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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>Shorewall Logging</title>
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<meta http-equiv="content-type"
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content="text/html; charset=ISO-8859-1">
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<meta name="author" content="Tom Eastep">
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</head>
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<body>
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<h1 style="text-align: center;">Logging</h1>
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<h2>How to Log Traffic through a Shorewall Firewall</h2>
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The disposition of packets entering a Shorewall firewall is
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determined by one of a number of Shorewall facilities. Only some of
|
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these facilities permit logging.<br>
|
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<ol>
|
||||
<li>The packet is part of an established connection. The packet is
|
||||
accepted and cannot be logged.</li>
|
||||
<li>The packet represents a connection request that is related to an
|
||||
established connection (such as a <a href="FTP.html">data connection
|
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associated with an FTP control connection</a>). These packets
|
||||
also cannot be logged.</li>
|
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<li>The packet is rejected because of an option in <a
|
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href="Documentation.htm#Conf">/etc/shorewall/shorewall.conf</a> or <a
|
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href="Documentation.htm#Interfaces">/etc/shorewall/interfaces</a>.
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These packets can be logged by setting the appropriate logging-related
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option in <a href="Documentation.htm#Conf">/etc/shorewall/shorewall.conf.</a></li>
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<li>The packet matches a rule in <a href="Documentation.htm#Rules">/etc/shorewall/rules</a>.
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By including a syslog level (see below) in the ACTION column of a rule
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(e.g., "ACCEPT<span
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style="font-weight: bold; text-decoration: underline;">:info</span>
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net fw tcp 22"), the connection attempt will be logged at that level.</li>
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<li>The packet doesn't match a rule so is handled by a policy defined
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in <a href="Documentation.htm#Policy">/etc/shorewall/policy</a>. These
|
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may be logged by specifying a syslog level in the LOG LEVEL column of
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the policy entry (e.g., "loc net ACCEPT <span
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style="font-weight: bold; text-decoration: underline;">info</span>"<br>
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</li>
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</ol>
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<h2>Where the Traffic is logged and how to Change the Destination<br>
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</h2>
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By default, Shorewall directs NetFilter to log using syslog (8). Syslog
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classifies log messages by a <i>facility</i> and a <i>priority</i>
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(using the notation <i>facility.priority</i>). <br>
|
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<br>
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The facilities defined by syslog are <i>auth, authpriv, cron, daemon,
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kern, lpr, mail, mark, news, syslog, user, uucp</i> and <i>local0</i>
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through <i>local7</i>.<br>
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<br>
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Throughout the Shorewall documentation, I will use the term <i>level</i>
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rather than <i>priority</i> since <i>level</i> is the term used by
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NetFilter. The syslog documentation uses the term <i>priority</i>.<br>
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<h3>Syslog Levels<br>
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</h3>
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Syslog levels are a method of describing to syslog (8) the importance
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of a message and a number of Shorewall parameters have a syslog level
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as their value.<br>
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<br>
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Valid levels are:<br>
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<br>
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7 <span style="font-weight: bold;">debug</span>
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(Debug-level messages)<br>
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6 <span style="font-weight: bold;">info</span>
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(Informational)<br>
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5 <span style="font-weight: bold;">notice</span>
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(Normal but significant Condition)<br>
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4 <span style="font-weight: bold;">
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warning</span> (Warning Conditions)<br>
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3 <span style="font-weight: bold;">err</span>
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(Error Conditions)<br>
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2 <span style="font-weight: bold;">crit</span>
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(Critical Conditions)<br>
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1 <span style="font-weight: bold;">alert</span>
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(Must be handled immediately)<br>
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0 <span style="font-weight: bold;">emerg</span>
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(System is unusable)<br>
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<br>
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For most Shorewall logging, a level of 6 (info) is appropriate.
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Shorewall log messages are generated by NetFilter and are logged using
|
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the <i>kern</i> facility and the level that you specify. If you are
|
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unsure of the level to choose, 6 (info) is a safe bet. You may specify
|
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levels by name or by number.<br>
|
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<br>
|
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Syslogd writes log messages to files (typically in /var/log/*)
|
||||
based on their facility and level. The mapping of these facility/level
|
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pairs to log files is done in /etc/syslog.conf (5). If you make changes
|
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to this file, you must restart syslogd before the changes can take
|
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effect.<br>
|
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<h3>Configuring a Separate Log for Shorewall Messages</h3>
|
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There are a couple of limitations to syslogd-based logging:<br>
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<ol>
|
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<li>If you give, for example, kern.info it's own log destination then
|
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that destination will also receive all kernel messages of levels 5
|
||||
(notice) through 0 (emerg).</li>
|
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<li>All kernel.info messages will go to that destination and not just
|
||||
those from NetFilter.<br>
|
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</li>
|
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</ol>
|
||||
Beginning with Shorewall version 1.3.12, if your kernel has ULOG target
|
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support (and most vendor-supplied kernels do), you may also specify a
|
||||
log level of ULOG (must be all caps). When ULOG is used, Shorewall will
|
||||
direct netfilter to log the related messages via the ULOG target which
|
||||
will send them to a process called 'ulogd'. The ulogd program is
|
||||
available from http://www.gnumonks.org/projects/ulogd and can be
|
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configured to log all Shorewall message to their own log file.<br>
|
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<br>
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<b>Note: </b>The ULOG logging mechanism is <u>completely separate</u>
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from syslog. Once you switch to ULOG, the settings in /etc/syslog.conf
|
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have
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absolutely no effect on your Shorewall logging (except for Shorewall
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status
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messages which still go to syslog).<br>
|
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<br>
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You will need to have the kernel source available to compile ulogd.<br>
|
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<br>
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Download the ulod tar file and:<br>
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<ol>
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<li>Be sure that /usr/src/linux is linked to your kernel source tree<br>
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</li>
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<li>cd /usr/local/src (or wherever you do your builds)</li>
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<li>tar -zxf <i>source-tarball-that-you-downloaded</i></li>
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<li>cd ulogd-<i>version</i><br>
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</li>
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<li>./configure</li>
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<li>make</li>
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<li>make install<br>
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</li>
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</ol>
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If you are like me and don't have a development environment on your
|
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firewall, you can do the first six steps on another system then either
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||||
NFS
|
||||
mount your /usr/local/src directory or tar up the /usr/local/src/ulogd-<i>version</i>
|
||||
directory and move it to your firewall system.<br>
|
||||
<br>
|
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Now on the firewall system, edit /usr/local/etc/ulogd.conf and set:<br>
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<ol>
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<li>syslogfile <i><file that you wish to log to></i></li>
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<li>syslogsync 1</li>
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</ol>
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Also on the firewall system:<br>
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<blockquote>touch <<i>file that you wish to log to</i>><br>
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</blockquote>
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I also copied the file /usr/local/src/ulogd-<i>version</i>/ulogd.init
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to /etc/init.d/ulogd. I had to edit the line that read "daemon
|
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/usr/local/sbin/ulogd" to read daemon /usr/local/sbin/ulogd -d". On a
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RedHat system, a simple
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"chkconfig --level 3 ulogd on" starts ulogd during boot up. Your init
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system
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may need something else done to activate the script.<br>
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<br>
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You will need to change all instances of log levels (usually 'info') in
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your configuration files to 'ULOG' - this includes entries in the
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policy, rules and shorewall.conf files. Here's what I have:<br>
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<pre> [root@gateway shorewall]# grep ULOG *<br> policy:loc fw REJECT ULOG<br> policy:net all DROP ULOG 10/sec:40<br> policy:all all REJECT ULOG<br> rules:REJECT:ULOG loc net tcp 6667<br> shorewall.conf:TCP_FLAGS_LOG_LEVEL=ULOG<br> shorewall.conf:RFC1918_LOG_LEVEL=ULOG<br> [root@gateway shorewall]#<br></pre>
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Finally edit /etc/shorewall/shorewall.conf and set LOGFILE=<i><file
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that you wish to log to></i>. This tells the /sbin/shorewall program
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where to look for the log when processing its "show log", "logwatch"
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and
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"monitor" commands.<br>
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<h2>Syslog-ng</h2>
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<a
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href="http://marc.theaimsgroup.com/?l=gentoo-security&m=106040714910563&w=2">Here</a>
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is a post describing configuring syslog-ng to work with Shorewall.<br>
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<p><font size="2"> Updated 10/30/2003 - <a href="support.htm">Tom
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Eastep</a>
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</font></p>
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<p><a href="copyright.htm"><font size="2">Copyright</font> © <font
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size="2">2001, 2002, 2003 Thomas M. Eastep</font></a><br>
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</p>
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<br>
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<br>
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</body>
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</html>
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284
Shorewall-docs/shorewall_logging.xml
Normal file
284
Shorewall-docs/shorewall_logging.xml
Normal file
@ -0,0 +1,284 @@
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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||||
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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||||
<article id="IPIP">
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<articleinfo>
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<title>Shorewall Logging</title>
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<authorgroup>
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||||
<author>
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<firstname>Tom</firstname>
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<surname>Eastep</surname>
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</author>
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</authorgroup>
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||||
|
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<pubdate>2003-12-18</pubdate>
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<copyright>
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||||
<year>2001 - 2003</year>
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||||
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||||
<holder>Thomas M. Eastep</holder>
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||||
</copyright>
|
||||
|
||||
<legalnotice>
|
||||
<para>Permission is granted to copy, distribute and/or modify this
|
||||
document under the terms of the GNU Free Documentation License, Version
|
||||
1.2 or any later version published by the Free Software Foundation; with
|
||||
no Invariant Sections, with no Front-Cover, and with no Back-Cover
|
||||
Texts. A copy of the license is included in the section entitled "<ulink
|
||||
url="GnuCopyright.htm">GNU Free Documentation License</ulink>".</para>
|
||||
</legalnotice>
|
||||
</articleinfo>
|
||||
|
||||
<section>
|
||||
<title>How to Log Traffic Through a Shorewall Firewall</title>
|
||||
|
||||
<para>The disposition of packets entering a Shorewall firewall is
|
||||
determined by one of a number of Shorewall facilities. Only some of these
|
||||
facilities permit logging.</para>
|
||||
|
||||
<orderedlist>
|
||||
<listitem>
|
||||
<para>The packet is part of an established commection. The packet is
|
||||
accepted and connot be logged.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>The packet represents a connection request that is related to an
|
||||
established connection (such as a <ulink url="FTP.html">data
|
||||
connection associated with an FTP control connection</ulink>). These
|
||||
packets also cannot be logged.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>The packet is rejected because of an option in <ulink
|
||||
url="Documentation.htm#Conf">/etc/shorewall/shorewall.conf</ulink> or
|
||||
<ulink url="Documentation.htm#Interfaces">/etc/shorewall/interfaces</ulink>.
|
||||
These packets can be logged by setting the appropriate logging-related
|
||||
option in <ulink url="Documentation.htm#Conf">/etc/shorewall/shorewall.conf</ulink>.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>The packet matches a rule in <ulink
|
||||
url="Documentation.htm#Rules">/etc/shorewall/rules</ulink>. By
|
||||
including a syslog level (see below) in the ACTION column of a rule
|
||||
(e.g., "ACCEPT<emphasis role="bold">:info</emphasis> net fw tcp
|
||||
22"), the connection attempt will be logged at that level.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>The packet doesn't match a rule so it is handled by a policy
|
||||
defined in <ulink url="Documentation.htm#Policy">/etc/shorewall/policy</ulink>.
|
||||
These may be logged by specifying a syslog level in the LOG LEVEL
|
||||
column of the policy's entry (e.g., "loc net ACCEPT <emphasis
|
||||
role="bold">info</emphasis>").</para>
|
||||
</listitem>
|
||||
</orderedlist>
|
||||
</section>
|
||||
|
||||
<section>
|
||||
<title>Where the Traffic is Logged and How to Change the Destination</title>
|
||||
|
||||
<para>By default, Shorewall directs NetFilter to log using syslog (8).
|
||||
Syslog classifies log messages by a <emphasis>facility</emphasis> and a
|
||||
<emphasis>priority</emphasis> (using the notation <emphasis>facility.priority</emphasis>).</para>
|
||||
|
||||
<para>The facilities defined by syslog are <emphasis>auth, authpriv, cron,
|
||||
daemon, kern, lpr, mail, mark, news, syslog, user, uucp</emphasis> and
|
||||
<emphasis>local0</emphasis> through <emphasis>local7.</emphasis></para>
|
||||
|
||||
<para>Throughout the Shorewall documentation, I will use the term
|
||||
<emphasis>level</emphasis> rather than <emphasis>priority </emphasis>since
|
||||
<emphasis>level</emphasis> is the term used by NetFilter. The syslog
|
||||
documentation uses the term <emphasis>priority</emphasis>. </para>
|
||||
|
||||
<section>
|
||||
<title>Syslog Levels</title>
|
||||
|
||||
<para>Syslog levels are a method of describing to syslog (8) the
|
||||
importance of a message. A number of Shorewall parameters have a syslog
|
||||
level as their value.</para>
|
||||
|
||||
<para>Valid levels are:</para>
|
||||
|
||||
<simplelist>
|
||||
<member>7 - <emphasis role="bold">debug</emphasis> (Debug-level
|
||||
messages)</member>
|
||||
|
||||
<member>6 - <emphasis role="bold">info</emphasis> (Informational)</member>
|
||||
|
||||
<member>5 - <emphasis role="bold">notice</emphasis> (Normal but
|
||||
significant Condition)</member>
|
||||
|
||||
<member>4 - <emphasis role="bold">warning</emphasis> (Warning
|
||||
Condition)</member>
|
||||
|
||||
<member>3 - <emphasis role="bold">err</emphasis> (Error Condition)</member>
|
||||
|
||||
<member>2 - <emphasis role="bold">crit</emphasis> (Critical
|
||||
Conditions)</member>
|
||||
|
||||
<member>1 - <emphasis role="bold">alert</emphasis> (must be handled
|
||||
immediately)</member>
|
||||
|
||||
<member>0 - <emphasis role="bold">emerg</emphasis> (System is
|
||||
unusable)</member>
|
||||
</simplelist>
|
||||
|
||||
<para>For most Shorewall logging, a level of 6 (info) is appropriate.
|
||||
Shorewall log messages are generated by NetFilter and are logged using
|
||||
the <emphasis>kern</emphasis> facility and the level that you specify.
|
||||
If you are unsure of the level to choose, 6 (info) is a safe bet. You
|
||||
may specify levels by name or by number.</para>
|
||||
|
||||
<para>Syslogd writes log messages to files (typically in /var/log/*)
|
||||
based on their facility and level. The mapping of these facility/level
|
||||
pairs to log files is done in /etc/syslog.conf (5). If you make changes
|
||||
to this file, you must restart syslogd before the changes can take
|
||||
effect.</para>
|
||||
</section>
|
||||
|
||||
<section>
|
||||
<title>Configuring a Separate Log for Shorewall Messages</title>
|
||||
|
||||
<para>There are a couple of limitations to syslogd-based logging:</para>
|
||||
|
||||
<orderedlist>
|
||||
<listitem>
|
||||
<para>If you give, for example, kern.info it's own log
|
||||
destination then that destination will also receive all kernel
|
||||
messages of levels 5 (notice) through 0 (emerg).</para>
|
||||
|
||||
<destructorsynopsis>
|
||||
<void />
|
||||
</destructorsynopsis>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>All kernel.info messages will go to that destination and not
|
||||
just those from NetFilter.</para>
|
||||
</listitem>
|
||||
</orderedlist>
|
||||
|
||||
<para>Beginning with Shorewall version 1.3.12, if your kernel has ULOG
|
||||
target support (and most vendor-supplied kernels do), you may also
|
||||
specify a log level of ULOG (must be all caps). When ULOG is used,
|
||||
Shorewall will direct netfilter to log the related messages via the ULOG
|
||||
target which will send them to a process called 'ulogd'. The
|
||||
ulogd program is available from <ulink
|
||||
url="http://www.gnumonks.org/projects/ulogd">http://www.gnumonks.org/projects/ulogd</ulink>
|
||||
and can be configured to log all Shorewall message to their own log
|
||||
file.</para>
|
||||
|
||||
<note>
|
||||
<para>The ULOG logging mechanism is <emphasis role="underline">completely
|
||||
separate</emphasis> from syslog. Once you switch to ULOG, the settings
|
||||
in /etc/syslog.conf have absolutely no effect on your Shorewall
|
||||
logging (except for Shorewall status messages which still go to
|
||||
syslog).</para>
|
||||
</note>
|
||||
|
||||
<para>You will need to have the kernel source available to compile
|
||||
ulogd.</para>
|
||||
|
||||
<para>Download the ulog tar file and:</para>
|
||||
|
||||
<orderedlist>
|
||||
<listitem>
|
||||
<para>Be sure that /usr/src/linux is linked to your kernel source
|
||||
tree</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>cd /usr/local/src (or whereever you do your builds)</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>tar -zxf <emphasis>source-tarball-that-you-downloaded</emphasis></para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>cd ulod-<emphasis>version</emphasis></para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>./configure</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>make</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>make install</para>
|
||||
</listitem>
|
||||
</orderedlist>
|
||||
|
||||
<para>If you are like me and don't have a development environment on
|
||||
your firewall, you can do the first six steps on another system then
|
||||
either NFS mount your /usr/local/src directory or tar up the
|
||||
/usr/local/src/ulogd-<emphasis>version</emphasis> directory and move it
|
||||
to your firewall system.</para>
|
||||
|
||||
<para>Now on the firewall system, edit /usr/local/etc/ulogd.conf and
|
||||
set:</para>
|
||||
|
||||
<orderedlist>
|
||||
<listitem>
|
||||
<para>syslogfile <<emphasis>the file that you wish to log to</emphasis>></para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>syslogsync 1</para>
|
||||
</listitem>
|
||||
</orderedlist>
|
||||
|
||||
<para>Also on the firewall system:</para>
|
||||
|
||||
<simplelist>
|
||||
<member>touch <<emphasis>the file that you wish to log to</emphasis>></member>
|
||||
</simplelist>
|
||||
|
||||
<para>I also copied the file /usr/local/src/ulogd-<emphasis>version</emphasis>/ulogd.init
|
||||
to /etc/init.d/ulogd. I had to edit the line that read "daemon
|
||||
/usr/local/sbin/ulogd" to read daemon /usr/local/sbin/ulogd -d".
|
||||
On a RedHat system, a simple "chkconfig --level 3 ulogd on"
|
||||
starts ulogd during boot up. Your init system may need something else
|
||||
done to activate the script.</para>
|
||||
|
||||
<para>You will need to change all instances of log levels (usually
|
||||
'info') in your configuration files to 'ULOG' - this
|
||||
includes entries in the policy, rules and shorewall.conf files.
|
||||
Here's what I have:</para>
|
||||
|
||||
<programlisting> [root@gateway shorewall]# grep ULOG *
|
||||
policy:loc fw REJECT ULOG
|
||||
policy:net all DROP ULOG 10/sec:40
|
||||
policy:all all REJECT ULOG
|
||||
rules:REJECT:ULOG loc net tcp 6667
|
||||
shorewall.conf:TCP_FLAGS_LOG_LEVEL=ULOG
|
||||
shorewall.conf:RFC1918_LOG_LEVEL=ULOG
|
||||
[root@gateway shorewall]#</programlisting>
|
||||
|
||||
<para>Finally edit /etc/shorewall/shorewall.conf and set LOGFILE=<<emphasis>file
|
||||
that you wish to log to</emphasis>>. This tells the /sbin/shorewall
|
||||
program where to look for the log when processing its "show
|
||||
log", "logwatch" and "monitor" commands.</para>
|
||||
</section>
|
||||
</section>
|
||||
|
||||
<section>
|
||||
<title>Syslog-ng</title>
|
||||
|
||||
<para><ulink
|
||||
url="http://marc.theaimsgroup.com/?l=gentoo-security&amp;m=106040714910563&amp;w=2">Here</ulink>
|
||||
is a post describing configuring syslog-ng to work with Shorewall.</para>
|
||||
</section>
|
||||
|
||||
<section>
|
||||
<title>Understanding the Contents of Shorewall Log Messages</title>
|
||||
|
||||
<para>Please see <ulink url="FAQ.htm#faq17">FAQ #17</ulink>.</para>
|
||||
</section>
|
||||
</article>
|
||||
Loading…
Reference in New Issue
Block a user