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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>UNIX Application Servers — MIT Kerberos Documentation</title> <link rel="stylesheet" href="../_static/agogo.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <link rel="stylesheet" href="../_static/kerb.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '1.15.1', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <link rel="author" title="About these documents" href="../about.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="top" title="MIT Kerberos Documentation" href="../index.html" /> <link rel="up" title="Installation guide" href="install.html" /> <link rel="next" title="Configuration Files" href="conf_files/index.html" /> <link rel="prev" title="Installing and configuring UNIX client machines" href="install_clients.html" /> </head> <body> <div class="header-wrapper"> <div class="header"> <h1><a href="../index.html">MIT Kerberos Documentation</a></h1> <div class="rel"> <a href="../index.html" title="Full Table of Contents" accesskey="C">Contents</a> | <a href="install_clients.html" title="Installing and configuring UNIX client machines" accesskey="P">previous</a> | <a href="conf_files/index.html" title="Configuration Files" accesskey="N">next</a> | <a href="../genindex.html" title="General Index" accesskey="I">index</a> | <a href="../search.html" title="Enter search criteria" accesskey="S">Search</a> | <a href="mailto:krb5-bugs@mit.edu?subject=Documentation__UNIX Application Servers">feedback</a> </div> </div> </div> <div class="content-wrapper"> <div class="content"> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="unix-application-servers"> <h1>UNIX Application Servers<a class="headerlink" href="#unix-application-servers" title="Permalink to this headline">¶</a></h1> <p>An application server is a host that provides one or more services over the network. Application servers can be “secure” or “insecure.” A “secure” host is set up to require authentication from every client connecting to it. An “insecure” host will still provide Kerberos authentication, but will also allow unauthenticated clients to connect.</p> <p>If you have Kerberos V5 installed on all of your client machines, MIT recommends that you make your hosts secure, to take advantage of the security that Kerberos authentication affords. However, if you have some clients that do not have Kerberos V5 installed, you can run an insecure server, and still take advantage of Kerberos V5’s single sign-on capability.</p> <div class="section" id="the-keytab-file"> <span id="keytab-file"></span><h2>The keytab file<a class="headerlink" href="#the-keytab-file" title="Permalink to this headline">¶</a></h2> <p>All Kerberos server machines need a keytab file to authenticate to the KDC. By default on UNIX-like systems this file is named <tt class="docutils literal"><span class="pre">FILE:/etc/krb5.keytab</span></tt>. The keytab file is an local copy of the host’s key. The keytab file is a potential point of entry for a break-in, and if compromised, would allow unrestricted access to its host. The keytab file should be readable only by root, and should exist only on the machine’s local disk. The file should not be part of any backup of the machine, unless access to the backup data is secured as tightly as access to the machine’s root password.</p> <p>In order to generate a keytab for a host, the host must have a principal in the Kerberos database. The procedure for adding hosts to the database is described fully in <a class="reference internal" href="database.html#add-mod-del-princs"><em>Adding, modifying and deleting principals</em></a>. (See <a class="reference internal" href="install_kdc.html#slave-host-key"><em>Create host keytabs for slave KDCs</em></a> for a brief description.) The keytab is generated by running <a class="reference internal" href="admin_commands/kadmin_local.html#kadmin-1"><em>kadmin</em></a> and issuing the <a class="reference internal" href="admin_commands/kadmin_local.html#ktadd"><em>ktadd</em></a> command.</p> <p>For example, to generate a keytab file to allow the host <tt class="docutils literal"><span class="pre">trillium.mit.edu</span></tt> to authenticate for the services host, ftp, and pop, the administrator <tt class="docutils literal"><span class="pre">joeadmin</span></tt> would issue the command (on <tt class="docutils literal"><span class="pre">trillium.mit.edu</span></tt>):</p> <div class="highlight-python"><pre>trillium% kadmin kadmin5: ktadd host/trillium.mit.edu ftp/trillium.mit.edu pop/trillium.mit.edu kadmin: Entry for principal host/trillium.mit.edu@ATHENA.MIT.EDU with kvno 3, encryption type DES-CBC-CRC added to keytab FILE:/etc/krb5.keytab. kadmin: Entry for principal ftp/trillium.mit.edu@ATHENA.MIT.EDU with kvno 3, encryption type DES-CBC-CRC added to keytab FILE:/etc/krb5.keytab. kadmin: Entry for principal pop/trillium.mit.edu@ATHENA.MIT.EDU with kvno 3, encryption type DES-CBC-CRC added to keytab FILE:/etc/krb5.keytab. kadmin5: quit trillium%</pre> </div> <p>If you generate the keytab file on another host, you need to get a copy of the keytab file onto the destination host (<tt class="docutils literal"><span class="pre">trillium</span></tt>, in the above example) without sending it unencrypted over the network.</p> </div> <div class="section" id="some-advice-about-secure-hosts"> <h2>Some advice about secure hosts<a class="headerlink" href="#some-advice-about-secure-hosts" title="Permalink to this headline">¶</a></h2> <p>Kerberos V5 can protect your host from certain types of break-ins, but it is possible to install Kerberos V5 and still leave your host vulnerable to attack. Obviously an installation guide is not the place to try to include an exhaustive list of countermeasures for every possible attack, but it is worth noting some of the larger holes and how to close them.</p> <p>We recommend that backups of secure machines exclude the keytab file (<tt class="docutils literal"><span class="pre">FILE:/etc/krb5.keytab</span></tt>). If this is not possible, the backups should at least be done locally, rather than over a network, and the backup tapes should be physically secured.</p> <p>The keytab file and any programs run by root, including the Kerberos V5 binaries, should be kept on local disk. The keytab file should be readable only by root.</p> </div> </div> </div> </div> </div> </div> <div class="sidebar"> <h2>On this page</h2> <ul> <li><a class="reference internal" href="#">UNIX Application Servers</a><ul> <li><a class="reference internal" href="#the-keytab-file">The keytab file</a></li> <li><a class="reference internal" href="#some-advice-about-secure-hosts">Some advice about secure hosts</a></li> </ul> </li> </ul> <br/> <h2>Table of contents</h2> <ul class="current"> <li class="toctree-l1"><a class="reference internal" href="../user/index.html">For users</a></li> <li class="toctree-l1 current"><a class="reference internal" href="index.html">For administrators</a><ul class="current"> <li class="toctree-l2 current"><a class="reference internal" href="install.html">Installation guide</a><ul class="current"> <li class="toctree-l3"><a class="reference internal" href="install_kdc.html">Installing KDCs</a></li> <li class="toctree-l3"><a class="reference internal" href="install_clients.html">Installing and configuring UNIX client machines</a></li> <li class="toctree-l3 current"><a class="current reference internal" href="">UNIX Application Servers</a></li> </ul> </li> <li class="toctree-l2"><a class="reference internal" href="conf_files/index.html">Configuration Files</a></li> <li class="toctree-l2"><a class="reference internal" href="realm_config.html">Realm configuration decisions</a></li> <li class="toctree-l2"><a class="reference internal" href="database.html">Database administration</a></li> <li class="toctree-l2"><a class="reference internal" href="lockout.html">Account lockout</a></li> <li class="toctree-l2"><a class="reference internal" href="conf_ldap.html">Configuring Kerberos with OpenLDAP back-end</a></li> <li class="toctree-l2"><a class="reference internal" href="appl_servers.html">Application servers</a></li> <li class="toctree-l2"><a class="reference internal" href="host_config.html">Host configuration</a></li> <li class="toctree-l2"><a class="reference internal" href="backup_host.html">Backups of secure hosts</a></li> <li class="toctree-l2"><a class="reference internal" href="pkinit.html">PKINIT configuration</a></li> <li class="toctree-l2"><a class="reference internal" href="otp.html">OTP Preauthentication</a></li> <li class="toctree-l2"><a class="reference internal" href="princ_dns.html">Principal names and DNS</a></li> <li class="toctree-l2"><a class="reference internal" href="enctypes.html">Encryption types</a></li> <li class="toctree-l2"><a class="reference internal" href="https.html">HTTPS proxy configuration</a></li> <li class="toctree-l2"><a class="reference internal" href="auth_indicator.html">Authentication indicators</a></li> <li class="toctree-l2"><a class="reference internal" href="admin_commands/index.html">Administration programs</a></li> <li class="toctree-l2"><a class="reference internal" href="../mitK5defaults.html">MIT Kerberos defaults</a></li> <li class="toctree-l2"><a class="reference internal" href="env_variables.html">Environment variables</a></li> <li class="toctree-l2"><a class="reference internal" href="troubleshoot.html">Troubleshooting</a></li> <li class="toctree-l2"><a class="reference internal" href="advanced/index.html">Advanced topics</a></li> <li class="toctree-l2"><a class="reference internal" href="various_envs.html">Various links</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="../appdev/index.html">For application developers</a></li> <li class="toctree-l1"><a class="reference internal" href="../plugindev/index.html">For plugin module developers</a></li> <li class="toctree-l1"><a class="reference internal" href="../build/index.html">Building Kerberos V5</a></li> <li class="toctree-l1"><a class="reference internal" href="../basic/index.html">Kerberos V5 concepts</a></li> <li class="toctree-l1"><a class="reference internal" href="../formats/index.html">Protocols and file formats</a></li> <li class="toctree-l1"><a class="reference internal" href="../mitK5features.html">MIT Kerberos features</a></li> <li class="toctree-l1"><a class="reference internal" href="../build_this.html">How to build this documentation from the source</a></li> <li class="toctree-l1"><a class="reference internal" href="../about.html">Contributing to the MIT Kerberos Documentation</a></li> <li class="toctree-l1"><a class="reference internal" href="../resources.html">Resources</a></li> </ul> <br/> <h4><a href="../index.html">Full Table of Contents</a></h4> <h4>Search</h4> <form class="search" action="../search.html" method="get"> <input type="text" name="q" size="18" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> <div class="clearer"></div> </div> </div> <div class="footer-wrapper"> <div class="footer" > <div class="right" ><i>Release: 1.15.1</i><br /> © <a 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