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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
"http://www.oasis-open.org/docbook/xml/4.4/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>
<year>2007</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 4.0 and later. If you are running
a version of Shorewall earlier than Shorewall 4.0.0 then please see the
documentation for that release.</para>
</caution>
<section id="Before">
<title>Before Xen</title>
<para>Prior to adopting Xen, 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 id="After">
<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 --
Now replaced by a Hewlett-Packard Pavilion a1510y).</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>OpenSuSE </trademark>10.3 or
<trademark>Ubuntu</trademark> "Gutsy Gibbon".</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.</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 three 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>A DomU (Domain name <emphasis role="bold">lists</emphasis>, DNS
name <emphasis role="bold">lists.shorewall.net</emphasis>) that is
used as a public Web/FTP/Mail/DNS server.</para>
</listitem>
<listitem>
<para>A DomU (Domain name <emphasis role="bold">test</emphasis>, DNS
name <emphasis role="bold">test.shorewall.net</emphasis>) that I use
for Shorewall testing.</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="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>.<important>
<para>The files from <filename
class="directory">/etc/xen/auto</filename> shown below correspond to
my configuration under Xen 3.0. I'm now running Xen 3.1 which does
not use configuration files for the domains but rather keeps the
configuration in a database managed by xend. See <link
linkend="Xen3.1">below</link>.</para>
</important></para>
<blockquote>
<para><filename>/boot/grub/menu.lst</filename> — here is the entry
that boots Xen in Dom0.</para>
<blockquote>
<programlisting>title Kernel-2.6.18.8-0.1-xen
root (hd0,5)
kernel /boot/xen.gz
module /boot/vmlinuz-2.6.18.8-0.1-xen root=/dev/sda6 vga=0x31a resume=/dev/sda5 splash=silent showopts
module /boot/initrd-2.6.18.8-0.1-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>disk = [ 'phy:/dev/sda9,hda,w', 'phy:/dev/hda,hdb,r' ]
memory = 512
vcpus = 1
builder = 'linux'
name = 'server'
vif = [ 'mac=00:16:3e:b1:d7:90, <emphasis role="bold">ip=206.124.146.177, vifname=eth3</emphasis>' ]
localtime = 0
on_poweroff = 'destroy'
on_reboot = 'restart'
on_crash = 'restart'
extra = ' TERM=xterm'
bootloader = '/usr/lib/xen/boot/domUloader.py'
bootentry = 'hda2:/boot/vmlinuz-xen,/boot/initrd-xen'</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><filename>/etc/xen/auto/02-test</filename> — configuration file
for the test domain.</para>
<blockquote>
<programlisting>disk = [ 'phy:/dev/hdb4,hda,w', 'phy:/dev/hda,hdb,r' ]
memory = 512
vcpus = 1
builder = 'linux'
name = 'test'
vif = [ 'mac=00:16:3e:83:ad:28, <emphasis role="bold">ip=192.168.1.7</emphasis>, <emphasis
role="bold">vifname=eth4</emphasis>' ]
localtime = 0
on_poweroff = 'destroy'
on_reboot = 'restart'
on_crash = 'restart'
extra = ' TERM=xterm'
bootloader = '/usr/lib/xen/boot/domUloader.py'
bootentry = 'hda2:/boot/vmlinuz-xen,/boot/initrd-xen'
</programlisting>
</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>
</blockquote>
<para id="Xen3.1">Instructions for editing entries in the Xen 3.1 xend
database may be found at <ulink
url="http://www.novell.com/documentation/vmserver/config_options/index.html?page=/documentation/vmserver/config_options/data/b8uh3zr.html">http://www.novell.com/documentation/vmserver/config_options/index.html?page=/documentation/vmserver/config_options/data/b8uh3zr.html</ulink>,
The following are excerpts from the XML representations of the two user
domains (produced by "xm list -l …").</para>
<para>lists domain:<blockquote>
<para><programlisting>…
(features )
<emphasis role="bold"> (on_xend_start start)
(on_xend_stop shutdown)</emphasis>
(start_time 1194710550.49)
…
(console_mfn 397179)
(device
(vif
<emphasis role="bold"> (mac 00:16:3e:b1:d7:90)
(script vif-route)
(ip 206.124.146.177)
(vifname eth3)</emphasis>
(type netfront)
(devid 0)
(uuid 55676385-7b69-09fd-4027-751b692ead75)
)
)
(device
(vbd
…</programlisting></para>
</blockquote></para>
<para>test domain:<blockquote>
<para><programlisting>…
(console_mfn 418003)
(device
(vif
(uuid 64a1dd48-fa8b-7561-e90b-cd589cbeb7fa)
<emphasis role="bold"> (script vif-route)
(ip 192.168.1.7)
(mac 00:16:3e:83:ad:28)
(vifname eth4)
</emphasis> (devid 0)
(type netfront)
(backend 0)
)
)
(device
(vbd
…</programlisting></para>
</blockquote></para>
<para>With the three 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>
<para>Readers who are paying attention will notice that eth4 has the
same public IP address (206.124.146.176) as eth0 (and eth3), yet the
<emphasis role="bold">test</emphasis> system connected to that interface
has an RFC 1918 address (192.168.1.7). That configuration is established
by Xen which clones the primary IP address of eth0 on all of the routed
virtual interfaces that it creates. <emphasis
role="bold">test</emphasis> is configured with its default route via
192.168.1.254 which is the IP address of the firewall's br0. That works
because of the way that the Linux network stack treats local IPv4
addresses; by default, it will respond to ARP "who-has" broadcasts for
any local address and not just for the addresses on the interface that
received the broadcast (but of course the MAC address returned in the
"here-is" response is that of the interface that received the
broadcast). So when <emphasis role="bold">test</emphasis> broadcasts
"who-has 192.168.1.254", the firewall responds with "here-is
192.168.1.254 00:16:3e:83:ad:28" (00:16:3e:83:ad:28 is the MAC of
virtual interface eth4).</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> and <emphasis
role="bold">test</emphasis> domains when the <filename
class="devicefile">eth0</filename> device was brought up:</para>
<para><command>ethtool -K eth0 tx off</command></para>
<para>Under <trademark>OpenSuSE</trademark> 10.2, I placed the
following in
<filename><filename>/etc/sysconfig/network/ifcfg-eth-id-00:16:3e:b1:d7:90</filename></filename>
(the config file for eth0):</para>
<programlisting>ETHTOOL_OPTIONS='-K iface tx off'</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
<emphasis role="bold">post-up ethtool -K eth0 tx off</emphasis></programlisting>
</caution>
<caution>
<para>Update. Under OpenSuSE 10.2, communication from a domU works
okay without running ethtool <emphasis role="bold">but traffic shaping
in dom0 doesn't work!</emphasis> So it's a good idea to run it just to
be safe.</para>
</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 road warrior access for our three 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 three 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 OpenSuSE network
configuration.</para>
<blockquote>
<para>/etc/shorewall/shorewall.conf</para>
<programlisting>STARTUP_ENABLED=Yes
VERBOSITY=0
SHOREWALL_COMPILER=perl
LOGFILE=/var/log/firewall
LOGFORMAT="Shorewall:%s:%s:"
LOGTAGONLY=No
LOGRATE=
LOGBURST=
LOGALLNEW=
BLACKLIST_LOGLEVEL=
MACLIST_LOG_LEVEL=$LOG
TCP_FLAGS_LOG_LEVEL=$LOG
SMURF_LOG_LEVEL=$LOG
LOG_MARTIANS=No
IPTABLES=
SHOREWALL_SHELL=/bin/ash
SUBSYSLOCK=/var/lock/subsys/shorewall
MODULESDIR=
CONFIG_PATH=/etc/shorewall:/usr/share/shorewall
RESTOREFILE=
IPSECFILE=zones
LOCKFILE=
DROP_DEFAULT="Drop"
REJECT_DEFAULT="Reject"
ACCEPT_DEFAULT="none"
QUEUE_DEFAULT="none"
IP_FORWARDING=Yes
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=No
MODULE_SUFFIX=
DISABLE_IPV6=Yes
BRIDGING=No
DYNAMIC_ZONES=No
PKTTYPE=No
MACLIST_TABLE=mangle
MACLIST_TTL=60
SAVE_IPSETS=No
MAPOLDACTIONS=No
FASTACCEPT=Yes
IMPLICIT_CONTINUE=Yes
HIGH_ROUTE_MARKS=Yes
USE_ACTIONS=Yes
OPTIMIZE=1
EXPORTPARAMS=No
EXPAND_POLICIES=Yes
KEEP_RT_TABLES=No
DELETE_THEN_ADD=No
BLACKLIST_DISPOSITION=DROP
MACLIST_DISPOSITION=DROP
TCP_FLAGS_DISPOSITION=DROP</programlisting>
<para><filename>/etc/shorewall/zones</filename>:</para>
<programlisting>#ZONE TYPE OPTIONS IN_OPTIONS OUT_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</programlisting>
<para><filename>/etc/shorewall/policy</filename>:</para>
<programlisting>#SOURCE DEST POLICY LOGLEVEL LIMIT
$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</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
TEST_IF=eth4
OMAK=&lt;IP address at our second home&gt;</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> (don't specify
the BROADCAST addresses if you are using Shorewall-perl):</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net ${EXT_IF} detect dhcp,logmartians=1,blacklist
dmz $DMZ_IF detect logmartians=1
loc $INT_IF detect dhcp,logmartians=1,routeback,bridge
loc $TEST_IF detect optional
loc $TEST1_IF detect optional
wifi $WIFI_IF detect dhcp,maclist,mss=1400
vpn tun+ -
</programlisting>
<para><filename>/etc/shorewall/nat</filename>:</para>
<programlisting>#EXTERNAL INTERFACE INTERNAL ALLINTS LOCAL
COMMENT One-to-one NAT
206.124.146.178 $EXT_IF:0 192.168.1.3 No No
206.124.146.180 $EXT_IF:2 192.168.1.6 No No</programlisting>
<para><filename>/etc/shorewall/masq (Note the cute trick here and in
the <filename>following proxyarp</filename> file that allows me to
access the DSL "Modem" using its default IP address
(192.168.1.1))</filename>. The leading "+" is required to place the
rule before the SNAT rules generated by entries in
<filename>/etc/shorewall/nat</filename> above.</para>
<programlisting>#INTERFACE SOURCE ADDRESS PROTO DPORT IPSEC
COMMENT Handle DSL 'Modem'
+$EXT_IF:192.168.1.1 0.0.0.0/0 192.168.1.254
COMMENT Masquerade VPN clients and Wifi
$EXT_IF 192.168.2.0/24
$EXT_IF 192.168.3.0/24
$EXT_IF:192.168.98.1 192.168.99.1 192.168.1.99
$EXT_IF:192.168.99.1 192.168.98.1 192.168.1.98
COMMENT Masquerade Local Network
$EXT_IF 192.168.1.0/24 206.124.146.179</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
192.168.1.7 $TEST_IF $INT_IF yes</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</programlisting>
<para><filename>/etc/shorewall/actions</filename>:</para>
<programlisting>#ACTION
Mirrors # Accept traffic from Shorewall Mirrors</programlisting>
<para><filename>/etc/shorewall/action.Mirrors</filename>:</para>
<programlisting>#TARGET SOURCE DEST PROTO DPORT SPORT ORIGDEST RATE
ACCEPT $MIRRORS</programlisting>
<para><filename>/etc/shorewall/rules</filename>:</para>
<programlisting>SECTION NEW
###############################################################################################################################################################################
#ACTION SOURCE DEST PROTO DPORT SPORT ORIGDEST RATE USER
###############################################################################################################################################################################
REJECT:$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
</programlisting>
<para><filename>etc/shorewall/tcdevices</filename></para>
<programlisting>#INTERFACE IN_BANDWITH OUT_BANDWIDTH
$EXT_IF 1300kbit 384kbit
</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</programlisting></para>
<para><filename>/etc/shorewall/mangle</filename><programlisting>#ACTION SOURCE DEST PROTO DPORT SPORT USER TEST
CLASSIFY(1:110) 192.168.0.0/22 $EXT_IF #Our internal nets get priority
#over the server
CLASSIFY(1:130) 206.124.146.177 $EXT_IF tcp - 873 #Throttle rsync traffic to the
#Shorewall Mirrors.</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/licenses/old-licenses/gpl-2.0.txt]
#
# (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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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
mac=$1
local first
local second
local rest
local 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
interfaces=
local 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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