<?xml version="1.0" ?>
<?xml-stylesheet href="auth_ldap.xsl" type="text/xsl"?>
<!DOCTYPE module SYSTEM "auth_ldap.dtd" 
[
<!-- <!ENTITY authldap "<modulename>auth_ldap</modulename>" > -->
<!ENTITY authldap "auth_ldap">
]
>

<!--
   Copyright (c) 2000,2001 Dave Carrigan <dave@rudedog.org>
   All rights reserved.
      
   This module is free software; you can redistribute it and/or modify
   it under the same terms as Apache itself. This module is
   distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or
   FITNESS FOR A PARTICULAR PURPOSE. The copyright holder of this
   module can not be held liable for any general, special, incidental
   or consequential damages arising out of the use of the module.

   $Id: auth_ldap.xml,v 1.14 2001/07/04 14:38:54 dave Exp $
-->


<module title="The auth_ldap Module for Apache">

  <intro>
    <p>
      This is an authentication module for Apache that allows Apache to
      authenticate HTTP clients using user entries in an LDAP
      directory. The current stable version is 1.6.0, while the latest
      development release is 1.7.0. The latest version and the change
      log is always available at
      <link href="http://www.rudedog.org/auth_ldap/">
	http://www.rudedog.org/auth_ldap/</link>.
    </p>

    <p>
	&authldap; supports the following features:
    </p>

    <list type="bullet">
      <item>
	Support for both Unix and Windows NT. As with Apache, Windows NT
	support is not as stable as Unix support. <emph>Please note that
	I have not been able to test &authldap; 1.6 and later under
	Windows. I do not have access to a Windows development
	environment any more. Since some of the changes to &authldap; in
	1.6 were significant, I can no longer guarantee that &authldap;
	will work under Windows.</emph>
      </item>

      <item>
	Known to support the
	<link href="http://www.openldap.org/">
	  OpenLDAP SDK</link> (both 1.x and 2.x),
	and the <link href="http://www.iplanet.com/downloads/developer/">iPlanet
	  (Netscape)</link> SDK.
      </item>

      <item>
	Complex authorization policies can be implemented by
	representing the policy with LDAP filters.
      </item>

      <item>
	Support for Microsoft FrontPage allows FrontPage users to
	control access to their webs, while retaining LDAP for user
	authentication.
      </item>

      <item>
	Uses extensive caching of LDAP operations for increased
	performance.
      </item>

      <item>
	Support for LDAP over SSL (requires the Netscape SDK) or TLS
	(requires the OpenLDAP 2.x SDK).
      </item>

    </list>
  </intro>

  <section title="Building the Module" anchor="building">
    <p>
      The module is compatible with Apache 1.3.x. To use the SSL
      extensions, you must use the Netscape SDK. To use TLS, you must
      use the OpenLDAP 2.x SDK. 
    </p> 

    <p>
      Under Unix, &authldap; can be built as a DSO (Dynamic
      Shared Object) using Apache's <command>apxs</command> program. You
      should be able to build it using the old-style
      <command>Configure</command> method, but I don't personally use that
      method, so I can't guarantee support for it. The directions in
      this section apply to building &authldap; as a DSO.
    </p>

    <p>
      Note that a separate makefile is provided for building under
      Windows NT with Visual C++ 5.0.
    </p>

    <list type="numbered">
      <item>
	Run the <command>configure</command> script to generate the
	<filename>Makefile</filename>. <command>configure</command>
	accepts the following options.
	<table bgcolor="#ffffff">
	  <tr valign="top">
	    <th colspan="1" align="left">Option</th>
	    <th colspan="1" align="left">Comments</th>
	  </tr>
	  <tr valign="top">
	    <td colspan="1" align="left">--with-apxs=<command>/path/to/apxs</command></td>
	    <td colspan="1" align="left">
	      Specifies the path to Apache's <command>apxs</command>
	      command. If not provided, <command>configure</command>
	      will search your path.
	    </td>
	  </tr>

	  <tr valign="top">
	    <td colspan="1" align="left">
	      --with-ldap-sdk=<attrval>sdk</attrval>
	    </td>
	    <td colspan="1" align="left">
	      Specifies the LDAP SDK that you are using. For OpenLDAP,
	      use <attrval>openldap</attrval>. For Netscape, use
	      <attrval>netscape</attrval>. If you're using a different
	      SDK, specify <attrval>other</attrval>. If not provided,
	      the default is <attrval>openldap</attrval>.
	    </td>
	  </tr>

	  <tr valign="top">
	    <td colspan="1" align="left">
	      --with-sdk-headers=<filename>/path/to/headers</filename>
	    </td>
	    <td colspan="1" align="left">
	      Specifies the directory that contains the LDAP SDK include files.
	    </td>
	  </tr>

	  <tr valign="top">
	    <td colspan="1" align="left">
	      --with-sdk-libs=<filename>/path/to/libs</filename>
	    </td>
	    <td colspan="1" align="left">
	      Specifies the directory that contains the LDAP SDK libraries.
	    </td>
	  </tr>

	  <tr valign="top">
	    <td colspan="1" align="left">--with-ssl</td>
	    <td colspan="1" align="left">Build &authldap; with SSL support.</td>
	  </tr>

	  <tr valign="top">
	    <td colspan="1" align="left">--with-shared-cache</td>
	    <td colspan="1" align="left">
	      Include support for the shared LDAP cache. The default is
	      to have the shared cache enabled. To turn it off, use the
	      option <emph>--without-shared-cache</emph>. Note that the
	      shared cache requires that Apache was built with MM
	      support. If Apache was not built with MM support, then
	      this option will do nothing, even if enabled. It is safe
	      to ignore this option.
	    </td>
	  </tr>

	  <tr valign="top">
	    <td colspan="1" align="left">--with-activate</td>
	    <td colspan="1" align="left">
	      Include commands during the installation to activate
	      &authldap;.  Your Apache's <filename>httpd.conf</filename>
	      file will be modified during installation if this option
	      is on.
	    </td>
	  </tr>

	  <tr valign="top">
	    <td colspan="1" align="left">--with-frontpage</td>
	    <td colspan="1" align="left">
	      Include support for the <link href="#frontpage">FrontPage hack</link>.
	    </td>
	  </tr>
	</table>
      </item>
      
      <item>
	Run <command>make; make install</command> to install the module
	with the rest of your Apache modules.
      </item>

      <item>
	To load the module, add an appropriate <directive>LoadModule</directive>
	directive to your <filename>httpd.conf</filename> file, such as

	<config><![CDATA[
# For Unix
LoadModule   auth_ldap_module    libexec/auth_ldap.so

# For Windows NT
LoadModule   auth_ldap_module    modules/AuthLDAP.dll]]></config>

      </item>
    </list>

    <p>
      Note that this module has not been extensively tested under
      Windows NT, as I do not have easy access to an NT box. Because
      Apache on NT is threaded, there are a lot of concurrency issues. I
      think that I have addressed most of the concurrency issues,
      although the locks are pretty coarse grained.  If you have any
      experiences, good or bad, with the module under Windows NT, please
      let me know, so I can improve these instructions and the
      module. I'm especially open to receiving code improvements for NT.
    </p>
  </section>

  <section title="Operation" anchor="operation">
    <p>
      There are two phases in granting access to a user.  The first
      phase is authentication, in which &authldap; verifies that the
      user's credentials are valid. This also called the
      <emph>search/bind</emph> phase. The second phase is authorization,
      in which &authldap; determines if the authenticated user is
      allowed access to the resource in question. This is also known as
      the <emph>compare</emph> phase.
    </p>

    <section title="The Authentication Phase" anchor="authenphase">
      <p>
	During the authentication phase, &authldap; searches for an
	entry in the directory that matches the username that the HTTP
	client passes. If a single unique match is found, then
	&authldap; attempts to bind to the directory server using the DN
	of the entry plus the password provided by the HTTP
	client. Because it does a search, then a bind, it is often
	referred to as the search/bind phase. Here are the steps taken
	during the search/bind phase.
      </p>

      <list type="numbered">
	<item>
	  Generate a search filter by combining the attribute and filter
	  provided in the <link href="#dir:AuthLDAPURL"><directive>
	    AuthLDAPURL</directive></link>
	  directive with the username passed by the HTTP client.
	</item>

	<item>
	  Search the directory using the generated filter. If the search
	  does not return exactly one entry, deny or decline access.
	</item>

	<item>
	  Fetch the distinguished name of the entry retrieved from the
	  search and attempt to bind to the LDAP server using the DN and
	  the password passed by the HTTP client. If the bind is
	  unsuccessful, deny or decline access.
	</item>
      </list>

      <p>
	The following directives are used during the search/bind phase
      </p>

      <table bgcolor="#ffffff">
	<tr valign="top">
	  <td colspan="1" align="left">
	    <link href="#dir:AuthLDAPURL">AuthLDAPURL</link>
	  </td>
	  <td colspan="1" align="left">
	    Specifies the LDAP server, the base DN, the attribute to use
	    in the search, as well as the extra search filter to use.
	  </td>
	</tr>
	<tr valign="top">
	  <td colspan="1" align="left">
	    <link href="#dir:AuthLDAPBindDN">AuthLDAPBindDN</link>
	  </td>
	  <td colspan="1" align="left">
	    An optional DN to bind with during the search phase.
	  </td>
	</tr>
	<tr valign="top">
	  <td colspan="1" align="left">
	    <link href="#dir:AuthLDAPBindPassword">AuthLDAPBindPassword</link>
	  </td>
	  <td colspan="1" align="left">
	    An optional password to bind with during the search phase.
	  </td>
	</tr>
      </table>
    </section>

    <section title="The Authorization Phase" anchor="authorphase">
      <p>
	During the authorization phase, &authldap; attempts to determine
	if the user is authorized to access the resource. Many of these
	checks require &authldap; to do a compare operation on the LDAP
	server. This is why this phase is often referred to as the
	compare phase. &authldap; accepts the following <link
	href="#requiredirectives"><directive>require</directive>
	directives</link> to determine if the credentials are
	acceptable:
      </p>

      <list type="bullet">
	<item>
	  Grant access if there is a <link href="#requser"><directive>
	    require valid-user</directive></link> directive.
	</item>
	
	<item>
	  Grant access if there is a <link
	  href="#reqgroup"><directive>require user</directive></link>
	  directive, and the username in the directive matches the
	  username passed by the client.
	</item>
	
	<item>
	  Grant access if there is a <link
	  href="#reqdn"><directive>require dn</directive></link>
	  directive, and the DN in the directive matches the DN fetched
	  from the LDAP directory.
	</item>
	
	<item>
	  Grant access if there is a <link
	  href="#reqgroup"><directive>require group</directive></link>
	  directive, and the DN fetched from the LDAP directory (or the
	  username passed by the client) occurs in the LDAP group.
	</item>
	
	<item>
	  otherwise, deny or decline access
	</item>
	
      </list>

      <p>
	&authldap; uses the following directives during the compare
	phase:
      </p>

      <table bgcolor="#ffffff">
	<tr>
	  <td>
	    <link href="#dir:AuthLDAPURL"><directive>AuthLDAPURL</directive></link>
	  </td>
	  <td colspan="1" align="left">
	    The attribute specified in the URL is used in compare
	    operations for the <directive>require user</directive>
	    operation.
	  </td>
	</tr>
	<tr>
	  <td>
	    <link href="#dir:AuthLDAPCompareDNOnServer"><directive>
		AuthLDAPCompareDNOnServer</directive></link>
	  </td>
	  <td colspan="1" align="left">
	    Determines the behavior of the <directive>require
	    dn</directive> directive.
	  </td>
	</tr>
	<tr>
	  <td>
	    <link href="#dir:AuthLDAPGroupAttribute"><directive>
		AuthLDAPGroupAttribute</directive></link>
	  </td>
	  <td colspan="1" align="left">
	    Determines the attribute to use for comparisons in the
	    <directive>require group</directive> directive.
	  </td>
	</tr>
	<tr>
	  <td>
	    <link href="#dir:AuthLDAPGroupAttributeIsDN"><directive>
		AuthLDAPGroupAttributeIsDN</directive></link>
	  </td>
	  <td colspan="1" align="left">
	    Specifies whether to use the user DN or the username when
	    doing comparisons for the <directive>require
	    group</directive> directive.
	  </td>
	</tr>
      </table>
    </section>
  </section>

  <section title="Auth_ldap Directives" anchor="directives">
    <p>
      This section contains the complete list of directives that are
      used by the &authldap; module.
    </p>      

    <directive-doc name="AuthLDAPAuthoritative" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-flag default="on"/>
      </syntax>

      <p>
	Set to <directive-value>off</directive-value> if this module should let other
	authentication modules attempt to authenticate the user,
	should authentication with this module fail. Control is only
	passed on to lower modules if there is no DN or rule that matches
	the supplied user name (as passed by the client). 
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPBindDN" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  distinguished-name
	</syn-value>
      </syntax>
      <p>
	An optional DN used to bind to the server when searching for
	entries. If not provided, &authldap; will use an
	anonymous bind.
      </p>
    </directive-doc>
    
    <directive-doc name="AuthLDAPBindPassword" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  password
	</syn-value>
      </syntax>
      <p>
	A bind password to use in conjunction with the bind DN. Note
	that the bind password is probably sensitive data, and should be
	properly protected. You should only use the <link
	href="#dir:AuthLDAPBindDN"><directive>AuthLDAPBindDN</directive></link>
	and <link
	href="#dir:AuthLDAPBindPassword"><directive>AuthLDAPBindPassword</directive></link>
	if you absolutely need them to search the directory.
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPCacheSize" context="server config" override="Not Applicable" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  size
	</syn-value>
      </syntax>

      <p>
	Specifies the maximum size of the primary LDAP cache. This cache
	contains successful search/binds. Set it to 0 to turn of
	search/bind caching. The default size is 1024 cached
	searches. See the <link href="#caching">section below on
	caching</link> for complete information on caching LDAP
	operations in &authldap;.
      </p>

    </directive-doc>

    <directive-doc name="AuthLDAPCacheTTL" context="server config" override="Not Applicable" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  time
	</syn-value>
      </syntax>
      <p>
	Specifies the time (in seconds) that an item in the search/bind
	cache remains valid. The default is 600 seconds (10 minutes). A
	value of 0 means that items in the cache never go stale.
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPCertDBPath" context="server config" override="Not Applicable" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  /path/to/cert7.db/directory
	</syn-value>
      </syntax>

      <p>
	Specifies in which directory &authldap; should look for the
	certificate authorities database. There should be a file named
	<filename>cert7.db</filename> in that directory.
      </p>

    </directive-doc>

    <directive-doc name="AuthLDAPCompareDNOnServer" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-flag default="on"/>
      </syntax>
      <p>
	When set, &authldap; will use the LDAP server to compare the
	DNs. This is the only foolproof way to compare DNs. &authldap;
	will search the directory for the DN specified with the <link
	href="#reqdn"><directive>require dn</directive></link>
	directive, then, retrieve the DN and compare it with the DN
	retrieved from the user entry. If this directive is not set,
	&authldap; simply does a string comparison. It is possible to
	get false negatives with this approach, but it is much
	faster. Note the &authldap; cache can speed up DN comparison in
	most situations.
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPDereferenceAliases" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  never | searching | finding | always
	</syn-value>
      </syntax>
      <p>
	This directive specifies when &authldap; will de-reference
	aliases during LDAP operations. The default is
	<vartext>always</vartext>.
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPEnabled" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-flag default="on"/>
      </syntax>

      <p>
	Set to <directive-value>off</directive-value> to disable
	&authldap; in certain directories. This is useful if you have
	&authldap; enabled at or near the top of your tree, but want to
	disable it completely in certain locations.
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPFrontPageHack" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-flag default="off"/>
      </syntax>

      <p>
	See the section on <link href="#frontpage">using Microsoft
	FrontPage</link> with &authldap;.
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPGroupAttribute" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  attribute
	</syn-value>
      </syntax>
      <p>
	This directive specifies which LDAP attributes are used to check
	for group membership. Up to 10 attributes can be used by
	specifying this directive multiple times. If not specified, then
	&authldap; uses the <attribute>member</attribute> and
	<attribute>uniquemember</attribute> attributes.
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPGroupAttributeIsDN" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-flag default="on"/>
      </syntax>
      <p>
	When set, this directive says to use the distinguished name of
	the client username when checking for group
	membership. Otherwise, the username will be used. For example,
	assume that the client sent the username
	<username>bjenson</username>, which corresponds to the LDAP DN
	<dn>cn=Babs Jenson, o=Airius</dn>. If this directive is set,
	&authldap; will check if the group has <dn>cn=Babs Jenson,
	o=Airius</dn> as a member. If this directive is not set, then
	&authldap; will check if the group has
	<username>bjenson</username> as a member.
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPOpCacheSize" context="server config" override="Not Applicable" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  size
	</syn-value>
      </syntax>

      <p>
	This specifies the size of the cache &authldap; uses to
	cache LDAP compare operations. The default is 1024
	entries. Setting it to 0 disables operation caching.
      </p>
    </directive-doc>

    <directive-doc name="AuthLDAPOpCacheTTL" context="server config" override="Not Applicable" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  time
	</syn-value>
      </syntax>

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

    <directive-doc name="AuthLDAPRemoteUserIsDN" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">

      <syntax>
	<syn-flag default="off"/>
      </syntax>

      <p>
	If this directive is set to on, the value of the
	<vartext>REMOTE_USER</vartext> environment variable will be set to the
	full distinguished name of the authenticated user, rather than
	just the username that was passed by the client. It is turned
	off by default, which is consistent with the behavior of
	previous
	  &authldap; releases.
      </p>

    </directive-doc>    

    <directive-doc name="AuthLDAPStartTLS" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">

      <syntax>
	<syn-flag default="off"/>
      </syntax>

      <p>
	If this directive is set to on, &authldap; will start a secure
	TLS session after connecting to the LDAP server. This requires
	your LDAP server to support TLS.
      </p>

    </directive-doc>    
    
    <directive-doc name="AuthLDAPUrl" context="directory, .htaccess" override="AuthConfig" status="Extension" module="auth_ldap">
      <syntax>
	<syn-value>
	  url
	</syn-value>
      </syntax>

      <p>
	An RFC 2255 URL which specifies the LDAP search parameters to
	use. The syntax of the URL is

	<config>
ldap://host:port/basedn?attribute?scope?filter</config>
      </p>

      <table bgcolor="#ffffff">
	<tr valign="top">
	  <td colspan="1" align="left">ldap</td>
	  <td colspan="1" align="left">
	    For regular ldap, use the string <vartext>ldap</vartext>. For secure
	    LDAP, use <vartext>ldaps</vartext> instead. Secure LDAP is only
	    available if &authldap; was compiled with SSL
	    support.
	  </td>
	</tr>
	<tr valign="top">
	  <td colspan="1" align="left">host:port</td>
	  <td colspan="1" align="left">
	    <p>
	      The name/port of the ldap server (defaults to
	      <vartext>localhost:389</vartext> for <vartext>ldap</vartext>, and
	      <vartext>localhost:636</vartext> for <vartext>ldaps</vartext>). To specify
	      multiple, redundant LDAP servers, just list all servers,
	      separated by spaces. &authldap; will try
	      connecting to each server in turn, until it makes a
	      successful connection.
	    </p>

	    <p>
	      Once a connection has been made to a server, that
	      connection remains active for the life of the
	      <command>httpd</command> process, or until the LDAP server goes
	      down.
	    </p>

	    <p>
	      If the LDAP server goes down and breaks an existing
	      connection, &authldap; will attempt to re-connect,
	      starting with the primary server, and trying each
	      redundant server in turn. Note that this is different than 
	      a true round-robin search.
	    </p>
	  </td>
	</tr>

	<tr valign="top">
	  <td colspan="1" align="left">basedn</td>
	  <td colspan="1" align="left">
	    The DN of the branch of the directory where all searches
	    should start from. At the very least, this must be the top
	    of your directory tree, but could also specify a subtree in
	    the directory.
	  </td>
	</tr>

	<tr valign="top">
	  <td colspan="1" align="left">attribute</td>
	  <td colspan="1" align="left">
	    The attribute to search for. Although RFC 2255 allows a
	    comma-separated list of attributes, only the first attribute
	    will be used, no matter how many are provided. If no
	    attributes are provided, the default is to use
	    <attribute>uid</attribute>. It's a good idea to choose an attribute that
	    will be unique across all entries in the subtree you will be
	    using.
	  </td>
	</tr>

	<tr valign="top">
	  <td colspan="1" align="left">scope</td>
	  <td colspan="1" align="left">
	    The scope of the search. Can be either <vartext>one</vartext> or
	    <vartext>sub</vartext>. Note that a scope of <vartext>base</vartext> is also
	    supported by RFC 2255, but is not supported by this
	    module. If the scope is not provided, or if <vartext>base</vartext>
	    scope is specified, the default is to use a scope of
	    <vartext>sub</vartext>.
	  </td>
	</tr>

	<tr valign="top">
	  <td colspan="1" align="left">filter</td>
	  <td colspan="1" align="left">
	    A valid LDAP search filter. If not provided, defaults to
	    <filter>(objectClass=*)</filter>, which will search for all
	    objects in the tree. Filters are limited to approximately
	    8000 characters (the definition of
	    <vartext>MAX_STRING_LEN</vartext> in the Apache source code). This
	    should be than sufficient for any application.
	  </td>
	</tr>
      </table>

      <p>
	When doing searches, the attribute, filter and username passed
	by the HTTP client are combined to create a search filter that
	looks like
	<filter>(&amp;(<vartext>filter</vartext>)(<vartext>attribute</vartext>=<vartext>username</vartext>))</filter>.
      </p>

      <p>
	For example, consider an URL of
	<vartext>ldap://ldap.airius.com/o=Airius?cn?sub?(posixid=*)</vartext>.
	When a client attempts to connect using a username of 
	<username>
	  Babs Jenson</username>, the resulting search filter will be
	<filter>(&amp;(posixid=*)(cn=Babs Jenson))</filter>.
      </p>

      <p>
	See below for examples of <link
	href="#dir:AuthLDAPURL"><directive>AuthLDAPURL</directive></link>
	URLs.
      </p>

    </directive-doc>

  </section>

  <section title="The require Directives" anchor="requiredirectives">

    <p>
      Apache's <directive>require</directive> directives are used during
      the authorization phase to ensure that a user is allowed to access
      a resource.
    </p>

    <section title="require valid-user" anchor="reqvaliduser">
      <p>
	If this directive exists, &authldap; grants access to any user
	that has successfully authenticated during the search/bind
	phase.
      </p>
    </section>
    <section title="require user" anchor="requser">

      <p>
	The <directive>require user</directive> directive specifies what
	usernames can access the resource. Once &authldap; has retrieved
	a unique DN from the directory, it does an LDAP compare
	operation using the username specified in the <directive>require
	user</directive> to see if that username is part of the
	just-fetched LDAP entry. Multiple users can be granted access by
	putting multiple usernames on the line, separated with
	spaces. If a username has a space in it, then it must be the
	only user on the line. In this case, multiple users can be
	granted access by using multiple <directive>require
	user</directive> directives, with one user per line. For
	example, with a <directive>AuthLDAPURL</directive> of
	<vartext>ldap://ldap/o=Airius?cn</vartext> (i.e.,
	<attribute>cn</attribute> is used for searches), the following
	require directives could be used to restrict access:

	<config><![CDATA[
require user Barbara Jenson
require user Fred User
require user Joe Manager]]></config>
      </p>

      <p>
	Because of the way that &authldap; handles this directive,
	Barbara Jenson could sign on as <username>Barbara
	Jenson</username>, <username>Babs Jenson</username> or any other
	<attribute>cn</attribute> that she has in her LDAP entry. Only
	the single <directive>require user</directive> line is needed to
	support all values of the attribute in the user's entry.
      </p>

      <p>
	If the <attribute>uid</attribute> attribute was used instead of
	the <attribute>cn</attribute> attribute in the URL above, the
	above three lines could be condensed to
      </p>

      <p>
	<config>
require user bjenson fuser jmanager</config>
      </p>
    </section>

    <section title="require group" anchor="reqgroup">

      <p>
	This directive specifies an LDAP group whose members are allowed
	access.  It takes the distinguished name of the LDAP group. For
	example, assume that the following entry existed in the LDAP
	directory:
      </p>

      <p>
	<config><![CDATA[
dn: cn=Administrators, o=Airius
objectClass: groupOfUniqueNames
uniqueMember: cn=Barbara Jenson, o=Airius
uniqueMember: cn=Fred User, o=Airius]]></config>
      </p>

      <p>
	The following directive would grant access to both Fred and
	Barbara:
      </p>

      <p>
	<config>
require group cn=Administrators, o=Airius</config>
      </p>

      <p>
	Behavior of this directive is modified by the 
	<link href="#dir:AuthLDAPGroupAttribute">
	  <directive>AuthLDAPGroupAttribute</directive></link>
	and <link href="#dir:AuthLDAPGroupAttributeIsDN">
	  <directive>AuthLDAPGroupAttributeIsDN</directive></link>
	directives.
      </p>
    </section>

    <section title="require dn" anchor="reqdn">
      <p>
	The <directive>require dn</directive> directive allows the
	administrator to grant access based on distinguished names. It
	specifies a DN that must match for access to be granted. If the
	distinguished name that was retrieved from the directory server
	matches the distinguished name in the <directive>require
	dn</directive>, then authorization is granted.
      </p>

      <p>
	The following directive would grant access to a specific DN:
	<config>
require dn cn=Barbara Jenson, o=Airius</config>
      </p>

      <p>
	Behavior of this directive is modified by the 
	<link href="#dir:AuthLDAPCompareDNOnServer">
	  <directive>AuthLDAPCompareDNOnServer</directive></link>
	directive.
      </p>

    </section>
  </section>

  <section title="Examples" anchor="examples">

    <list type="bullet">
      <item>
	Grant access to anyone who exists in the LDAP directory, using
	their UID for searches. 

	<config>
AuthLDAPURL ldap://ldap1.airius.com:389/ou=People, o=Airius?uid?sub?(objectClass=*)
require valid-user</config>
      </item>

      <item>
	The next example is the same as above; but with the fields that
	have useful defaults omitted. Also, note the use of a redundant
	LDAP server.

	<config>
AuthLDAPURL ldap://ldap1.airius.com ldap2.airius.com/ou=People, o=Airius
require valid-user</config>
      </item>

      <item>
	The next example is similar to the previous one, but is uses the
	common name instead of the UID.  Note that this could be
	problematical if multiple people in the directory share the same
	<attribute>cn</attribute>, because a search on
	<attribute>cn</attribute> <emph>must</emph> return exactly one
	entry. That's why this approach is not recommended: it's a
	better idea to choose an attribute that is guaranteed unique in
	your directory, such as <attribute>uid</attribute>.

	<config>
AuthLDAPURL ldap://ldap.airius.com/ou=People, o=Airius?cn
require valid-user</config>
      </item>

      <item>
	Grant access to anybody in the Administrators group. The users
	must authenticate using their UID.

	<config>
AuthLDAPURL ldap://ldap.airius.com/o=Airius?uid
require group cn=Administrators, o=Airius</config>
      </item>

      <item>
	The next example assumes that everyone at Airius who carries an
	alphanumeric pager will have an LDAP attribute of
	<attribute>qpagePagerID</attribute>. The example will grant access only to
	people (authenticated via their UID) who have alphanumeric
	pagers:

	<config>
AuthLDAPURL ldap://ldap.airius.com/o=Airius?uid??(qpagePagerID=*)
require valid-user</config>
      </item>

      <item>
	<p> The next example demonstrates the power of using filters to
	accomplish complicated administrative requirements. Without
	filters, it would have been necessary to create a new LDAP group
	and ensure that the group's members remain synchronized with the
	pager users. This becomes trivial with filters. The goal is to
	grant access to anyone who has a filter, plus grant access to
	Joe Manager, who doesn't have a pager, but does need to access
	the same resource:

	<config>
AuthLDAPURL ldap://ldap.airius.com/o=Airius?uid??(|(qpagePagerID=*)(uid=jmanager))
require valid-user</config>

	This last may look confusing at first, so it helps to evaluate
	what the search filter will look like based on who connects, as
	shown below. The text in blue is the part that is filled in
	using the attribute specified in the URL.  The text in red is
	the part that is filled in using the filter specified in the
	URL. The text in green is filled in using the information that
	is retrieved from the HTTP client. If Fred User connects as
	<username>fuser</username>, the filter would look like
	</p>
	<p>
	  <filter>(&amp;<filtcolor color="red">(|(qpagePagerID=*)(uid=jmanager))</filtcolor>(<filtcolor color="blue">uid</filtcolor>=<filtcolor color="green">fuser</filtcolor>))</filter>
	</p>
	
	<p>
	  The above search will only succeed if
	  <username>fuser</username> has a pager.  When Joe Manager
	  connects as <username>jmanager</username>, the filter looks
	  like
	</p>
	<p>
	  <filter>(&amp;<filtcolor color="red">(|(qpagePagerID=*)(uid=jmanager))</filtcolor>(<filtcolor color="blue">uid</filtcolor>=<filtcolor color="green">jmanager</filtcolor>))</filter>	  
	</p>

	<p>
	  The above search will succeed whether
	  <username>jmanager</username> has a pager or not.
	</p>

      </item>
    </list>
  </section>

  <section title="Caching in auth_ldap" anchor="caching">
    <p>
      For improved performance, &authldap; 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
	&authldap;-protected pages. In addition, the load on the
      LDAP server will be significantly decreased.
    </p>

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

    <section title="The Search/Bind Cache" anchor="sbcaching">

      <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
	(i.e., 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>
	&authldap; 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, &authldap;
	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, &authldap; bypasses the search/bind phase.
      </p>

      <p>
	The search and bind cache is controlled with the 
	<link href="#dir:AuthLDAPCacheSize">
	  <directive>AuthLDAPCacheSize</directive></link>
	and <link href="#dir:AuthLDAPCacheTTL">
	  <directive>AuthLDAPCacheTTL</directive></link>
	directives. 
      </p>
    </section>

    <section title="Operation Caches" anchor="opcaches">

      <p>
	During the compare phase, &authldap; uses two operation caches
	to cache the compare operations that it does. The first compare
	cache is used to cache the results of compares done for the
	<directive>require user</directive> and <directive>require
	group</directive> directives. The second compare cache is used
	to cache the results of compares done for the <directive>require
	dn</directive> directive.
      </p>

      <p>
	The behavior of both of these caches is controlled with the
	<link href="#dir:AuthLDAPOpCacheSize">
	  <directive>AuthLDAPOpCacheSize</directive></link> and 
	<link href="#dir:AuthLDAPOpCacheTTL">
	  <directive>AuthLDAPOpCacheTTL</directive></link>
	directives.
      </p>
    </section>

    <section title="Monitoring the Cache " anchor="cachemonitor">
      <p>
	&authldap; has a content handler that allows administrators to
	monitor the cache performance. The name of the content handler
	is <vartext>auth-ldap-info</vartext>, so the following
	directives could be used to access the &authldap; cache
	information: <config><![CDATA[
<Location /server/cache-info >
 SetHandler auth-ldap-info
</Location>]]></config>
	By fetching the URL
	<vartext>http://servername/cache-info</vartext>, the
	administrator can get a status report of every cache that is
	used by &authldap; cache. Note that if Apache does not support
	MM-style shared memory, then each <command>httpd</command>
	instance has its own cache, so reloading the URL will result in
	different information each time, depending on which
	<command>httpd</command> instance processes the request. 
      </p>
    </section>
  </section>

  <section title="Benchmarks" anchor="benchmarks">

    <p>
      These benchmarks compare the performance for different cache
      configurations. They list the time to complete the benchmark, and
      the number of LDAP operations actually performed the LDAP
      server. All benchmarks were performed with Apache 1.3.4. Apache,
      the WWW client and the directory server all resided on the same
      system.
    </p>

    <p>
      <emph>Note!</emph> These benchmarks were performed using
	&authldap; 1.4, which used a much different
      caching strategy, the meaning of some of the benchmarks will not
      be apparent. The latest version of &authldap; uses a strategy that
      should be much more efficient in most situations, so the
      benchmarks are mostly of use only for historical reasons.
    </p>

    <p>
      The first benchmark did 10,000 retrievals of the same page. The
      page was protected by a <directive>&lt;Location&gt;</directive>
      specification in <filename>access.conf</filename> that contained a single
      <directive>require user</directive> directive.
    </p>

    <table bgcolor="#cccccc">
      <tr valign="top">
	<th colspan="1" align="right"></th>
	<th colspan="1" align="right"></th>
	<th colspan="5" align="center">LDAP Operations</th>
      </tr>
      <tr valign="top">
	<td colspan="1" align="left">Cache Level</td>
	<td colspan="1" align="left">Real Time</td>
	<td colspan="1" align="left">Connect</td>
	<td colspan="1" align="left">Bind</td>
	<td colspan="1" align="left">Search</td>
	<td colspan="1" align="left">Compare</td>
	<td colspan="1" align="left">Total</td>
      </tr>
      <tr valign="top">
	<td colspan="1" align="left">None</td>
	<td colspan="1" align="right">6:04</td>
	<td colspan="1" align="right">      6</td><!-- connect -->
	<td colspan="1" align="right"> 60,006</td><!-- bind -->
	<td colspan="1" align="right"> 30,000</td><!-- search -->
	<td colspan="1" align="right"> 30,000</td><!-- compare -->
	<td colspan="1" align="right">120,012</td><!-- total -->
      </tr>
      <tr valign="top">
	<td colspan="1" align="left">Search</td>
	<td colspan="1" align="right">4:53</td>
	<td colspan="1" align="right">     6</td><!-- connect -->
	<td colspan="1" align="right">60,006</td><!-- bind -->
	<td colspan="1" align="right">     6</td><!-- search -->
	<td colspan="1" align="right">30,000</td><!-- compare -->
	<td colspan="1" align="right">90,018</td><!-- total -->
      </tr>
      <tr valign="top">
	<td colspan="1" align="left">Search, bind</td>
	<td colspan="1" align="right">2:20</td>
	<td colspan="1" align="right">     6</td><!-- connect -->
	<td colspan="1" align="right">    18</td><!-- bind -->
	<td colspan="1" align="right">     6</td><!-- search -->
	<td colspan="1" align="right">30,000</td><!-- compare -->
	<td colspan="1" align="right">30,030</td><!-- total -->
      </tr>
      <tr valign="top">
	<td colspan="1" align="left">Search, bind, compare</td>
	<td colspan="1" align="right">1:46</td>
	<td colspan="1" align="right"> 6</td><!-- connect -->
	<td colspan="1" align="right">18</td><!-- bind -->
	<td colspan="1" align="right"> 6</td><!-- search -->
	<td colspan="1" align="right"> 6</td><!-- compare -->
	<td colspan="1" align="right">36</td><!-- total -->
      </tr>
    </table>

    <p>
      The second benchmark did 10,000 retrievals of the same page, but
      chose a random username from a pool of 1000 names for each
      connection. The page was protected by a
      <directive>&lt;Location&gt;</directive> specification in
      <filename>access.conf</filename> that contained a <directive>require
	valid-user</directive> directive. Since this doesn't require a LDAP
      compare operation, there is no benchmark for the third level of
      caching (search, bind and compare).
    </p>

    <table bgcolor="#cccccc">
      <tr valign="top">
	<th colspan="1" align="left"></th>
	<th colspan="1" align="left"></th>
	<th colspan="4" align="center">LDAP Operations</th>
      </tr>
      <tr valign="top">
	<td colspan="1" align="left">Cache Level</td>
	<td colspan="1" align="left">Real Time</td>
	<td colspan="1" align="left">Connect</td>
	<td colspan="1" align="left">Bind</td>
	<td colspan="1" align="left">Search</td>
	<td colspan="1" align="left">Total</td>
      </tr>
      <tr valign="top">
	<td colspan="1" align="left">None</td>
	<td colspan="1" align="right">5:47</td>
	<td colspan="1" align="right">     7</td><!-- connect -->
	<td colspan="1" align="right">60,002</td><!-- bind -->
	<td colspan="1" align="right">30,001</td><!-- search -->
	<td colspan="1" align="right">90,009</td><!-- total -->
      </tr>
      <tr valign="top">
	<td colspan="1" align="left">Search</td>
	<td colspan="1" align="right">5:00</td>
	<td colspan="1" align="right">     7</td><!-- connect -->
	<td colspan="1" align="right">60,002</td><!-- bind -->
	<td colspan="1" align="right"> 9,970</td><!-- search -->
	<td colspan="1" align="right">69,979</td><!-- total -->
      </tr>
      <tr valign="top">
	<td colspan="1" align="left">Search, bind</td>
	<td colspan="1" align="right">2:51</td>
	<td colspan="1" align="right">     7</td><!-- connect -->
	<td colspan="1" align="right"> 9,672</td><!-- bind -->
	<td colspan="1" align="right"> 9,968</td><!-- search -->
	<td colspan="1" align="right">19,647</td><!-- total -->
      </tr>
    </table>

    <p>
      These benchmarks are only included to give an idea about how
      caching can improve performance. They do not really simulate real
      world conditions, since both servers and the client were in a
      sandbox.
    </p>
  </section>

  <section title="Using TLS" anchor="usingtls">
    <p>
      To use TLS, simply set the <directive>AuthLDAPStartTLS</directive>
      to on. Nothing else needs to be done (other than ensure that your
      LDAP server is configured for TLS).
    </p>
  </section>

  <section title="Using SSL" anchor="usingssl">

    <p>
      &authldap; will not talk to any SSL server unless that server has
      a certificate signed by a known Certificate Authority. Once you've
      built &authldap; with SSL support,
	&authldap; still needs to be told where it can find a database
      containing the known CAs. This database is in the same format as
      Netscape Communicator's <filename>cert7.db</filename>
      database. The easiest way to get this file is to start up a fresh
      copy of Netscape, and grab the resulting
      <filename>$HOME/.netscape/cert7.db</filename> file.
    </p>

    <p>
      To specify a secure LDAP server, use <vartext>ldaps://</vartext>
      in the <directive>AuthLDAPURL</directive> directive, instead of
      <vartext>ldap://</vartext>. 
    </p>

  </section>

  <section title="Using Microsoft FrontPage with auth_ldap" anchor="frontpage">

    <p>
      Normally, FrontPage uses FrontPage-web-specific user/group files
      (i.e., the <modulename>mod_auth</modulename> module) to handle all
      authentication.  Unfortunately, it is not possible to just change
      to LDAP authentication by adding the proper directives, because it
      will break the <emph>Permissions</emph> forms in the FrontPage
      client, which attempt to modify the standard text-based
      authorization files.
    </p>

    <p>
      To use FrontPage with &authldap;, ensure that &authldap; is
      compiled with the
      <vartext>-DAUTH_LDAP_FRONTPAGE_HACK</vartext>. See the
      <filename>Makefile</filename> for more information.
    </p>

    <p>
      Once a FrontPage web has been created, adding LDAP authentication
      to it is a matter of adding the following directives to
      <emph>every</emph> <filename>.htaccess</filename> file that gets
      created in the web
      <config>
AuthLDAPURL            the url
AuthLDAPAuthoritative  off
AuthLDAPFrontPageHack  on</config>
    </p>
    
    <p>
      <directive>AuthLDAPAuthoritative</directive> must be off to allow
	&authldap; to decline group authentication so that
      Apache will fall back to file authentication for checking group
      membership. This allows the FrontPage-managed group file to be
      used.
    </p>

    <section title="How It Works" anchor="howitworks">
      <p>
	FrontPage restricts access to a web by adding the
	<directive>
	  require valid-user</directive> directive to the
	<filename>.htaccess</filename> files. If
	<directive>AuthLDAPFrontPageHack</directive> is not on, the
	<directive>
	  require valid-user</directive> directive will succeed for any
	user who is valid <emph>as far as LDAP is concerned</emph>. This
	means that anybody who has an entry in the LDAP directory is
	considered a valid user, whereas FrontPage considers only those
	people in the local user file to be valid. The purpose of the
	hack is to force Apache to consult the local user file (which is
	managed by FrontPage) - instead of LDAP - when handling the
	<directive>
	  require valid-user</directive> directive.
      </p>

      <p>
	Once directives have been added as specified above, FrontPage
	users will be able to perform all management operations from the
	FrontPage client.
      </p> 
    </section>

    <section title="Caveats" anchor="fpcaveats">

      <list type="bullet">
	<item>
	  When choosing the LDAP URL, the attribute to use for
	  authentication should be something that will also be valid for
	  putting into a <modulename>mod_auth</modulename> user
	  file. The user ID is ideal for this.
	</item>

	<item>
	  When adding users via FrontPage, FrontPage administrators
	  should choose usernames that already exist in the LDAP
	  directory (for obvious reasons). Also, the password that the
	  administrator enters into the form is ignored, since Apache
	  will actually be authenticating against the password in the
	  LDAP database, and not against the password in the local user
	  file. This could cause confusion for web administrators
	  (although not as much confusion as if the entire FrontPage
	  permissions model is broken).
	</item>

	<item>
	  Apache must be compiled with <modulename>mod_auth</modulename>
	  in order to use FrontPage support. This is because Apache will
	  still use the <modulename>mod_auth</modulename> group file for
	  determine the extent of a user's access to the FrontPage
	  web. Furthermore, &authldap; must be called before
	  <modulename>mod_auth</modulename>. This means that it must be
	  loaded after <modulename>mod_auth</modulename>, because
	  authentication modules are run in reverser order of how they
	  were loaded. Order of modules is controlled by the
	  <directive>LoadModule</directive> and
	  <directive>AddModule</directive> directives.
	</item>

	<item>
	  The directives must be put in the
	  <filename>.htaccess</filename> files. Attempting to put them
	  inside <directive>&lt;Location&gt;</directive> or
	  <directive>&lt;Directory&gt;</directive> directives won't
	  work. This is because &authldap; has to be able to grab the
	  <directive>AuthUserFile</directive> directive that is found in
	  FrontPage <filename>.htaccess</filename> files so that it
	  knows where to look for the valid user list. If the &authldap;
	  directives aren't in the same <filename>.htaccess</filename>
	  file as the FrontPage directives, then the hack won't work,
	  because &authldap; will never get a chance to process the
	  <filename>.htaccess</filename> file, and won't be able to find
	  the FrontPage-managed user file.
	</item>

	<item>
	  FrontPage support is still very experimental. On the whole,
	  FrontPage is a huge fragile steaming pile of goo, and is
	  subject to breakage and other lossage. While I am aware of
	  people who have been using it with no apparent problems, I
	  would not try to do anything fancy with the
	  <filename>.htaccess</filename> files.
	</item>

      </list>
    </section>
  </section>

  <acks>

    <ack email="ajc@bing.wattle.id.au" name="Andrew Cosgriff">
      for suggesting the <directive>AuthLDAPRemoteUserIsDN</directive>
      directive.
    </ack>

    <ack email="kevin.hendrix@mciworldcom.com" name="Kevin Hendrix">
      for code and other advice with the caching functionality.
    </ack>

    <ack email="minfrin@sharp.fm" name="Graham Leggett">
      for goading me into doing SSL support as well as assistance with
      tracking down some thorny Solaris problems, bug reports, patches,
      and lots of other suggestions for improvements.
    </ack>

    <ack email="muscarella@stanford.edu" name="Greg Muscarella">
      for testing and critiquing of early versions.
    </ack>

    <ack email="eshin@mail.law.berkeley.edu" name="Edwin Shin">
      for Win32 testing.
    </ack>

    <ack email="camield@inet.unisource.nl" name="Camiel Dobbelaar">
      for various Makefile patches.
    </ack>

    <ack email="mikki@Elma.FI" name="Mikko Ahonen">
      for patches needed to compile on AIX.
    </ack>

    <ack email="karel.zajicek@ecn.cz" name="Karel Zajicek">
      for suggestions and patches for implementing the
      <directive>AuthLDAPMemberIsDN</directive>.
    </ack>

    <ack email="tony@atomide.com" name="Tony Lindgren"> 
      for suggestions and patches for implementing the shared memory
      caching.
    </ack>

    <ack email="michael@csuite.ns.ca" name="Michael Smith">
      for valuable bug reports.
    </ack>

    <ack email="wpchiu@ied.edu.hk" name="Chiu Wai Pun">
      for suggesting a much better approach to the FrontPage hack. It's
      clean enough now that I may not even call it a hack any more.
    </ack>

    <ack email="j.costlow@f5.com" name="Jeff Costlow">
      for TLS patches and testing.
    </ack>

  </acks>

  <copyright address="dave@rudedog.org">
    <holder years="1998, 1999">Enbridge Pipelines Inc.</holder>
    <holder years="1999-2001">Dave Carrigan</holder>

    <p>
      This module is free software; you can redistribute it and/or
      modify it under the same terms as Apache itself. This module is
      distributed in the hope that it will be useful, but
      <emph>without any warranty</emph>; without even the
      implied warranty of <emph>merchantability</emph> or
      <emph>fitness for a particular purpose</emph>. The
      copyright holder of this module can not be held liable for any
      general, special, incidental or consequential damages arising out
      of the use of the module.
    </p>

  </copyright>
</module>
