Apache HTTP Server Version 2.2
Apache Module mod_log_forensic
| Description: | Forensic Logging of the requests made to the server |
|---|---|
| Status: | Extension |
| Module Identifier: | log_forensic_module |
| Source File: | mod_log_forensic.c |
| Compatibility: | mod_unique_id is no longer required since
version 2.1 |
Summary
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:
- The format is fixed. You cannot modify the logging format at runtime.
- If it cannot write its data, the child process
exits immediately and may dump core (depending on your
CoreDumpDirectoryconfiguration).
The check_forensic script, which can be found in the
distribution's support directory, may be helpful in evaluating the
forensic log output.
See also
Forensic Log Format
Each request is logged two times. The first time is before it's processed further (that is, after receiving the headers). The second log entry is written after the request processing at the same time where normal logging occurs.
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
%{forensic-id}n format string. If you're using
mod_unique_id, its generated ID will be used.
The first line logs the forensic ID, the request line and all received
headers, separated by pipe characters (|). A sample line
looks like the following (all on one line):
+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, etc...
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:
-yQtJf8CoAB4AAFNXBIEAAAAA
The check_forensic script takes as its argument the name
of the logfile. It looks for those +/- ID pairs
and complains if a request was not completed.
Security Considerations
See the security tips 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.
The log files may contain sensitive data such as the contents of
Authorization: headers (which can contain passwords), so
they should not be readable by anyone except the user that starts the
server.
ForensicLog Directive
| Description: | Sets filename of the forensic log |
|---|---|
| Syntax: | ForensicLog filename|pipe |
| Context: | server config, virtual host |
| Status: | Extension |
| Module: | mod_log_forensic |
The ForensicLog 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 CustomLog
directive. mod_log_forensic creates a token called
forensic-id, which can be added to the transfer log
using the %{forensic-id}n format string.
The argument, which specifies the location to which the logs will be written, can take one of the following two types of values:
- filename
- A filename, relative to the
ServerRoot. - pipe
- The pipe character "
|", followed by the path to a program to receive the log information on its standard input. The program name can be specified relative to theServerRootdirective.Security:
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.Note
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.