path: root/docs/manual/mod/mod_ldap.xml

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<modulesynopsis metafile="mod_ldap.xml.meta">

<name>mod_ldap</name>
<description>LDAP connection pooling and result caching services for use
by other LDAP modules</description>
<status>Extension</status>
<sourcefile>util_ldap.c</sourcefile>
<identifier>ldap_module</identifier>
<compatibility>Available in version 2.0.41 and later</compatibility>

<summary>
    <p>This module was created to improve the performance of
    websites relying on backend connections to LDAP servers. In
    addition to the functions provided by the standard LDAP
    libraries, this module adds an LDAP connection pool and an LDAP
    shared memory cache.</p>

    <p>To enable this module, LDAP support must be compiled into
    apr-util. This is achieved by adding the <code>--with-ldap</code>
    flag to the <program>configure</program> script when building
    Apache.</p>

    <p>SSL/TLS support is dependant on which LDAP toolkit has been
    linked to <glossary>APR</glossary>. As of this writing, APR-util supports:
    <a href="http://www.openldap.org/">OpenLDAP SDK</a> (2.x or later),
    <a href="http://developer.novell.com/ndk/cldap.htm">Novell LDAP
    SDK</a>, <a href="http://www.mozilla.org/directory/csdk.html">
    Mozilla LDAP SDK</a>, native Solaris LDAP SDK (Mozilla based),
    native Microsoft LDAP SDK, or the
    <a href="http://www.iplanet.com/downloads/developer/">iPlanet
    (Netscape)</a> SDK. See the <a href="http://apr.apache.org">APR</a>
    website for details.</p>

</summary>

<section id="exampleconfig"><title>Example Configuration</title>
    <p>The following is an example configuration that uses
    <module>mod_ldap</module> to increase the performance of HTTP Basic
    authentication provided by <module>mod_authnz_ldap</module>.</p>

    <example>
      # Enable the LDAP connection pool and shared<br />
      # memory cache. Enable the LDAP cache status<br />
      # handler. Requires that mod_ldap and mod_authnz_ldap<br />
      # be loaded. Change the "yourdomain.example.com" to<br />
      # match your domain.<br />
      <br />
      LDAPSharedCacheSize 200000<br />
      LDAPCacheEntries 1024<br />
      LDAPCacheTTL 600<br />
      LDAPOpCacheEntries 1024<br />
      LDAPOpCacheTTL 600<br />
      <br />
      &lt;Location /ldap-status&gt;<br />
      <indent>
        SetHandler ldap-status<br />
        Order deny,allow<br />
        Deny from all<br />
        Allow from yourdomain.example.com<br />
        AuthLDAPEnabled on<br />
        AuthLDAPURL ldap://127.0.0.1/dc=example,dc=com?uid?one<br />
        AuthLDAPAuthoritative on<br />
        require valid-user<br />
      </indent>
      &lt;/Location&gt;
    </example>
</section>

<section id="pool"><title>LDAP Connection Pool</title>

    <p>LDAP connections are pooled from request to request. This
    allows the LDAP server to remain connected and bound ready for
    the next request, without the need to unbind/connect/rebind.
    The performance advantages are similar to the effect of HTTP
    keepalives.</p>

    <p>On a busy server it is possible that many requests will try
    and access the same LDAP server connection simultaneously.
    Where an LDAP connection is in use, Apache will create a new
    connection alongside the original one. This ensures that the
    connection pool does not become a bottleneck.</p>

    <p>There is no need to manually enable connection pooling in
    the Apache configuration. Any module using this module for
    access to LDAP services will share the connection pool.</p>
</section>

<section id="cache"><title>LDAP Cache</title>

    <p>For improved performance, <module>mod_ldap</module> uses an aggressive
    caching strategy to minimize the number of times that the LDAP
    server must be contacted. Caching can easily double or triple
    the throughput of Apache when it is serving pages protected
    with mod_authnz_ldap. In addition, the load on the LDAP server
    will be significantly decreased.</p>

    <p><module>mod_ldap</module> supports two types of LDAP caching during
    the search/bind phase with a <em>search/bind cache</em> and
    during the compare phase with two <em>operation
    caches</em>. Each LDAP URL that is used by the server has
    its own set of these three caches.</p>

    <section id="search-bind"><title>The Search/Bind Cache</title>
      <p>The process of doing a search and then a bind is the
      most time-consuming aspect of LDAP operation, especially if
      the directory is large. The search/bind cache is used to
      cache all searches that resulted in successful binds.
      Negative results (<em>i.e.</em>, unsuccessful searches, or searches
      that did not result in a successful bind) are not cached.
      The rationale behind this decision is that connections with
      invalid credentials are only a tiny percentage of the total
      number of connections, so by not caching invalid
      credentials, the size of the cache is reduced.</p>

      <p><module>mod_ldap</module> stores the username, the DN
      retrieved, the password used to bind, and the time of the bind
      in the cache. Whenever a new connection is initiated with the
      same username, <module>mod_ldap</module> compares the password
      of the new connection with the password in the cache. If the
      passwords match, and if the cached entry is not too old,
      <module>mod_ldap</module> bypasses the search/bind phase.</p>

      <p>The search and bind cache is controlled with the <directive
      module="mod_ldap">LDAPCacheEntries</directive> and <directive
      module="mod_ldap">LDAPCacheTTL</directive> directives.</p>
    </section>

    <section id="opcaches"><title>Operation Caches</title>
      <p>During attribute and distinguished name comparison
      functions, <module>mod_ldap</module> uses two operation caches
      to cache the compare operations. The first compare cache is
      used to cache the results of compares done to test for LDAP
      group membership. The second compare cache is used to cache
      the results of comparisons done between distinguished
      names.</p>

      <p>The behavior of both of these caches is controlled with
      the <directive module="mod_ldap">LDAPOpCacheEntries</directive>
      and <directive module="mod_ldap">LDAPOpCacheTTL</directive>
      directives.</p>
    </section>

    <section id="monitoring"><title>Monitoring the Cache</title>
      <p><module>mod_ldap</module> has a content handler that allows
      administrators to monitor the cache performance. The name of
      the content handler is <code>ldap-status</code>, so the
      following directives could be used to access the
      <module>mod_ldap</module> cache information:</p>

      <example>
        &lt;Location /server/cache-info&gt;<br />
        <indent>
          SetHandler ldap-status<br />
        </indent>
        &lt;/Location&gt;
      </example>

      <p>By fetching the URL <code>http://servername/cache-info</code>,
      the administrator can get a status report of every cache that is used
      by <module>mod_ldap</module> cache. Note that if Apache does not
      support shared memory, then each <program>httpd</program> instance has its
      own cache, so reloading the URL will result in different
      information each time, depending on which <program>httpd</program>
      instance processes the request.</p>
    </section>
</section>

<section id="usingssltls"><title>Using SSL/TLS</title>

    <p>The ability to create an SSL and TLS connections to an LDAP server 
    is defined by the directives <directive module="mod_ldap">
    LDAPTrustedGlobalCert</directive>, <directive module="mod_ldap">
    LDAPTrustedClientCert</directive> and <directive module="mod_ldap">
    LDAPTrustedMode</directive>. These directives specify the CA and
    optional client certificates to be used, as well as the type of
    encryption to be used on the connection (none, SSL or TLS/STARTTLS).</p>

    <example>
      # Establish an SSL LDAP connection on port 636. Requires that <br />
      # mod_ldap and mod_authnz_ldap be loaded. Change the <br />
      # "yourdomain.example.com" to match your domain.<br />
      <br />
      LDAPTrustedGlobalCert CA_DER /certs/certfile.der<br />
      <br />
      &lt;Location /ldap-status&gt;<br />
      <indent>
        SetHandler ldap-status<br />
        Order deny,allow<br />
        Deny from all<br />
        Allow from yourdomain.example.com<br />
        AuthLDAPEnabled on<br />
        AuthLDAPURL ldaps://127.0.0.1/dc=example,dc=com?uid?one<br />
        AuthLDAPAuthoritative on<br />
        require valid-user<br />
      </indent>
      &lt;/Location&gt;
    </example>

    <example>
      # Establish a TLS LDAP connection on port 389. Requires that <br />
      # mod_ldap and mod_authnz_ldap be loaded. Change the <br />
      # "yourdomain.example.com" to match your domain.<br />
      <br />
      LDAPTrustedGlobalCert CA_DER /certs/certfile.der<br />
      <br />
      &lt;Location /ldap-status&gt;<br />
      <indent>
        SetHandler ldap-status<br />
        Order deny,allow<br />
        Deny from all<br />
        Allow from yourdomain.example.com<br />
        AuthLDAPEnabled on<br />
        LDAPTrustedMode TLS
        AuthLDAPURL ldap://127.0.0.1/dc=example,dc=com?uid?one<br />
        AuthLDAPAuthoritative on<br />
        require valid-user<br />
      </indent>
      &lt;/Location&gt;
    </example>

</section>

<section id="settingcerts"><title>SSL/TLS Certificates</title>

    <p>The different LDAP SDKs have widely different methods of setting
    and handling both CA and client side certificates.</p>

    <p>If you intend to use SSL or TLS, read this section CAREFULLY so as to
    understand the differences between configurations on the different LDAP
    toolkits supported.</p>

    <section id="settingcerts-netscape"><title>Netscape/Mozilla/iPlanet SDK</title>
        <p>CA certificates are specified within a file called cert7.db.
        The SDK will not talk to any LDAP server whose certificate was
        not signed by a CA specified in this file. If
        client certificates are required, an optional key3.db file may
        be specified with an optional password. The secmod file can be
        specified if required. These files are in the same format as
        used by the Netscape Communicator or Mozilla web browsers. The easiest
        way to obtain these files is to grab them from your browser
        installation.</p>

        <p>Client certificates are specified per connection using the
        LDAPTrustedClientCert directive by referring
        to the certificate "nickname". An optional password may be
        specified to unlock the certificate's private key.</p>

        <p>The SDK supports SSL only. An attempt to use STARTTLS will cause
        an error when an attempt is made to contact the LDAP server at
        runtime.</p>

        <example>
            # Specify a Netscape CA certificate file<br />
            LDAPTrustedGlobalCert CA_CERT7_DB /certs/cert7.db<br />
            # Specify an optional key3.db file for client certificate support<br />
            LDAPTrustedGlobalCert CERT_KEY3_DB /certs/key3.db<br />
            # Specify the secmod file if required<br />
            LDAPTrustedGlobalCert CA_SECMOD /certs/secmod<br />
            &lt;Location /ldap-status&gt;<br />
            <indent>
                SetHandler ldap-status<br />
                Order deny,allow<br />
                Deny from all<br />
                Allow from yourdomain.example.com<br />
                AuthLDAPEnabled on<br />
                LDAPTrustedClientCert CERT_NICKNAME &lt;nickname&gt; [password]<br />
                AuthLDAPURL ldaps://127.0.0.1/dc=example,dc=com?uid?one<br />
                AuthLDAPAuthoritative on<br />
                require valid-user<br />
            </indent>
            &lt;/Location&gt;
        </example>

    </section>

    <section id="settingcerts-novell"><title>Novell SDK</title>

        <p>One or more CA certificates must be specified for the Novell
        SDK to work correctly. These certificates can be specified as
        binary DER or Base64 (PEM) encoded files.</p>

        <p>Note: Client certificates are specified globally rather than per
        connection, and so must be specified with the LDAPTrustedGlobalCert
        directive as below. Trying to set client certificates via the
        LDAPTrustedClientCert directive will cause an error to be logged
        when an attempt is made to connect to the LDAP server..</p>

        <p>The SDK supports both SSL and STARTTLS, set using the
        LDAPTrustedMode parameter. If an ldaps:// URL is specified,
        SSL mode is forced, override this directive.</p>

        <example>
             # Specify two CA certificate files<br />
             LDAPTrustedGlobalCert CA_DER /certs/cacert1.der<br />
             LDAPTrustedGlobalCert CA_BASE64 /certs/cacert2.pem<br />
             # Specify a client certificate file and key<br />
             LDAPTrustedGlobalCert CERT_BASE64 /certs/cert1.pem<br />
             LDAPTrustedGlobalCert KEY_BASE64 /certs/key1.pem [password]<br />
             # Do not use this directive, as it will throw an error<br />
             #LDAPTrustedClientCert CERT_BASE64 /certs/cert1.pem<br />
        </example>

    </section>

    <section id="settingcerts-openldap"><title>OpenLDAP SDK</title>

        <p>One or more CA certificates must be specified for the OpenLDAP
        SDK to work correctly. These certificates can be specified as
        binary DER or Base64 (PEM) encoded files.</p>

        <p>Client certificates are specified per connection using the
        LDAPTrustedClientCert directive.</p>

        <p>The documentation for the SDK claims to support both SSL and
        STARTTLS, however STARTTLS does not seem to work on all versions
        of the SDK. The SSL/TLS mode can be set using the
        LDAPTrustedMode parameter. If an ldaps:// URL is specified,
        SSL mode is forced. The OpenLDAP documentation notes that SSL
        (ldaps://) support has been deprecated to be replaced with TLS,
        although the SSL functionality still works.</p>

        <example>
             # Specify two CA certificate files<br />
             LDAPTrustedGlobalCert CA_DER /certs/cacert1.der<br />
             LDAPTrustedGlobalCert CA_BASE64 /certs/cacert2.pem<br />
            &lt;Location /ldap-status&gt;<br />
            <indent>
                SetHandler ldap-status<br />
                Order deny,allow<br />
                Deny from all<br />
                Allow from yourdomain.example.com<br />
                AuthLDAPEnabled on<br />
                LDAPTrustedClientCert CERT_BASE64 /certs/cert1.pem<br />
                LDAPTrustedClientCert KEY_BASE64 /certs/key1.pem<br />
                AuthLDAPURL ldaps://127.0.0.1/dc=example,dc=com?uid?one<br />
                AuthLDAPAuthoritative on<br />
                require valid-user<br />
            </indent>
            &lt;/Location&gt;
        </example>

    </section>

    <section id="settingcerts-solaris"><title>Solaris SDK</title>

        <p>SSL/TLS for the native Solaris LDAP libraries is not yet
        supported. If required, install and use the OpenLDAP libraries
        instead.</p>

    </section>

    <section id="settingcerts-microsoft"><title>Microsoft SDK</title>

        <p>SSL/TLS certificate configuration for the native Microsoft
        LDAP libraries is done inside the system registry, and no
        configuration directives are required.</p>

        <p>Both SSL and TLS are supported by using the ldaps:// URL
        format, or by using the LDAPTrustedMode directive accordingly.</p>

        <p>Note: The status of support for client certificates is not yet known
        for this toolkit.</p>

    </section>

</section>

<directivesynopsis>
<name>LDAPSharedCacheSize</name>
<description>Size in bytes of the shared-memory cache</description>
<syntax>LDAPSharedCacheSize <var>bytes</var></syntax>
<default>LDAPSharedCacheSize 102400</default>
<contextlist><context>server config</context></contextlist>

<usage>
    <p>Specifies the number of bytes to allocate for the shared
    memory cache. The default is 100kb. If set to 0, shared memory
    caching will not be used.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPSharedCacheFile</name>
<description>Sets the shared memory cache file</description>
<syntax>LDAPSharedCacheFile <var>directory-path/filename</var></syntax>
<contextlist><context>server config</context></contextlist>

<usage>
    <p>Specifies the directory path and file name of the shared memory
    cache file. If not set, anonymous shared memory will be used if the
    platform supports it.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPCacheEntries</name>
<description>Maximum number of entries in the primary LDAP cache</description>
<syntax>LDAPCacheEntries <var>number</var></syntax>
<default>LDAPCacheEntries 1024</default>
<contextlist><context>server config</context></contextlist>

<usage>
    <p>Specifies the maximum size of the primary LDAP cache. This
    cache contains successful search/binds. Set it to 0 to turn off
    search/bind caching. The default size is 1024 cached
    searches.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPCacheTTL</name>
<description>Time that cached items remain valid</description>
<syntax>LDAPCacheTTL <var>seconds</var></syntax>
<default>LDAPCacheTTL 600</default>
<contextlist><context>server config</context></contextlist>

<usage>
    <p>Specifies the time (in seconds) that an item in the
    search/bind cache remains valid. The default is 600 seconds (10
    minutes).</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPOpCacheEntries</name>
<description>Number of entries used to cache LDAP compare 
operations</description>
<syntax>LDAPOpCacheEntries <var>number</var></syntax>
<default>LDAPOpCacheEntries 1024</default>
<contextlist><context>server config</context></contextlist>

<usage>
    <p>This specifies the number of entries <module>mod_ldap</module>
    will use to cache LDAP compare operations. The default is 1024
    entries.  Setting it to 0 disables operation caching.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPOpCacheTTL</name>
<description>Time that entries in the operation cache remain
valid</description>
<syntax>LDAPOpCacheTTL <var>seconds</var></syntax>
<default>LDAPOpCacheTTL 600</default>
<contextlist><context>server config</context></contextlist>

<usage>
    <p>Specifies the time (in seconds) that entries in the
    operation cache remain valid. The default is 600 seconds.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPTrustedGlobalCert</name>
<description>Sets the file or database containing global trusted
Certificate Authority or global client certificates</description>
<syntax>LDAPTrustedGlobalCert <var>type</var> <var>directory-path/filename</var> <var>[password]</var></syntax>
<contextlist><context>server config</context></contextlist>

<usage>
    <p>It specifies the directory path and file name of the trusted CA
    certificates and/or system wide client certificates <module>mod_ldap</module>
    should use when establishing an SSL or TLS connection to an LDAP
    server. Note that all certificate information specified using this directive
    is applied globally to the entire server installation. Some LDAP toolkits
    (notably Novell) require all client certificates to be set globally using
    this directive. Most other toolkits require clients certificates to be set
    per Directory or per Location using LDAPTrustedClientCert. If you get this
    wrong, an error may be logged when an attempt is made to contact the LDAP
    server, or the connection may silently fail (See the SSL/TLS certificate
    guide above for details).
    The type specifies the kind of certificate parameter being
    set, depending on the LDAP toolkit being used. Supported types are:</p>
    <ul>
      <li>CA_DER - binary DER encoded CA certificate</li>
      <li>CA_BASE64 - PEM encoded CA certificate</li>
      <li>CA_CERT7_DB - Netscape cert7.db CA certificate database file</li>
      <li>CA_SECMOD - Netscape secmod database file</li>
      <li>CERT_DER - binary DER encoded client certificate</li>
      <li>CERT_BASE64 - PEM encoded client certificate</li>
      <li>CERT_KEY3_DB - Netscape key3.db client certificate database file</li>
      <li>CERT_NICKNAME - Client certificate "nickname" (Netscape SDK)</li>
      <li>CERT_PFX - PKCS#12 encoded client certificate (Novell SDK)</li>
      <li>KEY_DER - binary DER encoded private key</li>
      <li>KEY_BASE64 - PEM encoded private key</li>
      <li>KEY_PFX - PKCS#12 encoded private key (Novell SDK)</li>
    </ul>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPTrustedClientCert</name>
<description>Sets the file containing or nickname referring to a per
connection client certificate. Not all LDAP toolkits support per
connection client certificates.</description>
<syntax>LDAPTrustedClientCert <var>type</var> <var>directory-path/filename/nickname</var> <var>[password]</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>

<usage>
    <p>It specifies the directory path, file name or nickname of a
    per connection client certificate used when establishing an SSL
    or TLS connection to an LDAP server. Different locations or
    directories may have their own independant client certificate
    settings. Some LDAP toolkits (notably Novell)
    do not support per connection client certificates, and will throw an
    error on LDAP server connection if you try to use this directive
    (Use the LDAPTrustedGlobalCert directive instead for Novell client
    certificates - See the SSL/TLS certificate guide above for details).
    The type specifies the kind of certificate parameter being
    set, depending on the LDAP toolkit being used. Supported types are:</p>
    <ul>
      <li>CERT_DER - binary DER encoded client certificate</li>
      <li>CERT_BASE64 - PEM encoded client certificate</li>
      <li>CERT_NICKNAME - Client certificate "nickname" (Netscape SDK)</li>
      <li>KEY_DER - binary DER encoded private key</li>
      <li>KEY_BASE64 - PEM encoded private key</li>
    </ul>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPTrustedMode</name>
<description>Specifies the SSL/TLS mode to be used when connecting to an LDAP server.</description>
<syntax>LDAPTrustedMode <var>type</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>

<usage>
    <p>The following modes are supported:</p>
    <ul>
      <li>NONE - no encryption</li>
      <li>SSL - ldaps:// encryption on default port 636</li>
      <li>TLS - STARTTLS encryption on default port 389</li>
    </ul>

    <p>Not all LDAP toolkits support all the above modes. An error message
    will be logged at runtime if a mode is not supported, and the
    connection to the LDAP server will fail.
    </p>

    <p>If an ldaps:// URL is specified, the mode becomes SSL and the setting
    of LDAPTrustedMode is ignored.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPConnectionTimeout</name>
<description>Specifies the socket connection timeout in seconds</description>
<syntax>LDAPConnectionTimeout <var>seconds</var></syntax>
<contextlist><context>server config</context></contextlist>

<usage>
    <p>Specifies the timeout value (in seconds) in which the module will
    attempt to connect to the LDAP server.  If a connection is not
    successful with the timeout period, either an error will be 
    returned or the module will attempt to connect to a secondary LDAP 
    server if one is specified. The default is 10 seconds.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LDAPVerifyServerCert</name>
<description>Force server certificate verification</description>
<syntax>LDAPVerifyServerCert <var>On|Off</var></syntax>
<default>LDAPVerifyServerCert On</default>
<contextlist><context>server config</context></contextlist>

<usage>
    <p>Specifies whether to force the verification of a 
     server certificate when establishing an SSL connection to the 
     LDAP server.</p>
</usage>
</directivesynopsis>

</modulesynopsis>