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2002-08-07 16:28:04 +02:00
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<title>Shorewall Extension Scripts</title>
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2002-08-07 16:28:04 +02:00
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2003-11-17 22:06:32 +01:00
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<h1 style="text-align: center;">Extension Scripts<br>
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</h1>
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<p>Extension scripts are user-provided scripts that are invoked at
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various points during firewall start, restart, stop and clear. The
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scripts are placed in /etc/shorewall and are processed using the Bourne
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shell "source" mechanism.<br>
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</p>
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<p><font color="#ff0000"><b>Caution: <br>
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</b></font></p>
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<ol>
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<li><font color="#ff0000"><b>Be sure that you actually need to use an
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extension script to do what you want. Shorewall has a wide range of
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features
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that cover most requirements.</b></font></li>
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<li><font color="#ff0000"><b>DO NOT SIMPLY COPY RULES THAT YOU FIND
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ON THE NET INTO AN EXTENSION SCRIPT AND EXPECT THEM TO WORK AND TO NOT
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BREAK SHOREWALL. TO USE SHOREWALL EXTENSION SCRIPTS YOU MUST KNOW WHAT
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YOU ARE
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DOING WITH RESPECT TO iptables/Netfilter</b></font></li>
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</ol>
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<p>The following scripts can be supplied:</p>
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<ul>
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<li>init -- invoked early in "shorewall start" and "shorewall restart"</li>
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<li>start -- invoked after the firewall has been started or restarted.</li>
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<li>stop -- invoked as a first step when the firewall is being
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stopped.</li>
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<li>stopped -- invoked after the firewall has been stopped.</li>
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<li>clear -- invoked after the firewall has been cleared.</li>
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<li>refresh -- invoked while the firewall is being refreshed but
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before the common and/or blacklst chains have been rebuilt.</li>
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<li>newnotsyn (added in version 1.3.6) -- invoked after the
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'newnotsyn' chain has been created but before any rules have been added
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to it.</li>
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</ul>
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<p><u><b>If your version of Shorewall doesn't have the file that you
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want to use from the above list, you can simply create the file
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yourself.</b></u></p>
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<p> You can also supply a script with the same name as any of the
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filter chains in the firewall and the script will be invoked after the
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/etc/shorewall/rules file has been processed but before the
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/etc/shorewall/policy file has been processed.</p>
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<p>The /etc/shorewall/common file receives special treatment. If this
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file is present, the rules that it defines will totally replace the
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default rules in the common chain. These default rules are contained in
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the file /etc/shorewall/common.def which may be used as a starting
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point for making your own customized file.</p>
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<p> Rather than running iptables directly, you should run it using the
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function run_iptables. Similarly, rather than running "ip" directly,
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you should use run_ip. These functions accept the same arguments as the
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underlying command but cause the firewall to be stopped if an error
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occurs during
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processing of the command.</p>
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<p> If you decide to create /etc/shorewall/common it is a good idea to
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use the following technique</p>
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<p> /etc/shorewall/common:</p>
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<blockquote>
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<pre>. /etc/shorewall/common.def<br><add your rules here></pre>
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</blockquote>
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<p>If you need to supercede a rule in the released common.def file, you
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can add the superceding rule before the '.' command. Using this
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technique allows you to add new rules while still getting the benefit
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of the latest common.def file.</p>
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<p>Remember that /etc/shorewall/common defines rules that are only
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applied if the applicable policy is DROP or REJECT. These rules are NOT
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applied if the policy is ACCEPT or CONTINUE<br>
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</p>
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<p> </p>
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<p align="left"><font size="2">Last updated 6/30/2003 - <a
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href="support.htm">Tom Eastep</a></font></p>
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<p align="left"><a href="copyright.htm"><font size="2">Copyright 2002,
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2003 Thomas M. Eastep</font></a></p>
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<br>
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<br>
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<br>
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<br>
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<br>
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2002-08-22 23:33:54 +02:00
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</body>
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2002-12-28 16:38:03 +01:00
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</html>
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