<?xml version="1.0"?>
<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
<!-- $Revision: 1.3.2.2 $ -->

<!--
 Copyright 2004 The Apache Software Foundation

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
-->

<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>Available in version 2.0.50 and later</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>

    <note type="warning">
      This module was backported from version 2.1 which uses a more powerful
      APR version in order to generate the forensic IDs. If you want to run
      <module>mod_log_forensic</module> in version 2.0, you need to include
      <module>mod_unique_id</module> as well.
    </note>
</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 <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 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> takes the unique ID from
    <module>mod_unique_id</module>, so you need to load this module as well.
    (This requirement will not be necessary in version 2.1 and later, because
    of a more powerful APR version.) The ID token is attached to the request
    under the name <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 httpd. 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>
