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This is yet another pam_ldap module. 

The advantages of this particular version are:

   o Support for changing passwords in LDAP, optionally
     with NDS or Active Directory servers

   o Support for the V3 client API and protocol (to minimize
     rebinds)

   o Support for Netscape's SSL API and proprietary extensions

   o Compatibility with the nss_ldap configuration file format
     and POSIX configuration profile semantics

   o Supports ypldapd LDAP locator for plug-and-play installation

   o Supports Netscape Directory Server 3.x password policies and
     password expiration controls

   o Supports access authorization on the "host" attribute of the
     account objectclass, and on group membership

   o Supports generating crypted hashes locally for use with
     OpenLDAP and other University of Michigan derived LDAP 
     servers

   o Bundled with Debian (Potato) and RedHat (Rawhide)
     distributions.

The module builds under both Linux 2.x and Solaris 2.x (see note below
regarding Solaris 7 - aka Solaris 2.7 - and above).  NOTE - you MUST
use GNU Make (Solaris Make will not work).

Thanks to fellow Aussie Chris Albone who wrote the initial
pam_ldap_auth module.

I am indebted to Doug Nazar for his contributions to
this software.

I've tested this with Netscape Directory Server 3.1 under NT and
Solaris, the University of Michigan LDAP server, and Microsoft's
Exchange Server.

pam_ldap is only secure if used with a secure SASL mechanism (like
CRAM-MD5) or with transport security (like SSL/TLS). With simple
authentication, it is less secure than using UNIX hashed passwords,
because the LDAP bind request sends the password in the clear.

Here are some possible deployment scenarios:

   o pam_ldap with account information in /etc flat files,
     kept manually in sync with LDAP

   o pam_ldap with account information in LDAP, using 
     nss_ldap

   o pam_ldap with account information in NIS, using
     ypldapd

FAQS
====

Don't forget to ensure that pam_ldap's link dependencies are
satisfied after installation (you can verify this by doing
ldd /usr/lib/security/pam_ldap.so.1). You must ensure that
any libraries that it depends on (such as the LDAP client
library) can be located by the dynamic linker. Otherwise,
libpam may fail to load the pam_ldap module.

Q: Using the Netscape LDAP library with pam_ldap on Solaris 8
- aka Solaris 2.8 - fails to link properly! David Begley writes:

There are two releases of the Netscape LDAP library, one marked
for Solaris 8 and the other marked for Solaris 2.6 - the additional
catch is that the Solaris 8 library is a 64-bit library (this is marked
on Netscape's site) whilst the other is a 32-bit library.

It doesn't matter if you have a 64-bit UltraSPARC processor running
the 64-bit Solaris kernel, if your compiler only works with 32-bit
objects then it won't successfully link the 64-bit Solaris 8
Netscape LDAP library.

GCC (up to version 2.95.2) does not work properly with 64-bit objects
under Solaris, so just use the Solaris 2.6 (32-bit) Netscape LDAP
library and everything should be fine.

Q: Can I use a third-party client LDAP library (such as Netscape's)
on Solaris 7? David Begley writes:

Yes, but if you have the Solaris 7 LDAP library installed (package
SUNWlldap or SUNWldapx) configure will find it before the third-party
library - in this case, you can't rely on the auto-lib-type detection of
configure and must use the "--with-ldap-lib=" parameter.

Q: Why does linking fail on Solaris 2.6 (complaining about
relocations remaining against libcrypt)? David Begley
writes:

In short, the problem is that GCC is looking for a shared libcrypt
(in response to the "--shared" parameter) which doesn't exist on
Solaris 2.6 (but does on Solaris 7).  The fix is quite simple, use
"-G" instead of "--shared" (could this be a GCC bug?).  This change
should already be included in newer versions of pam_ldap.

It doesn't look like libcrypt is even needed if you're using the
Netscape LDAP client library (maybe it's required for OpenLDAP?).

Q: Where is ldap_ssl.h? It's in the Netscape LDAP
C SDK. Download it from developer.netscape.com. If you
don't want to use SSL, removed -DSSL from CFLAGS. I
don't have any experience building with the SSL/TLS
support in OpenLDAP.

Q: I get an undefined symbol "re_comp" under
FreeBSD. Try linking against libgnuregex (set
LDFLAGS=-lgnuregex before configuring).

Q: I get undefined symbols "pam_sm_authenticate"
&c. Make sure that you compile with -DPIC, eg:
CFLAGS=-DPIC LDFLAGS=-lgnuregex ./configure

Q: The pam_nds_passwd, pam_ad_passwd, and 
pam_crypt options don't seem to work anymore. Why?
These have been replaced with the pam_password
attribute, which takes the values:

pam_password [clear|crypt|md5|nds|ad|exop]

clear -- send the new password in cleartext to
         the server. Use with Netscape
         Directory Server, others.

crypt -- crypt the password using the UNIX
         crypt(3) library call before updating
         userPassword.

md5   -- use inbuilt MD5 code to hash password

nds   -- do the right thing for updating 
         NDS passwords

ad    -- do the right thing for updating
         Active Directory passwords

exop  -- use the password change extended
         operation, used by OpenLDAP

Q: Connecting to my LDAPv2 server used to 
work, but doesn't anymore. Why?
LDAPv3 is now the default protocol. To
use LDAPv2, if your client library doesn't
fall back automatically, set

ldap_version 2

in /etc/ldap.conf.

Scott M. Stone <sstone@foo3.com> writes:
Your openldap libs *and* your SSL/RSAREF libs must be DYNAMIC LIBRARIES
or neither nss_ldap nor pam_ldap will work.

Q: Solaris stdio bug

Mark Blackman <mark.blackman@netscalibur.co.uk> writes:

Our problem was trigged by the Solaris bug where stdio can
only open 256 STREAMS (fopen), i.e. 
>From http://www.science.uva.nl/pub/solaris/solaris2.html

"Programs using stdio or even library calls that use stdio may break when they
have more than 256 files open as that is the stdio limit. Programs using many
filedescriptors should try and reserve a number of low numbered file
descriptors for use by stdio."

We are running a large application from Critical Path (imsd) and they open
thousands of file descriptors under load. This is not a problem, however after
all these descriptors are open and when pam_ldap is loadedp/called and it
attempts to open its config file '/etc/ldap.conf', it fails because of the
stdio bug that internally casts the 'int' file descriptor to a 'char'
representation in the FILEHANDLE structure.

To remedy this, we recommend that pam_ldap either keeps a set of compile time
specified defaults in the binary and harmless ignore the absence
of '/etc/ldap.conf' or to rewrite config file routines to use
open/close instead of the STREAMS version fopen/fclose or
to make it easy to link against SFIO
(http://www.research.att.com/sw/tools/sfio/)

SUPPORT
=======

To discuss pam_ldap and related technologies, you may
subscribe to the following mailing lists:    

        <URL:mailto:pamldap-request@padl.com>
and
        <URL:mailto:ldap-nis-request@padl.com>

Send an electronic mail message with "subscribe" in the
message body to join the list.

Note that PADL now offer commercial support on a
per-incident basis.      

To request a support incident, send email to:

	<URL:mailto:pamldap-support@padl.com>

--
PADL Software Pty Ltd
pamldap-support@padl.com
http://www.padl.com/