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<title>mod_session - Apache HTTP Server</title>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.5</a> > <a href="./">Modules</a></div>
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<div id="preamble"><h1>Apache Module mod_session</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="/en/mod/mod_session.html" title="English"> en </a></p>
</div>
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Session support</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>session_module</td></tr>
<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.3 and later</td></tr></table>
<h3>Summary</h3>
<div class="warning"><h3>Warning</h3>
<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>
</div>
<p>This module provides support for a server wide per user session
interface. Sessions can be used for keeping track of whether a user
has been logged in, or for other per user information that should
be kept available across requests.</p>
<p>Sessions may be stored on the server, or may be stored on the
browser. Sessions may also be optionally encrypted for added security.
These features are divided into several modules in addition to
<code class="module"><a href="/mod/mod_session.html">mod_session</a></code>; <code class="module"><a href="/mod/mod_session_crypto.html">mod_session_crypto</a></code>,
<code class="module"><a href="/mod/mod_session_cookie.html">mod_session_cookie</a></code> and <code class="module"><a href="/mod/mod_session_dbd.html">mod_session_dbd</a></code>.
Depending on the server requirements, load the appropriate modules
into the server (either statically at compile time or dynamically
via the <code class="directive"><a href="/mod/mod_so.html#loadmodule">LoadModule</a></code> directive).</p>
<p>Sessions may be manipulated from other modules that depend on the
session, or the session may be read from and written to using
environment variables and HTTP headers, as appropriate.</p>
</div>
<div id="quickview"><h3 class="directives">Directives</h3>
<ul id="toc">
</ul>
<h3>Topics</h3>
<ul id="topics">
<li><img alt="" src="/images/down.gif" /> <a href="#whocanuseasession">Who can use a session?</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#serversession">Keeping sessions on the server</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#browsersession">Keeping sessions on the browser</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#authentication">Session Support for Authentication</a></li>
</ul><h3>See also</h3>
<ul class="seealso">
</ul></div>
<div class="section">
<h2><a name="whatisasession" id="whatisasession">What is a session?</a></h2>
<p>At the core of the session interface is a table of key and value pairs
that are made accessible across browser requests.</p>
<p>These pairs can be set to any valid string, as needed by the
application making use of the session.</p>
<div class="section">
<h2><a name="whocanuseasession" id="whocanuseasession">Who can use a session?</a></h2>
<p>The session interface is primarily developed for the use by other
server modules, such as <code class="module"><a href="/mod/mod_auth_form.html">mod_auth_form</a></code>, however CGI
based applications can optionally be granted access to the contents
of the session via the HTTP_SESSION environment variable. Sessions
response header containing the new session parameters.</p>
<div class="section">
<h2><a name="serversession" id="serversession">Keeping sessions on the server</a></h2>
<p>Apache can be configured to keep track of per user sessions stored
on a particular server or group of servers. This functionality is
similar to the sessions available in typical application servers.</p>
<p>If configured, sessions are tracked through the use of a session ID that
is stored inside a cookie, or extracted from the parameters embedded
within the URL query string, as found in a typical GET request.</p>
<p>As the contents of the session are stored exclusively on the server,
there is an expectation of privacy of the contents of the session. This
does have performance and resource implications should a large number
of sessions be present, or where a large number of webservers have to
share sessions with one another.</p>
<p>The <code class="module"><a href="/mod/mod_session_dbd.html">mod_session_dbd</a></code> module allows the storage of user
sessions within a SQL database via <code class="module"><a href="/mod/mod_dbd.html">mod_dbd</a></code>.</p>
<div class="section">
<h2><a name="browsersession" id="browsersession">Keeping sessions on the browser</a></h2>
<p>Where keeping track of a session on a server is too resource
intensive or inconvenient, the option exists to store the contents
of the session within a cookie on the client browser instead.</p>
<p>This has the advantage that minimal resources are required on the
server to keep track of sessions, and multiple servers within a server
farm have no need to share session information.</p>
<p>The contents of the session however are exposed to the client, with a
corresponding risk of a loss of privacy. The
<code class="module"><a href="/mod/mod_session_crypto.html">mod_session_crypto</a></code> module can be configured to encrypt the
contents of the session before writing the session to the client.</p>
<p>The <code class="module"><a href="/mod/mod_session_cookie.html">mod_session_cookie</a></code> allows the storage of user
sessions on the browser within an HTTP cookie.</p>
<div class="section">
<h2><a name="basicexamples" id="basicexamples">Basic Examples</a></h2>
<p>Creating a session is as simple as turning the session on, and deciding
where the session will be stored. In this example, the session will be
stored on the browser, in a cookie called <code>session</code>.</p>
<div class="example"><h3>Browser based session</h3><p><code>
Session On<br />
SessionCookieName session path=/<br />
</code></p></div>
<p>The session is not useful unless it can be written to or read from. The
following example shows how values can be injected into the session through
the use of a predetermined HTTP response header called
<code>X-Replace-Session</code>.</p>
<div class="example"><h3>Writing to a session</h3><p><code>
Session On<br />
SessionCookieName session path=/<br />
SessionHeader X-Replace-Session<br />
</code></p></div>
<p>The header should contain name value pairs expressed in the same format
as a query string in a URL, as in the example below. Setting a key to the
empty string has the effect of removing that key from the session.</p>
<div class="example"><h3>CGI to write to a session</h3><p><code>
echo "X-Replace-Session: key1=foo&key2=&key3=bar"<br />
echo<br />
env<br />
</code></p></div>
<p>If configured, the session can be read back from the HTTP_SESSION
environment variable. By default, the session is kept private, so this
has to be explicitly turned on with the
<code class="directive"><a href="#sessionenv">SessionEnv</a></code> directive.</p>
<div class="example"><h3>Read from a session</h3><p><code>
Session On<br />
SessionEnv On<br />
SessionCookieName session path=/<br />
SessionHeader X-Replace-Session<br />
</code></p></div>
<p>Once read, the CGI variable <code>HTTP_SESSION</code> should contain
the value <code>key1=foo&key3=bar</code>.</p>
<div class="section">
<h2><a name="sessionprivacy" id="sessionprivacy">Session Privacy</a></h2>
<p>Using the "show cookies" feature of your browser, you would have seen
a clear text representation of the session. This could potentially be a
problem should the end user need to be kept unaware of the contents of
the session, or where a third party could gain unauthorised access to the
data within the session.</p>
<p>The contents of the session can be optionally encrypted before being
placed on the browser using the <code class="module"><a href="/mod/mod_session_crypto.html">mod_session_crypto</a></code>
module.</p>
<div class="example"><h3>Browser based encrypted session</h3><p><code>
Session On<br />
SessionCryptoPassphrase secret<br />
SessionCookieName session path=/<br />
</code></p></div>
<p>The session will be automatically decrypted on load, and encrypted on
save by Apache, the underlying application using the session need have
no knowledge that encryption is taking place.</p>
<p>Sessions stored on the server rather than on the browser can also be
encrypted as needed, offering privacy where potentially sensitive
information is being shared between webservers in a server farm using
<div class="section">
<h2><a name="cookieprivacy" id="cookieprivacy">Cookie Privacy</a></h2>
<p>The HTTP cookie mechanism also offers privacy features, such as the
ability to restrict cookie transport to SSL protected pages only, or
to prevent browser based javascript from gaining access to the contents
of the cookie.</p>
<div class="warning"><h3>Warning</h3>
<p>Some of the HTTP cookie privacy features are either non-standard, or
are not implemented consistently across browsers. The session modules
allow you to set cookie parameters, but it makes no guarantee that privacy
will be respected by the browser. If security is a concern, use the
<code class="module"><a href="/mod/mod_session_crypto.html">mod_session_crypto</a></code> to encrypt the contents of the session,
or store the session on the server using the <code class="module"><a href="/mod/mod_session_dbd.html">mod_session_dbd</a></code>
module.</p>
</div>
<p>Standard cookie parameters can be specified after the name of the cookie,
as in the example below.</p>
<div class="example"><h3>Setting cookie parameters</h3><p><code>
Session On<br />
SessionCryptoPassphrase secret<br />
SessionCookieName session path=/private;domain=example.com;httponly;secure;<br />
</code></p></div>
<p>In cases where the Apache server forms the frontend for backend origin servers,
it is possible to have the session cookies removed from the incoming HTTP headers using
the <code class="directive"><a href="/mod/mod_session_cookie.html#sessioncookieremove">SessionCookieRemove</a></code> directive.
This keeps the contents of the session cookies from becoming accessible from the
backend server.
</p>
<div class="section">
<h2><a name="authentication" id="authentication">Session Support for Authentication</a></h2>
<p>As is possible within many application servers, authentication modules can use
a session for storing the username and password after login. The
<code class="module"><a href="/mod/mod_auth_form.html">mod_auth_form</a></code> saves the user's login name and password within
the session.</p>
<div class="example"><h3>Form based authentication</h3><p><code>
Session On<br />
SessionCryptoPassphrase secret<br />
SessionCookieName session path=/<br />
AuthFormProvider file<br />
AuthType form<br />
AuthName realm<br />
...<br />
</code></p></div>
<p>See the <code class="module"><a href="/mod/mod_auth_form.html">mod_auth_form</a></code> module for documentation and complete
examples.</p>
</div>
<div class="directive-section"><h2><a name="Session" id="Session">Session</a> <a name="session" id="session">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables a session for the current directory or location</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Session On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Session Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive">Session</code> directive enables a session for the
directory or location container. Further directives control where the
session will be stored and how privacy is maintained.</p>
</div>
<div class="directive-section"><h2><a name="SessionEnv" id="SessionEnv">SessionEnv</a> <a name="sessionenv" id="sessionenv">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Control whether the contents of the session are written to the
<var>HTTP_SESSION</var> environment variable</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SessionEnv On|Off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SessionEnv Off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>If set to <var>On</var>, the <code class="directive">SessionEnv</code> directive
causes the contents of the session to be written to a CGI environment
variable called <var>HTTP_SESSION</var>.</p>
<p>The string is written in the URL query format, for example:</p>
<div class="example"><p><code>
<code>key1=foo&key3=bar</code>
</code></p></div>
</div>
<div class="directive-section"><h2><a name="SessionExclude" id="SessionExclude">SessionExclude</a> <a name="sessionexclude" id="sessionexclude">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Define URL prefixes for which a session is ignored</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SessionExclude <var>path</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive">SessionExclude</code> directive allows sessions to
be disabled relative to URL prefixes only. This can be used to make a
website more efficient, by targeting a more precise URL space for which
a session should be maintained. By default, all URLs within the directory
or location are included in the session. The
<code class="directive"><a href="#sessionexclude">SessionExclude</a></code> directive takes
precedence over the
<code class="directive"><a href="#sessioninclude">SessionInclude</a></code> directive.</p>
<div class="warning"><h3>Warning</h3>
<p>This directive has a similar purpose to the <var>path</var> attribute
in HTTP cookies, but should not be confused with this attribute. This
directive does not set the <var>path</var> attribute, which must be
configured separately.</p></div>
</div>
<div class="directive-section"><h2><a name="SessionHeader" id="SessionHeader">SessionHeader</a> <a name="sessionheader" id="sessionheader">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Import session updates from a given HTTP response header</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SessionHeader <var>header</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive">SessionHeader</code> directive defines the name of an
HTTP response header which, if present, will be parsed and written to the
current session.</p>
<p>The header value is expected to be in the URL query format, for example:</p>
<div class="example"><p><code>
<code>key1=foo&key2=&key3=bar</code>
</code></p></div>
<p>Where a key is set to the empty string, that key will be removed from the
session.</p>
</div>
<div class="directive-section"><h2><a name="SessionInclude" id="SessionInclude">SessionInclude</a> <a name="sessioninclude" id="sessioninclude">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Define URL prefixes for which a session is valid</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SessionInclude <var>path</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive">SessionInclude</code> directive allows sessions to
be made valid for specific URL prefixes only. This can be used to make a
website more efficient, by targeting a more precise URL space for which
a session should be maintained. By default, all URLs within the directory
or location are included in the session.</p>
<div class="warning"><h3>Warning</h3>
<p>This directive has a similar purpose to the <var>path</var> attribute
in HTTP cookies, but should not be confused with this attribute. This
directive does not set the <var>path</var> attribute, which must be
configured separately.</p></div>
</div>
<div class="directive-section"><h2><a name="SessionMaxAge" id="SessionMaxAge">SessionMaxAge</a> <a name="sessionmaxage" id="sessionmaxage">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Define a maximum age in seconds for a session</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SessionMaxAge <var>maxage</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SessionMaxAge 0</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
</table>
<p>The <code class="directive">SessionMaxAge</code> directive defines a time limit
for which a session will remain valid. When a session is saved, this time
limit is reset and an existing session can be continued. If a session
becomes older than this limit without a request to the server to refresh
the session, the session will time out and be removed. Where a session is
used to stored user login details, this has the effect of logging the user
out automatically after the given time.</p>
<p>Setting the maxage to zero disables session expiry.</p>
</div>
</div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="/en/mod/mod_session.html" title="English"> en </a></p>
</div><div id="footer">
<p class="apache">Copyright 2011 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
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