docs/manual/mod/mod_authnz_ldap.xml

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

<name>mod_authnz_ldap</name>
<description>Allows an LDAP directory to be used to store the database
for HTTP Basic authentication.</description>
<status>Extension</status>
<sourcefile>mod_authnz_ldap.c</sourcefile>
<identifier>authnz_ldap_module</identifier>
<compatibility>Available in version 2.1 and later</compatibility>

<summary>
    <p>This module provides authentication front-ends such as
    <module>mod_auth_basic</module> to authenticate users through 
    an ldap directory.</p>
    
    <p><module>mod_authnz_ldap</module> supports the following features:</p>

    <ul>
      <li>Known to support the <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> and the <a
      href="http://www.iplanet.com/downloads/developer/">iPlanet
      (Netscape)</a> SDK.</li>

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

      <li>Uses extensive caching of LDAP operations via <a
      href="mod_ldap.html">mod_ldap</a>.</li>

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

    <p>When using <module>mod_auth_basic</module>, this module is invoked
    via the <directive module="mod_auth_basic">AuthBasicProvider</directive>
    directive with the <code>ldap</code> value.</p>
</summary>

<seealso><module>mod_ldap</module></seealso>
<seealso><module>mod_auth_basic</module></seealso>
<seealso><module>mod_authz_user</module></seealso>
<seealso><module>mod_authz_groupfile</module></seealso>

<section id="contents"><title>Contents</title>

    <ul>
      <li>
        <a href="#operation">Operation</a> 

        <ul>
          <li><a href="#authenphase">The Authentication
          Phase</a></li>

          <li><a href="#authorphase">The Authorization
          Phase</a></li>
        </ul>
      </li>

      <li>
        <a href="#requiredirectives">The Require Directives</a> 

        <ul>
          <li><a href="#requser">Require ldap-user</a></li>
          <li><a href="#reqgroup">Require ldap-group</a></li>
          <li><a href="#reqdn">Require ldap-dn</a></li>
          <li><a href="#reqattribute">Require ldap-attribute</a></li>
          <li><a href="#reqfilter">Require ldap-filter</a></li>
        </ul>
      </li>

      <li><a href="#examples">Examples</a></li>
      <li><a href="#usingtls">Using TLS</a></li>
      <li><a href="#usingssl">Using SSL</a></li>
      <li><a href="#exposed">Exposing Login Information</a></li>
      <li><a href="#activedirectory">Using Active Directory</a></li>
      <li>
        <a href="#frontpage">Using Microsoft FrontPage with
        <module>mod_authnz_ldap</module></a> 

        <ul>
          <li><a href="#howitworks">How It Works</a></li>
          <li><a href="#fpcaveats">Caveats</a></li>
        </ul>
      </li>
    </ul>
</section>

<section id="operation"><title>Operation</title>

    <p>There are two phases in granting access to a user. The first
    phase is authentication, in which the <module>mod_authnz_ldap</module>
    authentication provider verifies that the user's credentials are valid. 
    This is also called the <em>search/bind</em> phase. The second phase is
    authorization, in which <module>mod_authnz_ldap</module> determines
    if the authenticated user is allowed access to the resource in
    question. This is also known as the <em>compare</em>
    phase.</p>

    <p><module>mod_authnz_ldap</module> registers both an authn_ldap authentication
    provider and an authz_ldap authorization handler.  The authn_ldap
    authentication provider can be enabled through the 
    <directive module="mod_auth_basic">AuthBasicProvider</directive> directive 
    using the <code>ldap</code> value. The authz_ldap handler extends the 
    <directive module="mod_authz_core">Require</directive> directive's authorization types
    by adding <code>ldap-user</code>, <code>ldap-dn</code> and <code>ldap-group</code> 
    values.</p>

<section id="authenphase"><title>The Authentication
    Phase</title>

    <p>During the authentication phase, <module>mod_authnz_ldap</module>
    searches for an entry in the directory that matches the username
    that the HTTP client passes. If a single unique match is found,
    then <module>mod_authnz_ldap</module> 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>

    <ol>
      <li>Generate a search filter by combining the attribute and
      filter provided in the <directive module="mod_authnz_ldap"
      >AuthLDAPURL</directive> directive with
      the username passed by the HTTP client.</li>

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

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

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

    <table>
      <columnspec><column width=".3"/><column width=".7"/></columnspec>
      <tr>
        <td><directive module="mod_authnz_ldap">AuthLDAPURL</directive></td>

        <td>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>
        <td><directive module="mod_authnz_ldap">AuthLDAPBindDN</directive></td>

        <td>An optional DN to bind with
        during the search phase.</td>
      </tr>

      <tr>
        <td><directive
        module="mod_authnz_ldap">AuthLDAPBindPassword</directive></td>

        <td>An optional password to bind
        with during the search phase.</td>
      </tr>
    </table>
</section>

<section id="authorphase"><title>The Authorization Phase</title>

    <p>During the authorization phase, <module>mod_authnz_ldap</module>
    attempts to determine if the user is authorized to access the
    resource.  Many of these checks require
    <module>mod_authnz_ldap</module> to do a compare operation on the
    LDAP server. This is why this phase is often referred to as the
    compare phase. <module>mod_authnz_ldap</module> accepts the
    following <directive module="mod_authz_core">Require</directive>
    directives to determine if the credentials are acceptable:</p>

    <ul>
      <li>Grant access if there is a <a
      href="#reqgroup"><code>Require ldap-user</code></a> directive, and the
      username in the directive matches the username passed by the
      client.</li>

      <li>Grant access if there is a <a href="#reqdn"><code>Require
      ldap-dn</code></a> directive, and the DN in the directive matches
      the DN fetched from the LDAP directory.</li>

      <li>Grant access if there is a <a
      href="#reqgroup"><code>Require ldap-group</code></a> directive, and
      the DN fetched from the LDAP directory (or the username
      passed by the client) occurs in the LDAP group or, potentially, in
      one of its sub-groups.</li>

      <li>Grant access if there is a <a href="#reqattribute">
      <code>Require ldap-attribute</code></a> 
      directive, and the attribute fetched from the LDAP directory
      matches the given value.</li> 

      <li>Grant access if there is a <a href="#reqfilter">
      <code>Require ldap-filter</code></a> 
      directive, and the search filter successfully finds a single user
      object that matches the dn of the authenticated user.</li> 

      <li>otherwise, deny or decline access</li>
    </ul>

    <p>Other <directive module="mod_authz_core">Require</directive> values may also
    be used which may require loading additional authorization modules.</p>

    <ul>
        <li>Grant access to all successfully authenticated users if 
        there is a <a href="#requser"><code>Require valid-user</code></a> 
        directive. (requires <module>mod_authz_user</module>)</li>

        <li>Grant access if there is a <a
        href="#reqgroup"><code>Require group</code></a> directive, and
        <module>mod_authz_groupfile</module> has been loaded with the 
        <directive module="mod_authz_groupfile">AuthGroupFile</directive> 
        directive set.</li>
    
        <li>others...</li>
     </ul>


    <p><module>mod_authnz_ldap</module> uses the following directives during the
    compare phase:</p>

    <table>
      <columnspec><column width=".4"/><column width=".6"/></columnspec>
      <tr>
        <td><directive module="mod_authnz_ldap">AuthLDAPURL</directive> </td>

        <td>The attribute specified in the
        URL is used in compare operations for the <code>Require
        ldap-user</code> operation.</td>
      </tr>

      <tr>
        <td><directive
        module="mod_authnz_ldap">AuthLDAPCompareDNOnServer</directive></td>

        <td>Determines the behavior of the
        <code>Require ldap-dn</code> directive.</td>
      </tr>

      <tr>
        <td><directive
        module="mod_authnz_ldap">AuthLDAPGroupAttribute</directive></td>

        <td>Determines the attribute to
        use for comparisons in the <code>Require ldap-group</code>
        directive.</td>
      </tr>

      <tr>
        <td><directive
        module="mod_authnz_ldap">AuthLDAPGroupAttributeIsDN</directive></td>

        <td>Specifies whether to use the
        user DN or the username when doing comparisons for the
        <code>Require ldap-group</code> directive.</td>
      </tr>

      <tr>
        <td><directive
        module="mod_authnz_ldap">AuthLDAPMaxSubGroupDepth</directive></td>

        <td>Determines the maximum depth of sub-groups that will be evaluated
        during comparisons in the <code>Require ldap-group</code> directive.</td>
      </tr>

      <tr>
        <td><directive
        module="mod_authnz_ldap">AuthLDAPSubGroupAttribute</directive></td>

        <td>Determines the attribute to use when obtaining sub-group members
        of the current group during comparisons in the <code>Require ldap-group</code>
        directive.</td>
      </tr>

      <tr>
        <td><directive
        module="mod_authnz_ldap">AuthLDAPSubGroupClass</directive></td>

        <td>Specifies the LDAP objectClass values used to identify if queried directory
        objects really are group objects (as opposed to user objects) during the
        <code>Require ldap-group</code> directive's sub-group processing.</td>
      </tr>
    </table>
</section>
</section>

<section id="requiredirectives"><title>The Require Directives</title>

    <p>Apache's <directive module="mod_authz_core">Require</directive>
    directives are used during the authorization phase to ensure that
    a user is allowed to access a resource.  mod_authnz_ldap extends the 
    authorization types with <code>ldap-user</code>, <code>ldap-dn</code>, 
    <code>ldap-group</code>, <code>ldap-attribute</code> and 
    <code>ldap-filter</code>.  Other authorization types may also be 
    used but may require that additional authorization modules be loaded.</p>

<section id="requser"><title>Require ldap-user</title>

    <p>The <code>Require ldap-user</code> directive specifies what
    usernames can access the resource. Once
    <module>mod_authnz_ldap</module> has retrieved a unique DN from the
    directory, it does an LDAP compare operation using the username
    specified in the <code>Require ldap-user</code> 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 surrounded with double quotes. Multiple users can also be
    granted access by using multiple <code>Require ldap-user</code>
    directives, with one user per line. For example, with a <directive
    module="mod_authnz_ldap">AuthLDAPURL</directive> of
    <code>ldap://ldap/o=Example?cn</code> (i.e., <code>cn</code> is
    used for searches), the following Require directives could be used
    to restrict access:</p>
<example>
Require ldap-user "Barbara Jenson"<br />
Require ldap-user "Fred User"<br />
Require ldap-user "Joe Manager"<br />
</example>

    <p>Because of the way that <module>mod_authnz_ldap</module> handles this
    directive, Barbara Jenson could sign on as <em>Barbara
    Jenson</em>, <em>Babs Jenson</em> or any other <code>cn</code> that
    she has in her LDAP entry. Only the single <code>Require
    ldap-user</code> line is needed to support all values of the attribute
    in the user's entry.</p>

    <p>If the <code>uid</code> attribute was used instead of the
    <code>cn</code> attribute in the URL above, the above three lines
    could be condensed to</p>
<example>Require ldap-user bjenson fuser jmanager</example>
</section>

<section id="reqgroup"><title>Require ldap-group</title>

    <p>This directive specifies an LDAP group whose members are
    allowed access. It takes the distinguished name of the LDAP
    group. Note: Do not surround the group name with quotes.
    For example, assume that the following entry existed in
    the LDAP directory:</p>
<example>
dn: cn=Administrators, o=Example<br />
objectClass: groupOfUniqueNames<br />
uniqueMember: cn=Barbara Jenson, o=Example<br />
uniqueMember: cn=Fred User, o=Example<br />
</example>

    <p>The following directive would grant access to both Fred and
    Barbara:</p>
<example>Require ldap-group cn=Administrators, o=Example</example>

    <p>Members can also be found within sub-groups of a specified LDAP group
    if <directive module="mod_authnz_ldap">AuthLDAPMaxSubGroupDepth</directive>
    is set to a value greater than 0. For example, assume the following entries
    exist in the LDAP directory:</p>
<example>
dn: cn=Employees, o=Example<br />
objectClass: groupOfUniqueNames<br />
uniqueMember: cn=Managers, o=Example<br />
uniqueMember: cn=Administrators, o=Example<br />
uniqueMember: cn=Users, o=Example<br />
<br />
dn: cn=Managers, o=Example<br />
objectClass: groupOfUniqueNames<br />
uniqueMember: cn=Bob Ellis, o=Example<br />
uniqueMember: cn=Tom Jackson, o=Example<br />
<br />
dn: cn=Administrators, o=Example<br />
objectClass: groupOfUniqueNames<br />
uniqueMember: cn=Barbara Jenson, o=Example<br />
uniqueMember: cn=Fred User, o=Example<br />
<br />
dn: cn=Users, o=Example<br />
objectClass: groupOfUniqueNames<br />
uniqueMember: cn=Allan Jefferson, o=Example<br />
uniqueMember: cn=Paul Tilley, o=Example<br />
uniqueMember: cn=Temporary Employees, o=Example<br />
<br />
dn: cn=Temporary Employees, o=Example<br />
objectClass: groupOfUniqueNames<br />
uniqueMember: cn=Jim Swenson, o=Example<br />
uniqueMember: cn=Elliot Rhodes, o=Example<br />
</example>

    <p>The following directives would allow access for Bob Ellis, Tom Jackson,
    Barbara Jensen, Fred User, Allan Jefferson, and Paul Tilley but would not
    allow access for Jim Swenson, or Elliot Rhodes (since they are at a 
    sub-group depth of 2):</p>
<example>
Require ldap-group cn=Employees, o-Example<br />
AuthLDAPSubGroupDepth 1<br />
</example>

    <p>Behavior of this directive is modified by the <directive
    module="mod_authnz_ldap">AuthLDAPGroupAttribute</directive>, <directive
    module="mod_authnz_ldap">AuthLDAPGroupAttributeIsDN</directive>, <directive
    module="mod_authnz_ldap">AuthLDAPMaxSubGroupDepth</directive>, <directive
    module="mod_authnz_ldap">AuthLDAPSubGroupAttribute</directive>, and <directive
    module="mod_authnz_ldap">AuthLDAPSubGroupClass</directive>
    directives.</p>
</section>

<section id="reqdn"><title>Require ldap-dn</title>

    <p>The <code>Require ldap-dn</code> 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 <code>Require ldap-dn</code>, then
    authorization is granted. Note: do not surround the distinguished
    name with quotes.</p>

    <p>The following directive would grant access to a specific
    DN:</p>
<example>Require ldap-dn cn=Barbara Jenson, o=Example</example>

    <p>Behavior of this directive is modified by the <directive
    module="mod_authnz_ldap">AuthLDAPCompareDNOnServer</directive>
    directive.</p>
</section>

<section id="reqattribute"><title>Require ldap-attribute</title>

    <p>The <code>Require ldap-attribute</code> directive allows the
    administrator to grant access based on attributes of the authenticated
    user in the LDAP directory.  If the attribute in the directory
    matches the value given in the configuration, access is granted.</p>
    
    <p>The following directive would grant access to anyone with
    the attribute employeeType = active</p>

    <example>Require ldap-attribute employeeType=active</example>

    <p>Multiple attribute/value pairs can be specified on the same line
    separated by spaces or they can be specified in multiple 
    <code>Require ldap-attribute</code> directives. The effect of listing 
    multiple attribute/values pairs is an OR operation. Access will be 
    granted if any of the listed attribute values match the value of the 
    corresponding attribute in the user object. If the value of the 
    attribute contains a space, only the value must be within double quotes.</p>

    <p>The following directive would grant access to anyone with
    the city attribute equal to "San Jose" or status equal to "Active"</p>

    <example>Require ldap-attribute city="San Jose" status=active</example>

</section>

<section id="reqfilter"><title>Require ldap-filter</title>

    <p>The <code>Require ldap-filter</code> directive allows the
    administrator to grant access based on a complex LDAP search filter.
    If the dn returned by the filter search matches the authenticated user
    dn, access is granted.</p>
    
    <p>The following directive would grant access to anyone having a cell phone
    and is in the marketing department</p>

    <example>Require ldap-filter &amp;(cell=*)(department=marketing)</example>

    <p>The difference between the <code>Require ldap-filter</code> directive and the 
    <code>Require ldap-attribute</code> directive is that <code>ldap-filter</code> 
    performs a search operation on the LDAP directory using the specified search 
    filter rather than a simple attribute comparison. If a simple attribute 
    comparison is all that is required, the comparison operation performed by 
    <code>ldap-attribute</code> will be faster than the search operation 
    used by <code>ldap-filter</code> especially within a large directory.</p>

</section>

</section>

<section id="examples"><title>Examples</title>

    <ul>
      <li>
        Grant access to anyone who exists in the LDAP directory,
        using their UID for searches. 
<example>
AuthLDAPURL "ldap://ldap1.example.com:389/ou=People, o=Example?uid?sub?(objectClass=*)"<br />
Require valid-user
</example>
      </li>

      <li>
        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. 
<example>AuthLDAPURL "ldap://ldap1.example.com ldap2.example.com/ou=People, o=Example"<br />
Require valid-user
</example>
      </li>

      <li>
        The next example is similar to the previous one, but it
        uses the common name instead of the UID. Note that this
        could be problematical if multiple people in the directory
        share the same <code>cn</code>, because a search on <code>cn</code>
        <strong>must</strong> 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 <code>uid</code>. 
<example>
AuthLDAPURL "ldap://ldap.example.com/ou=People, o=Example?cn"<br />
Require valid-user
</example>
      </li>

      <li>
        Grant access to anybody in the Administrators group. The
        users must authenticate using their UID. 
<example>
AuthLDAPURL ldap://ldap.example.com/o=Example?uid<br />
Require ldap-group cn=Administrators, o=Example
</example>
      </li>

      <li>
        The next example assumes that everyone at Example who
        carries an alphanumeric pager will have an LDAP attribute
        of <code>qpagePagerID</code>. The example will grant access
        only to people (authenticated via their UID) who have
        alphanumeric pagers: 
<example>
AuthLDAPURL ldap://ldap.example.com/o=Example?uid??(qpagePagerID=*)<br />
Require valid-user
</example>
      </li>

      <li>
        <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 pager, plus grant access to Joe Manager, who doesn't
        have a pager, but does need to access the same
        resource:</p>
<example>
AuthLDAPURL ldap://ldap.example.com/o=Example?uid??(|(qpagePagerID=*)(uid=jmanager))<br />
Require valid-user
</example>

        <p>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.  If
        Fred User connects as <code>fuser</code>, the filter would look
        like</p>

        <example>(&amp;(|(qpagePagerID=*)(uid=jmanager))(uid=fuser))</example>

        <p>The above search will only succeed if <em>fuser</em> has a
        pager. When Joe Manager connects as <em>jmanager</em>, the
        filter looks like</p>

        <example>(&amp;(|(qpagePagerID=*)(uid=jmanager))(uid=jmanager))</example>

        <p>The above search will succeed whether <em>jmanager</em>
        has a pager or not.</p>
      </li>
    </ul>
</section>

<section id="usingtls"><title>Using TLS</title>

    <p>To use TLS, see the <module>mod_ldap</module> directives <directive
    module="mod_ldap">LDAPTrustedClientCert</directive>, <directive
    module="mod_ldap">LDAPTrustedGlobalCert</directive> and <directive
    module="mod_ldap">LDAPTrustedMode</directive>.</p>

    <p>An optional second parameter can be added to the 
    <directive module="mod_authnz_ldap">AuthLDAPURL</directive> to override
    the default connection type set by <directive module="mod_ldap">LDAPTrustedMode</directive>.
    This will allow the connection established by an <em>ldap://</em> Url 
    to be upgraded to a secure connection on the same port.</p>
</section>

<section id="usingssl"><title>Using SSL</title>

    <p>To use SSL, see the <module>mod_ldap</module> directives <directive
    module="mod_ldap">LDAPTrustedClientCert</directive>, <directive
    module="mod_ldap">LDAPTrustedGlobalCert</directive> and <directive
    module="mod_ldap">LDAPTrustedMode</directive>.</p>

    <p>To specify a secure LDAP server, use <em>ldaps://</em> in the
    <directive module="mod_authnz_ldap">AuthLDAPURL</directive>
    directive, instead of <em>ldap://</em>.</p>
</section>

<section id="exposed"><title>Exposing Login Information</title>

    <p>when this module performs <em>authentication</em>, ldap attributes specified
    in the <directive module="mod_authnz_ldap">authldapurl</directive> 
    directive are placed in environment variables with the prefix "AUTHENTICATE_".</p>

    <p>when this module performs <em>authorization</em>, ldap attributes specified
    in the <directive module="mod_authnz_ldap">authldapurl</directive> 
    directive are placed in environment variables with the prefix "AUTHORIZE_".</p>

    <p>If the attribute field contains the username, common name
    and telephone number of a user, a CGI program will have access to
    this information without the need to make a second independent LDAP
    query to gather this additional information.</p>

    <p>This has the potential to dramatically simplify the coding and
    configuration required in some web applications.</p>

</section>

<section id="activedirectory"><title>Using Active Directory</title>

    <p>An Active Directory installation may support multiple domains at the
    same time. To distinguish users between domains, an identifier called
    a User Principle Name (UPN) can be added to a user's entry in the
    directory. This UPN usually takes the form of the user's account
    name, followed by the domain components of the particular domain,
    for example <em>somebody@nz.example.com</em>.</p>

    <p>You may wish to configure the <module>mod_authnz_ldap</module>
    module to authenticate users present in any of the domains making up
    the Active Directory forest. In this way both
    <em>somebody@nz.example.com</em> and <em>someone@au.example.com</em>
    can be authenticated using the same query at the same time.</p>

    <p>To make this practical, Active Directory supports the concept of
    a Global Catalog. This Global Catalog is a read only copy of selected
    attributes of all the Active Directory servers within the Active
    Directory forest. Querying the Global Catalog allows all the domains
    to be queried in a single query, without the query spanning servers
    over potentially slow links.</p>

    <p>If enabled, the Global Catalog is an independent directory server
    that runs on port 3268 (3269 for SSL). To search for a user, do a
    subtree search for the attribute <em>userPrincipalName</em>, with
    an empty search root, like so:</p>

<example>
AuthLDAPBindDN apache@example.com<br />
AuthLDAPBindPassword password<br />
AuthLDAPURL ldap://10.0.0.1:3268/?userPrincipalName?sub
</example>

    <p>Users will need to enter their User Principal Name as a login, in
    the form <em>somebody@nz.example.com</em>.</p>

</section>

<section id="frontpage"><title>Using Microsoft
    FrontPage with mod_authnz_ldap</title>

    <p>Normally, FrontPage uses FrontPage-web-specific user/group
    files (i.e., the <module>mod_authn_file</module> and
    <module>mod_authz_groupfile</module> modules) 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 <em>Permissions</em> forms in
    the FrontPage client, which attempt to modify the standard
    text-based authorization files.</p>

    <p>Once a FrontPage web has been created, adding LDAP
    authentication to it is a matter of adding the following
    directives to <em>every</em> <code>.htaccess</code> file
    that gets created in the web</p>
<example><pre>
AuthLDAPURL            "the url"
AuthGroupFile <em>mygroupfile</em>
Require group <em>mygroupfile</em>
</pre></example>

<section id="howitworks"><title>How It Works</title>

    <p>FrontPage restricts access to a web by adding the <code>Require
    valid-user</code> directive to the <code>.htaccess</code>
    files. The <code>Require valid-user</code> directive will succeed for
    any user who is valid <em>as far as LDAP is
    concerned</em>. 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. By substituting the ldap-group with group file authorization,
    Apache is allowed to consult the local user file (which is managed by 
    FrontPage) - instead of LDAP - when handling authorizing the user.</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 id="fpcaveats"><title>Caveats</title>

    <ul>
      <li>When choosing the LDAP URL, the attribute to use for
      authentication should be something that will also be valid
      for putting into a <module>mod_authn_file</module> user file.
      The user ID is ideal for this.</li>

      <li>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.</li>

      <!-- XXX is that true? was mod_auth before the aaa change -->
      <li>Apache must be compiled with <module>mod_auth_basic</module>,
      <module>mod_authn_file</module> and
      <module>mod_authz_groupfile</module> in order to
      use FrontPage support. This is because Apache will still use
      the <module>mod_authz_groupfile</module> group file for determine 
      the extent of a user's access to the FrontPage web.</li>

      <li>The directives must be put in the <code>.htaccess</code>
      files. Attempting to put them inside <directive module="core"
      type="section">Location</directive> or <directive module="core"
      type="section">Directory</directive> directives won't work. This
      is because <module>mod_authnz_ldap</module> has to be able to grab
      the <directive module="mod_authn_file">AuthGroupFile</directive>
      directive that is found in FrontPage <code>.htaccess</code>
      files so that it knows where to look for the valid user list. If
      the <module>mod_authnz_ldap</module> directives aren't in the same
      <code>.htaccess</code> file as the FrontPage directives, then
      the hack won't work, because <module>mod_authnz_ldap</module> will
      never get a chance to process the <code>.htaccess</code> file,
      and won't be able to find the FrontPage-managed user file.</li>
    </ul>
</section>
</section>

<directivesynopsis>
<name>AuthLDAPAuthorizePrefix</name>
<description>Specifies the prefix for environment variables set during
authorization</description>
<syntax>AuthLDAPAuthorizePrefix <em>prefix</em></syntax>
<default>AuthLDAPAuthorizePrefix AUTHORIZE_</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<compatibility>Available in version 2.3.6 and later</compatibility>
<usage>
    <p>This directive allows you to override the prefix used for environment
    variables set during LDAP authorization.  If <em>AUTHENTICATE_</em> is
    specified, consumers of these environment variables see the same information
    whether LDAP has performed authentication, authorization, or both.</p>

    <note><title>Note</title>
    No authorization variables are set when a user is authorized on the basis of 
    <code>Require valid-user</code>.
    </note>
</usage>
</directivesynopsis>


<directivesynopsis>
<name>AuthLDAPBindAuthoritative</name>
<description>Determines if other authentication providers are used when a user can be mapped to a DN but the server cannot successfully bind with the user's credentials.</description>
<syntax>AuthLDAPBindAuthoritative<em>off|on</em></syntax>
<default>AuthLDAPBindAuthoritative on</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
    <p>By default, subsequent authentication providers are only queried if a 
    user cannot be mapped to a DN, but not if the user can be mapped to a DN and their
    password cannot be verified with an LDAP bind.  
    If <directive module="mod_authnz_ldap">AuthLDAPBindAuthoritative</directive> 
    is set to <em>off</em>, other configured authentication modules will have 
    a chance to validate the user if the LDAP bind (with the current user's credentials) 
    fails for any reason.</p>
    <p> This allows users present in both LDAP and 
    <directive module="mod_authn_file">AuthUserFile</directive> to authenticate
    when the LDAP server is available but the user's account is locked or password
    is otherwise unusable.</p>
</usage>
<seealso><directive module="mod_authn_file">AuthUserFile</directive></seealso>
<seealso><directive module="mod_auth_basic">AuthBasicProvider</directive></seealso>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPInitialBindAsUser</name>
<description>Determines if the server does the initial DN lookup using the basic authentication users'
own username, instead of anonymously or with hard-coded credentials for the server</description>
<syntax>AuthLDAPInitialBindAsUser <em>off|on</em></syntax>
<default>AuthLDAPInitialBindAsUser off</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<compatibility>Available in version 2.3.6 and later</compatibility>
<usage>
    <p>By default, the server either anonymously, or with a dedicated user and
     password, converts the basic authentication username into an LDAP
     distinguished name (DN).  This directive forces the server to use the verbatim username
     and password provided by the incoming user to perform the initial DN
     search.</p>
 
     <p> If the verbatim username can't directly bind, but needs some
     cosmetic transformation, see <directive module="mod_authnz_ldap">
     AuthLDAPInitialBindPattern</directive>.</p>
   
     <p> This directive should only be used when your LDAP server doesn't 
         accept anonymous searches and you cannot use a dedicated 
         <directive module="mod_authnz_ldap">AuthLDAPBindDN</directive>.
     </p>

     <note><title>Not available with authorization-only</title>
         This directive can only be used if this module authenticates the user, and
         has no effect when this module is used exclusively for authorization.
     </note>
</usage>
<seealso><directive module="mod_authnnz_ldap">AuthLDAPInitialBindPattern</directive></seealso>
<seealso><directive module="mod_authnnz_ldap">AuthLDAPBindDN</directive></seealso>
<seealso><directive module="mod_authnz_ldap">AuthLDAPCompareAsUser</directive></seealso>
<seealso><directive module="mod_authnz_ldap">AuthLDAPSearchAsUser</directive></seealso>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPInitialBindPattern</name>
<description>Specifies the transformation of the basic authentication username to be used when binding to the LDAP server
to perform a DN lookup</description>
<syntax>AuthLDAPInitialBindPattern<em><var>regex</var> <var>substitution</var></em></syntax>
<default>AuthLDAPInitialBindPattern (.*) $1 (remote username used verbatim)</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<compatibility>Available in version 2.3.6 and later</compatibility>
<usage>
    <p>If <directive module="mod_authnz_ldap">AuthLDAPInitialBindAsUser</directive> is set to
       <em>ON</em>, the basic authentication username will be transformed according to the
       regular expression and substituion arguments.</p>

    <p> The regular expression argument is compared against the current basic authentication username.
        The substitution argument may contain backreferences, but has no other variable interpolation.</p>
     
    <p> This directive should only be used when your LDAP server doesn't 
        accept anonymous searches and you cannot use a dedicated 
        <directive module="mod_authnz_ldap">AuthLDAPBindDN</directive>.
    </p>

    <example> AuthLDAPInitialBindPattern (.+) $1@example.com </example>
    <example> AuthLDAPInitialBindPattern (.+) cn=$1,dc=example,dc=com</example>

    <note><title>Not available with authorization-only</title>
        This directive can only be used if this module authenticates the user, and
        has no effect when this module is used exclusively for authorization.
    </note>
    <note><title>debugging</title>
        The substituted DN is recorded in the environment variable 
        <em>LDAP_BINDASUSER</em>.  If the regular expression does not match the input, 
        the verbatim username is used.
    </note>
</usage>
<seealso><directive module="mod_authnz_ldap">AuthLDAPInitialBindAsUser</directive></seealso>
<seealso><directive module="mod_authnz_ldap">AuthLDAPBindDN</directive></seealso>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPBindDN</name>
<description>Optional DN to use in binding to the LDAP server</description>
<syntax>AuthLDAPBindDN <em>distinguished-name</em></syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <p>An optional DN used to bind to the server when searching for
    entries. If not provided, <module>mod_authnz_ldap</module> will use
    an anonymous bind.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPBindPassword</name>
<description>Password used in conjuction with the bind DN</description>
<syntax>AuthLDAPBindPassword <em>password</em></syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <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 <directive
    module="mod_authnz_ldap">AuthLDAPBindDN</directive> and <directive
    module="mod_authnz_ldap">AuthLDAPBindPassword</directive> if you
    absolutely need them to search the directory.</p> 
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPCharsetConfig</name>
<description>Language to charset conversion configuration file</description>
<syntax>AuthLDAPCharsetConfig <em>file-path</em></syntax>
<contextlist><context>server config</context>
</contextlist>

<usage>
    <p>The <directive>AuthLDAPCharsetConfig</directive> directive sets the location
    of the language to charset conversion configuration file. <var>File-path</var> is relative
    to the <directive module="core">ServerRoot</directive>. This file specifies
    the list of language extensions to character sets.
    Most administrators use the provided <code>charset.conv</code>
    file, which associates common language extensions to character sets.</p>

    <p>The file contains lines in the following format:</p>

    <example>
      <var>Language-Extension</var> <var>charset</var> [<var>Language-String</var>] ...
    </example>

    <p>The case of the extension does not matter. Blank lines, and lines
    beginning with a hash character (<code>#</code>) are ignored.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPCompareAsUser</name>
<description>Use the authenticated user's credentials to perform authorization comparisons</description>
<syntax>AuthLDAPCompareAsUser on|off</syntax>
<default>AuthLDAPCompareAsUser off</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<compatibility>Available in version 2.3.6 and later</compatibility>

<usage>
    <p>When set, and <module>mod_authnz_ldap</module> has authenticated the
    user, LDAP comparisons for authorization use the queried distinguished name (DN)
    and HTTP basic authentication password of the authenticated user instead of 
    the servers configured credentials.</p>

    <p> The <em>ldap-attribute</em>, <em>ldap-user</em>, and <em>ldap-group</em> (single-level only) 
    authorization checks use comparisons.</p>

    <p>This directive only has effect on the comparisons performed during
    nested group processing when <directive module="mod_authnz_ldap">
    AuthLDAPSearchAsUser</directive> is also enabled.</p>
    
    <p> This directive should only be used when your LDAP server doesn't
        accept anonymous comparisons and you cannot use a dedicated
        <directive module="mod_authnz_ldap">AuthLDAPBindDN</directive>.
    </p>
</usage>
<seealso><directive module="mod_authnz_ldap">AuthLDAPInitialBindAsUser</directive></seealso>
<seealso><directive module="mod_authnz_ldap">AuthLDAPSearchAsUser</directive></seealso>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPCompareDNOnServer</name>
<description>Use the LDAP server to compare the DNs</description>
<syntax>AuthLDAPCompareDNOnServer on|off</syntax>
<default>AuthLDAPCompareDNOnServer on</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <p>When set, <module>mod_authnz_ldap</module> will use the LDAP
    server to compare the DNs. This is the only foolproof way to
    compare DNs.  <module>mod_authnz_ldap</module> will search the
    directory for the DN specified with the <a
    href="#reqdn"><code>Require dn</code></a> directive, then,
    retrieve the DN and compare it with the DN retrieved from the user
    entry. If this directive is not set,
    <module>mod_authnz_ldap</module> simply does a string comparison. It
    is possible to get false negatives with this approach, but it is
    much faster. Note the <module>mod_ldap</module> cache can speed up
    DN comparison in most situations.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPDereferenceAliases</name>
<description>When will the module de-reference aliases</description>
<syntax>AuthLDAPDereferenceAliases never|searching|finding|always</syntax>
<default>AuthLDAPDereferenceAliases always</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <p>This directive specifies when <module>mod_authnz_ldap</module> will
    de-reference aliases during LDAP operations. The default is
    <code>always</code>.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPGroupAttribute</name>
<description>LDAP attributes used to identify the user members of
groups.</description>
<syntax>AuthLDAPGroupAttribute <em>attribute</em></syntax>
<default>AuthLDAPGroupAttribute member uniquemember</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <p>This directive specifies which LDAP attributes are used to
    check for user members within groups. Multiple attributes can be used
    by specifying this directive multiple times. If not specified,
    then <module>mod_authnz_ldap</module> uses the <code>member</code> and
    <code>uniquemember</code> attributes.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPGroupAttributeIsDN</name>
<description>Use the DN of the client username when checking for
group membership</description>
<syntax>AuthLDAPGroupAttributeIsDN on|off</syntax>
<default>AuthLDAPGroupAttributeIsDN on</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <p>When set <code>on</code>, 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 <code>bjenson</code>,
    which corresponds to the LDAP DN <code>cn=Babs Jenson,
    o=Example</code>. If this directive is set,
    <module>mod_authnz_ldap</module> will check if the group has
    <code>cn=Babs Jenson, o=Example</code> as a member. If this
    directive is not set, then <module>mod_authnz_ldap</module> will
    check if the group has <code>bjenson</code> as a member.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPMaxSubGroupDepth</name>
<description>Specifies the maximum sub-group nesting depth that will be
evaluated before the user search is discontinued.</description>
<syntax>AuthLDAPMaxSubGroupDepth <var>Number</var></syntax>
<default>AuthLDAPMaxSubGroupDepth 10</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
   <p>When this directive is set to a non-zero value <code>X</code>
   combined with use of the <code>Require ldap-group someGroupDN</code>
   directive, the provided user credentials will be searched for
   as a member of the <code>someGroupDN</code> directory object or of
   any group member of the current group up to the maximum nesting
   level <code>X</code> specified by this directive.</p>
   <p>See the <a href="#reqgroup"><code>Require ldap-group</code></a>
   section for a more detailed example.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPRemoteUserAttribute</name>
<description>Use the value of the attribute returned during the user
query to set the REMOTE_USER environment variable</description>
<syntax>AuthLDAPRemoteUserAttribute uid</syntax>
<default>none</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override> 
      
<usage>
    <p>If this directive is set, the value of the 
    <code>REMOTE_USER</code> environment variable will be set to the
    value of the attribute specified. Make sure that this attribute is
    included in the list of attributes in the AuthLDAPUrl definition,
    otherwise this directive will have no effect. This directive, if
    present, takes precedence over AuthLDAPRemoteUserIsDN. This
    directive is useful should you want people to log into a website
    using an email address, but a backend application expects the
    username as a userid.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPRemoteUserIsDN</name>
<description>Use the DN of the client username to set the REMOTE_USER
environment variable</description>
<syntax>AuthLDAPRemoteUserIsDN on|off</syntax>
<default>AuthLDAPRemoteUserIsDN off</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <p>If this directive is set to on, the value of the
    <code>REMOTE_USER</code> 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.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPSearchAsUser</name>
<description>Use the authenticated user's credentials to perform authorization searches</description>
<syntax>AuthLDAPSearchAsUser on|off</syntax>
<default>AuthLDAPSearchAsUser off</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<compatibility>Available in version 2.3.6 and later</compatibility>

<usage>
    <p>When set, and <module>mod_authnz_ldap</module> has authenticated the
    user, LDAP searches for authorization use the queried distinguished name (DN)
    and HTTP basic authentication password of the authenticated user instead of 
    the servers configured credentials.</p>

    <p> The <em>ldap-filter</em> and <em>ldap-dn</em> authorization 
    checks use searches.</p>

    <p>This directive only has effect on the comparisons performed during
    nested group processing when <directive module="mod_authnz_ldap">
    AuthLDAPCompareAsUser</directive> is also enabled.</p>

    <p> This directive should only be used when your LDAP server doesn't
        accept anonymous searches and you cannot use a dedicated
        <directive module="mod_authnz_ldap">AuthLDAPBindDN</directive>.
    </p>
</usage>
<seealso><directive module="mod_authnz_ldap">AuthLDAPInitialBindAsUser</directive></seealso>
<seealso><directive module="mod_authnz_ldap">AuthLDAPCompareAsUser</directive></seealso>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPSubGroupAttribute</name>
<description>Specifies the attribute labels, one value per
directive line, used to distinguish the members of the current group that
are groups.</description>
<syntax>AuthLDAPSubGroupAttribute <em>attribute</em></syntax>
<default>AuthLDAPSubgroupAttribute member uniquemember</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <p>An LDAP group object may contain members that are users and
    members that are groups (called nested or sub groups). The
    <code>AuthLDAPSubGroupAttribute</code> directive identifies the
    labels of group members and the <code>AuthLDAPGroupAttribute</code>
    directive identifies the labels of the user members. Multiple
    attributes can be used by specifying this directive multiple times.
    If not specified, then <module>mod_authnz_ldap</module> uses the
    <code>member</code> and <code>uniqueMember</code> attributes.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPSubGroupClass</name>
<description>Specifies which LDAP objectClass values identify directory
objects that are groups during sub-group processing.</description>
<syntax>AuthLDAPSubGroupClass <em>LdapObjectClass</em></syntax>
<default>AuthLDAPSubGroupClass groupOfNames groupOfUniqueNames</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <p>An LDAP group object may contain members that are users and
    members that are groups (called nested or sub groups). The
    <code>AuthLDAPSubGroupAttribute</code> directive identifies the
    labels of members that may be sub-groups of the current group
    (as opposed to user members). The <code>AuthLDAPSubGroupClass</code>
    directive specifies the LDAP objectClass values used in verifying that
    these potential sub-groups are in fact group objects. Verified sub-groups
    can then be searched for more user or sub-group members. Multiple
    attributes can be used by specifying this directive multiple times.
    If not specified, then <module>mod_authnz_ldap</module> uses the
    <code>groupOfNames</code> and <code>groupOfUniqueNames</code> values.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthLDAPUrl</name>
<description>URL specifying the LDAP search parameters</description>
<syntax>AuthLDAPUrl <em>url [NONE|SSL|TLS|STARTTLS]</em></syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>

<usage>
    <p>An RFC 2255 URL which specifies the LDAP search parameters
    to use. The syntax of the URL is</p>
<example>ldap://host:port/basedn?attribute?scope?filter</example>
    <p>If you want to specify more than one LDAP URL that Apache should try in turn, the syntax is:</p>
<example>AuthLDAPUrl "ldap://ldap1.example.com ldap2.example.com/dc=..."</example>
<p><em><strong>Caveat: </strong>If you specify multiple servers, you need to enclose the entire URL string in quotes; 
otherwise you will get an error: "AuthLDAPURL takes one argument, URL to define LDAP connection.." </em> 
You can of course use search parameters on each of these.</p>

<dl>
<dt>ldap</dt>

        <dd>For regular ldap, use the
        string <code>ldap</code>. For secure LDAP, use <code>ldaps</code>
        instead. Secure LDAP is only available if Apache was linked
        to an LDAP library with SSL support.</dd>

<dt>host:port</dt>

        <dd>
          <p>The name/port of the ldap server (defaults to
          <code>localhost:389</code> for <code>ldap</code>, and
          <code>localhost:636</code> for <code>ldaps</code>). To
          specify multiple, redundant LDAP servers, just list all
          servers, separated by spaces. <module>mod_authnz_ldap</module>
          will try connecting to each server in turn, until it makes a
          successful connection. If multiple ldap servers are specified, 
          then entire LDAP URL must be encapsulated in double quotes.</p>

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

          <p>If the LDAP server goes down and breaks an existing
          connection, <module>mod_authnz_ldap</module> 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>
        </dd>

<dt>basedn</dt>

        <dd>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.</dd>

<dt>attribute</dt>

        <dd>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 <code>uid</code>. It's a good
        idea to choose an attribute that will be unique across all
        entries in the subtree you will be using.  All attributes
        listed will be put into the environment with an AUTHENTICATE_ prefix
        for use by other modules.</dd>

<dt>scope</dt>

        <dd>The scope of the search. Can be either <code>one</code> or
        <code>sub</code>. Note that a scope of <code>base</code> is
        also supported by RFC 2255, but is not supported by this
        module. If the scope is not provided, or if <code>base</code> scope
        is specified, the default is to use a scope of
        <code>sub</code>.</dd>

<dt>filter</dt>

        <dd>A valid LDAP search filter. If
        not provided, defaults to <code>(objectClass=*)</code>, which
        will search for all objects in the tree. Filters are
        limited to approximately 8000 characters (the definition of
        <code>MAX_STRING_LEN</code> in the Apache source code). This
        should be more than sufficient for any application.</dd>
</dl>

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

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

    <p>An optional parameter can be added to allow the LDAP Url to override 
    the connection type.  This parameter can be one of the following:</p>

<dl>
    <dt>NONE</dt>
        <dd>Establish an unsecure connection on the default LDAP port. This
        is the same as <code>ldap://</code> on port 389.</dd>
    <dt>SSL</dt>
        <dd>Establish a secure connection on the default secure LDAP port.
        This is the same as <code>ldaps://</code></dd>
    <dt>TLS | STARTTLS</dt>
        <dd>Establish an upgraded secure connection on the default LDAP port.
        This connection will be initiated on port 389 by default and then 
        upgraded to a secure connection on the same port.</dd>
</dl>

    <p>See above for examples of <directive
    module="mod_authnz_ldap">AuthLDAPURL</directive> URLs.</p>
</usage>
</directivesynopsis>

</modulesynopsis>