2.4.x/docs/manual/mod/mod_session_dbd.xml

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

<name>mod_session_dbd</name>
<description>DBD/SQL based session support</description>
<status>Extension</status>
<sourcefile>mod_session_dbd.c</sourcefile>
<identifier>session_dbd_module</identifier>
<compatibility>Available in Apache 2.3 and later</compatibility>

<summary>
    <note type="warning"><title>Warning</title>
      <p>The session modules make use of HTTP cookies, and as such can fall
      victim to Cross Site Scripting attacks, or expose potentially private
      information to clients. Please ensure that the relevant risks have
      been taken into account before enabling the session functionality on
      your server.</p>
    </note>

    <p>This submodule of <module>mod_session</module> provides support for the
    storage of user sessions within a SQL database using the
    <module>mod_dbd</module> module.</p>

    <p>Sessions can either be <strong>anonymous</strong>, where the session is
    keyed by a unique UUID string stored on the browser in a cookie, or
    <strong>per user</strong>, where the session is keyed against the userid of
    the logged in user.</p>

    <p>SQL based sessions are hidden from the browser, and so offer a measure of
    privacy without the need for encryption.</p>

    <p>Different webservers within a server farm may choose to share a database,
    and so share sessions with one another.</p>

    <p>For more details on the session interface, see the documentation for
    the <module>mod_session</module> module.</p>

</summary>
<seealso><module>mod_session</module></seealso>
<seealso><module>mod_session_crypto</module></seealso>
<seealso><module>mod_session_cookie</module></seealso>
<seealso><module>mod_dbd</module></seealso>

    <section id="dbdconfig"><title>DBD Configuration</title>

      <p>Before the <module>mod_session_dbd</module> module can be configured to maintain a
      session, the <module>mod_dbd</module> module must be configured to make the various database queries
      available to the server.</p>

      <p>There are four queries required to keep a session maintained, to select an existing session,
      to update an existing session, to insert a new session, and to delete an expired or empty
      session. These queries are configured as per the example below.</p>

      <example><title>Sample DBD configuration</title>
      <highlight language="config">
DBDriver pgsql
DBDParams "dbname=apachesession user=apache password=xxxxx host=localhost"
DBDPrepareSQL "delete from session where key = %s" deletesession
DBDPrepareSQL "update session set value = %s, expiry = %lld, key = %s where key = %s" updatesession
DBDPrepareSQL "insert into session (value, expiry, key) values (%s, %lld, %s)" insertsession
DBDPrepareSQL "select value from session where key = %s and (expiry = 0 or expiry &gt; %lld)" selectsession
DBDPrepareSQL "delete from session where expiry != 0 and expiry &lt; %lld" cleansession
    </highlight>
      </example>

    </section>

    <section id="anonymous"><title>Anonymous Sessions</title>

      <p>Anonymous sessions are keyed against a unique UUID, and stored on the
      browser within an HTTP cookie. This method is similar to that used by most
      application servers to store session information.</p>

      <p>To create a simple anonymous session and store it in a postgres database
      table called <var>apachesession</var>, and save the session ID in a cookie
      called <var>session</var>, configure the session as follows:</p>

      <example><title>SQL based anonymous session</title>
      <highlight language="config">
Session On
SessionDBDCookieName session path=/
        </highlight>
      </example>

      <p>For more examples on how the session can be configured to be read
      from and written to by a CGI application, see the
      <module>mod_session</module> examples section.</p>

      <p>For documentation on how the session can be used to store username
      and password details, see the <module>mod_auth_form</module> module.</p>

    </section>

    <section id="peruser"><title>Per User Sessions</title>

      <p>Per user sessions are keyed against the username of a successfully
      authenticated user. It offers the most privacy, as no external handle
      to the session exists outside of the authenticated realm.</p>

      <p>Per user sessions work within a correctly configured authenticated
      environment, be that using basic authentication, digest authentication
      or SSL client certificates. Due to the limitations of who came first,
      the chicken or the egg, per user sessions cannot be used to store
      authentication credentials from a module like
      <module>mod_auth_form</module>.</p>

      <p>To create a simple per user session and store it in a postgres database
      table called <var>apachesession</var>, and with the session keyed to the
      userid, configure the session as follows:</p>

      <example><title>SQL based per user session</title>
      <highlight language="config">
Session On
SessionDBDPerUser On
        </highlight>
      </example>

    </section>

    <section id="housekeeping"><title>Database Housekeeping</title>
      <p>Over the course of time, the database can be expected to start accumulating
      expired sessions. At this point, the <module>mod_session_dbd</module> module
      is not yet able to handle session expiry automatically.</p>

      <note type="warning"><title>Warning</title>
      <p>The administrator will need to set up an external process via cron to clean
      out expired sessions.</p>
      </note>

    </section>

<directivesynopsis>
<name>SessionDBDCookieName</name>
<description>Name and attributes for the RFC2109 cookie storing the session ID</description>
<syntax>SessionDBDCookieName <var>name</var> <var>attributes</var></syntax>
<default>none</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
<context>.htaccess</context>
</contextlist>

<usage>
    <p>The <directive>SessionDBDCookieName</directive> directive specifies the name and
    optional attributes of an RFC2109 compliant cookie inside which the session ID will
    be stored. RFC2109 cookies are set using the <code>Set-Cookie</code> HTTP header.
    </p>

    <p>An optional list of cookie attributes can be specified, as per the example below.
    These attributes are inserted into the cookie as is, and are not interpreted by
    Apache. Ensure that your attributes are defined correctly as per the cookie specification.
    </p>

    <example><title>Cookie with attributes</title>
    <highlight language="config">
Session On
SessionDBDCookieName session path=/private;domain=example.com;httponly;secure;version=1;
      </highlight>
    </example>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>SessionDBDCookieName2</name>
<description>Name and attributes for the RFC2965 cookie storing the session ID</description>
<syntax>SessionDBDCookieName2 <var>name</var> <var>attributes</var></syntax>
<default>none</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
<context>.htaccess</context>
</contextlist>

<usage>
    <p>The <directive>SessionDBDCookieName2</directive> directive specifies the name and
    optional attributes of an RFC2965 compliant cookie inside which the session ID will
    be stored. RFC2965 cookies are set using the <code>Set-Cookie2</code> HTTP header.
    </p>

    <p>An optional list of cookie attributes can be specified, as per the example below.
    These attributes are inserted into the cookie as is, and are not interpreted by
    Apache. Ensure that your attributes are defined correctly as per the cookie specification.
    </p>

    <example><title>Cookie2 with attributes</title>
    <highlight language="config">
Session On
SessionDBDCookieName2 session path=/private;domain=example.com;httponly;secure;version=1;
      </highlight>
    </example>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>SessionDBDCookieRemove</name>
<description>Control for whether session ID cookies should be removed from incoming HTTP headers</description>
<syntax>SessionDBDCookieRemove On|Off</syntax>
<default>SessionDBDCookieRemove On</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
<context>.htaccess</context>
</contextlist>

<usage>
    <p>The <directive>SessionDBDCookieRemove</directive> flag controls whether the cookies
    containing the session ID will be removed from the headers during request processing.</p>

    <p>In a reverse proxy situation where the Apache server acts as a server frontend for
    a backend origin server, revealing the contents of the session ID cookie to the backend
    could be a potential privacy violation. When set to on, the session ID cookie will be
    removed from the incoming HTTP headers.</p>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>SessionDBDPerUser</name>
<description>Enable a per user session</description>
<syntax>SessionDBDPerUser On|Off</syntax>
<default>SessionDBDPerUser Off</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
<context>.htaccess</context>
</contextlist>

<usage>
    <p>The <directive>SessionDBDPerUser</directive> flag enables a per user session keyed
    against the user's login name. If the user is not logged in, this directive will be
    ignored.</p>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>SessionDBDSelectLabel</name>
<description>The SQL query to use to select sessions from the database</description>
<syntax>SessionDBDSelectLabel <var>label</var></syntax>
<default>SessionDBDSelectLabel selectsession</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
<context>.htaccess</context>
</contextlist>

<usage>
    <p>The <directive>SessionDBDSelectLabel</directive> directive sets the default select
    query label to be used to load in a session. This label must have been previously defined using the
    <directive module="mod_dbd">DBDPrepareSQL</directive> directive.</p>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>SessionDBDInsertLabel</name>
<description>The SQL query to use to insert sessions into the database</description>
<syntax>SessionDBDInsertLabel <var>label</var></syntax>
<default>SessionDBDInsertLabel insertsession</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
<context>.htaccess</context>
</contextlist>

<usage>
    <p>The <directive>SessionDBDInsertLabel</directive> directive sets the default insert
    query label to be used to load in a session. This label must have been previously defined using the
    <directive module="mod_dbd">DBDPrepareSQL</directive> directive.</p>

    <p>If an attempt to update the session affects no rows, this query will be called to insert the
    session into the database.</p>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>SessionDBDUpdateLabel</name>
<description>The SQL query to use to update existing sessions in the database</description>
<syntax>SessionDBDUpdateLabel <var>label</var></syntax>
<default>SessionDBDUpdateLabel updatesession</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
<context>.htaccess</context>
</contextlist>

<usage>
    <p>The <directive>SessionDBDUpdateLabel</directive> directive sets the default update
    query label to be used to load in a session. This label must have been previously defined using the
    <directive module="mod_dbd">DBDPrepareSQL</directive> directive.</p>

    <p>If an attempt to update the session affects no rows, the insert query will be
    called to insert the session into the database. If the database supports InsertOrUpdate,
    override this query to perform the update in one query instead of two.</p>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>SessionDBDDeleteLabel</name>
<description>The SQL query to use to remove sessions from the database</description>
<syntax>SessionDBDDeleteLabel <var>label</var></syntax>
<default>SessionDBDDeleteLabel deletesession</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
<context>.htaccess</context>
</contextlist>

<usage>
    <p>The <directive>SessionDBDDeleteLabel</directive> directive sets the default delete
    query label to be used to delete an expired or empty session. This label must have been previously
    defined using the <directive module="mod_dbd">DBDPrepareSQL</directive> directive.</p>

</usage>
</directivesynopsis>

</modulesynopsis>