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|
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<title>mod_policy - Apache HTTP Server</title>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.5</a> > <a href="./">Modules</a></div>
<div id="page-content">
<div id="preamble"><h1>Apache Module mod_policy</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/mod/mod_policy.html" title="English"> en </a></p>
</div>
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>HTTP protocol compliance enforcement.</td></tr>
<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>policy_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>mod_policy.c</td></tr></table>
<h3>Summary</h3>
<p>The HTTP protocol recommends that clients should be "liberal in
what they accept", and servers "strict with what they send". In some
cases it can be difficult to detect when a server or an application
has been misconfigured, is serving uncacheable content or is behaving
suboptimally, as an HTTP client might be compensating for the server.
These problems can potentially lead to excessive bandwidth
consumption, or a server outage under load.</p>
<p>The <code class="module"><a href="../mod/mod_policy.html">mod_policy</a></code> module consists of a set of
filters that test servers for HTTP protocol compliance. These
tests allow the server administrator to log violations of, or
outright reject responses where certain defined conditions exist.</p>
<p>This could be used as a way to set minimum HTTP protocol compliance
criteria for a restful application. Alternatively, a reverse proxy or
cache could be configured to protect itself from misconfigured origin
servers or unexpectedly uncacheable content, or as a mechanism to
detect configuration mistakes within the server itself.</p>
</div>
<div id="quickview"><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/down.gif" /> <a href="#policyconditional">PolicyConditional</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policyconditionalurl">PolicyConditionalURL</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policyenvironment">PolicyEnvironment</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policyfilter">PolicyFilter</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policykeepalive">PolicyKeepalive</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policykeepaliveurl">PolicyKeepaliveURL</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policylength">PolicyLength</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policylengthurl">PolicyLengthURL</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policymaxage">PolicyMaxage</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policymaxageurl">PolicyMaxageURL</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policynocache">PolicyNocache</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policynocacheurl">PolicyNocacheURL</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policytype">PolicyType</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policytypeurl">PolicyTypeURL</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policyvalidation">PolicyValidation</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policyvalidationurl">PolicyValidationURL</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policyvary">PolicyVary</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policyvaryurl">PolicyVaryURL</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policyversion">PolicyVersion</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#policyversionurl">PolicyVersionURL</a></li>
</ul>
<h3>Topics</h3>
<ul id="topics">
<li><img alt="" src="../images/down.gif" /> <a href="#actions">Actions</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#tests">Policy Tests</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#example">Example Configuration</a></li>
</ul><h3>See also</h3>
<ul class="seealso">
<li><a href="../filter.html">Filters</a></li>
<li><a href="../compliance.html">HTTP Protocol Compliance</a></li>
</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="actions" id="actions">Actions</a></h2>
<p>If a policy is violated, one of the following actions can be
taken:</p>
<dl>
<dt><strong>ignore</strong></dt>
<dd>The policy check will be ignored for the given URL space, even
if the filter is present.</dd>
<dt><strong>log</strong></dt>
<dd>The policy check will be executed, and if a violation is detected
a warning will be logged to the server error_log, and a
<code>Warning</code> header added to the response for the benefit of
the client.</dd>
<dt><strong>enforce</strong></dt>
<dd>The policy check will be executed, and if a violation is detected
an error will be logged to the server error_log, a
<code>Warning</code> header added to the response, and a <code>502
Bad Gateway</code> will be returned to the client. Optional links to
explanatory documentation can be added to each error message,
detailing the origin of each policy.</dd>
</dl>
<p>It is also possible to selectively disable all policies for a
given URL space, should the need arise, using the
<code class="directive"><a href="#policyfilter">PolicyFilter</a></code> directive.</p>
<p>Alternatively, the
<code class="directive"><a href="#policyenvironment">PolicyEnvironment</a></code>
directive can be used to specify an environment variable, which if
present, will cause the policies to be selectively downgraded or
bypassed.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="tests" id="tests">Policy Tests</a></h2>
<p>The following policy filters are available:</p>
<dl>
<dt><strong><a href="../compliance.html#policytype">POLICY_TYPE</a>
</strong>: Enforce valid content types</dt>
<dd>Content types that are syntactically invalid or blank can be detected
and the request rejected. Types can be restricted to a specific list
containing optional wildcards ? and *.</dd>
<dt><strong><a href="../compliance.html#policylength">POLICY_LENGTH</a>
</strong>: Enforce the presence of a Content-Length</dt>
<dd>The length of responses can be specified in one of three ways, by
specifying an explicit length in advance, using chunked encoding to set
the length, or by setting no length at all and terminating the request
when complete. The absence of a specific content length can affect the
cacheability of the response, and prevents the use of keepalive during
HTTP/1.0 requests. This policy enforces the presence of an explicit
content length on the response.</dd>
<dt><strong><a href="../compliance.html#policykeepalive">POLICY_KEEPALIVE
</a></strong>: Enforce the option to keepalive</dt>
<dd>Less restrictive than the POLICY_LENGTH test, this policy enforces the
possibility that the response can be kept alive. If the response doesn't
have a protocol defined zero length, and the response isn't already an
error, and the response has neither a Content-Length or is declared
HTTP/1.1 and lacks Content-Encoding: chunked, then this response will be
rejected.</dd>
<dt><strong><a href="../compliance.html#policyvary">POLICY_VARY</a>
</strong>: Enforce the absence of certain headers within Vary headers</dt>
<dd>If the Vary header contains any of the headers specified, this policy
will reject the request. The typical case is the presence of the User-Agent
within Vary, which is likely to cause a denial of service condition to a
cache.</dd>
<dt><strong><a href="../compliance.html#policyvalidation">
POLICY_VALIDATION</a></strong>: Enforce the presence of Etag and/or
Last-Modified</dt>
<dd>The ability for a cache to determine whether a cached entity can be
refreshed is dependent on whether a valid Etag and/or Last-Modified header
is present to revalidate against. The absence of both headers, or the
invalid syntax of a header will cause this policy to be rejected.</dd>
<dt><strong><a href="../compliance.html#policyconditional">
POLICY_CONDITIONAL</a></strong>: Enforce correct operation of conditional
requests</dt>
<dd>When conditional headers are present in the request, a server should
respond with a <code>304 Not Modified</code> or <code>412 Precondition
Failed</code> response where appropriate. A server may ignore conditional
headers, and this affects the efficiency of the HTTP caching mechanism.
This policy rejects requests where a conditional header is present, and
a 304 or 412 response code was expected, but a 2xx response was seen
instead.</dd>
<dt><strong><a href="../compliance.html#policynocache">POLICY_NOCACHE</a>
</strong>: Enforce cacheable responses</dt>
<dd>When a response is encountered that declares itself explicitly
uncacheable, the request is rejected. A response is considered
uncacheable if it specifies any of the following:
<ul><li><code>Cache-Control: no-cache</code></li>
<li><code>Pragma: no-cache</code></li>
<li><code>Cache-Control: no-store</code></li>
<li><code>Cache-Control: private</code></li>
</ul></dd>
<dt><strong><a href="../compliance.html#policymaxage">POLICY_MAXAGE</a>
</strong>: Enforce a minimum maxage</dt>
<dd>When a response is encountered where the freshness lifetime is less
than the given value, or the freshness lifetime is heuristic, the request
is rejected. A response is checked in the following order:
<ul><li>If <code>s-maxage</code> is present but too small; or</li>
<li>If <code>max-age</code> is present but too small; or</li>
<li>If <code>Expires</code> is present and invalid; or</li>
<li><code>Date</code> is present and invalid; or</li>
<li><code>Expires</code> minus Date is too small; or</li>
<li>No <code>s-maxage</code>, <code>maxage</code>, or
<code>Expires</code>/<code>Date</code> declared at all</li>
</ul></dd>
<dt><strong><a href="../compliance.html#policyversion">POLICY_VERSION</a>
</strong>: Enforce a minimum HTTP version within a request</dt>
<dd>When a request is encountered with an HTTP version number less than
the required minimum version, the request is rejected. The following
version numbers are recognised:
<ul><li><code>HTTP/1.1</code></li>
<li><code>HTTP/1.0</code></li>
<li><code>HTTP/0.9</code></li>
</ul></dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="example" id="example">Example Configuration</a></h2>
<p>A typical configuration protecting a server serving static content
might be as follows:</p>
<pre class="prettyprint lang-config">
<Location />
SetOutputFilter POLICY_TYPE;POLICY_LENGTH;POLICY_KEEPALIVE;POLICY_VARY;POLICY_VALIDATION; \
POLICY_CONDITIONAL;POLICY_NOCACHE;POLICY_MAXAGE;POLICY_VERSION
# content type must be present and valid, but can be anything
PolicyType enforce */*
# reject if no explicitly declared content length
PolicyLength enforce
# covered by the policy length filter
PolicyKeepalive ignore
# reject if User-Agent appears within Vary headers
PolicyVary enforce User-Agent
# we want to enforce validation
PolicyValidation enforce
# non-functional conditional responses should be rejected
PolicyConditional enforce
# no-cache responses should be rejected
PolicyNocache enforce
# maxage must be at least a day
PolicyMaxage enforce 86400
# request version can be anything
PolicyVersion ignore HTTP/1.1
</Location>
# suppress policy protection for server-status
<Location /server-status>
PolicyFilter off
</Location>
</pre>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyConditional" id="PolicyConditional">PolicyConditional</a> <a name="policyconditional" id="policyconditional">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the conditional request policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyConditional <var>ignore|log|enforce</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyConditional is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>When logged or enforced, a response that should have been conditional
but wasn't will be rejected.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# non-functional conditional responses should be rejected
PolicyConditional enforce
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyConditionalURL" id="PolicyConditionalURL">PolicyConditionalURL</a> <a name="policyconditionalurl" id="policyconditionalurl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the conditional request policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyConditionalURL <var>url</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyConditionalURL is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Specify the URL of the documentation describing the conditional
request policy, to appear within error messages.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyEnvironment" id="PolicyEnvironment">PolicyEnvironment</a> <a name="policyenvironment" id="policyenvironment">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Override policies based on an environment variable.</td></tr>
<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>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyEnvironment is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Downgrade policies to logging only or ignored based on the presence
of an environment variable. If the given variable is present and equal
to the log-value, enforced policies will be logged instead. If the given
variable is present and equal to the ignore-value, all policies will
be ignored.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# downgrade if POLICY_CONTROL was present
PolicyEnvironment POLICY_CONTROL log ignore
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyFilter" id="PolicyFilter">PolicyFilter</a> <a name="policyfilter" id="policyfilter">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable or disable policies for the given URL space.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyFilter <var>on|off</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>on</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyFilter is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Master switch to enable or disable policies for a given URL space.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# enabled by default
<Location />
PolicyFilter on
</Location>
# suppress policy protection for server-status
<Location /server-status>
PolicyFilter off
</Location>
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyKeepalive" id="PolicyKeepalive">PolicyKeepalive</a> <a name="policykeepalive" id="policykeepalive">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the keepalive policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyKeepalive <var>ignore|log|enforce</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyKeepalive is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>When logged or enforced, a response that lacks both an explicit
<code>Content-Length</code> header and a <code>Transfer-Encoding</code>
of <code>chunked</code> will be rejected.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# missing Content-Length or Transfer-Encoding should be rejected
PolicyKeepalive enforce
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyKeepaliveURL" id="PolicyKeepaliveURL">PolicyKeepaliveURL</a> <a name="policykeepaliveurl" id="policykeepaliveurl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the keepalive policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyKeepaliveURL <var>url</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyKeepaliveURL is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Specify the URL of the documentation describing the keepalive
policy, to appear within error messages.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyLength" id="PolicyLength">PolicyLength</a> <a name="policylength" id="policylength">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the content length policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyLength <var>ignore|log|enforce</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyLength is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>When logged or enforced, a response that lacks an explicit
<code>Content-Length</code> header will be rejected.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# missing Content-Length header should be rejected
PolicyLength enforce
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyLengthURL" id="PolicyLengthURL">PolicyLengthURL</a> <a name="policylengthurl" id="policylengthurl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content length policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyLengthURL <var>url</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyLengthURL is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Specify the URL of the documentation describing the content length
policy, to appear within error messages.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyMaxage" id="PolicyMaxage">PolicyMaxage</a> <a name="policymaxage" id="policymaxage">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the caching minimum max-age policy.</td></tr>
<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>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyMaxage is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>When logged or enforced, a response that lacks an explicit freshness
lifetime defined with <code>max-age</code>, <code>s-maxage</code> or an
<code>Expires</code> header, or where the explicit freshness lifetime is
smaller than the given value, will be rejected.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# reject responses with a freshness lifetime shorter than a day
PolicyMaxage enforce 86400
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyMaxageURL" id="PolicyMaxageURL">PolicyMaxageURL</a> <a name="policymaxageurl" id="policymaxageurl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the caching minimum freshness lifetime policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyMaxageURL <var>url</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyMaxageURL is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Specify the URL of the documentation describing the caching minimum
freshness lifetime policy, to appear within error messages.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyNocache" id="PolicyNocache">PolicyNocache</a> <a name="policynocache" id="policynocache">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the caching no-cache policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyNocache <var>ignore|log|enforce</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyNocache is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>When logged or enforced, a response that defines itself uncacheable
using the <code>Cache-Control</code> or <code>Pragma</code> headers will
be rejected.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# Cache-Control: no-cache will be rejected
PolicyNocache enforce
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyNocacheURL" id="PolicyNocacheURL">PolicyNocacheURL</a> <a name="policynocacheurl" id="policynocacheurl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the caching no-cache policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyNocacheURL <var>url</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyNocacheURL is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Specify the URL of the documentation describing the caching no-cache
policy, to appear within error messages.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyType" id="PolicyType">PolicyType</a> <a name="policytype" id="policytype">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the content type policy.</td></tr>
<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>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyType is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>When logged or enforced, a response that lacks a <code>Content-Type</code>
header, where the <code>Content-Type</code> header is malformed, or where the
header does not match the given pattern or patterns will be rejected.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# enforce json or XML
PolicyType enforce application/json text/xml
</pre>
</div>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# malformed content type should be rejected
PolicyType enforce */*
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyTypeURL" id="PolicyTypeURL">PolicyTypeURL</a> <a name="policytypeurl" id="policytypeurl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content type policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyTypeURL <var>url</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyTypeURL is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Specify the URL of the documentation describing the content type
policy, to appear within error messages.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyValidation" id="PolicyValidation">PolicyValidation</a> <a name="policyvalidation" id="policyvalidation">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the validation policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyValidation <var>ignore|log|enforce</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyValidation is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>When logged or enforced, a response that lacks either a valid
<code>ETag</code> header or a <code>Last-Modified</code> header, or where
either header is syntactically incorrect, will be rejected.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# no ETag or Last-Modified will be rejected
PolicyValidation enforce
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyValidationURL" id="PolicyValidationURL">PolicyValidationURL</a> <a name="policyvalidationurl" id="policyvalidationurl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content type policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyValidationURL <var>url</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyValidationURL is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Specify the URL of the documentation describing the validation policy, to
appear within error messages.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyVary" id="PolicyVary">PolicyVary</a> <a name="policyvary" id="policyvary">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the Vary policy.</td></tr>
<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>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVary is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>When logged or enforced, a response that contains a <code>Vary</code>
header which in turn contains one of the headers listed, will be
rejected.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# reject reponses with "User-Agent" listed in the Vary header
PolicyVary enforce User-Agent
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyVaryURL" id="PolicyVaryURL">PolicyVaryURL</a> <a name="policyvaryurl" id="policyvaryurl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the content type policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyVaryURL <var>url</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVaryURL is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Specify the URL of the documentation describing the vary policy, to
appear within error messages.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyVersion" id="PolicyVersion">PolicyVersion</a> <a name="policyversion" id="policyversion">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the version policy.</td></tr>
<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>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ignore</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVersion is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>When logged or enforced, a request with a version lower than specified
will be rejected.</p>
<div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
# reject requests with an HTTP version older than HTTP/1.1
PolicyVersion enforce HTTP/1.1
</pre>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="PolicyVersionURL" id="PolicyVersionURL">PolicyVersionURL</a> <a name="policyversionurl" id="policyversionurl">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>URL describing the minimum request HTTP version policy.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PolicyVersionURL <var>url</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>none</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_policy</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>PolicyVersionURL is only available in Apache 2.5.0 and
later.</td></tr>
</table>
<p>Specify the URL of the documentation describing the minimum request
HTTP version policy, to appear within error messages.</p>
</div>
</div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="../en/mod/mod_policy.html" title="English"> en </a></p>
</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>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
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