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24<div id="page-content">
25<div id="preamble"><h1>Apache Module mod_authn_socache</h1>
26<div class="toplang">
27<p><span>Available Languages: </span><a href="/en/mod/mod_authn_socache.html" title="English">&nbsp;en&nbsp;</a> |
28<a href="/fr/mod/mod_authn_socache.html" hreflang="fr" rel="alternate" title="Fran�ais">&nbsp;fr&nbsp;</a></p>
29</div>
30<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Manages a cache of authentication credentials to relieve
31the 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>
36<h3>Summary</h3>
37
38    <p>Maintains a cache of authentication credentials, so that a new backend
39    lookup is not required for every authenticated request.</p>
40</div>
41<div id="quickview"><h3 class="directives">Directives</h3>
42<ul id="toc">
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>
48</ul>
49<h3>Topics</h3>
50<ul id="topics">
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>
56<div class="section">
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>
68<div class="section">
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>
85    </ol>
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">&lt;Directory /usr/www/myhost/private&gt;
89    AuthType Basic
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
95    AuthnCacheSOCache dbm
96    Require valid-user
97&lt;/Directory&gt;</pre>
98
99</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
100<div class="section">
101<h2><a name="dev" id="dev">Cacheing with custom modules</a></h2>
102    <p>Module developers should note that their modules must be enabled
103    for cacheing with mod_authn_socache.  A single optional API function
104    <var>ap_authn_cache_store</var> is provided to cache credentials
105    a provider has just looked up or generated.  Usage examples are
106    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>
107</div>
108<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
109<div class="directive-section"><h2><a name="AuthnCacheContext" id="AuthnCacheContext">AuthnCacheContext</a> <a name="authncachecontext" id="authncachecontext">Directive</a></h2>
110<table class="directive">
111<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a context string for use in the cache key</td></tr>
112<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheContext <var>directory|server|custom-string</var></code></td></tr>
113<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>directory</code></td></tr>
114<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory</td></tr>
115<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
116<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
117</table>
118    <p>This directive specifies a string to be used along with the supplied
119    username (and realm in the case of Digest Authentication) in constructing
120    a cache key.  This serves to disambiguate identical usernames serving
121    different authentication areas on the server.</p>
122    <p>Two special values for this are <var>directory</var>, which uses
123    the directory context of the request as a string, and <var>server</var>
124    which uses the virtual host name.</p>
125    <p>The default is <var>directory</var>, which is also the most
126    conservative setting.  This is likely to be less than optimal, as it
127    (for example) causes <var>$app-base</var>, <var>$app-base/images</var>,
128    <var>$app-base/scripts</var> and <var>$app-base/media</var> each to
129    have its own separate cache key.  A better policy is to name the
130    <code class="directive">AuthnCacheContext</code> for the password
131    provider: for example a <var>htpasswd</var> file or database table.</p>
132    <p>Contexts can be shared across different areas of a server, where
133    credentials are shared.  However, this has potential to become a vector
134    for cross-site or cross-application security breaches, so this directive
135    is not permitted in <var>.htaccess</var> contexts.</p>
136
137</div>
138<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
139<div class="directive-section"><h2><a name="AuthnCacheEnable" id="AuthnCacheEnable">AuthnCacheEnable</a> <a name="authncacheenable" id="authncacheenable">Directive</a></h2>
140<table class="directive">
141<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable Authn caching configured anywhere</td></tr>
142<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheEnable</code></td></tr>
143<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
144<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>None</td></tr>
145<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
146<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
147</table>
148    <p>This directive is not normally necessary: it is implied if
149    authentication cacheing is enabled anywhere in <var>httpd.conf</var>.
150    However, if it is not enabled anywhere in <var>httpd.conf</var>
151    it will by default not be initialised, and is therefore not
152    available in a <var>.htaccess</var> context.  This directive
153    ensures it is initialised so it can be used in <var>.htaccess</var>.</p>
154
155</div>
156<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
157<div class="directive-section"><h2><a name="AuthnCacheProvideFor" id="AuthnCacheProvideFor">AuthnCacheProvideFor</a> <a name="authncacheprovidefor" id="authncacheprovidefor">Directive</a></h2>
158<table class="directive">
159<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify which authn provider(s) to cache for</td></tr>
160<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheProvideFor <var>authn-provider</var> [...]</code></td></tr>
161<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>None</code></td></tr>
162<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
163<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>AuthConfig</td></tr>
164<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
165<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
166</table>
167    <p>This directive specifies an authentication provider or providers
168    to cache for.  Credentials found by a provider not listed in an
169    AuthnCacheProvideFor directive will not be cached.</p>
170
171    <p>For example, to cache credentials found by <code class="module"><a href="/mod/mod_authn_dbd.html">mod_authn_dbd</a></code>
172    or by a custom provider <var>myprovider</var>, but leave those looked
173    up by lightweight providers like file or dbm lookup alone:</p>
174    <pre class="prettyprint lang-config">AuthnCacheProvideFor dbd myprovider</pre>
175
176
177</div>
178<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
179<div class="directive-section"><h2><a name="AuthnCacheSOCache" id="AuthnCacheSOCache">AuthnCacheSOCache</a> <a name="authncachesocache" id="authncachesocache">Directive</a></h2>
180<table class="directive">
181<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Select socache backend provider to use</td></tr>
182<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheSOCache <var>provider-name[:provider-args]</var></code></td></tr>
183<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
184<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>None</td></tr>
185<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
186<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
187<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Optional provider arguments are available in
188Apache HTTP Server 2.4.7 and later</td></tr>
189</table>
190    <p>This is a server-wide setting to select a provider for the
191    <a href="/socache.html">shared object cache</a>, followed by
192    optional arguments for that provider.
193    Some possible values for <var>provider-name</var> are "dbm", "dc",
194    "memcache", or "shmcb", each subject to the appropriate module
195    being loaded.  If not set, your platform's default will be used.</p>
196
197</div>
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>
208</table>
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
220    your timeout.</p>
221
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