http://grouper.ieee.org/groups/1363">IEEE P-1363 public key
 standard</A></LI>
<LI>our collection of links for the<A href="#ipsec.link"> IPsec</A>
 standards</LI>
<LI>history of<A href="http://www.visi.com/crypto/evalhist/index.html">
 formal evaluation</A> of security policies and implementation</LI>
</UL>
<H4><A name="quotes">Crypto quotes</A></H4>
<P>There are several collections of cryptographic quotes on the net:</P>
<UL>
<LI><A href="http://www.eff.org/pub/EFF/quotes.eff">the EFF</A></LI>
<LI><A href="http://www.samsimpson.com/cquotes.php">Sam Simpson</A></LI>
<LI><A href="http://www.amk.ca/quotations/cryptography/page-1.html">AM
 Kutchling</A></LI>
</UL>
<H3><A name="policy">Cryptography law and policy</A></H3>
<H4><A name="legal">Surveys of crypto law</A></H4>
<UL>
<LI>International survey of<A href="http://cwis.kub.nl/~FRW/PEOPLE/koops/lawsurvy.htm">
 crypto law</A>.</LI>
<LI>International survey of<A href="http://rechten.kub.nl/simone/ds-lawsu.htm">
 digital signature law</A></LI>
</UL>
<H4><A name="oppose">Organisations opposing crypto restrictions</A></H4>
<UL>
<LI>The<A href="#EFF"> EFF</A>'s archives on<A href="http://www.eff.org/pub/Privacy/">
 privacy</A> and<A href="http://www.eff.org/pub/Privacy/ITAR_export/">
 export control</A>.</LI>
<LI><A href="http://www.gilc.org">Global Internet Liberty Campaign</A></LI>
<LI><A href="http://www.cdt.org/crypto">Center for Democracy and
 Technology</A></LI>
<LI><A href="http://www.privacyinternational.org/">Privacy International</A>
, who give out<A href="http://www.bigbrotherawards.org/"> Big Brother
 Awards</A> to snoopy organisations</LI>
</UL>
<H4><A name="other.policy">Other information on crypto policy</A></H4>
<UL>
<LI><A href="ftp://ftp.isi.edu/in-notes/rfc1984.txt">RFC 1984</A>, the<A href="#IAB">
 IAB</A> and<A href="#IESG"> IESG</A> Statement on Cryptographic
 Technology and the Internet.</LI>
<LI>John Young's collection of<A href="http://cryptome.org/"> documents</A>
 of interest to the cryptography, open government and privacy movements,
 organized chronologically</LI>
<LI>AT&amp;T researcher Matt Blaze's Encryption, Privacy and Security<A href="http://www.crypto.com">
 Resource Page</A></LI>
<LI>A good<A href="http://cryptome.org/crypto97-ne.htm"> overview</A> of
 the issues from Australia.</LI>
</UL>
<P>See also our documentation section on the<A href="politics.html">
 history and politics</A> of cryptography.</P>
<H3><A name="crypto.tech">Cryptography technical information</A></H3>
<H4><A name="cryptolinks">Collections of crypto links</A></H4>
<UL>
<LI><A href="http://www.counterpane.com/hotlist.html">Counterpane</A></LI>
<LI><A href="http://www.cs.auckland.ac.nz/~pgut001/links.html">Peter
 Gutman's links</A></LI>
<LI><A href="http://www.pca.dfn.de/eng/team/ske/pem-dok.html">PKI links</A>
</LI>
<LI><A href="http://crypto.yashy.com/www/">Robert Guerra's links</A></LI>
</UL>
<H4><A name="papers">Lists of online cryptography papers</A></H4>
<UL>
<LI><A href="http://www.counterpane.com/biblio">Counterpane</A></LI>
<LI><A href="http://www.cryptography.com/resources/papers">
cryptography.com</A></LI>
<LI><A href="http://www.cryptosoft.com/html/secpub.htm">Cryptosoft</A></LI>
</UL>
<H4><A name="interesting">Particularly interesting papers</A></H4>
<P>These papers emphasize important issues around the use of
 cryptography, and the design and management of secure systems.</P>
<UL>
<LI><A href="http://www.counterpane.com/keylength.html">Key length
 requirements for security</A></LI>
<LI><A href="http://www.cl.cam.ac.uk/users/rja14/wcf.html">Why
 Cryptosystems Fail</A></LI>
<LI><A href="http://www.cdt.org/crypto/risks98/">Risks of escrowed
 encryption</A></LI>
<LI><A href="http://www.counterpane.com/pitfalls.html">Security pitfalls
 in cryptography</A></LI>
<LI><A href="http://www.acm.org/classics/sep95">Reflections on Trusting
 Trust</A>, Ken Thompson on Trojan horse design</LI>
<LI><A href="http://www.apache-ssl.org/disclosure.pdf">Security against
 Compelled Disclosure</A>, how to maintain privacy in the face of legal
 or other coersion</LI>
</UL>
<H3><A name="compsec">Computer and network security</A></H3>
<H4><A name="seclink">Security links</A></H4>
<UL>
<LI><A href="http://www.cs.purdue.edu/coast/hotlist">COAST Hotlist</A></LI>
<LI>DMOZ open directory project<A href="http://dmoz.org/Computers/Security/">
 computer security</A> links</LI>
<LI><A href="http://www-cse.ucsd.edu/users/bsy/sec.html">Bennet Yee</A></LI>
<LI>Mike Fuhr's<A href="http://www.fuhr.org/~mfuhr/computers/security.html">
 link collection</A></LI>
<LI><A href="http://www.networkintrusion.co.uk/">links</A> with an
 emphasis on intrusion detection</LI>
</UL>
<H4><A name="firewall.web">Firewall links</A></H4>
<UL>
<LI><A href="http://www.cs.purdue.edu/coast/firewalls">COAST firewalls</A>
</LI>
<LI><A href="http://www.zeuros.co.uk">Firewalls Resource page</A></LI>
</UL>
<H4><A name="vpn">VPN links</A></H4>
<UL>
<LI><A href="http://www.vpnc.org">VPN Consortium</A></LI>
<LI>First VPN's<A href="http://www.firstvpn.com/research/rhome.html">
 white paper</A> collection</LI>
</UL>
<H4><A name="tools">Security tools</A></H4>
<UL>
<LI>PGP -- mail encryption
<UL>
<LI><A href="http://www.pgp.com/">PGP Inc.</A> (part of NAI) for
 commercial versions</LI>
<LI><A href="http://web.mit.edu/network/pgp.html">MIT</A> distributes
 the NAI product for non-commercial use</LI>
<LI><A href="http://www.pgpi.org/">international</A> distribution site</LI>
<LI><A href="http://gnupg.org">GNU Privacy Guard (GPG)</A></LI>
<LI><A href="http://www.dk.pgp.net/pgpnet/pgp-faq/">PGP FAQ</A></LI>
</UL>
 A message in our mailing list archive has considerable detail on<A href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/12/msg00029.html">
 available versions</A> of PGP and on IPsec support in them.
<P><STRONG>Note:</STRONG> A fairly nasty bug exists in all commercial
 PGP versions from 5.5 through 6.5.3. If you have one of those,<STRONG>
 upgrade now</STRONG>.</P>
</LI>
<LI>SSH -- secure remote login
<UL>
<LI><A href="http://www.ssh.fi">SSH Communications Security</A>, for the
 original software. It is free for trial, academic and non-commercial
 use.</LI>
<LI><A href="http://www.openssh.com/">Open SSH</A>, the Open BSD team's
 free replacement</LI>
<LI><A href="http://www.freessh.org/">freessh.org</A>, links to free
 implementations for many systems</LI>
<LI><A href="http://www.uni-karlsruhe.de/~ig25/ssh-faq">SSH FAQ</A></LI>
<LI><A href="http://www.chiark.greenend.org.uk/~sgtatham/putty/">Putty</A>
, an SSH client for Windows</LI>
</UL>
</LI>
<LI>Tripwire saves message digests of your system files. Re-calculate
 the digests and compare to saved values to detect any file changes.
 There are several versions available:
<UL>
<LI><A href="http://www.tripwiresecurity.com/">commercial version</A></LI>
<LI><A href="http://www.tripwire.org/">Open Source</A></LI>
</UL>
</LI>
<LI><A href="http://www.snort.org">Snort</A> and<A href="http://www.lids.org">
 LIDS</A> are intrusion detection system for Linux</LI>
<LI><A href="http://www.fish.com/~zen/satan/satan.html">SATAN</A> System
 Administrators Tool for Analysing Networks</LI>
<LI><A href="http://www.insecure.org/nmap/">NMAP</A> Network Mapper</LI>
<LI><A href="ftp://ftp.porcupine.org/pub/security/index.html">Wietse
 Venema's page</A> with various tools</LI>
<LI><A href="http://ita.ee.lbl.gov/index.html">Internet Traffic Archive</A>
, various tools to analyze network traffic, mostly scripts to organise
 and format tcpdump(8) output for specific purposes</LI>
<LI><A name="ssmail">ssmail -- sendmail patched to do</A><A href="#carpediem">
 opportunistic encryption</A>
<UL>
<LI><A href="http://www.home.aone.net.au/qualcomm/">web page</A> with
 links to code and to a Usenix paper describing it, in PDF</LI>
</UL>
</LI>
<LI><A href="http://www.openca.org/">Open CA</A> project to develop a
 freely distributed<A href="#CA"> Certification Authority</A> for
 building a open<A href="#PKI"> Public Key Infrastructure</A>.</LI>
</UL>
<H3><A name="people">Links to home pages</A></H3>
<P>David Wagner at Berkeley provides a set of links to<A href="http://www.cs.berkeley.edu/~daw/people/crypto.html">
 home pages</A> of cryptographers, cypherpunks and computer security
 people.</P>
<HR>
<H1><A name="ourgloss">Glossary for the Linux FreeS/WAN project</A></H1>
<P>Entries are in alphabetical order. Some entries are only one line or
 one paragraph long. Others run to several paragraphs. I have tried to
 put the essential information in the first paragraph so you can skip
 the other paragraphs if that seems appropriate.</P>
<HR>
<H2><A name="jump">Jump to a letter in the glossary</A></H2>
<CENTER> <BIG><B><A href="#0">numeric</A><A href="#A"> A</A><A href="#B">
 B</A><A href="#C"> C</A><A href="#D"> D</A><A href="#E"> E</A><A href="#F">
 F</A><A href="#G"> G</A><A href="#H"> H</A><A href="#I"> I</A><A href="#J">
 J</A><A href="#K"> K</A><A href="#L"> L</A><A href="#M"> M</A><A href="#N">
 N</A><A href="#O"> O</A><A href="#P"> P</A><A href="#Q"> Q</A><A href="#R">
 R</A><A href="#S"> S</A><A href="#T"> T</A><A href="#U"> U</A><A href="#V">
 V</A><A href="#W"> W</A><A href="#X"> X</A><A href="#Y"> Y</A><A href="#Z">
 Z</A></B></BIG></CENTER>
<HR>
<H2><A name="gloss">Other glossaries</A></H2>
<P>Other glossaries which overlap this one include:</P>
<UL>
<LI>The VPN Consortium's glossary of<A href="http://www.vpnc.org/terms.html">
 VPN terms</A>.</LI>
<LI>glossary portion of the<A href="http://www.rsa.com/rsalabs/faq/B.html">
 Cryptography FAQ</A></LI>
<LI>an extensive crytographic glossary on<A href="http://www.ciphersbyritter.com/GLOSSARY.HTM">
 Terry Ritter's</A> page.</LI>
<LI>The<A href="#NSA"> NSA</A>'s<A href="http://www.sans.org/newlook/resources/glossary.htm">
 glossary of computer security</A> on the<A href="http://www.sans.org">
 SANS Institute</A> site.</LI>
<LI>a small glossary for Internet Security at<A href="http://www5.zdnet.com/pcmag/pctech/content/special/glossaries/internetsecurity.html">
 PC magazine</A></LI>
<LI>The<A href="http://www.visi.com/crypto/inet-crypto/glossary.html">
 glossary</A> from Richard Smith's book<A href="#Smith"> Internet
 Cryptography</A></LI>
</UL>
<P>Several Internet glossaries are available as RFCs:</P>
<UL>
<LI><A href="http://www.rfc-editor.org/rfc/rfc1208.txt">Glossary of
 Networking Terms</A></LI>
<LI><A href="http://www.rfc-editor.org/rfc/rfc1983.txt">Internet User's
 Glossary</A></LI>
<LI><A href="http://www.rfc-editor.org/rfc/rfc2828.txt">Internet
 Security Glossary</A></LI>
</UL>
<P>More general glossary or dictionary information:</P>
<UL>
<LI>Free Online Dictionary of Computing (FOLDOC)
<UL>
<LI><A href="http://www.nightflight.com/foldoc">North America</A></LI>
<LI><A href="http://wombat.doc.ic.ac.uk/foldoc/index.html">Europe</A></LI>
<LI><A href="http://www.nue.org/foldoc/index.html">Japan</A></LI>
</UL>
<P>There are many more mirrors of this dictionary.</P>
</LI>
<LI>The Jargon File, the definitive resource for hacker slang and
 folklore
<UL>
<LI><A href="http://www.netmeg.net/jargon">North America</A></LI>
<LI><A href="http://info.wins.uva.nl/~mes/jargon/">Holland</A></LI>
<LI><A href="http://www.tuxedo.org/~esr/jargon">home page</A></LI>
</UL>
<P>There are also many mirrors of this. See the home page for a list.</P>
</LI>
<LI>A general<A href="http://www.trinity.edu/~rjensen/245glosf.htm#Navigate">
 technology glossary</A></LI>
<LI>An<A href="http://www.yourdictionary.com/"> online dictionary
 resource page</A> with pointers to many dictionaries for many languages</LI>
<LI>A<A href="http://www.onelook.com/"> search engine</A> that accesses
 several hundred online dictionaries</LI>
<LI>O'Reilly<A href="http://www.ora.com/reference/dictionary/">
 Dictionary of PC Hardware and Data Communications Terms</A></LI>
<LI><A href="http://www.FreeSoft.org/CIE/index.htm">Connected</A>
 Internet encyclopedia</LI>
<LI><A href="http://www.whatis.com/">whatis.com</A></LI>
</UL>
<HR>
<H2><A name="definitions">Definitions</A></H2>
<DL>
<DT><A name="0">0</A></DT>
<DT><A name="3DES">3DES (Triple DES)</A></DT>
<DD>Using three<A href="#DES"> DES</A> encryptions on a single data
 block, with at least two different keys, to get higher security than is
 available from a single DES pass. The three-key version of 3DES is the
 default encryption algorithm for<A href="#FreeSWAN"> Linux FreeS/WAN</A>
.
<P><A href="#IPSEC">IPsec</A> always does 3DES with three different
 keys, as required by RFC 2451. For an explanation of the two-key
 variant, see<A href="#2key"> two key triple DES</A>. Both use an<A href="#EDE">
 EDE</A> encrypt-decrypt-encrpyt sequence of operations.</P>
<P>Single<A href="#DES"> DES</A> is<A href="#desnotsecure"> insecure</A>
.</P>
<P>Double DES is ineffective. Using two 56-bit keys, one might expect an
 attacker to have to do 2<SUP>112</SUP> work to break it. In fact, only
 2<SUP>57</SUP> work is required with a<A href="#meet">
 meet-in-the-middle attack</A>, though a large amount of memory is also
 required. Triple DES is vulnerable to a similar attack, but that just
 reduces the work factor from the 2<SUP>168</SUP> one might expect to 2<SUP>
112</SUP>. That provides adequate protection against<A href="#brute">
 brute force</A> attacks, and no better attack is known.</P>
<P>3DES can be somewhat slow compared to other ciphers. It requires
 three DES encryptions per block. DES was designed for hardware
 implementation and includes some operations which are difficult in
 software. However, the speed we get is quite acceptable for many uses.
 See our<A href="performance.html"> performance</A> document for
 details.</P>
</DD>
<DT><A name="A">A</A></DT>
<DT><A name="active">Active attack</A></DT>
<DD>An attack in which the attacker does not merely eavesdrop (see<A href="#passive">
 passive attack</A>) but takes action to change, delete, reroute, add,
 forge or divert data. Perhaps the best-known active attack is<A href="#middle">
 man-in-the-middle</A>. In general,<A href="#authentication">
 authentication</A> is a useful defense against active attacks.</DD>
<DT><A name="AES">AES</A></DT>
<DD>The<B> A</B>dvanced<B> E</B>ncryption<B> S</B>tandard -- a new<A href="#block">
 block cipher</A> standard to replace<A href="#desnotsecure"> DES</A> --
 developed by<A href="#NIST"> NIST</A>, the US National Institute of
 Standards and Technology. DES used 64-bit blocks and a 56-bit key. AES
 ciphers use a 128-bit block and 128, 192 or 256-bit keys. The larger
 block size helps resist<A href="#birthday"> birthday attacks</A> while
 the large key size prevents<A href="#brute"> brute force attacks</A>.
<P>Fifteen proposals meeting NIST's basic criteria were submitted in
 1998 and subjected to intense discussion and analysis, &quot;round one&quot;
 evaluation. In August 1999, NIST narrowed the field to five &quot;round two&quot;
 candidates:</P>
<UL>
<LI><A href="http://www.research.ibm.com/security/mars.html">Mars</A>
 from IBM</LI>
<LI><A href="http://www.rsa.com/rsalabs/aes/">RC6</A> from RSA</LI>
<LI><A href="http://www.esat.kuleuven.ac.be/~rijmen/rijndael/">Rijndael</A>
 from two Belgian researchers</LI>
<LI><A href="http://www.cl.cam.ac.uk/~rja14/serpent.html">Serpent</A>, a
 British-Norwegian-Israeli collaboration</LI>
<LI><A href="http://www.counterpane.com/twofish.html">Twofish</A> from
 the consulting firm<A href="http://www.counterpane.com"> Counterpane</A>
</LI>
</UL>
<P>Three of the five finalists -- Rijndael, Serpent and Twofish -- have
 completely open licenses.</P>
<P>In October 2000, NIST announced the winner -- Rijndael.</P>
<P>For more information, see:</P>
<UL>
<LI>NIST's<A href="http://csrc.nist.gov/encryption/aes/aes_home.htm">
 AES home page</A></LI>
<LI>the Block Cipher Lounge<A href="http://www.ii.uib.no/~larsr/aes.html">
 AES page</A></LI>
<LI>Brian Gladman's<A href="http://fp.gladman.plus.com/cryptography_technology/index.htm">
 code and benchmarks</A></LI>
<LI>Helger Lipmaa's<A href="http://www.tcs.hut.fi/~helger/aes/"> survey
 of implementations</A></LI>
</UL>
<P>AES will be added to a future release of<A href="#FreeSWAN"> Linux
 FreeS/WAN</A>. Likely we will add all three of the finalists with good
 licenses. User-written<A href="#patch"> AES patches</A> are already
 available.</P>
<P>Adding AES may also require adding stronger hashes,<A href="#SHA-256">
 SHA-256, SHA-384 and SHA-512</A>.</P>
</DD>
<DT><A name="AH">AH</A></DT>
<DD>The<A href="#IPSEC"> IPsec</A><B> A</B>uthentication<B> H</B>eader,
 added after the IP header. For details, see our<A href="#AH.ipsec">
 IPsec</A> document and/or RFC 2402.</DD>
<DT><A name="alicebob">Alice and Bob</A></DT>
<DD>A and B, the standard example users in writing on cryptography and
 coding theory. Carol and Dave join them for protocols which require
 more players.
<P>Bruce Schneier extends these with many others such as Eve the
 Eavesdropper and Victor the Verifier. His extensions seem to be in the
 process of becoming standard as well. See page 23 of<A href="#schneier">
 Applied Cryptography</A></P>
<P>Alice and Bob have an amusing<A href="http://www.conceptlabs.co.uk/alicebob.html">
 biography</A> on the web.</P>
</DD>
<DT>ARPA</DT>
<DD>see<A href="#DARPA"> DARPA</A></DD>
<DT><A name="ASIO">ASIO</A></DT>
<DD>Australian Security Intelligence Organisation.</DD>
<DT>Asymmetric cryptography</DT>
<DD>See<A href="#public"> public key cryptography</A>.</DD>
<DT><A name="authentication">Authentication</A></DT>
<DD>Ensuring that a message originated from the expected sender and has
 not been altered on route.<A href="#IPSEC"> IPsec</A> uses
 authentication in two places:
<UL>
<LI>peer authentication, authenticating the players in<A href="#IKE">
 IKE</A>'s<A href="#DH"> Diffie-Hellman</A> key exchanges to prevent<A href="#middle">
 man-in-the-middle attacks</A>. This can be done in a number of ways.
 The methods supported by FreeS/WAN are discussed in our<A href="#choose">
 advanced configuration</A> document.</LI>
<LI>packet authentication, authenticating packets on an established<A href="#SA">
 SA</A>, either with a separate<A href="#AH"> authentication header</A>
 or with the optional authentication in the<A href="#ESP"> ESP</A>
 protocol. In either case, packet authentication uses a<A href="#HMAC">
 hashed message athentication code</A> technique.</LI>
</UL>
<P>Outside IPsec, passwords are perhaps the most common authentication
 mechanism. Their function is essentially to authenticate the person's
 identity to the system. Passwords are generally only as secure as the
 network they travel over. If you send a cleartext password over a
 tapped phone line or over a network with a packet sniffer on it, the
 security provided by that password becomes zero. Sending an encrypted
 password is no better; the attacker merely records it and reuses it at
 his convenience. This is called a<A href="#replay"> replay</A> attack.</P>
<P>A common solution to this problem is a<A href="#challenge">
 challenge-response</A> system. This defeats simple eavesdropping and
 replay attacks. Of course an attacker might still try to break the
 cryptographic algorithm used, or the<A href="#random"> random number</A>
 generator.</P>
</DD>
<DT><A name="auto">Automatic keying</A></DT>
<DD>A mode in which keys are automatically generated at connection
 establisment and new keys automaically created periodically thereafter.
 Contrast with<A href="#manual"> manual keying</A> in which a single
 stored key is used.
<P>IPsec uses the<A href="#DH"> Diffie-Hellman key exchange protocol</A>
 to create keys. An<A href="#authentication"> authentication</A>
 mechansim is required for this. FreeS/WAN normally uses<A href="#RSA">
 RSA</A> for this. Other methods supported are discussed in our<A href="#choose">
 advanced configuration</A> document.</P>
<P>Having an attacker break the authentication is emphatically not a
 good idea. An attacker that breaks authentication, and manages to
 subvert some other network entities (DNS, routers or gateways), can use
 a<A href="#middle"> man-in-the middle attack</A> to break the security
 of your IPsec connections.</P>
<P>However, having an attacker break the authentication in automatic
 keying is not quite as bad as losing the key in manual keying.</P>
<UL>
<LI>An attacker who reads /etc/ipsec.conf and gets the keys for a
 manually keyed connection can, without further effort, read all
 messages encrypted with those keys, including any old messages he may
 have archived.</LI>
<LI>Automatic keying has a property called<A href="#PFS"> perfect
 forward secrecy</A>. An attacker who breaks the authentication gets
 none of the automatically generated keys and cannot immediately read
 any messages. He has to mount a successful<A href="#middle">
 man-in-the-middle attack</A> in real time before he can read anything.
 He cannot read old archived messages at all and will not be able to
 read any future messages not caught by man-in-the-middle tricks.</LI>
</UL>
<P>That said, the secrets used for authentication, stored in<A href="manpage.d/ipsec.secrets.5.html">
 ipsec.secrets(5)</A>, should still be protected as tightly as
 cryptographic keys.</P>
</DD>
<DT><A name="B">B</A></DT>
<DT><A href="http://www.nortelnetworks.com">Bay Networks</A></DT>
<DD>A vendor of routers, hubs and related products, now a subsidiary of
 Nortel. Interoperation between their IPsec products and Linux FreeS/WAN
 was problematic at last report; see our<A href="interop.html#bay">
 interoperation</A> section.</DD>
<DT><A name="benchmarks">benchmarks</A></DT>
<DD>Our default block cipher,<A href="#3DES"> triple DES</A>, is slower
 than many alternate ciphers that might be used. Speeds achieved,
 however, seem adequate for many purposes. For example, the assembler
 code from the<A href="#LIBDES"> LIBDES</A> library we use encrypts 1.6
 megabytes per second on a Pentium 200, according to the test program
 supplied with the library.
<P>For more detail, see our document on<A href="performance.html">
 FreeS/WAN performance</A>.</P>
</DD>
<DT><A name="BIND">BIND</A></DT>
<DD><B>B</B>erkeley<B> I</B>nternet<B> N</B>ame<B> D</B>aemon, a widely
 used implementation of<A href="#DNS"> DNS</A> (Domain Name Service).
 See our bibliography for a<A href="#DNS"> useful reference</A>. See the<A
href="http://www.isc.org/bind.html"> BIND home page</A> for more
 information and the latest version.</DD>
<DT><A name="birthday">Birthday attack</A></DT>
<DD>A cryptographic attack based on the mathematics exemplified by the<A href="#paradox">
 birthday paradox</A>. This math turns up whenever the question of two
 cryptographic operations producing the same result becomes an issue:
<UL>
<LI><A href="#collision">collisions</A> in<A href="#digest"> message
 digest</A> functions.</LI>
<LI>identical output blocks from a<A href="#block"> block cipher</A></LI>
<LI>repetition of a challenge in a<A href="#challenge">
 challenge-response</A> system</LI>
</UL>
<P>Resisting such attacks is part of the motivation for:</P>
<UL>
<LI>hash algorithms such as<A href="#SHA"> SHA</A> and<A href="#RIPEMD">
 RIPEMD-160</A> giving a 160-bit result rather than the 128 bits of<A href="#MD4">
 MD4</A>,<A href="#MD5"> MD5</A> and<A href="#RIPEMD"> RIPEMD-128</A>.</LI>
<LI><A href="#AES">AES</A> block ciphers using a 128-bit block instead
 of the 64-bit block of most current ciphers</LI>
<LI><A href="#IPSEC">IPsec</A> using a 32-bit counter for packets sent
 on an<A href="#auto"> automatically keyed</A><A href="#SA"> SA</A> and
 requiring that the connection always be rekeyed before the counter
 overflows.</LI>
</UL>
</DD>
<DT><A name="paradox">Birthday paradox</A></DT>
<DD>Not really a paradox, just a rather counter-intuitive mathematical
 fact. In a group of 23 people, the chance of a least one pair having
 the same birthday is over 50%.
<P>The second person has 1 chance in 365 (ignoring leap years) of
 matching the first. If they don't match, the third person's chances of
 matching one of them are 2/365. The 4th, 3/365, and so on. The total of
 these chances grows more quickly than one might guess.</P>
</DD>
<DT><A name="block">Block cipher</A></DT>
<DD>A<A href="#symmetric"> symmetric cipher</A> which operates on
 fixed-size blocks of plaintext, giving a block of ciphertext for each.
 Contrast with<A href="#stream"> stream cipher</A>. Block ciphers can be
 used in various<A href="#mode"> modes</A> when multiple block are to be
 encrypted.
<P><A href="#DES">DES</A> is among the the best known and widely used
 block ciphers, but is now obsolete. Its 56-bit key size makes it<A href="#desnotsecure">
 highly insecure</A> today.<A href="#3DES"> Triple DES</A> is the
 default block cipher for<A href="#FreeSWAN"> Linux FreeS/WAN</A>.</P>
<P>The current generation of block ciphers -- such as<A href="#Blowfish">
 Blowfish</A>,<A href="#CAST128"> CAST-128</A> and<A href="#IDEA"> IDEA</A>
 -- all use 64-bit blocks and 128-bit keys. The next generation,<A href="#AES">
 AES</A>, uses 128-bit blocks and supports key sizes up to 256 bits.</P>
<P>The<A href="http://www.ii.uib.no/~larsr/bc.html"> Block Cipher Lounge</A>
 web site has more information.</P>
</DD>
<DT><A name="Blowfish">Blowfish</A></DT>
<DD>A<A href="#block"> block cipher</A> using 64-bit blocks and keys of
 up to 448 bits, designed by<A href="#schneier"> Bruce Schneier</A> and
 used in several products.
<P>This is not required by the<A href="#IPSEC"> IPsec</A> RFCs and not
 currently used in<A href="#FreeSWAN"> Linux FreeS/WAN</A>.</P>
</DD>
<DT><A name="brute">Brute force attack (exhaustive search)</A></DT>
<DD>Breaking a cipher by trying all possible keys. This is always
 possible in theory (except against a<A href="#OTP"> one-time pad</A>),
 but it becomes practical only if the key size is inadequate. For an
 important example, see our document on the<A href="#desnotsecure">
 insecurity of DES</A> with its 56-bit key. For an analysis of key sizes
 required to resist plausible brute force attacks, see<A href="http://www.counterpane.com/keylength.html">
 this paper</A>.
<P>Longer keys protect against brute force attacks. Each extra bit in
 the key doubles the number of possible keys and therefore doubles the
 work a brute force attack must do. A large enough key defeats<STRONG>
 any</STRONG> brute force attack.</P>
<P>For example, the EFF's<A href="#EFF"> DES Cracker</A> searches a
 56-bit key space in an average of a few days. Let us assume an attacker
 that can find a 64-bit key (256 times harder) by brute force search in
 a second (a few hundred thousand times faster). For a 96-bit key, that
 attacker needs 2<SUP>32</SUP> seconds, about 135 years. Against a
 128-bit key, he needs 2<SUP>32</SUP> times that, over 500,000,000,000
 years. Your data is then obviously secure against brute force attacks.
 Even if our estimate of the attacker's speed is off by a factor of a
 million, it still takes him over 500,000 years to crack a message.</P>
<P>This is why</P>
<UL>
<LI>single<A href="#DES"> DES</A> is now considered<A href="#desnotsecure">
 dangerously insecure</A></LI>
<LI>all of the current generation of<A href="#block"> block ciphers</A>
 use a 128-bit or longer key</LI>
<LI><A href="#AES">AES</A> ciphers support keysizes 128, 192 and 256
 bits</LI>
<LI>any cipher we add to Linux FreeS/WAN will have<EM> at least</EM> a
 128-bit key</LI>
</UL>
<P><STRONG>Cautions:</STRONG>
<BR><EM> Inadequate keylength always indicates a weak cipher</EM> but it
 is important to note that<EM> adequate keylength does not necessarily
 indicate a strong cipher</EM>. There are many attacks other than brute
 force, and adequate keylength<EM> only</EM> guarantees resistance to
 brute force. Any cipher, whatever its key size, will be weak if design
 or implementation flaws allow other attacks.</P>
<P>Also,<EM> once you have adequate keylength</EM> (somewhere around 90
 or 100 bits),<EM> adding more key bits make no practical difference</EM>
, even against brute force. Consider our 128-bit example above that
 takes 500,000,000,000 years to break by brute force. We really don't
 care how many zeroes there are on the end of that, as long as the
 number remains ridiculously large. That is, we don't care exactly how
 large the key is as long as it is large enough.</P>
<P>There may be reasons of convenience in the design of the cipher to
 support larger keys. For example<A href="#Blowfish"> Blowfish</A>
 allows up to 448 bits and<A href="#RC4"> RC4</A> up to 2048, but beyond
 100-odd bits it makes no difference to practical security.</P>
</DD>
<DT>Bureau of Export Administration</DT>
<DD>see<A href="#BXA"> BXA</A></DD>
<DT><A name="BXA">BXA</A></DT>
<DD>The US Commerce Department's<B> B</B>ureau of E<B>x</B>port<B> A</B>
dministration which administers the<A href="#EAR"> EAR</A> Export
 Administration Regulations controling the export of, among other
 things, cryptography.</DD>
<DT><A name="C">C</A></DT>
<DT><A name="CA">CA</A></DT>
<DD><B>C</B>ertification<B> A</B>uthority, an entity in a<A href="#PKI">
 public key infrastructure</A> that can certify keys by signing them.
 Usually CAs form a hierarchy. The top of this hierarchy is called the<A href="#rootCA">
 root CA</A>.
<P>See<A href="#web"> Web of Trust</A> for an alternate model.</P>
</DD>
<DT><A name="CAST128">CAST-128</A></DT>
<DD>A<A href="#block"> block cipher</A> using 64-bit blocks and 128-bit
 keys, described in RFC 2144 and used in products such as<A href="#Entrust">
 Entrust</A> and recent versions of<A href="#PGP"> PGP</A>.
<P>This is not required by the<A href="#IPSEC"> IPsec</A> RFCs and not
 currently used in<A href="#FreeSWAN"> Linux FreeS/WAN</A>.</P>
</DD>
<DT>CAST-256</DT>
<DD><A href="#Entrust">Entrust</A>'s candidate cipher for the<A href="#AES">
 AES standard</A>, largely based on the<A href="#CAST128"> CAST-128</A>
 design.</DD>
<DT><A name="CBC">CBC mode</A></DT>
<DD><B>C</B>ipher<B> B</B>lock<B> C</B>haining<A href="#mode"> mode</A>,
 a method of using a<A href="#block"> block cipher</A> in which for each
 block except the first, the result of the previous encryption is XORed
 into the new block before it is encrypted. CBC is the mode used in<A href="#IPSEC">
 IPsec</A>.
<P>An<A href="#IV"> initialisation vector</A> (IV) must be provided. It
 is XORed into the first block before encryption. The IV need not be
 secret but should be different for each message and unpredictable.</P>
</DD>
<DT><A name="CIDR">CIDR</A></DT>
<DD><B>C</B>lassless<B> I</B>nter-<B>D</B>omain<B> R</B>outing, an
 addressing scheme used to describe networks not restricted to the old
 Class A, B, and C sizes. A CIDR block is written<VAR> address</VAR>/<VAR>
mask</VAR>, where<VAR> address</VAR> is a 32-bit Internet address. The
 first<VAR> mask</VAR> bits of<VAR> address</VAR> are part of the
 gateway address, while the remaining bits designate other host
 addresses. For example, the CIDR block 192.0.2.96/27 describes a
 network with gateway 192.0.2.96, hosts 192.0.2.96 through 192.0.2.126
 and broadcast 192.0.2.127.
<P>FreeS/WAN policy group files accept CIDR blocks of the format<VAR>
 address</VAR>/[<VAR>mask</VAR>], where<VAR> address</VAR> may take the
 form<VAR> name.domain.tld</VAR>. An absent<VAR> mask</VAR> is assumed
 to be /32.</P>
</DD>
<DT>Certification Authority</DT>
<DD>see<A href="#CA"> CA</A></DD>
<DT><A name="challenge">Challenge-response authentication</A></DT>
<DD>An<A href="#authentication"> authentication</A> system in which one
 player generates a<A href="#random"> random number</A>, encrypts it and
 sends the result as a challenge. The other player decrypts and sends
 back the result. If the result is correct, that proves to the first
 player that the second player knew the appropriate secret, required for
 the decryption. Variations on this technique exist using<A href="#public">
 public key</A> or<A href="#symmetric"> symmetric</A> cryptography. Some
 provide two-way authentication, assuring each player of the other's
 identity.
<P>This is more secure than passwords against two simple attacks:</P>
<UL>
<LI>If cleartext passwords are sent across the wire (e.g. for telnet),
 an eavesdropper can grab them. The attacker may even be able to break
 into other systems if the user has chosen the same password for them.</LI>
<LI>If an encrypted password is sent, an attacker can record the
 encrypted form and use it later. This is called a replay attack.</LI>
</UL>
<P>A challenge-response system never sends a password, either cleartext
 or encrypted. An attacker cannot record the response to one challenge
 and use it as a response to a later challenge. The random number is
 different each time.</P>
<P>Of course an attacker might still try to break the cryptographic
 algorithm used, or the<A href="#random"> random number</A> generator.</P>
</DD>
<DT><A name="mode">Cipher Modes</A></DT>
<DD>Different ways of using a block cipher when encrypting multiple
 blocks.
<P>Four standard modes were defined for<A href="#DES"> DES</A> in<A href="#FIPS">
 FIPS</A> 81. They can actually be applied with any block cipher.</P>
<TABLE><TBODY></TBODY>
<TR><TD></TD><TD><A href="#ECB">ECB</A></TD><TD>Electronic CodeBook</TD><TD>
encrypt each block independently</TD></TR>
<TR><TD></TD><TD><A href="#CBC">CBC</A></TD><TD>Cipher Block Chaining
<BR></TD><TD>XOR previous block ciphertext into new block plaintext
 before encrypting new block</TD></TR>
<TR><TD></TD><TD>CFB</TD><TD>Cipher FeedBack</TD><TD></TD></TR>
<TR><TD></TD><TD>OFB</TD><TD>Output FeedBack</TD><TD></TD></TR>
</TABLE>
<P><A href="#IPSEC">IPsec</A> uses<A href="#CBC"> CBC</A> mode since
 this is only marginally slower than<A href="#ECB"> ECB</A> and is more
 secure. In ECB mode the same plaintext always encrypts to the same
 ciphertext, unless the key is changed. In CBC mode, this does not
 occur.</P>
<P>Various other modes are also possible, but none of them are used in
 IPsec.</P>
</DD>
<DT><A name="ciphertext">Ciphertext</A></DT>
<DD>The encrypted output of a cipher, as opposed to the unencrypted<A href="#plaintext">
 plaintext</A> input.</DD>
<DT><A href="http://www.cisco.com">Cisco</A></DT>
<DD>A vendor of routers, hubs and related products. Their IPsec products
 interoperate with Linux FreeS/WAN; see our<A href="#cisco"> interop</A>
 section.</DD>
<DT><A name="client">Client</A></DT>
<DD>This term has at least two distinct uses in discussing IPsec:
<UL>
<LI>The<STRONG> clients of an IPsec gateway</STRONG> are the machines it
 protects, typically on one or more subnets behind the gateway. In this
 usage, all the machines on an office network are clients of that
 office's IPsec gateway. Laptop or home machines connecting to the
 office, however, are<EM> not</EM> clients of that gateway. They are
 remote gateways, running the other end of an IPsec connection. Each of
 them is also its own client.</LI>
<LI><STRONG>IPsec client software</STRONG> is used to describe software
 which runs on various standalone machines to let them connect to IPsec
 networks. In this usage, a laptop or home machine connecting to the
 office is a client, and the office gateway is the server.</LI>
</UL>
<P>We generally use the term in the first sense. Vendors of Windows
 IPsec solutions often use it in the second. See this<A href="interop.html#client.server">
 discussion</A>.</P>
</DD>
<DT><A name="cc">Common Criteria</A></DT>
<DD>A set of international security classifications which are replacing
 the old US<A href="#rainbow"> Rainbow Book</A> standards and similar
 standards in other countries.
<P>Web references include this<A href="http://csrc.nist.gov/cc"> US
 government site</A> and this<A href="http://www.commoncriteria.org">
 global home page</A>.</P>
</DD>
<DT>Conventional cryptography</DT>
<DD>See<A href="#symmetric"> symmetric cryptography</A></DD>
<DT><A name="collision">Collision resistance</A></DT>
<DD>The property of a<A href="#digest"> message digest</A> algorithm
 which makes it hard for an attacker to find or construct two inputs
 which hash to the same output.</DD>
<DT>Copyleft</DT>
<DD>see GNU<A href="#GPL"> General Public License</A></DD>
<DT><A name="CSE">CSE</A></DT>
<DD><A href="http://www.cse-cst.gc.ca/">Communications Security
 Establishment</A>, the Canadian organisation for<A href="#SIGINT">
 signals intelligence</A>.</DD>
<DT><A name="D">D</A></DT>
<DT><A name="DARPA">DARPA (sometimes just ARPA)</A></DT>
<DD>The US government's<B> D</B>efense<B> A</B>dvanced<B> R</B>esearch<B>
 P</B>rojects<B> A</B>gency. Projects they have funded over the years
 have included the Arpanet which evolved into the Internet, the TCP/IP
 protocol suite (as a replacement for the original Arpanet suite), the
 Berkeley 4.x BSD Unix projects, and<A href="#SDNS"> Secure DNS</A>.
<P>For current information, see their<A href="http://www.darpa.mil/ito">
 web site</A>.</P>
</DD>
<DT><A name="DOS">Denial of service (DoS) attack</A></DT>
<DD>An attack that aims at denying some service to legitimate users of a
 system, rather than providing a service to the attacker.
<UL>
<LI>One variant is a flooding attack, overwhelming the system with too
 many packets, to much email, or whatever.</LI>
<LI>A closely related variant is a resource exhaustion attack. For
 example, consider a &quot;TCP SYN flood&quot; attack. Setting up a TCP connection
 involves a three-packet exchange:
<UL>
<LI>Initiator: Connection please (SYN)</LI>
<LI>Responder: OK (ACK)</LI>
<LI>Initiator: OK here too</LI>
</UL>
<P>If the attacker puts bogus source information in the first packet,
 such that the second is never delivered, the responder may wait a long
 time for the third to come back. If responder has already allocated
 memory for the connection data structures, and if many of these bogus
 packets arrive, the responder may run out of memory.</P>
</LI>
<LI>Another variant is to feed the system undigestible data, hoping to
 make it sick. For example, IP packets are limited in size to 64K bytes
 and a fragment carries information on where it starts within that 64K
 and how long it is. The &quot;ping of death&quot; delivers fragments that say,
 for example, that they start at 60K and are 20K long. Attempting to
 re-assemble these without checking for overflow can be fatal.</LI>
</UL>
<P>The two example attacks discussed were both quite effective when
 first discovered, capable of crashing or disabling many operating
 systems. They were also well-publicised, and today far fewer systems
 are vulnerable to them.</P>
</DD>
<DT><A name="DES">DES</A></DT>
<DD>The<B> D</B>ata<B> E</B>ncryption<B> S</B>tandard, a<A href="#block">
 block cipher</A> with 64-bit blocks and a 56-bit key. Probably the most
 widely used<A href="#symmetric"> symmetric cipher</A> ever devised. DES
 has been a US government standard for their own use (only for
 unclassified data), and for some regulated industries such as banking,
 since the late 70's. It is now being replaced by<A href="#AES"> AES</A>
.
<P><A href="#desnotsecure">DES is seriously insecure against current
 attacks.</A></P>
<P><A href="#FreeSWAN">Linux FreeS/WAN</A> does not include DES, even
 though the RFCs specify it.<B> We strongly recommend that single DES
 not be used.</B></P>
<P>See also<A href="#3DES"> 3DES</A> and<A href="#DESX"> DESX</A>,
 stronger ciphers based on DES.</P>
</DD>
<DT><A name="DESX">DESX</A></DT>
<DD>An improved<A href="#DES"> DES</A> suggested by Ron Rivest of RSA
 Data Security. It XORs extra key material into the text before and
 after applying the DES cipher.
<P>This is not required by the<A href="#IPSEC"> IPsec</A> RFCs and not
 currently used in<A href="#FreeSWAN"> Linux FreeS/WAN</A>. DESX would
 be the easiest additional transform to add; there would be very little
 code to write. It would be much faster than 3DES and almost certainly
 more secure than DES. However, since it is not in the RFCs other IPsec
 implementations cannot be expected to have it.</P>
</DD>
<DT>DH</DT>
<DD>see<A href="#DH"> Diffie-Hellman</A></DD>
<DT><A name="DHCP">DHCP</A></DT>
<DD><STRONG>D</STRONG>ynamic<STRONG> H</STRONG>ost<STRONG> C</STRONG>
onfiguration<STRONG> P</STRONG>rotocol, a method of assigning<A href="#dynamic">
 dynamic IP addresses</A>, and providing additional information such as
 addresses of DNS servers and of gateways. See this<A href="http://www.dhcp.org">
 DHCP resource page.</A></DD>
<DT><A name="DH">Diffie-Hellman (DH) key exchange protocol</A></DT>
<DD>A protocol that allows two parties without any initial shared secret
 to create one in a manner immune to eavesdropping. Once they have done
 this, they can communicate privately by using that shared secret as a
 key for a block cipher or as the basis for key exchange.
<P>The protocol is secure against all<A href="#passive"> passive attacks</A>
, but it is not at all resistant to active<A href="#middle">
 man-in-the-middle attacks</A>. If a third party can impersonate Bob to
 Alice and vice versa, then no useful secret can be created.
 Authentication of the participants is a prerequisite for safe
 Diffie-Hellman key exchange. IPsec can use any of several<A href="#authentication">
 authentication</A> mechanisims. Those supported by FreeS/WAN are
 discussed in our<A href="#choose"> configuration</A> section.</P>
<P>The Diffie-Hellman key exchange is based on the<A href="#dlog">
 discrete logarithm</A> problem and is secure unless someone finds an
 efficient solution to that problem.</P>
<P>Given a prime<VAR> p</VAR> and generator<VAR> g</VAR> (explained
 under<A href="#dlog"> discrete log</A> below), Alice:</P>
<UL>
<LI>generates a random number<VAR> a</VAR></LI>
<LI>calculates<VAR> A = g^a modulo p</VAR></LI>
<LI>sends<VAR> A</VAR> to Bob</LI>
</UL>
<P>Meanwhile Bob:</P>
<UL>
<LI>generates a random number<VAR> b</VAR></LI>
<LI>calculates<VAR> B = g^b modulo p</VAR></LI>
<LI>sends<VAR> B</VAR> to Alice</LI>
</UL>
<P>Now Alice and Bob can both calculate the shared secret<VAR> s =
 g^(ab)</VAR>. Alice knows<VAR> a</VAR> and<VAR> B</VAR>, so she
 calculates<VAR> s = B^a</VAR>. Bob knows<VAR> A</VAR> and<VAR> b</VAR>
 so he calculates<VAR> s = A^b</VAR>.</P>
<P>An eavesdropper will know<VAR> p</VAR> and<VAR> g</VAR> since these
 are made public, and can intercept<VAR> A</VAR> and<VAR> B</VAR> but,
 short of solving the<A href="#dlog"> discrete log</A> problem, these do
 not let him or her discover the secret<VAR> s</VAR>.</P>
</DD>
<DT><A name="signature">Digital signature</A></DT>
<DD>Sender:
<UL>
<LI>calculates a<A href="#digest"> message digest</A> of a document</LI>
<LI>encrypts the digest with his or her private key, using some<A href="#public">
 public key cryptosystem</A>.</LI>
<LI>attaches the encrypted digest to the document as a signature</LI>
</UL>
<P>Receiver:</P>
<UL>
<LI>calculates a digest of the document (not including the signature)</LI>
<LI>decrypts the signature with the signer's public key</LI>
<LI>verifies that the two results are identical</LI>
</UL>
<P>If the public-key system is secure and the verification succeeds,
 then the receiver knows</P>
<UL>
<LI>that the document was not altered between signing and verification</LI>
<LI>that the signer had access to the private key</LI>
</UL>
<P>Such an encrypted message digest can be treated as a signature since
 it cannot be created without<EM> both</EM> the document<EM> and</EM>
 the private key which only the sender should possess. The<A href="#legal">
 legal issues</A> are complex, but several countries are moving in the
 direction of legal recognition for digital signatures.</P>
</DD>
<DT><A name="dlog">discrete logarithm problem</A></DT>
<DD>The problem of finding logarithms in a finite field. Given a field
 defintion (such definitions always include some operation analogous to
 multiplication) and two numbers, a base and a target, find the power
 which the base must be raised to in order to yield the target.
<P>The discrete log problem is the basis of several cryptographic
 systems, including the<A href="#DH"> Diffie-Hellman</A> key exchange
 used in the<A href="#IKE"> IKE</A> protocol. The useful property is
 that exponentiation is relatively easy but the inverse operation,
 finding the logarithm, is hard. The cryptosystems are designed so that
 the user does only easy operations (exponentiation in the field) but an
 attacker must solve the hard problem (discrete log) to crack the
 system.</P>
<P>There are several variants of the problem for different types of
 field. The IKE/Oakley key determination protocol uses two variants,
 either over a field modulo a prime or over a field defined by an
 elliptic curve. We give an example modulo a prime below. For the
 elliptic curve version, consult an advanced text such as<A href="#handbook">
 Handbook of Applied Cryptography</A>.</P>
<P>Given a prime<VAR> p</VAR>, a generator<VAR> g</VAR> for the field
 modulo that prime, and a number<VAR> x</VAR> in the field, the problem
 is to find<VAR> y</VAR> such that<VAR> g^y = x</VAR>.</P>
<P>For example, let p = 13. The field is then the integers from 0 to 12.
 Any integer equals one of these modulo 13. That is, the remainder when
 any integer is divided by 13 must be one of these.</P>
<P>2 is a generator for this field. That is, the powers of two modulo 13
 run through all the non-zero numbers in the field. Modulo 13 we have:</P>
<PRE>          y      x
        2^0  ==  1
        2^1  ==  2
        2^2  ==  4
        2^3  ==  8
        2^4  ==  3 that is, the remainder from 16/13 is 3
        2^5  ==  6          the remainder from 32/13 is 6
        2^6  == 12 and so on
        2^7  == 11
        2^8  ==  9
        2^9  ==  5
        2^10 == 10
        2^11 ==  7
        2^12 ==  1</PRE>
<P>Exponentiation in such a field is not difficult. Given, say,<NOBR><VAR>
 y = 11</VAR>,calculating<NOBR><VAR> x = 7</VAR>is straightforward. One
 method is just to calculate<NOBR><VAR> 2^11 = 2048</VAR>,then<NOBR><VAR>
 2048 mod 13 == 7</VAR>.When the field is modulo a large prime (say a
 few 100 digits) you need a silghtly cleverer method and even that is
 moderately expensive in computer time, but the calculation is still not
 problematic in any basic way.</P>
<P>The discrete log problem is the reverse. In our example, given<NOBR><VAR>
 x = 7</VAR>,find the logarithm<NOBR><VAR> y = 11</VAR>.When the field
 is modulo a large prime (or is based on a suitable elliptic curve),
 this is indeed problematic. No solution method that is not
 catastrophically expensive is known. Quite a few mathematicians have
 tackled this problem. No efficient method has been found and
 mathematicians do not expect that one will be. It seems likely no
 efficient solution to either of the main variants the discrete log
 problem exists.</P>
<P>Note, however, that no-one has proven such methods do not exist. If a
 solution to either variant were found, the security of any crypto
 system using that variant would be destroyed. This is one reason<A href="#IKE">
 IKE</A> supports two variants. If one is broken, we can switch to the
 other.</P>
</DD>
<DT><A name="discretionary">discretionary access control</A></DT>
<DD>access control mechanisms controlled by the user, for example Unix
 rwx file permissions. These contrast with<A href="#mandatory">
 mandatory access controls</A>.</DD>
<DT><A name="DNS">DNS</A></DT>
<DD><B>D</B>omain<B> N</B>ame<B> S</B>ervice, a distributed database
 through which names are associated with numeric addresses and other
 information in the Internet Protocol Suite. See also the<A href="#dns.background">
 DNS background</A> section of our documentation.</DD>
<DT>DOS attack</DT>
<DD>see<A href="#DOS"> Denial Of Service</A> attack</DD>
<DT><A name="dynamic">dynamic IP address</A></DT>
<DD>an IP address which is automatically assigned, either by<A href="#DHCP">
 DHCP</A> or by some protocol such as<A href="#PPP"> PPP</A> or<A href="#PPPoE">
 PPPoE</A> which the machine uses to connect to the Internet. This is
 the opposite of a<A href="#static"> static IP address</A>, pre-set on
 the machine itself.</DD>
<DT><A name="E">E</A></DT>
<DT><A name="EAR">EAR</A></DT>
<DD>The US government's<B> E</B>xport<B> A</B>dministration<B> R</B>
egulations, administered by the<A href="#BXA"> Bureau of Export
 Administration</A>. These have replaced the earlier<A href="#ITAR">
 ITAR</A> regulations as the controls on export of cryptography.</DD>
<DT><A name="ECB">ECB mode</A></DT>
<DD><B>E</B>lectronic<B> C</B>ode<B>B</B>ook mode, the simplest way to
 use a block cipher. See<A href="#mode"> Cipher Modes</A>.</DD>
<DT><A name="EDE">EDE</A></DT>
<DD>The sequence of operations normally used in either the three-key
 variant of<A href="#3DES"> triple DES</A> used in<A href="#IPSEC">
 IPsec</A> or the<A href="#2key"> two-key</A> variant used in some other
 systems.
<P>The sequence is:</P>
<UL>
<LI><B>E</B>ncrypt with key1</LI>
<LI><B>D</B>ecrypt with key2</LI>
<LI><B>E</B>ncrypt with key3</LI>
</UL>
<P>For the two-key version, key1=key3.</P>
<P>The &quot;advantage&quot; of this EDE order of operations is that it makes it
 simple to interoperate with older devices offering only single DES. Set
 key1=key2=key3 and you have the worst of both worlds, the overhead of
 triple DES with the &quot;security&quot; of single DES. Since both the<A href="#desnotsecure">
 security of single DES</A> and the overheads of triple DES are
 seriously inferior to many other ciphers, this is a spectacularly
 dubious &quot;advantage&quot;.</P>
</DD>
<DT><A name="Entrust">Entrust</A></DT>
<DD>A Canadian company offerring enterprise<A href="#PKI"> PKI</A>
 products using<A href="#CAST128"> CAST-128</A> symmetric crypto,<A href="#RSA">
 RSA</A> public key and<A href="#X509"> X.509</A> directories.<A href="http://www.entrust.com">
 Web site</A></DD>
<DT><A name="EFF">EFF</A></DT>
<DD><A href="http://www.eff.org">Electronic Frontier Foundation</A>, an
 advocacy group for civil rights in cyberspace.</DD>
<DT><A name="encryption">Encryption</A></DT>
<DD>Techniques for converting a readable message (<A href="#plaintext">
plaintext</A>) into apparently random material (<A href="#ciphertext">
ciphertext</A>) which cannot be read if intercepted. A key is required
 to read the message.
<P>Major variants include<A href="#symmetric"> symmetric</A> encryption
 in which sender and receiver use the same secret key and<A href="#public">
 public key</A> methods in which the sender uses one of a matched pair
 of keys and the receiver uses the other. Many current systems,
 including<A href="#IPSEC"> IPsec</A>, are<A href="#hybrid"> hybrids</A>
 combining the two techniques.</P>
</DD>
<DT><A name="ESP">ESP</A></DT>
<DD><B>E</B>ncapsulated<B> S</B>ecurity<B> P</B>ayload, the<A href="#IPSEC">
 IPsec</A> protocol which provides<A href="#encryption"> encryption</A>.
 It can also provide<A href="#authentication"> authentication</A>
 service and may be used with null encryption (which we do not
 recommend). For details see our<A href="#ESP.ipsec"> IPsec</A> document
 and/or RFC 2406.</DD>
<DT><A name="#extruded">Extruded subnet</A></DT>
<DD>A situation in which something IP sees as one network is actually in
 two or more places.
<P>For example, the Internet may route all traffic for a particular
 company to that firm's corporate gateway. It then becomes the company's
 problem to get packets to various machines on their<A href="#subnet">
 subnets</A> in various departments. They may decide to treat a branch
 office like a subnet, giving it IP addresses &quot;on&quot; their corporate net.
 This becomes an extruded subnet.</P>
<P>Packets bound for it are delivered to the corporate gateway, since as
 far as the outside world is concerned, that subnet is part of the
 corporate network. However, instead of going onto the corporate LAN (as
 they would for, say, the accounting department) they are then
 encapsulated and sent back onto the Internet for delivery to the branch
 office.</P>
<P>For information on doing this with Linux FreeS/WAN, look in our<A href="#extruded.config">
 advanced configuration</A> section.</P>
</DD>
<DT>Exhaustive search</DT>
<DD>See<A href="#brute"> brute force attack</A>.</DD>
<DT><A name="F">F</A></DT>
<DT><A name="FIPS">FIPS</A></DT>
<DD><B>F</B>ederal<B> I</B>nformation<B> P</B>rocessing<B> S</B>tandard,
 the US government's standards for products it buys. These are issued by<A
href="#NIST"> NIST</A>. Among other things,<A href="#DES"> DES</A> and<A href="#SHA">
 SHA</A> are defined in FIPS documents. NIST have a<A href="http://www.itl.nist.gov/div897/pubs">
 FIPS home page</A>.</DD>
<DT><A name="FSF">Free Software Foundation (FSF)</A></DT>
<DD>An organisation to promote free software, free in the sense of these
 quotes from their web pages</DD>
<DD><BLOCKQUOTE> &quot;Free software&quot; is a matter of liberty, not price. To
 understand the concept, you should think of &quot;free speech&quot;, not &quot;free
 beer.&quot;
<P>&quot;Free software&quot; refers to the users' freedom to run, copy,
 distribute, study, change and improve the software.</P>
</BLOCKQUOTE>
<P>See also<A href="#GNU"> GNU</A>,<A href="#GPL"> GNU General Public
 License</A>, and<A href="http://www.fsf.org"> the FSF site</A>.</P>
</DD>
<DT>FreeS/WAN</DT>
<DD>see<A href="#FreeSWAN"> Linux FreeS/WAN</A></DD>
<DT><A name="fullnet">Fullnet</A></DT>
<DD>The CIDR block containing all IPs of its IP version. The<A HREF="#IPv4">
 IPv4</A> fullnet is written 0.0.0.0/0. Also known as &quot;all&quot; and
 &quot;default&quot;, fullnet may be used in a routing table to specify a default
 route, and in a FreeS/WAN<A HREF="#policygroups"> policy group</A> file
 to specify a default IPsec policy.</DD>
<DT>FSF</DT>
<DD>see<A href="#FSF"> Free software Foundation</A></DD>
<DT><A name="G">G</A></DT>
<DT><A name="GCHQ">GCHQ</A></DT>
<DD><A href="http://www.gchq.gov.uk">Government Communications
 Headquarters</A>, the British organisation for<A href="#SIGINT">
 signals intelligence</A>.</DD>
<DT>generator of a prime field</DT>
<DD>see<A href="#dlog"> discrete logarithm problem</A></DD>
<DT><A name="GILC">GILC</A></DT>
<DD><A href="http://www.gilc.org">Global Internet Liberty Campaign</A>,
 an international organisation advocating, among other things, free
 availability of cryptography. They have a<A href="http://www.gilc.org/crypto/wassenaar">
 campaign</A> to remove cryptographic software from the<A href="#Wassenaar.gloss">
 Wassenaar Arrangement</A>.</DD>
<DT>Global Internet Liberty Campaign</DT>
<DD>see<A href="#GILC"> GILC</A>.</DD>
<DT><A name="GTR">Global Trust Register</A></DT>
<DD>An attempt to create something like a<A href="#rootCA"> root CA</A>
 for<A href="#PGP"> PGP</A> by publishing both<A href="#GTR"> as a book</A>
 and<A href="http://www.cl.cam.ac.uk/Research/Security/Trust-Register">
 on the web</A> the fingerprints of a set of verified keys for
 well-known users and organisations.</DD>
<DT><A name="GMP">GMP</A></DT>
<DD>The<B> G</B>NU<B> M</B>ulti-<B>P</B>recision library code, used in<A href="#FreeSWAN">
 Linux FreeS/WAN</A> by<A href="#Pluto"> Pluto</A> for<A href="#public">
 public key</A> calculations. See the<A href="http://www.swox.com/gmp">
 GMP home page</A>.</DD>
<DT><A name="GNU">GNU</A></DT>
<DD><B>G</B>NU's<B> N</B>ot<B> U</B>nix, the<A href="#FSF"> Free
 Software Foundation's</A> project aimed at creating a free system with
 at least the capabilities of Unix.<A href="#Linux"> Linux</A> uses GNU
 utilities extensively.</DD>
<DT><A name="#GOST">GOST</A></DT>
<DD>a Soviet government standard<A href="#block"> block cipher</A>.<A href="#schneier">
 Applied Cryptography</A> has details.</DD>
<DT>GPG</DT>
<DD>see<A href="#GPG"> GNU Privacy Guard</A></DD>
<DT><A name="GPL">GNU General Public License</A>(GPL, copyleft)</DT>
<DD>The license developed by the<A href="#FSF"> Free Software Foundation</A>
 under which<A href="#Linux"> Linux</A>,<A href="#FreeSWAN"> Linux
 FreeS/WAN</A> and many other pieces of software are distributed. The
 license allows anyone to redistribute and modify the code, but forbids
 anyone from distributing executables without providing access to source
 code. For more details see the file<A href="../COPYING"> COPYING</A>
 included with GPLed source distributions, including ours, or<A href="http://www.fsf.org/copyleft/gpl.html">
 the GNU site's GPL page</A>.</DD>
<DT><A name="GPG">GNU Privacy Guard</A></DT>
<DD>An open source implementation of Open<A href="#PGP"> PGP</A> as
 defined in RFC 2440. See their<A href="http://www.gnupg.org"> web site</A>
</DD>
<DT>GPL</DT>
<DD>see<A href="#GPL"> GNU General Public License</A>.</DD>
<DT><A name="H">H</A></DT>
<DT><A name="hash">Hash</A></DT>
<DD>see<A href="#digest"> message digest</A></DD>
<DT><A name="HMAC">Hashed Message Authentication Code (HMAC)</A></DT>
<DD>using keyed<A href="#digest"> message digest</A> functions to
 authenticate a message. This differs from other uses of these
 functions:
<UL>
<LI>In normal usage, the hash function's internal variable are
 initialised in some standard way. Anyone can reproduce the hash to
 check that the message has not been altered.</LI>
<LI>For HMAC usage, you initialise the internal variables from the key.
 Only someone with the key can reproduce the hash. A successful check of
 the hash indicates not only that the message is unchanged but also that
 the creator knew the key.</LI>
</UL>
<P>The exact techniques used in<A href="#IPSEC"> IPsec</A> are defined
 in RFC 2104. They are referred to as HMAC-MD5-96 and HMAC-SHA-96
 because they output only 96 bits of the hash. This makes some attacks
 on the hash functions harder.</P>
</DD>
<DT>HMAC</DT>
<DD>see<A href="#HMAC"> Hashed Message Authentication Code</A></DD>
<DT>HMAC-MD5-96</DT>
<DD>see<A href="#HMAC"> Hashed Message Authentication Code</A></DD>
<DT>HMAC-SHA-96</DT>
<DD>see<A href="#HMAC"> Hashed Message Authentication Code</A></DD>
<DT><A name="hybrid">Hybrid cryptosystem</A></DT>
<DD>A system using both<A href="#public"> public key</A> and<A href="#symmetric">
 symmetric cipher</A> techniques. This works well. Public key methods
 provide key management and<A href="#signature"> digital signature</A>
 facilities which are not readily available using symmetric ciphers. The
 symmetric cipher, however, can do the bulk of the encryption work much
 more efficiently than public key methods.</DD>
<DT><A name="I">I</A></DT>
<DT><A name="IAB">IAB</A></DT>
<DD><A href="http://www.iab.org/iab">Internet Architecture Board</A>.</DD>
<DT><A name="ICMP.gloss">ICMP</A></DT>
<DD><STRONG>I</STRONG>nternet<STRONG> C</STRONG>ontrol<STRONG> M</STRONG>
essage<STRONG> P</STRONG>rotocol. This is used for various IP-connected
 devices to manage the network.</DD>
<DT><A name="IDEA">IDEA</A></DT>
<DD><B>I</B>nternational<B> D</B>ata<B> E</B>ncrypion<B> A</B>lgorithm,
 developed in Europe as an alternative to exportable American ciphers
 such as<A href="#DES"> DES</A> which were<A href="#desnotsecure"> too
 weak for serious use</A>. IDEA is a<A href="#block"> block cipher</A>
 using 64-bit blocks and 128-bit keys, and is used in products such as<A href="#PGP">
 PGP</A>.
<P>IDEA is not required by the<A href="#IPSEC"> IPsec</A> RFCs and not
 currently used in<A href="#FreeSWAN"> Linux FreeS/WAN</A>.</P>
<P>IDEA is patented and, with strictly limited exceptions for personal
 use, using it requires a license from<A href="http://www.ascom.com">
 Ascom</A>.</P>
</DD>
<DT><A name="IEEE">IEEE</A></DT>
<DD><A href="http://www.ieee.org">Institute of Electrical and Electronic
 Engineers</A>, a professional association which, among other things,
 sets some technical standards</DD>
<DT><A name="IESG">IESG</A></DT>
<DD><A href="http://www.iesg.org">Internet Engineering Steering Group</A>
.</DD>
<DT><A name="IETF">IETF</A></DT>
<DD><A href="http://www.ietf.org">Internet Engineering Task Force</A>,
 the umbrella organisation whose various working groups make most of the
 technical decisions for the Internet. The IETF<A href="http://www.ietf.org/html.charters/ipsec-charter.html">
 IPsec working group</A> wrote the<A href="#RFC"> RFCs</A> we are
 implementing.</DD>
<DT><A name="IKE">IKE</A></DT>
<DD><B>I</B>nternet<B> K</B>ey<B> E</B>xchange, based on the<A href="#DH">
 Diffie-Hellman</A> key exchange protocol. For details, see RFC 2409 and
 our<A href="ipsec.html"> IPsec</A> document. IKE is implemented in<A href="#FreeSWAN">
 Linux FreeS/WAN</A> by the<A href="#Pluto"> Pluto daemon</A>.</DD>
<DT>IKE v2</DT>
<DD>A proposed replacement for<A href="#IKE"> IKE</A>. There are other
 candidates, such as<A href="#JFK"> JFK</A>, and at time of writing
 (March 2002) the choice between them has not yet been made and does not
 appear imminent.</DD>
<DT><A name="iOE">iOE</A></DT>
<DD>See<A HREF="#initiate-only"> Initiate-only opportunistic encryption</A>
.</DD>
<DT><A name="IP">IP</A></DT>
<DD><B>I</B>nternet<B> P</B>rotocol.</DD>
<DT><A name="masq">IP masquerade</A></DT>
<DD>A mostly obsolete term for a method of allowing multiple machines to
 communicate over the Internet when only one IP address is available for
 their use. The more current term is Network Address Translation or<A href="#NAT.gloss">
 NAT</A>.</DD>
<DT><A name="IPng">IPng</A></DT>
<DD>&quot;IP the Next Generation&quot;, see<A href="#ipv6.gloss"> IPv6</A>.</DD>
<DT><A name="IPv4">IPv4</A></DT>
<DD>The current version of the<A href="#IP"> Internet protocol suite</A>
.</DD>
<DT><A name="ipv6.gloss">IPv6 (IPng)</A></DT>
<DD>Version six of the<A href="#IP"> Internet protocol suite</A>,
 currently being developed. It will replace the current<A href="#IPv4">
 version four</A>. IPv6 has<A href="#IPSEC"> IPsec</A> as a mandatory
 component.
<P>See this<A href="http://playground.sun.com/pub/ipng/html/ipng-main.html">
 web site</A> for more details, and our<A href="#ipv6"> compatibility</A>
 document for information on FreeS/WAN and the Linux implementation of
 IPv6.</P>
</DD>
<DT><A name="IPSEC">IPsec</A> or IPSEC</DT>
<DD><B>I</B>nternet<B> P</B>rotocol<B> SEC</B>urity, security functions
 (<A href="#authentication">authentication</A> and<A href="#encryption">
 encryption</A>) implemented at the IP level of the protocol stack. It
 is optional for<A href="#IPv4"> IPv4</A> and mandatory for<A href="#ipv6.gloss">
 IPv6</A>.
<P>This is the standard<A href="#FreeSWAN"> Linux FreeS/WAN</A> is
 implementing. For more details, see our<A href="ipsec.html"> IPsec
 Overview</A>. For the standards, see RFCs listed in our<A href="#RFC">
 RFCs document</A>.</P>
</DD>
<DT><A name="IPX">IPX</A></DT>
<DD>Novell's Netware protocol tunnelled over an IP link. Our<A href="#user.scripts">
 firewalls</A> document includes an example of using this through an
 IPsec tunnel.</DD>
<DT><A name="ISAKMP">ISAKMP</A></DT>
<DD><B>I</B>nternet<B> S</B>ecurity<B> A</B>ssociation and<B> K</B>ey<B>
 M</B>anagement<B> P</B>rotocol, defined in RFC 2408.</DD>
<DT><A name="ITAR">ITAR</A></DT>
<DD><B>I</B>nternational<B> T</B>raffic in<B> A</B>rms<B> R</B>
egulations, US regulations administered by the State Department which
 until recently limited export of, among other things, cryptographic
 technology and software. ITAR still exists, but the limits on
 cryptography have now been transferred to the<A href="#EAR"> Export
 Administration Regulations</A> under the Commerce Department's<A href="#BXA">
 Bureau of Export Administration</A>.</DD>
<DT>IV</DT>
<DD>see<A href="#IV"> Initialisation vector</A></DD>
<DT><A name="IV">Initialisation Vector (IV)</A></DT>
<DD>Some cipher<A href="#mode"> modes</A>, including the<A href="#CBC">
 CBC</A> mode which IPsec uses, require some extra data at the
 beginning. This data is called the initialisation vector. It need not
 be secret, but should be different for each message. Its function is to
 prevent messages which begin with the same text from encrypting to the
 same ciphertext. That might give an analyst an opening, so it is best
 prevented.</DD>
<DT><A name="initiate-only">Initiate-only opportunistic encryption (iOE)</A>
</DT>
<DD>A form of<A HREF="#carpediem"> opportunistic encryption</A> (OE) in
 which a host proposes opportunistic connections, but lacks the reverse
 DNS records necessary to support incoming opportunistic connection
 requests. Common among hosts on cable or pppoe connections where the
 system administrator does not have write access to the DNS reverse map
 for the host's external IP.
<P>Configuring for initiate-only opportunistic encryption is described
 in our<A href="#opp.client"> quickstart</A> document.</P>
</DD>
<DT><A name="J">J</A></DT>
<DT><A name="JFK">JFK</A></DT>
<DD><STRONG>J</STRONG>ust<STRONG> F</STRONG>ast<STRONG> K</STRONG>eying,
 a proposed simpler replacement for<A href="#IKE"> IKE.</A></DD>
<DT><A name="K">K</A></DT>
<DT><A name="kernel">Kernel</A></DT>
<DD>The basic part of an operating system (e.g. Linux) which controls
 the hardware and provides services to all other programs.
<P>In the Linux release numbering system, an even second digit as in 2.<STRONG>
2</STRONG>.x indicates a stable or production kernel while an odd number
 as in 2.<STRONG>3</STRONG>.x indicates an experimental or development
 kernel. Most users should run a recent kernel version from the
 production series. The development kernels are primarily for people
 doing kernel development. Others should consider using development
 kernels only if they have an urgent need for some feature not yet
 available in production kernels.</P>
</DD>
<DT>Keyed message digest</DT>
<DD>See<A href="#HMAC"> HMAC</A>.</DD>
<DT>Key length</DT>
<DD>see<A href="#brute"> brute force attack</A></DD>
<DT><A name="KLIPS">KLIPS</A></DT>
<DD><B>K</B>erne<B>l</B><B> IP</B><B> S</B>ecurity, the<A href="#FreeSWAN">
 Linux FreeS/WAN</A> project's changes to the<A href="#Linux"> Linux</A>
 kernel to support the<A href="#IPSEC"> IPsec</A> protocols.</DD>
<DT><A name="L">L</A></DT>
<DT><A name="LDAP">LDAP</A></DT>
<DD><B>L</B>ightweight<B> D</B>irectory<B> A</B>ccess<B> P</B>rotocol,
 defined in RFCs 1777 and 1778, a method of accessing information stored
 in directories. LDAP is used by several<A href="#PKI"> PKI</A>
 implementations, often with X.501 directories and<A href="#X509"> X.509</A>
 certificates. It may also be used by<A href="#IPSEC"> IPsec</A> to
 obtain key certifications from those PKIs. This is not yet implemented
 in<A href="#FreeSWAN"> Linux FreeS/WAN</A>.</DD>
<DT><A name="LIBDES">LIBDES</A></DT>
<DD>A publicly available library of<A href="#DES"> DES</A> code, written
 by Eric Young, which<A href="#FreeSWAN"> Linux FreeS/WAN</A> uses in
 both<A href="#KLIPS"> KLIPS</A> and<A href="#Pluto"> Pluto</A>.</DD>
<DT><A name="Linux">Linux</A></DT>
<DD>A freely available Unix-like operating system based on a kernel
 originally written for the Intel 386 architecture by (then) student
 Linus Torvalds. Once his 32-bit kernel was available, the<A href="#GNU">
 GNU</A> utilities made it a usable system and contributions from many
 others led to explosive growth.
<P>Today Linux is a complete Unix replacement available for several CPU
 architectures -- Intel, DEC/Compaq Alpha, Power PC, both 32-bit SPARC
 and the 64-bit UltraSPARC, SrongARM, . . . -- with support for multiple
 CPUs on some architectures.</P>
<P><A href="#FreeSWAN">Linux FreeS/WAN</A> is intended to run on all
 CPUs supported by Linux and is known to work on several. See our<A href="#CPUs">
 compatibility</A> section for a list.</P>
</DD>
<DT><A name="FreeSWAN">Linux FreeS/WAN</A></DT>
<DD>Our implementation of the<A href="#IPSEC"> IPsec</A> protocols,
 intended to be freely redistributable source code with<A href="#GPL"> a
 GNU GPL license</A> and no constraints under US or other<A href="#exlaw">
 export laws</A>. Linux FreeS/WAN is intended to interoperate with other<A
href="#IPSEC"> IPsec</A> implementations. The name is partly taken, with
 permission, from the<A href="#SWAN"> S/WAN</A> multi-vendor IPsec
 compatability effort. Linux FreeS/WAN has two major components,<A href="#KLIPS">
 KLIPS</A> (KerneL IPsec Support) and the<A href="#Pluto"> Pluto</A>
 daemon which manages the whole thing.
<P>See our<A href="ipsec.html"> IPsec section</A> for more detail. For
 the code see our<A href="http://freeswan.org"> primary site</A> or one
 of the mirror sites on<A href="#mirrors"> this list</A>.</P>
</DD>
<DT><A name="LSM">Linux Security Modules (LSM)</A></DT>
<DD>a project to create an interface in the Linux kernel that supports
 plug-in modules for various security policies.
<P>This allows multiple security projects to take different approaches
 to security enhancement without tying the kernel down to one particular
 approach. As I understand the history, several projects were pressing
 Linus to incorporate their changes, the various sets of changes were
 incompatible, and his answer was more-or-less &quot;a plague on all your
 houses; I'll give you an interface, but I won't incorporate anything&quot;.</P>
<P>It seems to be working. There is a fairly active<A href="http://mail.wirex.com/mailman/listinfo/linux-security-module">
 LSM mailing list</A>, and several projects are already using the
 interface.</P>
</DD>
<DT>LSM</DT>
<DD>see<A href="#LSM"> Linux Security Modules</A></DD>
<DT><A name="M">M</A></DT>
<DT><A name="list">Mailing list</A></DT>
<DD>The<A href="#FreeSWAN"> Linux FreeS/WAN</A> project has several
 public email lists for bug reports and software development
 discussions. See our document on<A href="mail.html"> mailing lists</A>.</DD>
<DT><A name="middle">Man-in-the-middle attack</A></DT>
<DD>An<A href="#active"> active attack</A> in which the attacker
 impersonates each of the legitimate players in a protocol to the other.
<P>For example, if<A href="#alicebob"> Alice and Bob</A> are negotiating
 a key via the<A href="#DH"> Diffie-Hellman</A> key agreement, and are
 not using<A href="#authentication"> authentication</A> to be certain
 they are talking to each other, then an attacker able to insert himself
 in the communication path can deceive both players.</P>
<P>Call the attacker Mallory. For Bob, he pretends to be Alice. For
 Alice, he pretends to be Bob. Two keys are then negotiated,
 Alice-to-Mallory and Bob-to-Mallory. Alice and Bob each think the key
 they have is Alice-to-Bob.</P>
<P>A message from Alice to Bob then goes to Mallory who decrypts it,
 reads it and/or saves a copy, re-encrypts using the Bob-to-Mallory key
 and sends it along to Bob. Bob decrypts successfully and sends a reply
 which Mallory decrypts, reads, re-encrypts and forwards to Alice.</P>
<P>To make this attack effective, Mallory must</P>
<UL>
<LI>subvert some part of the network in some way that lets him carry out
 the deception
<BR> possible targets: DNS, router, Alice or Bob's machine, mail server,
 ...</LI>
<LI>beat any authentication mechanism Alice and Bob use
<BR> strong authentication defeats the attack entirely; this is why<A href="#IKE">
 IKE</A> requires authentication</LI>
<LI>work in real time, delivering messages without introducing a delay
 large enough to alert the victims
<BR> not hard if Alice and Bob are using email; quite difficult in some
 situations.</LI>
</UL>
<P>If he manages it, however, it is devastating. He not only gets to
 read all the messages; he can alter messages, inject his own, forge
 anything he likes, . . . In fact, he controls the communication
 completely.</P>
</DD>
<DT><A name="mandatory">mandatory access control</A></DT>
<DD>access control mechanisims which are not settable by the user (see<A href="#discretionary">
 discretionary access control</A>), but are enforced by the system.
<P>For example, a document labelled &quot;secret, zebra&quot; might be readable
 only by someone with secret clearance working on Project Zebra.
 Ideally, the system will prevent any transfer outside those boundaries.
 For example, even if you can read it, you should not be able to e-mail
 it (unless the recipient is appropriately cleared) or print it (unless
 certain printers are authorised for that classification).</P>
<P>Mandatory access control is a required feature for some levels of<A href="#rainbow">
 Rainbow Book</A> or<A href="#cc"> Common Criteria</A> classification,
 but has not been widely used outside the military and government. There
 is a good discussion of the issues in Anderson's<A href="#anderson">
 Security Engineering</A>.</P>
<P>The<A href="#SElinux"> Security Enhanced Linux</A> project is adding
 mandatory access control to Linux.</P>
</DD>
<DT><A name="manual">Manual keying</A></DT>
<DD>An IPsec mode in which the keys are provided by the administrator.
 In FreeS/WAN, they are stored in /etc/ipsec.conf. The alternative,<A href="#auto">
 automatic keying</A>, is preferred in most cases. See this<A href="#man-auto">
 discussion</A>.</DD>
<DT><A name="MD4">MD4</A></DT>
<DD><A href="#digest">Message Digest Algorithm</A> Four from Ron Rivest
 of<A href="#RSAco"> RSA</A>. MD4 was widely used a few years ago, but
 is now considered obsolete. It has been replaced by its descendants<A href="#MD5">
 MD5</A> and<A href="#SHA"> SHA</A>.</DD>
<DT><A name="MD5">MD5</A></DT>
<DD><A href="#digest">Message Digest Algorithm</A> Five from Ron Rivest
 of<A href="#RSAco"> RSA</A>, an improved variant of his<A href="#MD4">
 MD4</A>. Like MD4, it produces a 128-bit hash. For details see RFC
 1321.
<P>MD5 is one of two message digest algorithms available in IPsec. The
 other is<A href="#SHA"> SHA</A>. SHA produces a longer hash and is
 therefore more resistant to<A href="#birthday"> birthday attacks</A>,
 but this is not a concern for IPsec. The<A href="#HMAC"> HMAC</A>
 method used in IPsec is secure even if the underlying hash is not
 particularly strong against this attack.</P>
<P>Hans Dobbertin found a weakness in MD5, and people often ask whether
 this means MD5 is unsafe for IPsec. It doesn't. The IPsec RFCs discuss
 Dobbertin's attack and conclude that it does not affect MD5 as used for
 HMAC in IPsec.</P>
</DD>
<DT><A name="meet">Meet-in-the-middle attack</A></DT>
<DD>A divide-and-conquer attack which breaks a cipher into two parts,
 works against each separately, and compares results. Probably the best
 known example is an attack on double DES. This applies in principle to
 any pair of block ciphers, e.g. to an encryption system using, say,
 CAST-128 and Blowfish, but we will describe it for double DES.
<P>Double DES encryption and decryption can be written:</P>
<PRE>        C = E(k2,E(k1,P))
        P = D(k1,D(k2,C))</PRE>
<P>Where C is ciphertext, P is plaintext, E is encryption, D is
 decryption, k1 is one key, and k2 is the other key. If we know a P, C
 pair, we can try and find the keys with a brute force attack, trying
 all possible k1, k2 pairs. Since each key is 56 bits, there are 2<SUP>
112</SUP> such pairs and this attack is painfully inefficient.</P>
<P>The meet-in-the middle attack re-writes the equations to calculate a
 middle value M:</P>
<PRE>        M = E(k1,P)
        M = D(k2,C)</PRE>
<P>Now we can try some large number of D(k2,C) decryptions with various
 values of k2 and store the results in a table. Then start doing E(k1,P)
 encryptions, checking each result to see if it is in the table.</P>
<P>With enough table space, this breaks double DES with<NOBR> 2<SUP>56</SUP>
 + 2<SUP>56</SUP> = 2<SUP>57</SUP>work. Against triple DES, you need<NOBR>
 2<SUP>56</SUP> + 2<SUP>112</SUP> ~= 2<SUP>112</SUP>.</P>
<P>The memory requirements for such attacks can be prohibitive, but
 there is a whole body of research literature on methods of reducing
 them.</P>
</DD>
<DT><A name="digest">Message Digest Algorithm</A></DT>
<DD>An algorithm which takes a message as input and produces a hash or
 digest of it, a fixed-length set of bits which depend on the message
 contents in some highly complex manner. Design criteria include making
 it extremely difficult for anyone to counterfeit a digest or to change
 a message without altering its digest. One essential property is<A href="#collision">
 collision resistance</A>. The main applications are in message<A href="#authentication">
 authentication</A> and<A href="#signature"> digital signature</A>
 schemes. Widely used algorithms include<A href="#MD5"> MD5</A> and<A href="#SHA">
 SHA</A>. In IPsec, message digests are used for<A href="#HMAC"> HMAC</A>
 authentication of packets.</DD>
<DT><A name="MTU">MTU</A></DT>
<DD><STRONG>M</STRONG>aximum<STRONG> T</STRONG>ransmission<STRONG> U</STRONG>
nit, the largest size of packet that can be sent over a link. This is
 determined by the underlying network, but must be taken account of at
 the IP level.
<P>IP packets, which can be up to 64K bytes each, must be packaged into
 lower-level packets of the appropriate size for the underlying
 network(s) and re-assembled on the other end. When a packet must pass
 over multiple networks, each with its own MTU, and many of the MTUs are
 unknown to the sender, this becomes a fairly complex problem. See<A href="#pathMTU">
 path MTU discovery</A> for details.</P>
<P>Often the MTU is a few hundred bytes on serial links and 1500 on
 Ethernet. There are, however, serial link protocols which use a larger
 MTU to avoid fragmentation at the ethernet/serial boundary, and newer
 (especially gigabit) Ethernet networks sometimes support much larger
 packets because these are more efficient in some applications.</P>
</DD>
<DT><A name="N">N</A></DT>
<DT><A name="NAI">NAI</A></DT>
<DD><A href="http://www.nai.com">Network Associates</A>, a conglomerate
 formed from<A href="#PGPI"> PGP Inc.</A>, TIS (Trusted Information
 Systems, a firewall vendor) and McAfee anti-virus products. Among other
 things, they offer an IPsec-based VPN product.</DD>
<DT><A name="NAT.gloss">NAT</A></DT>
<DD><B>N</B>etwork<B> A</B>ddress<B> T</B>ranslation, a process by which
 firewall machines may change the addresses on packets as they go
 through. For discussion, see our<A href="#nat.background"> background</A>
 section.</DD>
<DT><A name="NIST">NIST</A></DT>
<DD>The US<A href="http://www.nist.gov"> National Institute of Standards
 and Technology</A>, responsible for<A href="#FIPS"> FIPS standards</A>
 including<A href="#DES"> DES</A> and its replacement,<A href="#AES">
 AES</A>.</DD>
<DT><A name="nonce">Nonce</A></DT>
<DD>A<A href="#random"> random</A> value used in an<A href="#authentication">
 authentication</A> protocol.</DD>
<DT></DT>
<DT><A name="non-routable">Non-routable IP address</A></DT>
<DD>An IP address not normally allowed in the &quot;to&quot; or &quot;from&quot; IP address
 field header of IP packets.
<P>Almost invariably, the phrase &quot;non-routable address&quot; means one of the
 addresses reserved by RFC 1918 for private networks:</P>
<UL>
<LI>10.anything</LI>
<LI>172.x.anything with 16 &lt;= x &lt;= 31</LI>
<LI>192.168.anything</LI>
</UL>
<P>These addresses are commonly used on private networks, e.g. behind a
 Linux machines doing<A href="#masq"> IP masquerade</A>. Machines within
 the private network can address each other with these addresses. All
 packets going outside that network, however, have these addresses
 replaced before they reach the Internet.</P>
<P>If any packets using these addresses do leak out, they do not go far.
 Most routers automatically discard all such packets.</P>
<P>Various other addresses -- the 127.0.0.0/8 block reserved for local
 use, 0.0.0.0, various broadcast and network addresses -- cannot be
 routed over the Internet, but are not normally included in the meaning
 when the phrase &quot;non-routable address&quot; is used.</P>
</DD>
<DT><A name="NSA">NSA</A></DT>
<DD>The US<A href="http://www.nsa.gov"> National Security Agency</A>,
 the American organisation for<A href="#SIGINT"> signals intelligence</A>
, the protection of US government messages and the interception and
 analysis of other messages. For details, see Bamford's<A href="#puzzle">
 &quot;The Puzzle Palace&quot;</A>.
<P>Some<A href="http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB23/index.html">
 history of NSA</A> documents were declassified in response to a FOIA
 (Freedom of Information Act) request.</P>
</DD>
<DT><A name="O">O</A></DT>
<DT><A name="oakley">Oakley</A></DT>
<DD>A key determination protocol, defined in RFC 2412.</DD>
<DT>Oakley groups</DT>
<DD>The groups used as the basis of<A href="#DH"> Diffie-Hellman</A> key
 exchange in the Oakley protocol, and in<A href="#IKE"> IKE</A>. Four
 were defined in the original RFC, and a fifth has been<A href="http://www.lounge.org/ike_doi_errata.html">
 added since</A>.
<P>Linux FreeS/WAN currently supports the three groups based on finite
 fields modulo a prime (Groups 1, 2 and 5) and does not support the
 elliptic curve groups (3 and 4). For a description of the difference of
 the types, see<A href="#dlog"> discrete logarithms</A>.</P>
</DD>
<DT><A name="OTP">One time pad</A></DT>
<DD>A cipher in which the key is:
<UL>
<LI>as long as the total set of messages to be enciphered</LI>
<LI>absolutely<A href="#random"> random</A></LI>
<LI>never re-used</LI>
</UL>
<P>Given those three conditions, it can easily be proved that the cipher
 is perfectly secure, in the sense that an attacker with intercepted
 message in hand has no better chance of guessing the message than an
 attacker who has not intercepted the message and only knows the message
 length. No such proof exists for any other cipher.</P>
<P>There are, however, several problems with this &quot;perfect&quot; cipher.</P>
<P>First, it is<STRONG> wildly impractical</STRONG> for most
 applications. Key management is at best difficult, often completely
 impossible.</P>
<P>Second, it is<STRONG> extremely fragile</STRONG>. Small changes which
 violate the conditions listed above do not just weaken the cipher
 liitle. Quite often they destroy its security completely.</P>
<UL>
<LI>Re-using the pad weakens the cipher to the point where it can be
 broken with pencil and paper. With a computer, the attack is trivially
 easy.</LI>
<LI>Using<EM> anything</EM> less than truly<A href="#random"> random</A>
 numbers<EM> completely</EM> invalidates the security proof.</LI>
<LI>In particular, using computer-generated pseudo-random numbers may
 give an extremely weak cipher. It might also produce a good stream
 cipher, if the pseudo-random generator is both well-designed and
 properely seeded.</LI>
</UL>
<P>Marketing claims about the &quot;unbreakable&quot; security of various products
 which somewhat resemble one-time pads are common. Such claims are one
 of the surest signs of cryptographic<A href="#snake"> snake oil</A>;
 most systems marketed with such claims are worthless.</P>
<P>Finally, even if the system is implemented and used correctly, it is<STRONG>
 highly vulnerable to a substitution attack</STRONG>. If an attacker
 knows some plaintext and has an intercepted message, he can discover
 the pad.</P>
<UL>
<LI>This does not matter if the attacker is just a<A href="#passive">
 passive</A> eavesdropper. It gives him no plaintext he didn't already
 know and we don't care that he learns a pad which we will never re-use.</LI>
<LI>However, an<A href="#active"> active</A> attacker who knows the
 plaintext can recover the pad, then use it to encode with whatever he
 chooses. If he can get his version delivered instead of yours, this may
 be a disaster. If you send &quot;attack at dawn&quot;, the delivered message can
 be anything the same length -- perhaps &quot;retreat to east&quot; or &quot;shoot
 generals&quot;.</LI>
<LI>An active attacker with only a reasonable guess at the plaintext can
 try the same attack. If the guess is correct, this works and the
 attacker's bogus message is delivered. If the guess is wrong, a garbled
 message is delivered.</LI>
</UL>
<P>In general then, despite its theoretical perfection, the one-time-pad
 has very limited practical application.</P>
<P>See also the<A href="http://pubweb.nfr.net/~mjr/pubs/otpfaq/"> one
 time pad FAQ</A>.</P>
</DD>
<DT><A name="carpediem">Opportunistic encryption (OE)</A></DT>
<DD>A situation in which any two IPsec-aware machines can secure their
 communications, without a pre-shared secret and without a common<A href="#PKI">
 PKI</A> or previous exchange of public keys. This is one of the goals
 of the Linux FreeS/WAN project, discussed in our<A href="#goals">
 introduction</A> section.
<P>Setting up for opportunistic encryption is described in our<A href="#quickstart">
 quickstart</A> document.</P>
</DD>
<DT><A name="responder">Opportunistic responder</A></DT>
<DD>A host which accepts, but does not initiate, requests for<A HREF="#carpediem">
 opportunistic encryption</A> (OE). An opportunistic responder has
 enabled OE in its<A HREF="#passive.OE"> passive</A> form (pOE) only. A
 web server or file server may be usefully set up as an opportunistic
 responder.
<P>Configuring passive OE is described in our<A href="#policygroups">
 policy groups</A> document.</P>
</DD>
<DT><A name="orange">Orange book</A></DT>
<DD>the most basic and best known of the US government's<A href="#rainbow">
 Rainbow Book</A> series of computer security standards.</DD>
<DT><A name="P">P</A></DT>
<DT><A name="P1363">P1363 standard</A></DT>
<DD>An<A href="#IEEE"> IEEE</A> standard for public key cryptography.<A href="http://grouper.ieee.org/groups/1363">
 Web page</A>.</DD>
<DT><A name="pOE">pOE</A></DT>
<DD>See<A href="#passive.OE"> Passive opportunistic encryption</A>.</DD>
<DT><A name="passive">Passive attack</A></DT>
<DD>An attack in which the attacker only eavesdrops and attempts to
 analyse intercepted messages, as opposed to an<A href="#active"> active
 attack</A> in which he diverts messages or generates his own.</DD>
<DT><A name="passive.OE">Passive opportunistic encryption (pOE)</A></DT>
<DD>A form of<A HREF="#carpediem"> opportunistic encryption</A> (OE) in
 which the host will accept opportunistic connection requests, but will
 not initiate such requests. A host which runs OE in its passive form
 only is known as an<A HREF="#responder"> opportunistic responder</A>.
<P>Configuring passive OE is described in our<A href="#policygroups">
 policy groups</A> document.</P>
</DD>
<DT><A name="pathMTU">Path MTU discovery</A></DT>
<DD>The process of discovering the largest packet size which all links
 on a path can handle without fragmentation -- that is, without any
 router having to break the packet up into smaller pieces to match the<A href="#MTU">
 MTU</A> of its outgoing link.
<P>This is done as follows:</P>
<UL>
<LI>originator sends the largest packets allowed by<A href="#MTU"> MTU</A>
 of the first link, setting the DF (<STRONG>d</STRONG>on't<STRONG> f</STRONG>
ragment) bit in the packet header</LI>
<LI>any router which cannot send the packet on (outgoing MTU is too
 small for it, and DF prevents fragmenting it to match) sends back an<A href="#ICMP.gloss">
 ICMP</A> packet reporting the problem</LI>
<LI>originator looks at ICMP message and tries a smaller size</LI>
<LI>eventually, you settle on a size that can pass all routers</LI>
<LI>thereafter, originator just sends that size and no-one has to
 fragment</LI>
</UL>
<P>Since this requires co-operation of many systems, and since the next
 packet may travel a different path, this is one of the trickier areas
 of IP programming. Bugs that have shown up over the years have
 included:</P>
<UL>
<LI>malformed ICMP messages</LI>
<LI>hosts that ignore or mishandle these ICMP messages</LI>
<LI>firewalls blocking the ICMP messages so host does not see them</LI>
</UL>
<P>Since IPsec adds a header, it increases packet size and may require
 fragmentation even where incoming and outgoing MTU are equal.</P>
</DD>
<DT><A name="PFS">Perfect forward secrecy (PFS)</A></DT>
<DD>A property of systems such as<A href="#DH"> Diffie-Hellman</A> key
 exchange which use a long-term key (such as the shared secret in IKE)
 and generate short-term keys as required. If an attacker who acquires
 the long-term key<EM> provably</EM> can
<UL>
<LI><EM>neither</EM> read previous messages which he may have archived</LI>
<LI><EM>nor</EM> read future messages without performing additional
 successful attacks</LI>
</UL>
<P>then the system has PFS. The attacker needs the short-term keys in
 order to read the trafiic and merely having the long-term key does not
 allow him to infer those. Of course, it may allow him to conduct
 another attack (such as<A href="#middle"> man-in-the-middle</A>) which
 gives him some short-term keys, but he does not automatically get them
 just by acquiring the long-term key.</P>
<P>See also<A href="http://sandelman.ottawa.on.ca/ipsec/1996/08/msg00123.html">
 Phil Karn's definition</A>.</P>
</DD>
<DT>PFS</DT>
<DD>see Perfect Forward Secrecy</DD>
<DT><A name="PGP">PGP</A></DT>
<DD><B>P</B>retty<B> G</B>ood<B> P</B>rivacy, a personal encryption
 system for email based on public key technology, written by Phil
 Zimmerman.
<P>The 2.xx versions of PGP used the<A href="#RSA"> RSA</A> public key
 algorithm and used<A href="#IDEA"> IDEA</A> as the symmetric cipher.
 These versions are described in RFC 1991 and in<A href="#PGP">
 Garfinkel's book</A>. Since version 5, the products from<A href="#PGPI">
 PGP Inc</A>. have used<A href="#DH"> Diffie-Hellman</A> public key
 methods and<A href="#CAST128"> CAST-128</A> symmetric encryption. These
 can verify signatures from the 2.xx versions, but cannot exchange
 encryted messages with them.</P>
<P>An<A href="#IETF"> IETF</A> working group has issued RFC 2440 for an
 &quot;Open PGP&quot; standard, similar to the 5.x versions. PGP Inc. staff were
 among the authors. A free<A href="#GPG"> Gnu Privacy Guard</A> based on
 that standard is now available.</P>
<P>For more information on PGP, including how to obtain it, see our
 cryptography<A href="#tools"> links</A>.</P>
</DD>
<DT><A name="PGPI">PGP Inc.</A></DT>
<DD>A company founded by Zimmerman, the author of<A href="#PGP"> PGP</A>
, now a division of<A href="#NAI"> NAI</A>. See the<A href="http://www.pgp.com">
 corporate website</A>. Zimmerman left in 2001, and early in 2002 NAI
 announced that they would no longer sell PGP..
<P>Versions 6.5 and later of the PGP product include PGPnet, an IPsec
 client for Macintosh or for Windows 95/98/NT. See our<A href="interop.html#pgpnet">
 interoperation documen</A>t.</P>
</DD>
<DT><A name="photuris">Photuris</A></DT>
<DD>Another key negotiation protocol, an alternative to<A href="#IKE">
 IKE</A>, described in RFCs 2522 and 2523.</DD>
<DT><A name="PPP">PPP</A></DT>
<DD><B>P</B>oint-to-<B>P</B>oint<B> P</B>rotocol, originally a method of
 connecting over modems or serial lines, but see also PPPoE.</DD>
<DT><A name="PPPoE">PPPoE</A></DT>
<DD><B>PPP</B><B> o</B>ver<B> E</B>thernet, a somewhat odd protocol that
 makes Ethernet look like a point-to-point serial link. It is widely
 used for cable or ADSL Internet services, apparently mainly because it
 lets the providers use access control and address assignmment
 mechanisms developed for dialup networks.<A href="http://www.roaringpenguin.com">
 Roaring Penguin</A> provide a widely used Linux implementation.</DD>
<DT><A name="PPTP">PPTP</A></DT>
<DD><B>P</B>oint-to-<B>P</B>oint<B> T</B>unneling<B> P</B>rotocol, used
 in some Microsoft VPN implementations. Papers discussing weaknesses in
 it are on<A href="http://www.counterpane.com/publish.html">
 counterpane.com</A>. It is now largely obsolete, replaced by L2TP.</DD>
<DT><A name="PKI">PKI</A></DT>
<DD><B>P</B>ublic<B> K</B>ey<B> I</B>nfrastructure, the things an
 organisation or community needs to set up in order to make<A href="#public">
 public key</A> cryptographic technology a standard part of their
 operating procedures.
<P>There are several PKI products on the market. Typically they use a
 hierarchy of<A href="#CA"> Certification Authorities (CAs)</A>. Often
 they use<A href="#LDAP"> LDAP</A> access to<A href="#X509"> X.509</A>
 directories to implement this.</P>
<P>See<A href="#web"> Web of Trust</A> for a different sort of
 infrastructure.</P>
</DD>
<DT><A name="PKIX">PKIX</A></DT>
<DD><B>PKI</B> e<B>X</B>change, an<A href="#IETF"> IETF</A> standard
 that allows<A href="#PKI"> PKI</A>s to talk to each other.
<P>This is required, for example, when users of a corporate PKI need to
 communicate with people at client, supplier or government
 organisations, any of which may have a different PKI in place. I should
 be able to talk to you securely whenever:</P>
<UL>
<LI>your organisation and mine each have a PKI in place</LI>
<LI>you and I are each set up to use those PKIs</LI>
<LI>the two PKIs speak PKIX</LI>
<LI>the configuration allows the conversation</LI>
</UL>
<P>At time of writing (March 1999), this is not yet widely implemented
 but is under quite active development by several groups.</P>
</DD>
<DT><A name="plaintext">Plaintext</A></DT>
<DD>The unencrypted input to a cipher, as opposed to the encrypted<A href="#ciphertext">
 ciphertext</A> output.</DD>
<DT><A name="Pluto">Pluto</A></DT>
<DD>The<A href="#FreeSWAN"> Linux FreeS/WAN</A> daemon which handles key
 exchange via the<A href="#IKE"> IKE</A> protocol, connection
 negotiation, and other higher-level tasks. Pluto calls the<A href="#KLIPS">
 KLIPS</A> kernel code as required. For details, see the manual page
 ipsec_pluto(8).</DD>
<DT><A name="public">Public Key Cryptography</A></DT>
<DD>In public key cryptography, keys are created in matched pairs.
 Encrypt with one half of a pair and only the matching other half can
 decrypt it. This contrasts with<A href="#symmetric"> symmetric or
 secret key cryptography</A> in which a single key known to both parties
 is used for both encryption and decryption.
<P>One half of each pair, called the public key, is made public. The
 other half, called the private key, is kept secret. Messages can then
 be sent by anyone who knows the public key to the holder of the private
 key. Encrypt with the public key and you know that only someone with
 the matching private key can decrypt.</P>
<P>Public key techniques can be used to create<A href="#signature">
 digital signatures</A> and to deal with key management issues, perhaps
 the hardest part of effective deployment of<A href="#symmetric">
 symmetric ciphers</A>. The resulting<A href="#hybrid"> hybrid
 cryptosystems</A> use public key methods to manage keys for symmetric
 ciphers.</P>
<P>Many organisations are currently creating<A href="#PKI"> PKIs, public
 key infrastructures</A> to make these benefits widely available.</P>
</DD>
<DT>Public Key Infrastructure</DT>
<DD>see<A href="#PKI"> PKI</A></DD>
<DT><A name="Q">Q</A></DT>
<DT><A name="R">R</A></DT>
<DT><A name="rainbow">Rainbow books</A></DT>
<DD>A set of US government standards for evaluation of &quot;trusted computer
 systems&quot;, of which the best known was the<A href="#orange"> Orange Book</A>
. One fairly often hears references to &quot;C2 security&quot; or a product
 &quot;evaluated at B1&quot;. The Rainbow books define the standards referred to
 in those comments.
<P>See this<A href="http://www.fas.org/irp/nsa/rainbow.htm"> reference
 page</A>.</P>
<P>The Rainbow books are now mainly obsolete, replaced by the
 international<A href="#cc"> Common Criteria</A> standards.</P>
</DD>
<DT><A name="random">Random</A></DT>
<DD>A remarkably tricky term, far too much so for me to attempt a
 definition here. Quite a few cryptosystems have been broken via attacks
 on weak random number generators, even when the rest of the system was
 sound.
<P>See<A href="http://nis.nsf.net/internet/documents/rfc/rfc1750.txt">
 RFC 1750</A> for the theory.</P>
<P>See the manual pages for<A href="manpage.d/ipsec_ranbits.8.html">
 ipsec_ranbits(8)</A> and ipsec_prng(3) for more on FreeS/WAN's use of
 randomness. Both depend on the random(4) device driver..</P>
<P>A couple of years ago, there was extensive mailing list discussion
 (archived<A href="http://www.openpgp.net/random/index.html"> here</A>
)of Linux /dev/random and FreeS/WAN. Since then, the design of the
 random(4) driver has changed considerably. Linux 2.4 kernels have the
 new driver..</P>
</DD>
<DT>Raptor</DT>
<DD>A firewall product for Windows NT offerring IPsec-based VPN
 services. Linux FreeS/WAN interoperates with Raptor; see our<A href="#raptor">
 interop</A> document for details. Raptor have recently merged with
 Axent.</DD>
<DT><A name="RC4">RC4</A></DT>
<DD><B>R</B>ivest<B> C</B>ipher four, designed by Ron Rivest of<A href="#RSAco">
 RSA</A> and widely used. Believed highly secure with adequate key
 length, but often implemented with inadequate key length to comply with
 export restrictions.</DD>
<DT><A name="RC6">RC6</A></DT>
<DD><B>R</B>ivest<B> C</B>ipher six,<A href="#RSAco"> RSA</A>'s<A href="#AES">
 AES</A> candidate cipher.</DD>
<DT><A name="replay">Replay attack</A></DT>
<DD>An attack in which the attacker records data and later replays it in
 an attempt to deceive the recipient.</DD>
<DT><A name="reverse">Reverse map</A></DT>
<DD>In<A href="#DNS"> DNS</A>, a table where IP addresses can be used as
 the key for lookups which return a system name and/or other
 information.</DD>
<DT>RFC</DT>
<DD><B>R</B>equest<B> F</B>or<B> C</B>omments, an Internet document.
 Some RFCs are just informative. Others are standards.
<P>Our list of<A href="#IPSEC"> IPsec</A> and other security-related
 RFCs is<A href="#RFC"> here</A>, along with information on methods of
 obtaining them.</P>
</DD>
<DT><A name="rijndael">Rijndael</A></DT>
<DD>a<A href="#block"> block cipher</A> designed by two Belgian
 cryptographers, winner of the US government's<A href="#AES"> AES</A>
 contest to pick a replacement for<A href="#DES"> DES</A>. See the<A href="http://www.esat.kuleuven.ac.be/~rijmen/rijndael">
 Rijndael home page</A>.</DD>
<DT><A name="RIPEMD">RIPEMD</A></DT>
<DD>A<A href="#digest"> message digest</A> algorithm. The current
 version is RIPEMD-160 which gives a 160-bit hash.</DD>
<DT><A name="rootCA">Root CA</A></DT>
<DD>The top level<A href="#CA"> Certification Authority</A> in a
 hierachy of such authorities.</DD>
<DT><A name="routable">Routable IP address</A></DT>
<DD>Most IP addresses can be used as &quot;to&quot; and &quot;from&quot; addresses in packet
 headers. These are the routable addresses; we expect routing to be
 possible for them. If we send a packet to one of them, we expect (in
 most cases; there are various complications) that it will be delivered
 if the address is in use and will cause an<A href="#ICMP.gloss"> ICMP</A>
 error packet to come back to us if not.
<P>There are also several classes of<A href="#non-routable">
 non-routable</A> IP addresses.</P>
</DD>
<DT><A name="RSA">RSA algorithm</A></DT>
<DD><B>R</B>ivest<B> S</B>hamir<B> A</B>dleman<A href="#public"> public
 key</A> algorithm, named for its three inventors. It is widely used and
 likely to become moreso since it became free of patent encumbrances in
 September 2000.
<P>RSA can be used to provide either<A href="#encryption"> encryption</A>
 or<A href="#signature"> digital signatures</A>. In IPsec, it is used
 only for signatures. These provide gateway-to-gateway<A href="#authentication">
 authentication</A> for<A href="#IKE"> IKE</A> negotiations.</P>
<P>For a full explanation of the algorithm, consult one of the standard
 references such as<A href="#schneier"> Applied Cryptography</A>. A
 simple explanation is:</P>
<P>The great 17th century French mathematician<A href="http://www-groups.dcs.st-andrews.ac.uk/~history/Mathematicians/Fermat.html">
 Fermat</A> proved that,</P>
<P>for any prime p and number x, 0 &lt;= x &lt; p:</P>
<PRE>        x^p == x         modulo p
        x^(p-1) == 1     modulo p, non-zero x
      </PRE>
<P>From this it follows that if we have a pair of primes p, q and two
 numbers e, d such that:</P>
<PRE>        ed == 1          modulo lcm( p-1, q-1)
      </PRE>
 where lcm() is least common multiple, then
<BR> for all x, 0 &lt;= x &lt; pq:
<PRE>      x^ed == x           modulo pq
      </PRE>
<P>So we construct such as set of numbers p, q, e, d and publish the
 product N=pq and e as the public key. Using c for<A href="#ciphertext">
 ciphertext</A> and i for the input<A href="#plaintext"> plaintext</A>,
 encryption is then:</P>
<PRE>        c = i^e           modulo N
      </PRE>
<P>An attacker cannot deduce i from the cyphertext c, short of either
 factoring N or solving the<A href="#dlog"> discrete logarithm</A>
 problem for this field. If p, q are large primes (hundreds or thousands
 of bits) no efficient solution to either problem is known.</P>
<P>The receiver, knowing the private key (N and d), can readily recover
 the plaintext p since:</P>
<PRE>        c^d == (i^e)^d    modulo N
            == i^ed       modulo N
            == i          modulo N
      </PRE>
<P>This gives an effective public key technique, with only a couple of
 problems. It uses a good deal of computer time, since calculations with
 large integers are not cheap, and there is no proof it is necessarily
 secure since no-one has proven either factoring or discrete log cannot
 be done efficiently. Quite a few good mathematicians have tried both
 problems, and no-one has announced success, but there is no proof they
 are insoluble.</P>
</DD>
<DT><A name="RSAco">RSA Data Security</A></DT>
<DD>A company founded by the inventors of the<A href="#RSA"> RSA</A>
 public key algorithm.</DD>
<DT><A name="S">S</A></DT>
<DT><A name="SA">SA</A></DT>
<DD><B>S</B>ecurity<B> A</B>ssociation, the channel negotiated by the
 higher levels of an<A href="#IPSEC"> IPsec</A> implementation (<A href="#IKE">
IKE</A>) and used by the lower (<A href="#ESP">ESP</A> and<A href="#AH">
 AH</A>). SAs are unidirectional; you need a pair of them for two-way
 communication.
<P>An SA is defined by three things -- the destination, the protocol (<A href="#AH">
AH</A> or<A href="#ESP">ESP</A>) and the<A href="SPI"> SPI</A>, security
 parameters index. It is used as an index to look up other things such
 as session keys and intialisation vectors.</P>
<P>For more detail, see our section on<A href="ipsec.html"> IPsec</A>
 and/or RFC 2401.</P>
</DD>
<DT><A name="SElinux">SE Linux</A></DT>
<DD><STRONG>S</STRONG>ecurity<STRONG> E</STRONG>nhanced Linux, an<A href="#NSA">
 NSA</A>-funded project to add<A href="#mandatory"> mandatory access
 control</A> to Linux. See the<A href="http://www.nsa.gov/selinux">
 project home page</A>.
<P>According to their web pages, this work will include extending
 mandatory access controls to IPsec tunnels.</P>
<P>Recent versions of SE Linux code use the<A href="#LSM"> Linux
 Security Module</A> interface.</P>
</DD>
<DT><A name="SDNS">Secure DNS</A></DT>
<DD>A version of the<A href="#DNS"> DNS or Domain Name Service</A>
 enhanced with authentication services. This is being designed by the<A href="#IETF">
 IETF</A> DNS security<A href="http://www.ietf.org/ids.by.wg/dnssec.html">
 working group</A>. Check the<A href="http://www.isc.org/bind.html">
 Internet Software Consortium</A> for information on implementation
 progress and for the latest version of<A href="#BIND"> BIND</A>.
 Another site has<A href="http://www.toad.com/~dnssec"> more information</A>
.
<P><A href="#IPSEC">IPsec</A> can use this plus<A href="#DH">
 Diffie-Hellman key exchange</A> to bootstrap itself. This allows<A href="#carpediem">
 opportunistic encryption</A>. Any pair of machines which can
 authenticate each other via DNS can communicate securely, without
 either a pre-existing shared secret or a shared<A href="#PKI"> PKI</A>.</P>
</DD>
<DT>Secret key cryptography</DT>
<DD>See<A href="#symmetric"> symmetric cryptography</A></DD>
<DT>Security Association</DT>
<DD>see<A href="#SA"> SA</A></DD>
<DT>Security Enhanced Linux</DT>
<DD>see<A href="#SElinux"> SE Linux</A></DD>
<DT><A name="sequence">Sequence number</A></DT>
<DD>A number added to a packet or message which indicates its position
 in a sequence of packets or messages. This provides some security
 against<A href="#replay"> replay attacks</A>.
<P>For<A href="#auto"> automatic keying</A> mode, the<A href="#IPSEC">
 IPsec</A> RFCs require that the sender generate sequence numbers for
 each packet, but leave it optional whether the receiver does anything
 with them.</P>
</DD>
<DT><A name="SHA">SHA</A></DT>
<DT>SHA-1</DT>
<DD><B>S</B>ecure<B> H</B>ash<B> A</B>lgorithm, a<A href="#digest">
 message digest algorithm</A> developed by the<A href="#NSA"> NSA</A>
 for use in the Digital Signature standard,<A href="#FIPS"> FIPS</A>
 number 186 from<A href="#NIST"> NIST</A>. SHA is an improved variant of<A
href="#MD4"> MD4</A> producing a 160-bit hash.
<P>SHA is one of two message digest algorithms available in IPsec. The
 other is<A href="#MD5"> MD5</A>. Some people do not trust SHA because
 it was developed by the<A href="#NSA"> NSA</A>. There is, as far as we
 know, no cryptographic evidence that SHA is untrustworthy, but this
 does not prevent that view from being strongly held.</P>
<P>The NSA made one small change after the release of the original SHA.
 They did not give reasons. Iit may be a defense against some attack
 they found and do not wish to disclose. Technically the modified
 algorithm should be called SHA-1, but since it has replaced the
 original algorithm in nearly all applications, it is generally just
 referred to as SHA..</P>
</DD>
<DT><A name="SHA-256">SHA-256</A></DT>
<DT>SHA-384</DT>
<DT>SHA-512</DT>
<DD>Newer variants of SHA designed to match the strength of the 128, 192
 and 256-bit keys of<A href="#AES"> AES</A>. The work to break an
 encryption algorithm's strength by<A href="#brute"> brute force</A> is
 2
<!--math xmlns="http://www.w3.org/1998/Math/MathML"-->

<!--msup-->

<!--mi-->
 keylength</(null)></(null)></(null)> operations but a<A href="birthday">
 birthday attack</A> on a hash needs only 2
<!--math xmlns="http://www.w3.org/1998/Math/MathML"-->

<!--msup-->

<!--mrow-->

<!--mi-->
 hashlength</(null)>
<!--mo-->
 /</(null)>
<!--mn-->

 2</(null)></(null)></(null)></(null)> , so as a general rule you need a
 hash twice the size of the key to get similar strength. SHA-256,
 SHA-384 and SHA-512 are designed to match the 128, 192 and 256-bit key
 sizes of AES, respectively.</DD>
<DT><A name="SIGINT">Signals intelligence (SIGINT)</A></DT>
<DD>Activities of government agencies from various nations aimed at
 protecting their own communications and reading those of others.
 Cryptography, cryptanalysis, wiretapping, interception and monitoring
 of various sorts of signals. The players include the American<A href="#NSA">
 NSA</A>, British<A href="#GCHQ"> GCHQ</A> and Canadian<A href="#CSE">
 CSE</A>.</DD>
<DT><A name="SKIP">SKIP</A></DT>
<DD><B>S</B>imple<B> K</B>ey management for<B> I</B>nternet<B> P</B>
rotocols, an alternative to<A href="#IKE"> IKE</A> developed by Sun and
 being marketed by their<A href="http://skip.incog.com"> Internet
 Commerce Group</A>.</DD>
<DT><A name="snake">Snake oil</A></DT>
<DD>Bogus cryptography. See the<A href="http://www.interhack.net/people/cmcurtin/snake-oil-faq.html">
 Snake Oil FAQ</A> or<A href="http://www.counterpane.com/crypto-gram-9902.html#snakeoil">
 this paper</A> by Schneier.</DD>
<DT><A name="SPI">SPI</A></DT>
<DD><B>S</B>ecurity<B> P</B>arameter<B> I</B>ndex, an index used within<A
href="#IPSEC"> IPsec</A> to keep connections distinct. A<A href="#SA">
 Security Association (SA)</A> is defined by destination, protocol and
 SPI. Without the SPI, two connections to the same gateway using the
 same protocol could not be distinguished.
<P>For more detail, see our<A href="ipsec.html"> IPsec</A> section
 and/or RFC 2401.</P>
</DD>
<DT><A name="SSH">SSH</A></DT>
<DD><B>S</B>ecure<B> SH</B>ell, an encrypting replacement for the
 insecure Berkeley commands whose names begin with &quot;r&quot; for &quot;remote&quot;:
 rsh, rlogin, etc.
<P>For more information on SSH, including how to obtain it, see our
 cryptography<A href="#tools"> links</A>.</P>
</DD>
<DT><A name="SSHco">SSH Communications Security</A></DT>
<DD>A company founded by the authors of<A href="#SSH"> SSH</A>. Offices
 are in<A href="http://www.ssh.fi"> Finland</A> and<A href="http://www.ipsec.com">
 California</A>. They have a toolkit for developers of IPsec
 applications.</DD>
<DT><A name="SSL">SSL</A></DT>
<DD><A href="http://home.netscape.com/eng/ssl3">Secure Sockets Layer</A>
, a set of encryption and authentication services for web browsers,
 developed by Netscape. Widely used in Internet commerce. Also known as<A
href="#TLS"> TLS</A>.</DD>
<DT>SSLeay</DT>
<DD>A free implementation of<A href="#SSL"> SSL</A> by Eric Young (eay)
 and others. Developed in Australia; not subject to US export controls.</DD>
<DT><A name="static">static IP address</A></DT>
<DD>an IP adddress which is pre-set on the machine itself, as opposed to
 a<A href="#dynamic"> dynamic address</A> which is assigned by a<A href="#DHCP">
 DHCP</A> server or obtained as part of the process of establishing a<A href="#PPP">
 PPP</A> or<A href="#PPPoE"> PPPoE</A> connection</DD>
<DT><A name="stream">Stream cipher</A></DT>
<DD>A<A href="#symmetric"> symmetric cipher</A> which produces a stream
 of output which can be combined (often using XOR or bytewise addition)
 with the plaintext to produce ciphertext. Contrasts with<A href="#block">
 block cipher</A>.
<P><A href="#IPSEC">IPsec</A> does not use stream ciphers. Their main
 application is link-level encryption, for example of voice, video or
 data streams on a wire or a radio signal.</P>
</DD>
<DT><A name="subnet">subnet</A></DT>
<DD>A group of IP addresses which are logically one network, typically
 (but not always) assigned to a group of physically connected machines.
 The range of addresses in a subnet is described using a subnet mask.
 See next entry.</DD>
<DT>subnet mask</DT>
<DD>A method of indicating the addresses included in a subnet. Here are
 two equivalent examples:
<UL>
<LI>101.101.101.0/24</LI>
<LI>101.101.101.0 with mask 255.255.255.0</LI>
</UL>
<P>The '24' is shorthand for a mask with the top 24 bits one and the
 rest zero. This is exactly the same as 255.255.255.0 which has three
 all-ones bytes and one all-zeros byte.</P>
<P>These indicate that, for this range of addresses, the top 24 bits are
 to be treated as naming a network (often referred to as &quot;the
 101.101.101.0/24 subnet&quot;) while most combinations of the low 8 bits can
 be used to designate machines on that network. Two addresses are
 reserved; 101.101.101.0 refers to the subnet rather than a specific
 machine while 101.101.101.255 is a broadcast address. 1 to 254 are
 available for machines.</P>
<P>It is common to find subnets arranged in a hierarchy. For example, a
 large company might have a /16 subnet and allocate /24 subnets within
 that to departments. An ISP might have a large subnet and allocate /26
 subnets (64 addresses, 62 usable) to business customers and /29 subnets
 (8 addresses, 6 usable) to residential clients.</P>
</DD>
<DT><A name="SWAN">S/WAN</A></DT>
<DD>Secure Wide Area Network, a project involving<A href="#RSAco"> RSA
 Data Security</A> and a number of other companies. The goal was to
 ensure that all their<A href="#IPSEC"> IPsec</A> implementations would
 interoperate so that their customers can communicate with each other
 securely.</DD>
<DT><A name="symmetric">Symmetric cryptography</A></DT>
<DD>Symmetric cryptography, also referred to as conventional or secret
 key cryptography, relies on a<EM> shared secret key</EM>, identical for
 sender and receiver. Sender encrypts with that key, receiver decrypts
 with it. The idea is that an eavesdropper without the key be unable to
 read the messages. There are two main types of symmetric cipher,<A href="#block">
 block ciphers</A> and<A href="#stream"> stream ciphers</A>.
<P>Symmetric cryptography contrasts with<A href="#public"> public key</A>
 or asymmetric systems where the two players use different keys.</P>
<P>The great difficulty in symmetric cryptography is, of course, key
 management. Sender and receiver<EM> must</EM> have identical keys and
 those keys<EM> must</EM> be kept secret from everyone else. Not too
 much of a problem if only two people are involved and they can
 conveniently meet privately or employ a trusted courier. Quite a
 problem, though, in other circumstances.</P>
<P>It gets much worse if there are many people. An application might be
 written to use only one key for communication among 100 people, for
 example, but there would be serious problems. Do you actually trust all
 of them that much? Do they trust each other that much? Should they?
 What is at risk if that key is compromised? How are you going to
 distribute that key to everyone without risking its secrecy? What do
 you do when one of them leaves the company? Will you even know?</P>
<P>On the other hand, if you need unique keys for every possible
 connection between a group of 100, then each user must have 99 keys.
 You need either 99*100/2 = 4950<EM> secure</EM> key exchanges between
 users or a central authority that<EM> securely</EM> distributes 100 key
 packets, each with a different set of 99 keys.</P>
<P>Either of these is possible, though tricky, for 100 users. Either
 becomes an administrative nightmare for larger numbers. Moreover, keys<EM>
 must</EM> be changed regularly, so the problem of key distribution
 comes up again and again. If you use the same key for many messages
 then an attacker has more text to work with in an attempt to crack that
 key. Moreover, one successful crack will give him or her the text of
 all those messages.</P>
<P>In short, the<EM> hardest part of conventional cryptography is key
 management</EM>. Today the standard solution is to build a<A href="#hybrid">
 hybrid system</A> using<A href="#public"> public key</A> techniques to
 manage keys.</P>
</DD>
<DT><A name="T">T</A></DT>
<DT><A name="TIS">TIS</A></DT>
<DD>Trusted Information Systems, a firewall vendor now part of<A href="#NAI">
 NAI</A>. Their Gauntlet product offers IPsec VPN services. TIS
 implemented the first version of<A href="#SDNS"> Secure DNS</A> on a<A href="#DARPA">
 DARPA</A> contract.</DD>
<DT><A name="TLS">TLS</A></DT>
<DD><B>T</B>ransport<B> L</B>ayer<B> S</B>ecurity, a newer name for<A href="#SSL">
 SSL</A>.</DD>
<DT><A name="TOS">TOS field</A></DT>
<DD>The<STRONG> T</STRONG>ype<STRONG> O</STRONG>f<STRONG> S</STRONG>
ervice field in an IP header, used to control qualkity of service
 routing.</DD>
<DT><A name="traffic">Traffic analysis</A></DT>
<DD>Deducing useful intelligence from patterns of message traffic,
 without breaking codes or reading the messages. In one case during
 World War II, the British guessed an attack was coming because all
 German radio traffic stopped. The &quot;radio silence&quot; order, intended to
 preserve security, actually gave the game away.
<P>In an industrial espionage situation, one might deduce something
 interesting just by knowing that company A and company B were talking,
 especially if one were able to tell which departments were involved, or
 if one already knew that A was looking for acquisitions and B was
 seeking funds for expansion.</P>
<P>In general, traffic analysis by itself is not very useful. However,
 in the context of a larger intelligence effort where quite a bit is
 already known, it can be very useful. When you are solving a complex
 puzzle, every little bit helps.</P>
<P><A href="#IPSEC">IPsec</A> itself does not defend against traffic
 analysis, but carefully thought out systems using IPsec can provide at
 least partial protection. In particular, one might want to encrypt more
 traffic than was strictly necessary, route things in odd ways, or even
 encrypt dummy packets, to confuse the analyst. We discuss this<A href="#traffic.resist">
 here</A>.</P>
</DD>
<DT><A name="transport">Transport mode</A></DT>
<DD>An IPsec application in which the IPsec gateway is the destination
 of the protected packets, a machine acts as its own gateway. Contrast
 with<A href="#tunnel"> tunnel mode</A>.</DD>
<DT>Triple DES</DT>
<DD>see<A href="#3DES"> 3DES</A></DD>
<DT><A name="TTL">TTL</A></DT>
<DD><STRONG>T</STRONG>ime<STRONG> T</STRONG>o<STRONG> L</STRONG>ive,
 used to control<A href="#DNS"> DNS</A> caching. Servers discard cached
 records whose TTL expires</DD>
<DT><A name="tunnel">Tunnel mode</A></DT>
<DD>An IPsec application in which an IPsec gateway provides protection
 for packets to and from other systems. Contrast with<A href="#transport">
 transport mode</A>.</DD>
<DT><A name="2key">Two-key Triple DES</A></DT>
<DD>A variant of<A href="#3DES"> triple DES or 3DES</A> in which only
 two keys are used. As in the three-key version, the order of operations
 is<A href="#EDE"> EDE</A> or encrypt-decrypt-encrypt, but in the
 two-key variant the first and third keys are the same.
<P>3DES with three keys has 3*56 = 168 bits of key but has only 112-bit
 strength against a<A href="#meet"> meet-in-the-middle</A> attack, so it
 is possible that the two key version is just as strong. Last I looked,
 this was an open question in the research literature.</P>
<P>RFC 2451 defines triple DES for<A href="#IPSEC"> IPsec</A> as the
 three-key variant. The two-key variant should not be used and is not
 implemented directly in<A href="#FreeSWAN"> Linux FreeS/WAN</A>. It
 cannot be used in automatically keyed mode without major fiddles in the
 source code. For manually keyed connections, you could make Linux
 FreeS/WAN talk to a two-key implementation by setting two keys the same
 in /etc/ipsec.conf.</P>
</DD>
<DT><A name="U">U</A></DT>
<DT><A name="V">V</A></DT>
<DT><A name="virtual">Virtual Interface</A></DT>
<DD>A<A href="#Linux"> Linux</A> feature which allows one physical
 network interface to have two or more IP addresses. See the<CITE> Linux
 Network Administrator's Guide</CITE> in<A href="#kirch"> book form</A>
 or<A href="http://metalab.unc.edu/LDP/LDP/nag/node1.html"> on the web</A>
 for details.</DD>
<DT>Virtual Private Network</DT>
<DD>see<A href="#VPN"> VPN</A></DD>
<DT><A name="VPN">VPN</A></DT>
<DD><B>V</B>irtual<B> P</B>rivate<B> N</B>etwork, a network which can
 safely be used as if it were private, even though some of its
 communication uses insecure connections. All traffic on those
 connections is encrypted.
<P><A href="#IPSEC">IPsec</A> is not the only technique available for
 building VPNs, but it is the only method defined by<A href="#RFC"> RFCs</A>
 and supported by many vendors. VPNs are by no means the only thing you
 can do with IPsec, but they may be the most important application for
 many users.</P>
</DD>
<DT><A name="VPNC">VPNC</A></DT>
<DD><A href="http://www.vpnc.org">Virtual Private Network Consortium</A>
, an association of vendors of VPN products.</DD>
<DT><A name="W">W</A></DT>
<DT><A name="Wassenaar.gloss">Wassenaar Arrangement</A></DT>
<DD>An international agreement restricting export of munitions and other
 tools of war. Unfortunately, cryptographic software is also restricted
 under the current version of the agreement.<A href="#Wassenaar">
 Discussion</A>.</DD>
<DT><A name="web">Web of Trust</A></DT>
<DD><A href="#PGP">PGP</A>'s method of certifying keys. Any user can
 sign a key; you decide which signatures or combinations of signatures
 to accept as certification. This contrasts with the hierarchy of<A href="#CA">
 CAs (Certification Authorities)</A> used in many<A href="#PKI"> PKIs
 (Public Key Infrastructures)</A>.
<P>See<A href="#GTR"> Global Trust Register</A> for an interesting
 addition to the web of trust.</P>
</DD>
<DT><A name="WEP">WEP (Wired Equivalent Privacy)</A></DT>
<DD>The cryptographic part of the<A href="#IEEE"> IEEE</A> standard for
 wireless LANs. As the name suggests, this is designed to be only as
 secure as a normal wired ethernet. Anyone with a network conection can
 tap it. Its advocates would claim this is good design, refusing to
 build in complex features beyond the actual requirements.
<P>Critics refer to WEP as &quot;Wire<EM>tap</EM> Equivalent Privacy&quot;, and
 consider it a horribly flawed design based on bogus &quot;requirements&quot;. You
 do not control radio waves as you might control your wires, so the
 metaphor in the rationale is utterly inapplicable. A security policy
 that chooses not to invest resources in protecting against certain
 attacks which can only be conducted by people physically plugged into
 your LAN may or may not be reasonable. The same policy is completely
 unreasonable when someone can &quot;plug in&quot; from a laptop half a block
 away..</P>
<P>There has been considerable analysis indicating that WEP is seriously
 flawed. A FAQ on attacks against WEP is available. Part of it reads:</P>
<BLOCKQUOTE> ... attacks are practical to mount using only inexpensive
 off-the-shelf equipment. We recommend that anyone using an 802.11
 wireless network not rely on WEP for security, and employ other
 security measures to protect their wireless network. Note that our
 attacks apply to both 40-bit and the so-called 128-bit versions of WEP
 equally well.</BLOCKQUOTE>
<P>WEP appears to be yet another instance of governments, and
 unfortunately some vendors and standards bodies, deliberately promoting
 hopelessly flawed &quot;security&quot; products, apparently mainly for the
 benefit of eavesdropping agencies. See this<A href="#weak"> discussion</A>
.</P>
</DD>
<DT><A name="X">X</A></DT>
<DT><A name="X509">X.509</A></DT>
<DD>A standard from the<A href="http://www.itu.int"> ITU (International
 Telecommunication Union)</A>, for hierarchical directories with
 authentication services, used in many<A href="#PKI"> PKI</A>
 implementations.
<P>Use of X.509 services, via the<A href="#LDAP"> LDAP protocol</A>, for
 certification of keys is allowed but not required by the<A href="#IPSEC">
 IPsec</A> RFCs. It is not yet implemented in<A href="#FreeSWAN"> Linux
 FreeS/WAN</A>.</P>
</DD>
<DT>Xedia</DT>
<DD>A vendor of router and Internet access products, now part of Lucent.
 Their QVPN products interoperate with Linux FreeS/WAN; see our<A href="#xedia">
 interop document</A>.</DD>
<DT><A name="Y">Y</A></DT>
<DT><A name="Z">Z</A></DT>
</DL>
<HR>
<H1><A name="biblio">Bibliography for the Linux FreeS/WAN project</A></H1>
<P>For extensive bibliographic links, see the<A href="http://liinwww.ira.uka.de/bibliography/index.html">
 Collection of Computer Science Bibliographies</A></P>
<P>See our<A href="web.html"> web links</A> for material available
 online.</P>
<HR><A name="adams"> Carlisle Adams and Steve Lloyd<CITE> Understanding
 Public Key Infrastructure</CITE>
<BR></A> Macmillan 1999 ISBN 1-57870-166-x
<P>An overview, mainly concentrating on policy and strategic issues
 rather than the technical details. Both authors work for<A href="#PKI">
 PKI</A> vendor<A href="http://www.entrust.com/"> Entrust</A>.</P>
<HR><A name="DNS.book"> Albitz, Liu &amp; Loukides<CITE> DNS &amp; BIND</CITE>
 3rd edition
<BR></A> O'Reilly 1998 ISBN 1-56592-512-2
<P>The standard reference on the<A href="#DNS"> Domain Name Service</A>
 and<A href="#BIND"> Berkeley Internet Name Daemon</A>.</P>
<HR><A name="anderson"> Ross Anderson</A>,<CITE> Security Engineering -
 a Guide to Building Dependable Distributed Systems</CITE>
<BR> Wiley, 2001, ISBN 0471389226
<P>Easily the best book for the security professional I have seen.<STRONG>
 Highly recommended</STRONG>. See the<A href="http://www.cl.cam.ac.uk/~rja14/book.html">
 book web page</A>.</P>
<P>This is quite readable, but Schneier's<A href="#secrets"> Secrets and
 Lies</A> might be an easier introduction.</P>
<HR><A name="puzzle"> Bamford<CITE> The Puzzle Palace, A report on NSA,
 Americas's most Secret Agency</CITE>
<BR> Houghton Mifflin 1982 ISBN 0-395-31286-8</A>
<HR> Bamford<CITE> Body of Secrets</CITE>
<P>The sequel.</P>
<HR><A name="bander"> David Bander</A>,<CITE> Linux Security Toolkit</CITE>
<BR> IDG Books, 2000, ISBN: 0764546902
<P>This book has a short section on FreeS/WAN and includes Caldera Linux
 on CD.</P>
<HR><A name="CZR"> Chapman, Zwicky &amp; Russell</A>,<CITE> Building
 Internet Firewalls</CITE>
<BR> O'Reilly 1995 ISBN 1-56592-124-0
<HR><A name="firewall.book"> Cheswick and Bellovin</A><CITE> Firewalls
 and Internet Security: Repelling the Wily Hacker</CITE>
<BR> Addison-Wesley 1994 ISBN 0201633574
<P>A fine book on firewalls in particular and security in general from
 two of AT&amp;T's system adminstrators.</P>
<P>Bellovin has also done a number of<A href="#papers"> papers</A> on
 IPsec and co-authored a<A href="#applied"> paper</A> on a large
 FreeS/WAN application.</P>
<HR><A name="comer"> Comer<CITE> Internetworking with TCP/IP</CITE>
<BR> Prentice Hall</A>
<UL>
<LI>Vol. I: Principles, Protocols, &amp; Architecture, 3rd Ed. 1995
 ISBN:0-13-216987-8</LI>
<LI>Vol. II: Design, Implementation, &amp; Internals, 2nd Ed. 1994
 ISBN:0-13-125527-4</LI>
<LI>Vol. III: Client/Server Programming &amp; Applications
<UL>
<LI>AT&amp;T TLI Version 1994 ISBN:0-13-474230-3</LI>
<LI>BSD Socket Version 1996 ISBN:0-13-260969-X</LI>
<LI>Windows Sockets Version 1997 ISBN:0-13-848714-6</LI>
</UL>
</LI>
</UL>
<P>If you need to deal with the details of the network protocols, read
 either this series or the<A href="#stevens"> Stevens and Wright</A>
 series before you start reading the RFCs.</P>
<HR><A name="diffie"> Diffie and Landau</A><CITE> Privacy on the Line:
 The Politics of Wiretapping and Encryption</CITE>
<BR> MIT press 1998 ISBN 0-262-04167-7 (hardcover) or 0-262-54100-9
<BR>
<HR><A name="d_and_hark"> Doraswamy and Harkins<CITE> IP Sec: The New
 Security Standard for the Internet, Intranets and Virtual Private
 Networks</CITE>
<BR> Prentice Hall 1999 ISBN: 0130118982</A>
<HR><A name="EFF"> Electronic Frontier Foundation<CITE> Cracking DES:
 Secrets of Encryption Research, Wiretap Politics and Chip Design</CITE>
<BR></A> O'Reilly 1998 ISBN 1-56592-520-3
<P>To conclusively demonstrate that DES is inadequate for continued use,
 the<A href="#EFF"> EFF</A> built a machine for just over $200,000 that
 breaks DES encryption in under five days on average, under nine in the
 worst case.</P>
<P>The book provides details of their design and, perhaps even more
 important, discusses why they felt the project was necessary.
 Recommended for anyone interested in any of the three topics mentioned
 in the subtitle.</P>
<P>See also the<A href="http://www.eff.org/descracker.html"> EFF page on
 this project</A> and our discussion of<A href="#desnotsecure"> DES
 insecurity</A>.</P>
<HR> Martin Freiss<CITE> Protecting Networks with SATAN</CITE>
<BR> O'Reilly 1998 ISBN 1-56592-425-8
<BR> translated from a 1996 work in German
<P>SATAN is a Security Administrator's Tool for Analysing Networks. This
 book is a tutorial in its use.</P>
<HR> Gaidosch and Kunzinger<CITE> A Guide to Virtual Private Networks</CITE>
<BR> Prentice Hall 1999 ISBN: 0130839647
<HR><A name="Garfinkel"> Simson Garfinkel</A><CITE> Database Nation: the
 death of privacy in the 21st century</CITE>
<BR> O'Reilly 2000 ISBN 1-56592-653-6
<P>A thoughtful and rather scary book.</P>
<HR><A name="PGP"> Simson Garfinkel</A><CITE> PGP: Pretty Good Privacy</CITE>
<BR> O'Reilly 1995 ISBN 1-56592-098-8
<P>An excellent introduction and user manual for the<A href="#PGP"> PGP</A>
 email-encryption package. PGP is a good package with a complex and
 poorly-designed user interface. This book or one like it is a must for
 anyone who has to use it at length.</P>
<P>The book covers using PGP in Unix, PC and Macintosh environments,
 plus considerable background material on both the technical and
 political issues around cryptography.</P>
<P>The book is now seriously out of date. It does not cover recent
 developments such as commercial versions since PGP 5, the Open PGP
 standard or GNU PG..</P>
<HR><A name="practical"> Garfinkel and Spafford</A><CITE> Practical Unix
 Security</CITE>
<BR> O'Reilly 1996 ISBN 1-56592-148-8
<P>A standard reference.</P>
<P>Spafford's web page has an excellent collection of<A href="http://www.cs.purdue.edu/coast/hotlist">
 crypto and security links</A>.</P>
<HR><A name="Kahn"> David Kahn</A><CITE> The Codebreakers: the
 Comprehensive History of Secret Communications from Ancient Times to
 the Internet</CITE>
<BR> second edition Scribner 1996 ISBN 0684831309
<P>A history of codes and code-breaking from ancient Egypt to the 20th
 century. Well-written and exhaustively researched.<STRONG> Highly
 recommended</STRONG>, even though it does not have much on computer
 cryptography.</P>
<HR> David Kahn<CITE> Seizing the Enigma, The Race to Break the German
 U-Boat codes, 1939-1943</CITE>
<BR> Houghton Mifflin 1991 ISBN 0-395-42739-8
<HR><A name="kirch"> Olaf Kirch</A><CITE> Linux Network Administrator's
 Guide</CITE>
<BR> O'Reilly 1995 ISBN 1-56592-087-2
<P>Now becoming somewhat dated in places, but still a good introductory
 book and general reference.</P>
<HR><A name="LinVPN"> Kolesnikov and Hatch</A>,<CITE> Building Linux
 Virtual Private Networks (VPNs)</CITE>
<BR> New Riders 2002
<P>This has had a number of favorable reviews, including<A href="http://www.slashdot.org/article.pl?sid=02/02/27/0115214&amp;mode=thread&amp;tid=172">
 this one</A> on Slashdot. The book has a<A href="http://www.buildinglinuxvpns.net/">
 web site</A>.</P>
<HR><A name="RFCs"> Pete Loshin<CITE> Big Book of IPsec RFCs</CITE>
<BR> Morgan Kaufmann 2000 ISBN: 0-12-455839-9</A>
<HR><A name="crypto"> Steven Levy<CITE> Crypto: How the Code Rebels Beat
 the Government -- Saving Privacy in the Digital Age</CITE></A>
<BR> Penguin 2001, ISBN 0-670--85950-8
<P><STRONG>Highly recommended</STRONG>. A fine history of recent (about
 1970-2000) developments in the field, and the related political
 controversies. FreeS/WAN project founder and leader John Gilmore
 appears several times.</P>
<P>The book does not cover IPsec or FreeS/WAN, but this project is very
 much another battle in the same war. See our discussion of the<A href="politics.html">
 politics</A>.</P>
<HR><A name="GTR"> Matyas, Anderson et al.</A><CITE> The Global Trust
 Register</CITE>
<BR> Northgate Consultants Ltd 1998 ISBN: 0953239705
<BR> hard cover edition MIT Press 1999 ISBN 0262511053
<P>From<A href="http://www.cl.cam.ac.uk/Research/Security/Trust-Register">
 their web page:</A></P>
<BLOCKQUOTE> This book is a register of the fingerprints of the world's
 most important public keys; it implements a top-level certification
 authority (CA) using paper and ink rather than in an electronic system.</BLOCKQUOTE>
<HR><A name="handbook"> Menezies, van Oorschot and Vanstone<CITE>
 Handbook of Applied Cryptography</CITE></A>
<BR> CRC Press 1997
<BR> ISBN 0-8493-8523-7
<P>An excellent reference. Read<A href="#schneier"> Schneier</A> before
 tackling this.</P>
<HR> Michael Padlipsky<CITE> Elements of Networking Style</CITE>
<BR> Prentice-Hall 1985 ISBN 0-13-268111-0 or 0-13-268129-3
<P>Probably<STRONG> the funniest technical book ever written</STRONG>,
 this is a vicious but well-reasoned attack on the OSI &quot;seven layer
 model&quot; and all that went with it. Several chapters of it are also
 available as RFCs 871 to 875.</P>
<HR><A name="matrix"> John S. Quarterman</A><CITE> The Matrix: Computer
 Networks and Conferencing Systems Worldwide</CITE>
<BR> Digital Press 1990 ISBN 155558-033-5
<BR> Prentice-Hall ISBN 0-13-565607-9
<P>The best general treatment of computer-mediated communication we have
 seen. It naturally has much to say about the Internet, but also covers
 UUCP, Fidonet and so on.</P>
<HR><A name="ranch"> David Ranch</A><CITE> Securing Linux Step by Step</CITE>
<BR> SANS Institute, 1999
<P><A href="http://www.sans.org/">SANS</A> is a respected organisation,
 this guide is part of a well-known series, and Ranch has previously
 written the useful<A href=" http://www.ecst.csuchico.edu/~dranch/LINUX/index-linux.html#trinityos">
 Trinity OS</A> guide to securing Linux, so my guess would be this is a
 pretty good book. I haven't read it yet, so I'm not certain. It can be
 ordered online from<A href="http://www.sans.org/"> SANS</A>.</P>
<P>Note (Mar 1, 2002): a new edition with different editors in the
 works. Expect it this year.</P>
<HR><A name="schneier"> Bruce Schneier</A><CITE> Applied Cryptography,
 Second Edition</CITE>
<BR> John Wiley &amp; Sons, 1996
<BR> ISBN 0-471-12845-7 hardcover
<BR> ISBN 0-471-11709-9 paperback
<P>A standard reference on computer cryptography. For more recent
 essays, see the<A href="http://www.counterpane.com/"> author's
 company's web site</A>.</P>
<HR><A name="secrets"> Bruce Schneier</A><CITE> Secrets and Lies</CITE>
<BR> Wiley 2000, ISBN 0-471-25311-1
<P>An interesting discussion of security and privacy issues, written
 with more of an &quot;executive overview&quot; approach rather than a narrow
 focus on the technical issues.<STRONG> Highly recommended</STRONG>.</P>
<P>This is worth reading even if you already understand security issues,
 or think you do. To go deeper, follow it with Anderson's<A href="#anderson">
 Security Engineering</A>.</P>
<HR><A name="VPNbook"> Scott, Wolfe and Irwin<CITE> Virtual Private
 Networks</CITE></A>
<BR> 2nd edition, O'Reilly 1999 ISBN: 1-56592-529-7
<P>This is the only O'Reilly book, out of a dozen I own, that I'm
 disappointed with. It deals mainly with building VPNs with various
 proprietary tools --<A href="#PPTP"> PPTP</A>,<A href="#ssh"> SSH</A>,
 Cisco PIX, ... -- and touches only lightly on IPsec-based approaches.</P>
<P>That said, it appears to deal competently with what it does cover and
 it has readable explanations of many basic VPN and security concepts.
 It may be exactly what some readers require, even if I find the
 emphasis unfortunate.</P>
<HR><A name="LASG"> Kurt Seifried<CITE> Linux Administrator's Security
 Guide</CITE></A>
<P>Available online from<A href="http://www.securityportal.com/lasg/">
 Security Portal</A>. It has fairly extensive coverage of IPsec.</P>
<HR><A name="Smith"> Richard E Smith<CITE> Internet Cryptography</CITE>
<BR></A> ISBN 0-201-92480-3, Addison Wesley, 1997
<P>See the book's<A href="http://www.visi.com/crypto/inet-crypto/index.html">
 home page</A></P>
<HR><A name="neal"> Neal Stephenson<CITE> Cryptonomicon</CITE></A>
<BR> Hardcover ISBN -380-97346-4, Avon, 1999.
<P>A novel in which cryptography and the net figure prominently.<STRONG>
 Highly recommended</STRONG>: I liked it enough I immediately went out
 and bought all the author's other books.</P>
<P>There is also a paperback edition. Sequels are expected.</P>
<HR><A name="stevens"> Stevens and Wright</A><CITE> TCP/IP Illustrated</CITE>
<BR> Addison-Wesley
<UL>
<LI>Vol. I: The Protocols 1994 ISBN:0-201-63346-9</LI>
<LI>Vol. II: The Implementation 1995 ISBN:0-201-63354-X</LI>
<LI>Vol. III: TCP for Transactions, HTTP, NNTP, and the UNIX Domain
 Protocols 1996 ISBN: 0-201-63495-3</LI>
</UL>
<P>If you need to deal with the details of the network protocols, read
 either this series or the<A href="#comer"> Comer</A> series before you
 start reading the RFCs.</P>
<HR><A name="Rubini"> Rubini</A><CITE> Linux Device Drivers</CITE>
<BR> O'Reilly &amp; Associates, Inc. 1998 ISBN 1-56592-292-1
<HR><A name="Zeigler"> Robert Zeigler</A><CITE> Linux Firewalls</CITE>
<BR> Newriders Publishing, 2000 ISBN 0-7537-0900-9
<P>A good book, with detailed coverage of ipchains(8) firewalls and of
 many related issues.</P>
<HR>
<H1><A name="RFC">IPsec RFCs and related documents</A></H1>
<H2><A name="RFCfile">The RFCs.tar.gz Distribution File</A></H2>
<P>The Linux FreeS/WAN distribution is available from<A href="http://www.xs4all.nl/~freeswan">
 our primary distribution site</A> and various mirror sites. To give
 people more control over their downloads, the RFCs that define IP
 security are bundled separately in the file RFCs.tar.gz.</P>
<P>The file you are reading is included in the main distribution and is
 available on the web site. It describes the RFCs included in the<A href="#RFCs.tar.gz">
 RFCs.tar.gz</A> bundle and gives some pointers to<A href="#sources">
 other ways to get them</A>.</P>
<H2><A name="sources">Other sources for RFCs &amp; Internet drafts</A></H2>
<H3><A name="RFCdown">RFCs</A></H3>
<P>RFCs are downloadble at many places around the net such as:</P>
<UL>
<LI><A href="http://www.rfc-editor.org">http://www.rfc-editor.org</A></LI>
<LI><A href="http://nis.nsf.net/internet/documents/rfc">NSF.net</A></LI>
<LI><A href="http://sunsite.doc.ic.ac.uk/computing/internet/rfc">Sunsite
 in the UK</A></LI>
</UL>
<P>browsable in HTML form at others such as:</P>
<UL>
<LI><A href="http://www.landfield.com/rfcs/index.html">landfield.com</A></LI>
<LI><A href="http://www.library.ucg.ie/Connected/RFC">Connected Internet
 Encyclopedia</A></LI>
</UL>
<P>and some of them are available in translation:</P>
<UL>
<LI><A href="http://www.eisti.fr/eistiweb/docs/normes/">French</A></LI>
</UL>
<P>There is also a published<A href="#RFCs"> Big Book of IPSEC RFCs</A>.</P>
<H3><A name="drafts">Internet Drafts</A></H3>
<P>Internet Drafts, working documents which sometimes evolve into RFCs,
 are also available.</P>
<UL>
<LI><A href="http://www.ietf.org/ID.html">Overall reference page</A></LI>
<LI><A href="http://www.ietf.org/ids.by.wg/ipsec.html">IPsec</A> working
 group</LI>
<LI><A href="http://www.ietf.org/ids.by.wg/ipsra.html">IPSRA (IPsec
 Remote Access)</A> working group</LI>
<LI><A href="http://www.ietf.org/ids.by.wg/ipsp.html">IPsec Policy</A>
 working group</LI>
<LI><A href="http://www.ietf.org/ids.by.wg/kink.html">KINK (Kerberized
 Internet Negotiation of Keys)</A> working group</LI>
</UL>
<P>Note: some of these may be obsolete, replaced by later drafts or by
 RFCs.</P>
<H3><A name="FIPS1">FIPS standards</A></H3>
<P>Some things used by<A href="#IPSEC"> IPsec</A>, such as<A href="#DES">
 DES</A> and<A href="#SHA"> SHA</A>, are defined by US government
 standards called<A href="#FIPS"> FIPS</A>. The issuing organisation,<A href="#NIST">
 NIST</A>, have a<A href="http://www.itl.nist.gov/div897/pubs"> FIPS
 home page</A>.</P>
<H2><A name="RFCs.tar.gz">What's in the RFCs.tar.gz bundle?</A></H2>
<P>All filenames are of the form rfc*.txt, with the * replaced with the
 RFC number.</P>
<PRE>RFC#        Title</PRE>
<H3><A name="rfc.ov">Overview RFCs</A></H3>
<PRE>2401        Security Architecture for the Internet Protocol
2411        IP Security Document Roadmap</PRE>
<H3><A name="basic.prot">Basic protocols</A></H3>
<PRE>2402        IP Authentication Header
2406        IP Encapsulating Security Payload (ESP)</PRE>
<H3><A name="key.ike">Key management</A></H3>
<PRE>2367        PF_KEY Key Management API, Version 2
2407        The Internet IP Security Domain of Interpretation for ISAKMP
2408        Internet Security Association and Key Management Protocol (ISAKMP)
2409        The Internet Key Exchange (IKE)
2412        The OAKLEY Key Determination Protocol
2528        Internet X.509 Public Key Infrastructure</PRE>
<H3><A name="rfc.detail">Details of various things used</A></H3>
<PRE>2085        HMAC-MD5 IP Authentication with Replay Prevention
2104        HMAC: Keyed-Hashing for Message Authentication
2202        Test Cases for HMAC-MD5 and HMAC-SHA-1
2207        RSVP Extensions for IPSEC Data Flows
2403        The Use of HMAC-MD5-96 within ESP and AH
2404        The Use of HMAC-SHA-1-96 within ESP and AH
2405        The ESP DES-CBC Cipher Algorithm With Explicit IV
2410        The NULL Encryption Algorithm and Its Use With IPsec
2451        The ESP CBC-Mode Cipher Algorithms
2521        ICMP Security Failures Messages</PRE>
<H3><A name="rfc.ref">Older RFCs which may be referenced</A></H3>
<PRE>1321        The MD5 Message-Digest Algorithm
1828        IP Authentication using Keyed MD5
1829        The ESP DES-CBC Transform
1851        The ESP Triple DES Transform
1852        IP Authentication using Keyed SHA</PRE>
<H3><A name="rfc.dns">RFCs for secure DNS service, which IPsec may use</A>
</H3>
<PRE>2137        Secure Domain Name System Dynamic Update
2230        Key Exchange Delegation Record for the DNS
2535        Domain Name System Security Extensions
2536        DSA KEYs and SIGs in the Domain Name System (DNS)
2537        RSA/MD5 KEYs and SIGs in the Domain Name System (DNS)
2538        Storing Certificates in the Domain Name System (DNS)
2539        Storage of Diffie-Hellman Keys in the Domain Name System (DNS)</PRE>
<H3><A name="rfc.exp">RFCs labelled &quot;experimental&quot;</A></H3>
<PRE>2521        ICMP Security Failures Messages
2522        Photuris: Session-Key Management Protocol
2523        Photuris: Extended Schemes and Attributes</PRE>
<H3><A name="rfc.rel">Related RFCs</A></H3>
<PRE>1750        Randomness Recommendations for Security
1918        Address Allocation for Private Internets
1984        IAB and IESG Statement on Cryptographic Technology and the Internet
2144        The CAST-128 Encryption Algorithm</PRE>
<HR>
<H1><A name="roadmap">Distribution Roadmap: What's Where in Linux
 FreeS/WAN</A></H1>
<P> This file is a guide to the locations of files within the FreeS/WAN
 distribution. Everything described here should be on your system once
 you download, gunzip, and untar the distribution.</P>
<P>This distribution contains two major subsystems</P>
<DL>
<DT><A href="#klips.roadmap">KLIPS</A></DT>
<DD>the kernel code</DD>
<DT><A href="#pluto.roadmap">Pluto</A></DT>
<DD>the user-level key-management daemon</DD>
</DL>
<P>plus assorted odds and ends.</P>
<H2><A name="top">Top directory</A></H2>
<P>The top directory has essential information in text files:</P>
<DL>
<DT>README</DT>
<DD>introduction to the software</DD>
<DT>INSTALL</DT>
<DD>short experts-only installation procedures. More detalied procedures
 are in<A href="install.html"> installation</A> and<A href="config.html">
 configuration</A> HTML documents.</DD>
<DT>BUGS</DT>
<DD>major known bugs in the current release.</DD>
<DT>CHANGES</DT>
<DD>changes from previous releases</DD>
<DT>CREDITS</DT>
<DD>acknowledgement of contributors</DD>
<DT>COPYING</DT>
<DD>licensing and distribution information</DD>
</DL>
<H2><A name="doc">Documentation</A></H2>
<P> The doc directory contains the bulk of the documentation, most of it
 in HTML format. See the<A href="index.html"> index file</A> for
 details.</P>
<H2><A name="klips.roadmap">KLIPS: kernel IP security</A></H2>
<P><A href="#KLIPS"> KLIPS</A> is<STRONG> K</STRONG>erne<STRONG>L</STRONG><STRONG>
 IP</STRONG><STRONG> S</STRONG>ecurity. It lives in the klips directory,
 of course.</P>
<DL>
<DT>klips/doc</DT>
<DD>documentation</DD>
<DT>klips/patches</DT>
<DD>patches for existing kernel files</DD>
<DT>klips/test</DT>
<DD>test stuff</DD>
<DT>klips/utils</DT>
<DD>low-level user utilities</DD>
<DT>klips/net/ipsec</DT>
<DD>actual klips kernel files</DD>
<DT>klips/src</DT>
<DD>symbolic link to klips/net/ipsec
<P>The &quot;make insert&quot; step of installation installs the patches and makes
 a symbolic link from the kernel tree to klips/net/ipsec. The odd name
 of klips/net/ipsec is dictated by some annoying limitations of the
 scripts which build the Linux kernel. The symbolic-link business is a
 bit messy, but all the alternatives are worse.</P>
<P></P>
</DD>
<DT>klips/utils</DT>
<DD>Utility programs:
<P></P>
<DL>
<DT>eroute</DT>
<DD>manipulate IPsec extended routing tables</DD>
<DT>klipsdebug</DT>
<DD>set Klips (kernel IPsec support) debug features and level</DD>
<DT>spi</DT>
<DD>manage IPsec Security Associations</DD>
<DT>spigrp</DT>
<DD>group/ungroup IPsec Security Associations</DD>
<DT>tncfg</DT>
<DD>associate IPsec virtual interface with real interface</DD>
</DL>
<P>These are all normally invoked by ipsec(8) with commands such as</P>
<PRE>        ipsec tncfg <VAR>arguments</VAR></PRE>
 There are section 8 man pages for all of these; the names have &quot;ipsec_&quot;
 as a prefix, so your man command should be something like:
<PRE>        man 8 ipsec_tncfg</PRE>
</DD>
</DL>
<H2><A name="pluto.roadmap">Pluto key and connection management daemon</A>
</H2>
<P><A href="#Pluto"> Pluto</A> is our key management and negotiation
 daemon. It lives in the pluto directory, along with its low-level user
 utility, whack.</P>
<P> There are no subdirectories. Documentation is a man page,<A href="manpage.d/ipsec_pluto.8.html">
 pluto.8</A>. This covers whack as well.</P>
<H2><A name="utils">Utils</A></H2>
<P> The utils directory contains a growing collection of higher-level
 user utilities, the commands that administer and control the software.
 Most of the things that you will actually have to run yourself are in
 there.</P>
<DL>
<DT>ipsec</DT>
<DD>invoke IPsec utilities
<P>ipsec(8) is normally the only program installed in a standard
 directory, /usr/local/sbin. It is used to invoke the others, both those
 listed below and the ones in klips/utils mentioned above.</P>
<P></P>
</DD>
<DT>auto</DT>
<DD>control automatically-keyed IPsec connections</DD>
<DT>manual</DT>
<DD>take manually-keyed IPsec connections up and down</DD>
<DT>barf</DT>
<DD>generate copious debugging output</DD>
<DT>look</DT>
<DD>generate moderate amounts of debugging output</DD>
</DL>
<P> There are .8 manual pages for these. look is covered in barf.8. The
 man pages have an &quot;ipsec_&quot; prefix so your man command should be
 something like:</P>
<PRE>
        man 8 ipsec_auto
</PRE>
<P> Examples are in various files with names utils/*.eg</P>
<H2><A name="lib">Libraries</A></H2>
<H3><A name="fswanlib">FreeS/WAN Library</A></H3>
<P> The lib directory is the FreeS/WAN library, also steadily growing,
 used by both user-level and kernel code.
<BR /> It includes section 3<A href="manpages.html"> man pages</A> for
 the library routines.</P>
<H3><A name="otherlib">Imported Libraries</A></H3>
<H4><A NAME="33_6_2_1">LibDES</A></H4>
 The libdes library, originally from SSLeay, is used by both Klips and
 Pluto for<A href="#3DES"> Triple DES</A> encryption. Single DES is not
 used because<A href="#desnotsecure"> it is insecure</A>.
<P> Note that this library has its own license, different from the<A href="#GPL">
 GPL</A> used for other code in FreeS/WAN.</P>
<P> The library includes its own documentation.</P>
<H4><A NAME="33_6_2_2">GMP</A></H4>
 The GMP (GNU multi-precision) library is used for multi-precision
 arithmetic in Pluto's key-exchange code and public key code.
<P> Older versions (up to 1.7) of FreeS/WAN included a copy of this
 library in the FreeS/WAN distribution.</P>
<P> Since 1.8, we have begun to rely on the system copy of GMP.</P>
<HR>
<H1><A name="umltesting">User-Mode-Linux Testing guide</A></H1>
<P> User mode linux is a way to compile a linux kernel such that it can
 run as a process in another linux system (potentially as a *BSD or
 Windows process later). See<A HREF="http://user-mode-linux.sourceforge.net/">
 http://user-mode-linux.sourceforge.net/</A></P>
<P> UML is a good platform for testing and experimenting with FreeS/WAN.
 It allows several network nodes to be simulated on a single machine.
 Creating, configuring, installing, monitoring, and controling these
 nodes is generally easier and easier to script with UML than real
 hardware.</P>
<P> You'll need about 500Mb of disk space for a full
 sunrise-east-west-sunset setup. You can possibly get this down by 130Mb
 if you remove the sunrise/sunset kernel build. If you just want to run,
 then you can even remove the east/west kernel build.</P>
<P> Nothing need be done as super user. In a couple of steps, we note
 where super user is required to install commands in system-wide
 directories, but ~/bin could be used instead. UML seems to use a
 system-wide /tmp/uml directory so different users may interfere with
 one another. Later UMLs use ~/.uml instead, so multiple users running
 UML tests should not be a problem, but note that a single user running
 the UML tests will only be able run one set. Further, UMLs sometimes
 get stuck and hang around. These &quot;zombies&quot; (most will actually be in
 the &quot;T&quot; state in the process table) will interfere with subsequent
 tests.</P>
<H2><A NAME="34_1">Preliminary Notes on BIND</A></H2>
<P> As of 2003/3/1, the Light-Weight Resolver is used by pluto. This
 requires that BIND9 be running. It also requires that BIND9 development
 libraries be present in the build environment. The DNSSEC code is only
 truly functional in BIND9 snapshots. The library code could be 9.2.2,
 we believe. We are using BIND9 20021115 snapshot code from<A HREF="ftp://ftp.isc.org/isc/bind9/snapshots">
 ftp://ftp.isc.org/isc/bind9/snapshots</A>.</P>
<P> FreeS/WAN may well require a newer BIND than is on your system. Many
 distributions have moved to BIND9.2.2 recently due to a security
 advisory. BIND is five components.</P>
<OL>
<LI> named</LI>
<LI> dnssec-*</LI>
<LI> client side resolver libraries</LI>
<LI> client side utility libraries I thought there were lib and named
 parts to dnsssec...</LI>
<LI> dynamic DNS update utilities</LI>
</OL>
<P> The only piece that we need for *building* is #4. That's the only
 part that has to be on the build host. What is the difference between
 resolver and util libs? If you want to edit
 testing/baseconfigs/all/etc/bind, you'll need a snapshot version. The
 resolver library contains the resolver. FreeS/WAN has its own copy of
 that in lib/liblwres.</P>
<H2><A NAME="34_2">Steps to Install UML for FreeS/WAN</A></H2>
<OL>
<LI> Get the following files:
<OL type="a">
<LI> from<A HREF="http://www.sandelman.ottawa.on.ca/freeswan/uml/">
 http://www.sandelman.ottawa.on.ca/freeswan/uml/</A>
 umlfreeroot-15.1.tar.gz (or highest numbered one). This is a debian
 potato root file system. You can use this even on a Redhat host, as it
 has the newer GLIBC2.2 libraries as well.
<!-- If you are using
  Redhat 7.2 or newer as your development machine, you can create the
  image from your installation media. See <A HREF="uml-rhroot.html">Building a RedHat root"></A>.
  A future document will explain how to build this from .DEB files as well.
-->

<!--
<LI> umlfreesharemini.tar.gz    (or umlfreeshareall.tar.gz). 
  If you are a Debian potato user, you don't need it you can use your
  native /usr/share.
</UL>
-->
</LI>
<LI> From<A HREF="ftp://ftp.xs4all.nl/pub/crypto/freeswan/">
 ftp://ftp.xs4all.nl/pub/crypto/freeswan/</A> a snapshot or release
 (1.92 or better)</LI>
<LI> From a<A HREF="http://www.kernel.org/mirrors/">
 http://www.kernel.org mirror</A>, the virgin 2.4.19 kernel. Please
 realize that we have defaults in our tree for kernel configuration. We
 try to track the latest UML kernels. If you use a newer kernel, you may
 have faults in the kernel build process. You can see what the latest
 that is being regularly tested by visiting<A HREF="http://bugs.freeswan.org:81/regress/HEAD/lastgood/freeswan-regress-env.sh">
 freeswan-regress-env.sh</A>.</LI>
<LI>
<!-- Note: this step is refered to as "step 1d" below. -->
 Get<A HREF="http://ftp.nl.linux.org/uml/">
 http://ftp.nl.linux.org/uml/</A> uml-patch-2.4.19-47.bz2 or the one
 associated with your kernel. As of 2003/03/05, uml-patch-2.4.19-47.bz2
 works for us.<STRONG> More recent versions of the patch have not been
 tested by us.</STRONG></LI>
<LI> You'll probably want to visit<A HREF="http://user-mode-linux.sourceforge.net">
 http://user-mode-linux.sourceforge.net</A> and get the UML utilities.
 These are not needed for the build or interactive use (but
 recommended). They are necessary for the regression testing procedures
 used by &quot;make check&quot;. We currently use uml_utilities_20020212.tar.bz2.</LI>
<LI> You need tcpdump version 3.7.1 or better. This is newer than the
 version included in most LINUX distributions. You can check the version
 of an installed tcpdump with the --version flag. If you need a newer
 tcpdump fetch both tcpdump and libpcap source tar files from<A HREF="http://www.tcpdump.org/">
 http://www.tcpdump.org/</A> or a mirror.</LI>
</OL>
</LI>
<LI> Pick a suitable place, and extract the following files:
<OL type="a">
<LI>
<!-- Note: this step is refered to as "step 2a" later. -->
 2.4.19 kernel. For instance:
<PRE>
 <CODE>           cd /c2/kernel
           tar xzvf ../download/pub/linux/kernel/v2.4/linux-2.4.19.tar.gz
</CODE>
</PRE>
</LI>
<LI> extract the umlfreeroot file
<!-- (unless you <A HREF="uml-rhroot.html">built your own from RPMs</A>) -->

<PRE>
 <CODE>           mkdir -p /c2/user-mode-linux/basic-root
           cd /c2/user-mode-linux/basic-root
           tar xzvf ../download/umlfreeroot-15.1.tar.gz
</CODE>
</PRE>
</LI>
<LI> FreeSWAN itself (or checkout &quot;all&quot; from CVS)
<PRE>
 <CODE>           mkdir -p /c2/freeswan/sandbox
           cd /c2/freeswan/sandbox
           tar xzvf ../download/snapshot.tar.gz
</CODE>
</PRE>
</LI>
</OL>
</LI>
<LI> If you need to build a newer tcpdump:
<UL>
<LI> Make sure you have OpenSSL installed -- it is needed for
 cryptographic routines.</LI>
<LI> Unpack libpcap and tcpdump source in parallel directories (the
 tcpdump build procedures look for libpcap next door).</LI>
<LI> Change directory into the libpcap source directory and then build
 the library:
<PRE>
 <CODE>	./configure
	make
</CODE>
</PRE>
</LI>
<LI> Change into the tcpdump source directory, build tcpdump, and
 install it.
<PRE>
 <CODE>	./configure
	make
	# Need to be superuser to install in system directories.
	# Installing in ~/bin would be an alternative.
	su -c &quot;make install&quot;
</CODE>
</PRE>
</LI>
</UL>
</LI>
<LI> If you need the uml utilities, unpack them somewhere then build and
 install them:
<PRE>
 <CODE>	cd tools
	make all
	# Need to be superuser to install in system directories.
	# Installing in ~/bin would be an alternative.
	su -c &quot;make install BIN_DIR=/usr/local/bin&quot;
</CODE>
</PRE>
</LI>
<LI> set up the configuration file
<UL>
<LI> <CODE>cd /c2/freeswan/sandbox/freeswan-1.97/testing/utils</CODE></LI>
<LI> copy umlsetup-sample.sh to ../../umlsetup.sh: <CODE> cp
 umlsetup-sample.sh ../../umlsetup.sh</CODE></LI>
<LI> open up ../../umlsetup.sh in your favorite editor.</LI>
<LI> change POOLSPACE= to point to the place with at least 500Mb of
 disk. Best if it is on the same partition as the &quot;umlfreeroot&quot;
 extraction, as it will attempt to use hard links if possible to save
 disk space.</LI>
<LI> Set TESTINGROOT if you intend to run the script outside of the
 sandbox/snapshot/release directory. Otherwise, it will configure
 itself.</LI>
<LI> KERNPOOL should point to the directory with your 2.4.19 kernel
 tree. This tree should be unconfigured! This is the directory you used
 in step 2a.</LI>
<LI> UMLPATCH should point at the bz2 file you downloaded at 1d. If
 using a kernel that already includes the patch, set this to /dev/null.</LI>
<LI> FREESWANDIR should point at the directory where you unpacked the
 snapshot/release. Include the &quot;freeswan-snap2001sep16b&quot; or whatever in
 it. If you are running from CVS, then you point at the directory where
 top, klips, etc. are. The script will fix up the directory so that it
 can be used.</LI>
<LI> BASICROOT should be set to the directory used in 2b, or to the
 directory that you created with RPMs.</LI>
<LI> SHAREDIR should be set to the directory used in 2c, to /usr/share
 for Debian potato users, or to $BASICROOT/usr/share.</LI>
</UL>
</LI>
<LI>
<PRE> <CODE>cd $TESTINGROOT/utils
sh make-uml.sh
</CODE></PRE>
 It will grind for awhile. If there are errors it will bail. If so, run
 it under &quot;script&quot; and send the output to bugs@lists.freeswan.org.</LI>
<LI> You will have a bunch of stuff under $POOLSPACE. Open four xterms:
<PRE> <CODE>    for i in sunrise sunset east west
    do
        xterm -name $i -title $i -e $POOLSPACE/$i/start.sh     done
</CODE></PRE>
</LI>
<LI> Login as root. Password is &quot;root&quot; (Note, these virtual machines are
 networked together, but are not configured to talk to the rest of the
 world.)</LI>
<LI> verify that pluto started on east/west, run &quot;ipsec look&quot;</LI>
<LI> login to sunrise. run &quot;ping sunset&quot;</LI>
<LI> login to west. run &quot;tcpdump -p -i eth1 -n&quot; (tcpdump must be version
 3.7.1 or newer)</LI>
<LI> Closing a console xterm will shut down that UML.</LI>
<LI> You can &quot;make check&quot;, if you want to. It is run from
 /c2/freeswan/sandbox/freeswan-1.97.</LI>
</OL>
<H1><A NAME="35">Debugging the kernel with GDB</A></H1>
<P> With User-Mode-Linux, you can debug the kernel using GDB. See
<!--HREF="http://user-mode-linux.sourceforge.net/debugging.html"-->

 http://user-mode-linux.sourceforge.net/debugging.html.</(null)></P>
<P> Typically, one will want to address a test case for a failing
 situation. Running GDB from Emacs, or from other front ends is
 possible. First start GDB.</P>
<P> Tell it to open the UMLPOOL/swan/linux program.</P>
<P> Note the PID of GDB:</P>
<PRE>
marajade-[projects/freeswan/mgmt/planning] mcr 1029 %ps ax | grep gdb
 1659 pts/9    SN     0:00 /usr/bin/gdb -fullname -cd /mara4/freeswan/kernpatch/UMLPOOL/swan/ linux
</PRE>
<P> Set the following in the environment:</P>
<PRE>
UML_east_OPT=&quot;debug gdb-pid=1659&quot;
</PRE>
<P> Then start the user-mode-linux in the test scheme you wish:</P>
<PRE>
marajade-[kernpatch/testing/klips/east-icmp-02] mcr 1220 %../../utils/runme.sh
</PRE>
 The user-mode-linux will stop on boot, giving you a chance to attach to
 the process:
<PRE>
(gdb) file linux
Reading symbols from linux...done.
(gdb) attach 1
Attaching to program: /mara4/freeswan/kernpatch/UMLPOOL/swan/linux, process 1
0xa0118bc1 in kill () at hostfs_kern.c:770
</PRE>
<P> At this point, break points should be created as appropriate.</P>
<H2><A NAME="35_1">Other notes about debugging</A></H2>
<P> If you are running a standard test, after all the packets are sent,
 the UML will be shutdown. This can cause problems, because the UML may
 get terminated while you are debugging.</P>
<P> The environment variable <CODE>NETJIGWAITUSER</CODE> can be set to
 &quot;waituser&quot;. If so, then the testing system will prompt before exiting
 the test.</P>
<H1><A NAME="36">User-Mode-Linux mysteries</A></H1>
<UL>
<LI> running more than one UML of the same name (e.g. &quot;west&quot;) can cause
 problems.</LI>
<LI> running more than one UML from the same root file system is not a
 good idea.</LI>
<LI> all this means that running &quot;make check&quot; twice on the same machine
 is probably not a good idea.</LI>
<LI> occationally, UMLs will get stuck. This can happen like:
<!--BLOCK-->
 15134 ? T
 0:00 /spare/hugh/uml/uml2.4.18-sept5/umlbuild/east/linux (east)
 [/bin/sh] 15138 ? T 0:00
 /spare/hugh/uml/uml2.4.18-sept5/umlbuild/east/linux (east) [halt]</(null)>
 these will need to be killed. Note that they are in &quot;T&quot;racing mode.</LI>
<LI> UMLs can also hang, and will report &quot;Tracing myself and I can't get
 out&quot;. This is a bug in UML. There are ways to find out what is going on
 and report this to the UML people, but we don't know the magic right
 now.</LI>
</UL>
<H1><A NAME="37">Getting more info from uml_netjig</A></H1>
<P> uml_netjig can be compiled with a built-in tcpdump. This uses
 not-yet-released code from<A HREF="http://www.tcpdump.org/">
 www.tcpdump.org</A>. Please see the instructions in <CODE>
testing/utils/uml_netjig/Makefile</CODE>.</P>
<HR>
<H1><A name="makecheck">How to configure to use &quot;make check&quot;</A></H1>
<H2><A NAME="38_1">What is &quot;make check&quot;</A></H2>
<P> &quot;make check&quot; is a target in the top level makefile. It takes care of
 running a number of unit and system tests to confirm that FreeSWAN has
 been compiled correctly, and that no new bugs have been introduced.</P>
<P> As FreeSWAN contains both kernel and userspace components, doing
 testing of FreeSWAN requires that the kernel be simulated. This is
 typically difficult to do as a kernel requires that it be run on bare
 hardware. A technology has emerged that makes this simpler. This is<A HREF="http://user-mode-linux.sourceforge.net">
 User Mode Linux</A>.</P>
<P> User-Mode Linux is a way to build a Linux kernel such that it can
 run as a process under another Linux (or in the future other) kernel.
 Presently, this can only be done for 2.4 guest kernels. The host kernel
 can be 2.2 or 2.4.</P>
<P> &quot;make check&quot; expects to be able to build User-Mode Linux kernels
 with FreeSWAN included. To do this it needs to have some files
 downloaded and extracted prior to running &quot;make check&quot;. This is
 described in the<A HREF="umltesting.html"> UML testing</A> document.</P>
<P> After having run the example in the UML testing document and
 successfully brought up the four machine combination, you are ready to
 use &quot;make check&quot;</P>
<H2><A NAME="38_2">Running &quot;make check&quot;</A></H2>
<P> &quot;make check&quot; works by walking the FreeSWAN source tree invoking the
 &quot;check&quot; target at each node. At present there are tests defined only
 for the <CODE>klips</CODE> directory. These tests will use the UML
 infrastructure to test out pieces of the <CODE>klips</CODE> code.</P>
<P> The results of the tests can be recorded. If the environment
 variable <CODE>$REGRESSRESULTS</CODE> is non-null, then the results of
 each test will be recorded. This can be used as part of a nightly
 regression testing system, see<A HREF="nightly.html"> Nightly testing</A>
 for more details.</P>
<P> &quot;make check&quot; otherwise prints a minimal amount of output for each
 test, and indicates pass/fail status of each test as they are run.
 Failed tests do not cause failure of the target in the form of exit
 codes.</P>
<H1><A NAME="39">How to write a &quot;make check&quot; test</A></H1>
<H2><A NAME="39_1">Structure of a test</A></H2>
<P> Each test consists of a set of directories under <CODE>testing/</CODE>
. There are directories for <CODE>klips</CODE>, <CODE>pluto</CODE>, <CODE>
packaging</CODE> and <CODE>libraries</CODE>. Each directory has a list
 of tests to run is stored in a file called <CODE>TESTLIST</CODE> in
 that directory. e.g. <CODE>testing/klips/TESTLIST</CODE>.</P>
<H2 NAME="TESTLIST"><A NAME="39_2">The TESTLIST</A></H2>
<P> This isn't actually a shell script. It just looks like one. Some
 tools other than /bin/sh process it. Lines that start with # are
 comments.</P>
<PRE>
# test-kind     directory-containing-test       expectation     [PR#]
</PRE>
<P>The first word provides the test type, detailed below.</P>
<P> The second word is the name of the test to run. This the directory
 in which the test case is to be found..</P>
<P>The third word may be one of:</P>
<DL>
<DT> blank/good</DT>
<DD>the test is believed to function, report failure</DD>
<DT> bad</DT>
<DD> the test is known to fail, report unexpected success</DD>
<DT> suspended</DT>
<DD> the test should not be run</DD>
</DL>
<P> The fourth word may be a number, which is a PR# if the test is
 failing.</P>
<H2><A NAME="39_3">Test kinds</A></H2>
 The test types are:
<DL>
<DT>skiptest</DT>
<DD>means run no test.</DD>
<DT>ctltest</DT>
<DD>means run a single system without input/output.</DD>
<DT>klipstest</DT>
<DD>means run a single system with input/output networks</DD>
<DT><A HREF="#umlplutotest">umlplutotest</A></DT>
<DD>means run a pair of systems</DD>
<DT><A HREF="#umlXhost">umlXhost</A></DT>
<DD>run an arbitrary number of systems</DD>
<DT>suntest (TBD)</DT>
<DD>means run a quad of east/west/sunrise/sunset</DD>
<DT>roadtest (TBD)</DT>
<DD>means run a trio of east-sunrise + warrior</DD>
<DT>extrudedtest (TBD)</DT>
<DD>means run a quad of east-sunrise + warriorsouth + park</DD>
<DT>mkinsttest</DT>
<DD>a test of the &quot;make install&quot; machinery.</DD>
<DT>kernel_test_patch</DT>
<DD>a test of the &quot;make kernelpatch&quot; machinery.</DD>
</DL>
 Tests marked (TBD) have yet to be fully defined.
<P> Each test directory has a file in it called <CODE>testparams.sh</CODE>
. This file sets a number of environment variables to define the
 parameters of the test.</P>
<H2><A NAME="39_4">Common parameters</A></H2>
<DL>
<DT>TESTNAME</DT>
<DD>the name of the test (repeated for checking purposes)</DD>
<DT>TEST_TYPE</DT>
<DD>the type of the test (repeat of type type above)</DD>
<DT>TESTHOST</DT>
<DD>the name of the UML machine to run for the test, typically &quot;east&quot; or
 &quot;west&quot;</DD>
<DT>TEST_PURPOSE</DT>
<DD>The purpose of the test is one of:
<DL>
<DT>goal</DT>
<DD>The goal purpose is where a test is defined for code that is not yet
 finished. The test indicates when the goals have in fact been reached.</DD>
<DT>regress</DT>
<DD>This is a test to determine that a previously existing bug has been
 repaired. This test will initially be created to reproduce the bug in
 isolation, and then the bug will be fixed.</DD>
<DT>exploit</DT>
<DD>This is a set of packets/programs that causes a vulnerability to be
 exposed. It is a specific variation of the regress option.</DD>
</DL>
</DD>
<DT>TEST_GOAL_ITEM</DT>
<DT></DT>
<DD>in the case of a goal test, this is a reference to the requirements
 document</DD>
<DT>TEST_PROB_REPORT</DT>
<DD>in the case of regression test, this the problem report number from
 GNATS</DD>
<DT>TEST_EXPLOIT_URL</DT>
<DD>in the case of an exploit, this is a URL referencing the paper
 explaining the origin of the test and the origin of exploit software</DD>
<DT>REF_CONSOLE_OUTPUT</DT>
<DD>a file in the test directory that contains the sanitized console
 output against which to compare the output of the actual test.</DD>
<DT>REF_CONSOLE_FIXUPS</DT>
<DD>a list of scripts (found in <CODE>klips/test/fixups</CODE>) to apply
 to sanitize the console output of the machine under test. These are
 typically perl, awk or sed scripts that remove things in the kernel
 output that change each time the test is run and/or compiled.</DD>
<DT>INIT_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode prior to starting the tests. This file will usually
 set up any eroute's and SADB entries that are required for the test.</P>
<P>Lines beginning with # are skipped. Blank lines are skipped.
 Otherwise, a shell prompted is waited for each time (consisting of <CODE>
\n#</CODE>) and then the command is sent. Note that the prompt is waited
 for before the command and not after, so completion of the last command
 in the script is not required. This is often used to invoke a program
 to monitor the system, e.g. <CODE>ipsec pf_key</CODE>.</P>
</DD>
<DT>RUN_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode, before the packets are sent. On single machine tests,
 this script doesn't provide any more power than INIT_SCRIPT, but is
 implemented for consistency's sake.</P>
</DD>
<DT>FINAL_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode after the final packet is sent. Similar to
 INIT_SCRIPT, above. If not specified, then the single command &quot;halt&quot; is
 sent. If specified, then the script should end with a halt command to
 nicely shutdown the UML.</P>
</DD>
<DT>CONSOLEDIFFDEBUG</DT>
<DD>If set to &quot;true&quot; then the series of console fixups (see
 REF_CONSOLE_FIXUPS) will be output after it is constructed. (It should
 be set to &quot;false&quot;, or unset otherwise)</DD>
<DT>NETJIGDEBUG</DT>
<DD>If set to &quot;true&quot; then the series of console fixups (see
 REF_CONSOLE_FIXUPS) will be output after it is constructed. (It should
 be set to &quot;false&quot;, or unset otherwise)</DD>
<DT>NETJIGTESTDEBUG</DT>
<DD> If set to &quot;netjig&quot;, then the results of talking to the <CODE>
uml_netjig</CODE> will be printed to stderr during the test. In
 addition, the jig will be invoked with --debug, which causes it to log
 its process ID, and wait 60 seconds before continuing. This can be used
 if you are trying to debug the <CODE>uml_netjig</CODE> program itself.</DD>
<DT>HOSTTESTDEBUG</DT>
<DD> If set to &quot;hosttest&quot;, then the results of taling to the consoles of
 the UMLs will be printed to stderr during the test.</DD>
<DT>NETJIGWAITUSER</DT>
<DD> If set to &quot;waituser&quot;, then the scripts will wait forever for user
 input before they shut the tests down. Use this is if you are debugging
 through the kernel.</DD>
<DT>PACKETRATE</DT>
<DD> A number, in miliseconds (default is 500ms) at which packets will
 be replayed by the netjig.</DD>
</DL>
<H2><A NAME="39_5">KLIPStest paramaters</A></H2>
<P> The klipstest function starts a program (<CODE>
testing/utils/uml_netjig/uml_netjig</CODE>) to setup a bunch of I/O
 sockets (that simulate network interfaces). It then exports the
 references to these sockets to the environment and invokes (using
 system()) a given script. It waits for the script to finish.</P>

<!-- <IMG SRC="single_netjig.png" ALT="block diagram of uml_netjig"> -->
<P> The script invoked (<CODE>testing/utils/host-test.tcl</CODE>) is a
 TCL<A HREF="http://expect.nist.gov/"> expect</A> script that arranges
 to start the UML and configure it appropriately for the test. The
 configuration is done with the script given above for<VAR> INIT_SCRIPT</VAR>
. The TCL script then forks, leaves the UML in the background and exits.
 uml_netjig continues. It then starts listening to the simulated network
 answering ARPs and inserting packets as appropriate.</P>
<P> The klipstest function invokes <CODE>uml_netjig</CODE> with
 arguments to capture output from network interface(s) and insert
 packets as appropriate:</P>
<DL>
<DT>PUB_INPUT</DT>
<DD>a<A HREF="http://www.tcpdump.org/"> pcap</A> file to feed in on the
 public (encrypted) interface. (typically, eth1)</DD>
<DT>PRIV_INPUT</DT>
<DD>a pcap file to feed in on the private (plain-text) interface
 (typically, eth0).</DD>
<DT>REF_PUB_OUTPUT</DT>
<DD>a text file containing tcpdump output. Packets on the public (eth1)
 interface are captured to a<A HREF="http://www.tcpdump.org/"> pcap</A>
 file by <CODE>uml_netjig</CODE>. The klipstest function then uses
 tcpdump on the file to produce text output, which is compared to the
 file given.</DD>
<DT>REF_PUB_FILTER</DT>
<DD>a program that will filter the TCPDUMP output to do further
 processing. Defaults to &quot;cat&quot;.</DD>
<DT>REF_PRIV_OUTPUT</DT>
<DD>a text file containing tcpdump output. Packets on the private (eth0)
 interface are captured and compared after conversion by tcpdump, as
 with<VAR> REFPUBOUTPUT</VAR>.</DD>
<DT>REF_PRIV_FILTER</DT>
<DD>a program that will filter the TCPDUMP output to do further
 processing. Defaults to &quot;cat&quot;.</DD>
<DT>EXITONEMPTY</DT>
<DD>a flag for <CODE>uml_netjig</CODE>. It should contain
 &quot;--exitonempty&quot; of uml_netjig should exit when all of the input (<VAR>
PUBINPUT</VAR>,<VAR>PRIVINPUT</VAR>) packets have been injected.</DD>
<DT>ARPREPLY</DT>
<DD>a flag for <CODE>uml_netjig</CODE>. It should contain &quot;--arpreply&quot;
 if <CODE>uml_netjig</CODE> should reply to ARP requests. One will
 typically set this to avoid having to fudge the ARP cache manually.</DD>
<DT>TCPDUMPFLAGS</DT>
<DD>a set of flags for the tcpdump used when converting captured output.
 Typical values will include &quot;-n&quot; to turn off DNS, and often &quot;-E&quot; to set
 the decryption key (tcpdump 3.7.1 and higher only) for ESP packets. The
 &quot;-t&quot; flag (turn off timestamps) is provided automatically</DD>
<DT>NETJIG_EXTRA</DT>
<DD>additional comments to be sent to the netjig. This may arrange to
 record or create additional networks, or may toggle options.</DD>
</DL>
<H2><A NAME="39_6">mkinsttest paramaters</A></H2>
<P> The basic concept of the <CODE>mkinsttest</CODE> test type is that
 it performs a &quot;make install&quot; to a temporary $DESTDIR. The resulting
 tree can then be examined to determine if it was done properly. The
 files can be uninstalled to determine if the file list was correct, or
 the contents of files can be examined more precisely.</P>
<DL>
<DT>INSTALL_FLAGS</DT>
<DD>If set, then an install will be done. This provides the set of flags
 to provide for the install. The target to be used (usually &quot;install&quot;)
 must be among the flags.</DD>
<DT>POSTINSTALL_SCRIPT</DT>
<DD>If set, a script to run after initial &quot;make install&quot;. Two arguments
 are provided: an absolute path to the root of the FreeSWAN src tree,
 and an absolute path to the temporary installation area.</DD>
<DT>INSTALL2_FLAGS</DT>
<DD>If set, a second install will be done using these flags. Similarly
 to INSTALL_FLAGS, the target must be among the flags.</DD>
<DT>UNINSTALL_FLAGS</DT>
<DD>If set, an uninstall will be done using these flags. Similarly to
 INSTALL_FLAGS, the target (usually &quot;uninstall&quot;) must be among the
 flags.</DD>
<DT>REF_FIND_f_l_OUTPUT</DT>
<DD>If set, a <CODE>find $ROOT ( -type f -or -type -l )</CODE> will be
 done to get a list of a real files and symlinks. The resulting file
 will be compared to the file listed by this option.</DD>
<DT>REF_FILE_CONTENTS</DT>
<DD>If set, it should point to a file containing records for the form:
<PRE>
  
<!--VARIABLE-->
reffile</(null)>   
<!--VARIABLE-->
samplefile</(null)>
</PRE>
 one record per line. A diff between the provided reference file, and
 the sample file (located in the temporary installation root) will be
 done for each record.</DD>
</DL>
<H2><A NAME="39_7">rpm_build_install_test paramaters</A></H2>
<P> The <CODE>rpm_build_install_test</CODE> type is to verify that the
 proper packing list is produced by &quot;make rpm&quot;, and that the mechanisms
 for building the kernel modules produce consistent results.</P>
<DL>
<DT>RPM_KERNEL_SOURCE</DT>
<DD>Point to an extracted copy of the RedHat kernel source code.
 Variables from the environment may be used.</DD>
<DT>REF_RPM_CONTENTS</DT>
<DD>This is a file containing one record per line. Each record consists
 of a RPM name (may contain wildcards) and a filename to compare the
 contents to. The RPM will be located and a file list will be produced
 with rpm2cpio.</DD>
</DL>
<H2><A NAME="39_8">libtest paramaters</A></H2>
<P> The libtest test is for testing library routines. The library file
 is expected to provided an <CODE>#ifdef</CODE> by the name of<VAR>
 library</VAR>
<!--CODE_MAIN</CODE-->
. The libtest type invokes the C compiler to compile this
 file, links it against <CODE>libfreeswan.a</CODE> (to resolve any other
 dependancies) and runs the test with the <CODE>-r</CODE> argument to
 invoke a regression test.</(null)></P>
<P>The library test case is expected to do a self-test, exiting with
 status code 0 if everything is okay, and with non-zero otherwise. A
 core dump (exit code greater than 128) is noted specifically.</P>
<P> Unlike other tests, there are no subdirectories required, or other
 parameters to set.</P>
<H2 NAME="umlplutotest"><A NAME="39_9">umlplutotest paramaters</A></H2>
<P> The umlplutotest function starts a pair of user mode line processes.
 This is a 2-host version of umlXhost. The &quot;EAST&quot; and &quot;WEST&quot; slots are
 defined.</P>
<H2 NAME="umlXhost"><A NAME="39_10">umlXhost parameters</A></H2>
<P> The umlXtest function starts an arbitrary number of user mode line
 processes.</P>

<!-- <IMG SRC="single_netjig.png" ALT="block diagram of uml_netjig"> -->
<P> The script invoked (<CODE>testing/utils/Xhost-test.tcl</CODE>) is a
 TCL<A HREF="http://expect.nist.gov/"> expect</A> script that arranges
 to start each UML and configure it appropriately for the test. It then
 starts listening (using uml_netjig) to the simulated network answering
 ARPs and inserting packets as appropriate.</P>
<P> umlXtest has a series of slots, each of which should be filled by a
 host. The list of slots is controlled by the variable, XHOST_LIST. This
 variable should be set to a space seperated list of slots. The former
 umlplutotest is now implemented as a variation of the umlXhost test,
 with XHOST_LIST=&quot;EAST WEST&quot;.</P>
<P> For each host slot that is defined, a series of variables should be
 filled in, defining what configuration scripts to use for that host.</P>
<P> The following are used to control the console input and output to
 the system. Where the string ${host} is present, the host slot should
 be filled in. I.e. for the two host system with XHOST_LIST=&quot;EAST WEST&quot;,
 then the variables: EAST_INIT_SCRIPT and WEST_INIT_SCRIPT will exist.</P>
<DL>
<DT>${host}HOST</DT>
<DD>The name of the UML host which will fill this slot</DD>
<DT>${host}_INIT_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode prior to starting the tests. This file will usually
 set up any eroute's and SADB entries that are required for the test.
 Similar to INIT_SCRIPT, above.</P>
</DD>
<DT>${host}_RUN_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode, before the packets are sent. This set of commands is
 run after all of the virtual machines are initialized. I.e. after
 EAST_INIT_SCRIPT<B> AND</B> WEST_INIT_SCRIPT. This script can therefore
 do things that require that all machines are properly configured.</P>
</DD>
<DT>${host}_RUN2_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode, after the packets are sent. This set of commands is
 run before any of the virtual machines have been shut down. (I.e.
 before EAST_FINAL_SCRIPT<B> AND</B> WEST_FINAL_SCRIPT.) This script can
 therefore catch post-activity status reports.</P>
</DD>
<DT>${host}_FINAL_SCRIPT</DT>
<DD>
<P>a file of commands that is fed into the virtual machine's console in
 single user mode after the final packet is sent. Similar to
 INIT_SCRIPT, above. If not specified, then the single command &quot;halt&quot; is
 sent. Note that when this script is run, the other virtual machines may
 already have been killed. If specified, then the script should end with
 a halt command to nicely shutdown the UML.</P>
</DD>
<DT>REF_${host}_CONSOLE_OUTPUT</DT>
<DD>Similar to REF_CONSOLE_OUTPUT, above.</DD>
</DL>
<P>Some additional flags apply to all hosts:</P>
<DL>
<DT>REF_CONSOLE_FIXUPS</DT>
<DD>a list of scripts (found in <CODE>klips/test/fixups</CODE>) to apply
 to sanitize the console output of the machine under test. These are
 typically perl, awk or sed scripts that remove things in the kernel
 output that change each time the test is run and/or compiled.</DD>
</DL>
<P> In addition to input to the console, the networks may have input fed
 to them:</P>
<DL>
<DT>EAST_INPUT/WEST_INPUT</DT>
<DD>a<A HREF="http://www.tcpdump.org/"> pcap</A> file to feed in on the
 private network side of each network. The &quot;EAST&quot; and &quot;WEST&quot; here refer
 to the networks, not the hosts.</DD>
<DT>REF_PUB_FILTER</DT>
<DD>a program that will filter the TCPDUMP output to do further
 processing. Defaults to &quot;cat&quot;.</DD>
<DT>REF_EAST_FILTER/REF_WEST_FILTER</DT>
<DD>a program that will filter the TCPDUMP output to do further
 processing. Defaults to &quot;cat&quot;.</DD>
&lt;
<DT>TCPDUMPFLAGS</DT>
<DD>a set of flags for the tcpdump used when converting captured output.
 Typical values will include &quot;-n&quot; to turn off DNS, and often &quot;-E&quot; to set
 the decryption key (tcpdump 3.7.1 and higher only) for ESP packets. The
 &quot;-t&quot; flag (turn off timestamps) is provided automatically</DD>
<DT>REF_EAST_OUTPUT/REF_WEST_OUTPUT</DT>
<DD>a text file containing tcpdump output. Packets on the private (eth0)
 interface are captured and compared after conversion by tcpdump, as
 with<VAR> REF_PUB_OUTPUT</VAR>.</DD>
<P> There are two additional environment variables that may be set on
 the command line:</P>
<DL>
<DT> NETJIGVERBOSE=verbose export NETJIGVERBOSE</DT>
<DD> If set, then the test output will be &quot;chatty&quot;, and let you know
 what commands it is running, and as packets are sent. Without it set,
 the output is limited to success/failure messages.</DD>
<DT> NETJIGTESTDEBUG=netjig export NETJIGTESTDEBUG</DT>
<DD> This will enable debugging of the communication with uml_netjig,
 and turn on debugging in this utility. This does not imply
 NETJIGVERBOSE.</DD>
</DL>
<DT> HOSTTESTDEBUG=hosttest export HOSTTESTDEBUG</DT>
<DD> This will show all interactions with the user-mode-linux consoles</DD>
</DL>
<H2 NAME="kernelpatch"><A NAME="39_11">kernel_patch_test paramaters</A></H2>
<P> The kernel_patch_test function takes some kernel source, copies it
 with lndir, and then applies the patch as produced by &quot;make
 kernelpatch&quot;.</P>
<P> The following are used to control the input and output to the
 system:</P>
<DL>
<DT>KERNEL_NAME</DT>
<DD>the kernel name, typically something like &quot;linus&quot; or &quot;rh&quot;</DD>
<DT>KERNEL_VERSION</DT>
<DD>the kernel version number, as in &quot;2.2&quot; or &quot;2.4&quot;.</DD>
<DT>KERNEL_${KERNEL_NAME}${KERNEL_VERSION}_SRC</DT>
<DD>This variable should set in the environment, probably in
 ~/freeswan-regress-env.sh. Examples of this variables would be
 KERNEL_LINUS2_0_SRC or KERNEL_RH7_3_SRC. This variable should point to
 an extracted copy of the kernel source in question.</DD>
<DT>REF_PATCH_OUTPUT</DT>
<DD>a copy of the patch output to compare against</DD>
<DT>KERNEL_PATCH_LEAVE_SOURCE</DT>
<DD>If set to a non-empty string, then the patched kernel source is not
 removed at the end of the test. This will typically be set in the
 environment while debugging.</DD>
</DL>
<H2 NAME="modtest"><A NAME="39_12">module_compile paramaters</A></H2>
<P> The module_compile test attempts to build the KLIPS module against a
 given set of kernel source. This is also done by the RPM tests, but in
 a very specific manner.</P>
<P> There are two variations of this test - one where the kernel either
 doesn't need to be configured, or is already done, and tests were there
 is a local configuration file.</P>
<P> Where the kernel doesn't need to be configured, the kernel source
 that is found is simply used. It may be a RedHat-style kernel, where
 one can cause it to configure itself via rhconfig.h-style definitions.
 Or, it may just be a kernel tree that has been configured.</P>
<P> If the variable KERNEL_CONFIG_FILE is set, then a new directory is
 created for the kernel source. It is populated with lndir(1). The
 referenced file is then copied in as .config, and &quot;make oldconfig&quot; is
 used to configure the kernel. This resulting kernel is then used as the
 reference source.</P>
<P> In all cases, the kernel source is found the same was for the
 kernelpatch test, i.e. via KERNEL_VERSION/KERNEL_NAME and
 KERNEL_${KERNEL_NAME}${KERNEL_VERSION}_SRC.</P>
<P> Once there is kernel source, the module is compiled using the
 top-level &quot;make module&quot; target.</P>
<P> The test is considered successful if an executable is found in
 OUTPUT/module/ipsec.o at the end of the test.</P>
<DL>
<DT>KERNEL_NAME</DT>
<DD>the kernel name, typically something like &quot;linus&quot; or &quot;rh&quot;</DD>
<DT>KERNEL_VERSION</DT>
<DD>the kernel version number, as in &quot;2.2&quot; or &quot;2.4&quot;.</DD>
<DT>KERNEL_${KERNEL_NAME}${KERNEL_VERSION}_SRC</DT>
<DD>This variable should set in the environment, probably in
 ~/freeswan-regress-env.sh. Examples of this variables would be
 KERNEL_LINUS2_0_SRC or KERNEL_RH7_3_SRC. This variable should point to
 an extracted copy of the kernel source in question.</DD>
<DT>KERNEL_CONFIG_FILE</DT>
<DD>The configuration file for the kernel.</DD>
<DT>KERNEL_PATCH_LEAVE_SOURCE</DT>
<DD>If set to a non-empty string, then the configured kernel source is
 not removed at the end of the test. This will typically be set in the
 environment while debugging.</DD>
<DT>MODULE_DEF_INCLUDE</DT>
<DD>The include file that will be used to configure the KLIPS module,
 and possibly the kernel source.</DD>
</DL>
<H1><A NAME="40">Current pitfalls</A></H1>
<DL>
<DT> &quot;tcpdump dissector&quot; not available.</DT>
<DD> This is a non-fatal warning. If uml_netjig is invoked with the -t
 option, then it will attempt to use tcpdump's dissector to decode each
 packet that it processes. The dissector is presently not available, so
 this option it normally turned off at compile time. The dissector
 library will be released with tcpdump version 4.0.</DD>
</DL>
<HR>
<H1><A name="nightly">Nightly regression testing</A></H1>
<P> The nightly regression testing system consists of several shell
 scripts and some perl scripts. The goal is to check out a fresh tree,
 run &quot;make check&quot; on it, record the results and summarize the results to
 the team and to the web site.</P>
<P> Output can be found on<A HREF="http://bugs.freeswan.org:81/"> adams</A>
, although the tests are actually run on another project machine.</P>
<H1><A name="nightlyhowto">How to setup the nightly build</A></H1>
<P> The best way to do nightly testing is to setup a new account. We
 call the account &quot;build&quot; - you could call it something else, but there
 may still be some references to ~build in the scripts.</P>
<H2><A NAME="42_1"> Files you need to know about</A></H2>
<P> As few files as possible need to be extracted from the source tree -
 files are run from the source tree whenever possible. However, there
 are some bootstrap and configuration files that are necessary.</P>
<P> There are 7 files in testing/utils that are involved:</P>
<DL>
<DT> nightly-sample.sh</DT>
<DD> This is the root of the build process. This file should be copied
 out of the CVS tree, to $HOME/bin/nightly.sh of the build account. This
 file should be invoked from cron.</DD>
<DT> freeswan-regress-env-sample.sh</DT>
<DD> This file should be copied to $HOME/freeswan-regress-env.sh. It
 should be edited to localize the values. See below.</DD>
<DT> regress-cleanup.pl</DT>
<DD> This file needs to be copied to $HOME/bin/regress-cleanup.pl. It is
 invoked by the nightly file before doing anything else. It removes
 previous nights builds in order to free up disk space for the build
 about to be done.</DD>
<DT> teammail-sample.sh</DT>
<DD> A script used to send results email to the &quot;team&quot;. This sample
 script could be copied to $HOME/bin/teammail.sh. This version will PGP
 encrypt all the output to the team members. If this script is used,
 then PGP will have to be properly setup to have the right keys.</DD>
<DT> regress-nightly.sh</DT>
<DD> This is the first stage of the nightly build. This stage will call
 other scripts as appropriate, and will extract the source code from
 CVS. This script should be copied to $HOME/bin/regress-nightly.sh</DD>
<DT> regress-stage2.sh</DT>
<DD> This is the second stage of the nightly build. It is called in
 place. It essentially sets up the UML setup in umlsetup.sh, and calls
 &quot;make check&quot;.</DD>
<DT> regress-summarize-results.pl</DT>
<DD> This script will summarize the results from the tests to a
 permanent directory set by $REGRESSRESULTS. It is invoked from the
 stage2 nightly script.</DD>
<DT> regress-chart.sh</DT>
<DD> This script is called at the end of the build process, and will
 summarize each night's results (as saved into $REGRESSRESULTS by
 regress-summarize-results.pl) as a chart using gnuplot. Note that this
 requires at least gnuplot 3.7.2.</DD>
</DL>
<H2><A NAME="42_2">Configuring freeswan-regress-env.sh</A></H2>
<P>For more info on KERNPOOL, UMLPATCH, BASICROOT and SHAREDIR, see<A HREF="umltesting.html">
 User-Mode-Linux testing guide</A>.</P>
<DL>
<DT> KERNPOOL</DT>
<DD> Extract copy of some kernel source to be used for UML builds</DD>
<DT> UMLPATCH</DT>
<DD> matching User-Mode-Linux patch.</DD>
<DT> BASICROOT</DT>
<DD> the root file system image (see<A HREF="umltesting.html">
 User-Mode-Linux testing guide</A>).</DD>
<DT> SHAREDIR=${BASICROOT}/usr/share</DT>
<DD> The /usr/share to use.</DD>
<DT> REGRESSTREE</DT>
<DD> A directory in which to store the nightly regression results.
 Directories will be created by date in this tree.</DD>
<DT> TCPDUMP=tcpdump-3.7.1</DT>
<DD> The path to the<A HREF="http://www.tcpdump.org/"> tcpdump</A> to
 use. This must have crypto compiled in, and must be at least 3.7.1</DD>
<DT> KERNEL_RH7_2_SRC=/a3/kernel_sources/linux-2.4.9-13/</DT>
<DD> An extracted copy of the RedHat 7.2. kernel source. If set, then
 the packaging/rpm-rh72-install-01 test will be run, and an RPM will be
 built as a test.</DD>
<DT> KERNEL_RH7_3_SRC=/a3/kernel_sources/rh/linux-2.4.18-5</DT>
<DD> An extracted copy of the RedHat 7.3. kernel source. If set, then
 the packaging/rpm-rh73-install-01 test will be run, and an RPM will be
 built as a test.</DD>
<DT> NIGHTLY_WATCHERS=&quot;userid,userid,userid&quot;</DT>
<DD> The list of people who should receive nightly output. This is used
 by teammail.sh</DD>
<DT> FAILLINES=128</DT>
<DD> How many lines of failed test output to include in the nightly
 output</DD>
<DT> PATH=$PATH:/sandel/bin export PATH</DT>
<DD> You can also override the path if necessary here.</DD>
<DT> CVSROOT=:pserver:anoncvs@ip212.xs4net.freeswan.org:/freeswan/MASTER</DT>
<DD> The CVSROOT to use. This example may work for anonymous CVS, but
 will be 12 hours behind the primary, and is still experimental</DD>
<DT> SNAPSHOTSIGDIR=$HOME/snapshot-sig</DT>
<DD> For the release tools, where to put the generated per-snapshot
 signature keys</DD>
<DT> LASTREL=1.97</DT>
<DD> the name of the last release branch (to find the right per-snapshot
 signature</DD>
<DD></DD>
</DL>
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