doc/help/kerberos.html

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   2 <!-- SECTION: Getting Started -->
   3 <HEAD>
   4         <TITLE>Using Kerberos Authentication</TITLE>
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   7
   8 <P>CUPS allows you to use a Key Distribution Center (KDC) for authentication
   9 on your local CUPS server and when printing to a remote authenticated queue.
  10 This document describes how to configure CUPS to use Kerberos authentication
  11 and provides links to the MIT help pages for configuring Kerberos on your
  12 systems and network.</P>
  13
  14
  15 <H2 CLASS="title"><A NAME="REQUIREMENTS">System Requirements</A></H2>
  16
  17 <p>The following are required to use Kerberos with CUPS:</p>
  18
  19 <ol>
  20
  21         <li>Heimdal Kerberos (any version) or MIT Kerberos (1.6.3 or newer)</li>
  22
  23         <li>Properly configured Domain Name System (DNS)
  24         infrastructure:<ol type='a'>
  25                 <li>DNS server(s) with static IP addresses for all CUPS clients
  26                 and servers or configured to allow DHCP updates to the host
  27                 addresses</li>
  28                 <li>All CUPS clients and servers configured to use the same
  29                 DNS server(s)</li>
  30         </ol></li>
  31
  32         <li>Properly configured Kerberos infrastructure:<ol type='a'>
  33                 <li>KDC configured to allow CUPS clients and servers to obtain
  34                 Service Granting Tickets (SGTs) for the "ipp" service</li>
  35                 <li>LDAP-based user accounts - both OpenDirectory and
  36                 ActiveDirectory provide this with the KDC</li>
  37                 <li>CUPS clients and servers bound to the KDC and LDAP
  38                 server(s)</li>
  39         </ol></li>
  40
  41         <li>An "ipp" Service Granting Ticket (SGT) for every CUPS client and
  42         server</li>
  43
  44 </ol>
  45
  46
  47 <H2 CLASS="title"><A NAME="KRB5">Configuring Kerberos on Your System</A></H2>
  48
  49 <P>Before you can use Kerberos with CUPS, you will need to configure
  50 Kerberos on your system and setup a system as a KDC. Because this
  51 configuration is highly system and site-specific, please consult
  52 the following on-line resources provided by the creators of Kerberos
  53 at the Massachussetts Institute of Technology (MIT):</P>
  54
  55 <UL>
  56
  57         <LI><A HREF="http://web.mit.edu/kerberos/">Kerberos: The Network
  58         Authentication Protocol</A></LI>
  59
  60         <LI><A HREF="http://web.mit.edu/macdev/KfM/Common/Documentation/faq-osx.html">Kerberos
  61         on Mac OS X Frequently Asked Questions</A></LI>
  62
  63 </UL>
  64
  65 <P>The Linux Documentation Project also has a HOWTO on Kerberos:</P>
  66
  67 <UL>
  68
  69         <LI><A HREF="http://tldp.org/HOWTO/html_single/Kerberos-Infrastructure-HOWTO/">Kerberos
  70         Infrastructure HOWTO</A></LI>
  71
  72 </UL>
  73
  74
  75 <H2 CLASS="title"><A NAME="CUPS">Configuring CUPS to Use Kerberos</A></H2>
  76
  77 <P>Once you have configured Kerberos on your system(s), you can then
  78 enable Kerberos authentication by selecting the <tt>Negotiate</tt>
  79 authentication type. The simplest way to do this is using the
  80 <tt>cupsctl(8)</tt> command:</P>
  81
  82 <PRE CLASS="command">
  83 <KBD>cupsctl DefaultAuthType=Negotiate</KBD>
  84 </PRE>
  85
  86 <P>You can also enable Kerberos from the web interface by checking the
  87 <VAR>Use Kerberos Authentication</VAR> box and clicking <VAR>Change
  88 Settings</VAR>:</P>
  89
  90 <PRE CLASS="command">
  91 http://localhost:631/admin
  92 </PRE>
  93
  94 <P>After you have enabled Kerberos authentication, use the built-in
  95 "authenticated" policy or your own custom policies with the printers you
  96 will be sharing. See <a href="policies.html">Managing Operation Policies</a>
  97 for more information.</P>
  98
  99
 100 <H2 CLASS="title"><A NAME="IMPLEMENT">Implementation Information</A></H2>
 101
 102 <P>CUPS implements Kerberos over HTTP using GSSAPI and the service name
 103 "ipp". Because of limitations in the HTTP GSSAPI protocol extension, only
 104 a single domain/KDC is supported for authentication.</P>
 105
 106 <P>When doing printing tasks that require authentication, CUPS requests a
 107 single-use "ticket" from your login session to authenticate who you are.
 108 This ticket gives CUPS a username of the form "user@REALM", which is then
 109 converted to just "user" for purposes of user and group checks.</P>
 110
 111 <P>In order to support printing to a shared printer, CUPS has to ask the KDC
 112 for a copy of your credentials (this is called delegation) that can be sent to
 113 the remote server for authenticatation. Delegation only works when the system
 114 has a stable hostname which maps to the current address of the system, which
 115 is why you need a static IP address or DHCP that updates the DNS entry for your
 116 system.</P>
 117
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