mirror of
https://gitlab.com/shorewall/code.git
synced 2024-12-23 14:48:51 +01:00
53495ec0a8
Signed-off-by: Matt Darfeuille <matdarf@gmail.com> Signed-off-by: Tom Eastep <teastep@shorewall.net>
386 lines
14 KiB
XML
386 lines
14 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
|
|
<refentry>
|
|
<refmeta>
|
|
<refentrytitle>shorewall-logging</refentrytitle>
|
|
|
|
<manvolnum>5</manvolnum>
|
|
|
|
<refmiscinfo>Configuration Files</refmiscinfo>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>logging</refname>
|
|
|
|
<refpurpose>Shorewall logging</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<cmdsynopsis>
|
|
<command><replaceable>action</replaceable>:<replaceable>level</replaceable></command>
|
|
</cmdsynopsis>
|
|
|
|
<cmdsynopsis>
|
|
<command>NFLOG(<replaceable>nflog-parameters</replaceable>)</command>
|
|
</cmdsynopsis>
|
|
|
|
<cmdsynopsis>
|
|
<command>ULOG(<replaceable>ulog-parameters</replaceable>)</command>
|
|
</cmdsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</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 connection. While the
|
|
packet can be logged using LOG rules in the ESTABLISHED section of
|
|
<ulink
|
|
url="manpages/shorewall-rules.html">/etc/shorewall/rules</ulink>, that
|
|
is not recommended because of the large amount of information that may
|
|
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 may be logged using LOG rules in the RELATED section of <ulink
|
|
url="manpages/shorewall-rules.html">shorewall-rules(5)</ulink>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The packet is rejected because of an option in <ulink
|
|
url="manpages/shorewall.conf.html">shorewall.conf</ulink>(5) or <ulink
|
|
url="manpages/shorewall-interfaces.html">shorewall-interfaces(5)</ulink>.
|
|
These packets can be logged by setting the appropriate logging-related
|
|
option in <ulink
|
|
url="manpages/shorewall.conf.html">/etc/shorewall/shorewall.conf</ulink>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The packet matches a rule in <ulink
|
|
url="manpages/shorewall-rules.html">shorewall-rules</ulink>(5). 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="manpages/shorewall-policy.html">shorewall-policy(5)</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>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Default Logging</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, the term
|
|
<emphasis>level</emphasis> rather than <emphasis>priority is used,
|
|
</emphasis>since <emphasis>level</emphasis> is the term used by Netfilter.
|
|
The syslog documentation uses the term
|
|
<emphasis>priority</emphasis>.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<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>Beginning with Shorewall 4.5.5, the <replaceable>level</replaceable>
|
|
name or number may be optionally followed by a comma-separated list of one
|
|
or more<replaceable> log options</replaceable>. The list is enclosed in
|
|
parentheses. Log options cause additional information to be included in
|
|
each log message.</para>
|
|
|
|
<para>Valid log options are:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><emphasis role="bold">ip_options</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Log messages will include the option settings from the IP
|
|
header.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">macdecode</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Decode the MAC address and protocol.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">tcp_sequence</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Include TCP sequence numbers.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">tcp_options</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Include options from the TCP header.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">uid</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Include the UID of the sending program; only valid for packets
|
|
originating on the firewall itself.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>Example: <emphasis
|
|
role="bold">info(tcp_options,tcp_sequence)</emphasis></para>
|
|
|
|
<para>Syslogd writes log messages to files (typically in <filename
|
|
class="directory">/var/log/</filename>*) 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>
|
|
|
|
<para>Syslog may also write to your system console. See <ulink
|
|
url="FAQ.htm#faq16">Shorewall FAQ 16</ulink> for ways to avoid having
|
|
Shorewall messages written to the console.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<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 its own log destination then
|
|
that destination will also receive all kernel messages of levels 5
|
|
(notice) through 0 (emerg).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>All kernel.info messages will go to that destination and not
|
|
just those from Netfilter.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Netfilter (Shorewall) messages show up in
|
|
<command>dmesg</command>.</para>
|
|
</listitem>
|
|
</orderedlist>
|
|
|
|
<para>If your kernel has NFLOG target support (and most vendor-supplied
|
|
kernels do), you may also specify a log level of NFLOG (must be all caps).
|
|
When NFLOG is used, Shorewall will direct Netfilter to log the related
|
|
messages via the NFLOG target which will send them to a process called
|
|
<quote>ulogd</quote>. The ulogd program is included in most
|
|
distributions.</para>
|
|
|
|
<note>
|
|
<para>The NFLOG logging mechanism is <emphasis
|
|
role="underline">completely separate</emphasis> from syslog. Once you
|
|
switch to NFLOG, the settings in <filename>/etc/syslog.conf</filename>
|
|
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 change all instances of log levels (usually
|
|
<quote>info</quote>) in your Shorewall configuration files to
|
|
<quote>NFLOG</quote> - this includes entries in the policy, rules and
|
|
shorewall.conf files. If you initially installed using Shorewall 5.1.2 or
|
|
later, you can simply change the setting of LOG_LEVEL in
|
|
shorewall.conf.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<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/en/2010/07/netfilter-log-format/">http://logi.cc/en/2010/07/netfilter-log-format/</ulink>.</para>
|
|
|
|
<para>For Shorewall-specific information, see <ulink
|
|
url="/FAQ.htm#faq17">FAQ #17</ulink>.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Customizing the Content of Shorewall Log Messages</title>
|
|
|
|
<para>In a Shorewall logging rule, the log level can be followed by a
|
|
<firstterm>log tag</firstterm> as in "DROP:NFLOG:junk". The generated log
|
|
message will include "<emphasis>chain-name</emphasis> junk DROP".</para>
|
|
|
|
<para>By setting the LOGTAGONLY option to Yes in <ulink
|
|
url="/manpages/shorewall.conf.html">shorewall.conf(5)</ulink> or <ulink
|
|
url="/manpages6/shorewall6.conf.html">shorewall6.conf(5)</ulink>, the
|
|
disposition ('DROP' in the above example) will be omitted. Consider the
|
|
following rule:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO
|
|
REJECT(icmp-proto-unreachable):notice:IPv6 loc net 41 # who's using IPv6 tunneling</programlisting>
|
|
|
|
<para>This rule generates the following warning at compile time:</para>
|
|
|
|
<simplelist>
|
|
<member>WARNING: Log Prefix shortened to "Shorewall:IPv6:REJECT(icmp-p "
|
|
/etc/shorewall/rules (line 212)</member>
|
|
</simplelist>
|
|
|
|
<para>and produces the rather ugly prefix "Shorewall:IPv6:REJECT(icmp-p
|
|
".</para>
|
|
|
|
<para>Now consider this similar rule:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO
|
|
REJECT(icmp-proto-unreachable):notice:IPv6,tunneling loc net 41 # who's using IPv6 tunneling</programlisting>
|
|
|
|
<para>With LOGTAGONLY=Yes, no warning is generated and the prefix becomes
|
|
"Shorewall:IPv6:tunneling:"</para>
|
|
|
|
<para>See the <ulink url="shorewall.conf.html">shorewall[6].conf man
|
|
page</ulink> for further information about how LOGTAGONLY=Yes can be
|
|
used.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Log Backends</title>
|
|
|
|
<para>Netfilter logging allows configuration of multiple backends. Logging
|
|
backends provide the The low-level forward of log messages. There are
|
|
currently three backends:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>LOG (ipt_LOG and ip6t_LOG).</term>
|
|
|
|
<listitem>
|
|
<para>Normal kernel-based logging to a syslog daemon.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ULOG (ipt_ULOG)</term>
|
|
|
|
<listitem>
|
|
<para>ULOG logging as described ablve. Only available for
|
|
IPv4.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>netlink (nfnetlink_log)</term>
|
|
|
|
<listitem>
|
|
<para>The logging backend behind NFLOG, defined above.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>The currently-available and currently-selected IPv4 and IPv6
|
|
backends are shown in /proc/sys/net/netfilter/nf_log:</para>
|
|
|
|
<programlisting>cat /proc/net/netfilter/nf_log
|
|
0 NONE (nfnetlink_log)
|
|
1 NONE (nfnetlink_log)
|
|
2 ipt_ULOG (ipt_ULOG,ipt_LOG,nfnetlink_log)
|
|
3 NONE (nfnetlink_log)
|
|
4 NONE (nfnetlink_log)
|
|
5 NONE (nfnetlink_log)
|
|
6 NONE (nfnetlink_log)
|
|
7 NONE (nfnetlink_log)
|
|
8 NONE (nfnetlink_log)
|
|
9 NONE (nfnetlink_log)
|
|
10 ip6t_LOG (ip6t_LOG,nfnetlink_log)
|
|
11 NONE (nfnetlink_log)
|
|
12 NONE (nfnetlink_log)</programlisting>
|
|
|
|
<para>The magic numbers (0-12) are Linux address family numbers (AF_INET
|
|
is 2 and AF_INET6 is 10).</para>
|
|
|
|
<para>The name immediately following the number is the currently-selected
|
|
backend, and the ones in parentheses are the ones that are available. You
|
|
can change the currently selected backend by echoing it's name into
|
|
/proc/net/netfilter/nf_log.<replaceable>number</replaceable>.</para>
|
|
|
|
<para>Example - change the IPv4 backend to LOG:</para>
|
|
|
|
<programlisting>sysctl net.netfilter.nf_log.2=ipt_LOG</programlisting>
|
|
|
|
<para>Beginning with Shorewall 4.6.4, you can configure the backend using
|
|
the LOG_BACKEND option in <ulink
|
|
url="manpages/shorewall.conf.html">shorewall.conf(5)</ulink> and <ulink
|
|
url="manpages6/shorewall6.conf.html">shorewall6.conf(5)</ulink>.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>SEE ALSO</title>
|
|
|
|
<para><ulink
|
|
url="/shorewall_logging.htm">http://www.shorewall.org/shorewall_logging.html</ulink></para>
|
|
</refsect1>
|
|
</refentry>
|