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134 lines
7.2 KiB
HTML
134 lines
7.2 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<meta http-equiv="Content-Language" content="en-us">
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<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
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<meta name="ProgId" content="FrontPage.Editor.Document">
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<meta http-equiv="Content-Type"
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content="text/html; charset=windows-1252">
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<title>Shorewall Extension Scripts</title>
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</head>
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<body>
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<table border="0" cellpadding="0" cellspacing="0"
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style="border-collapse: collapse;" bordercolor="#111111" width="100%"
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id="AutoNumber1" bgcolor="#400169" height="90">
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<tbody>
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<tr>
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<td width="100%">
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<h1 align="center"><font color="#ffffff">Extension Scripts</font></h1>
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</td>
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</table>
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<p> Extension scripts are user-provided scripts that are invoked at various
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points during firewall start, restart, stop and clear. The scripts are
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placed in /etc/shorewall and are processed using the Bourne shell "source"
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mechanism. 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 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 before
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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 'newnotsyn'
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chain has been created but before any rules have been added 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 want
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to use from the above list, you can simply create the file yourself.</b></u></p>
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<p> You can also supply a script with the same name as any of the filter
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chains in the firewall and the script will be invoked after the /etc/shorewall/rules
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file has been processed but before the /etc/shorewall/policy file has been
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processed.</p>
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<p>The /etc/shorewall/common file receives special treatment. If this file
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is present, the rules that it defines will totally replace the default
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rules in the common chain. These default rules are contained in the
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file /etc/shorewall/common.def which may be used as a starting point
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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 occurs
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during 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 can
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add the superceding rule before the '.' command. Using this technique allows
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you to add new rules while still getting the benefit of the latest common.def
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file.</p>
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<p>Remember that /etc/shorewall/common defines rules that are only applied
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if the applicable policy is DROP or REJECT. These rules are NOT applied
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if the policy is ACCEPT or CONTINUE.</p>
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<p>If you set ALLOWRELATED=No in shorewall.conf, then most ICMP packets will
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be rejected by the firewall. It is recommended with this setting that you
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create the file /etc/shorewall/icmpdef and in it place the following commands:</p>
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<pre> run_iptables -A icmpdef -p ICMP --icmp-type echo-reply -j ACCEPT<br> run_iptables -A icmpdef -p ICMP --icmp-type source-quench -j ACCEPT<br> run_iptables -A icmpdef -p ICMP --icmp-type destination-unreachable -j ACCEPT<br> run_iptables -A icmpdef -p ICMP --icmp-type time-exceeded -j ACCEPT<br> run_iptables -A icmpdef -p ICMP --icmp-type parameter-problem -j ACCEPT<br></pre>
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<p align="left"><font size="2">Last updated 12/22/2002 - <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 Thomas
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M. Eastep</font></a></p>
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<br>
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</body>
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</html>
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