mod_session.xml revision ab152dac543de24fadd7ed0159c9f380af02061b
c3fcea07965f59723831e23da647a77518285b8eslive<!DOCTYPE modulesynopsis SYSTEM "/style/modulesynopsis.dtd">
e942c741056732f50da2074b36fe59805d370650slive<?xml-stylesheet type="text/xsl" href="/style/manual.en.xsl"?>
5f5d1b4cc970b7f06ff8ef6526128e9a27303d88nd<!-- $LastChangedRevision$ -->
db479b48bd4d75423ed4a45e15b75089d1a8ad72fielding Licensed to the Apache Software Foundation (ASF) under one or more
db479b48bd4d75423ed4a45e15b75089d1a8ad72fielding contributor license agreements. See the NOTICE file distributed with
db479b48bd4d75423ed4a45e15b75089d1a8ad72fielding this work for additional information regarding copyright ownership.
db479b48bd4d75423ed4a45e15b75089d1a8ad72fielding The ASF licenses this file to You under the Apache License, Version 2.0
db479b48bd4d75423ed4a45e15b75089d1a8ad72fielding (the "License"); you may not use this file except in compliance with
db479b48bd4d75423ed4a45e15b75089d1a8ad72fielding the License. You may obtain a copy of the License at
d5d794fc2f4cc9ca6d6da17cfa2cdcd8d244bacdnd Unless required by applicable law or agreed to in writing, software
d5d794fc2f4cc9ca6d6da17cfa2cdcd8d244bacdnd distributed under the License is distributed on an "AS IS" BASIS,
d5d794fc2f4cc9ca6d6da17cfa2cdcd8d244bacdnd WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
d5d794fc2f4cc9ca6d6da17cfa2cdcd8d244bacdnd See the License for the specific language governing permissions and
d5d794fc2f4cc9ca6d6da17cfa2cdcd8d244bacdnd limitations under the License.
c3fcea07965f59723831e23da647a77518285b8eslive<compatibility>Available in Apache 2.3 and later</compatibility>
23171986812b568beef50b28bdca284ab949e774rbowen <p>The session modules make use of HTTP cookies, and as such can fall
23171986812b568beef50b28bdca284ab949e774rbowen victim to Cross Site Scripting attacks, or expose potentially private
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh information to clients. Please ensure that the relevant risks have
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh been taken into account before enabling the session functionality on
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh your server.</p>
23171986812b568beef50b28bdca284ab949e774rbowen <p>This module provides support for a server wide per user session
251d54de2284abc4a59d0959487e1ddcb8714b4arbowen interface. Sessions can be used for keeping track of whether a user
251d54de2284abc4a59d0959487e1ddcb8714b4arbowen has been logged in, or for other per user information that should
4f3a5dcf5f9538e0e51183011e346c16be8dc126rbowen be kept available across requests.</p>
251d54de2284abc4a59d0959487e1ddcb8714b4arbowen <p>Sessions may be stored on the server, or may be stored on the
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh browser. Sessions may also be optionally encrypted for added security.
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh These features are divided into several modules in addition to
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh <module>mod_session</module>; <module>mod_session_crypto</module>,
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh <module>mod_session_cookie</module> and <module>mod_session_dbd</module>.
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh Depending on the server requirements, load the appropriate modules
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh into the server (either statically at compile time or dynamically
251d54de2284abc4a59d0959487e1ddcb8714b4arbowen via the <directive module="mod_so">LoadModule</directive> directive).</p>
14ae27a0c6c67bed36e2e8cb5099a02e19548943pquerna <p>Sessions may be manipulated from other modules that depend on the
23171986812b568beef50b28bdca284ab949e774rbowen session, or the session may be read from and written to using
23171986812b568beef50b28bdca284ab949e774rbowen environment variables and HTTP headers, as appropriate.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna<seealso><module>mod_session_cookie</module></seealso>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna<seealso><module>mod_session_crypto</module></seealso>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <section id="whatisasession"><title>What is a session?</title>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>At the core of the session interface is a table of key and value pairs
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna that are made accessible across browser requests. These pairs can be set
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna to any valid string, as needed by the application making use of the
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna session.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>The "session" is a <strong>application/x-www-form-urlencoded</strong>
860b4efe27e7c1c9a2bf5c872b29c90f76849b51jim string containing these key value pairs, as defined by the
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <a href="http://www.w3.org/TR/html4/">HTML specification</a>.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>The session can optionally be encrypted and base64 encoded before
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh being written to the storage mechanism, as defined by the
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh administrator.</p>
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh <section id="whocanuseasession"><title>Who can use a session?</title>
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh <p>The session interface is primarily developed for the use by other
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh server modules, such as <module>mod_auth_form</module>, however CGI
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh based applications can optionally be granted access to the contents
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh of the session via the HTTP_SESSION environment variable. Sessions
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh have the option to be modified and/or updated by inserting an HTTP
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna response header containing the new session parameters.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <section id="serversession"><title>Keeping sessions on the server</title>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>Apache can be configured to keep track of per user sessions stored
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna on a particular server or group of servers. This functionality is
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna similar to the sessions available in typical application servers.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>If configured, sessions are tracked through the use of a session ID that
860b4efe27e7c1c9a2bf5c872b29c90f76849b51jim is stored inside a cookie, or extracted from the parameters embedded
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna within the URL query string, as found in a typical GET request.</p>
14ae27a0c6c67bed36e2e8cb5099a02e19548943pquerna <p>As the contents of the session are stored exclusively on the server,
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna there is an expectation of privacy of the contents of the session. This
860b4efe27e7c1c9a2bf5c872b29c90f76849b51jim does have performance and resource implications should a large number
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna of sessions be present, or where a large number of webservers have to
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna share sessions with one another.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>The <module>mod_session_dbd</module> module allows the storage of user
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna sessions within a SQL database via <module>mod_dbd</module>.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <section id="browsersession"><title>Keeping sessions on the browser</title>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>In high traffic environments where keeping track of a session on a
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna server is too resource intensive or inconvenient, the option exists to store
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna the contents of the session within a cookie on the client browser instead.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>This has the advantage that minimal resources are required on the
3d636d91428f2c0a74012c89a94ec7d5b40aa52esf server to keep track of sessions, and multiple servers within a server
3d636d91428f2c0a74012c89a94ec7d5b40aa52esf farm have no need to share session information.</p>
3d636d91428f2c0a74012c89a94ec7d5b40aa52esf <p>The contents of the session however are exposed to the client, with a
3d636d91428f2c0a74012c89a94ec7d5b40aa52esf corresponding risk of a loss of privacy. The
3d636d91428f2c0a74012c89a94ec7d5b40aa52esf <module>mod_session_crypto</module> module can be configured to encrypt the
3d636d91428f2c0a74012c89a94ec7d5b40aa52esf contents of the session before writing the session to the client.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>The <module>mod_session_cookie</module> allows the storage of user
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna sessions on the browser within an HTTP cookie.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <section id="basicexamples"><title>Basic Examples</title>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>Creating a session is as simple as turning the session on, and deciding
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna where the session will be stored. In this example, the session will be
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna stored on the browser, in a cookie called <code>session</code>.</p>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquernaSessionCookieName session path=/
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna </highlight>
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna <p>The session is not useful unless it can be written to or read from. The
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna following example shows how values can be injected into the session through
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna the use of a predetermined HTTP response header called
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquernaSessionCookieName session path=/
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquernaSessionHeader X-Replace-Session
9242e4b895c96a03d7c575702cf6b69b5c2702c0pquerna </highlight>
15ba1801088da1aad6d20609cf3f7b0b1eefce8aslive <p>The header should contain name value pairs expressed in the same format
23171986812b568beef50b28bdca284ab949e774rbowen as a query string in a URL, as in the example below. Setting a key to the
72efd3996108e6e17834609af9cf84b95e4c586end empty string has the effect of removing that key from the session.</p>
23171986812b568beef50b28bdca284ab949e774rbowenecho "X-Replace-Session: key1=foo&key2=&key3=bar"
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh </highlight>
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh <p>If configured, the session can be read back from the HTTP_SESSION
4c05a0bde64b79d08f4a8791e5919151ff353849humbedooh environment variable. By default, the session is kept private, so this
23171986812b568beef50b28bdca284ab949e774rbowen has to be explicitly turned on with the
23171986812b568beef50b28bdca284ab949e774rbowen <directive module="mod_session">SessionEnv</directive> directive.</p>
SessionCookieName session path=/private;domain=example.com;httponly;secure;