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Shorewall-1.3.9a
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@271 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
This commit is contained in:
teastep
@ -1,320 +1,426 @@
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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||||
<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>
|
||||
|
||||
<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">
|
||||
<tr>
|
||||
<td width="100%">
|
||||
|
||||
<h1 align="center"><font color="#FFFFFF">Standalone Firewall</font></h1>
|
||||
|
||||
</td>
|
||||
</tr>
|
||||
<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 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>
|
||||
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>
|
||||
<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
|
||||
/sbin/ip
|
||||
[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/~hany/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">
|
||||
<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>
|
||||
</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
|
||||
|
||||
<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>
|
||||
|
||||
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">
|
||||
<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>
|
||||
</table>
|
||||
</blockquote>
|
||||
<pre> fw net ACCEPT
|
||||
net all DROP info
|
||||
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>
|
||||
<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.<2E> 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">
|
||||
<EFBFBD><EFBFBD><EFBFBD> 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>
|
||||
<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 "-".</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.</li>
|
||||
<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>
|
||||
<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
|
||||
172.16.0.0 - 172.31.255.255
|
||||
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.</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:</div>
|
||||
<div align="left">
|
||||
<blockquote>
|
||||
<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber4">
|
||||
<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>
|
||||
|
||||
<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<4F> 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>ACCEPT</td>
|
||||
<td>net</td>
|
||||
<td>fw</td>
|
||||
<td><i><protocol></i></td>
|
||||
<td><i><port></i></td>
|
||||
<td> </td>
|
||||
<td> </td>
|
||||
<td>net</td>
|
||||
<td>ACCEPT</td>
|
||||
<td><EFBFBD></td>
|
||||
<td><EFBFBD></td>
|
||||
</tr>
|
||||
</table>
|
||||
<tr>
|
||||
<td>net</td>
|
||||
<td>net</td>
|
||||
<td>DROP</td>
|
||||
<td>info</td>
|
||||
<td><EFBFBD></td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>all</td>
|
||||
<td>all</td>
|
||||
<td>REJECT</td>
|
||||
<td>info</td>
|
||||
<td><EFBFBD></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:</div>
|
||||
<div align="left">
|
||||
<blockquote>
|
||||
<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber5">
|
||||
<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>
|
||||
</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>.</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:</div>
|
||||
<div align="left">
|
||||
<blockquote>
|
||||
<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber4">
|
||||
<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>
|
||||
</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.</div>
|
||||
<div align="left">
|
||||
<h2 align="left">Starting and Stopping Your Firewall</h2>
|
||||
</div>
|
||||
<div align="left">
|
||||
<p align="left">The <a href="Install.htm">installation procedure </a>
|
||||
configures your system to start Shorewall at system boot.</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".</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>.</div>
|
||||
<p align="left"><font size="2">Last updated
|
||||
7/23/2002 - <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>
|
||||
|
||||
|
||||
<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"<22>
|
||||
<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">
|
||||
<EFBFBD><EFBFBD><EFBFBD> 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">
|
||||
<EFBFBD><EFBFBD><EFBFBD><EFBFBD> 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><EFBFBD></td>
|
||||
<td><EFBFBD></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><EFBFBD></td>
|
||||
<td><EFBFBD></td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>ACCEPT</td>
|
||||
<td>net</td>
|
||||
<td>fw</td>
|
||||
<td>tcp</td>
|
||||
<td>110</td>
|
||||
<td><EFBFBD></td>
|
||||
<td><EFBFBD></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><EFBFBD></td>
|
||||
<td><EFBFBD></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">
|
||||
<20><><EFBFBD> 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">
|
||||
<20><><EFBFBD> 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>
|
||||
</html>
|
||||
|
||||
Reference in New Issue
Block a user