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<modulesynopsis metafile="mod_log_forensic.xml.meta">

<name>mod_log_forensic</name>

<description>Forensic Logging of the requests made to the server</description>

<status>Extension</status>

<sourcefile>mod_log_forensic.c</sourcefile>

<identifier>log_forensic_module</identifier>

<compatibility><module>mod_unique_id</module> is no longer required since

version 2.1</compatibility>

<summary>

<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

<directive module="mpm_common">CoreDumpDirectory</directive>

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>

</summary>

<seealso><a href="/logs.html">Apache Log Files</a></seealso>

<seealso><module>mod_log_config</module></seealso>

<section id="formats"><title>Forensic Log Format</title>

<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

<module>mod_unique_id</module>, 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>

<example>

+yQtJf8CoAB4AAFNXBIEAAAAA|GET /manual/de/images/down.gif

HTTP/1.1|Host:localhost%3a8080|User-Agent:Mozilla/5.0 (X11;

U; Linux i686; en-US; rv%3a1.6) Gecko/20040216

Firefox/0.8|Accept:image/png, <var>etc...</var>

</example>

<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>

<example>

-yQtJf8CoAB4AAFNXBIEAAAAA

</example>

<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>

</section>

<section id="security"><title>Security Considerations</title>

<p>See the <a

href="/misc/security_tips.html#serverroot">security tips</a>

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>

</section>

<directivesynopsis>

<name>ForensicLog</name>

<description>Sets filename of the forensic log</description>

<syntax>ForensicLog <var>filename</var>|<var>pipe</var></syntax>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>The <directive>ForensicLog</directive> 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 <directive module="mod_log_config">CustomLog</directive>

directive. <module>mod_log_forensic</module> 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 <directive module="core"

>ServerRoot</directive>.</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 <directive

module="core">ServerRoot</directive> directive.

<note type="warning"><title>Security:</title>

<p>If a program is used, then it will be run as the user who

started <program>httpd</program>. 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>

</note>

<note><title>Note</title>

<p>When entering a file path on non-Unix platforms, care should be taken

to make sure that only forward slashed 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>

</note></dd>

</dl>

</usage>

</directivesynopsis>

</modulesynopsis>