granicus.if.org Git - apache/blob - docs/manual/mod/mod_policy.html.en

   1 <?xml version="1.0" encoding="ISO-8859-1"?>
   2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
   3 <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
   4         XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
   5               This file is generated from xml source: DO NOT EDIT
   6         XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
   7       -->
   8 <title>mod_policy - Apache HTTP Server</title>
   9 <link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
  10 <link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
  11 <link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" />
  12 <script src="../style/scripts/prettify.js" type="text/javascript">
  13 </script>
  14
  15 <link href="../images/favicon.ico" rel="shortcut icon" /></head>
  16 <body>
  17 <div id="page-header">
  18 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
  19 <p class="apache">Apache HTTP Server Version 2.5</p>
  20 <img alt="" src="../images/feather.gif" /></div>
  21 <div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
  22 <div id="path">
  23 <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>
  24 <div id="page-content">
  25 <div id="preamble"><h1>Apache Module mod_policy</h1>
  26 <div class="toplang">
  27 <p><span>Available Languages: </span><a href="../en/mod/mod_policy.html" title="English">&nbsp;en&nbsp;</a></p>
  28 </div>
  29 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>HTTP protocol compliance enforcement.</td></tr>
  30 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  31 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>policy_module</td></tr>
  32 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_policy.c</td></tr></table>
  33 <h3>Summary</h3>
  34
  35     <p>The HTTP protocol recommends that clients should be "liberal in
  36     what they accept", and servers "strict with what they send". In some
  37     cases it can be difficult to detect when a server or an application
  38     has been misconfigured, is serving uncacheable content or is behaving
  39     suboptimally, as an HTTP client might be compensating for the server.
  40     These problems can potentially lead to excessive bandwidth
  41     consumption, or a server outage under load.</p>
  42
  43     <p>The <code class="module"><a href="../mod/mod_policy.html">mod_policy</a></code> module consists of a set of
  44     filters that test servers for HTTP protocol compliance. These
  45     tests allow the server administrator to log violations of, or
  46     outright reject responses where certain defined conditions exist.</p>
  47
  48     <p>This could be used as a way to set minimum HTTP protocol compliance
  49     criteria for a restful application. Alternatively, a reverse proxy or
  50     cache could be configured to protect itself from misconfigured origin
  51     servers or unexpectedly uncacheable content, or as a mechanism to
  52     detect configuration mistakes within the server itself.</p>
  53
  54 </div>
  55 <div id="quickview"><h3 class="directives">Directives</h3>
  56 <ul id="toc">
  57 <li><img alt="" src="../images/down.gif" /> <a href="#policyconditional">PolicyConditional</a></li>
  58 <li><img alt="" src="../images/down.gif" /> <a href="#policyconditionalurl">PolicyConditionalURL</a></li>
  59 <li><img alt="" src="../images/down.gif" /> <a href="#policyenvironment">PolicyEnvironment</a></li>
  60 <li><img alt="" src="../images/down.gif" /> <a href="#policyfilter">PolicyFilter</a></li>
  61 <li><img alt="" src="../images/down.gif" /> <a href="#policykeepalive">PolicyKeepalive</a></li>
  62 <li><img alt="" src="../images/down.gif" /> <a href="#policykeepaliveurl">PolicyKeepaliveURL</a></li>
  63 <li><img alt="" src="../images/down.gif" /> <a href="#policylength">PolicyLength</a></li>
  64 <li><img alt="" src="../images/down.gif" /> <a href="#policylengthurl">PolicyLengthURL</a></li>
  65 <li><img alt="" src="../images/down.gif" /> <a href="#policymaxage">PolicyMaxage</a></li>
  66 <li><img alt="" src="../images/down.gif" /> <a href="#policymaxageurl">PolicyMaxageURL</a></li>
  67 <li><img alt="" src="../images/down.gif" /> <a href="#policynocache">PolicyNocache</a></li>
  68 <li><img alt="" src="../images/down.gif" /> <a href="#policynocacheurl">PolicyNocacheURL</a></li>
  69 <li><img alt="" src="../images/down.gif" /> <a href="#policytype">PolicyType</a></li>
  70 <li><img alt="" src="../images/down.gif" /> <a href="#policytypeurl">PolicyTypeURL</a></li>
  71 <li><img alt="" src="../images/down.gif" /> <a href="#policyvalidation">PolicyValidation</a></li>
  72 <li><img alt="" src="../images/down.gif" /> <a href="#policyvalidationurl">PolicyValidationURL</a></li>
  73 <li><img alt="" src="../images/down.gif" /> <a href="#policyvary">PolicyVary</a></li>
  74 <li><img alt="" src="../images/down.gif" /> <a href="#policyvaryurl">PolicyVaryURL</a></li>
  75 <li><img alt="" src="../images/down.gif" /> <a href="#policyversion">PolicyVersion</a></li>
  76 <li><img alt="" src="../images/down.gif" /> <a href="#policyversionurl">PolicyVersionURL</a></li>
  77 </ul>
  78 <h3>Topics</h3>
  79 <ul id="topics">
  80 <li><img alt="" src="../images/down.gif" /> <a href="#actions">Actions</a></li>
  81 <li><img alt="" src="../images/down.gif" /> <a href="#tests">Policy Tests</a></li>
  82 <li><img alt="" src="../images/down.gif" /> <a href="#example">Example Configuration</a></li>
  83 </ul><h3>See also</h3>
  84 <ul class="seealso">
  85 <li><a href="../filter.html">Filters</a></li>
  86 <li><a href="../compliance.html">HTTP Protocol Compliance</a></li>
  87 </ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
  88 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  89 <div class="section">
  90 <h2><a name="actions" id="actions">Actions</a></h2>
  91
  92
  93     <p>If a policy is violated, one of the following actions can be
  94     taken:</p>
  95
  96     <dl>
  97     <dt><strong>ignore</strong></dt>
  98     <dd>The policy check will be ignored for the given URL space, even
  99     if the filter is present.</dd>
 100
 101     <dt><strong>log</strong></dt>
 102     <dd>The policy check will be executed, and if a violation is detected
 103     a warning will be logged to the server error_log, and a
 104     <code>Warning</code> header added to the response for the benefit of
 105     the client.</dd>
 106
 107     <dt><strong>enforce</strong></dt>
 108     <dd>The policy check will be executed, and if a violation is detected
 109     an error will be logged to the server error_log, a
 110     <code>Warning</code> header added to the response, and a <code>502
 111     Bad Gateway</code> will be returned to the client. Optional links to
 112     explanatory documentation can be added to each error message,
 113     detailing the origin of each policy.</dd>
 114
 115     </dl>
 116
 117     <p>It is also possible to selectively disable all policies for a
 118     given URL space, should the need arise, using the
 119     <code class="directive"><a href="#policyfilter">PolicyFilter</a></code> directive.</p>
 120
 121     <p>Alternatively, the
 122     <code class="directive"><a href="#policyenvironment">PolicyEnvironment</a></code>
 123     directive can be used to specify an environment variable, which if
 124     present, will cause the policies to be selectively downgraded or
 125     bypassed.</p>
 126
 127 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 128 <div class="section">
 129 <h2><a name="tests" id="tests">Policy Tests</a></h2>
 130
 131
 132     <p>The following policy filters are available:</p>
 133
 134     <dl>
 135     <dt><strong><a href="../compliance.html#policytype">POLICY_TYPE</a>
 136     </strong>: Enforce valid content types</dt>
 137     <dd>Content types that are syntactically invalid or blank can be detected
 138         and the request rejected. Types can be restricted to a specific list
 139         containing optional wildcards ? and *.</dd>
 140
 141     <dt><strong><a href="../compliance.html#policylength">POLICY_LENGTH</a>
 142     </strong>: Enforce the presence of a Content-Length</dt>
 143     <dd>The length of responses can be specified in one of three ways, by
 144     specifying an explicit length in advance, using chunked encoding to set
 145     the length, or by setting no length at all and terminating the request
 146     when complete. The absence of a specific content length can affect the
 147     cacheability of the response, and prevents the use of keepalive during
 148     HTTP/1.0 requests. This policy enforces the presence of an explicit
 149     content length on the response.</dd>
 150
 151     <dt><strong><a href="../compliance.html#policykeepalive">POLICY_KEEPALIVE
 152     </a></strong>: Enforce the option to keepalive</dt>
 153     <dd>Less restrictive than the POLICY_LENGTH test, this policy enforces the
 154     possibility that the response can be kept alive. If the response doesn't
 155     have a protocol defined zero length, and the response isn't already an
 156     error, and the response has neither a Content-Length or is declared
 157     HTTP/1.1 and lacks Content-Encoding: chunked, then this response will be
 158     rejected.</dd>
 159
 160     <dt><strong><a href="../compliance.html#policyvary">POLICY_VARY</a>
 161     </strong>: Enforce the absence of certain headers within Vary headers</dt>
 162     <dd>If the Vary header contains any of the headers specified, this policy
 163     will reject the request. The typical case is the presence of the User-Agent
 164     within Vary, which is likely to cause a denial of service condition to a
 165     cache.</dd>
 166
 167     <dt><strong><a href="../compliance.html#policyvalidation">
 168     POLICY_VALIDATION</a></strong>: Enforce the presence of Etag and/or
 169     Last-Modified</dt>
 170     <dd>The ability for a cache to determine whether a cached entity can be
 171     refreshed is dependent on whether a valid Etag and/or Last-Modified header
 172     is present to revalidate against. The absence of both headers, or the
 173     invalid syntax of a header will cause this policy to be rejected.</dd>
 174
 175     <dt><strong><a href="../compliance.html#policyconditional">
 176     POLICY_CONDITIONAL</a></strong>: Enforce correct operation of conditional
 177     requests</dt>
 178     <dd>When conditional headers are present in the request, a server should
 179     respond with a <code>304 Not Modified</code> or <code>412 Precondition
 180     Failed</code> response where appropriate. A server may ignore conditional
 181     headers, and this affects the efficiency of the HTTP caching mechanism.
 182     This policy rejects requests where a conditional header is present, and
 183     a 304 or 412 response code was expected, but a 2xx response was seen
 184     instead.</dd>
 185
 186     <dt><strong><a href="../compliance.html#policynocache">POLICY_NOCACHE</a>
 187     </strong>: Enforce cacheable responses</dt>
 188     <dd>When a response is encountered that declares itself explicitly
 189     uncacheable, the request is rejected. A response is considered
 190     uncacheable if it specifies any of the following:
 191     <ul><li><code>Cache-Control: no-cache</code></li>
 192     <li><code>Pragma: no-cache</code></li>
 193     <li><code>Cache-Control: no-store</code></li>
 194     <li><code>Cache-Control: private</code></li>
 195     </ul></dd>
 196
 197     <dt><strong><a href="../compliance.html#policymaxage">POLICY_MAXAGE</a>
 198     </strong>: Enforce a minimum maxage</dt>
 199     <dd>When a response is encountered where the freshness lifetime is less
 200     than the given value, or the freshness lifetime is heuristic, the request
 201     is rejected. A response is checked in the following order:
 202     <ul><li>If <code>s-maxage</code> is present but too small; or</li>
 203     <li>If <code>max-age</code> is present but too small; or</li>
 204     <li>If <code>Expires</code> is present and invalid; or</li>
 205     <li><code>Date</code> is present and invalid; or</li>
 206     <li><code>Expires</code> minus Date is too small; or</li>
 207     <li>No <code>s-maxage</code>, <code>maxage</code>, or
 208     <code>Expires</code>/<code>Date</code> declared at all</li>
 209     </ul></dd>
 210
 211     <dt><strong><a href="../compliance.html#policyversion">POLICY_VERSION</a>
 212     </strong>: Enforce a minimum HTTP version within a request</dt>
 213     <dd>When a request is encountered with an HTTP version number less than
 214     the required minimum version, the request is rejected. The following
 215     version numbers are recognised:
 216     <ul><li><code>HTTP/1.1</code></li>
 217     <li><code>HTTP/1.0</code></li>
 218     <li><code>HTTP/0.9</code></li>
 219     </ul></dd>
 220
 221     </dl>
 222
 223 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 224 <div class="section">
 225 <h2><a name="example" id="example">Example Configuration</a></h2>
 226
 227
 228     <p>A typical configuration protecting a server serving static content
 229     might be as follows:</p>
 230
 231     <pre class="prettyprint lang-config">
 232 &lt;Location /&gt;
 233   SetOutputFilter POLICY_TYPE;POLICY_LENGTH;POLICY_KEEPALIVE;POLICY_VARY;POLICY_VALIDATION; \
 234     POLICY_CONDITIONAL;POLICY_NOCACHE;POLICY_MAXAGE;POLICY_VERSION
 235
 236   # content type must be present and valid, but can be anything
 237   PolicyType enforce */*
 238
 239   # reject if no explicitly declared content length
 240   PolicyLength enforce
 241
 242   # covered by the policy length filter
 243   PolicyKeepalive ignore
 244
 245   # reject if User-Agent appears within Vary headers
 246   PolicyVary enforce User-Agent
 247
 248   # we want to enforce validation
 249   PolicyValidation enforce
 250
 251   # non-functional conditional responses should be rejected
 252   PolicyConditional enforce
 253
 254   # no-cache responses should be rejected
 255   PolicyNocache enforce
 256
 257   # maxage must be at least a day
 258   PolicyMaxage enforce 86400
 259
 260   # request version can be anything
 261   PolicyVersion ignore HTTP/1.1
 262 &lt;/Location&gt;
 263
 264 # suppress policy protection for server-status
 265 &lt;Location /server-status&gt;
 266   PolicyFilter off
 267 &lt;/Location&gt;
 268     </pre>
 269
 270
 271 </div>
 272 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 273 <div class="directive-section"><h2><a name="PolicyConditional" id="PolicyConditional">PolicyConditional</a> <a name="policyconditional" id="policyconditional">Directive</a></h2>
 274 <table class="directive">
 275 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the conditional request policy.</td></tr>
 276 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyConditional <var>ignore|log|enforce</var></code></td></tr>
 277 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 278 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 279 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 280 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 281 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyConditional is only available in Apache 2.5.0 and
 282 later.</td></tr>
 283 </table>
 284     <p>When logged or enforced, a response that should have been conditional
 285     but wasn't will be rejected.</p>
 286
 287     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 288 # non-functional conditional responses should be rejected
 289 PolicyConditional enforce
 290     </pre>
 291 </div>
 292
 293 </div>
 294 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 295 <div class="directive-section"><h2><a name="PolicyConditionalURL" id="PolicyConditionalURL">PolicyConditionalURL</a> <a name="policyconditionalurl" id="policyconditionalurl">Directive</a></h2>
 296 <table class="directive">
 297 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the conditional request policy.</td></tr>
 298 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyConditionalURL <var>url</var></code></td></tr>
 299 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 300 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 301 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 302 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 303 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyConditionalURL is only available in Apache 2.5.0 and
 304 later.</td></tr>
 305 </table>
 306     <p>Specify the URL of the documentation describing the conditional
 307     request policy, to appear within error messages.</p>
 308
 309 </div>
 310 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 311 <div class="directive-section"><h2><a name="PolicyEnvironment" id="PolicyEnvironment">PolicyEnvironment</a> <a name="policyenvironment" id="policyenvironment">Directive</a></h2>
 312 <table class="directive">
 313 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Override policies based on an environment variable.</td></tr>
 314 <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>
 315 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 316 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 317 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 318 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 319 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyEnvironment is only available in Apache 2.5.0 and
 320 later.</td></tr>
 321 </table>
 322     <p>Downgrade policies to logging only or ignored based on the presence
 323     of an environment variable. If the given variable is present and equal
 324     to the log-value, enforced policies will be logged instead. If the given
 325     variable is present and equal to the ignore-value, all policies will
 326     be ignored.</p>
 327
 328     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 329 # downgrade if POLICY_CONTROL was present
 330 PolicyEnvironment POLICY_CONTROL log ignore
 331     </pre>
 332 </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><pre class="prettyprint lang-config">
 350 # enabled by default
 351 &lt;Location /&gt;
 352   PolicyFilter on
 353 &lt;/Location&gt;
 354
 355 # suppress policy protection for server-status
 356 &lt;Location /server-status&gt;
 357   PolicyFilter off
 358 &lt;/Location&gt;
 359 </pre>
 360 </div>
 361
 362 </div>
 363 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 364 <div class="directive-section"><h2><a name="PolicyKeepalive" id="PolicyKeepalive">PolicyKeepalive</a> <a name="policykeepalive" id="policykeepalive">Directive</a></h2>
 365 <table class="directive">
 366 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the keepalive policy.</td></tr>
 367 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyKeepalive <var>ignore|log|enforce</var></code></td></tr>
 368 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 369 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 370 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 371 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 372 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyKeepalive is only available in Apache 2.5.0 and
 373 later.</td></tr>
 374 </table>
 375     <p>When logged or enforced, a response that lacks both an explicit
 376     <code>Content-Length</code> header and a <code>Transfer-Encoding</code>
 377     of <code>chunked</code> will be rejected.</p>
 378
 379     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 380 # missing Content-Length or Transfer-Encoding should be rejected
 381 PolicyKeepalive enforce
 382 </pre>
 383 </div>
 384
 385 </div>
 386 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 387 <div class="directive-section"><h2><a name="PolicyKeepaliveURL" id="PolicyKeepaliveURL">PolicyKeepaliveURL</a> <a name="policykeepaliveurl" id="policykeepaliveurl">Directive</a></h2>
 388 <table class="directive">
 389 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the keepalive policy.</td></tr>
 390 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyKeepaliveURL <var>url</var></code></td></tr>
 391 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 392 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 393 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 394 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 395 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyKeepaliveURL is only available in Apache 2.5.0 and
 396 later.</td></tr>
 397 </table>
 398     <p>Specify the URL of the documentation describing the keepalive
 399     policy, to appear within error messages.</p>
 400
 401 </div>
 402 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 403 <div class="directive-section"><h2><a name="PolicyLength" id="PolicyLength">PolicyLength</a> <a name="policylength" id="policylength">Directive</a></h2>
 404 <table class="directive">
 405 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the content length policy.</td></tr>
 406 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyLength <var>ignore|log|enforce</var></code></td></tr>
 407 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 408 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 409 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 410 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 411 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyLength is only available in Apache 2.5.0 and
 412 later.</td></tr>
 413 </table>
 414     <p>When logged or enforced, a response that lacks an explicit
 415     <code>Content-Length</code> header will be rejected.</p>
 416
 417     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 418 # missing Content-Length header should be rejected
 419 PolicyLength enforce
 420     </pre>
 421 </div>
 422
 423 </div>
 424 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 425 <div class="directive-section"><h2><a name="PolicyLengthURL" id="PolicyLengthURL">PolicyLengthURL</a> <a name="policylengthurl" id="policylengthurl">Directive</a></h2>
 426 <table class="directive">
 427 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content length policy.</td></tr>
 428 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyLengthURL <var>url</var></code></td></tr>
 429 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 430 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 431 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 432 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 433 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyLengthURL is only available in Apache 2.5.0 and
 434 later.</td></tr>
 435 </table>
 436     <p>Specify the URL of the documentation describing the content length
 437     policy, to appear within error messages.</p>
 438
 439 </div>
 440 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 441 <div class="directive-section"><h2><a name="PolicyMaxage" id="PolicyMaxage">PolicyMaxage</a> <a name="policymaxage" id="policymaxage">Directive</a></h2>
 442 <table class="directive">
 443 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the caching minimum max-age policy.</td></tr>
 444 <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>
 445 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 446 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 447 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 448 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 449 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyMaxage is only available in Apache 2.5.0 and
 450 later.</td></tr>
 451 </table>
 452     <p>When logged or enforced, a response that lacks an explicit freshness
 453     lifetime defined with <code>max-age</code>, <code>s-maxage</code> or an
 454     <code>Expires</code> header, or where the explicit freshness lifetime is
 455     smaller than the given value, will be rejected.</p>
 456
 457     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 458 # reject responses with a freshness lifetime shorter than a day
 459 PolicyMaxage enforce 86400
 460     </pre>
 461 </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><pre class="prettyprint lang-config">
 498 # Cache-Control: no-cache will be rejected
 499 PolicyNocache enforce
 500     </pre>
 501 </div>
 502
 503
 504 </div>
 505 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 506 <div class="directive-section"><h2><a name="PolicyNocacheURL" id="PolicyNocacheURL">PolicyNocacheURL</a> <a name="policynocacheurl" id="policynocacheurl">Directive</a></h2>
 507 <table class="directive">
 508 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the caching no-cache policy.</td></tr>
 509 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyNocacheURL <var>url</var></code></td></tr>
 510 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 511 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 512 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 513 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 514 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyNocacheURL is only available in Apache 2.5.0 and
 515 later.</td></tr>
 516 </table>
 517     <p>Specify the URL of the documentation describing the caching no-cache
 518     policy, to appear within error messages.</p>
 519
 520 </div>
 521 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 522 <div class="directive-section"><h2><a name="PolicyType" id="PolicyType">PolicyType</a> <a name="policytype" id="policytype">Directive</a></h2>
 523 <table class="directive">
 524 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the content type policy.</td></tr>
 525 <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>
 526 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 527 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 528 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 529 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 530 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyType is only available in Apache 2.5.0 and
 531 later.</td></tr>
 532 </table>
 533     <p>When logged or enforced, a response that lacks a <code>Content-Type</code>
 534     header, where the <code>Content-Type</code> header is malformed, or where the
 535     header does not match the given pattern or patterns will be rejected.</p>
 536
 537     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 538 # enforce json or XML
 539 PolicyType enforce application/json text/xml
 540     </pre>
 541 </div>
 542
 543     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 544 # malformed content type should be rejected
 545 PolicyType enforce */*
 546     </pre>
 547 </div>
 548
 549
 550 </div>
 551 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 552 <div class="directive-section"><h2><a name="PolicyTypeURL" id="PolicyTypeURL">PolicyTypeURL</a> <a name="policytypeurl" id="policytypeurl">Directive</a></h2>
 553 <table class="directive">
 554 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content type policy.</td></tr>
 555 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyTypeURL <var>url</var></code></td></tr>
 556 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 557 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 558 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 559 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 560 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyTypeURL is only available in Apache 2.5.0 and
 561 later.</td></tr>
 562 </table>
 563     <p>Specify the URL of the documentation describing the content type
 564     policy, to appear within error messages.</p>
 565
 566 </div>
 567 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 568 <div class="directive-section"><h2><a name="PolicyValidation" id="PolicyValidation">PolicyValidation</a> <a name="policyvalidation" id="policyvalidation">Directive</a></h2>
 569 <table class="directive">
 570 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the validation policy.</td></tr>
 571 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyValidation <var>ignore|log|enforce</var></code></td></tr>
 572 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 573 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 574 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 575 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 576 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyValidation is only available in Apache 2.5.0 and
 577 later.</td></tr>
 578 </table>
 579     <p>When logged or enforced, a response that lacks either a valid
 580     <code>ETag</code> header or a <code>Last-Modified</code> header, or where
 581     either header is syntactically incorrect, will be rejected.</p>
 582
 583     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 584 # no ETag or Last-Modified will be rejected
 585 PolicyValidation enforce
 586     </pre>
 587 </div>
 588
 589
 590 </div>
 591 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 592 <div class="directive-section"><h2><a name="PolicyValidationURL" id="PolicyValidationURL">PolicyValidationURL</a> <a name="policyvalidationurl" id="policyvalidationurl">Directive</a></h2>
 593 <table class="directive">
 594 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content type policy.</td></tr>
 595 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyValidationURL <var>url</var></code></td></tr>
 596 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 597 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 598 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 599 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 600 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyValidationURL is only available in Apache 2.5.0 and
 601 later.</td></tr>
 602 </table>
 603     <p>Specify the URL of the documentation describing the validation policy, to
 604     appear within error messages.</p>
 605
 606 </div>
 607 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 608 <div class="directive-section"><h2><a name="PolicyVary" id="PolicyVary">PolicyVary</a> <a name="policyvary" id="policyvary">Directive</a></h2>
 609 <table class="directive">
 610 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the Vary policy.</td></tr>
 611 <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>
 612 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 613 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 614 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 615 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 616 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVary is only available in Apache 2.5.0 and
 617 later.</td></tr>
 618 </table>
 619     <p>When logged or enforced, a response that contains a <code>Vary</code>
 620     header which in turn contains one of the headers listed, will be
 621     rejected.</p>
 622
 623     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 624 # reject reponses with "User-Agent" listed in the Vary header
 625 PolicyVary enforce User-Agent
 626     </pre>
 627 </div>
 628
 629
 630 </div>
 631 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 632 <div class="directive-section"><h2><a name="PolicyVaryURL" id="PolicyVaryURL">PolicyVaryURL</a> <a name="policyvaryurl" id="policyvaryurl">Directive</a></h2>
 633 <table class="directive">
 634 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content type policy.</td></tr>
 635 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyVaryURL <var>url</var></code></td></tr>
 636 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 637 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 638 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 639 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 640 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVaryURL is only available in Apache 2.5.0 and
 641 later.</td></tr>
 642 </table>
 643     <p>Specify the URL of the documentation describing the vary policy, to
 644     appear within error messages.</p>
 645
 646 </div>
 647 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 648 <div class="directive-section"><h2><a name="PolicyVersion" id="PolicyVersion">PolicyVersion</a> <a name="policyversion" id="policyversion">Directive</a></h2>
 649 <table class="directive">
 650 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the version policy.</td></tr>
 651 <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>
 652 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
 653 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 654 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 655 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 656 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVersion is only available in Apache 2.5.0 and
 657 later.</td></tr>
 658 </table>
 659     <p>When logged or enforced, a request with a version lower than specified
 660     will be rejected.</p>
 661
 662     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 663 # reject requests with an HTTP version older than HTTP/1.1
 664 PolicyVersion enforce HTTP/1.1
 665     </pre>
 666 </div>
 667
 668
 669 </div>
 670 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 671 <div class="directive-section"><h2><a name="PolicyVersionURL" id="PolicyVersionURL">PolicyVersionURL</a> <a name="policyversionurl" id="policyversionurl">Directive</a></h2>
 672 <table class="directive">
 673 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the minimum request HTTP version policy.</td></tr>
 674 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyVersionURL <var>url</var></code></td></tr>
 675 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
 676 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
 677 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 678 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
 679 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVersionURL is only available in Apache 2.5.0 and
 680 later.</td></tr>
 681 </table>
 682     <p>Specify the URL of the documentation describing the minimum request
 683     HTTP version policy, to appear within error messages.</p>
 684
 685 </div>
 686 </div>
 687 <div class="bottomlang">
 688 <p><span>Available Languages: </span><a href="../en/mod/mod_policy.html" title="English">&nbsp;en&nbsp;</a></p>
 689 </div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>This section is experimental!</strong><br />Comments placed here should not be expected
 690 to last beyond the testing phase of this system, nor do we in any way guarantee that we'll read them.</div>
 691 <div id="disqus_thread">
 692 </div><script type="text/javascript"><!--//--><![CDATA[//><!--
 693 var lang = 'en';
 694 var disqus_shortname = 'httpd';
 695 var disqus_identifier = window.location.href.replace(/(current|trunk)/, "2.4").replace(/\/[a-z]{2}\//, "/").replace(window.location.protocol, "http:") + '.' + lang;
 696 if (disqus_identifier.indexOf("httpd.apache.org") != -1) {
 697     (function() {
 698                 var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true;
 699                 dsq.src = window.location.protocol + '//' + disqus_shortname + '.disqus.com/embed.js';
 700             (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq);
 701         })();
 702 } else {
 703     var text = document.createTextNode("Comments have been disabled for offline viewing.");
 704     document.getElementById('disqus_thread').appendChild(text);
 705 }
 706 //--><!]]></script></div><div id="footer">
 707 <p class="apache">Copyright 2012 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>
 708 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div><script type="text/javascript"><!--//--><![CDATA[//><!--
 709 if (typeof(prettyPrint) !== undefined) {
 710     prettyPrint();
 711 }
 712 //--><!]]></script>
 713 </body></html>