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992 lines
36 KiB
XML
992 lines
36 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
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<article>
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<!--$Id$-->
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<articleinfo>
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<title>Actions</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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<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
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<copyright>
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<year>2005</year>
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<year>2007</year>
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<year>2008</year>
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<year>2009</year>
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<year>2010</year>
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<year>2012</year>
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<year>2013</year>
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<holder>Thomas M. Eastep</holder>
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</copyright>
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<legalnotice>
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<para>Permission is granted to copy, distribute and/or modify this
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document under the terms of the GNU Free Documentation License, Version
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1.2 or any later version published by the Free Software Foundation; with
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no Invariant Sections, with no Front-Cover, and with no Back-Cover
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Texts. A copy of the license is included in the section entitled
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<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
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License</ulink></quote>.</para>
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</legalnotice>
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</articleinfo>
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<caution>
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<para><emphasis role="bold">This article applies to Shorewall 4.3 and
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later. If you are running a version of Shorewall earlier than Shorewall
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4.3.5 then please see the documentation for that
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release.</emphasis></para>
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</caution>
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<section id="Intro">
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<title>What are Shorewall Actions?</title>
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<para>Shorewall actions allow a symbolic name to be associated with a
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series of one or more iptables rules. The symbolic name may appear in the
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ACTION column of an <filename><ulink
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url="manpages/shorewall-rules.html">/etc/shorewall/rules</ulink></filename>
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entry, in a <ulink url="Macros.html">macro</ulink> body and within another
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action, in which case the traffic matching that rules file entry will be
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passed to the series of iptables rules named by the action.</para>
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<para>Actions can be thought of as templates. When an action is invoked in
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an <filename>/etc/shorewall/rules</filename> entry, it may be qualified by
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a logging specification (log level and optionally a log tag). The presence
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of the log level/tag causes a modified series of rules to be generated in
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which each packet/rule match within the action causes a log message to be
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generated.</para>
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<para>For readers familiar with iptables, actions are the way in which you
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can create your own filter-table chains.</para>
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<para>There are three types of Shorewall actions:</para>
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<orderedlist>
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<listitem>
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<para>Built-in Actions. These actions are known by the Shorewall code
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itself. They are listed in the comments at the top of the file
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<filename>/usr/share/shorewall/actions.std</filename>.</para>
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</listitem>
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<listitem>
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<para>Standard Actions. These actions are released as part of
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Shorewall. They are listed in the file
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<filename>/usr/share/shorewall/actions.std</filename> and are defined
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in the corresponding action.* files in <filename
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class="directory">/usr/share/shorewall</filename>. Each
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<filename>action.*</filename> file has a comment at the beginning of
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the file that describes what the action does. As an example, here is
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the definition of the <firstterm>AllowSMB</firstterm> standard action
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from Shorewall version 2.2.</para>
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<programlisting>#
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# Shorewall 2.2 /usr/share/shorewall/action.AllowSMB
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#
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# Allow Microsoft SMB traffic. You need to invoke this action in
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# both directions.
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#
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######################################################################################
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#TARGET SOURCE DEST PROTO DPORT SPORT RATE USER
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ACCEPT - - udp 135,445
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ACCEPT - - udp 137:139
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ACCEPT - - udp 1024: 137
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ACCEPT - - tcp 135,139,445</programlisting>
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<para>If you wish to modify one of the standard actions, do not modify
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the definition in <filename
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class="directory">/usr/share/shorewall</filename>. Rather, copy the
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file to <filename class="directory">/etc/shorewall</filename> (or
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somewhere else on your CONFIG_PATH) and modify the copy.</para>
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<para>Standard Actions have been largely replaced by <ulink
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url="Macros.html">macros</ulink> .</para>
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</listitem>
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<listitem>
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<para>User-defined Actions. These actions are created by end-users.
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They are listed in the file
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<filename>/etc/shorewall/actions</filename> and are defined in
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<filename>action.*</filename> files in <filename
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class="directory">/etc/shorewall</filename> or in another directory
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listed in your CONFIG_PATH (defined in <filename><ulink
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url="manpages/shorewall.conf.html">/etc/shorewall/shorewall.conf</ulink></filename>).</para>
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</listitem>
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</orderedlist>
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</section>
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<section id="Default">
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<title>Default Actions (Formerly Common Actions)</title>
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<para>Shorewall allows the association of a <firstterm>default
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action</firstterm> with policies. A separate default action may be
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associated with ACCEPT, DROP, REJECT, QUEUE and NFQUEUE policies. Default
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actions provide a way to invoke a set of common rules just before the
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policy is enforced. Default actions accomplish two goals:</para>
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<orderedlist>
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<listitem>
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<para>Relieve log congestion. Default actions typically include rules
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to silently drop or reject traffic that would otherwise be logged when
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the policy is enforced.</para>
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</listitem>
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<listitem>
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<para>Ensure correct operation.</para>
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</listitem>
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</orderedlist>
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<para>Shorewall supports default actions for the ACCEPT, REJECT, DROP,
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QUEUE and NFQUEUE policies. These default actions are specified in the
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<filename>/etc/shorewall/shorewall.conf</filename> file using the
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ACCEPT_DEFAULT, REJECT_DEFAULT, DROP_DEFAULT, QUEUE_DEFAULT and
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NFQUEUE_DEFAULT options respectively. Policies whose default is set to a
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value of <quote>none</quote> have no default action.</para>
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<para>In addition, the default specified in
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<filename>/etc/shorewall/shorewall.conf</filename> may be overridden by
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specifying a different action in the POLICY column of <filename><ulink
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url="manpages/shorewall-policy.html">/etc/shorewall/policy</ulink></filename>.</para>
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<important>
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<para>Entries in the DROP and REJECT default actions <emphasis
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role="bold">ARE NOT THE CAUSE OF CONNECTION PROBLEMS</emphasis>.
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Remember — default actions are only invoked immediately before the
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packet is going to be dropped or rejected anyway!!!</para>
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</important>
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<para>Beginning with Shorewall 4.4.21, the standard Drop and Reject
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options are parameterized. Each has five parameters as follows:</para>
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<informaltable>
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<tgroup cols="4">
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<tbody>
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<row>
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<entry>ACTION</entry>
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<entry>PARAMETER</entry>
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<entry>VALUE</entry>
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<entry>DEFAULT</entry>
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</row>
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<row>
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<entry>Drop</entry>
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<entry>1</entry>
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<entry>Either '-' or 'audit'. 'audit' causes auditing by the
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builtin actions invoked by Drop</entry>
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<entry>-</entry>
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</row>
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<row>
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<entry>Drop</entry>
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<entry>2</entry>
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<entry>Determines what to do with Auth requests</entry>
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<entry>-</entry>
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</row>
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<row>
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<entry>Drop</entry>
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<entry>3</entry>
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<entry>Determines what to do with SMB</entry>
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<entry>DROP or A_DROP depending on the setting of parameter
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1</entry>
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</row>
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<row>
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<entry>Reject</entry>
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<entry>1</entry>
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<entry>Either '-' or 'audit'. 'audit' causes auditing by the
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builtin actions invoked by Drop</entry>
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<entry>-</entry>
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</row>
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<row>
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<entry>Reject</entry>
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<entry>2</entry>
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<entry>Determines what to do with Auth requests</entry>
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<entry>-</entry>
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</row>
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<row>
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<entry>Reject</entry>
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<entry>3</entry>
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<entry>Determines what to do with SMB</entry>
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<entry>REJECT or A_REJECT depending on the setting of parameter
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1</entry>
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</row>
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<row>
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<entry>Both</entry>
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<entry>4</entry>
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<entry>Determines what to do with accepted critical ICMP
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packets.</entry>
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<entry>ACCEPT or A_ACCEPT depending on the setting of parameter
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1</entry>
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</row>
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<row>
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<entry>Both</entry>
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<entry>5</entry>
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<entry>Determines what to do with late-arriving DNS replies
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(source port 53) or UPnP (udp port 1900).</entry>
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<entry>DROP or A_DROP depending on the setting of parameter
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1.</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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<para>The parameters may be specified in either shorewall.conf (e.g.,
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DROP_DEFAULT=<emphasis role="bold">Drop(-,DROP)</emphasis> or in the
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POLICY column of <ulink
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url="manpages/shorewall-policy.html">shorewall-policy</ulink>(5) (e.g.,
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DROP:<emphasis role="bold">Drop(audit)</emphasis>:audit).</para>
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</section>
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<section id="Defining">
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<title>Defining your own Actions</title>
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<para>Before defining a new action, you should evaluate whether your goal
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can be best accomplished using an action or a
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<firstterm>macro</firstterm>. See <ulink url="Macros.html">this
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article</ulink> for details.</para>
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<para>To define a new action:</para>
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<orderedlist>
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<listitem>
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<para>Add a line to <filename>/etc/shorewall/actions</filename> that
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names your new action. Action names must be valid shell variable names
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(must begin with a letter and be composed of letters, digits and
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underscore characters) as well as valid Netfilter chain names. If you
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intend to log from the action, the name must have a maximum of 11
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characters. It is recommended that the name you select for a new
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action begins with a capital letter; that way, the name won't conflict
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with a Shorewall-defined chain name.</para>
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<para>Normally. the rules in an action are placed in a separate chain.
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Beginning with Shorewall 4.5.10, the action rules can be expanded
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inline in a manner similar to a macro by specifying
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<option>inline</option> in the OPTIONS column of
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<filename>/etc/shorewall/actions</filename>.</para>
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<para>Beginning in Shorewall 4.5.11, the <option>nolog</option> option
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may be specified; see the <link linkend="Logging">logging
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section</link> below for details.</para>
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<para>Shorewall includes pre-defined actions for DROP and REJECT --
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see above.</para>
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</listitem>
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<listitem>
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<para>Once you have defined your new action name (ActionName), then
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copy <filename>/usr/share/shorewall/action.template</filename> to
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<filename>/etc/shorewall/action.ActionName</filename> (for example, if
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your new action name is <quote>Foo</quote> then copy
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<filename>/usr/share/shorewall/action.template</filename> to
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<filename>/etc/shorewall/action.Foo</filename>).</para>
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</listitem>
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<listitem>
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<para>Now modify the new file to define the new action.</para>
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</listitem>
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</orderedlist>
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<section>
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<title>Shorewall 5.0.0 and Later.</title>
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<para>In Shorewall 5.0, the columns in action.template are the same as
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those in shorewall-rules (5). There are no restrictions regarding which
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targets can be used within your action.</para>
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<para>The SOURCE and DEST columns in the action file may not include
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zone names; those are given when the action is invoked.</para>
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<para>Additionally, it is possible to pass parameters to an action, when
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it is invoked in the rules file or in another action.</para>
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<para>Here's a trivial example:</para>
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<para>/etc/shorewall/action.A:</para>
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<programlisting>#TARGET SOURCE DEST PROTO Dport SPORT ORIGDEST
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$1 - - tcp 80 - 1.2.3.4</programlisting>
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<para>/etc/shorewall/rules:</para>
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<programlisting>#TARGET SOURCE DEST PROTO DPORT SPORT ORIGDEST
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A(REDIRECT) net fw</programlisting>
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<para>The above is equivalent to this rule:</para>
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<programlisting>#TARGET SOURCE DEST PROTO DPORT SPORT ORIGDEST
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REDIRECT net - tcp 80 - 1.2.3.4</programlisting>
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<para>You can 'omit' parameters by using '-'.</para>
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<para>Example: ACTION(REDIRECT,-,info)</para>
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<para>In the above example, $2 would expand to nothing.</para>
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<para>Beginning with Shorewall 4.5.13, completely omitting a arameter is
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equivalent to passing '-'.</para>
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<para>Example: ACTION(REDIRECT,,info)</para>
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<para>This example behaves the same as the one shown above.</para>
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<para>If you refer to a parameter $n in the body of the action, then the
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nth paramer must either be passed to all action invocations or it's
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default value must be established via a DEFAULTS line.</para>
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<para>If you want to make '-' a parameter value, use '--' (e.g.,
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ACTION(REDIRECT,--.info)).</para>
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<para>Beginning with Shorewall 4.4.21, you can specify the default
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values of your FORMAT-2 actions:</para>
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<programlisting>DEFAULTS <replaceable>def1</replaceable>,<replaceable>def2</replaceable>,...</programlisting>
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<para>where <replaceable>def1</replaceable> is the default value for the
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first parameter, <replaceable>def2</replaceable> is the default value
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for the second parameter and so on. You can specify an empty default
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using '-' (e.g. DEFAULTS DROP,-,audit).</para>
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<para>For additional information about actions, see the <ulink
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url="configuration_file_basics.htm#ActionVariables">Action Variables
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section</ulink> of the Configuration Basics article.</para>
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</section>
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</section>
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<section id="Logging">
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<title>Actions and Logging</title>
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<para>Specifying a log level in a rule that specifies a user-defined or
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Shorewall-defined action will cause each rule in the action to be logged
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with the specified level (and tag), unless the <option>nolog</option>
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option is specified in the action's entry in
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<filename>/etc/shorewall/actions</filename>.</para>
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<para>The extent to which logging of action rules occur is governed by the
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following:</para>
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<orderedlist>
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<listitem>
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<para>When you invoke an action and specify a log level, only those
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rules in the action that have no log level will be changed to log at
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the level specified at the action invocation.</para>
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<para>Example:</para>
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<para>/etc/shorewall/action.foo</para>
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<programlisting>#TARGET SOURCE DEST PROTO DPORT
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ACCEPT - - tcp 22
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bar:info</programlisting>
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<para>/etc/shorewall/rules:</para>
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<programlisting>#ACTION SOURCE DEST PROTO DPORT
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foo:debug $FW net</programlisting>
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<para>Logging in the invoke <quote>foo</quote> action will be as if
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foo had been defined as:</para>
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<programlisting>#TARGET SOURCE DEST PROTO DPORT
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ACCEPT:debug - - tcp 22
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bar:info</programlisting>
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</listitem>
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<listitem>
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<para>If you follow the log level with <quote>!</quote> then logging
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will be set at that level for all rules recursively invoked by the
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action.</para>
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<para>Example:</para>
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<para>/etc/shorewall/action.foo</para>
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<programlisting>#TARGET SOURCE DEST PROTO DPORT
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ACCEPT - - tcp 22
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bar:info</programlisting>
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<para>/etc/shorewall/rules:</para>
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<programlisting>#ACTION SOURCE DEST PROTO DPORT
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foo:debug! $FW net</programlisting>
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<para>Logging in the invoke <quote>foo</quote> action will be as if
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foo had been defined as:</para>
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<programlisting>#TARGET SOURCE DEST PROTO DPORT
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ACCEPT:debug - - tcp 22
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bar:debug</programlisting>
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</listitem>
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</orderedlist>
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</section>
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<section id="Embedded">
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<title>Using Embedded Perl in an Action</title>
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<para>There may be cases where you wish to create a chain with rules that
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can't be constructed using the tools defined in the
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<filename>action.template</filename>. Such rules can be constructed using
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<ulink url="configuration_file_basics.htm#Embedded">Embedded Perl.</ulink>
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For those who are comfortable using Perl, embedded Perl is more efficient
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that using complicated conditional entries. The Perl compiler is invoked
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only once for a BEGIN PERL...END PERL block; it is invoked most times that
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an expression is evaluated in an ?IF, ?ELSEIF or ?SET directive.</para>
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<para>The Shorewall compiler provides a set of services that are available
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to Perl code embedded in an action file. These services are not available
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in in-line actions when running Shorewall 4.5.12 or earlier.</para>
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<variablelist>
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<varlistentry>
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<term>Shorewall::Config::get_action_params(
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<replaceable>$howmany</replaceable> )</term>
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<listitem>
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<para>This function returns an array containing the functions
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parameters. The scalar argument <replaceable>$howmany</replaceable>
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is the number of parameters that you expect to be passed. You can
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ensure that at least this many parameters are passed by including a
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DEFAULTS line prior to the embedded Perl.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Shorewall::Config::set_action_param(
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<replaceable>$ordinal</replaceable>, <replaceable>$value</replaceable>
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)</term>
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<listitem>
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<para>Set the value of parameter <replaceable>$ordinal</replaceable>
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to <replaceable>$value</replaceable>. Care must be take when using
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this function such that for a given set of parameters actually
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passed to the action, the same rules are created. That is because
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the compiler assumes that all invocations of an action with the same
|
|
parameters, log level and log tag can share the same action
|
|
chain.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Shorewall::Config::get_action_chain()</term>
|
|
|
|
<listitem>
|
|
<para>This function returns a reference to the chain table entry for
|
|
the current action chain.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Shorewall::Config::get_action_logging()</term>
|
|
|
|
<listitem>
|
|
<para>Returns a two-element list containing the the log level and
|
|
log tag specified when the action was invoked. Note that you must
|
|
use this function rather than @loglevel and @logtag within embedded
|
|
Perl, as the compiler does not expand <ulink
|
|
url="configuration_file_basics.htm#ShorewallVariables">Shorewall
|
|
Variables</ulink> within embedded Perl (or embedded shell).</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Shorewall::Config::push_comment()</term>
|
|
|
|
<listitem>
|
|
<para>Prior to Shorewall 4.5.21, this required:</para>
|
|
|
|
<programlisting>use Shorewall::Config (:DEFAULT :internal);</programlisting>
|
|
|
|
<para>Returns the current rule comment to the caller and clears the
|
|
comment. The returned comment may be restored by calling either
|
|
pop_comment() or set_comment().</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Shorewall::Config::pop_comment($comment) and
|
|
Shorewall::Config::set_comment($comment).</term>
|
|
|
|
<listitem>
|
|
<para>The set_comment() function was added in Shorewall 4.5.21.
|
|
Prior to that release, accessing pop_comment() required:</para>
|
|
|
|
<programlisting>use Shorewall::Config (:DEFAULT :internal);</programlisting>
|
|
|
|
<para>These functions are identical and set the current rule comment
|
|
to the contents of the passed simple variable.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Shorewall::Chains::add_rule(
|
|
<replaceable>$chainre</replaceable>f, <replaceable>$rule</replaceable>
|
|
[, <replaceable>$expandports</replaceable> ] )</term>
|
|
|
|
<listitem>
|
|
<para>This function adds a rule to a chain. As of Shoreall 4.5.13,
|
|
it is deprecated in favor of Shorewall::Rules::perl_action_helper().
|
|
Arguments are:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable>$chainref</replaceable></term>
|
|
|
|
<listitem>
|
|
<para>Normally, you get this from get_action_chain() described
|
|
above.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable>$rule</replaceable></term>
|
|
|
|
<listitem>
|
|
<para>The matches and target for the rule that you want
|
|
added.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable>$expandports</replaceable> (optional)</term>
|
|
|
|
<listitem>
|
|
<para>This optional argument is for compiler-internal use
|
|
only. Either omit it or pass a false value.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<warning>
|
|
<para>Do not call this function in a inline action. Use
|
|
perl_action_helper() instead (see below).</para>
|
|
</warning>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Shorewall::Chains::log_rule_limit(
|
|
<replaceable>$level</replaceable>,
|
|
$<replaceable>chainref</replaceable>,
|
|
<replaceable>$chain</replaceable>,
|
|
<replaceable>$disposition</replaceable>,
|
|
<replaceable>$limit</replaceable>, <replaceable>$tag</replaceable>,
|
|
<replaceable>$command</replaceable>,
|
|
<replaceable>$matches</replaceable> )</term>
|
|
|
|
<listitem>
|
|
<para>This function adds a logging rule to a chain. As of Shoreall
|
|
4.5.13, it is deprecated in favor of
|
|
Shorewall::Rules::perl_action_helper(). Arguments are:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><replaceable>$level</replaceable></term>
|
|
|
|
<listitem>
|
|
<para>Either a syslog level or a ULOG or NFLOG target
|
|
expression (e.g., "NFLOG(1,0,1)"). Specifies how you want the
|
|
logging done.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable>$chainref</replaceable></term>
|
|
|
|
<listitem>
|
|
<para>Normally, you get this from get_action_chain() described
|
|
above.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable>$chain</replaceable></term>
|
|
|
|
<listitem>
|
|
<para>The value you want substituted for the first %s
|
|
formatting directive in the LOGFORMAT setting in
|
|
<filename>/etc/shorewall/shorewall.conf</filename>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable>$disposition</replaceable></term>
|
|
|
|
<listitem>
|
|
<para>This is the value substituted for the second '%s'
|
|
formatting directive in the LOGFORMAT setting in
|
|
<filename>/etc/shorewall/shorewall.conf</filename>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable>$limit</replaceable></term>
|
|
|
|
<listitem>
|
|
<para>If you want to use the default limit set in LOGLIMIT
|
|
(<filename>/etc/shorewall/shorewall.conf</filename>), you can
|
|
specify your own '-limit' match. Otherwise, if you want to use
|
|
the default, pass 0 or "". If you want the rule to be
|
|
unlimited, pass '-'.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable>$tag</replaceable></term>
|
|
|
|
<listitem>
|
|
<para>Log tag.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><replaceable>$command</replaceable></term>
|
|
|
|
<listitem>
|
|
<para>Pass 'add' here, unless you want the rule to be inserted
|
|
at the front of the chain.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><firstterm>$matches</firstterm></term>
|
|
|
|
<listitem>
|
|
<para>Zero or more iptables matches that limit when logging
|
|
will occur. If this parameter is other than the empty string,
|
|
the last character must be a space.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Shorewall::Chains::allow::optimize(
|
|
<replaceable>$chainref</replaceable> )</term>
|
|
|
|
<listitem>
|
|
<para>This allows the passed action chain to be optimized away
|
|
(jumps to the chain are replaced by the chain's rule(s)). The
|
|
<replaceable>chainref</replaceable> argument is usually obtained
|
|
from get_action_chain() described above.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Shorewall::Rules::perl_action_helper( $target, $matches )</term>
|
|
|
|
<listitem>
|
|
<para>This function adds a rule to the current chain. For a regular
|
|
action, the chain will be an action chain; for an inline action, the
|
|
chain is determined by the invoking rule.</para>
|
|
|
|
<para>To use this function, you must include:</para>
|
|
|
|
<simplelist>
|
|
<member><emphasis role="bold">use
|
|
Shorewall::Rules;</emphasis></member>
|
|
</simplelist>
|
|
|
|
<para>Arguments are:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>$target</term>
|
|
|
|
<listitem>
|
|
<para>The target of the rule. Legal values are anything that
|
|
can appear in the TARGET column of in an action body and may
|
|
include log level, tag, and parameters.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>$matches</term>
|
|
|
|
<listitem>
|
|
<para>ip[6]tables matches to be included in the rule. When
|
|
called in an inline action, these matches are augmented by
|
|
matches generated by the invoking rule.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<note>
|
|
<para>This function has additional optional arguments which are
|
|
used internally by Shorewall standard actions. Their number and
|
|
behavior is likely to change in future Shorewall releases.</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Shorewall::Rules::perl_action_tcp_helper( $target, $proto
|
|
)</term>
|
|
|
|
<listitem>
|
|
<para>This function is similar to
|
|
Shorewall::Rules::perl_action_helper but is taylored for specifying
|
|
options to "-p tcp".</para>
|
|
|
|
<para>To use this function, you must include:</para>
|
|
|
|
<simplelist>
|
|
<member><emphasis role="bold">use
|
|
Shorewall::Rules;</emphasis></member>
|
|
</simplelist>
|
|
|
|
<para>Arguments are:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>$target</term>
|
|
|
|
<listitem>
|
|
<para>The target of the rule. Legal values are anything that
|
|
can appear in the TARGET column of in an action body and may
|
|
include log level, tag, and parameters.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>$proto</term>
|
|
|
|
<listitem>
|
|
<para>The '-p' part of the rule to be generated (e.g., "-p tcp
|
|
--tcp-flags RST RST").</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>For examples of using these services, look at the standard actions
|
|
in <filename>/usr/share/shorewall/action.*</filename>.</para>
|
|
</section>
|
|
|
|
<section id="Extension">
|
|
<title>Creating an Action using an Extension Script (deprecated in favor
|
|
of BEGIN PERL ... END PERL)</title>
|
|
|
|
<para>There may be cases where you wish to create a chain with rules that
|
|
can't be constructed using the tools defined in the
|
|
<filename>action.template</filename>. In that case, you can use an <ulink
|
|
url="shorewall_extension_scripts.htm">extension script</ulink>. Beginning
|
|
with Shorewall 4.5.16, such scripts require CHAIN_SCRIPTS=Yes in <ulink
|
|
url="manpages/shorewall.conf.html">shorewall.conf</ulink> (5)<note>
|
|
<para>If you actually need an action to drop broadcast packets, use
|
|
the <command>dropBcast</command> standard action rather than create
|
|
one like this.</para>
|
|
</note></para>
|
|
|
|
<example id="Example">
|
|
<title>An action to drop all broadcast packets</title>
|
|
|
|
<para>If you define an action <quote>acton</quote> and you have an
|
|
<filename>/etc/shorewall/acton</filename> script, the rules compiler
|
|
sets lexical variables as follows:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><emphasis role="bold">$chainref</emphasis> is a reference to
|
|
the chain-table entry for the chain where your rules are to be
|
|
placed.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><emphasis role="bold">$level</emphasis> is the log level. If
|
|
false, no logging was specified.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><emphasis role="bold">$tag</emphasis> is the log tag.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><emphasis role="bold">@params</emphasis> is the list of
|
|
parameter values (Shorewall 4.4.16 and later). 'Omitted' parameters
|
|
contain '-'.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>Example:</para>
|
|
|
|
<para>/etc/shorewall/actions<programlisting>DropBcasts</programlisting></para>
|
|
|
|
<para>/etc/shorewall/action.DropBcasts<programlisting># This file is empty</programlisting>/etc/shorewall/DropBcasts<programlisting>use Shorewall::Chains;
|
|
|
|
if ( $level ne '' ) {
|
|
log_rule_limit $level, $chainref, 'dropBcast' , 'DROP', '', $tag, 'add', ' -m addrtype --dst-type BROADCAST ';
|
|
log_rule_limit $level, $chainref, 'dropBcast' , 'DROP', '', $tag, 'add', ' -d 224.0.0.0/4 ';
|
|
}
|
|
|
|
add_rule $chainref, '-m addrtype --dst-type BROADCAST -j DROP';
|
|
add_rule $chainref, '-d 224.0.0.0/4 -j DROP';
|
|
|
|
1;</programlisting></para>
|
|
</example>
|
|
|
|
<para>For a richer example, see the next section.</para>
|
|
</section>
|
|
|
|
<section id="Limit">
|
|
<title>Limiting Per-IP Connection Rate using the Limit Action</title>
|
|
|
|
<para>Shorewall supports a <quote>Limit</quote> built-in action. Prior to
|
|
Shorewall 4.4.16, Limit is invoked with a comma-separated list in place of
|
|
a logging tag. Beginning in Shorewall 4.4.16, it may also be invoked with
|
|
a list of three parameters enclosed in parentheses. The list has three
|
|
elements:</para>
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>The name of a <quote>recent</quote> list. You select the list
|
|
name which must conform to the rules for a valid chain name. Different
|
|
rules that specify the same list name will use the same set of
|
|
counters.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The number of connections permitted in a specified time
|
|
period.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The time period, expressed in seconds.</para>
|
|
</listitem>
|
|
</orderedlist>
|
|
|
|
<para>Connections that exceed the specified rate are dropped.</para>
|
|
|
|
<para>For example, to use a recent list name of <emphasis
|
|
role="bold">SSHA</emphasis>, and to limit SSH connections to 3 per minute,
|
|
use this entry in <filename>/etc/shorewall/rules</filename>:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT
|
|
Limit:none:SSHA,3,60 net $FW tcp 22</programlisting>
|
|
|
|
<para>Using Shorewall 4.4.16 or later, you can also invoke the action this
|
|
way:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT
|
|
Limit(SSHA,3,60):none net $FW tcp 22</programlisting>
|
|
|
|
<para>If you want dropped connections to be logged at the info level, use
|
|
this rule instead:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT
|
|
Limit:info:SSHA,3,60 net $FW tcp 22</programlisting>
|
|
|
|
<para>Shorewall 4.4.16 and later:<programlisting>#ACTION SOURCE DEST PROTO DPORT
|
|
Limit(SSH,3,60):info net $FW tcp 22</programlisting></para>
|
|
|
|
<para>To summarize, you pass four pieces of information to the Limit
|
|
action:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>The log level. If you don't want to log, specify
|
|
<quote>none</quote>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The name of the recent list that you want to use
|
|
(<quote>SSHA</quote> in this example).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The maximum number of connections to accept (3 in this
|
|
example).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The number of seconds over which you are willing to accept that
|
|
many connections (60 in this example).</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<section id="LimitImp">
|
|
<title>How Limit is Implemented</title>
|
|
|
|
<para>For those who are curious, the Limit action in Shorewall 4.4.16 is
|
|
implemented as follows:</para>
|
|
|
|
<programlisting>use Shorewall::Chains;
|
|
|
|
@params = split( /,/, $tag ), $tag='' unless @params;
|
|
|
|
fatal_error 'Limit rules must include <list name>,<max connections>,<interval> as the log tag or params' unless @params == 3;
|
|
|
|
my $list = $params[0];
|
|
|
|
for ( @params[1,2] ) {
|
|
fatal_error 'Max connections and interval in Limit rules must be numeric (' . $_ . ')' unless /^\d+$/
|
|
}
|
|
|
|
my $count = $params[1] + 1;
|
|
|
|
add_rule $chainref, "-m recent --name $list --set";
|
|
|
|
if ( $level ) {
|
|
my $xchainref = new_chain 'filter' , "$chainref->{name}%";
|
|
log_rule_limit $level, $xchainref, $params[0], 'DROP', $tag, '', 'add', '';
|
|
add_rule $xchainref, '-j DROP';
|
|
add_rule $chainref, "-m recent --name $list --update --seconds $params[2] --hitcount $count -j $xchainref->{name}";
|
|
} else {
|
|
add_rule $chainref, "-m recent --update --name $list --seconds $params[2] --hitcount $count -j DROP";
|
|
}
|
|
|
|
add_rule $chainref, '-j ACCEPT';
|
|
|
|
1; </programlisting>
|
|
</section>
|
|
</section>
|
|
</article>
|