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545 lines
21 KiB
XML
545 lines
21 KiB
XML
<?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>
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<!--$Id$-->
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<articleinfo>
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<title>Compiled Firewall Programs and Shorewall Lite</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>2006-06-17</pubdate>
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<copyright>
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<year>2006</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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<section>
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<title>Overview</title>
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<para>Beginning with Shorewall version 3.1, Shorewall has the capability
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to compile a Shorewall configuration and produce a runnable firewall
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program script. The script is a complete program which can be placed on a
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system with <emphasis>Shorewall Lite</emphasis> installed and can serve as
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the firewall creation script for that system.</para>
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<section>
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<title>Restrictions</title>
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<para>While compiled Shorewall programs are useful in many cases, there
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are some important restrictions that you should be aware of before
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attempting to use them.</para>
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<orderedlist>
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<listitem>
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<para>The <emphasis role="bold">detectnets</emphasis> interface
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option is not supported.</para>
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</listitem>
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<listitem>
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<para>DYNAMIC_ZONES=Yes in <filename>shorewall.conf</filename> is
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not supported.</para>
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</listitem>
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<listitem>
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<para>All extension scripts used are copied into the program. The
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ramifications of this are:</para>
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<itemizedlist>
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<listitem>
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<para>If you update an extension script, the compiled program
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will not use the updated script.</para>
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</listitem>
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<listitem>
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<para>The <filename>/etc/shorewall/params</filename> extension
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script is executed at compile time as well as at run
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time.</para>
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<para>Running the script at compile time allows variable
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expansion (expanding $variable to it's defined value) of
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variables used in Shorewall configuration files to occur at
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compile time. Running it at run-time allows your extension
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scripts to use the variables that it creates. BUT -- for any
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given variable, the value at compile time may be different from
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the value at run-time unless you only assign constant
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values.</para>
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<para>For example, if you have:</para>
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<programlisting>EXT_IP=$(fiind_first_interface_address eth0)</programlisting>
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<para>in <filename>/etc/shorewall/params</filename> then all
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occurrences of $EXT_IP in Shorewall configuration files will be
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replaced with eth0's IP address when the program is being
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compiled. On the other hand, if you use $EXT_IP in your
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/etc/shorewall/start script, the value will be the IP address of
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eth0 when the program is run.</para>
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<para>Bottom line: You probably want to use only constant values
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for variables set in
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<filename>/etc/shorewall/params</filename>.</para>
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</listitem>
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</itemizedlist>
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</listitem>
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<listitem>
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<para>You must install Shorewall Lite on the system where you want
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to run the script. You then install the compiled program in
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/usr/share/shorewall/firewall and use the /sbin/shorewall program
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included with Shorewall Lite to control the firewall just as if the
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full Shorewall distribution was installed.</para>
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</listitem>
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</orderedlist>
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</section>
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</section>
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<section>
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<title>The "shorewall compile" command</title>
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<para>A compiled script is produced using the <command>compile</command>
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command:</para>
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<blockquote>
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<para><command>shorewall compile [ -e ] [ <directory name> ]
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<path name></command></para>
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</blockquote>
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<para>where</para>
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<blockquote>
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<variablelist>
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<varlistentry>
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<term>-e</term>
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<listitem>
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<para>Indicates that the program is to be "exported" to another
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system. When this flag is set, the "detectnets" interface is not
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allowed but the created program may be run on a system that has
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only Shorewall Lite installed</para>
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<para>When this flag is given, Shorewall does not probe the
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current system to determine the kernel/iptables features that it
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supports. It rather reads those capabilities from
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<filename>/etc/shorewall/capabilities</filename>. See below for
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details.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><directory name></term>
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<listitem>
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<para>specifies a directory to be searched for configuration files
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before those directories listed in the CONFIG_PATH variable in
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<filename>shorewall.conf</filename>.</para>
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<para>When -e <directory-name> is included, only the
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SHOREWALL_SHELL and VERBOSITY settings from
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<filename>/etc/shorewall/shorewall.conf</filename> are used and
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these apply only to the compiler itself. The settings used by the
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compiled firewall script are determined by the contents of
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<filename><directory name>/shorewall.conf</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><path name></term>
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<listitem>
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<para>specifies the name of the script to be created.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</blockquote>
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</section>
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<section id="Lite">
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<title>Shorewall Lite (Added in version 3.2.0 RC 1)</title>
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<para>Shorewall Lite is a companion product to Shorewall and is designed
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to allow you to maintain all Shorewall configuration information on a
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single system within your network.</para>
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<orderedlist numeration="loweralpha">
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<listitem>
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<para>You install the full Shorewall release on one system within your
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network. You need not configure Shorewall there and you may totally
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disable startup of Shorewall in your init scripts. For ease of
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reference, we call this system the 'administrative system'.</para>
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</listitem>
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<listitem>
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<para>On each system where you wish to run a Shorewall-generated
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firewall, you install Shorewall Lite. For ease of reference, we will
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call these systems the 'firewall systems'.</para>
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<note>
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<para>The firewall systems do <emphasis role="bold">NOT</emphasis>
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need to have the full Shorewall product installed but rather only
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the Shorewall Lite product. Shorewall and Shorewall LIte may be
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installed on the same system but that isn't encouraged.</para>
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</note>
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</listitem>
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<listitem>
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<para>On the administrative system you create a separete
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'configuration directory' for each firewall system. You copy the
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contents of /usr/share/shorewall/configfiles into each configuration
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directory.</para>
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</listitem>
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<listitem>
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<para>On each firewall system, you run:</para>
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<programlisting><command>/usr/share/shorewall-lite/shorecap > capabilities</command>
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<command>scp capabilities <admin system>:<this system's config dir></command></programlisting>
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</listitem>
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<listitem>
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<para>On the administrative system, for each firewall system you do
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the following (this may be done by a non-root user):</para>
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<orderedlist>
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<listitem>
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<para>modify the files in the corresponding configuration
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directory appropriately. It's a good idea to include the IP
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address of the administrative system in the
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<filename>routestopped</filename> file.</para>
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<para>It is important to understand that with Shorewall Lite, the
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firewall's configuration directory on the administrative system
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acts as <filename class="directory">/etc/shorewall</filename> for
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that firewall. So when the Shorewall documentation gives
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instructions for placing entries in files in the firewall's
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<filename class="directory">/etc/shorewall</filename>, when using
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Shorewall Lite you make those changes in the firewall's
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configuration directory on the administrative system.</para>
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</listitem>
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<listitem>
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<programlisting><command>cd <configuration directory></command>
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<command>/sbin/shorewall compile -e . firewall</command>
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<command>scp firewall root@<firewall system>:/var/lib/shorewall-lite/</command></programlisting>
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<note>
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<para>The 'firewall' script is in <filename
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class="directory">/var/lib/shorewall-lite</filename> in packages
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from shorewall.net. The package maintainers for the various
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distributions are free to choose the directory where the script
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will be stored under their distribution. You can look in your
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/usr/share/shorewall/configpath file to see what your
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distribution defines for the value of LITEDIR.</para>
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</note>
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</listitem>
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</orderedlist>
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</listitem>
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<listitem>
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<para>On each firewall system:</para>
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<para>Modify <filename>/etc/shorewall-lite/shorewall.conf</filename>
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as needed.</para>
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<para>If you are running Debian or one of its derivatives like Ubuntu
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then edit /etc/default/shorewall-lite and set startup=1.</para>
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<programlisting><command>shorewall-lite start</command></programlisting>
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</listitem>
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</orderedlist>
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<para>Shorewall Lite includes a very limited version of
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<filename>shorewall.conf
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</filename>(<filename>/etc/shorewall-lite/shorewall.conf</filename>). It
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includes the following options which have the same meaning as in a full
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Shorewall installation except as noted below:</para>
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<blockquote>
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<simplelist>
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<member>VERBOSITY</member>
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<member>LOGFILE</member>
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<member>LOGFORMAT — used by <filename>/sbin/shorewall</filename> for
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finding 'Shorewall' log messages. If LOGFORMAT was specified in the
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shorewall.conf file used at compile time on the administrative system,
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then the format of the messages themselves is defined by that value.
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If LOGFORMAT was not specified at compile time then the firewall
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script will use the value from
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<filename>/etc/shorewall-lite/shorewall.conf</filename> on the
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firewall system.</member>
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<member>IPTABLES — determines the iptables binary to be used by
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<filename>/sbin/shorewall</filename>. The compiled firewall script
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will use the IPTABLES specified in <filename>shorewall.conf</filename>
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at compile time on the administrative system, if any; if IPTABLES was
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not specified at compile time then the IPTABLES value from
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<filename>/etc/shorewall-lite/shorewall.conf</filename> on the
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firewall system will be used by the firewall script.</member>
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<member>PATH</member>
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<member>SHOREWALL_SHELL</member>
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<member>SUBSYSLOCK</member>
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<member>RESTOREFILE</member>
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</simplelist>
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</blockquote>
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<para>The <filename>/sbin/shorewall-lite</filename> program included with
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Shorewall Lite supports the same set of commands as the
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<filename>/sbin/shorewall</filename> program in a full Shorewall
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installation with the following exceptions:</para>
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<blockquote>
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<simplelist>
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<member>add</member>
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<member>compile</member>
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<member>delete</member>
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<member>refresh</member>
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<member>reload</member>
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<member>try</member>
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<member>safe-start</member>
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<member>safe-restart</member>
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<member>show actions</member>
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<member>show macros</member>
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</simplelist>
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</blockquote>
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<para>On systems with only Shorewall Lite installed, I recommend that you
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create a symbolic link <filename>/sbin/shorewall</filename> and point it
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at <filename>/sbin/shorewall-lite</filename>. That way, you can use
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<command>shorewall</command> as the command regardless of which product is
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installed.</para>
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<blockquote>
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<programlisting><command>ln -sf shorewall-lite /sbin/shorewall</command></programlisting>
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</blockquote>
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<section>
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<title>Converting a system from Shorewall to Shorewall Lite</title>
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<para>Converting a firewall system that is currently running Shorewall
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to run Shorewall Lite instead is straight-forward.</para>
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<orderedlist>
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<listitem>
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<para>On the administrative system, create a configuration directory
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for the firewall system.</para>
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</listitem>
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<listitem>
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<para>Copy the contents of <filename
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class="directory">/etc/shorewall/</filename> from the firewall
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system to the configuration directory on the administrative
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system.</para>
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</listitem>
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<listitem>
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<para>On the firewall system:</para>
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<para>Be sure that the IP address of the administrative system is
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included in <filename>/etc/shorewall/routestopped</filename>.</para>
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<programlisting><command>shorewall stop</command></programlisting>
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<para><emphasis role="bold">We recommend that you uninstall
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Shorewall at this point.</emphasis></para>
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</listitem>
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<listitem>
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<para>Install Shorewall Lite on the firewall system.</para>
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</listitem>
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<listitem>
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<para>On the firewall system:</para>
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<programlisting><command>/usr/share/shorewall-lite/shorecap > capabilities</command>
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<command>scp capabilities <admin system>:<this system's config dir></command></programlisting>
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</listitem>
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<listitem>
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<para>On the administrative system:</para>
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<para>It's a good idea to include the IP address of the
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administrative system in the firewall system's
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<filename>routestopped</filename> file.</para>
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<programlisting><command>cd <configuration directory></command>
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<command>/sbin/shorewall compile -e . firewall</command>
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<command>scp firewall root@<firewall system>:/var/lib/shorewall-lite/</command></programlisting>
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</listitem>
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<listitem>
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<para>On the firewall system:</para>
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<para>Modify <filename>/etc/shorewall-lite/shorewall.conf</filename>
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as needed.</para>
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<para>If you are running Debian or one of its derivatives like
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Ubuntu then edit /etc/default/shorewall-lite and set
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startup=1.</para>
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<programlisting><command>shorewall-lite start</command></programlisting>
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</listitem>
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</orderedlist>
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</section>
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<section>
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<title>/sbin/shorewall reload command (Added in 3.2.0 RC4)</title>
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<para>The <ulink
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url="starting_and_stopping_shorewall.htm#Reload"><command>reload</command>
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command</ulink> allows for easy updating of remote firewall systems by a
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non-root user. At shorewall.net, I keep my firewall configurations in
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sub-directories under ~/Configs. The name of the directory corresponds
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to the DNS name of the system.</para>
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<para>To recompile the firewall script for the system named gateway and
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to install that script on gateway, I issue the following
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commands:</para>
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<blockquote>
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<programlisting>teastep@wookie:~$ <command>cd Configs/gateway</command>
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teastep@wookie:~/Configs/gateway$ <command>/sbin/shorewall reload gateway</command>
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Compiling...
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Shorewall configuration compiled to firewall
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firewall 100% 29KB 29.3KB/s 00:00
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Restarting Shorewall Lite....
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done.
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teastep@wookie:~/Configs/gateway$</programlisting>
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</blockquote>
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<para>The user running the <command>reload</command> command must have
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ssh access to the remote system. I use RSA keys and ssh-agent so I don't
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need to enter a password each time the command runs scp or ssh; I only
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need to supply the password once when I log onto my desktop
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system.</para>
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</section>
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</section>
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<section>
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<title>The /etc/shorewall/capabilities file and the shorecap
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program</title>
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<para>As mentioned above, the /etc/shorewall/capabilities file specifies
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that kernel/iptables capabilities of the target system. Here is a sample
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file:</para>
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<blockquote>
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<programlisting>NAT_ENABLED=Yes # NAT
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MANGLE_ENABLED=Yes # Packet Mangling
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MULTIPORT=Yes # Multi-port Match
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XMULTIPORT=Yes # Extended Multi-port Match
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CONNTRACK_MATCH=Yes # Connection Tracking Match
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USEPKTTYPE= # Packet Type Match
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POLICY_MATCH=Yes # Policy Match
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PHYSDEV_MATCH=Yes # Physdev Match
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LENGTH_MATCH=Yes # Packet Length Match
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IPRANGE_MATCH=Yes # IP range Match
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RECENT_MATCH=Yes # Recent Match
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OWNER_MATCH=Yes # Owner match
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IPSET_MATCH= # Ipset Match
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CONNMARK=Yes # CONNMARK Target
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XCONNMARK=Yes # Extended CONNMARK Target
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CONNMARK_MATCH=Yes # Connmark Match
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XCONNMARK_MATCH=Yes # Extended Connmark Match
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RAW_TABLE=Yes # Raw Table
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IPP2P_MATCH= # IPP2P Match
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CLASSIFY_TARGET=Yes # CLASSIFY Target
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ENHANCED_REJECT=Yes # Extended REJECT
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KLUDGEFREE= # iptables accepts multiple "-m iprange" or "-m physdev" in a single command
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MARK=Yes # MARK Target Support
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XMARK=YES # Extended MARK Target Support
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MANGLE_FORWARD # Mangle table has FORWARD chain</programlisting>
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</blockquote>
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<para>As you can see, the file contains a simple list of shell variable
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assignments -- the variables correspond to the capabilities listed by the
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<command>shorewall show capabilities</command> command and they appear in
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the same order as the output of that command.</para>
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|
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<para>To aid in creating this file, Shorewall Lite includes a
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<command>shorecap</command> program. The program is installed in the
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<filename>/usr/share/shorewall-lite/</filename> directory and may be run
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as follows:</para>
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|
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<blockquote>
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<para><command>[ IPTABLES=<iptables binary> ] [
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MODULESDIR=<kernel modules directory> ]
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/usr/share/shorewall-lite/shorecap > capabilities</command></para>
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</blockquote>
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<para>The IPTABLES and MODULESDIR options have their <ulink
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url="Documentation.htm#Conf">usual Shorewall default
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values</ulink>.</para>
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<para>The <filename>capabilities</filename> file may then be copied to a
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system with Shorewall installed and used when compiling firewall programs
|
|
to run on the remote system.</para>
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</section>
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|
|
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<section>
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<title>Running compiled programs directly</title>
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|
|
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<para>Compiled firewall programs are complete programs that support the
|
|
following run-line commands:</para>
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|
|
|
<blockquote>
|
|
<simplelist>
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|
<member><command><program> [ -q ] [ -v ] [ -n ]
|
|
start</command></member>
|
|
|
|
<member><command><program> [ -q ] [ -v ] [ -n ]
|
|
stop</command></member>
|
|
|
|
<member><command><program> [ -q ] [ -v ] [ -n ]
|
|
clear</command></member>
|
|
|
|
<member><command><program> [ -q ] [ -v ] [ -n ]
|
|
restart</command></member>
|
|
|
|
<member><command><program> [ -q ] [ -v ] [ -n ]
|
|
status</command></member>
|
|
|
|
<member><command><program> [ -q ] [ -v ] [ -n ]
|
|
version</command></member>
|
|
</simplelist>
|
|
</blockquote>
|
|
|
|
<para>The options have their same meaning is when they are passed to
|
|
<filename>/sbin/shorewall</filename> itself. The default VERBOSITY level
|
|
is the level specified in the shorewall.conf file used when then program
|
|
was compiled.</para>
|
|
</section>
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</article> |