2002-09-29 23:42:38 +02:00
|
|
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
2002-08-13 22:45:21 +02:00
|
|
|
|
<html>
|
|
|
|
|
|
<head>
|
|
|
|
|
|
|
2002-09-29 23:42:38 +02:00
|
|
|
|
<meta http-equiv="Content-Language" content="en-us">
|
2002-08-13 22:45:21 +02:00
|
|
|
|
|
2002-09-29 23:42:38 +02:00
|
|
|
|
<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
|
2002-08-13 22:45:21 +02:00
|
|
|
|
|
2002-09-29 23:42:38 +02:00
|
|
|
|
<meta name="ProgId" content="FrontPage.Editor.Document">
|
2002-08-13 22:45:21 +02:00
|
|
|
|
|
2002-09-29 23:42:38 +02:00
|
|
|
|
<meta http-equiv="Content-Type"
|
|
|
|
|
|
content="text/html; charset=windows-1252">
|
|
|
|
|
|
<title>Configuration File Basics</title>
|
|
|
|
|
|
</head>
|
|
|
|
|
|
<body>
|
|
|
|
|
|
|
|
|
|
|
|
<table border="0" cellpadding="0" cellspacing="0"
|
|
|
|
|
|
style="border-collapse: collapse;" bordercolor="#111111" width="100%"
|
|
|
|
|
|
id="AutoNumber1" bgcolor="#400169" height="90">
|
|
|
|
|
|
<tbody>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td width="100%">
|
|
|
|
|
|
<h1 align="center"><font color="#ffffff">Configuration Files</font></h1>
|
|
|
|
|
|
</td>
|
|
|
|
|
|
</tr>
|
2002-08-13 22:45:21 +02:00
|
|
|
|
|
2002-09-29 23:42:38 +02:00
|
|
|
|
</tbody>
|
|
|
|
|
|
</table>
|
|
|
|
|
|
|
|
|
|
|
|
<p><b><font color="#ff0000">Warning: </font>If you copy or edit your
|
|
|
|
|
|
configuration files on a system running Microsoft Windows, you <u>must</u>
|
|
|
|
|
|
run them through <a
|
|
|
|
|
|
href="http://www.megaloman.com/%7Ehany/software/hd2u/"> dos2unix</a>
|
|
|
|
|
|
before you use them with Shorewall.</b></p>
|
|
|
|
|
|
|
|
|
|
|
|
<h2>Files</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p>Shorewall's configuration files are in the directory /etc/shorewall.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
|
<li>/etc/shorewall/shorewall.conf - used to set several firewall
|
|
|
|
|
|
parameters.</li>
|
|
|
|
|
|
<li>/etc/shorewall/params - use this file to set shell variables
|
|
|
|
|
|
that you will expand in other files.</li>
|
|
|
|
|
|
<li>/etc/shorewall/zones - partition the firewall's view of the
|
|
|
|
|
|
world into <i>zones.</i></li>
|
|
|
|
|
|
<li>/etc/shorewall/policy - establishes firewall high-level policy.</li>
|
|
|
|
|
|
<li>/etc/shorewall/interfaces - describes the interfaces on the
|
|
|
|
|
|
firewall system.</li>
|
|
|
|
|
|
<li>/etc/shorewall/hosts - allows defining zones in terms of individual
|
|
|
|
|
|
hosts and subnetworks.</li>
|
|
|
|
|
|
<li>/etc/shorewall/masq - directs the firewall where to use many-to-one
|
|
|
|
|
|
(dynamic) Network Address Translation (a.k.a. Masquerading) and Source
|
|
|
|
|
|
Network Address Translation (SNAT).</li>
|
|
|
|
|
|
<li>/etc/shorewall/modules - directs the firewall to load kernel
|
|
|
|
|
|
modules.</li>
|
|
|
|
|
|
<li>/etc/shorewall/rules - defines rules that are exceptions to
|
|
|
|
|
|
the overall policies established in /etc/shorewall/policy.</li>
|
|
|
|
|
|
<li>/etc/shorewall/nat - defines static NAT rules.</li>
|
|
|
|
|
|
<li>/etc/shorewall/proxyarp - defines use of Proxy ARP.</li>
|
|
|
|
|
|
<li>/etc/shorewall/routestopped (Shorewall 1.3.4 and later) - defines
|
|
|
|
|
|
hosts accessible when Shorewall is stopped.</li>
|
|
|
|
|
|
<li>/etc/shorewall/tcrules - defines marking of packets for later
|
|
|
|
|
|
use by traffic control/shaping or policy routing.</li>
|
|
|
|
|
|
<li>/etc/shorewall/tos - defines rules for setting the TOS field
|
|
|
|
|
|
in packet headers.</li>
|
|
|
|
|
|
<li>/etc/shorewall/tunnels - defines IPSEC, GRE and IPIP tunnels
|
|
|
|
|
|
with end-points on the firewall system.</li>
|
|
|
|
|
|
<li>/etc/shorewall/blacklist - lists blacklisted IP/subnet/MAC
|
|
|
|
|
|
addresses.</li>
|
|
|
|
|
|
|
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
|
|
<h2>Comments</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p>You may place comments in configuration files by making the first non-whitespace
|
|
|
|
|
|
character a pound sign ("#"). You may also place comments at the end
|
|
|
|
|
|
of any line, again by delimiting the comment from the rest of the line
|
|
|
|
|
|
with a pound sign.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<p>Examples:</p>
|
|
|
|
|
|
|
|
|
|
|
|
<pre># This is a comment</pre>
|
|
|
|
|
|
|
|
|
|
|
|
<pre>ACCEPT net fw tcp www #This is an end-of-line comment</pre>
|
|
|
|
|
|
|
2002-08-13 22:45:21 +02:00
|
|
|
|
<h2>Line Continuation</h2>
|
2002-09-29 23:42:38 +02:00
|
|
|
|
|
|
|
|
|
|
<p>You may continue lines in the configuration files using the usual backslash
|
|
|
|
|
|
("\") followed immediately by a new line character.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<p>Example:</p>
|
|
|
|
|
|
|
|
|
|
|
|
<pre>ACCEPT net fw tcp \<br>smtp,www,pop3,imap #Services running on the firewall</pre>
|
|
|
|
|
|
|
|
|
|
|
|
<h2><a name="dnsnames"></a>Using DNS Names</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p align="left"> </p>
|
|
|
|
|
|
|
|
|
|
|
|
<p align="left"><b>WARNING: I personally recommend strongly <u>against</u>
|
|
|
|
|
|
using DNS names in Shorewall configuration files. If you use DNS names and
|
|
|
|
|
|
you are called out of bed at 2:00AM because Shorewall won't start as a result
|
|
|
|
|
|
of DNS problems then don't say that you were not forewarned. <br>
|
|
|
|
|
|
</b></p>
|
|
|
|
|
|
|
|
|
|
|
|
<p align="left"><b><EFBFBD><EFBFBD><EFBFBD> -Tom<br>
|
|
|
|
|
|
</b></p>
|
|
|
|
|
|
|
|
|
|
|
|
<p align="left">Beginning with Shorwall 1.3.9, Host addresses in Shorewall
|
|
|
|
|
|
configuration files may be specified either as IP addresses or as DNS Names.<br>
|
|
|
|
|
|
<br>
|
|
|
|
|
|
DNS names in iptables rules aren't nearly as useful as they first appear.
|
|
|
|
|
|
When a DNS name appears in a rule, the iptables utility resolves the name
|
|
|
|
|
|
to one or more IP addresses and inserts those addresses into the rule. So
|
|
|
|
|
|
change in the DNS->IP address relationship that occur after the firewall
|
|
|
|
|
|
has started have absolutely no effect on the firewall's ruleset. </p>
|
|
|
|
|
|
|
|
|
|
|
|
<p align="left"> If your firewall rules include DNS names then:</p>
|
|
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
|
<li>If your /etc/resolv.conf is wrong then your firewall won't start.</li>
|
|
|
|
|
|
<li>If your /etc/nsswitch.conf is wrong then your firewall won't start.</li>
|
|
|
|
|
|
<li>If your Name Server(s) is(are) down then your firewall won't start.</li>
|
|
|
|
|
|
<li>If your startup scripts try to start your firewall before starting
|
|
|
|
|
|
your DNS server then your firewall won't start.<br>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>Factors totally outside your control (your ISP's router is down
|
|
|
|
|
|
for example), can prevent your firewall from starting.</li>
|
|
|
|
|
|
<li>You must bring up your network interfaces prior to starting your firewall.<br>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
|
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
|
|
<p align="left"> Each DNS name much be fully qualified and include a minumum
|
|
|
|
|
|
of two periods (although one may be trailing). This restriction is imposed
|
|
|
|
|
|
by Shorewall to insure backward compatibility with existing configuration
|
|
|
|
|
|
files.<br>
|
|
|
|
|
|
<br>
|
|
|
|
|
|
Examples of valid DNS names:<br>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
|
<li>mail.shorewall.net</li>
|
|
|
|
|
|
<li>shorewall.net.</li>
|
|
|
|
|
|
|
|
|
|
|
|
</ul>
|
|
|
|
|
|
Examples of invalid DNS names:<br>
|
|
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
|
<li>mail (not fully qualified)</li>
|
|
|
|
|
|
<li>shorewall.net (only one period)</li>
|
|
|
|
|
|
|
|
|
|
|
|
</ul>
|
|
|
|
|
|
DNS names may not be used as:<br>
|
|
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
|
<li>The server address in a DNAT rule (/etc/shorewall/rules file)</li>
|
|
|
|
|
|
<li>In the ADDRESS column of an entry in /etc/shorewall/masq.</li>
|
|
|
|
|
|
<li>In the /etc/shorewall/nat file.</li>
|
|
|
|
|
|
|
|
|
|
|
|
</ul>
|
|
|
|
|
|
These are iptables restrictions and are not simply imposed for your inconvenience
|
|
|
|
|
|
by Shorewall. <br>
|
|
|
|
|
|
<br>
|
|
|
|
|
|
|
2002-08-13 22:45:21 +02:00
|
|
|
|
<h2>Complementing an Address or Subnet</h2>
|
2002-09-29 23:42:38 +02:00
|
|
|
|
|
|
|
|
|
|
<p>Where specifying an IP address, a subnet or an interface, you can
|
|
|
|
|
|
precede the item with "!" to specify the complement of the item. For
|
|
|
|
|
|
example, !192.168.1.4 means "any host but 192.168.1.4".</p>
|
|
|
|
|
|
|
|
|
|
|
|
<h2>Comma-separated Lists</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p>Comma-separated lists are allowed in a number of contexts within the
|
2002-08-13 22:45:21 +02:00
|
|
|
|
configuration files. A comma separated list:</p>
|
2002-09-29 23:42:38 +02:00
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
|
<li>Must not have any embedded white space.<br>
|
|
|
|
|
|
Valid: routestopped,dhcp,norfc1918<br>
|
|
|
|
|
|
Invalid: routestopped,<2C><><EFBFBD><EFBFBD> dhcp,<2C><><EFBFBD><EFBFBD> norfc1818</li>
|
|
|
|
|
|
<li>If you use line continuation to break a comma-separated list,
|
|
|
|
|
|
the continuation line(s) must begin in column 1 (or there would be
|
|
|
|
|
|
embedded white space)</li>
|
|
|
|
|
|
<li>Entries in a comma-separated list may appear in any order.</li>
|
|
|
|
|
|
|
2002-08-13 22:45:21 +02:00
|
|
|
|
</ul>
|
2002-09-29 23:42:38 +02:00
|
|
|
|
|
|
|
|
|
|
<h2>Port Numbers/Service Names</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p>Unless otherwise specified, when giving a port number you can use
|
|
|
|
|
|
either an integer or a service name from /etc/services. </p>
|
|
|
|
|
|
|
|
|
|
|
|
<h2>Port Ranges</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p>If you need to specify a range of ports, the proper syntax is <<i>low
|
|
|
|
|
|
port number</i>>:<<i>high port number</i>>.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<h2>Using Shell Variables</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p>You may use the file /etc/shorewall/params file to set shell variables
|
|
|
|
|
|
that you can then use in some of the other configuration files.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<p>It is suggested that variable names begin with an upper case letter<font
|
|
|
|
|
|
size="1"> </font>to distinguish them from variables used internally
|
|
|
|
|
|
within the Shorewall programs</p>
|
|
|
|
|
|
|
|
|
|
|
|
<p>Example:</p>
|
|
|
|
|
|
|
|
|
|
|
|
<blockquote>
|
|
|
|
|
|
<pre>NET_IF=eth0<br>NET_BCAST=130.252.100.255<br>NET_OPTIONS=noping,norfc1918</pre>
|
|
|
|
|
|
</blockquote>
|
|
|
|
|
|
|
|
|
|
|
|
<p><br>
|
|
|
|
|
|
Example (/etc/shorewall/interfaces record):</p>
|
|
|
|
|
|
<font
|
|
|
|
|
|
face="Century Gothic, Arial, Helvetica">
|
|
|
|
|
|
<blockquote>
|
|
|
|
|
|
<pre><font face="Courier">net $NET_IF $NET_BCAST $NET_OPTIONS</font></pre>
|
|
|
|
|
|
</blockquote>
|
|
|
|
|
|
</font>
|
|
|
|
|
|
|
|
|
|
|
|
<p>The result will be the same as if the record had been written</p>
|
|
|
|
|
|
<font
|
|
|
|
|
|
face="Century Gothic, Arial, Helvetica">
|
|
|
|
|
|
<blockquote>
|
|
|
|
|
|
<pre>net eth0 130.252.100.255 noping,norfc1918</pre>
|
|
|
|
|
|
</blockquote>
|
|
|
|
|
|
</font>
|
|
|
|
|
|
|
|
|
|
|
|
<p>Variables may be used anywhere in the other configuration
|
|
|
|
|
|
files.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<h2>Using MAC Addresses</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p>Media Access Control (MAC) addresses can be used to specify packet
|
|
|
|
|
|
source in several of the configuration files. To use this feature,
|
|
|
|
|
|
your kernel must have MAC Address Match support (CONFIG_IP_NF_MATCH_MAC)
|
|
|
|
|
|
included.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<p>MAC addresses are 48 bits wide and each Ethernet Controller has a
|
|
|
|
|
|
unique MAC address.<br>
|
|
|
|
|
|
<br>
|
|
|
|
|
|
In GNU/Linux, MAC addresses are usually written as a series of 6
|
|
|
|
|
|
hex numbers separated by colons. Example:<br>
|
|
|
|
|
|
<br>
|
|
|
|
|
|
<20><><EFBFBD><EFBFBD> [root@gateway root]# ifconfig eth0<br>
|
|
|
|
|
|
<20><><EFBFBD><EFBFBD> eth0 Link encap:Ethernet HWaddr <b><u>02:00:08:E3:FA:55</u></b><br>
|
|
|
|
|
|
<20><><EFBFBD><EFBFBD> inet addr:206.124.146.176 Bcast:206.124.146.255 Mask:255.255.255.0<br>
|
|
|
|
|
|
<20><><EFBFBD><EFBFBD> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1<br>
|
|
|
|
|
|
<20><><EFBFBD><EFBFBD> RX packets:2398102 errors:0 dropped:0 overruns:0 frame:0<br>
|
|
|
|
|
|
<20><><EFBFBD><EFBFBD> TX packets:3044698 errors:0 dropped:0 overruns:0 carrier:0<br>
|
|
|
|
|
|
<20><><EFBFBD><EFBFBD> collisions:30394 txqueuelen:100<br>
|
|
|
|
|
|
<20><><EFBFBD><EFBFBD> RX bytes:419871805 (400.4 Mb) TX bytes:1659782221 (1582.8 Mb)<br>
|
|
|
|
|
|
<20><><EFBFBD><EFBFBD> Interrupt:11 Base address:0x1800<br>
|
|
|
|
|
|
<br>
|
|
|
|
|
|
Because Shorewall uses colons as a separator for address fields,
|
|
|
|
|
|
Shorewall requires MAC addresses to be written in another way. In
|
|
|
|
|
|
Shorewall, MAC addresses begin with a tilde ("~") and consist of 6
|
|
|
|
|
|
hex numbers separated by hyphens. In Shorewall, the MAC address in
|
|
|
|
|
|
the example above would be written "~02-00-08-E3-FA-55".</p>
|
|
|
|
|
|
|
|
|
|
|
|
<h2>Shorewall Configurations</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p> Shorewall allows you to have configuration directories other than /etc/shorewall.
|
|
|
|
|
|
The <a href="starting_and_stopping_shorewall.htm">shorewall start and restart</a>
|
|
|
|
|
|
commands allow you to specify an alternate configuration directory and
|
|
|
|
|
|
Shorewall will use the files in the alternate directory rather than the corresponding
|
2002-08-13 22:45:21 +02:00
|
|
|
|
files in /etc/shorewall. The alternate directory need not contain a complete
|
|
|
|
|
|
configuration; those files not in the alternate directory will be read from
|
|
|
|
|
|
/etc/shorewall.</p>
|
2002-09-29 23:42:38 +02:00
|
|
|
|
|
|
|
|
|
|
<p> This facility permits you to easily create a test or temporary configuration
|
|
|
|
|
|
by:</p>
|
|
|
|
|
|
|
|
|
|
|
|
<ol>
|
|
|
|
|
|
<li> copying the files that need modification from /etc/shorewall
|
|
|
|
|
|
to a separate directory;</li>
|
|
|
|
|
|
<li> modify those files in the separate directory; and</li>
|
|
|
|
|
|
<li> specifying the separate directory in a shorewall start or
|
|
|
|
|
|
shorewall restart command (e.g., <i><b>shorewall -c /etc/testconfig restart</b></i>
|
|
|
|
|
|
).</li>
|
|
|
|
|
|
|
|
|
|
|
|
</ol>
|
|
|
|
|
|
|
2002-08-13 22:45:21 +02:00
|
|
|
|
|
|
|
|
|
|
|
2002-09-29 23:42:38 +02:00
|
|
|
|
|
|
|
|
|
|
<p><font size="2"> Updated 9/24/2002 - <a href="support.htm">Tom Eastep</a>
|
|
|
|
|
|
</font></p>
|
2002-08-13 22:45:21 +02:00
|
|
|
|
|
|
|
|
|
|
|
2002-09-29 23:42:38 +02:00
|
|
|
|
|
|
|
|
|
|
<p><font face="Trebuchet MS"><a href="copyright.htm"><font size="2">Copyright</font>
|
|
|
|
|
|
<20> <font size="2">2001, 2002 Thomas M. Eastep.</font></a></font></p>
|
2002-08-13 22:45:21 +02:00
|
|
|
|
|
|
|
|
|
|
|
2002-09-29 23:42:38 +02:00
|
|
|
|
<br>
|
|
|
|
|
|
<br>
|
|
|
|
|
|
</body>
|
|
|
|
|
|
</html>
|
