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   8 <title>mod_log_forensic - Apache HTTP Server</title>
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  21 <div id="page-content">
  22 <div id="preamble"><h1>Apache Module mod_log_forensic</h1>
  23 <div class="toplang">
  24 <p><span>Available Languages: </span><a href="../en/mod/mod_log_forensic.html" title="English">&nbsp;en&nbsp;</a> |
  25 <a href="../ja/mod/mod_log_forensic.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
  26 <a href="../tr/mod/mod_log_forensic.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
  27 </div>
  28 <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>
  29 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  30 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>log_forensic_module</td></tr>
  31 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_log_forensic.c</td></tr>
  32 <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
  33 version 2.1</td></tr></table>
  34 <h3>Summary</h3>
  35
  36     <p>This module provides for forensic logging of client
  37     requests. Logging is done before and after processing a request, so the
  38     forensic log contains two log lines for each request.
  39     The forensic logger is very strict, which means:</p>
  40
  41     <ul>
  42     <li>The format is fixed. You cannot modify the logging format at
  43     runtime.</li>
  44     <li>If it cannot write its data, the child process
  45     exits immediately and may dump core (depending on your
  46     <code class="directive"><a href="../mod/mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></code>
  47     configuration).</li>
  48     </ul>
  49
  50     <p>The <code>check_forensic</code> script, which can be found in the
  51     distribution's support directory, may be helpful in evaluating the
  52     forensic log output.</p>
  53 </div>
  54 <div id="quickview"><h3 class="directives">Directives</h3>
  55 <ul id="toc">
  56 <li><img alt="" src="../images/down.gif" /> <a href="#forensiclog">ForensicLog</a></li>
  57 </ul>
  58 <h3>Topics</h3>
  59 <ul id="topics">
  60 <li><img alt="" src="../images/down.gif" /> <a href="#formats">Forensic Log Format</a></li>
  61 <li><img alt="" src="../images/down.gif" /> <a href="#security">Security Considerations</a></li>
  62 </ul><h3>See also</h3>
  63 <ul class="seealso">
  64 <li><a href="../logs.html">Apache Log Files</a></li>
  65 <li><code class="module"><a href="../mod/mod_log_config.html">mod_log_config</a></code></li>
  66 </ul></div>
  67 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  68 <div class="section">
  69 <h2><a name="formats" id="formats">Forensic Log Format</a></h2>
  70     <p>Each request is logged two times. The first time is <em>before</em> it's
  71     processed further (that is, after receiving the headers). The second log
  72     entry is written <em>after</em> the request processing at the same time
  73     where normal logging occurs.</p>
  74
  75     <p>In order to identify each request, a unique request ID is assigned.
  76     This forensic ID can be cross logged in the normal transfer log using the
  77     <code>%{forensic-id}n</code> format string. If you're using
  78     <code class="module"><a href="../mod/mod_unique_id.html">mod_unique_id</a></code>, its generated ID will be used.</p>
  79
  80     <p>The first line logs the forensic ID, the request line and all received
  81     headers, separated by pipe characters (<code>|</code>). A sample line
  82     looks like the following (all on one line):</p>
  83
  84     <div class="example"><p><code>
  85         +yQtJf8CoAB4AAFNXBIEAAAAA|GET /manual/de/images/down.gif
  86         HTTP/1.1|Host:localhost%3a8080|User-Agent:Mozilla/5.0 (X11;
  87         U; Linux i686; en-US; rv%3a1.6) Gecko/20040216
  88         Firefox/0.8|Accept:image/png, <var>etc...</var>
  89     </code></p></div>
  90
  91     <p>The plus character at the beginning indicates that this is the first log
  92     line of this request. The second line just contains a minus character and
  93     the ID again:</p>
  94
  95     <div class="example"><p><code>
  96       -yQtJf8CoAB4AAFNXBIEAAAAA
  97     </code></p></div>
  98
  99     <p>The <code>check_forensic</code> script takes as its argument the name
 100     of the logfile. It looks for those <code>+</code>/<code>-</code> ID pairs
 101     and complains if a request was not completed.</p>
 102 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 103 <div class="section">
 104 <h2><a name="security" id="security">Security Considerations</a></h2>
 105     <p>See the <a href="../misc/security_tips.html#serverroot">security tips</a>
 106     document for details on why your security could be compromised
 107     if the directory where logfiles are stored is writable by
 108     anyone other than the user that starts the server.</p>
 109 </div>
 110 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 111 <div class="directive-section"><h2><a name="ForensicLog" id="ForensicLog">ForensicLog</a> <a name="forensiclog" id="forensiclog">Directive</a></h2>
 112 <table class="directive">
 113 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets filename of the forensic log</td></tr>
 114 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ForensicLog <var>filename</var>|<var>pipe</var></code></td></tr>
 115 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
 116 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 117 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_forensic</td></tr>
 118 </table>
 119     <p>The <code class="directive">ForensicLog</code> directive is used to
 120     log requests to the server for forensic analysis. Each log entry
 121     is assigned a unique ID which can be associated with the request
 122     using the normal <code class="directive"><a href="../mod/mod_log_config.html#customlog">CustomLog</a></code>
 123     directive. <code class="module"><a href="../mod/mod_log_forensic.html">mod_log_forensic</a></code> creates a token called
 124     <code>forensic-id</code>, which can be added to the transfer log
 125     using the <code>%{forensic-id}n</code> format string.</p>
 126
 127     <p>The argument, which specifies the location to which
 128     the logs will be written, can take one of the following two
 129     types of values:</p>
 130
 131     <dl>
 132       <dt><var>filename</var></dt>
 133       <dd>A filename, relative to the <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</dd>
 134
 135       <dt><var>pipe</var></dt>
 136       <dd>The pipe character "<code>|</code>", followed by the path
 137       to a program to receive the log information on its standard
 138       input. The program name can be specified relative to the <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code> directive.
 139
 140       <div class="warning"><h3>Security:</h3>
 141       <p>If a program is used, then it will be run as the user who
 142       started <code class="program"><a href="../programs/httpd.html">httpd</a></code>. This will be root if the server was
 143       started by root; be sure that the program is secure or switches to a
 144       less privileged user.</p>
 145       </div>
 146
 147       <div class="note"><h3>Note</h3>
 148         <p>When entering a file path on non-Unix platforms, care should be taken
 149         to make sure that only forward slashes are used even though the platform
 150         may allow the use of back slashes. In general it is a good idea to always
 151         use forward slashes throughout the configuration files.</p>
 152       </div></dd>
 153     </dl>
 154
 155 </div>
 156 </div>
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 158 <p><span>Available Languages: </span><a href="../en/mod/mod_log_forensic.html" title="English">&nbsp;en&nbsp;</a> |
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 162 <p class="apache">Copyright 2009 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>
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