1<HTML> 2<!-- SECTION: Getting Started --> 3<HEAD> 4 <TITLE>Using Kerberos Authentication</TITLE> 5 <LINK REL="STYLESHEET" TYPE="text/css" HREF="/cups-printable.css"> 6</HEAD> 7<BODY> 8 9<H1 CLASS="title">Using Kerberos Authentication</H1> 10 11<P>CUPS allows you to use a Key Distribution Center (KDC) for authentication on your local CUPS server and when printing to a remote authenticated queue. This document describes how to configure CUPS to use Kerberos authentication and provides links to the MIT help pages for configuring Kerberos on your systems and network.</P> 12 13 14<H2 CLASS="title"><A NAME="REQUIREMENTS">System Requirements</A></H2> 15 16<p>The following are required to use Kerberos with CUPS:</p> 17 18<ol> 19 20 <li>Heimdal Kerberos (any version) or MIT Kerberos (1.6.3 or newer)</li> 21 22 <li>Properly configured Domain Name System (DNS) infrastructure (for your servers):<ol type='a'> 23 <li>DNS server(s) with static IP addresses for all CUPS servers or configured to allow DHCP updates to the host addresses and</li> 24 <li>All CUPS clients and servers configured to use the same 25DNS server(s).</li> 26 </ol></li> 27 28 <li>Properly configured Kerberos infrastructure:<ol type='a'> 29 <li>KDC configured to allow CUPS servers to obtain Service Granting Tickets (SGTs) for the "host" service,</li> 30 <li>LDAP-based user accounts - both OpenDirectory and ActiveDirectory provide this with the KDC, and</li> 31 <li>CUPS clients and servers bound to the same KDC and LDAP 32 server(s).</li> 33 </ol></li> 34 35 <li>A "host" Service Granting Ticket (SGT) for every CUPS server</li> 36 37</ol> 38 39 40<H2 CLASS="title"><A NAME="KRB5">Configuring Kerberos on Your System</A></H2> 41 42<P>Before you can use Kerberos with CUPS, you will need to configure Kerberos on your system and setup a system as a KDC. Because this configuration is highly system and site-specific, please consult the following on-line resources provided by the creators of Kerberos at the Massachusetts Institute of Technology (MIT):</P> 43 44<UL> 45 46 <LI><A HREF="http://web.mit.edu/kerberos/">Kerberos: The Network Authentication Protocol</A></LI> 47 48 <LI><A HREF="http://web.mit.edu/macdev/KfM/Common/Documentation/faq-osx.html">Kerberos 49 on OS X Frequently Asked Questions</A></LI> 50 51</UL> 52 53<P>The Linux Documentation Project also has a HOWTO on Kerberos:</P> 54 55<UL> 56 57 <LI><A HREF="http://tldp.org/HOWTO/html_single/Kerberos-Infrastructure-HOWTO/">Kerberos 58 Infrastructure HOWTO</A></LI> 59 60</UL> 61 62 63<H2 CLASS="title"><A NAME="CUPS">Configuring CUPS to Use Kerberos</A></H2> 64 65<P>Once youhave configured Kerberos on your system(s), you can then enable Kerberos authentication by selecting the <tt>Negotiate</tt> authentication type. The simplest way to do this is using the <tt>cupsctl(8)</tt> command on your server(s):</P> 66 67<PRE CLASS="command"> 68<KBD>cupsctl DefaultAuthType=Negotiate</KBD> 69</PRE> 70 71<P>You can also enable Kerberos from the web interface by checking the <VAR>Use Kerberos Authentication</VAR> box and clicking <VAR>Change Settings</VAR>:</P> 72 73<PRE CLASS="command"> 74http://server.example.com:631/admin 75</PRE> 76 77<P>After you have enabled Kerberos authentication, use the built-in "authenticated" policy or your own custom policies with the printers you will be sharing. See <a href="policies.html">Managing Operation Policies</a> for more information.</P> 78 79 80<H2 CLASS="title"><A NAME="IMPLEMENT">Implementation Information</A></H2> 81 82<P>CUPS implements Kerberos over HTTP using GSSAPI and the service name "host". Because of limitations in the HTTP GSSAPI protocol extension, only a single domain/KDC is supported for authentication. The HTTP extension is described in <a href="http://tools.ietf.org/html/rfc4559">RFC 4559</a>.</P> 83 84<P>When doing printing tasks that require authentication, CUPS requests single-use "tickets" from your login session to authenticate who you are. These tickets give CUPS a username of the form "user@REALM", which is then converted to just "user" for purposes of user and group checks.</P> 85 86<P>In order to support printing to a shared printer, CUPS runs the IPP backend as the owner of the print job so it can obtain the necessary credentials.</P> 87 88</BODY> 89</HTML> 90