forked from extern/shorewall_code
c68ecd14e7
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@519 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
352 lines
14 KiB
HTML
352 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><a name="Files"></a>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>
|
||
<li>/etc/shorewall/init - commands that you wish to execute at the
|
||
beginning of a "shorewall start" or "shorewall restart".</li>
|
||
<li>/etc/shorewall/start - commands that you wish to execute at the
|
||
completion of a "shorewall start" or "shorewall restart"</li>
|
||
<li>/etc/shorewall/stop - commands that you wish to execute at the
|
||
beginning of a "shorewall stop".</li>
|
||
<li>/etc/shorewall/stopped - commands that you wish to execute at
|
||
the completion of a "shorewall stop".</li>
|
||
<li>/etc/shorewall/ecn - disable Explicit Congestion Notification (ECN
|
||
- RFC 3168) to remote hosts or networks.<br>
|
||
</li>
|
||
|
||
</ul>
|
||
|
||
<h2><a name="Comments"></a>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><a name="Continuation"></a>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 as either IP addresses or 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 changes 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. (note the trailing period).</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 restrictions are not imposed by Shorewall simply
|
||
for your inconvenience but are rather limitations of iptables.<br>
|
||
|
||
<h2><a name="Compliment"></a>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><a name="Lists"></a>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: routefilter,dhcp,norfc1918<br>
|
||
Invalid: routefilter,<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><a name="Ports"></a>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><a name="Ranges"></a>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>
|
||
If you omit the low port number, a value of zero is assumed; if you omit
|
||
the high port number, a value of 65535 is assumed.<br>
|
||
|
||
<h2><a name="Variables"></a>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=routefilter,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 routefilter,norfc1918</pre>
|
||
</blockquote>
|
||
</font>
|
||
|
||
|
||
<p>Variables may be used anywhere in the other configuration
|
||
files.</p>
|
||
|
||
<h2><a name="MAC"></a>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><a name="Levels"></a>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 2/24/2003 - <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, 2003 Thomas M. Eastep.</font></a></font><br>
|
||
</p>
|
||
<br>
|
||
<br>
|
||
<br>
|
||
<br>
|
||
<br>
|
||
<br>
|
||
</body>
|
||
</html>
|