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8 <title>mod_authn_socache - Apache HTTP Server Version 2.5</title>
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24 <div id="page-content">
25 <div id="preamble"><h1>Apache Module mod_authn_socache</h1>
27 <p><span>Available Languages: </span><a href="../en/mod/mod_authn_socache.html" title="English"> en </a> |
28 <a href="../fr/mod/mod_authn_socache.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p>
30 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Manages a cache of authentication credentials to relieve
31 the load on backends</td></tr>
32 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Base</td></tr>
33 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>authn_socache_module</td></tr>
34 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_authn_socache.c</td></tr>
35 <tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Version 2.3 and later</td></tr></table>
38 <p>Maintains a cache of authentication credentials, so that a new backend
39 lookup is not required for every authenticated request.</p>
41 <div id="quickview"><h3 class="directives">Directives</h3>
43 <li><img alt="" src="../images/down.gif" /> <a href="#authncachecontext">AuthnCacheContext</a></li>
44 <li><img alt="" src="../images/down.gif" /> <a href="#authncacheenable">AuthnCacheEnable</a></li>
45 <li><img alt="" src="../images/down.gif" /> <a href="#authncacheprovidefor">AuthnCacheProvideFor</a></li>
46 <li><img alt="" src="../images/down.gif" /> <a href="#authncachesocache">AuthnCacheSOCache</a></li>
47 <li><img alt="" src="../images/down.gif" /> <a href="#authncachetimeout">AuthnCacheTimeout</a></li>
51 <li><img alt="" src="../images/down.gif" /> <a href="#intro">Authentication Cacheing</a></li>
52 <li><img alt="" src="../images/down.gif" /> <a href="#usage">Usage</a></li>
53 <li><img alt="" src="../images/down.gif" /> <a href="#dev">Cacheing with custom modules</a></li>
54 </ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
55 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
57 <h2><a name="intro" id="intro">Authentication Cacheing</a></h2>
58 <p>Some users of more heavyweight authentication such as SQL database
59 lookups (<code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code>) have reported it putting an
60 unacceptable load on their authentication provider. A typical case
61 in point is where an HTML page contains hundreds of objects
62 (images, scripts, stylesheets, media, etc), and a request to the page
63 generates hundreds of effectively-immediate requests for authenticated
64 additional contents.</p>
65 <p>mod_authn_socache provides a solution to this problem by
66 maintaining a cache of authentication credentials.</p>
67 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
69 <h2><a name="usage" id="usage">Usage</a></h2>
70 <p>The authentication cache should be used where authentication
71 lookups impose a significant load on the server, or a backend or
72 network. Authentication by file (<code class="module"><a href="../mod/mod_authn_file.html">mod_authn_file</a></code>)
73 or dbm (<code class="module"><a href="../mod/mod_authn_dbm.html">mod_authn_dbm</a></code>) are unlikely to benefit,
74 as these are fast and lightweight in their own right (though in some
75 cases, such as a network-mounted file, cacheing may be worthwhile).
76 Other providers such as SQL or LDAP based authentication are more
77 likely to benefit, particularly where there is an observed
78 performance issue. Amongst the standard modules, <code class="module"><a href="../mod/mod_authnz_ldap.html">mod_authnz_ldap</a></code> manages its own cache, so only
79 <code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code> will usually benefit from this cache.</p>
80 <p>The basic rules to cache for a provider are:</p>
81 <ol><li>Include the provider you're cacheing for in an
82 <code class="directive">AuthnCacheProvideFor</code> directive.</li>
83 <li>List <var>socache</var> ahead of the provider you're
84 cacheing for in your <code class="directive"><a href="../mod/mod_auth_basic.html#authbasicprovider">AuthBasicProvider</a></code> or <code class="directive"><a href="../mod/mod_auth_digest.html#authdigestprovider">AuthDigestProvider</a></code> directive.</li>
86 <p>A simple usage example to accelerate <code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code>
87 using dbm as a cache engine:</p>
88 <pre class="prettyprint lang-config">#AuthnCacheSOCache is optional. If specified, it is server-wide
90 <Directory /usr/www/myhost/private>
92 AuthName "Cached Authentication Example"
93 AuthBasicProvider socache dbd
94 AuthDBDUserPWQuery "SELECT password FROM authn WHERE user = %s"
95 AuthnCacheProvideFor dbd
98 AuthnCacheContext dbd-authn-example
99 </Directory></pre>
101 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
102 <div class="section">
103 <h2><a name="dev" id="dev">Cacheing with custom modules</a></h2>
104 <p>Module developers should note that their modules must be enabled
105 for cacheing with mod_authn_socache. A single optional API function
106 <var>ap_authn_cache_store</var> is provided to cache credentials
107 a provider has just looked up or generated. Usage examples are
108 available in <a href="http://svn.eu.apache.org/viewvc?view=revision&revision=957072">r957072</a>, in which three authn providers are enabled for cacheing.</p>
110 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
111 <div class="directive-section"><h2><a name="AuthnCacheContext" id="AuthnCacheContext">AuthnCacheContext</a> <a name="authncachecontext" id="authncachecontext">Directive</a></h2>
112 <table class="directive">
113 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a context string for use in the cache key</td></tr>
114 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheContext <var>directory|server|custom-string</var></code></td></tr>
115 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>directory</code></td></tr>
116 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory</td></tr>
117 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
118 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
120 <p>This directive specifies a string to be used along with the supplied
121 username (and realm in the case of Digest Authentication) in constructing
122 a cache key. This serves to disambiguate identical usernames serving
123 different authentication areas on the server.</p>
124 <p>Two special values for this are <var>directory</var>, which uses
125 the directory context of the request as a string, and <var>server</var>
126 which uses the virtual host name.</p>
127 <p>The default is <var>directory</var>, which is also the most
128 conservative setting. This is likely to be less than optimal, as it
129 (for example) causes <var>$app-base</var>, <var>$app-base/images</var>,
130 <var>$app-base/scripts</var> and <var>$app-base/media</var> each to
131 have its own separate cache key. A better policy is to name the
132 <code class="directive">AuthnCacheContext</code> for the password
133 provider: for example a <var>htpasswd</var> file or database table.</p>
134 <p>Contexts can be shared across different areas of a server, where
135 credentials are shared. However, this has potential to become a vector
136 for cross-site or cross-application security breaches, so this directive
137 is not permitted in <var>.htaccess</var> contexts.</p>
140 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
141 <div class="directive-section"><h2><a name="AuthnCacheEnable" id="AuthnCacheEnable">AuthnCacheEnable</a> <a name="authncacheenable" id="authncacheenable">Directive</a></h2>
142 <table class="directive">
143 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable Authn caching configured anywhere</td></tr>
144 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheEnable</code></td></tr>
145 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
146 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>None</td></tr>
147 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
148 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
150 <p>This directive is not normally necessary: it is implied if
151 authentication cacheing is enabled anywhere in <var>httpd.conf</var>.
152 However, if it is not enabled anywhere in <var>httpd.conf</var>
153 it will by default not be initialised, and is therefore not
154 available in a <var>.htaccess</var> context. This directive
155 ensures it is initialised so it can be used in <var>.htaccess</var>.</p>
158 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
159 <div class="directive-section"><h2><a name="AuthnCacheProvideFor" id="AuthnCacheProvideFor">AuthnCacheProvideFor</a> <a name="authncacheprovidefor" id="authncacheprovidefor">Directive</a></h2>
160 <table class="directive">
161 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify which authn provider(s) to cache for</td></tr>
162 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheProvideFor <var>authn-provider</var> [...]</code></td></tr>
163 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>None</code></td></tr>
164 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
165 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>AuthConfig</td></tr>
166 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
167 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
169 <p>This directive specifies an authentication provider or providers
170 to cache for. Credentials found by a provider not listed in an
171 AuthnCacheProvideFor directive will not be cached.</p>
173 <p>For example, to cache credentials found by <code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code>
174 or by a custom provider <var>myprovider</var>, but leave those looked
175 up by lightweight providers like file or dbm lookup alone:</p>
176 <pre class="prettyprint lang-config">AuthnCacheProvideFor dbd myprovider</pre>
180 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
181 <div class="directive-section"><h2><a name="AuthnCacheSOCache" id="AuthnCacheSOCache">AuthnCacheSOCache</a> <a name="authncachesocache" id="authncachesocache">Directive</a></h2>
182 <table class="directive">
183 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Select socache backend provider to use</td></tr>
184 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheSOCache <var>provider-name[:provider-args]</var></code></td></tr>
185 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
186 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>None</td></tr>
187 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
188 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
189 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Optional provider arguments are available in
190 Apache HTTP Server 2.4.7 and later</td></tr>
192 <p>This is a server-wide setting to select a provider for the
193 <a href="../socache.html">shared object cache</a>, followed by
194 optional arguments for that provider.
195 Some possible values for <var>provider-name</var> are "dbm", "dc",
196 "memcache", or "shmcb", each subject to the appropriate module
197 being loaded. If not set, your platform's default will be used.</p>
200 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
201 <div class="directive-section"><h2><a name="AuthnCacheTimeout" id="AuthnCacheTimeout">AuthnCacheTimeout</a> <a name="authncachetimeout" id="authncachetimeout">Directive</a></h2>
202 <table class="directive">
203 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Set a timeout for cache entries</td></tr>
204 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheTimeout <var>timeout</var> (seconds)</code></td></tr>
205 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>300 (5 minutes)</code></td></tr>
206 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
207 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>AuthConfig</td></tr>
208 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
209 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
211 <p>Cacheing authentication data can be a security issue, though short-term
212 cacheing is unlikely to be a problem. Typically a good solution is to
213 cache credentials for as long as it takes to relieve the load on a
214 backend, but no longer, though if changes to your users and passwords
215 are infrequent then a longer timeout may suit you. The default 300
216 seconds (5 minutes) is both cautious and ample to keep the load
217 on a backend such as dbd (SQL database queries) down.</p>
218 <p>This should not be confused with session timeout, which is an
219 entirely separate issue. However, you may wish to check your
220 session-management software for whether cached credentials can
221 "accidentally" extend a session, and bear it in mind when setting
226 <div class="bottomlang">
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