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| <div id="preamble"><h1>Apache Module mod_authn_socache</h1> |
| <div class="toplang"> |
| <p><span>Available Languages: </span><a href="../en/mod/mod_authn_socache.html" title="English"> en </a> | |
| <a href="../fr/mod/mod_authn_socache.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p> |
| </div> |
| <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Manages a cache of authentication credentials to relieve |
| the load on backends</td></tr> |
| <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Base</td></tr> |
| <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>authn_socache_module</td></tr> |
| <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_authn_socache.c</td></tr> |
| <tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Version 2.3 and later</td></tr></table> |
| <h3>Summary</h3> |
| |
| <p>Maintains a cache of authentication credentials, so that a new backend |
| lookup is not required for every authenticated request.</p> |
| </div> |
| <div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3>Topics</h3> |
| <ul id="topics"> |
| <li><img alt="" src="../images/down.gif" /> <a href="#intro">Authentication Caching</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#usage">Usage</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#dev">Caching with custom modules</a></li> |
| </ul><h3 class="directives">Directives</h3> |
| <ul id="toc"> |
| <li><img alt="" src="../images/down.gif" /> <a href="#authncachecontext">AuthnCacheContext</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#authncacheenable">AuthnCacheEnable</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#authncacheprovidefor">AuthnCacheProvideFor</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#authncachesocache">AuthnCacheSOCache</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#authncachetimeout">AuthnCacheTimeout</a></li> |
| </ul> |
| <h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_authn_socache">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_authn_socache">Report a bug</a></li></ul><h3>See also</h3> |
| <ul class="seealso"> |
| <li><a href="#comments_section">Comments</a></li></ul></div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="intro" id="intro">Authentication Caching</a></h2> |
| <p>Some users of more heavyweight authentication such as SQL database |
| lookups (<code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code>) have reported it putting an |
| unacceptable load on their authentication provider. A typical case |
| in point is where an HTML page contains hundreds of objects |
| (images, scripts, stylesheets, media, etc), and a request to the page |
| generates hundreds of effectively-immediate requests for authenticated |
| additional contents.</p> |
| <p><code class="module"><a href="../mod/mod_authn_socache.html">mod_authn_socache</a></code> provides a solution to this problem by |
| maintaining a cache of authentication credentials.</p> |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="usage" id="usage">Usage</a></h2> |
| <p>The authentication cache should be used where authentication |
| lookups impose a significant load on the server, or a backend or |
| network. Authentication by file (<code class="module"><a href="../mod/mod_authn_file.html">mod_authn_file</a></code>) |
| or dbm (<code class="module"><a href="../mod/mod_authn_dbm.html">mod_authn_dbm</a></code>) are unlikely to benefit, |
| as these are fast and lightweight in their own right (though in some |
| cases, such as a network-mounted file, caching may be worthwhile). |
| Other providers such as SQL or LDAP based authentication are more |
| likely to benefit, particularly where there is an observed |
| 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 |
| <code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code> will usually benefit from this cache.</p> |
| <p>The basic rules to cache for a provider are:</p> |
| <ol><li>Include the provider you're caching for in an |
| <code class="directive"><a href="#authncacheprovidefor">AuthnCacheProvideFor</a></code> directive.</li> |
| <li>List <var>socache</var> ahead of the provider you're |
| caching 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> |
| </ol> |
| <p>A simple usage example to accelerate <code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code> |
| using dbm as a cache engine:</p> |
| <pre class="prettyprint lang-config">#AuthnCacheSOCache is optional. If specified, it is server-wide |
| AuthnCacheSOCache dbm |
| <Directory "/usr/www/myhost/private"> |
| AuthType Basic |
| AuthName "Cached Authentication Example" |
| AuthBasicProvider socache dbd |
| AuthDBDUserPWQuery "SELECT password FROM authn WHERE user = %s" |
| AuthnCacheProvideFor dbd |
| Require valid-user |
| #Optional |
| AuthnCacheContext dbd-authn-example |
| </Directory></pre> |
| |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="dev" id="dev">Caching with custom modules</a></h2> |
| <p>Module developers should note that their modules must be enabled |
| for caching with <code class="module"><a href="../mod/mod_authn_socache.html">mod_authn_socache</a></code>. A single optional API function |
| <var>ap_authn_cache_store</var> is provided to cache credentials |
| a provider has just looked up or generated. Usage examples are |
| available in <a href="http://svn.eu.apache.org/viewvc?view=revision&revision=957072">r957072</a>, in which three authn providers are enabled for caching.</p> |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="AuthnCacheContext" id="AuthnCacheContext">AuthnCacheContext</a> <a name="authncachecontext" id="authncachecontext">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a context string for use in the cache key</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheContext directory|server|<var>custom-string</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AuthnCacheContext directory</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr> |
| </table> |
| <p>This directive specifies a string to be used along with the supplied |
| username (and realm in the case of Digest Authentication) in constructing |
| a cache key. This serves to disambiguate identical usernames serving |
| different authentication areas on the server.</p> |
| <p>Two special values for this are <code>directory</code>, which uses |
| the directory context of the request as a string, and <code>server</code> |
| which uses the virtual host name.</p> |
| <p>The default is <code>directory</code>, which is also the most |
| conservative setting. This is likely to be less than optimal, as it |
| (for example) causes <var>$app-base</var>, <var>$app-base/images</var>, |
| <var>$app-base/scripts</var> and <var>$app-base/media</var> each to |
| have its own separate cache key. A better policy is to name the |
| <code class="directive">AuthnCacheContext</code> for the password |
| provider: for example a <var>htpasswd</var> file or database table.</p> |
| <p>Contexts can be shared across different areas of a server, where |
| credentials are shared. However, this has potential to become a vector |
| for cross-site or cross-application security breaches, so this directive |
| is not permitted in <var>.htaccess</var> contexts.</p> |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="AuthnCacheEnable" id="AuthnCacheEnable">AuthnCacheEnable</a> <a name="authncacheenable" id="authncacheenable">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable Authn caching configured anywhere</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheEnable</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr> |
| </table> |
| <p>This directive is not normally necessary: it is implied if |
| authentication caching is enabled anywhere in <var>httpd.conf</var>. |
| However, if it is not enabled anywhere in <var>httpd.conf</var> |
| it will by default not be initialised, and is therefore not |
| available in a <var>.htaccess</var> context. This directive |
| ensures it is initialised so it can be used in <var>.htaccess</var>.</p> |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="AuthnCacheProvideFor" id="AuthnCacheProvideFor">AuthnCacheProvideFor</a> <a name="authncacheprovidefor" id="authncacheprovidefor">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify which authn provider(s) to cache for</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheProvideFor <var>authn-provider</var> [...]</code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>None</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr> |
| <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>AuthConfig</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr> |
| </table> |
| <p>This directive specifies an authentication provider or providers |
| to cache for. Credentials found by a provider not listed in an |
| <code class="directive">AuthnCacheProvideFor</code> directive will not be cached.</p> |
| |
| <p>For example, to cache credentials found by <code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code> |
| or by a custom provider <var>myprovider</var>, but leave those looked |
| up by lightweight providers like file or dbm lookup alone:</p> |
| <pre class="prettyprint lang-config">AuthnCacheProvideFor dbd myprovider</pre> |
| |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="AuthnCacheSOCache" id="AuthnCacheSOCache">AuthnCacheSOCache</a> <a name="authncachesocache" id="authncachesocache">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Select socache backend provider to use</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheSOCache <var>provider-name[:provider-args]</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr> |
| <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Optional provider arguments are available in |
| Apache HTTP Server 2.4.7 and later</td></tr> |
| </table> |
| <p>This is a server-wide setting to select a provider for the |
| <a href="../socache.html">shared object cache</a>, followed by |
| optional arguments for that provider. |
| Some possible values for <var>provider-name</var> are "dbm", "dc", |
| "memcache", or "shmcb", each subject to the appropriate module |
| being loaded. If not set, your platform's default will be used.</p> |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="AuthnCacheTimeout" id="AuthnCacheTimeout">AuthnCacheTimeout</a> <a name="authncachetimeout" id="authncachetimeout">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Set a timeout for cache entries</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheTimeout <var>timeout</var> (seconds)</code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AuthnCacheTimeout 300 (5 minutes)</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr> |
| <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>AuthConfig</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr> |
| </table> |
| <p>Caching authentication data can be a security issue, though short-term |
| caching is unlikely to be a problem. Typically a good solution is to |
| cache credentials for as long as it takes to relieve the load on a |
| backend, but no longer, though if changes to your users and passwords |
| are infrequent then a longer timeout may suit you. The default 300 |
| seconds (5 minutes) is both cautious and ample to keep the load |
| on a backend such as dbd (SQL database queries) down.</p> |
| <p>This should not be confused with session timeout, which is an |
| entirely separate issue. However, you may wish to check your |
| session-management software for whether cached credentials can |
| "accidentally" extend a session, and bear it in mind when setting |
| your timeout.</p> |
| |
| </div> |
| </div> |
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