mirror of
https://gitlab.com/shorewall/code.git
synced 2024-12-29 17:48:53 +01:00
9fd5780f36
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@1439 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
290 lines
11 KiB
XML
290 lines
11 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
|
<article id="IPIP">
|
|
<!--$Id$-->
|
|
|
|
<articleinfo>
|
|
<title>Shorewall Logging</title>
|
|
|
|
<authorgroup>
|
|
<author>
|
|
<firstname>Tom</firstname>
|
|
|
|
<surname>Eastep</surname>
|
|
</author>
|
|
</authorgroup>
|
|
|
|
<pubdate>2004-06-28</pubdate>
|
|
|
|
<copyright>
|
|
<year>2001 - 2004</year>
|
|
|
|
<holder>Thomas M. Eastep</holder>
|
|
</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
|
|
<quote><ulink url="GnuCopyright.htm">GNU Free Documentation License</ulink></quote>.</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 cannot 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., <quote>ACCEPT<emphasis role="bold">:info</emphasis> net fw tcp
|
|
22</quote>), 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., <quote>loc net ACCEPT
|
|
<emphasis role="bold">info</emphasis></quote>).</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 (ulogd)</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 <quote>ulogd</quote>.
|
|
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 <quote>daemon
|
|
/usr/local/sbin/ulogd</quote> to read <quote>daemon
|
|
/usr/local/sbin/ulogd -d</quote>. On a RedHat system, a simple
|
|
<quote>chkconfig --level 3 ulogd on</quote> 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
|
|
<quote>info</quote>) in your configuration files to <quote>ULOG</quote>
|
|
- 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 <quote>show log</quote>,
|
|
<quote>logwatch</quote> and <quote>monitor</quote> 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>For general information on the contents of Netfilter log messages,
|
|
see <ulink url="http://logi.cc/linux/netfilter-log-format.php3">http://logi.cc/linux/netfilter-log-format.php3</ulink>.</para>
|
|
|
|
<para>For Shorewall-specific information, see <ulink url="FAQ.htm#faq17">FAQ
|
|
#17</ulink>.</para>
|
|
</section>
|
|
</article> |