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<div id="preamble"><h1>Apache Module mod_log_forensic</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="/en/mod/mod_log_forensic.html" title="English"> en </a> |
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Forensic Logging of the requests made to the server</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>log_forensic_module</td></tr>
<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td><code class="module"><a href="/mod/mod_unique_id.html">mod_unique_id</a></code> is no longer required since
version 2.1</td></tr></table>
<h3>Summary</h3>
<p>This module provides for forensic logging of client
requests. Logging is done before and after processing a request, so the
forensic log contains two log lines for each request.
The forensic logger is very strict, which means:</p>
<ul>
<li>The format is fixed. You cannot modify the logging format at
runtime.</li>
<li>If it cannot write its data, the child process
exits immediately and may dump core (depending on your
<code class="directive"><a href="/mod/mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></code>
configuration).</li>
</ul>
<p>The <code>check_forensic</code> script, which can be found in the
distribution's support directory, may be helpful in evaluating the
forensic log output.</p>
</div>
<div id="quickview"><h3 class="directives">Directives</h3>
<ul id="toc">
</ul>
<h3>Topics</h3>
<ul id="topics">
</ul><h3>See also</h3>
<ul class="seealso">
</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
<div class="section">
<h2><a name="formats" id="formats">Forensic Log Format</a></h2>
<p>Each request is logged two times. The first time is <em>before</em> it's
processed further (that is, after receiving the headers). The second log
entry is written <em>after</em> the request processing at the same time
where normal logging occurs.</p>
<p>In order to identify each request, a unique request ID is assigned.
This forensic ID can be cross logged in the normal transfer log using the
<code>%{forensic-id}n</code> format string. If you're using
<code class="module"><a href="/mod/mod_unique_id.html">mod_unique_id</a></code>, its generated ID will be used.</p>
<p>The first line logs the forensic ID, the request line and all received
headers, separated by pipe characters (<code>|</code>). A sample line
looks like the following (all on one line):</p>
<div class="example"><p><code>
</code></p></div>
<p>The plus character at the beginning indicates that this is the first log
line of this request. The second line just contains a minus character and
the ID again:</p>
<div class="example"><p><code>
-yQtJf8CoAB4AAFNXBIEAAAAA
</code></p></div>
<p>The <code>check_forensic</code> script takes as its argument the name
of the logfile. It looks for those <code>+</code>/<code>-</code> ID pairs
and complains if a request was not completed.</p>
<div class="section">
<h2><a name="security" id="security">Security Considerations</a></h2>
document for details on why your security could be compromised
if the directory where logfiles are stored is writable by
anyone other than the user that starts the server.</p>
<p>The log files may contain sensitive data such as the contents of
<code>Authorization:</code> headers (which can contain passwords), so
they should not be readable by anyone except the user that starts the
server.</p>
</div>
<div class="directive-section"><h2><a name="ForensicLog" id="ForensicLog">ForensicLog</a> <a name="forensiclog" id="forensiclog">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets filename of the forensic log</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ForensicLog <var>filename</var>|<var>pipe</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>The <code class="directive">ForensicLog</code> directive is used to
log requests to the server for forensic analysis. Each log entry
is assigned a unique ID which can be associated with the request
using the normal <code class="directive"><a href="/mod/mod_log_config.html#customlog">CustomLog</a></code>
directive. <code class="module"><a href="/mod/mod_log_forensic.html">mod_log_forensic</a></code> creates a token called
<code>forensic-id</code>, which can be added to the transfer log
using the <code>%{forensic-id}n</code> format string.</p>
<p>The argument, which specifies the location to which
the logs will be written, can take one of the following two
types of values:</p>
<dl>
<dt><var>filename</var></dt>
<dd>A filename, relative to the <code class="directive"><a href="/mod/core.html#serverroot">ServerRoot</a></code>.</dd>
<dt><var>pipe</var></dt>
<dd>The pipe character "<code>|</code>", followed by the path
to a program to receive the log information on its standard
input. The program name can be specified relative to the <code class="directive"><a href="/mod/core.html#serverroot">ServerRoot</a></code> directive.
<div class="warning"><h3>Security:</h3>
<p>If a program is used, then it will be run as the user who
started <code class="program"><a href="/programs/httpd.html">httpd</a></code>. This will be root if the server was
started by root; be sure that the program is secure or switches to a
less privileged user.</p>
</div>
<div class="note"><h3>Note</h3>
<p>When entering a file path on non-Unix platforms, care should be taken
to make sure that only forward slashes are used even though the platform
may allow the use of back slashes. In general it is a good idea to always
use forward slashes throughout the configuration files.</p>
</div></dd>
</dl>
</div>
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