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16 <p class="apache">Apache HTTP Server Version 2.1</p>
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22 <div id="preamble"><h1>Apache Module mod_log_forensic</h1>
24 <p><span>Available Languages: </span><a href="../en/mod/mod_log_forensic.html" title="English"> en </a></p>
26 <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>
27 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
28 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>log_forensic_module</td></tr>
29 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_log_forensic.c</td></tr>
30 <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
31 version 2.1</td></tr></table>
34 <p>This module provides for forensic logging of client
35 requests. Logging is done before and after processing a request, so the
36 forensic log contains two log lines for each request.
37 The forensic logger is very strict, which means:</p>
40 <li>The format is fixed. You cannot modify the logging format at
42 <li>If it cannot write its data, the child process
43 exits immediately and may dump core (depending on your
44 <code class="directive"><a href="../mod/mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></code>
48 <p>The <code>check_forensic</code> script, which can be found in the
49 distribution's support directory, may be helpful in evaluating the
50 forensic log output.</p>
52 <div id="quickview"><h3 class="directives">Directives</h3>
54 <li><img alt="" src="../images/down.gif" /> <a href="#forensiclog">ForensicLog</a></li>
58 <li><img alt="" src="../images/down.gif" /> <a href="#formats">Forensic Log Format</a></li>
59 <li><img alt="" src="../images/down.gif" /> <a href="#security">Security Considerations</a></li>
60 </ul><h3>See also</h3>
62 <li><a href="../logs.html">Apache Log Files</a></li>
63 <li><code class="module"><a href="../mod/mod_log_config.html">mod_log_config</a></code></li>
65 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
67 <h2><a name="formats" id="formats">Forensic Log Format</a></h2>
68 <p>Each request is logged two times. The first time is <em>before</em> it's
69 processed further (that is, after receiving the headers). The second log
70 entry is written <em>after</em> the request processing at the same time
71 where normal logging occurs.</p>
73 <p>In order to identify each request, a unique request ID is assigned.
74 This forensic ID can be cross logged in the normal transfer log using the
75 <code>%{forensic-id}n</code> format string. If you're using
76 <code class="module"><a href="../mod/mod_unique_id.html">mod_unique_id</a></code>, its generated ID will be used.</p>
78 <p>The first line logs the forensic ID, the request line and all received
79 headers, separated by pipe characters (<code>|</code>). A sample line
80 looks like the following (all on one line):</p>
82 <div class="example"><p><code>
83 +yQtJf8CoAB4AAFNXBIEAAAAA|GET /manual/de/images/down.gif
84 HTTP/1.1|Host:localhost%3a8080|User-Agent:Mozilla/5.0 (X11;
85 U; Linux i686; en-US; rv%3a1.6) Gecko/20040216
86 Firefox/0.8|Accept:image/png, <var>etc...</var>
89 <p>The plus character at the beginning indicates that this is the first log
90 line of this request. The second line just contains a minus character and
93 <div class="example"><p><code>
94 -yQtJf8CoAB4AAFNXBIEAAAAA
97 <p>The <code>check_forensic</code> script takes as its argument the name
98 of the logfile. It looks for those <code>+</code>/<code>-</code> ID pairs
99 and complains if a request was not completed.</p>
100 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
101 <div class="section">
102 <h2><a name="security" id="security">Security Considerations</a></h2>
103 <p>See the <a href="../misc/security_tips.html#serverroot">security tips</a>
104 document for details on why your security could be compromised
105 if the directory where logfiles are stored is writable by
106 anyone other than the user that starts the server.</p>
108 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
109 <div class="directive-section"><h2><a name="ForensicLog" id="ForensicLog">ForensicLog</a> <a name="forensiclog" id="forensiclog">Directive</a></h2>
110 <table class="directive">
111 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets filename of the forensic log</td></tr>
112 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ForensicLog <var>filename</var>|<var>pipe</var></code></td></tr>
113 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
114 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
115 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_forensic</td></tr>
117 <p>The <code class="directive">ForensicLog</code> directive is used to
118 log requests to the server for forensic analysis. Each log entry
119 is assigned a unique ID which can be associated with the request
120 using the normal <code class="directive"><a href="../mod/mod_log_config.html#customlog">CustomLog</a></code>
121 directive. <code class="module"><a href="../mod/mod_log_forensic.html">mod_log_forensic</a></code> creates a token called
122 <code>forensic-id</code>, which can be added to the transfer log
123 using the <code>%{forensic-id}n</code> format string.</p>
125 <p>The argument, which specifies the location to which
126 the logs will be written, can take one of the following two
130 <dt><var>filename</var></dt>
131 <dd>A filename, relative to the <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</dd>
133 <dt><var>pipe</var></dt>
134 <dd>The pipe character "<code>|</code>", followed by the path
135 to a program to receive the log information on its standard
136 input. The program name can be specified relative to the <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code> directive.
138 <div class="warning"><h3>Security:</h3>
139 <p>If a program is used, then it will be run as the user who
140 started httpd. This will be root if the server was started by root;
141 be sure that the program is secure or switches to a less privileged
145 <div class="note"><h3>Note</h3>
146 <p>When entering a file path on non-Unix platforms, care should be taken
147 to make sure that only forward slashed are used even though the platform
148 may allow the use of back slashes. In general it is a good idea to always
149 use forward slashes throughout the configuration files.</p>
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156 <p><span>Available Languages: </span><a href="../en/mod/mod_log_forensic.html" title="English"> en </a></p>
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158 <p class="apache">Copyright 1999-2004 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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