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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>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="For administrators" href="index.html" /> <link rel="next" title="Host configuration" href="host_config.html" /> <link rel="prev" title="Configuring Kerberos with OpenLDAP back-end" href="conf_ldap.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="conf_ldap.html" title="Configuring Kerberos with OpenLDAP back-end" accesskey="P">previous</a> | <a href="host_config.html" title="Host configuration" 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__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="application-servers"> <h1>Application servers<a class="headerlink" href="#application-servers" title="Permalink to this headline">¶</a></h1> <p>If you need to install the Kerberos V5 programs on an application server, please refer to the Kerberos V5 Installation Guide. Once you have installed the software, you need to add that host to the Kerberos database (see <a class="reference internal" href="database.html#add-mod-del-princs"><em>Adding, modifying and deleting principals</em></a>), and generate a keytab for that host, that contains the host’s key. You also need to make sure the host’s clock is within your maximum clock skew of the KDCs.</p> <div class="section" id="keytabs"> <h2>Keytabs<a class="headerlink" href="#keytabs" title="Permalink to this headline">¶</a></h2> <p>A keytab is a host’s copy of its own keylist, which is analogous to a user’s password. An application server that needs to authenticate itself to the KDC has to have a keytab that contains its own principal and key. Just as it is important for users to protect their passwords, it is equally important for hosts to protect their keytabs. You should always store keytab files on local disk, and make them readable only by root, and you should never send a keytab file over a network in the clear. Ideally, you should run the <a class="reference internal" href="admin_commands/kadmin_local.html#kadmin-1"><em>kadmin</em></a> command to extract a keytab on the host on which the keytab is to reside.</p> <div class="section" id="adding-principals-to-keytabs"> <span id="add-princ-kt"></span><h3>Adding principals to keytabs<a class="headerlink" href="#adding-principals-to-keytabs" title="Permalink to this headline">¶</a></h3> <p>To generate a keytab, or to add a principal to an existing keytab, use the <strong>ktadd</strong> command from kadmin.</p> </div> <div class="section" id="ktadd"> <h3>ktadd<a class="headerlink" href="#ktadd" title="Permalink to this headline">¶</a></h3> <blockquote> <div><div class="line-block"> <div class="line"><strong>ktadd</strong> [options] <em>principal</em></div> <div class="line"><strong>ktadd</strong> [options] <strong>-glob</strong> <em>princ-exp</em></div> </div> </div></blockquote> <p>Adds a <em>principal</em>, or all principals matching <em>princ-exp</em>, to a keytab file. Each principal’s keys are randomized in the process. The rules for <em>princ-exp</em> are described in the <strong>list_principals</strong> command.</p> <p>This command requires the <strong>inquire</strong> and <strong>changepw</strong> privileges. With the <strong>-glob</strong> form, it also requires the <strong>list</strong> privilege.</p> <p>The options are:</p> <dl class="docutils"> <dt><strong>-k[eytab]</strong> <em>keytab</em></dt> <dd>Use <em>keytab</em> as the keytab file. Otherwise, the default keytab is used.</dd> <dt><strong>-e</strong> <em>enc</em>:<em>salt</em>,...</dt> <dd>Uses the specified keysalt list for setting the new keys of the principal. See <a class="reference internal" href="conf_files/kdc_conf.html#keysalt-lists"><em>Keysalt lists</em></a> in <a class="reference internal" href="conf_files/kdc_conf.html#kdc-conf-5"><em>kdc.conf</em></a> for a list of possible values.</dd> <dt><strong>-q</strong></dt> <dd>Display less verbose information.</dd> <dt><strong>-norandkey</strong></dt> <dd>Do not randomize the keys. The keys and their version numbers stay unchanged. This option cannot be specified in combination with the <strong>-e</strong> option.</dd> </dl> <p>An entry for each of the principal’s unique encryption types is added, ignoring multiple keys with the same encryption type but different salt types.</p> <p>Example:</p> <div class="highlight-python"><pre>kadmin: ktadd -k /tmp/foo-new-keytab host/foo.mit.edu Entry for principal host/foo.mit.edu@ATHENA.MIT.EDU with kvno 3, encryption type aes256-cts-hmac-sha1-96 added to keytab FILE:/tmp/foo-new-keytab kadmin:</pre> </div> <div class="section" id="examples"> <h4>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h4> <p>Here is a sample session, using configuration files that enable only AES encryption:</p> <div class="highlight-python"><pre>kadmin: ktadd host/daffodil.mit.edu@ATHENA.MIT.EDU Entry for principal host/daffodil.mit.edu with kvno 2, encryption type aes256-cts-hmac-sha1-96 added to keytab FILE:/etc/krb5.keytab Entry for principal host/daffodil.mit.edu with kvno 2, encryption type aes128-cts-hmac-sha1-96 added to keytab FILE:/etc/krb5.keytab kadmin:</pre> </div> </div> </div> <div class="section" id="removing-principals-from-keytabs"> <h3>Removing principals from keytabs<a class="headerlink" href="#removing-principals-from-keytabs" title="Permalink to this headline">¶</a></h3> <p>To remove a principal from an existing keytab, use the kadmin <strong>ktremove</strong> command.</p> </div> <div class="section" id="ktremove"> <h3>ktremove<a class="headerlink" href="#ktremove" title="Permalink to this headline">¶</a></h3> <blockquote> <div><strong>ktremove</strong> [options] <em>principal</em> [<em>kvno</em> | <em>all</em> | <em>old</em>]</div></blockquote> <p>Removes entries for the specified <em>principal</em> from a keytab. Requires no permissions, since this does not require database access.</p> <p>If the string “all” is specified, all entries for that principal are removed; if the string “old” is specified, all entries for that principal except those with the highest kvno are removed. Otherwise, the value specified is parsed as an integer, and all entries whose kvno match that integer are removed.</p> <p>The options are:</p> <dl class="docutils"> <dt><strong>-k[eytab]</strong> <em>keytab</em></dt> <dd>Use <em>keytab</em> as the keytab file. Otherwise, the default keytab is used.</dd> <dt><strong>-q</strong></dt> <dd>Display less verbose information.</dd> </dl> <p>Example:</p> <div class="highlight-python"><pre>kadmin: ktremove kadmin/admin all Entry for principal kadmin/admin with kvno 3 removed from keytab FILE:/etc/krb5.keytab kadmin:</pre> </div> </div> </div> <div class="section" id="clock-skew"> <h2>Clock Skew<a class="headerlink" href="#clock-skew" title="Permalink to this headline">¶</a></h2> <p>A Kerberos application server host must keep its clock synchronized or it will reject authentication requests from clients. Modern operating systems typically provide a facility to maintain the correct time; make sure it is enabled. This is especially important on virtual machines, where clocks tend to drift more rapidly than normal machine clocks.</p> <p>The default allowable clock skew is controlled by the <strong>clockskew</strong> variable in <a class="reference internal" href="conf_files/krb5_conf.html#libdefaults"><em>[libdefaults]</em></a>.</p> </div> <div class="section" id="getting-dns-information-correct"> <h2>Getting DNS information correct<a class="headerlink" href="#getting-dns-information-correct" title="Permalink to this headline">¶</a></h2> <p>Several aspects of Kerberos rely on name service. When a hostname is used to name a service, the Kerberos library canonicalizes the hostname using forward and reverse name resolution. (The reverse name resolution step can be turned off using the <strong>rdns</strong> variable in <a class="reference internal" href="conf_files/krb5_conf.html#libdefaults"><em>[libdefaults]</em></a>.) The result of this canonicalization must match the principal entry in the host’s keytab, or authentication will fail.</p> <p>Each host’s canonical name must be the fully-qualified host name (including the domain), and each host’s IP address must reverse-resolve to the canonical name.</p> <p>Configuration of hostnames varies by operating system. On the application server itself, canonicalization will typically use the <tt class="docutils literal"><span class="pre">/etc/hosts</span></tt> file rather than the DNS. Ensure that the line for the server’s hostname is in the following form:</p> <div class="highlight-python"><pre>IP address fully-qualified hostname aliases</pre> </div> <p>Here is a sample <tt class="docutils literal"><span class="pre">/etc/hosts</span></tt> file:</p> <div class="highlight-python"><pre># this is a comment 127.0.0.1 localhost localhost.mit.edu 10.0.0.6 daffodil.mit.edu daffodil trillium wake-robin</pre> </div> <p>The output of <tt class="docutils literal"><span class="pre">klist</span> <span class="pre">-k</span></tt> for this example host should look like:</p> <div class="highlight-python"><pre>viola# klist -k Keytab name: /etc/krb5.keytab KVNO Principal ---- ------------------------------------------------------------ 2 host/daffodil.mit.edu@ATHENA.MIT.EDU</pre> </div> <p>If you were to ssh to this host with a fresh credentials cache (ticket file), and then <a class="reference internal" href="../user/user_commands/klist.html#klist-1"><em>klist</em></a>, the output should list a service principal of <tt class="docutils literal"><span class="pre">host/daffodil.mit.edu@ATHENA.MIT.EDU</span></tt>.</p> </div> <div class="section" id="configuring-your-firewall-to-work-with-kerberos-v5"> <span id="conf-firewall"></span><h2>Configuring your firewall to work with Kerberos V5<a class="headerlink" href="#configuring-your-firewall-to-work-with-kerberos-v5" title="Permalink to this headline">¶</a></h2> <p>If you need off-site users to be able to get Kerberos tickets in your realm, they must be able to get to your KDC. This requires either that you have a slave KDC outside your firewall, or that you configure your firewall to allow UDP requests into at least one of your KDCs, on whichever port the KDC is running. (The default is port 88; other ports may be specified in the KDC’s <a class="reference internal" href="conf_files/kdc_conf.html#kdc-conf-5"><em>kdc.conf</em></a> file.) Similarly, if you need off-site users to be able to change their passwords in your realm, they must be able to get to your Kerberos admin server on the kpasswd port (which defaults to 464). If you need off-site users to be able to administer your Kerberos realm, they must be able to get to your Kerberos admin server on the administrative port (which defaults to 749).</p> <p>If your on-site users inside your firewall will need to get to KDCs in other realms, you will also need to configure your firewall to allow outgoing TCP and UDP requests to port 88, and to port 464 to allow password changes. If your on-site users inside your firewall will need to get to Kerberos admin servers in other realms, you will also need to allow outgoing TCP and UDP requests to port 749.</p> <p>If any of your KDCs are outside your firewall, you will need to allow kprop requests to get through to the remote KDC. <a class="reference internal" href="admin_commands/kprop.html#kprop-8"><em>kprop</em></a> uses the <tt class="docutils literal"><span class="pre">krb5_prop</span></tt> service on port 754 (tcp).</p> <p>The book <em>UNIX System Security</em>, by David Curry, is a good starting point for learning to configure firewalls.</p> </div> </div> </div> </div> </div> </div> <div class="sidebar"> <h2>On this page</h2> <ul> <li><a class="reference internal" href="#">Application servers</a><ul> <li><a class="reference internal" href="#keytabs">Keytabs</a><ul> <li><a class="reference internal" href="#adding-principals-to-keytabs">Adding principals to keytabs</a></li> <li><a class="reference internal" href="#ktadd">ktadd</a><ul> <li><a class="reference internal" href="#examples">Examples</a></li> </ul> </li> <li><a class="reference internal" href="#removing-principals-from-keytabs">Removing principals from keytabs</a></li> <li><a class="reference internal" href="#ktremove">ktremove</a></li> </ul> </li> <li><a class="reference internal" href="#clock-skew">Clock Skew</a></li> <li><a class="reference internal" href="#getting-dns-information-correct">Getting DNS information correct</a></li> <li><a class="reference internal" href="#configuring-your-firewall-to-work-with-kerberos-v5">Configuring your firewall to work with Kerberos V5</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"><a class="reference internal" href="install.html">Installation guide</a></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 current"><a class="current reference internal" href="">Application servers</a><ul class="simple"> </ul> </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 href="../copyright.html">Copyright</a> 1985-2017, MIT. </div> <div class="left"> <a href="../index.html" title="Full Table of Contents" >Contents</a> | <a href="conf_ldap.html" 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