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<?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>
<!--$Id$-->
<articleinfo>
<title>Strong Firewall in a Routed Xen Dom0</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
<copyright>
<year>2006</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>
<caution>
<para>This article applies to Shorewall 3.0 and later. If you are running
a version of Shorewall earlier than Shorewall 3.0.0 then please see the
documentation for that release.</para>
</caution>
<section>
<title>Before Xen</title>
<para>Prior to adopting <ulink url="Xen.html">Xen</ulink>, I had a home
office crowded with 5 systems, three monitors a scanner and a printer. The
systems were:</para>
<orderedlist>
<listitem>
<para>Firewall</para>
</listitem>
<listitem>
<para>Public Server in a DMZ (mail)</para>
</listitem>
<listitem>
<para>Private Server (wookie)</para>
</listitem>
<listitem>
<para>My personal Linux Desktop (ursa)</para>
</listitem>
<listitem>
<para>My work system (docked laptop running Windows XP).</para>
</listitem>
</orderedlist>
<para>The result was a very crowded and noisy room.</para>
</section>
<section>
<title>After Xen</title>
<para>Xen has allowed me to reduce the noise and clutter considerably. I
now have three systems with two monitors. I've also replaced the
individual printer and scanner with a Multifunction
FAX/Scanner/Printer.</para>
<para>The systems now include:</para>
<orderedlist>
<listitem>
<para>Combination Firewall/Public Server/Private Server/Wireless
Gateway using Xen (created by building out my Linux desktop
system).</para>
</listitem>
<listitem>
<para>My work system.</para>
</listitem>
<listitem>
<para>My Linux desktop (wookie, which is actually the old public
server box)</para>
</listitem>
</orderedlist>
<para>The Linux systems run either <trademark>SuSE </trademark>10.1 or
<trademark>Ubuntu</trademark> "Edgy Eft".</para>
<para>Here is a high-level diagram of our network.</para>
<graphic align="center" fileref="images/Xen5.png" />
<para>As shown in this diagram, the Xen system has three physical network
interfaces. These are:</para>
<itemizedlist>
<listitem>
<para><filename class="devicefile">eth0</filename> -- connected to our
DSL "Modem".</para>
</listitem>
<listitem>
<para><filename class="devicefile">eth1</filename> -- connected to the
switch in my office. That switch is cabled to a second switch in my
wife's office where my wife has her desktop and networked printer (I
sure wish that there had been wireless back when I strung that CAT-5
cable halfway across the house).</para>
</listitem>
<listitem>
<para><filename class="devicefile">eth2</filename> -- connected to a
Wireless Access Point (WAP) that interfaces to our wireless
network.</para>
</listitem>
</itemizedlist>
<para>There are Two Xen domains.</para>
<orderedlist>
<listitem>
<para>Dom0 (DNS name <emphasis
role="bold">gateway.shorewall.net</emphasis>) is used as our main
firewall and wireless gateway as well as a local file server. It hosts
<ulink url="Shorewall_Squid_Usage.html">Squid</ulink> running as a
transparent HTTP proxy and a DHCP server that manages IP address
assignment for both the LAN and the Wireless network.</para>
</listitem>
<listitem>
<para>The DomU (Domain name <emphasis role="bold">lists</emphasis>,
DNS name <emphasis role="bold">lists.shorewall.net</emphasis>) is used
as a public Web/FTP/Mail/DNS server.</para>
</listitem>
</orderedlist>
<para>Shorewall runs in Dom0.</para>
<caution>
<para>As the developer of Shorewall, I have enough experience to be very
comfortable with Linux networking and Shorewall/iptables. I arrived at
this configuration after a fair amount of trial and error
experimentation (see <ulink url="Xen.html">Xen and Shorewall</ulink> and
<ulink url="XenMyWay.html">Xen and the art of Consolidation</ulink>). If
you are a Linux networking novice, I recommend that you do not attempt a
configuration like this one for your first Shorewall installation. You
are very likely to frustrate both yourself and the Shorewall support
team. Rather I suggest that you start with something simple like a
<ulink url="standalone.htm">standalone installation</ulink> in a DomU;
once you are comfortable with that then you will be ready to try
something more substantial.</para>
<para>As Paul Gear says: <emphasis>Shorewall might make iptables easy,
but it doesn't make understanding fundamental networking principles,
traffic shaping, or multi-ISP routing any easier</emphasis>.</para>
<para>The same goes for Xen networking.</para>
</caution>
<section id="Domains">
<title>Domain Configuration</title>
<para>Below are the relevant configuration files for the two domains. I
use a partition on my hard drives for the DomU storage device.</para>
<para>There is not much documentation about how to configure Xen for
routed operation. I've tried to mark the relevant parts with <emphasis
role="bold">bold font</emphasis>.</para>
<blockquote>
<para><filename>/boot/grub/menu.lst</filename> — here is the entry
that boots Xen in Dom0.</para>
<blockquote>
<programlisting>title XEN
root (hd0,1)
kernel /boot/xen.gz Dom0_mem=458752 sched=bvt
module /boot/vmlinuz-xen root=/dev/hda2 vga=0x31a selinux=0 resume=/dev/hda1 splash=silent showopts
module /boot/initrd-xen</programlisting>
</blockquote>
<para><filename>/etc/modprobe.conf.local</filename> (This may need to
go in <filename>/etc/modprobe.conf</filename> or
<filename>/etc/modprobe.d/options</filename> on your system)</para>
<para><blockquote>
<programlisting><emphasis role="bold">options netloop nloopbacks=0</emphasis> #Stop netloop from creating 8 useless vifs</programlisting>
</blockquote></para>
<para><filename>/etc/xen/auto/01-lists</filename> — configuration file
for the lists domain. Placed in <filename
class="directory">/etc/xen/auto/</filename> so it is started
automatically by Xen's <emphasis>xendomains</emphasis> service.</para>
<blockquote>
<programlisting># -*- mode: python; -*-
# configuration name:
name = "lists"
# usable ram:
memory = 512
# kernel and initrd:
kernel = "/xen2/vmlinuz-xen"
ramdisk = "/xen2/initrd-xen"
# boot device:
root = "/dev/hda3"
# boot to run level:
extra = "3"
# network interface:
vif = [ 'mac=aa:cc:00:00:00:01, <emphasis role="bold">ip=206.124.146.177, vifname=eth3</emphasis>' ]
# storage devices:
disk = [ 'phy:hda3,hda3,w' ]</programlisting>
<para>Note that the vifname is set to 'eth3' for the virtual
interface to this DomU. This will cause the Dom0 interface to the
server to have a fixed name (<filename
class="devicefile">eth3</filename>) which makes it a lot easier to
deal with in Shorewall and elsewhere.</para>
<para>Specifying an IP address (ip=206.124.146.177) causes the
vif-route script to create a host route to that IP address on
<filename class="devicefile">eth3</filename>.</para>
<blockquote>
<programlisting>gateway:~ # <command>ip route ls dev eth3</command>
206.124.146.177 scope link src 206.124.146.176
gateway:~ #</programlisting>
</blockquote>
<para>Note that the source for the route is 206.124.146.176. That is
the primary IP address of Dom0's <filename
class="devicefile">eth0</filename>. Xen configures <filename
class="devicefile">eth3</filename> to have that same IP
address.</para>
</blockquote>
<para>Excerpt from
<filename>/etc/xen/xend-config.sxp</filename>:<blockquote>
<programlisting>…
# It is possible to use the network-bridge script in more complicated
# scenarios, such as having two outgoing interfaces, with two bridges, and
# two fake interfaces per guest domain. To do things like this, write
# yourself a wrapper script, and call network-bridge from it, as appropriate.
#
<emphasis role="bold">#</emphasis>(network-script network-bridge)
…
# If you are using only one bridge, the vif-bridge script will discover that,
# so there is no need to specify it explicitly.
#
<emphasis role="bold">#</emphasis>(vif-script vif-bridge)
## Use the following if network traffic is routed, as an alternative to the
# settings for bridged networking given above.
<emphasis role="bold">(network-script network-route)
(vif-script vif-route)</emphasis>
</programlisting>
<important>
<para>As of this writing, the vif-route script does not set up
Proxy ARP correctly. So the domU can communicate with the dom0
but not with hosts beyond the dom0.</para>
<para>If you configure Shorewall as described below, Shorewall
will correct the Proxy ARP configuration so that it will
work.</para>
</important>
</blockquote></para>
<note>
<para>I have been asked a couple of times "How would I add another
domU to the DMZ?" Here is a sample config file to add a second domU
named "server", boot device <filename>/dev/hdb1</filename> and IP
address 206.124.146.179:</para>
<programlisting># -*- mode: python; -*-
# configuration name:
name = "server"
# usable ram:
memory = 512
# kernel and initrd:
kernel = "/xen2/vmlinuz-xen"
ramdisk = "/xen2/initrd-xen"
# boot device:
root = "/dev/hdb1"
# boot to run level:
extra = "3"
# network interface:
vif = [ 'mac=aa:cc:00:00:00:02, <emphasis role="bold">ip=206.124.146.179, vifname=eth4</emphasis>' ]
# storage devices:
disk = [ 'phy:hdb1,hdb1,w' ]</programlisting>
<para>Note that this domU has its own vif named <filename
class="devicefile">eth4</filename>.</para>
<para>The Shorewall configuration would need to be adjusted
accordingly.</para>
</note>
</blockquote>
<para>With both Xen domains up and running, the system looks as shown in
the following diagram.</para>
<graphic align="center" fileref="images/Xen4a.png" />
<para>The zones correspond to the Shorewall zones in the Dom0
configuration.</para>
<caution>
<para>Under some circumstances, UDP and/or TCP communication from a
DomU won't work for no obvious reason. That happened with the
<emphasis role="bold">lists</emphasis> domain in my setup. Looking at
the IP traffic with <command>tcpdump -nvvi eth1</command> in Dom0
showed that UDP packets from the <emphasis
role="bold">lists</emphasis> DomU had incorrect checksums. That
problem was corrected by arranging for the following command to be
executed in the <emphasis role="bold">lists</emphasis> domain when its
<filename class="devicefile">eth0</filename> device was brought
up:</para>
<para><command>ethtool -K eth0 tx off</command></para>
<para>Under <trademark>SuSE</trademark> 10.1, I placed the following
in <filename>/etc/sysconfig/network/if-up.d/resettx</filename> (that
file is executable):</para>
<programlisting>#!/bin/sh
if [ $2 = eth0 ]; then
ethtool -K eth0 tx off
echo "TX Checksum reset on eth0"
fi</programlisting>
<para>Under other distributions, the technique will vary. For example,
under <trademark>Debian</trademark> or <trademark>Ubuntu</trademark>,
you can just add a 'post-up' entry to
<filename>/etc/network/interfaces</filename> as shown here:</para>
<programlisting> iface eth0 inet static
address 206.124.146.177
netmask 255.255.255.0
post-up ethtool -K eth0 tx off</programlisting>
</caution>
</section>
<section id="Firewall">
<title>Dom0 Shorewall Configuration</title>
<para>In Dom0, I run a conventional three-interface firewall with Proxy
ARP DMZ -- it is very similar to the firewall described in the <ulink
url="shorewall_setup_guide.htm">Shorewall Setup Guide</ulink> with the
exception that I've added a fourth interface for our wireless network.
The firewall runs a routed <ulink url="OPENVPN.html">OpenVPN
server</ulink> to provide roadwarrior access for our two laptops and a
bridged OpenVPN server for the wireless network in our home. Here is the
firewall's view of the network:</para>
<graphic align="center" fileref="images/network4a.png" />
<para>The two laptops can be directly attached to the LAN as shown above
or they can be attached wirelessly -- their IP addresses are the same in
either case; when they are directly attached, the IP address is assigned
by the DHCP server running in Dom0 and when they are attached
wirelessly, the IP address is assigned by OpenVPN.</para>
<para>The Shorewall configuration files are shown below. All routing and
secondary IP addresses are handled in the SuSE network
configuration.</para>
<blockquote>
<para>/etc/shorewall/shorewall.conf</para>
<programlisting>STARTUP_ENABLED=Yes
VERBOSITY=0
LOGFILE=/var/log/firewall
LOGFORMAT="FW:%s:%s:"
LOGTAGONLY=No
LOGRATE=
LOGBURST=
LOGALLNEW=
BLACKLIST_LOGLEVEL=
MACLIST_LOG_LEVEL=$LOG
TCP_FLAGS_LOG_LEVEL=$LOG
RFC1918_LOG_LEVEL=$LOG
SMURF_LOG_LEVEL=$LOG
LOG_MARTIANS=No
PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin:/usr/local/sbin
SHOREWALL_SHELL=/bin/ash
SUBSYSLOCK=/var/lock/subsys/shorewall-lite
MODULESDIR=
CONFIG_PATH=/usr/share/shorewall-lite:/usr/share/shorewall/configfiles:/usr/share/shorewall
RESTOREFILE=restore
IPSECFILE=zones
IP_FORWARDING=On
ADD_IP_ALIASES=No
ADD_SNAT_ALIASES=No
RETAIN_ALIASES=No
TC_ENABLED=Internal
TC_EXPERT=No
CLEAR_TC=Yes
MARK_IN_FORWARD_CHAIN=Yes
CLAMPMSS=Yes
ROUTE_FILTER=No
DETECT_DNAT_IPADDRS=Yes
MUTEX_TIMEOUT=60
ADMINISABSENTMINDED=Yes
BLACKLISTNEWONLY=Yes
DELAYBLACKLISTLOAD=Yes
MODULE_SUFFIX=
DISABLE_IPV6=Yes
BRIDGING=No
DYNAMIC_ZONES=No
PKTTYPE=No
RFC1918_STRICT=Yes
MACLIST_TTL=60
SAVE_IPSETS=No
MAPOLDACTIONS=No
FASTACCEPT=Yes
HIGH_ROUTE_MARKS=Yes
BLACKLIST_DISPOSITION=DROP
MACLIST_TABLE=mangle
MACLIST_DISPOSITION=DROP
TCP_FLAGS_DISPOSITION=DROP</programlisting>
<para><filename>/etc/shorewall/zones</filename>:</para>
<programlisting>#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS
fw firewall #The firewall itself.
net ipv4 #Internet
loc ipv4 #Local wired Zone
dmz ipv4 #DMZ
vpn ipv4 #Open VPN clients
wifi ipv4 #Local Wireless Zone
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
</programlisting>
<para><filename>/etc/shorewall/policy</filename>:</para>
<programlisting>#SOURCE DEST POLICY LOG LIMIT:BURST
# LEVEL
$FW $FW ACCEPT
$FW net ACCEPT
loc net ACCEPT
$FW vpn ACCEPT
vpn net ACCEPT
vpn loc ACCEPT
loc vpn ACCEPT
$FW loc ACCEPT
loc $FW ACCEPT
wifi all REJECT $LOG
net $FW DROP $LOG 1/sec:2
net loc DROP $LOG 2/sec:4
net dmz DROP $LOG 8/sec:30
net vpn DROP $LOG
all all REJECT $LOG
#LAST LINE -- DO NOT REMOVE</programlisting>
<para><filename>Note that the firewall&lt;-&gt;local network interface
is wide open so from a security point of view, the firewall system is
part of the local zone.</filename></para>
<para><filename>/etc/shorewall/params (edited)</filename>:</para>
<programlisting>MIRRORS=&lt;comma-separated list of Shorewall mirrors&gt;
NTPSERVERS=&lt;comma-separated list of NTP servers I sync with&gt;
POPSERVERS=&lt;comma-separated list of server IP addresses&gt;
LOG=info
INT_IF=br0
DMZ_IF=eth3
EXT_IF=eth0
WIFI_IF=eth2
OMAK=&lt;IP address at our second home&gt;
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/init</filename>:</para>
<programlisting>echo 1 &gt; /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_be_liberal</programlisting>
<para><filename>/etc/shorewall/interfaces</filename>:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net $EXT_IF 206.124.146.255 dhcp,norfc1918,logmartians,blacklist,tcpflags,nosmurfs
dmz $DMZ_IF 192.168.0.255 logmartians
loc $INT_IF 192.168.1.255 dhcp,routeback,logmartians
wifi $WIFI_IF 192.168.3.255 dhcp,maclist
vpn tun+ -
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/nat</filename>:</para>
<programlisting>#EXTERNAL INTERFACE INTERNAL ALL LOCAL
# INTERFACES
206.124.146.178 $EXT_IF 192.168.1.3 No No #Wookie
206.124.146.180 $EXT_IF 192.168.1.6 No No #Work LapTop
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/masq (Note the cute trick here and in
the <filename>following proxyarp</filename> file that allows me to
access the DSL "Modem" using it's default IP address
(192.168.1.1))</filename>. The leading "+" is required to place the
rule before the SNAT rules generated by entries in
<filename>/etc/shorewall/nat</filename> above.</para>
<programlisting>#INTERFACE SUBNET ADDRESS PROTO PORT(S) IPSEC
+$EXT_IF:192.168.1.1 0.0.0.0/0 192.168.1.254
$EXT_IF 192.168.0.0/22 206.124.146.179
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/proxyarp</filename>:</para>
<programlisting>#ADDRESS INTERFACE EXTERNAL HAVEROUTE PERSISTENT
192.168.1.1 $EXT_IF $INT_IF yes
206.124.146.177 $DMZ_IF $EXT_IF yes
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/tunnels</filename>:</para>
<programlisting>#TYPE ZONE GATEWAY GATEWAY
# ZONE
openvpnserver:udp net 0.0.0.0/0 #Routed server for RoadWarrior access
openvpnserver:udp wifi 192.168.3.0/24 #Home wireless network server
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/blacklist</filename>:</para>
<programlisting>#ADDRESS/SUBNET PROTOCOL PORT
- udp 1024:1033,1434
- tcp 57,1433,1434,2401,2745,3127,3306,3410,4899,5554,6101,8081,9898
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/actions</filename>:</para>
<programlisting>#ACTION
Mirrors # Accept traffic from Shorewall Mirrors
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/action.Mirrors</filename>:</para>
<programlisting>#TARGET SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE
# PORT PORT(S) DEST LIMIT
ACCEPT $MIRRORS
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/rules</filename>:</para>
<programlisting>SECTION NEW
###############################################################################################################################################################################
#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/
# PORT PORT(S) DEST LIMIT GROUP
###############################################################################################################################################################################
REJECT:$LOG loc net tcp 25
REJECT:$LOG loc net udp 1025:1031
#
# Stop NETBIOS crap
#
REJECT loc net tcp 137,445
REJECT loc net udp 137:139
#
# Stop my idiotic work laptop from sending to the net with an HP source/dest IP address
#
DROP loc:!192.168.0.0/22 net
###############################################################################################################################################################################
# Local Network to Firewall
#
REDIRECT- loc 3128 tcp 80 - !192.168.1.1,192.168.0.7,206.124.146.177,155.98.64.80
###############################################################################################################################################################################
# Road Warriors to Firewall
#
ACCEPT vpn fw tcp ssh,time,631,8080
ACCEPT vpn fw udp 161,ntp,631
Ping/ACCEPT vpn fw
###############################################################################################################################################################################
# Road Warriors to DMZ
#
ACCEPT vpn dmz udp domain
ACCEPT vpn dmz tcp www,smtp,smtps,domain,ssh,imap,https,imaps,ftp,10023,pop3 -
Ping/ACCEPT vpn dmz
###############################################################################################################################################################################
# Local network to DMZ
#
ACCEPT loc dmz udp domain
ACCEPT loc dmz tcp ssh,smtps,www,ftp,imaps,domain,https -
ACCEPT loc dmz tcp smtp
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# Internet to ALL -- drop NewNotSyn packets
#
dropNotSyn net fw tcp
#dropNotSyn net loc tcp
dropNotSyn net dmz tcp
###############################################################################################################################################################################
# Internet to DMZ
#
ACCEPT net dmz udp domain
LOG:$LOG net:64.126.128.0/18 dmz tcp smtp
ACCEPT net dmz tcp smtps,www,ftp,imaps,domain,https -
ACCEPT net dmz tcp smtp - 206.124.146.177,206.124.146.178
ACCEPT net dmz udp 33434:33454
Mirrors net dmz tcp rsync
Limit:$LOG:SSHA,3,60\
net dmz tcp 22
Trcrt/ACCEPT net dmz
##############################################################################################################################################################################
#
# Net to Local
#
# When I'm "on the road", the following two rules allow me VPN access back home using PPTP.
#
DNAT net loc:192.168.1.4 tcp 1729
DNAT net loc:192.168.1.4 gre
#
# Roadwarrior access to Ursa
#
ACCEPT net:$OMAK loc tcp 22
Limit:$LOG:SSHA,3,60\
net loc tcp 22
#
# ICQ
#
ACCEPT net loc:192.168.1.3 tcp 113,4000:4100
#
# Bittorrent
#
ACCEPT net loc:192.168.1.3 tcp 6881:6889,6969
ACCEPT net loc:192.168.1.3 udp 6881:6889,6969
#
# Real Audio
#
ACCEPT net loc:192.168.1.3 udp 6970:7170
#
# Overnet
#
#ACCEPT net loc:192.168.1.3 tcp 4662
#ACCEPT net loc:192.168.1.3 udp 12112
#
# OpenVPN
#
ACCEPT net loc:192.168.1.3 udp 1194
ACCEPT net loc:192.168.1.6 udp 1194
# Skype
#
ACCEPT net loc:192.168.1.6 tcp 1194
#
# Traceroute
#
Trcrt/ACCEPT net loc:192.168.1.3
#
# Silently Handle common probes
#
REJECT net loc tcp www,ftp,https
DROP net loc icmp 8
###############################################################################################################################################################################
# DMZ to Internet
#
ACCEPT dmz net udp domain,ntp
ACCEPT dmz net tcp echo,ftp,ssh,smtp,whois,domain,www,81,https,cvspserver,2702,2703,8080
ACCEPT dmz net:$POPSERVERS tcp pop3
Ping/ACCEPT dmz net
#
# Some FTP clients seem prone to sending the PORT command split over two packets. This prevents the FTP connection tracking
# code from processing the command and setting up the proper expectation. The following rule allows active FTP to work in these cases
# but logs the connection so I can keep an eye on this potential security hole.
#
ACCEPT:$LOG dmz net tcp 1024: 20
###############################################################################################################################################################################
# Local to DMZ
#
ACCEPT loc dmz udp domain,xdmcp
ACCEPT loc dmz tcp www,smtp,smtps,domain,ssh,imap,rsync,https,imaps,ftp,10023,pop3,3128
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# DMZ to Local
#
ACCEPT dmz loc:192.168.1.5 udp 123
ACCEPT dmz loc:192.168.1.5 tcp 21
Ping/ACCEPT dmz loc
###############################################################################################################################################################################
# DMZ to Firewall -- ntp &amp; snmp, Silently reject Auth
#
#ACCEPT net loc:192.168.1.3 udp 12112
#
# OpenVPN
#
ACCEPT net loc:192.168.1.3 udp 1194
ACCEPT net loc:192.168.1.6 udp 1194
# Skype
#
ACCEPT net loc:192.168.1.6 tcp 1194
#
# Traceroute
#
Trcrt/ACCEPT net loc:192.168.1.3
#
# Silently Handle common probes
#
REJECT net loc tcp www,ftp,https
DROP net loc icmp 8
###############################################################################################################################################################################
# DMZ to Internet
#
ACCEPT dmz net udp domain,ntp
ACCEPT dmz net tcp echo,ftp,ssh,smtp,whois,domain,www,81,https,cvspserver,2702,2703,8080
ACCEPT dmz net:$POPSERVERS tcp pop3
Ping/ACCEPT dmz net
#
# Some FTP clients seem prone to sending the PORT command split over two packets. This prevents the FTP connection tracking
# code from processing the command and setting up the proper expectation. The following rule allows active FTP to work in these cases
# but logs the connection so I can keep an eye on this potential security hole.
#
ACCEPT:$LOG dmz net tcp 1024: 20
###############################################################################################################################################################################
# Local to DMZ
#
ACCEPT loc dmz udp domain,xdmcp
ACCEPT loc dmz tcp www,smtp,smtps,domain,ssh,imap,rsync,https,imaps,ftp,10023,pop3,3128
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# DMZ to Local
#
ACCEPT dmz loc:192.168.1.5 udp 123
ACCEPT dmz loc:192.168.1.5 tcp 21
Ping/ACCEPT dmz loc
###############################################################################################################################################################################
# DMZ to Firewall -- ntp &amp; snmp, Silently reject Auth
#
ACCEPT loc dmz udp domain,xdmcp
ACCEPT loc dmz tcp www,smtp,smtps,domain,ssh,imap,rsync,https,imaps,ftp,10023,pop3,3128
Trcrt/ACCEPT loc dmz
###############################################################################################################################################################################
# DMZ to Local
#
ACCEPT dmz loc:192.168.1.5 udp 123
ACCEPT dmz loc:192.168.1.5 tcp 21
Ping/ACCEPT dmz loc
###############################################################################################################################################################################
# DMZ to Firewall -- ntp &amp; snmp, Silently reject Auth
#
ACCEPT dmz fw tcp 161,ssh
ACCEPT dmz fw udp 161,ntp
REJECT dmz fw tcp auth
Ping/ACCEPT dmz fw
###############################################################################################################################################################################
# Internet to Firewall
#
REJECT net fw tcp www,ftp,https
DROP net fw icmp 8
ACCEPT net fw udp 33434:33454
ACCEPT net:$OMAK fw udp ntp
ACCEPT net fw tcp auth
ACCEPT net:$OMAK fw tcp 22
Limit:$LOG:SSHA,3,60\
net fw tcp 22
Trcrt/ACCEPT net fw
#
# Bittorrent
#
ACCEPT net fw tcp 6881:6889,6969
ACCEPT net fw udp 6881:6889,6969
###############################################################################################################################################################################
# Firewall to DMZ
#
ACCEPT fw dmz tcp domain,www,ftp,ssh,smtp,https,993,465
ACCEPT fw dmz udp domain
REJECT fw dmz udp 137:139
Ping/ACCEPT fw dmz
##############################################################################################################################################################################
# Avoid logging Freenode.net probes
#
DROP net:82.96.96.3 all
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
<para><filename>/etc/shorewall/tcdevices</filename></para>
<programlisting>#INTERFACE IN-BANDWITH OUT-BANDWIDTH
$EXT_IF 1300kbit 384kbit
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
</programlisting>
<para><filename>/etc/shorewall/tcclasses</filename><programlisting>#INTERFACE MARK RATE CEIL PRIORITY OPTIONS
$EXT_IF 10 5*full/10 full 1 tcp-ack,tos-minimize-delay
$EXT_IF 20 3*full/10 9*full/10 2 default
$EXT_IF 30 2*full/10 6*full/10 3
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting></para>
<para><filename>/etc/shorewall/tcrules</filename><programlisting>#MARK SOURCE DEST PROTO PORT(S) CLIENT USER TEST
# PORT(S)
1:110 192.168.0.0/22 $EXT_IF #Our internel nets get priority
#over the server
1:130 206.124.146.177 $EXT_IF tcp - 873 #Throttle rsync traffic to the
#Shorewall Mirrors.
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting></para>
</blockquote>
<para>The <filename class="devicefile">tap0</filename> device used by
the bridged OpenVPN server is created and bridged to <filename
class="devicefile">eth1</filename> using a SuSE-specific SysV init
script:</para>
<blockquote>
<programlisting>#!/bin/sh
#
# The Shoreline Firewall (Shorewall) Packet Filtering Firewall - V3.0
#
# This program is under GPL [http://www.gnu.org/copyleft/gpl.htm]
#
# (c) 1999,2000,2001,2002,2003,2004,2005 - Tom Eastep (teastep@shorewall.net)
#
# On most distributions, this file should be called /etc/init.d/shorewall.
#
# Complete documentation is available at http://shorewall.net
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of Version 2 of the GNU General Public License
# as published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA
#
# If an error occurs while starting or restarting the firewall, the
# firewall is automatically stopped.
#
# Commands are:
#
# bridge start Starts the bridge
# bridge restart Restarts the bridge
# bridge reload Restarts the bridge
# bridge stop Stops the bridge
# bridge status Displays bridge status
#
# chkconfig: 2345 4 99
# description: Packet filtering firewall
### BEGIN INIT INFO
# Provides: bridge
# Required-Start: boot.udev
# Required-Stop:
# Default-Start: 2 3 5
# Default-Stop: 0 1 6
# Description: starts and stops the bridge
### END INIT INFO
################################################################################
# Interfaces to be bridged -- may be listed by device name or by MAC
#
INTERFACES="eth1"
#
# Tap Devices
#
TAPS="tap0"
################################################################################
# Give Usage Information #
################################################################################
usage() {
echo "Usage: $0 start|stop|reload|restart|status"
exit 1
}
#################################################################################
# Find the interface with the passed MAC address
#################################################################################
find_interface_by_mac() {
local mac=$1 first second rest dev
/sbin/ip link ls | while read first second rest; do
case $first in
*:)
dev=$second
;;
*)
if [ "$second" = $mac ]; then
echo ${dev%:}
return
fi
esac
done
}
################################################################################
# Convert MAC addresses to interface names
################################################################################
get_interfaces() {
local interfaces= interface
for interface in $INTERFACES; do
case $interface in
*:*:*)
interface=$(find_interface_by_mac $interface)
[ -n "$interface" ] || echo "WARNING: Can't find an interface with MAC address $mac"
;;
esac
interfaces="$interfaces $interface"
done
INTERFACES="$interfaces"
}
################################################################################
# Start the Bridge
################################################################################
do_start()
{
local interface
get_interfaces
for interface in $TAPS; do
/usr/sbin/openvpn --mktun --dev $interface
done
/sbin/brctl addbr br0
for interface in $INTERFACES $TAPS; do
/sbin/ip link set $interface up
/sbin/brctl addif br0 $interface
done
}
################################################################################
# Stop the Bridge
################################################################################
do_stop()
{
local interface
get_interfaces
for interface in $INTERFACES $TAPS; do
/sbin/brctl delif br0 $interface
/sbin/ip link set $interface down
done
/sbin/ip link set br0 down
/sbin/brctl delbr br0
for interface in $TAPS; do
/usr/sbin/openvpn --rmtun --dev $interface
done
}
################################################################################
# E X E C U T I O N B E G I N S H E R E #
################################################################################
command="$1"
case "$command" in
start)
do_start
;;
stop)
do_stop
;;
restart|reload)
do_stop
do_start
;;
status)
/sbin/brctl show
;;
*)
usage
;;
esac
</programlisting>
</blockquote>
</section>
</section>
</article>
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