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228 lines
9.8 KiB
HTML
228 lines
9.8 KiB
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<html>
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<head>
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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" content="text/html; charset=windows-1252">
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<title>Configuration File Basics</title>
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<meta name="Microsoft Theme" content="boldstri 011, default">
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</head>
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<body>
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<h1 align="center">Configuration Files</h1>
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<p><b><font color="#FF0000">Warning: </font>If you copy or edit your
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configuration files on a system running Microsoft Windows, you <u>must</u>
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run them through <a href="http://www.megaloman.com/~hany/software/hd2u/">
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dos2unix</a> before you use them with Shorewall.</b></p>
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<h2>Files</h2>
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<p>Shorewall's configuration files are in the directory /etc/shorewall.</p>
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<ul>
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<li>/etc/shorewall/shorewall.conf - used to set several firewall
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parameters.</li>
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<li>/etc/shorewall/params - use this file to set shell variables that you will
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expand in other files.</li>
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<li>/etc/shorewall/zones - partition the firewall's view of the world
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into <i>zones.</i></li>
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<li>/etc/shorewall/policy - establishes firewall high-level policy.</li>
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<li>/etc/shorewall/interfaces - describes the interfaces on the
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firewall system.</li>
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<li>/etc/shorewall/hosts - allows defining zones in terms of individual
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hosts and subnetworks.</li>
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<li>/etc/shorewall/masq - directs the firewall where to use many-to-one
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(dynamic) Network Address Translation (a.k.a. Masquerading) and Source
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Network Address Translation (SNAT).</li>
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<li>/etc/shorewall/modules - directs the firewall to load kernel modules.</li>
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<li>/etc/shorewall/rules - defines rules that are exceptions to the
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overall policies established in /etc/shorewall/policy.</li>
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<li>/etc/shorewall/nat - defines static NAT rules.</li>
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<li>/etc/shorewall/proxyarp - defines use of Proxy ARP.</li>
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<li>/etc/shorewall/routestopped (Shorewall 1.3.4 and later) - defines hosts
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accessible when Shorewall is stopped.</li>
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<li>/etc/shorewall/tcrules - defines marking of packets for later use by
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traffic control/shaping or policy routing.</li>
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<li>/etc/shorewall/tos - defines rules for setting the TOS field in packet
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headers.</li>
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<li>/etc/shorewall/tunnels - defines IPSEC, GRE and IPIP tunnels with end-points on
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the firewall system.</li>
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<li>/etc/shorewall/blacklist - lists blacklisted IP/subnet/MAC addresses.</li>
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</ul>
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<h2>Comments</h2>
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<p>You may place comments in configuration files by making the first non-whitespace
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character a pound sign ("#"). You may also place comments at the end of any line, again by
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delimiting the comment from the rest of the line with a pound sign.</p>
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<p>Examples:</p>
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<pre># This is a comment</pre><pre>ACCEPT net fw tcp www #This is an end-of-line comment</pre>
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<h2>Line Continuation</h2>
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<p>You may continue lines in the configuration files using the usual backslash ("\") followed
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immediately by a new line character.</p>
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<p>Example:</p>
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<pre>ACCEPT net fw tcp \
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smtp,www,pop3,imap #Services running on the firewall</pre>
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<h2>Complementing an Address or Subnet</h2>
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<p>Where specifying an IP address, a subnet or an interface, you can
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precede the item with "!" to specify the complement of the item. For
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example, !192.168.1.4 means "any host but 192.168.1.4".</p>
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<h2>Comma-separated Lists</h2>
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<p>Comma-separated lists are allowed in a number of contexts within the
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configuration files. A comma separated list:</p>
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<ul>
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<li>Must not have any embedded white space.<br>
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Valid: routestopped,dhcp,norfc1918<br>
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Invalid: routestopped, dhcp,
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norfc1818</li>
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<li>If you use line continuation to break a comma-separated list, the
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continuation line(s) must begin in column 1 (or there would be embedded
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white space)</li>
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<li>Entries in a comma-separated list may appear in any order.</li>
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</ul>
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<h2>Port Numbers/Service Names</h2>
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<p>Unless otherwise specified, when giving a port number you can use
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either an integer or a service name from /etc/services. </p>
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<h2>Port Ranges</h2>
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<p>If you need to specify a range of ports, the proper syntax is <<i>low
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port number</i>>:<<i>high port number</i>>.</p>
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<h2>Using Shell Variables</h2>
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<p>You may use the file /etc/shorewall/params
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file to set shell variables that you can then use in some of the other
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configuration files.</p>
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<p>It is suggested that variable names begin with an upper case letter<font size="1">
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</font>to distinguish them from variables used internally within the
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Shorewall programs</p>
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<p>Example:</p>
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<blockquote>
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<pre>NET_IF=eth0
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NET_BCAST=130.252.100.255
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NET_OPTIONS=noping,norfc1918</pre>
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</blockquote>
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<p><br>
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Example (/etc/shorewall/interfaces record):</p>
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<font face="Century Gothic, Arial, Helvetica">
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<blockquote>
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<pre><font face="Courier">net $NET_IF $NET_BCAST $NET_OPTIONS</font></pre>
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</blockquote>
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</font>
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<p>The result will be the same as if the record had been written</p>
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<font face="Century Gothic, Arial, Helvetica">
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<blockquote>
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<pre>net eth0 130.252.100.255 noping,norfc1918</pre>
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</blockquote>
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</font>
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<p>Variables may be used anywhere in the
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other configuration files.</p>
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<h2>Using MAC Addresses</h2>
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<p>Media Access Control (MAC)
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addresses can be used to specify packet source in several of the
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configuration files. To use this feature, your kernel must have MAC
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Address Match support (CONFIG_IP_NF_MATCH_MAC) included.</p>
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<p>MAC addresses are 48 bits wide and each Ethernet Controller has a
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unique MAC address.<br>
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<br>
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In GNU/Linux, MAC addresses are usually written as a series of 6 hex numbers
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separated by colons. Example:<br>
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<br>
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[root@gateway root]# ifconfig eth0<br>
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eth0 Link encap:Ethernet HWaddr <b><u>02:00:08:E3:FA:55</u></b><br>
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inet addr:206.124.146.176 Bcast:206.124.146.255
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Mask:255.255.255.0<br>
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UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1<br>
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RX packets:2398102 errors:0 dropped:0 overruns:0
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frame:0<br>
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TX packets:3044698 errors:0 dropped:0 overruns:0
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carrier:0<br>
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collisions:30394 txqueuelen:100<br>
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RX bytes:419871805 (400.4 Mb) TX bytes:1659782221
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(1582.8 Mb)<br>
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Interrupt:11 Base address:0x1800<br>
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<br>
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Because Shorewall uses colons as a separator for address fields, Shorewall requires
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MAC addresses to be written in another way. In Shorewall, MAC addresses
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begin with a tilde ("~") and consist of 6 hex numbers separated by
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hyphens. In Shorewall, the MAC address in the example above would be
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written "~02-00-08-E3-FA-55".</p>
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<h2>Shorewall Configurations</h2>
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<p>
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Shorewall allows you to have configuration
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directories other than /etc/shorewall. The <a href="#Starting">shorewall start
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and restart</a>
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commands allow you to specify an alternate configuration directory and
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Shorewall will use the files in the alternate directory rather than the corresponding
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files in /etc/shorewall. The alternate directory need not contain a complete
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configuration; those files not in the alternate directory will be read from
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/etc/shorewall.</p>
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<p>
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This facility permits you to easily create a test or temporary configuration
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by:</p>
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<ol>
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<li>
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copying the files that need modification from /etc/shorewall to a separate
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directory;</li>
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<li>
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modify those files in the separate directory; and</li>
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<li>
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specifying the separate directory in a shorewall start or shorewall
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restart command (e.g., <i><b>shorewall -c /etc/testconfig restart</b></i>
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).</li>
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</ol>
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<p><font size="2">
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Updated 8/6/2002 - <a href="support.htm">Tom
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Eastep</a>
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</font></p>
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<p><font face="Trebuchet MS"><a href="copyright.htm"><font size="2">Copyright</font>
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<20> <font size="2">2001, 2002 Thomas M. Eastep.</font></a></font></p>
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</body>
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</html>
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