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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>KDC preauthentication interface (kdcpreauth) — 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 plugin module developers" href="index.html" /> <link rel="next" title="Credential cache selection interface (ccselect)" href="ccselect.html" /> <link rel="prev" title="Client preauthentication interface (clpreauth)" href="clpreauth.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="clpreauth.html" title="Client preauthentication interface (clpreauth)" accesskey="P">previous</a> | <a href="ccselect.html" title="Credential cache selection interface (ccselect)" 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__KDC preauthentication interface (kdcpreauth)">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="kdc-preauthentication-interface-kdcpreauth"> <h1>KDC preauthentication interface (kdcpreauth)<a class="headerlink" href="#kdc-preauthentication-interface-kdcpreauth" title="Permalink to this headline">¶</a></h1> <p>The kdcpreauth interface allows the addition of KDC support for preauthentication mechanisms beyond those included in the core MIT krb5 code base. For a detailed description of the kdcpreauth interface, see the header file <tt class="docutils literal"><span class="pre"><krb5/kdcpreauth_plugin.h></span></tt> (or <tt class="docutils literal"><span class="pre"><krb5/preauth_plugin.h></span></tt> before release 1.12).</p> <p>A kdcpreauth module is generally responsible for:</p> <ul class="simple"> <li>Supplying a list of preauth type numbers used by the module in the <strong>pa_type_list</strong> field of the vtable structure.</li> <li>Indicating what kind of preauthentication mechanism it implements, with the <strong>flags</strong> method. If the mechanism computes a new reply key, it must specify the <tt class="docutils literal"><span class="pre">PA_REPLACES_KEY</span></tt> flag. If the mechanism is generally only used with hardware tokens, the <tt class="docutils literal"><span class="pre">PA_HARDWARE</span></tt> flag allows the mechanism to work with principals which have the <strong>requires_hwauth</strong> flag set.</li> <li>Producing a padata value to be sent with a preauth_required error, with the <strong>edata</strong> method.</li> <li>Examining a padata value sent by a client and verifying that it proves knowledge of the appropriate client credential information. This is done with the <strong>verify</strong> method.</li> <li>Producing a padata response value for the client, and possibly computing a reply key. This is done with the <strong>return_padata</strong> method.</li> </ul> <p>A module can create and destroy per-KDC state objects by implementing the <strong>init</strong> and <strong>fini</strong> methods. Per-KDC state objects have the type krb5_kdcpreauth_moddata, which is an abstract pointer types. A module should typically cast this to an internal type for the state object.</p> <p>A module can create a per-request state object by returning one in the <strong>verify</strong> method, receiving it in the <strong>return_padata</strong> method, and destroying it in the <strong>free_modreq</strong> method. Note that these state objects only apply to the processing of a single AS request packet, not to an entire authentication exchange (since an authentication exchange may remain unfinished by the client or may involve multiple different KDC hosts). Per-request state objects have the type krb5_kdcpreauth_modreq, which is an abstract pointer type.</p> <p>The <strong>edata</strong>, <strong>verify</strong>, and <strong>return_padata</strong> methods have access to a callback function and handle (called a “rock”) which can be used to get additional information about the current request, including the maximum allowable clock skew, the client’s long-term keys, the DER-encoded request body, the FAST armor key, string attributes on the client’s database entry, and the client’s database entry itself. The <strong>verify</strong> method can assert one or more authentication indicators to be included in the issued ticket using the <tt class="docutils literal"><span class="pre">add_auth_indicator</span></tt> callback (new in release 1.14).</p> <p>A module can generate state information to be included with the next client request using the <tt class="docutils literal"><span class="pre">set_cookie</span></tt> callback (new in release 1.14). On the next request, the module can read this state information using the <tt class="docutils literal"><span class="pre">get_cookie</span></tt> callback. Cookie information is encrypted, timestamped, and transmitted to the client in a <tt class="docutils literal"><span class="pre">PA-FX-COOKIE</span></tt> pa-data item. Older clients may not support cookies and therefore may not transmit the cookie in the next request; in this case, <tt class="docutils literal"><span class="pre">get_cookie</span></tt> will not yield the saved information.</p> <p>If a module implements a mechanism which requires multiple round trips, its <strong>verify</strong> method can respond with the code <tt class="docutils literal"><span class="pre">KRB5KDC_ERR_MORE_PREAUTH_DATA_REQUIRED</span></tt> and a list of pa-data in the <em>e_data</em> parameter to be processed by the client.</p> <p>The <strong>edata</strong> and <strong>verify</strong> methods can be implemented asynchronously. Because of this, they do not return values directly to the caller, but must instead invoke responder functions with their results. A synchronous implementation can invoke the responder function immediately. An asynchronous implementation can use the callback to get an event context for use with the <a class="reference external" href="https://fedorahosted.org/libverto/">libverto</a> API.</p> </div> </div> </div> </div> </div> <div class="sidebar"> <h2>On this page</h2> <ul> <li><a class="reference internal" href="#">KDC preauthentication interface (kdcpreauth)</a></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"><a class="reference internal" href="../admin/index.html">For administrators</a></li> <li class="toctree-l1"><a class="reference internal" href="../appdev/index.html">For application developers</a></li> <li class="toctree-l1 current"><a class="reference internal" href="index.html">For plugin module developers</a><ul class="current"> <li class="toctree-l2"><a class="reference internal" href="general.html">General plugin concepts</a></li> <li class="toctree-l2"><a class="reference internal" href="clpreauth.html">Client preauthentication interface (clpreauth)</a></li> <li class="toctree-l2 current"><a class="current reference internal" href="">KDC preauthentication interface (kdcpreauth)</a></li> <li class="toctree-l2"><a class="reference internal" href="ccselect.html">Credential cache selection interface (ccselect)</a></li> <li class="toctree-l2"><a class="reference internal" href="pwqual.html">Password quality interface (pwqual)</a></li> <li class="toctree-l2"><a class="reference internal" href="kadm5_hook.html">KADM5 hook interface (kadm5_hook)</a></li> <li class="toctree-l2"><a class="reference internal" href="hostrealm.html">Host-to-realm interface (hostrealm)</a></li> <li class="toctree-l2"><a class="reference internal" href="localauth.html">Local authorization interface (localauth)</a></li> <li class="toctree-l2"><a class="reference internal" href="locate.html">Server location interface (locate)</a></li> <li class="toctree-l2"><a class="reference internal" href="profile.html">Configuration interface (profile)</a></li> <li class="toctree-l2"><a class="reference internal" href="gssapi.html">GSSAPI mechanism interface</a></li> <li class="toctree-l2"><a class="reference internal" href="internal.html">Internal pluggable interfaces</a></li> <li class="toctree-l2"><a class="reference internal" href="certauth.html">PKINIT certificate authorization interface (certauth)</a></li> <li class="toctree-l2"><a class="reference internal" href="kdcpolicy.html">KDC policy interface (kdcpolicy)</a></li> </ul> </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="clpreauth.html" title="Client preauthentication interface (clpreauth)" >previous</a> | <a href="ccselect.html" title="Credential cache selection interface (ccselect)" >next</a> | <a href="../genindex.html" title="General Index" >index</a> | <a href="../search.html" title="Enter search criteria" >Search</a> | <a href="mailto:krb5-bugs@mit.edu?subject=Documentation__KDC preauthentication interface (kdcpreauth)">feedback</a> </div> </div> </div> </body> </html>