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<section id="configuring-kerberos-with-openldap-back-end">
<span id="conf-ldap"></span><h1>Configuring Kerberos with OpenLDAP back-end<a class="headerlink" href="#configuring-kerberos-with-openldap-back-end" title="Link to this heading">ΒΆ</a></h1>
<blockquote>
<div><ol class="arabic">
<li><p>Make sure the LDAP server is using local authentication
(<code class="docutils literal notranslate"><span class="pre">ldapi://</span></code>) or TLS (<code class="docutils literal notranslate"><span class="pre">ldaps</span></code>). See
<a class="reference external" href="https://www.openldap.org/doc/admin/tls.html">https://www.openldap.org/doc/admin/tls.html</a> for instructions on
configuring TLS support in OpenLDAP.</p></li>
<li><p>Add the Kerberos schema file to the LDAP Server using the OpenLDAP
LDIF file from the krb5 source directory
(<code class="docutils literal notranslate"><span class="pre">src/plugins/kdb/ldap/libkdb_ldap/kerberos.openldap.ldif</span></code>).
The following example uses local authentication:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ldapadd</span> <span class="o">-</span><span class="n">Y</span> <span class="n">EXTERNAL</span> <span class="o">-</span><span class="n">H</span> <span class="n">ldapi</span><span class="p">:</span><span class="o">///</span> <span class="o">-</span><span class="n">f</span> <span class="o">/</span><span class="n">path</span><span class="o">/</span><span class="n">to</span><span class="o">/</span><span class="n">kerberos</span><span class="o">.</span><span class="n">openldap</span><span class="o">.</span><span class="n">ldif</span>
</pre></div>
</div>
</li>
<li><p>Choose DNs for the <a class="reference internal" href="admin_commands/krb5kdc.html#krb5kdc-8"><span class="std std-ref">krb5kdc</span></a> and <a class="reference internal" href="admin_commands/kadmind.html#kadmind-8"><span class="std std-ref">kadmind</span></a> servers
to bind to the LDAP server, and create them if necessary. Specify
these DNs with the <strong>ldap_kdc_dn</strong> and <strong>ldap_kadmind_dn</strong>
directives in <a class="reference internal" href="conf_files/kdc_conf.html#kdc-conf-5"><span class="std std-ref">kdc.conf</span></a>. The kadmind DN will also be
used for administrative commands such as <a class="reference internal" href="admin_commands/kdb5_util.html#kdb5-util-8"><span class="std std-ref">kdb5_util</span></a>.</p>
<p>Alternatively, you may configure krb5kdc and kadmind to use SASL
authentication to access the LDAP server; see the <a class="reference internal" href="conf_files/kdc_conf.html#dbmodules"><span class="std std-ref">[dbmodules]</span></a>
relations <strong>ldap_kdc_sasl_mech</strong> and similar.</p>
</li>
<li><p>Specify a location for the LDAP service password file by setting
<strong>ldap_service_password_file</strong>. Use <code class="docutils literal notranslate"><span class="pre">kdb5_ldap_util</span> <span class="pre">stashsrvpw</span></code>
to stash passwords for the KDC and kadmind DNs chosen above. For
example:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">kdb5_ldap_util</span> <span class="n">stashsrvpw</span> <span class="o">-</span><span class="n">f</span> <span class="o">/</span><span class="n">path</span><span class="o">/</span><span class="n">to</span><span class="o">/</span><span class="n">service</span><span class="o">.</span><span class="n">keyfile</span> <span class="n">cn</span><span class="o">=</span><span class="n">krbadmin</span><span class="p">,</span><span class="n">dc</span><span class="o">=</span><span class="n">example</span><span class="p">,</span><span class="n">dc</span><span class="o">=</span><span class="n">com</span>
</pre></div>
</div>
<p>Skip this step if you are using SASL authentication and the
mechanism does not require a password.</p>
</li>
<li><p>Choose a DN for the global Kerberos container entry (but do not
create the entry at this time). Specify this DN with the
<strong>ldap_kerberos_container_dn</strong> directive in <a class="reference internal" href="conf_files/kdc_conf.html#kdc-conf-5"><span class="std std-ref">kdc.conf</span></a>.
Realm container entries will be created underneath this DN.
Principal entries may exist either underneath the realm container
(the default) or in separate trees referenced from the realm
container.</p></li>
<li><p>Configure the LDAP server ACLs to enable the KDC and kadmin server
DNs to read and write the Kerberos data. If
<strong>disable_last_success</strong> and <strong>disable_lockout</strong> are both set to
true in the <a class="reference internal" href="conf_files/kdc_conf.html#dbmodules"><span class="std std-ref">[dbmodules]</span></a> subsection for the realm, then the
KDC DN only requires read access to the Kerberos data.</p>
<p>Sample access control information:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">access</span> <span class="n">to</span> <span class="n">dn</span><span class="o">.</span><span class="n">base</span><span class="o">=</span><span class="s2">""</span>
<span class="n">by</span> <span class="o">*</span> <span class="n">read</span>
<span class="n">access</span> <span class="n">to</span> <span class="n">dn</span><span class="o">.</span><span class="n">base</span><span class="o">=</span><span class="s2">"cn=Subschema"</span>
<span class="n">by</span> <span class="o">*</span> <span class="n">read</span>
<span class="c1"># Provide access to the realm container.</span>
<span class="n">access</span> <span class="n">to</span> <span class="n">dn</span><span class="o">.</span><span class="n">subtree</span><span class="o">=</span> <span class="s2">"cn=EXAMPLE.COM,cn=krbcontainer,dc=example,dc=com"</span>
<span class="n">by</span> <span class="n">dn</span><span class="o">.</span><span class="n">exact</span><span class="o">=</span><span class="s2">"cn=kdc-service,dc=example,dc=com"</span> <span class="n">write</span>
<span class="n">by</span> <span class="n">dn</span><span class="o">.</span><span class="n">exact</span><span class="o">=</span><span class="s2">"cn=adm-service,dc=example,dc=com"</span> <span class="n">write</span>
<span class="n">by</span> <span class="o">*</span> <span class="n">none</span>
<span class="c1"># Provide access to principals, if not underneath the realm container.</span>
<span class="n">access</span> <span class="n">to</span> <span class="n">dn</span><span class="o">.</span><span class="n">subtree</span><span class="o">=</span> <span class="s2">"ou=users,dc=example,dc=com"</span>
<span class="n">by</span> <span class="n">dn</span><span class="o">.</span><span class="n">exact</span><span class="o">=</span><span class="s2">"cn=kdc-service,dc=example,dc=com"</span> <span class="n">write</span>
<span class="n">by</span> <span class="n">dn</span><span class="o">.</span><span class="n">exact</span><span class="o">=</span><span class="s2">"cn=adm-service,dc=example,dc=com"</span> <span class="n">write</span>
<span class="n">by</span> <span class="o">*</span> <span class="n">none</span>
<span class="n">access</span> <span class="n">to</span> <span class="o">*</span>
<span class="n">by</span> <span class="o">*</span> <span class="n">read</span>
</pre></div>
</div>
<p>If the locations of the container and principals or the DNs of the
service objects for a realm are changed then this information
should be updated.</p>
</li>
<li><p>In <a class="reference internal" href="conf_files/kdc_conf.html#kdc-conf-5"><span class="std std-ref">kdc.conf</span></a>, make sure the following relations are set
in the <a class="reference internal" href="conf_files/kdc_conf.html#dbmodules"><span class="std std-ref">[dbmodules]</span></a> subsection for the realm:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>db_library (set to ``kldap``)
ldap_kerberos_container_dn
ldap_kdc_dn
ldap_kadmind_dn
ldap_service_password_file
ldap_servers
</pre></div>
</div>
</li>
<li><p>Create the realm using <a class="reference internal" href="admin_commands/kdb5_ldap_util.html#kdb5-ldap-util-8"><span class="std std-ref">kdb5_ldap_util</span></a>:</p>
<blockquote>
<div><p>kdb5_ldap_util create -subtrees ou=users,dc=example,dc=com -s</p>
</div></blockquote>
<p>Use the <strong>-subtrees</strong> option if the principals are to exist in a
separate subtree from the realm container. Before executing the
command, make sure that the subtree mentioned above
<code class="docutils literal notranslate"><span class="pre">(ou=users,dc=example,dc=com)</span></code> exists. If the principals will
exist underneath the realm container, omit the <strong>-subtrees</strong> option
and do not worry about creating the principal subtree.</p>
<p>For more information, refer to the section <a class="reference internal" href="database.html#ops-on-ldap"><span class="std std-ref">Operations on the LDAP database</span></a>.</p>
<p>The realm object is created under the
<strong>ldap_kerberos_container_dn</strong> specified in the configuration
file. This operation will also create the Kerberos container, if
not present already. This container can be used to store
information related to multiple realms.</p>
</li>
<li><p>Add an <code class="docutils literal notranslate"><span class="pre">eq</span></code> index for <code class="docutils literal notranslate"><span class="pre">krbPrincipalName</span></code> to speed up principal
lookup operations. See
<a class="reference external" href="https://www.openldap.org/doc/admin/tuning.html#Indexes">https://www.openldap.org/doc/admin/tuning.html#Indexes</a> for
details.</p></li>
</ol>
</div></blockquote>
<p>With the LDAP back end it is possible to provide aliases for principal
entries. Beginning in release 1.22, aliases can be added with the
kadmin <strong>add_alias</strong> command, but it is also possible (in release 1.7
or later) to provide aliases through direct manipulation of the LDAP
entries.</p>
<p>An entry with aliases contains multiple values of the
<em>krbPrincipalName</em> attribute. Since LDAP attribute values are not
ordered, it is necessary to specify which principal name is canonical,
by using the <em>krbCanonicalName</em> attribute. Therefore, to create
aliases for an entry, first set the <em>krbCanonicalName</em> attribute of
the entry to the canonical principal name (which should be identical
to the pre-existing <em>krbPrincipalName</em> value), and then add additional
<em>krbPrincipalName</em> attributes for the aliases.</p>
<p>Principal aliases are only returned by the KDC when the client
requests canonicalization. Canonicalization is normally requested for
service principals; for client principals, an explicit flag is often
required (e.g., <code class="docutils literal notranslate"><span class="pre">kinit</span> <span class="pre">-C</span></code>) and canonicalization is only performed
for initial ticket requests.</p>
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