mirror of
https://gitlab.com/shorewall/code.git
synced 2024-12-23 22:58:52 +01:00
17eb5cd1bb
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@265 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
427 lines
14 KiB
HTML
427 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>Standalone Firewall</title>
|
||
</head>
|
||
<body>
|
||
|
||
<table border="0" cellpadding="0" cellspacing="0"
|
||
style="border-collapse: collapse;" bordercolor="#111111" width="100%"
|
||
id="AutoNumber6" bgcolor="#400169" height="90">
|
||
<tbody>
|
||
<tr>
|
||
<td width="100%">
|
||
<h1 align="center"><font color="#ffffff">Standalone Firewall</font></h1>
|
||
</td>
|
||
</tr>
|
||
|
||
</tbody>
|
||
</table>
|
||
|
||
<h2 align="center">Version 2.0.1</h2>
|
||
|
||
<p align="left">Setting up Shorewall on a standalone Linux system is very
|
||
easy if you understand the basics and follow the documentation.</p>
|
||
|
||
<p>This guide doesn't attempt to acquaint you with all of the features of
|
||
Shorewall. It rather focuses on what is required to configure Shorewall in
|
||
one of its most common configurations:</p>
|
||
|
||
<ul>
|
||
<li>Linux system</li>
|
||
<li>Single external IP address</li>
|
||
<li>Connection through Cable Modem, DSL, ISDN, Frame Relay, dial-up...</li>
|
||
|
||
</ul>
|
||
|
||
<p>This guide assumes that you have the iproute/iproute2 package installed
|
||
(on RedHat, the package is called <i>iproute</i>)<i>. </i>You can tell if
|
||
this package is installed by the presence of an <b>ip</b> program on your
|
||
firewall system. As root, you can use the 'which' command to check for this
|
||
program:</p>
|
||
|
||
<pre> [root@gateway root]# which ip<br> /sbin/ip<br> [root@gateway root]#</pre>
|
||
|
||
<p>I recommend that you read through the guide first to familiarize yourself
|
||
with what's involved then go back through it again making your configuration
|
||
changes. Points at which configuration changes are recommended are flagged
|
||
with <img border="0" src="images/BD21298_.gif" width="13" height="13">
|
||
.</p>
|
||
|
||
<p><img border="0" src="images/j0213519.gif" width="60" height="60">
|
||
If you edit your configuration files on a Windows system, you must
|
||
save them as Unix files if your editor supports that option or you must
|
||
run them through dos2unix before trying to use them. Similarly, if you copy
|
||
a configuration file from your Windows hard drive to a floppy disk, you
|
||
must run dos2unix against the copy before using it with Shorewall.</p>
|
||
|
||
<ul>
|
||
<li><a href="http://www.simtel.net/pub/pd/51438.html">Windows Version
|
||
of dos2unix</a></li>
|
||
<li><a href="http://www.megaloman.com/%7Ehany/software/hd2u/">Linux Version
|
||
of dos2unix</a></li>
|
||
|
||
</ul>
|
||
|
||
<h2 align="left">Shorewall Concepts</h2>
|
||
|
||
<p>The configuration files for Shorewall are contained in the directory
|
||
/etc/shorewall -- for simple setups, you only need to deal with a few of
|
||
these as described in this guide. After you have <a href="Install.htm">installed
|
||
Shorewall</a>, download the <a
|
||
href="/pub/shorewall/LATEST.samples/one-interface.tgz">one-interface sample</a>,
|
||
un-tar it (tar -zxvf one-interface.tgz) and and copy the files to /etc/shorewall
|
||
(they will replace files with the same names that were placed in /etc/shorewall
|
||
during Shorewall installation).</p>
|
||
|
||
<p>As each file is introduced, I suggest that you look through the actual
|
||
file on your system -- each file contains detailed configuration instructions
|
||
and default entries.</p>
|
||
|
||
<p>Shorewall views the network where it is running as being composed of a
|
||
set of <i>zones.</i> In the one-interface sample configuration, only one
|
||
zone is defined:</p>
|
||
|
||
<table border="0" style="border-collapse: collapse;" cellpadding="3"
|
||
cellspacing="0" id="AutoNumber2">
|
||
<tbody>
|
||
<tr>
|
||
<td><u><b>Name</b></u></td>
|
||
<td><u><b>Description</b></u></td>
|
||
</tr>
|
||
<tr>
|
||
<td><b>net</b></td>
|
||
<td><b>The Internet</b></td>
|
||
</tr>
|
||
|
||
</tbody>
|
||
</table>
|
||
|
||
<p>Shorewall zones are defined in <a href="Documentation.htm#Zones"> /etc/shorewall/zones</a>.</p>
|
||
|
||
<p>Shorewall also recognizes the firewall system as its own zone - by default,
|
||
the firewall itself is known as <b>fw</b>.</p>
|
||
|
||
<p>Rules about what traffic to allow and what traffic to deny are expressed
|
||
in terms of zones.</p>
|
||
|
||
<ul>
|
||
<li>You express your default policy for connections from one zone to
|
||
another zone in the<a href="Documentation.htm#Policy"> /etc/shorewall/policy
|
||
</a>file.</li>
|
||
<li>You define exceptions to those default policies in the <a
|
||
href="Documentation.htm#Rules">/etc/shorewall/rules </a>file.</li>
|
||
|
||
</ul>
|
||
|
||
<p>For each connection request entering the firewall, the request is first
|
||
checked against the /etc/shorewall/rules file. If no rule in that file matches
|
||
the connection request then the first policy in /etc/shorewall/policy that
|
||
matches the request is applied. If that policy is REJECT or DROP the request
|
||
is first checked against the rules in /etc/shorewall/common (the samples
|
||
provide that file for you).</p>
|
||
|
||
<p>The /etc/shorewall/policy file included with the one-interface sample has
|
||
the following policies:</p>
|
||
|
||
<blockquote>
|
||
<table border="1" cellpadding="2" style="border-collapse: collapse;"
|
||
id="AutoNumber3">
|
||
<tbody>
|
||
<tr>
|
||
<td><u><b>SOURCE ZONE</b></u></td>
|
||
<td><u><b>DESTINATION ZONE</b></u></td>
|
||
<td><u><b>POLICY</b></u></td>
|
||
<td><u><b>LOG LEVEL</b></u></td>
|
||
<td><u><b>LIMIT:BURST</b></u></td>
|
||
</tr>
|
||
<tr>
|
||
<td>fw</td>
|
||
<td>net</td>
|
||
<td>ACCEPT</td>
|
||
<td> </td>
|
||
<td> </td>
|
||
</tr>
|
||
<tr>
|
||
<td>net</td>
|
||
<td>net</td>
|
||
<td>DROP</td>
|
||
<td>info</td>
|
||
<td> </td>
|
||
</tr>
|
||
<tr>
|
||
<td>all</td>
|
||
<td>all</td>
|
||
<td>REJECT</td>
|
||
<td>info</td>
|
||
<td> </td>
|
||
</tr>
|
||
|
||
</tbody>
|
||
</table>
|
||
</blockquote>
|
||
|
||
<pre> fw net ACCEPT<br> net all DROP info<br> all all REJECT info</pre>
|
||
|
||
<p>The above policy will:</p>
|
||
|
||
<ol>
|
||
<li>allow all connection requests from the firewall to the internet</li>
|
||
<li>drop (ignore) all connection requests from the internet to your firewall</li>
|
||
<li>reject all other connection requests (Shorewall requires this catchall
|
||
policy).</li>
|
||
|
||
</ol>
|
||
|
||
<p>At this point, edit your /etc/shorewall/policy and make any changes that
|
||
you wish.</p>
|
||
|
||
<h2 align="left">External Interface</h2>
|
||
|
||
<p align="left">The firewall has a single network interface. Where Internet
|
||
connectivity is through a cable or DSL "Modem", the <i>External Interface</i>
|
||
will be the ethernet adapter (<b>eth0</b>) that is connected to that "Modem"
|
||
<u>unless</u> you connect via <i><u>P</u>oint-to-<u>P</u>oint <u>P</u>rotocol
|
||
over <u>E</u>thernet</i> (PPPoE) or <i><u>P</u>oint-to-<u>P</u>oint <u>T</u>unneling
|
||
<u>P</u>rotocol </i>(PPTP) in which case the External Interface will be
|
||
a <b>ppp0</b>. If you connect via a regular modem, your External Interface
|
||
will also be <b>ppp0</b>. If you connect using ISDN, your external interface
|
||
will be<b> ippp0.</b></p>
|
||
|
||
<p align="left"><img border="0" src="images/BD21298_3.gif" width="13"
|
||
height="13">
|
||
The Shorewall one-interface sample configuration assumes that the external
|
||
interface is <b>eth0</b>. If your configuration is different, you will have
|
||
to modify the sample /etc/shorewall/interfaces file accordingly. While you
|
||
are there, you may wish to review the list of options that are specified
|
||
for the interface. Some hints:</p>
|
||
|
||
<ul>
|
||
<li>
|
||
<p align="left">If your external interface is <b>ppp0</b> or <b>ippp0</b>,
|
||
you can replace the "detect" in the second column with "-". </p>
|
||
</li>
|
||
<li>
|
||
<p align="left">If your external interface is <b>ppp0</b> or <b>ippp0</b>
|
||
or if you have a static IP address, you can remove "dhcp" from the option
|
||
list. </p>
|
||
</li>
|
||
|
||
</ul>
|
||
|
||
<div align="left">
|
||
<h2 align="left">IP Addresses</h2>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<p align="left">RFC 1918 reserves several <i>Private </i>IP address ranges
|
||
for use in private networks:</p>
|
||
|
||
<div align="left">
|
||
<pre> 10.0.0.0 - 10.255.255.255<br> 172.16.0.0 - 172.31.255.255<br> 192.168.0.0 - 192.168.255.255</pre>
|
||
</div>
|
||
|
||
<p align="left">These addresses are sometimes referred to as <i>non-routable</i>
|
||
because the Internet backbone routers will not forward a packet whose
|
||
destination address is reserved by RFC 1918. In some cases though, ISPs
|
||
are assigning these addresses then using <i>Network Address Translation
|
||
</i>to rewrite packet headers when forwarding to/from the internet.</p>
|
||
|
||
<p align="left"><img border="0" src="images/BD21298_.gif" align="left"
|
||
width="13" height="13">
|
||
Before starting Shorewall, you should look at the IP address of
|
||
your external interface and if it is one of the above ranges, you should
|
||
remove the 'norfc1918' option from the entry in /etc/shorewall/interfaces.</p>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<h2 align="left">Enabling other Connections</h2>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<p align="left">If you wish to enable connections from the internet to your
|
||
firewall, the general format is:</p>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<blockquote>
|
||
<table border="1" cellpadding="2" style="border-collapse: collapse;"
|
||
id="AutoNumber4">
|
||
<tbody>
|
||
<tr>
|
||
<td><u><b>ACTION</b></u></td>
|
||
<td><u><b>SOURCE</b></u></td>
|
||
<td><u><b>DESTINATION</b></u></td>
|
||
<td><u><b>PROTOCOL</b></u></td>
|
||
<td><u><b>PORT</b></u></td>
|
||
<td><u><b>SOURCE PORT</b></u></td>
|
||
<td><u><b>ORIGINAL ADDRESS</b></u></td>
|
||
</tr>
|
||
<tr>
|
||
<td>ACCEPT</td>
|
||
<td>net</td>
|
||
<td>fw</td>
|
||
<td><i><protocol></i></td>
|
||
<td><i><port></i></td>
|
||
<td> </td>
|
||
<td> </td>
|
||
</tr>
|
||
|
||
</tbody>
|
||
</table>
|
||
</blockquote>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<p align="left">Example - You want to run a Web Server and a POP3 Server on
|
||
your firewall system:</p>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<blockquote>
|
||
<table border="1" cellpadding="2" style="border-collapse: collapse;"
|
||
id="AutoNumber5">
|
||
<tbody>
|
||
<tr>
|
||
<td><u><b>ACTION</b></u></td>
|
||
<td><u><b>SOURCE</b></u></td>
|
||
<td><u><b>DESTINATION</b></u></td>
|
||
<td><u><b>PROTOCOL</b></u></td>
|
||
<td><u><b>PORT</b></u></td>
|
||
<td><u><b>SOURCE PORT</b></u></td>
|
||
<td><u><b>ORIGINAL ADDRESS</b></u></td>
|
||
</tr>
|
||
<tr>
|
||
<td>ACCEPT</td>
|
||
<td>net</td>
|
||
<td>fw</td>
|
||
<td>tcp</td>
|
||
<td>80</td>
|
||
<td> </td>
|
||
<td> </td>
|
||
</tr>
|
||
<tr>
|
||
<td>ACCEPT</td>
|
||
<td>net</td>
|
||
<td>fw</td>
|
||
<td>tcp</td>
|
||
<td>110</td>
|
||
<td> </td>
|
||
<td> </td>
|
||
</tr>
|
||
|
||
</tbody>
|
||
</table>
|
||
</blockquote>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<p align="left">If you don't know what port and protocol a particular application
|
||
uses, see <a href="ports.htm">here</a>.</p>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<p align="left"><b>Important: </b>I don't recommend enabling telnet to/from
|
||
the internet because it uses clear text (even for login!). If you want
|
||
shell access to your firewall from the internet, use SSH:</p>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<blockquote>
|
||
<table border="1" cellpadding="2" style="border-collapse: collapse;"
|
||
id="AutoNumber4">
|
||
<tbody>
|
||
<tr>
|
||
<td><u><b>ACTION</b></u></td>
|
||
<td><u><b>SOURCE</b></u></td>
|
||
<td><u><b>DESTINATION</b></u></td>
|
||
<td><u><b>PROTOCOL</b></u></td>
|
||
<td><u><b>PORT</b></u></td>
|
||
<td><u><b>SOURCE PORT</b></u></td>
|
||
<td><u><b>ORIGINAL ADDRESS</b></u></td>
|
||
</tr>
|
||
<tr>
|
||
<td>ACCEPT</td>
|
||
<td>net</td>
|
||
<td>fw</td>
|
||
<td>tcp</td>
|
||
<td>22</td>
|
||
<td> </td>
|
||
<td> </td>
|
||
</tr>
|
||
|
||
</tbody>
|
||
</table>
|
||
</blockquote>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<pre> ACCEPT net fw tcp 22</pre>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<p align="left"><img border="0" src="images/BD21298_3.gif" width="13"
|
||
height="13">
|
||
At this point, edit /etc/shorewall/rules to add other connections
|
||
as desired.</p>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<h2 align="left">Starting and Stopping Your Firewall</h2>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<p align="left"> <img border="0" src="images/BD21298_2.gif"
|
||
width="13" height="13" alt="Arrow">
|
||
The <a href="Install.htm">installation procedure </a> configures
|
||
your system to start Shorewall at system boot but beginning with Shorewall
|
||
version 1.3.9 startup is disabled so that your system won't try to start
|
||
Shorewall before configuration is complete. Once you have completed configuration
|
||
of your firewall, you can enable Shorewall startup by removing the file /etc/shorewall/startup_disabled.<br>
|
||
</p>
|
||
|
||
<p align="left"><font color="#ff0000"><b>IMPORTANT</b>: Users of the .deb
|
||
package must edit /etc/default/shorewall and set 'startup=1'.</font><br>
|
||
</p>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<p align="left">The firewall is started using the "shorewall start" command
|
||
and stopped using "shorewall stop". When the firewall is stopped, routing
|
||
is enabled on those hosts that have an entry in <a
|
||
href="Documentation.htm#Routestopped">/etc/shorewall/routestopped</a>. A
|
||
running firewall may be restarted using the "shorewall restart" command.
|
||
If you want to totally remove any trace of Shorewall from your Netfilter
|
||
configuration, use "shorewall clear".</p>
|
||
</div>
|
||
|
||
<div align="left">
|
||
<p align="left"><b>WARNING: </b>If you are connected to your firewall from
|
||
the internet, do not issue a "shorewall stop" command unless you have added
|
||
an entry for the IP address that you are connected from to <a
|
||
href="Documentation.htm#Routestopped">/etc/shorewall/routestopped</a>.
|
||
Also, I don't recommend using "shorewall restart"; it is better to create
|
||
an <i><a href="Documentation.htm#Configs">alternate configuration</a></i>
|
||
and test it using the <a href="Documentation.htm#Starting">"shorewall try"
|
||
command</a>.</p>
|
||
</div>
|
||
|
||
<p align="left"><font size="2">Last updated 9/26/2002 - <a
|
||
href="support.htm">Tom Eastep</a></font></p>
|
||
|
||
<p align="left"><a href="copyright.htm"><font size="2">Copyright 2002 Thomas
|
||
M. Eastep</font></a></p>
|
||
<br>
|
||
<br>
|
||
</body>
|
||
</html>
|