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

<name>mod_authn_dbd</name>
<description>User authentication using an SQL database</description>
<status>Extension</status>
<sourcefile>mod_authn_dbd.c</sourcefile>
<identifier>authn_dbd_module</identifier>
<compatibility>Available in Apache 2.1 and later</compatibility>

<summary>
    <p>This module provides authentication front-ends such as
    <module>mod_auth_digest</module> and <module>mod_auth_basic</module>
    to authenticate users by looking up users in SQL tables.
    Similar functionality is provided by, for example,
    <module>mod_authn_file</module>.</p>
    <p>This module relies on <module>mod_dbd</module> to specify
    the backend database driver and connection parameters, and
    manage the database connections.</p>

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

<seealso><directive module="mod_authn_core">AuthName</directive></seealso>
<seealso><directive module="mod_authn_core">AuthType</directive></seealso>
<seealso>
  <directive module="mod_auth_basic">AuthBasicProvider</directive>
</seealso>
<seealso>
  <directive module="mod_auth_digest">AuthDigestProvider</directive>
</seealso>
<seealso><directive module="mod_dbd">DBDriver</directive></seealso>
<seealso><directive module="mod_dbd">DBDParams</directive></seealso>
<seealso><a href="../misc/password_encryptions.html">Password Formats</a></seealso>

<section id="socache">
<title>Performance and Cacheing</title>
<p>Some users of DBD authentication in HTTPD 2.2/2.4 have reported that it
imposes a problematic load on the database.  This is most likely where
an HTML page contains hundreds of objects (e.g. images, scripts, etc)
each of which requires authentication.  Users affected (or concerned)
by this kind of problem should use <module>mod_authn_socache</module>
to cache credentials and take most of the load off the database.</p>
</section>

<section id="example">
<title>Configuration Example</title>
<p>This simple example shows use of this module in the context of
the Authentication and DBD frameworks.</p>
<highlight language="config">
# mod_dbd configuration
# UPDATED to include authentication cacheing
DBDriver pgsql
DBDParams "dbname=apacheauth user=apache password=xxxxxx"

DBDMin  4
DBDKeep 8
DBDMax  20
DBDExptime 300

&lt;Directory /usr/www/myhost/private&gt;
  # mod_authn_core and mod_auth_basic configuration
  # for mod_authn_dbd
  AuthType Basic
  AuthName "My Server"

  # To cache credentials, put socache ahead of dbd here
  AuthBasicProvider socache dbd

  # Also required for caching: tell the cache to cache dbd lookups!
  AuthnCacheProvideFor dbd
  AuthnCacheContext my-server

  # mod_authz_core configuration
  Require valid-user

  # mod_authn_dbd SQL query to authenticate a user
  AuthDBDUserPWQuery "SELECT password FROM authn WHERE user = %s"
&lt;/Directory&gt;
</highlight>
</section>

<section id="exposed">
<title>Exposing Login Information</title>
<p>
If httpd was built against <glossary>APR</glossary> version 1.3.0
or higher, then whenever a query is made to the database server, all
column values in the first row returned by the query are placed in the
environment, using environment variables with the prefix "AUTHENTICATE_".
</p>
<p>If a database query for example returned the username, full name
and telephone number of a user, a CGI program will have access to
this information without the need to make a second independent database
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>

<directivesynopsis>
<name>AuthDBDUserPWQuery</name>
<description>SQL query to look up a password for a user</description>
<syntax>AuthDBDUserPWQuery <var>query</var></syntax>
<contextlist><context>directory</context>
</contextlist>

<usage>
    <p>The <directive>AuthDBDUserPWQuery</directive> specifies an
    SQL query to look up a password for a specified user.  The user's ID
    will be passed as a single string parameter when the SQL query is
    executed.  It may be referenced within the query statement using
    a <code>%s</code> format specifier.</p>
    <highlight language="config">
AuthDBDUserPWQuery "SELECT password FROM authn WHERE user = %s"
</highlight>
    <p>The first column value of the first row returned by the query
    statement should be a string containing the encrypted password.
    Subsequent rows will be ignored.  If no rows are returned, the user
    will not be authenticated through <module>mod_authn_dbd</module>.</p>
    <p>If httpd was built against <glossary>APR</glossary> version 1.3.0
    or higher, any additional column values in the first row returned by
    the query statement will be stored as environment variables with
    names of the form <code>AUTHENTICATE_<var>COLUMN</var></code>.
    </p>
    <p>The encrypted password format depends on which authentication
    frontend (e.g. <module>mod_auth_basic</module> or
    <module>mod_auth_digest</module>) is being used.  See <a
    href="../misc/password_encryptions.html">Password Formats</a> for
    more information.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthDBDUserRealmQuery</name>
<description>SQL query to look up a password hash for a user and realm.
</description>
<syntax>AuthDBDUserRealmQuery <var>query</var></syntax>
<contextlist><context>directory</context>
</contextlist>

<usage>
    <p>The <directive>AuthDBDUserRealmQuery</directive> specifies an
    SQL query to look up a password for a specified user and realm in a 
    digest authentication process.
    The user's ID and the realm, in that order, will be passed as string
    parameters when the SQL query is executed.  They may be referenced
    within the query statement using <code>%s</code> format specifiers.</p>
    <highlight language="config">
AuthDBDUserRealmQuery "SELECT password FROM authn WHERE user = %s AND realm = %s"
</highlight>
    <p>The first column value of the first row returned by the query
    statement should be a string containing the encrypted password.
    Subsequent rows will be ignored.  If no rows are returned, the user
    will not be authenticated through <module>mod_authn_dbd</module>.</p>
    <p>If httpd was built against <glossary>APR</glossary> version 1.3.0
    or higher, any additional column values in the first row returned by
    the query statement will be stored as environment variables with
    names of the form <code>AUTHENTICATE_<var>COLUMN</var></code>.
    </p>
    <p>The encrypted password format depends on which authentication
    frontend (e.g. <module>mod_auth_basic</module> or
    <module>mod_auth_digest</module>) is being used.  See <a
    href="../misc/password_encryptions.html">Password Formats</a> for
    more information.</p>
</usage>
</directivesynopsis>

</modulesynopsis>
