mirror of
https://gitlab.com/shorewall/code.git
synced 2024-12-25 07:38:57 +01:00
be5a11b988
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@972 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
582 lines
20 KiB
XML
582 lines
20 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
|
<article id="Shorewall_and_Aliased_Interfaces">
|
|
<!--$Id$-->
|
|
|
|
<articleinfo>
|
|
<title>Shorewall and Aliased Interfaces</title>
|
|
|
|
<authorgroup>
|
|
<author>
|
|
<firstname>Tom</firstname>
|
|
|
|
<surname>Eastep</surname>
|
|
</author>
|
|
</authorgroup>
|
|
|
|
<pubdate>2003-11-13</pubdate>
|
|
|
|
<copyright>
|
|
<year>2001</year>
|
|
|
|
<year>2002</year>
|
|
|
|
<year>2003</year>
|
|
|
|
<holder>Thomas M. Eastep</holder>
|
|
</copyright>
|
|
|
|
<legalnotice>
|
|
<para>Permission is granted to copy, distribute and/or modify this
|
|
document under the terms of the GNU Free Documentation License, Version
|
|
1.2 or any later version published by the Free Software Foundation; with
|
|
no Invariant Sections, with no Front-Cover, and with no Back-Cover
|
|
Texts. A copy of the license is included in the section entitled
|
|
<quote><ulink url="GnuCopyright.htm">GNU Free Documentation License</ulink></quote>.</para>
|
|
</legalnotice>
|
|
</articleinfo>
|
|
|
|
<section>
|
|
<title>Background</title>
|
|
|
|
<para>The traditional net-tools contain a program called
|
|
<emphasis>ifconfig</emphasis> which is used to configure network devices.
|
|
ifconfig introduced the concept of <emphasis>aliased</emphasis> or
|
|
<emphasis>virtual</emphasis> interfaces. These virtual interfaces have
|
|
names of the form <emphasis>interface:integer</emphasis> (e.g., eth0:0)
|
|
and ifconfig treats them more or less like real interfaces.</para>
|
|
|
|
<example>
|
|
<title>ifconfig</title>
|
|
|
|
<programlisting>[root@gateway root]# ifconfig eth0:0
|
|
eth0:0 Link encap:Ethernet HWaddr 02:00:08:3:FA:55
|
|
inet addr:206.124.146.178 Bcast:206.124.146.255 Mask:255.255.255.0
|
|
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
|
|
Interrupt:11 Base address:0x2000
|
|
[root@gateway root]# </programlisting>
|
|
</example>
|
|
|
|
<para>The ifconfig utility is being gradually phased out in favor of the
|
|
ip utility which is part of the <emphasis>iproute</emphasis> package. The
|
|
ip utility does not use the concept of aliases or virtual interfaces but
|
|
rather treats additional addresses on an interface as objects in their own
|
|
right. The ip utility does provide for interaction with ifconfig in that
|
|
it allows addresses to be <emphasis>labeled</emphasis> where these labels
|
|
take the form of ipconfig virtual interfaces.</para>
|
|
|
|
<example>
|
|
<title>ip</title>
|
|
|
|
<programlisting>[root@gateway root]# ip addr show dev eth0
|
|
2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc htb qlen 100
|
|
link/ether 02:00:08:e3:fa:55 brd ff:ff:ff:ff:ff:ff
|
|
inet 206.124.146.176/24 brd 206.124.146.255 scope global eth0
|
|
inet 206.124.146.178/24 brd 206.124.146.255 scope global secondary eth0:0
|
|
[root@gateway root]# </programlisting>
|
|
|
|
<para><note><para>One <emphasis role="bold">cannot</emphasis> type
|
|
<quote>ip addr show dev eth0:0</quote> because <quote>eth0:0</quote> is
|
|
a label for a particular address rather than a device name.</para><programlisting>[root@gateway root]# ip addr show dev eth0:0
|
|
Device "eth0:0" does not exist.
|
|
[root@gateway root]#</programlisting></note></para>
|
|
</example>
|
|
|
|
<para>The iptables program doesn't support virtual interfaces in
|
|
either it's <quote>-i</quote> or <quote>-o</quote> command options; as
|
|
a consequence, Shorewall does not allow them to be used in the
|
|
/etc/shorewall/interfaces file or anywhere else except as described in the
|
|
discussion below.</para>
|
|
</section>
|
|
|
|
<section>
|
|
<title>Adding Addresses to Interfaces</title>
|
|
|
|
<para>Most distributions have a facility for adding additional addresses
|
|
to interfaces. If you have already used your distribution's capability
|
|
to add your required addresses, you can skip this section.</para>
|
|
|
|
<para>Shorewall provides facilities for automatically adding addresses to
|
|
interfaces as described in the following section. It is also easy to add
|
|
them yourself using the <emphasis role="bold">ip</emphasis> utility. The
|
|
above alias was added using:</para>
|
|
|
|
<programlisting>ip addr add 206.124.146.178/24 brd 206.124.146.255 dev eth0 label eth0:0</programlisting>
|
|
|
|
<para>You probably want to arrange to add these addresses when the device
|
|
is started rather than placing commands like the above in one of the
|
|
Shorewall extension scripts. For example, on RedHat systems, you can place
|
|
the commands in /sbin/ifup-local:</para>
|
|
|
|
<programlisting>#!/bin/sh
|
|
|
|
case $1 in
|
|
eth0)
|
|
/sbin/ip addr add 206.124.146.177 dev eth0 label eth0:0
|
|
;;
|
|
esac</programlisting>
|
|
|
|
<para>RedHat systems also allow adding such aliases from the network
|
|
administration GUI (which only works well if you have a graphical
|
|
environment on your firewall).</para>
|
|
</section>
|
|
|
|
<section>
|
|
<title>So how do I handle more than one address on an interface?</title>
|
|
|
|
<para>The answer depends on what you are trying to do with the interfaces.
|
|
In the sub-sections that follow, we'll take a look at common
|
|
scenarios.</para>
|
|
|
|
<section>
|
|
<title>Separate Rules</title>
|
|
|
|
<para>If you need to make a rule for traffic to/from the firewall itself
|
|
that only applies to a particular IP address, simply qualify the $FW
|
|
zone with the IP address.</para>
|
|
|
|
<example>
|
|
<title>allow SSH from net to eth0:0 above</title>
|
|
|
|
<para><table><title>/etc/shorewall/rules</title><tgroup cols="7"><thead><row><entry
|
|
align="center">ACTION</entry><entry align="center">SOURCE</entry><entry
|
|
align="center">DESTINATION</entry><entry align="center">PROTOCOL</entry><entry
|
|
align="center">PORT(S)</entry><entry align="center">SOURCE PORT(S)</entry><entry
|
|
align="center">ORIGINAL DESTINATION</entry></row></thead><tbody><row><entry>ACCEPT</entry><entry>net</entry><entry>$FW:206.124.146.178</entry><entry>tcp</entry><entry>22</entry><entry></entry><entry></entry></row></tbody></tgroup></table></para>
|
|
</example>
|
|
</section>
|
|
|
|
<section>
|
|
<title>DNAT</title>
|
|
|
|
<para>Suppose that I had set up eth0:0 as above and I wanted to port
|
|
forward from that virtual interface to a web server running in my local
|
|
zone at 192.168.1.3. That is accomplised by a single rule in the
|
|
/etc/shorewall/rules file:</para>
|
|
|
|
<table>
|
|
<title>/etc/shorewall/rules</title>
|
|
|
|
<tgroup cols="7">
|
|
<thead>
|
|
<row>
|
|
<entry align="center">ACTION</entry>
|
|
|
|
<entry align="center">SOURCE</entry>
|
|
|
|
<entry align="center">DESTINATION</entry>
|
|
|
|
<entry align="center">PROTOCOL</entry>
|
|
|
|
<entry align="center">PORT(S)</entry>
|
|
|
|
<entry align="center">SOURCE PORT(S)</entry>
|
|
|
|
<entry align="center">ORIGINAL DESTINATION</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>DNAT</entry>
|
|
|
|
<entry>net</entry>
|
|
|
|
<entry>loc:192.168.1.3</entry>
|
|
|
|
<entry>tcp</entry>
|
|
|
|
<entry>80</entry>
|
|
|
|
<entry>-</entry>
|
|
|
|
<entry>206.124.146.178</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</section>
|
|
|
|
<section>
|
|
<title>SNAT</title>
|
|
|
|
<para>If you wanted to use eth0:0 as the IP address for outbound
|
|
connections from your local zone (eth1), then in /etc/shorewall/masq:</para>
|
|
|
|
<table>
|
|
<title>/etc/shorewall/masq</title>
|
|
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry align="center">INTERFACE</entry>
|
|
|
|
<entry align="center">SUBNET</entry>
|
|
|
|
<entry align="center">ADDRESS</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>eth0</entry>
|
|
|
|
<entry>eth1</entry>
|
|
|
|
<entry>206.124.146.178</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>Shorewall can create the alias (additional address) for you if you
|
|
set ADD_SNAT_ALIASES=Yes in /etc/shorewall/shorewall.conf. Beginning
|
|
with Shorewall 1.3.14, Shorewall can actually create the <quote>label</quote>
|
|
(virtual interface) so that you can see the created address using
|
|
ifconfig. In addition to setting ADD_SNAT_ALIASES=Yes, you specify the
|
|
virtual interface name in the INTERFACE column as follows:</para>
|
|
|
|
<table>
|
|
<title>/etc/shorewall/masq</title>
|
|
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry align="center">INTERFACE</entry>
|
|
|
|
<entry align="center">SUBNET</entry>
|
|
|
|
<entry align="center">ADDRESS</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>eth0:0</entry>
|
|
|
|
<entry>eth1</entry>
|
|
|
|
<entry>206.124.146.178</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>Shorewall can also set up SNAT to round-robin over a range of IP
|
|
addresses. Do do that, you specify a range of IP addresses in the
|
|
ADDRESS column. If you specify a label in the INTERFACE column,
|
|
Shorewall will use that label for the first address of the range and
|
|
will increment the label by one for each subsequent label.</para>
|
|
|
|
<table>
|
|
<title>/etc/shorewall/masq</title>
|
|
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry align="center">INTERFACE</entry>
|
|
|
|
<entry align="center">SUBNET</entry>
|
|
|
|
<entry align="center">ADDRESS</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>eth0:0</entry>
|
|
|
|
<entry>eth1</entry>
|
|
|
|
<entry>206.124.146.178-206.124.146.180</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>The above would create three IP addresses:</para>
|
|
|
|
<programlisting>eth0:0 = 206.124.146.178
|
|
eth0:1 = 206.124.146.179
|
|
eth0:2 = 206.124.146.180</programlisting>
|
|
</section>
|
|
|
|
<section>
|
|
<title>One-to-one NAT</title>
|
|
|
|
<para>If you wanted to use one-to-one NAT to link eth0:0 with local
|
|
address 192.168.1.3, you would have the following in /etc/shorewall/nat:<table><title>/etc/shorewall/nat</title><tgroup
|
|
cols="5"><thead><row><entry align="center">EXTERNAL</entry><entry
|
|
align="center">INTERFACE</entry><entry align="center">INTERNAL</entry><entry
|
|
align="center">ALL INTERFACES</entry><entry align="center">LOCAL</entry></row></thead><tbody><row><entry>206.124.146.178</entry><entry>eth0</entry><entry>192.168.1.3</entry><entry>no</entry><entry>no</entry></row></tbody></tgroup></table></para>
|
|
|
|
<para>Shorewall can create the alias (additional address) for you if you
|
|
set ADD_IP_ALIASES=Yes in /etc/shorewall/shorewall.conf. Beginning with
|
|
Shorewall 1.3.14, Shorewall can actually create the <quote>label</quote>
|
|
(virtual interface) so that you can see the created address using
|
|
ifconfig. In addition to setting ADD_IP_ALIASES=Yes, you specify the
|
|
virtual interface name in the INTERFACE column as follows:</para>
|
|
|
|
<table>
|
|
<title>/etc/shorewall/nat</title>
|
|
|
|
<tgroup cols="5">
|
|
<thead>
|
|
<row>
|
|
<entry align="center">EXTERNAL</entry>
|
|
|
|
<entry align="center">INTERFACE</entry>
|
|
|
|
<entry align="center">INTERNAL</entry>
|
|
|
|
<entry align="center">ALL INTERFACES</entry>
|
|
|
|
<entry align="center">LOCAL</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>206.124.146.178</entry>
|
|
|
|
<entry>eth0:0</entry>
|
|
|
|
<entry>192.168.1.3</entry>
|
|
|
|
<entry>no</entry>
|
|
|
|
<entry>no</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>In either case, to create rules that pertain only to this NAT
|
|
pair, you simply qualify the local zone with the internal IP address.</para>
|
|
|
|
<example>
|
|
<title>You want to allow SSH from the net to 206.124.146.178 a.k.a.
|
|
192.168.1.3.</title>
|
|
|
|
<para><table><title>/etc/shorewall/rules</title><tgroup cols="7"><thead><row><entry
|
|
align="center">ACTION</entry><entry align="center">SOURCE</entry><entry
|
|
align="center">DESTINATION</entry><entry align="center">PROTOCOL</entry><entry
|
|
align="center">PORT(S)</entry><entry align="center">SOURCE PORT(S)</entry><entry
|
|
align="center">ORIGINAL DESTINATION</entry></row></thead><tbody><row><entry>ACCEPT</entry><entry>net</entry><entry>loc:192.168.1.3</entry><entry>tcp</entry><entry>22</entry><entry></entry><entry></entry></row></tbody></tgroup></table></para>
|
|
</example>
|
|
</section>
|
|
|
|
<section>
|
|
<title>MULTIPLE SUBNETS</title>
|
|
|
|
<para>Sometimes multiple IP addresses are used because there are
|
|
multiple subnetworks configured on a LAN segment. This technique does
|
|
not provide for any security between the subnetworks if the users of the
|
|
systems have administrative privileges because in that case, the users
|
|
can simply manipulate their system's routing table to bypass your
|
|
firewall/router. Nevertheless, there are cases where you simply want to
|
|
consider the LAN segment itself as a zone and allow your firewall/router
|
|
to route between the two subnetworks.</para>
|
|
|
|
<example>
|
|
<title>Local interface eth1 interfaces to 192.168.1.0/24 and
|
|
192.168.20.0/24. The primary IP address of eth1 is 192.168.1.254 and
|
|
eth1:0 is 192.168.20.254. You want to simply route all requests
|
|
between the two subnetworks.</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>If you are running Shorewall 1.4.1 or Later</term>
|
|
|
|
<listitem>
|
|
<para>In /etc/shorewall/interfaces:</para>
|
|
|
|
<table>
|
|
<title>/etc/shorewall/interfaces</title>
|
|
|
|
<tgroup cols="4">
|
|
<thead>
|
|
<row>
|
|
<entry align="center">ZONE</entry>
|
|
|
|
<entry align="center">INTERFACE</entry>
|
|
|
|
<entry align="center">BROADCAST</entry>
|
|
|
|
<entry align="center">OPTIONS</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>-</entry>
|
|
|
|
<entry>eth1</entry>
|
|
|
|
<entry>192.168.1.255,192.168.20.255</entry>
|
|
|
|
<entry></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>In /etc/shorewall/hosts:</para>
|
|
|
|
<table>
|
|
<title>/etc/shorewall/hosts</title>
|
|
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry align="center">ZONE</entry>
|
|
|
|
<entry align="center">HOSTS</entry>
|
|
|
|
<entry align="center">OPTIONS</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>loc</entry>
|
|
|
|
<entry>eth1:192.168.1.0/24</entry>
|
|
|
|
<entry></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>loc</entry>
|
|
|
|
<entry>eth1:192.168.20.0/24</entry>
|
|
|
|
<entry></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>You do NOT need any entry in /etc/shorewall/policy as
|
|
Shorewall 1.4.1 and later releases default to allowing
|
|
intra-zone traffic.</para>
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>If you are running Shorewall 1.4.0 or earlier</term>
|
|
|
|
<listitem>
|
|
<para>In /etc/shorewall/interfaces:</para>
|
|
|
|
<table>
|
|
<title>/etc/shorewall/interfaces</title>
|
|
|
|
<tgroup cols="4">
|
|
<thead>
|
|
<row>
|
|
<entry align="center">ZONE</entry>
|
|
|
|
<entry align="center">INTERFACE</entry>
|
|
|
|
<entry align="center">BROADCAST</entry>
|
|
|
|
<entry align="center">OPTIONS</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>-</entry>
|
|
|
|
<entry>eth1</entry>
|
|
|
|
<entry>192.168.1.255,192.168.20.255</entry>
|
|
|
|
<entry><xref linkend="multiple_subnets-ex1-n1" /></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note id="multiple_subnets-ex1-n1">
|
|
<para>If you are running Shorewall 1.3.10 or earlier then you
|
|
must specify the <emphasis role="bold">multi</emphasis>
|
|
option.</para>
|
|
</note>
|
|
|
|
<para>In /etc/shorewall/policy:</para>
|
|
|
|
<table>
|
|
<title>/etc/shorewall/policy</title>
|
|
|
|
<tgroup cols="5">
|
|
<thead>
|
|
<row>
|
|
<entry align="center">SOURCE</entry>
|
|
|
|
<entry align="center">DESTINATION</entry>
|
|
|
|
<entry align="center">POLICY</entry>
|
|
|
|
<entry align="center">LOG LEVEL</entry>
|
|
|
|
<entry align="center">BURST:LIMIT</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>loc</entry>
|
|
|
|
<entry>loc</entry>
|
|
|
|
<entry>ACCEPT</entry>
|
|
|
|
<entry></entry>
|
|
|
|
<entry></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</example>
|
|
|
|
<example>
|
|
<title>Local interface eth1 interfaces to 192.168.1.0/24 and
|
|
192.168.20.0/24. The primary IP address of eth1 is 192.168.1.254 and
|
|
eth1:0 is 192.168.20.254. You want to make these subnetworks into
|
|
separate zones and control the access between them (the users of the
|
|
systems do not have administrative privileges).</title>
|
|
|
|
<para>In /etc/shorewall/zones:<table><title>etc/shorewall/zones</title><tgroup
|
|
cols="3"><thead><row><entry align="center">ZONE</entry><entry
|
|
align="center">DISPLAY</entry><entry align="center">DESCRIPTION</entry></row></thead><tbody><row><entry>loc</entry><entry>Local</entry><entry>Local
|
|
Zone 1</entry></row><row><entry>loc2</entry><entry>Local2</entry><entry>Local
|
|
Zone 2</entry></row></tbody></tgroup></table></para>
|
|
|
|
<para>In /etc/shorewall/interfaces:<table><title>/etc/shorewall/interfaces</title><tgroup
|
|
cols="4"><thead><row><entry align="center">ZONE</entry><entry
|
|
align="center">INTERFACE</entry><entry align="center">BROADCAST</entry><entry
|
|
align="center">OPTIONS</entry></row></thead><tbody><row><entry>-</entry><entry>eth1</entry><entry>192.168.1.255,192.168.20.255</entry><entry><xref
|
|
linkend="multiple_subnets-ex2-n1" /></entry></row></tbody></tgroup></table><note
|
|
id="multiple_subnets-ex2-n1"><para>If you are running Shorewall 1.3.10
|
|
or earlier then you must specify the <emphasis role="bold">multi</emphasis>
|
|
option.</para></note></para>
|
|
|
|
<para>In /etc/shorewall/hosts:<table><title>/etc/shorewall/hosts</title><tgroup
|
|
cols="3"><thead><row><entry align="center">ZONE</entry><entry
|
|
align="center">HOSTS</entry><entry align="center">OPTIONS</entry></row></thead><tbody><row><entry>loc</entry><entry>eth1:192.168.1.0/24</entry><entry></entry></row><row><entry>loc2</entry><entry>eth1:192.168.20.0/24</entry><entry></entry></row></tbody></tgroup></table></para>
|
|
|
|
<para>In /etc/shorewall/rules, simply specify ACCEPT rules for the
|
|
traffic that you want to permit.</para>
|
|
</example>
|
|
</section>
|
|
</section>
|
|
</article> |