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