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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<tr>
<th colspan="3" align="center">LPRng-HOWTO: 1 Apr 2002
(For LPRng-3.8.10)</th>
</tr>
<tr>
<td width="10%" align="left" valign="bottom"><a href=
"x8993.htm" accesskey="P">Prev</a></td>
<td width="80%" align="center" valign="bottom">Chapter
17. Permissions and Authentication</td>
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"x9264.htm" accesskey="N">Next</a></td>
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<hr align="LEFT" width="100%">
</div>
<div class="SECT1">
<h1 class="SECT1"><a name="KERBEROS">17.14. Using Kerberos 5
for Authentication</a></h1>
<p><b class="APPLICATION">LPRng</b> Kerberos 5 authentication
is based on the Kerberos5-1.2.4 release as of 3 March 2020.
The distribution was obtained from MIT from the <i class=
"EMPHASIS"><a href="http://web.mit.edu/kerberos/www/" target=
"_top">http://web.mit.edu/kerberos/www/</a></i> Website.</p>
<p>The following sections briefly describes how to set up and
test the Kerberos software and then how to configure <b
class="APPLICATION">LPRng</b> to use Kerberos.</p>
<div class="SECT2">
<h2 class="SECT2"><a name="AEN9124">17.14.1. <b class=
"APPLICATION">LPRng</b> Configuration</a></h2>
<p>The following <tt class="LITERAL">configure</tt> options
are used to enable Kerberos support:</p>
<div class="INFORMALEXAMPLE">
<a name="AEN9129"></a>
<pre class="SCREEN">
--enable-kerberos enable Kerberos V support
--enable-mit_kerberos4 enable MIT Kerberos 4 support
--disable-kerberos_checks disable Kerberos sanity checks
</pre>
</div>
<br>
<br>
<p>The <tt class="LITERAL">--enable-kerberos</tt> option
will cause <tt class="LITERAL">configure</tt> to search for
the include files such as <tt class="FILENAME">krb5.h</tt>
and the <tt class="LITERAL">krb5</tt> support libraries.
libraries. If it finds these, then Kerberos authentication
will be included. The <tt class=
"LITERAL">--enable-mit_kerberos</tt> enable searching for
the Kerberos 4 include files and support libraries. If
these are found then MIT Kerberos 4 compatibility will be
enabled. The <tt class=
"LITERAL">--disable-kerberos_checks</tt> will disable
checking for libraries and simply enable the various
options.</p>
</div>
<div class="SECT2">
<h2 class="SECT2"><a name="AEN9138">17.14.2. Kerberos
Installation Procedure</a></h2>
<ol type="1">
<li>
<p>Get the Kerberos 5 distribution.</p>
</li>
<li>
<p>Compile and install the distribution.</p>
</li>
<li>
<p>Create the <tt class="FILENAME">/etc/krb5.conf</tt>
and <tt class=
"FILENAME">/usr/local/var/krb5kdc/kdc.conf</tt>, files
using templates from the files in the Kerberos
distribution's <tt class=
"FILENAME">src/config-files</tt> directory. See the
Kerberos Installation Guide and the Kerberos System
Administrators Guide for details.</p>
</li>
<li>
<p>Start up the KDC and KADMIN servers - you might want
to put the following in your <tt class=
"FILENAME">rc.local</tt> or equivalent system startup
files:</p>
<div class="INFORMALEXAMPLE">
<a name="AEN9154"></a>
<pre class="SCREEN">
if [ -f /etc/krb5.conf -a -f /usr/local/var/krb5kdc/kdc.conf ]; then
echo -n ' krb5kdc '; /usr/local/sbin/krb5kdc;
echo -n ' kadmind '; /usr/local/sbin/kadmind;
fi
</pre>
</div>
<br>
<br>
</li>
<li>
<p>Use kadmin (or kadmin.local) to create principals
for your users.</p>
</li>
<li>
<p>Use kadmin (or kadmin.local) to create principals
for the <b class="APPLICATION">lpd</b> servers. The
recommended method is to use <tt class=
"FILENAME">lpr/hostname@REALM</tt> as a template for
the principal name, i.e. - <tt class=
"LITERAL">lpr/astart1.private@ASTART.COM</tt> for an
example. You should use fully qualified domain names
for the principals. Do not assign the principal a
password.</p>
<div class="INFORMALEXAMPLE">
<a name="AEN9163"></a>
<pre class="SCREEN">
Example:
#> kadmin OR #> kadmin.local
kadmin: addprinc -randkey lpr/wayoff.private@ASTART.COM
quit
</pre>
</div>
<br>
<br>
</li>
<li>
<p>Extract the keytab for each server:</p>
<div class="INFORMALEXAMPLE">
<a name="AEN9167"></a>
<pre class="SCREEN">
Example:
#> kadmin OR #> kadmin.local
ktadd -k /etc/lpr.wayoff.private lpr/wayoff.private@ASTART.COM
quit
</pre>
</div>
<br>
<br>
</li>
<li>
<p>The <tt class="LITERAL">/etc/lpr.wayoff.private</tt>
file contains the keytab information which is the
equivalent of a password for a server program. You
should create these files and then copy the appropriate
<tt class="LITERAL">keytab</tt> file to <tt class=
"FILENAME">/etc/lpd.keytab</tt> file on each server.
See the warnings about of keytab files in the Kerberos
Installation and Kerberos Administration manuals. You
should copy the file using an encrypted connection, set
the permissions to read only by the owner (<tt class=
"LITERAL">400</tt>), and set the owner to <tt class=
"LITERAL">daemon</tt> or the user that <b class=
"APPLICATION">lpd</b> will run as.</p>
<div class="INFORMALEXAMPLE">
<a name="AEN9177"></a>
<pre class="SCREEN">
#> chmod 400 lpr.wayoff.com
#> scp lpr.wayoff.com root@wayoff.com:/etc/lpd.keytab
#> ssh -l root wayoff.com
# wayoff > chmod 400 /etc/lpd.keytab
# wayoff > chown daemon /etc/lpd.keytab
# wayoff > ls -l /etc/lpd.keytab
-rw------- 1 daemon wheel 128 Jan 16 11:06 /etc/lpd.keytab
</pre>
</div>
<br>
<br>
</li>
<li>
<p>If you want to have MIT Kerberos4 printing
compatibility then you will need to set up Kerberos 4
<tt class="LITERAL">servertabs</tt> instead of Kerberos
5 keytabs. Assuming that you have put the Kerberos 5
keytab in <tt class="FILENAME">/etc/lpd.keytab</tt>,
then you extract the Kerberos 4 srvtab version of the
Kerberos 5 keytab using the following commands. You
must put the key in the <tt class=
"FILENAME">/etc/srvtab</tt> file in order to be
compatible with the Kerberos 4 support.</p>
<div class="INFORMALEXAMPLE">
<a name="AEN9184"></a>
<pre class="SCREEN">
<tt class="PROMPT">h4: {321} #</tt> <tt class=
"USERINPUT"><b>ktuil</b></tt>
<tt class="USERINPUT"><b>rkt /etc/lpd.keytab</b></tt>
<tt class="USERINPUT"><b>wst /etc/srvtab</b></tt>
</pre>
</div>
<br>
<br>
</li>
</ol>
<br>
<br>
</div>
<div class="SECT2">
<h2 class="SECT2"><a name="AEN9190">17.14.3. <b class=
"APPLICATION">LPRng</b> Configuration</a></h2>
<p>The <b class="APPLICATION">LPRng</b> software needs to
be configured so that it can find the Kerberos libraries
and include files. By default, the include files are
installed in <tt class="FILENAME">/usr/local/include</tt>
and the libraries in <tt class=
"FILENAME">/usr/local/lib</tt>. Use the following steps to
configure <b class="APPLICATION">LPRng</b> so that it uses
these directories during configuration and
installation:</p>
<div class="INFORMALEXAMPLE">
<a name="AEN9198"></a>
<pre class="SCREEN">
cd .../LPRng
rm -f config.cache
CPPFLAGS="-I/usr/local/include -I/usr/include/kerberosIV" \
LDFLAGS="-L/usr/local/lib -L/usr/lib/kerberosIV" \
./configure
make clean all
su
make install
</pre>
</div>
<br>
<br>
</div>
<div class="SECT2">
<h2 class="SECT2"><a name="AEN9200">17.14.4. Printcap
Entries</a></h2>
<p>Options used:</p>
<ul>
<li>
<p><tt class="LITERAL">auth=kerberos5</tt><i class=
"EMPHASIS">use Kerberos5 authentication</i></p>
</li>
<li>
<p><tt class="LITERAL">kerberos_id=</tt><i class=
"EMPHASIS">server prinicpal name (for client
use)</i></p>
</li>
<li>
<p><tt class=
"LITERAL">kerberos_server_principal=</tt><i class=
"EMPHASIS">alias for kerberos_id</i></p>
</li>
<li>
<p><tt class="LITERAL">kerberos_forward_id=</tt><i
class="EMPHASIS">destination server used by
server</i></p>
</li>
<li>
<p><tt class=
"LITERAL">kerberos_forward_principal=</tt><i class=
"EMPHASIS">alias for kerberos_forward_id</i></p>
</li>
<li>
<p><tt class="LITERAL">kerberos_keytab=</tt><i class=
"EMPHASIS">location of the lpd server keytab
file</i></p>
</li>
<li>
<p><tt class="LITERAL">kerberos_service=</tt><i class=
"EMPHASIS">service to be used</i></p>
</li>
<li>
<p><tt class="LITERAL">kerberos_life=</tt><i class=
"EMPHASIS">lpd server ticket lifetime</i></p>
</li>
<li>
<p><tt class="LITERAL">kerberos_renew=</tt><i class=
"EMPHASIS">lpd server ticket renew</i></p>
</li>
</ul>
<br>
<br>
<p>Example printcap entry:</p>
<div class="INFORMALEXAMPLE">
<a name="AEN9241"></a>
<pre class="SCREEN">
pr:client
:lp=pr@wayoff
:auth=kerberos5
:kerberos_id=lpr/wayoff.private@ASTART.COM
pr:server
:lp=pr@faroff.private
:auth_forward=kerberos5
:kerberos_id=lpr/wayoff.private@ASTART.COM
:kerberos_forward_id=lpr/faroff.private@ASTART.COM
:kerberos_keytab=/etc/lpd.keytab
OR If you want to use Kerberos 4 authentication to the server
pr:client
:lp=pr@wayoff
:auth=kerberos4
:kerberos_id=lpr/wayoff.private@ASTART.COM
# support both Kerberos 4 and 5 on server
pr:server
:lp=pr@faroff.private
:auth_forward=kerberos5
:kerberos_id=lpr/wayoff.private@ASTART.COM
:kerberos_forward_id=lpr/faroff.private@ASTART.COM
:kerberos_keytab=/etc/lpd.keytab
</pre>
</div>
<br>
<br>
<p>The printcap configuration for Kerberos authentication
is very simple.</p>
<p>The <tt class="LITERAL">kerberos_id</tt> is the
principal name of the lpd server that clients will connect
to. For backwards compatibility, <tt class=
"LITERAL">kerberos_server_principal</tt> can also be used.
This values is used to obtain a ticket for the <b class=
"APPLICATION">lpd</b> server, and is the only entry
required for client to server authentication.</p>
<p>The other entries are used by the <b class=
"APPLICATION">lpd</b> server. <tt class=
"LITERAL">kerberos_keytab</tt> entry is the location of the
keytab file to be used by the server. This contains the
passphrase used by the server to authenticate itself and
get a ticket from the ticket server.</p>
<p>The <tt class="LITERAL">kerberos_id</tt> value is also
used by the server during the authentication process to
make sure that the correct principal name was used by the
request originator. This check has saved many hours of pain
in trying to determine why authentication is failing.</p>
<p>The <tt class="LITERAL">kerberos_life</tt> and <tt
class="LITERAL">kerberos_renew</tt> set the lifetime and
renewability of the lpd server Kerberos tickets. These
values should not be modified unless you are familiar with
the Kerberos system. There are extensive notes in the <b
class="APPLICATION">LPRng</b> source code concerning these
values. The <tt class="LITERAL">kerberos_service</tt> value
supplies the name of the service to be used when generating
a ticket. It is stronly recommended that the <tt class=
"LITERAL">kerberos_id</tt> entry be used instead.</p>
</div>
<div class="SECT2">
<h2 class="SECT2"><a name="AEN9259">17.14.5. User
Environment Variables and Files</a></h2>
<p>In order to use kerberos authentication, the user will
need to obtain a ticket from the Kerberos ticket server.
This is done using <tt class="LITERAL">kinit</tt>.</p>
<p>No other actions are required by the user.</p>
</div>
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Authentication Support</td>
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4 for Authentication</td>
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