mirror of
https://gitlab.com/shorewall/code.git
synced 2024-12-27 16:49:05 +01:00
3354d96ebb
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@319 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
320 lines
14 KiB
HTML
320 lines
14 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||
<html>
|
||
<head>
|
||
|
||
<meta http-equiv="Content-Language" content="en-us">
|
||
|
||
<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
|
||
|
||
<meta name="ProgId" content="FrontPage.Editor.Document">
|
||
|
||
<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>
|
||
|
||
</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>
|
||
|
||
<h2>Line Continuation</h2>
|
||
|
||
<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>
|
||
|
||
<h2>Complementing an Address or Subnet</h2>
|
||
|
||
<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". There must
|
||
be no white space following the "!".</p>
|
||
|
||
<h2>Comma-separated Lists</h2>
|
||
|
||
<p>Comma-separated lists are allowed in a number of contexts within the
|
||
configuration files. A comma separated list:</p>
|
||
|
||
<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>
|
||
|
||
</ul>
|
||
|
||
<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>>. For example,
|
||
if you want to forward the range of tcp ports 4000 through 4100 to local
|
||
host 192.168.1.3, the entry in /etc/shorewall/rules is:<br>
|
||
</p>
|
||
|
||
<pre> DNAT net loc:192.168.1.3 tcp 4000:4100<br></pre>
|
||
|
||
<h2>Using Shell Variables</h2>
|
||
|
||
<p>You may use the /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".<br>
|
||
</p>
|
||
<p><b>Note: </b>It is not necessary to use the special Shorewall notation
|
||
in the <a href="MAC_Validation.html">/etc/shorewall/maclist</a> file.<br>
|
||
</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 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>
|
||
|
||
<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>
|
||
|
||
|
||
|
||
|
||
<p><font size="2"> Updated 10/24/2002 - <a href="support.htm">Tom Eastep</a>
|
||
</font></p>
|
||
|
||
|
||
|
||
<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>
|
||
|
||
|
||
<br>
|
||
<br>
|
||
<br>
|
||
<br>
|
||
<br>
|
||
</body>
|
||
</html>
|