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<!DOCTYPE modulesynopsis SYSTEM "/style/modulesynopsis.dtd">

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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>Experimental</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 support requires that <module>mod_ldap</module> be linked

with one of the following LDAP SDKs: <a href="http://www.openldap.org/">

OpenLDAP SDK</a> (both 1.x and 2.x), <a href="http://developer.novell.com/ndk/cldap.htm">

Novell LDAP SDK</a>, native Solaris LDAP SDK, native Microsoft LDAP SDK, or the <a href="http://www.iplanet.com/downloads/developer/">

iPlanet(Netscape)</a> SDK.</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. Some of the

differences are described below:</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 Netscape Communicator / Mozilla web browser. The easiest

way to obtain these files is to grab them from a browser

installation.</p>

<p>Client certificates are specified per connection by referring

to the certificate "nickname", and an optional password may be

specified.</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>Client certificates are specified globally rather than per

connection, and so must be specified with the global certificate

option as below. Trying to set client certificates via the

LDAPTrustedClientCert option will cause an error to be thrown

when httpd starts up.</p>

<p>The SDK supports both SSL and STARTTLS, set using the

LDAPTrustedMode parameter. If an ldaps:// URL is specified,

SSL mode is forced.</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 />

</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>

</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 client certificates <module>mod_ldap</module>

should use when establishing an SSL or TLS connection to an LDAP

server. The type specifies the kind of certificate parameter being

set, depending on the LDAP toolkit being used. Supported types are:

<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>KEY_DER - binary DER encoded private key</li>

<li>KEY_BASE64 - PEM encoded private key</li>

</ul>

</p>

</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>All</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. Not all LDAP toolkits support

per connection client certificates (See the toolkit guide for details).

The type specifies the kind of certificate parameter being

set, depending on the LDAP toolkit being used. Supported types are:

<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>

</p>

</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>All</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>

<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>

</modulesynopsis>