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   8 <title>mod_policy - Apache HTTP Server</title>
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  20 <a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.5</a> &gt; <a href="./">Modules</a></div>
  21 <div id="page-content">
  22 <div id="preamble"><h1>Apache Module mod_policy</h1>
  23 <div class="toplang">
  24 <p><span>Available Languages: </span><a href="../en/mod/mod_policy.html" title="English">&nbsp;en&nbsp;</a></p>
  25 </div>
  26 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>HTTP protocol compliance enforcement.</td></tr>
  27 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  28 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>policy_module</td></tr>
  29 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_policy.c</td></tr></table>
  30 <h3>Summary</h3>
  31
  32     <p>The HTTP protocol recommends that clients should be "liberal in
  33     what they accept", and servers "strict with what they send". In some
  34     cases it can be difficult to detect when a server or an application
  35     has been misconfigured, is serving uncacheable content or is behaving
  36     suboptimally, as an HTTP client might be compensating for the server.
  37     These problems can potentially lead to excessive bandwidth
  38     consumption, or a server outage under load.</p>
  39
  40     <p>The <code class="module"><a href="../mod/mod_policy.html">mod_policy</a></code> module consists of a set of
  41     filters that test servers for HTTP protocol compliance. These
  42     tests allow the server administrator to log violations of, or
  43     outright reject responses where certain defined conditions exist.</p>
  44
  45     <p>This could be used as a way to set minimum HTTP protocol compliance
  46     criteria for a restful application. Alternatively, a reverse proxy or
  47     cache could be configured to protect itself from misconfigured origin
  48     servers or unexpectedly uncacheable content, or as a mechanism to
  49     detect configuration mistakes within the server itself.</p>
  50
  51 </div>
  52 <div id="quickview"><h3 class="directives">Directives</h3>
  53 <ul id="toc">
  54 <li><img alt="" src="../images/down.gif" /> <a href="#policyconditional">PolicyConditional</a></li>
  55 <li><img alt="" src="../images/down.gif" /> <a href="#policyconditionalurl">PolicyConditionalURL</a></li>
  56 <li><img alt="" src="../images/down.gif" /> <a href="#policyenvironment">PolicyEnvironment</a></li>
  57 <li><img alt="" src="../images/down.gif" /> <a href="#policyfilter">PolicyFilter</a></li>
  58 <li><img alt="" src="../images/down.gif" /> <a href="#policykeepalive">PolicyKeepalive</a></li>
  59 <li><img alt="" src="../images/down.gif" /> <a href="#policykeepaliveurl">PolicyKeepaliveURL</a></li>
  60 <li><img alt="" src="../images/down.gif" /> <a href="#policylength">PolicyLength</a></li>
  61 <li><img alt="" src="../images/down.gif" /> <a href="#policylengthurl">PolicyLengthURL</a></li>
  62 <li><img alt="" src="../images/down.gif" /> <a href="#policymaxage">PolicyMaxage</a></li>
  63 <li><img alt="" src="../images/down.gif" /> <a href="#policymaxageurl">PolicyMaxageURL</a></li>
  64 <li><img alt="" src="../images/down.gif" /> <a href="#policynocache">PolicyNocache</a></li>
  65 <li><img alt="" src="../images/down.gif" /> <a href="#policynocacheurl">PolicyNocacheURL</a></li>
  66 <li><img alt="" src="../images/down.gif" /> <a href="#policytype">PolicyType</a></li>
  67 <li><img alt="" src="../images/down.gif" /> <a href="#policytypeurl">PolicyTypeURL</a></li>
  68 <li><img alt="" src="../images/down.gif" /> <a href="#policyvalidation">PolicyValidation</a></li>
  69 <li><img alt="" src="../images/down.gif" /> <a href="#policyvalidationurl">PolicyValidationURL</a></li>
  70 <li><img alt="" src="../images/down.gif" /> <a href="#policyvary">PolicyVary</a></li>
  71 <li><img alt="" src="../images/down.gif" /> <a href="#policyvaryurl">PolicyVaryURL</a></li>
  72 <li><img alt="" src="../images/down.gif" /> <a href="#policyversion">PolicyVersion</a></li>
  73 <li><img alt="" src="../images/down.gif" /> <a href="#policyversionurl">PolicyVersionURL</a></li>
  74 </ul>
  75 <h3>Topics</h3>
  76 <ul id="topics">
  77 <li><img alt="" src="../images/down.gif" /> <a href="#actions">Actions</a></li>
  78 <li><img alt="" src="../images/down.gif" /> <a href="#tests">Policy Tests</a></li>
  79 <li><img alt="" src="../images/down.gif" /> <a href="#example">Example Configuration</a></li>
  80 </ul><h3>See also</h3>
  81 <ul class="seealso">
  82 <li><a href="../filter.html">Filters</a></li>
  83 <li><a href="../compliance.html">HTTP Protocol Compliance</a></li>
  84 </ul></div>
  85 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  86 <div class="section">
  87 <h2><a name="actions" id="actions">Actions</a></h2>
  88
  89
  90     <p>If a policy is violated, one of the following actions can be
  91     taken:</p>
  92
  93     <dl>
  94     <dt><strong>ignore</strong></dt>
  95     <dd>The policy check will be ignored for the given URL space, even
  96     if the filter is present.</dd>
  97
  98     <dt><strong>log</strong></dt>
  99     <dd>The policy check will be executed, and if a violation is detected
 100     a warning will be logged to the server error_log, and a
 101     <code>Warning</code> header added to the response for the benefit of
 102     the client.</dd>
 103
 104     <dt><strong>enforce</strong></dt>
 105     <dd>The policy check will be executed, and if a violation is detected
 106     an error will be logged to the server error_log, a
 107     <code>Warning</code> header added to the response, and a <code>502
 108     Bad Gateway</code> will be returned to the client. Optional links to
 109     explanatory documentation can be added to each error message,
 110     detailing the origin of each policy.</dd>
 111
 112     </dl>
 113
 114     <p>It is also possible to selectively disable all policies for a
 115     given URL space, should the need arise, using the
 116     <code class="directive"><a href="#policyfilter">PolicyFilter</a></code> directive.</p>
 117
 118     <p>Alternatively, the
 119     <code class="directive"><a href="#policyenvironment">PolicyEnvironment</a></code>
 120     directive can be used to specify an environment variable, which if
 121     present, will cause the policies to be selectively downgraded or
 122     bypassed.</p>
 123
 124 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 125 <div class="section">
 126 <h2><a name="tests" id="tests">Policy Tests</a></h2>
 127
 128
 129     <p>The following policy filters are available:</p>
 130
 131     <dl>
 132     <dt><strong><a href="../compliance.html#policytype">POLICY_TYPE</a>
 133     </strong>: Enforce valid content types</dt>
 134     <dd>Content types that are syntactically invalid or blank can be detected
 135         and the request rejected. Types can be restricted to a specific list
 136         containing optional wildcards ? and *.</dd>
 137
 138     <dt><strong><a href="../compliance.html#policylength">POLICY_LENGTH</a>
 139     </strong>: Enforce the presence of a Content-Length</dt>
 140     <dd>The length of responses can be specified in one of three ways, by
 141     specifying an explicit length in advance, using chunked encoding to set
 142     the length, or by setting no length at all and terminating the request
 143     when complete. The absence of a specific content length can affect the
 144     cacheability of the response, and prevents the use of keepalive during
 145     HTTP/1.0 requests. This policy enforces the presence of an explicit
 146     content length on the response.</dd>
 147
 148     <dt><strong><a href="../compliance.html#policykeepalive">POLICY_KEEPALIVE
 149     </a></strong>: Enforce the option to keepalive</dt>
 150     <dd>Less restrictive than the POLICY_LENGTH test, this policy enforces the
 151     possibility that the response can be kept alive. If the response doesn't
 152     have a protocol defined zero length, and the response isn't already an
 153     error, and the response has neither a Content-Length or is declared
 154     HTTP/1.1 and lacks Content-Encoding: chunked, then this response will be
 155     rejected.</dd>
 156
 157     <dt><strong><a href="../compliance.html#policyvary">POLICY_VARY</a>
 158     </strong>: Enforce the absence of certain headers within Vary headers</dt>
 159     <dd>If the Vary header contains any of the headers specified, this policy
 160     will reject the request. The typical case is the presence of the User-Agent
 161     within Vary, which is likely to cause a denial of service condition to a
 162     cache.</dd>
 163
 164     <dt><strong><a href="../compliance.html#policyvalidation">
 165     POLICY_VALIDATION</a></strong>: Enforce the presence of Etag and/or
 166     Last-Modified</dt>
 167     <dd>The ability for a cache to determine whether a cached entity can be
 168     refreshed is dependent on whether a valid Etag and/or Last-Modified header
 169     is present to revalidate against. The absence of both headers, or the
 170     invalid syntax of a header will cause this policy to be rejected.</dd>
 171
 172     <dt><strong><a href="../compliance.html#policyconditional">
 173     POLICY_CONDITIONAL</a></strong>: Enforce correct operation of conditional
 174     requests</dt>
 175     <dd>When conditional headers are present in the request, a server should
 176     respond with a <code>304 Not Modified</code> or <code>412 Precondition
 177     Failed</code> response where appropriate. A server may ignore conditional
 178     headers, and this affects the efficiency of the HTTP caching mechanism.
 179     This policy rejects requests where a conditional header is present, and
 180     a 304 or 412 response code was expected, but a 2xx response was seen
 181     instead.</dd>
 182
 183     <dt><strong><a href="../compliance.html#policynocache">POLICY_NOCACHE</a>
 184     </strong>: Enforce cacheable responses</dt>
 185     <dd>When a response is encountered that declares itself explicitly
 186     uncacheable, the request is rejected. A response is considered
 187     uncacheable if it specifies any of the following:
 188     <ul><li><code>Cache-Control: no-cache</code></li>
 189     <li><code>Pragma: no-cache</code></li>
 190     <li><code>Cache-Control: no-store</code></li>
 191     <li><code>Cache-Control: private</code></li>
 192     </ul></dd>
 193
 194     <dt><strong><a href="../compliance.html#policymaxage">POLICY_MAXAGE</a>
 195     </strong>: Enforce a minimum maxage</dt>
 196     <dd>When a response is encountered where the freshness lifetime is less
 197     than the given value, or the freshness lifetime is heuristic, the request
 198     is rejected. A response is checked in the following order:
 199     <ul><li>If <code>s-maxage</code> is present but too small; or</li>
 200     <li>If <code>max-age</code> is present but too small; or</li>
 201     <li>If <code>Expires</code> is present and invalid; or</li>
 202     <li><code>Date</code> is present and invalid; or</li>
 203     <li><code>Expires</code> minus Date is too small; or</li>
 204     <li>No <code>s-maxage</code>, <code>maxage</code>, or
 205     <code>Expires</code>/<code>Date</code> declared at all</li>
 206     </ul></dd>
 207
 208     <dt><strong><a href="../compliance.html#policyversion">POLICY_VERSION</a>
 209     </strong>: Enforce a minimum HTTP version within a request</dt>
 210     <dd>When a request is encountered with an HTTP version number less than
 211     the required minimum version, the request is rejected. The following
 212     version numbers are recognised:
 213     <ul><li><code>HTTP/1.1</code></li>
 214     <li><code>HTTP/1.0</code></li>
 215     <li><code>HTTP/0.9</code></li>
 216     </ul></dd>
 217
 218     </dl>
 219
 220 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 221 <div class="section">
 222 <h2><a name="example" id="example">Example Configuration</a></h2>
 223
 224
 225     <p>A typical configuration protecting a server serving static content
 226     might be as follows:</p>
 227
 228     <div class="example"><p><code>
 229     &lt;Location /&gt;<br />
 230     <span class="indent">
 231       SetOutputFilter POLICY_TYPE;POLICY_LENGTH;POLICY_KEEPALIVE;POLICY_VARY;POLICY_VALIDATION; \<br />
 232       <span class="indent">
 233         POLICY_CONDITIONAL;POLICY_NOCACHE;POLICY_MAXAGE;POLICY_VERSION<br />
 234       </span>
 235       <br />
 236       # content type must be present and valid, but can be anything<br />
 237       PolicyType enforce */*<br />
 238       <br />
 239       # reject if no explicitly declared content length<br />
 240       PolicyLength enforce<br />
 241       <br />
 242       # covered by the policy length filter<br />
 243       PolicyKeepalive ignore<br />
 244       <br />
 245       # reject if User-Agent appears within Vary headers<br />
 246       PolicyVary enforce User-Agent<br />
 247       <br />
 248       # we want to enforce validation<br />
 249       PolicyValidation enforce<br />
 250       <br />
 251       # non-functional conditional responses should be rejected<br />
 252       PolicyConditional enforce<br />
 253       <br />
 254       # no-cache responses should be rejected<br />
 255       PolicyNocache enforce<br />
 256       <br />
 257       # maxage must be at least a day<br />
 258       PolicyMaxage enforce 86400<br />
 259       <br />
 260       # request version can be anything<br />
 261       PolicyVersion ignore HTTP/1.1<br />
 262     </span>
 263     &lt;/Location&gt;<br />
 264     <br />
 265     # suppress policy protection for server-status<br />
 266     &lt;Location /server-status&gt;<br />
 267     <span class="indent">
 268       PolicyFilter off<br />
 269     </span>
 270     &lt;/Location&gt;<br />
 271     </code></p></div>
 272
 273 </div>
 274 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 275 <div class="directive-section"><h2><a name="PolicyConditional" id="PolicyConditional">PolicyConditional</a> <a name="policyconditional" id="policyconditional">Directive</a></h2>
 276 <table class="directive">
 277 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the conditional request policy.</td></tr>
 278 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyConditional <var>ignore|log|enforce</var></code></td></tr>
 279 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 280 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 281 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 282 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 283 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyConditional is only available in Apache 2.5.0 and
 284 later.</td></tr>
 285 </table>
 286     <p>When logged or enforced, a response that should have been conditional
 287     but wasn't will be rejected.</p>
 288
 289     <div class="example"><h3>Example</h3><p><code>
 290     # non-functional conditional responses should be rejected<br />
 291     PolicyConditional enforce<br />
 292     </code></p></div>
 293
 294 </div>
 295 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 296 <div class="directive-section"><h2><a name="PolicyConditionalURL" id="PolicyConditionalURL">PolicyConditionalURL</a> <a name="policyconditionalurl" id="policyconditionalurl">Directive</a></h2>
 297 <table class="directive">
 298 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the conditional request policy.</td></tr>
 299 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyConditionalURL <var>url</var></code></td></tr>
 300 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 301 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 302 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 303 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 304 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyConditionalURL is only available in Apache 2.5.0 and
 305 later.</td></tr>
 306 </table>
 307     <p>Specify the URL of the documentation describing the conditional
 308     request policy, to appear within error messages.</p>
 309
 310 </div>
 311 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 312 <div class="directive-section"><h2><a name="PolicyEnvironment" id="PolicyEnvironment">PolicyEnvironment</a> <a name="policyenvironment" id="policyenvironment">Directive</a></h2>
 313 <table class="directive">
 314 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Override policies based on an environment variable.</td></tr>
 315 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyEnvironment <var>variable</var> <var>log-value</var> <var>ignore-value</var></code></td></tr>
 316 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 317 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 318 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 319 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 320 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyEnvironment is only available in Apache 2.5.0 and
 321 later.</td></tr>
 322 </table>
 323     <p>Downgrade policies to logging only or ignored based on the presence
 324     of an environment variable. If the given variable is present and equal
 325     to the log-value, enforced policies will be logged instead. If the given
 326     variable is present and equal to the ignore-value, all policies will
 327     be ignored.</p>
 328
 329     <div class="example"><h3>Example</h3><p><code>
 330     # downgrade if POLICY_CONTROL was present<br />
 331     PolicyEnvironment POLICY_CONTROL log ignore<br />
 332     </code></p></div>
 333
 334 </div>
 335 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 336 <div class="directive-section"><h2><a name="PolicyFilter" id="PolicyFilter">PolicyFilter</a> <a name="policyfilter" id="policyfilter">Directive</a></h2>
 337 <table class="directive">
 338 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable or disable policies for the given URL space.</td></tr>
 339 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyFilter <var>on|off</var></code></td></tr>
 340 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>on</code></td></tr>
 341 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 342 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 343 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 344 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyFilter is only available in Apache 2.5.0 and
 345 later.</td></tr>
 346 </table>
 347     <p>Master switch to enable or disable policies for a given URL space.</p>
 348
 349     <div class="example"><h3>Example</h3><p><code>
 350     # enabled by default<br />
 351     &lt;Location /&gt;<br />
 352     <span class="indent">
 353       PolicyFilter on<br />
 354     </span>
 355     &lt;/Location&gt;<br />
 356     <br />
 357     # suppress policy protection for server-status<br />
 358     &lt;Location /server-status&gt;<br />
 359     <span class="indent">
 360       PolicyFilter off<br />
 361     </span>
 362     &lt;/Location&gt;<br />
 363     </code></p></div>
 364
 365 </div>
 366 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 367 <div class="directive-section"><h2><a name="PolicyKeepalive" id="PolicyKeepalive">PolicyKeepalive</a> <a name="policykeepalive" id="policykeepalive">Directive</a></h2>
 368 <table class="directive">
 369 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the keepalive policy.</td></tr>
 370 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyKeepalive <var>ignore|log|enforce</var></code></td></tr>
 371 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 372 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 373 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 374 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 375 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyKeepalive is only available in Apache 2.5.0 and
 376 later.</td></tr>
 377 </table>
 378     <p>When logged or enforced, a response that lacks both an explicit
 379     <code>Content-Length</code> header and a <code>Transfer-Encoding</code>
 380     of <code>chunked</code> will be rejected.</p>
 381
 382     <div class="example"><h3>Example</h3><p><code>
 383     # missing Content-Length or Transfer-Encoding should be rejected<br />
 384     PolicyKeepalive enforce<br />
 385     </code></p></div>
 386
 387 </div>
 388 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 389 <div class="directive-section"><h2><a name="PolicyKeepaliveURL" id="PolicyKeepaliveURL">PolicyKeepaliveURL</a> <a name="policykeepaliveurl" id="policykeepaliveurl">Directive</a></h2>
 390 <table class="directive">
 391 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the keepalive policy.</td></tr>
 392 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyKeepaliveURL <var>url</var></code></td></tr>
 393 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 394 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 395 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 396 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 397 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyKeepaliveURL is only available in Apache 2.5.0 and
 398 later.</td></tr>
 399 </table>
 400     <p>Specify the URL of the documentation describing the keepalive
 401     policy, to appear within error messages.</p>
 402
 403 </div>
 404 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 405 <div class="directive-section"><h2><a name="PolicyLength" id="PolicyLength">PolicyLength</a> <a name="policylength" id="policylength">Directive</a></h2>
 406 <table class="directive">
 407 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the content length policy.</td></tr>
 408 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyLength <var>ignore|log|enforce</var></code></td></tr>
 409 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 410 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 411 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 412 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 413 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyLength is only available in Apache 2.5.0 and
 414 later.</td></tr>
 415 </table>
 416     <p>When logged or enforced, a response that lacks an explicit
 417     <code>Content-Length</code> header will be rejected.</p>
 418
 419     <div class="example"><h3>Example</h3><p><code>
 420     # missing Content-Length header should be rejected<br />
 421     PolicyLength enforce<br />
 422     </code></p></div>
 423
 424 </div>
 425 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 426 <div class="directive-section"><h2><a name="PolicyLengthURL" id="PolicyLengthURL">PolicyLengthURL</a> <a name="policylengthurl" id="policylengthurl">Directive</a></h2>
 427 <table class="directive">
 428 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content length policy.</td></tr>
 429 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyLengthURL <var>url</var></code></td></tr>
 430 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 431 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 432 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 433 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 434 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyLengthURL is only available in Apache 2.5.0 and
 435 later.</td></tr>
 436 </table>
 437     <p>Specify the URL of the documentation describing the content length
 438     policy, to appear within error messages.</p>
 439
 440 </div>
 441 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 442 <div class="directive-section"><h2><a name="PolicyMaxage" id="PolicyMaxage">PolicyMaxage</a> <a name="policymaxage" id="policymaxage">Directive</a></h2>
 443 <table class="directive">
 444 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the caching minimum max-age policy.</td></tr>
 445 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyMaxage <var>ignore|log|enforce</var> <var>age</var></code></td></tr>
 446 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 447 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 448 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 449 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 450 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyMaxage is only available in Apache 2.5.0 and
 451 later.</td></tr>
 452 </table>
 453     <p>When logged or enforced, a response that lacks an explicit freshness
 454     lifetime defined with <code>max-age</code>, <code>s-maxage</code> or an
 455     <code>Expires</code> header, or where the explicit freshness lifetime is
 456     smaller than the given value, will be rejected.</p>
 457
 458     <div class="example"><h3>Example</h3><p><code>
 459     # reject responses with a freshness lifetime shorter than a day<br />
 460     PolicyMaxage enforce 86400<br />
 461     </code></p></div>
 462
 463
 464 </div>
 465 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 466 <div class="directive-section"><h2><a name="PolicyMaxageURL" id="PolicyMaxageURL">PolicyMaxageURL</a> <a name="policymaxageurl" id="policymaxageurl">Directive</a></h2>
 467 <table class="directive">
 468 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the caching minimum freshness lifetime policy.</td></tr>
 469 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyMaxageURL <var>url</var></code></td></tr>
 470 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 471 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 472 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 473 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 474 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyMaxageURL is only available in Apache 2.5.0 and
 475 later.</td></tr>
 476 </table>
 477     <p>Specify the URL of the documentation describing the caching minimum
 478     freshness lifetime policy, to appear within error messages.</p>
 479
 480 </div>
 481 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 482 <div class="directive-section"><h2><a name="PolicyNocache" id="PolicyNocache">PolicyNocache</a> <a name="policynocache" id="policynocache">Directive</a></h2>
 483 <table class="directive">
 484 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the caching no-cache policy.</td></tr>
 485 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyNocache <var>ignore|log|enforce</var></code></td></tr>
 486 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 487 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 488 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 489 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 490 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyNocache is only available in Apache 2.5.0 and
 491 later.</td></tr>
 492 </table>
 493     <p>When logged or enforced, a response that defines itself uncacheable
 494     using the <code>Cache-Control</code> or <code>Pragma</code> headers will
 495     be rejected.</p>
 496
 497     <div class="example"><h3>Example</h3><p><code>
 498     # Cache-Control: no-cache will be rejected<br />
 499     PolicyNocache enforce<br />
 500     </code></p></div>
 501
 502
 503 </div>
 504 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 505 <div class="directive-section"><h2><a name="PolicyNocacheURL" id="PolicyNocacheURL">PolicyNocacheURL</a> <a name="policynocacheurl" id="policynocacheurl">Directive</a></h2>
 506 <table class="directive">
 507 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the caching no-cache policy.</td></tr>
 508 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyNocacheURL <var>url</var></code></td></tr>
 509 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 510 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 511 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 512 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 513 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyNocacheURL is only available in Apache 2.5.0 and
 514 later.</td></tr>
 515 </table>
 516     <p>Specify the URL of the documentation describing the caching no-cache
 517     policy, to appear within error messages.</p>
 518
 519 </div>
 520 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 521 <div class="directive-section"><h2><a name="PolicyType" id="PolicyType">PolicyType</a> <a name="policytype" id="policytype">Directive</a></h2>
 522 <table class="directive">
 523 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the content type policy.</td></tr>
 524 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyType <var>ignore|log|enforce</var> <var>type</var> [ <var>type</var> [ ... ]]</code></td></tr>
 525 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 526 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 527 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 528 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 529 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyType is only available in Apache 2.5.0 and
 530 later.</td></tr>
 531 </table>
 532     <p>When logged or enforced, a response that lacks a <code>Content-Type</code>
 533     header, where the <code>Content-Type</code> header is malformed, or where the
 534     header does not match the given pattern or patterns will be rejected.</p>
 535
 536     <div class="example"><h3>Example</h3><p><code>
 537     # enforce json or XML<br />
 538     PolicyType enforce application/json text/xml<br />
 539     </code></p></div>
 540
 541     <div class="example"><h3>Example</h3><p><code>
 542     # malformed content type should be rejected<br />
 543     PolicyType enforce */*<br />
 544     </code></p></div>
 545
 546
 547 </div>
 548 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 549 <div class="directive-section"><h2><a name="PolicyTypeURL" id="PolicyTypeURL">PolicyTypeURL</a> <a name="policytypeurl" id="policytypeurl">Directive</a></h2>
 550 <table class="directive">
 551 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content type policy.</td></tr>
 552 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyTypeURL <var>url</var></code></td></tr>
 553 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 554 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 555 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 556 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 557 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyTypeURL is only available in Apache 2.5.0 and
 558 later.</td></tr>
 559 </table>
 560     <p>Specify the URL of the documentation describing the content type
 561     policy, to appear within error messages.</p>
 562
 563 </div>
 564 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 565 <div class="directive-section"><h2><a name="PolicyValidation" id="PolicyValidation">PolicyValidation</a> <a name="policyvalidation" id="policyvalidation">Directive</a></h2>
 566 <table class="directive">
 567 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the validation policy.</td></tr>
 568 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyValidation <var>ignore|log|enforce</var></code></td></tr>
 569 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 570 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 571 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 572 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 573 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyValidation is only available in Apache 2.5.0 and
 574 later.</td></tr>
 575 </table>
 576     <p>When logged or enforced, a response that lacks either a valid
 577     <code>ETag</code> header or a <code>Last-Modified</code> header, or where
 578     either header is syntactically incorrect, will be rejected.</p>
 579
 580     <div class="example"><h3>Example</h3><p><code>
 581     # no ETag or Last-Modified will be rejected<br />
 582     PolicyValidation enforce<br />
 583     </code></p></div>
 584
 585
 586 </div>
 587 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 588 <div class="directive-section"><h2><a name="PolicyValidationURL" id="PolicyValidationURL">PolicyValidationURL</a> <a name="policyvalidationurl" id="policyvalidationurl">Directive</a></h2>
 589 <table class="directive">
 590 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content type policy.</td></tr>
 591 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyValidationURL <var>url</var></code></td></tr>
 592 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 593 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 594 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 595 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 596 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyValidationURL is only available in Apache 2.5.0 and
 597 later.</td></tr>
 598 </table>
 599     <p>Specify the URL of the documentation describing the validation policy, to
 600     appear within error messages.</p>
 601
 602 </div>
 603 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 604 <div class="directive-section"><h2><a name="PolicyVary" id="PolicyVary">PolicyVary</a> <a name="policyvary" id="policyvary">Directive</a></h2>
 605 <table class="directive">
 606 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the Vary policy.</td></tr>
 607 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyVary <var>ignore|log|enforce</var> <var>header</var> [ <var>header</var> [ ... ]]</code></td></tr>
 608 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 609 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 610 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 611 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 612 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVary is only available in Apache 2.5.0 and
 613 later.</td></tr>
 614 </table>
 615     <p>When logged or enforced, a response that contains a <code>Vary</code>
 616     header which in turn contains one of the headers listed, will be
 617     rejected.</p>
 618
 619     <div class="example"><h3>Example</h3><p><code>
 620     # reject reponses with "User-Agent" listed in the Vary header<br />
 621     PolicyVary enforce User-Agent<br />
 622     </code></p></div>
 623
 624
 625 </div>
 626 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 627 <div class="directive-section"><h2><a name="PolicyVaryURL" id="PolicyVaryURL">PolicyVaryURL</a> <a name="policyvaryurl" id="policyvaryurl">Directive</a></h2>
 628 <table class="directive">
 629 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content type policy.</td></tr>
 630 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyVaryURL <var>url</var></code></td></tr>
 631 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 632 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 633 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 634 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 635 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVaryURL is only available in Apache 2.5.0 and
 636 later.</td></tr>
 637 </table>
 638     <p>Specify the URL of the documentation describing the vary policy, to
 639     appear within error messages.</p>
 640
 641 </div>
 642 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 643 <div class="directive-section"><h2><a name="PolicyVersion" id="PolicyVersion">PolicyVersion</a> <a name="policyversion" id="policyversion">Directive</a></h2>
 644 <table class="directive">
 645 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the version policy.</td></tr>
 646 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyVersion <var>ignore|log|enforce</var> <var>HTTP/0.9|HTTP/1.0|HTTP/1.1</var></code></td></tr>
 647 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 648 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 649 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 650 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 651 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVersion is only available in Apache 2.5.0 and
 652 later.</td></tr>
 653 </table>
 654     <p>When logged or enforced, a request with a version lower than specified
 655     will be rejected.</p>
 656
 657     <div class="example"><h3>Example</h3><p><code>
 658     # reject requests with an HTTP version older than HTTP/1.1<br />
 659     PolicyVersion enforce HTTP/1.1<br />
 660     </code></p></div>
 661
 662
 663 </div>
 664 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 665 <div class="directive-section"><h2><a name="PolicyVersionURL" id="PolicyVersionURL">PolicyVersionURL</a> <a name="policyversionurl" id="policyversionurl">Directive</a></h2>
 666 <table class="directive">
 667 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the minimum request HTTP version policy.</td></tr>
 668 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyVersionURL <var>url</var></code></td></tr>
 669 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 670 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 671 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 672 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 673 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVersionURL is only available in Apache 2.5.0 and
 674 later.</td></tr>
 675 </table>
 676     <p>Specify the URL of the documentation describing the minimum request
 677     HTTP version policy, to appear within error messages.</p>
 678
 679 </div>
 680 </div>
 681 <div class="bottomlang">
 682 <p><span>Available Languages: </span><a href="../en/mod/mod_policy.html" title="English">&nbsp;en&nbsp;</a></p>
 683 </div><div id="footer">
 684 <p class="apache">Copyright 2011 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
 685 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
 686 </body></html>