About My Network Tom Eastep 2004-10-09 2001-2004 Thomas M. Eastep 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 GNU Free Documentation License.
My Current Network I use a combination of One-to-one NAT and Proxy ARP, neither of which are relevant to a simple configuration with a single public IP address. If you have just a single public IP address, most of what you see here won't apply to your setup so beware of copying parts of this configuration and expecting them to work for you. What you copy may or may not work for you. The configuration shown here corresponds to Shorewall version 2.1.7. My configuration uses features not available in earlier Shorewall releases. I have DSL service and have 5 static IP addresses (206.124.146.176-180). My DSL modem (Westell 2200) is connected to eth0 and has IP address 192.168.1.1 (factory default). The modem is configured in bridge mode so PPPoE is not involved. I have a local network connected to eth2 (subnet 192.168.1.0/24) and a DMZ connected to eth1 (206.124.146.176/32). Note that I configure the same IP address on both eth0 and eth1. In this configuration: I use one-to-one NAT for Ursa (my personal system that run SuSE 9.1) - Internal address 192.168.1.5 and external address 206.124.146.178. I use one-to-one NAT for EastepLaptop (My work system -- Windows XP SP1). Internal address 192.168.1.7 and external address 206.124.146.180. I use SNAT through 206.124.146.179 for my Wife's Windows XP system Tarry, and our  dual-booting (SuSE 9.1/Windows XP) laptop Tipper which connects through the Wireless Access Point (wap) via a Wireless Bridge (wet). While the distance between the WAP and where I usually use the laptop isn't very far (50 feet or so), using a WAC11 (CardBus wireless card) has proved very unsatisfactory (lots of lost connections). By replacing the WAC11 with the WET11 wireless bridge, I have virtually eliminated these problems (Being an old radio tinkerer (K7JPV), I was also able to eliminate the disconnects by hanging a piece of aluminum foil on the family room wall. Needless to say, my wife Tarry rejected that as a permanent solution :-). I have Ursa (193.168.1.5/206.124.146.178) configured as a 2-port bridge. Squid runs on the firewall and is configured as a transparent proxy. The firewall runs on a 384MB K-6/II with SuSE 9.1. Ursa runs Samba for file sharing with the Windows systems.. The wireless network connects to Ursa's eth0 via a LinkSys WAP11.  In additional to using the rather weak WEP 40-bit encryption (64-bit with the 24-bit preamble), I use MAC verification. This is still a weak combination and if I lived near a wireless hot spot, I would probably add IPSEC or something similar to my WiFi->local connections. The single system in the DMZ (address 206.124.146.177) runs postfix, Courier IMAP (imaps and pop3), DNS, a Web server (Apache) and an FTP server (Pure-ftpd) under Fedora Core 2. The system also runs fetchmail to fetch our email from our old and current ISPs. That server is managed through Proxy ARP. The firewall system itself runs a DHCP server that serves the local network. All administration and publishing is done using ssh/scp. I have a desktop environment installed on the firewall but I am not usually logged in to it. X applications tunnel through SSH to Ursa. The server also has a desktop environment installed and that desktop environment is available via XDMCP from the local zone. For the most part though, X tunneled through SSH is used for server administration and the server runs at run level 3 (multi-user console mode on Fedora). I run an SNMP server on my firewall to serve MRTG running in the DMZ. The ethernet interface in the Server is configured with IP address 206.124.146.177, netmask 255.255.255.0. The server's default gateway is 206.124.146.254 (Router at my ISP. This is the same default gateway used by the firewall itself). On the firewall, an entry in my /etc/network/interfaces file (see below) adds a host route to 206.124.146.177 through eth1 when that interface is brought up. Tarry (192.168.1.4) runs a PPTP server for Road Warrior access from my work laptop and the Firewall is configured with IPSEC for tunnel mode access from our second home in Omak, Washington.
Firewall Configuration
Shorewall.conf
LOGFILE=/var/log/messages LOGFORMAT="Shorewall:%s:%s " LOGRATE= LOGBURST= LOGUNCLEAN=$LOG BLACKLIST_LOGLEVEL= LOGNEWNOTSYN=$LOG MACLIST_LOG_LEVEL=$LOG TCP_FLAGS_LOG_LEVEL=$LOG RFC1918_LOG_LEVEL=$LOG SMURF_LOG_LEVEL= PATH=/usr/local/sbin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin SHOREWALL_SHELL=/bin/ash SUBSYSLOCK= STATEDIR=/var/state/shorewall MODULESDIR= CONFIG_PATH=/etc/shorewall:/etc/shorewall/actiondir:/usr/share/shorewall RESTOREFILE=standard FW=fw IP_FORWARDING=On ADD_IP_ALIASES=Yes ADD_SNAT_ALIASES=Yes TC_ENABLED=Yes CLEAR_TC=Yes MARK_IN_FORWARD_CHAIN=No CLAMPMSS=Yes ROUTE_FILTER=No DETECT_DNAT_IPADDRS=Yes MUTEX_TIMEOUT=60 NEWNOTSYN=Yes BLACKLISTNEWONLY=Yes DYNAMIC_ZONES=No DISABLE_IPV6=Yes PKTTYPE=No BLACKLIST_DISPOSITION=DROP MACLIST_DISPOSITION=REJECT TCP_FLAGS_DISPOSITION=DROP
Params File (Edited)
MIRRORS=<list of shorewall mirror ip addresses> NTPSERVERS=<list of the NTP servers I sync with> TEXAS=<ip address of gateway in Plano> OMAK=<ip address of tipper while we are at our second home> LOG=info EXT_IF=eth1 INT_IF=eth0 DMZ_IF=eth2
Zones File
#ZONE DISPLAY COMMENTS omak Omak Our Laptop at our second home net Internet Internet dmz DMZ Demilitarized zone loc Local Local networks tx Texas Peer Network in Dallas #LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Interfaces File
This is set up so that I can start the firewall before bringing up my Ethernet interfaces. #ZONE INTERFACE BROADCAST OPTIONS net $EXT_IF 206.124.146.255 dhcp,norfc1918,routefilter,blacklist,tcpflags,nosmurfs loc $INT_IF 192.168.1.255 dhcp dmz $DMZ_IF - - texas - #LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Hosts File
#ZONE HOST(S) OPTIONS tx texas:192.168.8.0/22 omak $EXT_IF:$OMAK #LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Ipsec File
#ZONE IPSEC OPTIONS IN OUT # ONLY OPTIONS OPTIONS omak yes mode=tunnel #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Routestopped File
#INTERFACE HOST(S) $DMZ_IF 206.124.146.177 $INT_IF - $EXT_IF $OMAK #LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Blacklist File (Partial)
#ADDRESS/SUBNET PROTOCOL PORT 0.0.0.0/0 udp 1434 0.0.0.0/0 tcp 1433 0.0.0.0/0 tcp 3127 0.0.0.0/0 tcp 8081 0.0.0.0/0 tcp 57 #LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
RFC1918 File
Because my DSL modem has an RFC 1918 address (192.168.1.1) and is connected to eth0, I need to make an exception for that address in my rfc1918 file. I copied /usr/share/shorewall/rfc1918 to /etc/shorewall/rfc1918 and changed it as follows: #SUBNET TARGET 192.168.1.1 RETURN 172.16.0.0/12 logdrop # RFC 1918 192.168.0.0/16 logdrop # RFC 1918 10.0.0.0/8 logdrop # RFC 1918 #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Policy File
#SOURCE DESTINATION POLICY LOG LEVEL BURST:LIMIT fw fw ACCEPT loc net ACCEPT fw sec ACCEPT omak fw ACCEPT fw omak ACCEPT omak loc ACCEPT loc omak ACCEPT omak net NONE net omak NONE omak dmz NONE dmz omak NONE omak tx NONE tx omak NONE $FW loc ACCEPT #Firewall to Local $FW tx ACCEPT loc tx ACCEPT loc fw REJECT $LOG dmz tx ACCEPT net all DROP $LOG 10/sec:40 all all REJECT $LOG #LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Masq File
Although most of our internal systems use one-to-one NAT, my wife's system (192.168.1.4) uses IP Masquerading (actually SNAT) as does our laptop (192.168.1.8) and visitors with laptops. The first entry allows access to the DSL modem and uses features introduced in Shorewall 2.1.1. The leading plus sign ("+_") causes the rule to be placed before rules generated by the /etc/shorewall/nat file below. The double colons ("::") causes the entry to be exempt from ADD_SNAT_ALIASES=Yes in my shorewall.conf file above. #INTERFACE SUBNET ADDRESS +$EXT_IF::192.168.1.1 0.0.0.0/0 192.168.1.254 $EXT_IF:2 eth2 206.124.146.179 #LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
NAT File
#EXTERNAL INTERFACE INTERNAL ALL INTERFACES LOCAL 206.124.146.178 eth0:0 192.168.1.5 No No 206.124.146.180 eth0:1 192.168.1.7 No No #LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
Proxy ARP File
I configure the host route to 206.124.146.177 on eth1 using the Yast2 Network Interface tool; the Gateway is specified as 0.0.0.0 which indicates that the host is directly attached to the LAN on that interface. #ADDRESS INTERFACE EXTERNAL HAVEROUTE PERSISTENT 206.124.146.177 eth1 eth0 Yes 192.168.1.1 eth0 eth2 yes # Allow access to DSL modem from the local zone #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Tunnels File (Shell variables TEXAS and OMAK set in /etc/shorewall/params)
#TYPE ZONE GATEWAY GATEWAY ZONE PORT gre net $TEXAS ipsec:noah net $OMAK omak #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Actions File
#ACTION Mirrors #Accept traffic from the Shorewall Mirror sites #LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
action.Mirrors File
The $MIRRORS variable expands to a list of approximately 10 IP addresses. So moving these checks into a separate chain reduces the number of rules that most net->dmz traffic needs to traverse. #TARGET SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE # PORT PORT(S) DEST LIMIT ACCEPT $MIRRORS #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/action.Drop
This is my common action for the DROP policy. It is like the standard Drop action except that it allows Ping. #TARGET SOURCE DEST PROTO DEST SOURCE RATE USER/ # PORT(S) PORT(S) LIMIT GROUP RejectAuth AllowPing dropBcast DropSMB DropUPnP dropNotSyn DropDNSrep
/etc/shorewall/action.Reject
This is my common action for the REJECT policy. It is like the standard Reject action except that it allows Ping and contains one rule that guards against log flooding by broken software running in my local zone. #TARGET SOURCE DEST PROTO DEST SOURCE RATE USER/ # PORT(S) PORT(S) LIMIT GROUP RejectAuth AllowPing dropBcast RejectSMB DropUPnP dropNotSyn DropDNSrep DROP loc:eth2:!192.168.1.0/24 #So that my braindead Windows[tm] XP system doesn't flood my log #with NTP requests with a source address in 16.0.0.0/8 (address of #its PPTP tunnel to HP).
Rules File (The shell variables are set in /etc/shorewall/params)
############################################################################################################################################################################### #RESULT CLIENT(S) SERVER(S) PROTO PORT(S) CLIENT ORIGINAL RATE USER # PORT(S) DEST:SNAT SET ############################################################################################################################################################################### # Local Network to Internet - Reject attempts by Trojans to call home, direct SMTP and MS Message Service # RejectSMTP loc net tcp 25 REJECT:$LOG loc net tcp 6667,25 REJECT:$LOG loc net udp 1025:1031 # # Stop NETBIOS crap since our policy is ACCEPT # REJECT loc net tcp 137,445 REJECT loc net udp 137:139 # DROP loc:!192.168.1.0/24 net # # SQUID # REDIRECT loc 3128 tcp 80 ############################################################################################################################################################################### # Local Network to Firewall # DROP loc:!192.168.1.0/24 fw ACCEPT loc fw tcp ssh,time ACCEPT loc fw udp 161,ntp ############################################################################################################################################################################### # Local Network to DMZ # DROP loc:!192.168.1.0/24 dmz ACCEPT loc dmz udp domain,xdmcp ACCEPT loc dmz tcp www,smtp,smtps,domain,ssh,imap,https,imaps,cvspserver,ftp,10027,pop3 - ############################################################################################################################################################################### # Internet to ALL -- drop NewNotSyn packets # dropNotSyn net fw tcp dropNotSyn net loc tcp dropNotSyn net dmz tcp # # Drop ping to firewall and local # DropPing net fw DropPing net loc ############################################################################################################################################################################### # Internet to DMZ # DNAT- net dmz:206.124.146.177 tcp smtp - 206.124.146.179,206.124.146.1 78 ACCEPT net dmz tcp smtp,smtps,www,ftp,imaps,domain,https,cvspserver - ACCEPT net dmz udp domain ACCEPT net dmz udp 33434:33436 Mirrors net dmz tcp rsync AllowPing net dmz ############################################################################################################################################################################### # # Net to Local # # When I'm "on the road", the following two rules allow me VPN access back home. # DNAT net loc:192.168.1.4 tcp 1723 - DNAT net:!$TEXAS loc:192.168.1.4 gre - ACCEPT net loc:192.168.1.5 tcp 22 # # ICQ # ACCEPT net loc:192.168.1.5 tcp 4000:4100 DNAT net loc:192.168.1.8 tcp 4000:4100 - 206.124.146.179 # # Real Audio # ACCEPT net loc:192.168.1.5 udp 6970:7170 # # Overnet # #ACCEPT net loc:192.168.1.5 tcp 4662 #ACCEPT net loc:192.168.1.5 udp 12112 # # Silently Handle common probes # REJECT net loc tcp www,ftp,https ############################################################################################################################################################################### # DMZ to Internet # ACCEPT dmz net tcp smtp,domain,www,81,https,whois,echo,2702,21,2703,ssh,8080 ACCEPT dmz net udp domain REJECT:$LOG dmz net udp 1025:1031 ACCEPT dmz net:$POPSERVERS tcp pop3 # # Something is wrong with the FTP connection tracking code or there is some client out there # that is sending a PORT command which that code doesn't understand. Either way, # the following works around the problem. # ACCEPT:$LOG dmz net tcp 1024: 20 ############################################################################################################################################################################### # DMZ to Firewall -- ntp & snmp, Silently reject Auth # ACCEPT dmz fw udp ntp ntp ACCEPT dmz fw tcp 161,ssh ACCEPT dmz fw udp 161 REJECT dmz fw tcp auth ############################################################################################################################################################################### # DMZ to Local Network # ACCEPT dmz loc tcp smtp,6001:6010 ACCEPT dmz:206.124.146.177 loc:192.168.1.5 tcp 111 ACCEPT dmz:206.124.146.177 loc:192.168.1.5 udp ############################################################################################################################################################################### # Internet to Firewall # REJECT net fw tcp www,ftp,https ACCEPT net dmz udp 33434:33435 ############################################################################################################################################################################### # Firewall to Internet # ACCEPT fw net:$NTPSERVERS udp ntp ntp #ACCEPT fw net:$POPSERVERS tcp pop3 ACCEPT fw net udp domain ACCEPT fw net tcp domain,www,https,ssh,1723,whois,1863,ftp,2702,2703,7 ACCEPT fw net udp 33435:33535 ACCEPT fw net icmp REJECT:$LOG fw net udp 1025:1031 DROP fw net udp ntp ############################################################################################################################################################################### # Firewall to DMZ # ACCEPT fw dmz tcp www,ftp,ssh,smtp ACCEPT fw dmz udp domain REJECT fw dmz udp 137:139 ############################################################################################################################################################################### ACCEPT tx loc:192.168.1.5 all #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Bridge (Ursa) Configuration As mentioned above, Ursa acts as a bridge. It's view of the network is diagrammed in the following figure. I've included the files that I used to configure that system -- some of them are SuSE-specific. The configuration on Wookie can be modified to test various bridging features -- otherwise, it serves to isolate the Wireless network from the rest of our systems.
shorewall.conf
Only the changes from the defaults are shown. BRIDGING=Yes
zones
Because loc is a sub-zone of net, loc must be defined first. #ZONE DISPLAY COMMENTS loc Local Local networks net Internet The Big Bad Internet WiFi Wireless Wireless Network #LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
policy
#SOURCE DEST POLICY LOG LIMIT:BURST loc fw ACCEPT loc net NONE loc WiFi ACCEPT net fw ACCEPT net WiFi ACCEPT net loc NONE WiFi net ACCEPT fw all ACCEPT # # THE FOLLOWING POLICY MUST BE LAST # all all REJECT info #LAST LINE -- DO NOT REMOVE
interfaces
#ZONE INTERFACE BROADCAST OPTIONS - br0 192.168.1.255 dhcp #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
hosts
#ZONE HOST(S) OPTIONS loc br0:eth1:192.168.1.0/24 net br0:eth1 WiFi br0:eth0 maclist #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS LINE -- DO NOT REMOVE
rules
#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL # PORT PORT(S) DEST ACCEPT WiFi loc udp 137:139 ACCEPT WiFi loc tcp 22,80,137,139,445,631,901,3389 ACCEPT WiFi loc udp 1024: 137 ACCEPT WiFi loc udp 177,123 ACCEPT WiFi loc:192.168.1.4 tcp 1723 ACCEPT WiFi loc:192.168.1.4 47 ACCEPT WiFi loc tcp 5900:5909 ACCEPT WiFi fw tcp ssh,80,111,137,139,445,9100:9104 ACCEPT WiFi fw udp #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
routestopped
#INTERFACE HOST(S) OPTIONS br0 0.0.0.0/0 routeback #LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
maclist
#INTERFACE MAC IP ADDRESSES (Optional) br0:eth0 00:A0:1C:DB:0C:A0 192.168.1.7 #Work Laptop br0:eth0 00:04:59:0e:85:b9 #WAP11 br0:eth0 00:06:D5:45:33:3c #WET11 br0:eth0 00:0b:c1:53:cc:97 192.168.1.8 #TIPPER #LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
/etc/init.d/bridge
This file is SuSE-specific and creates the bridge device br0. A script for other distributions would be similar (see the Shorewall Bridge documentation for examples). #!/bin/sh ################################################################################ # Script to create a bridge # # This program is under GPL [http://www.gnu.org/copyleft/gpl.htm] # # (c) 2004 - Tom Eastep (teastep@shorewall.net) # # Modify the following variables to match your configuration # #### BEGIN INIT INFO # Provides: bridge # Required-Start: coldplug # Required-Stop: # Default-Start: 2 3 5 # Default-Stop: 0 1 6 # Description: starts and stops a bridge ### END INIT INFO # # chkconfig: 2345 05 89 # description: Layer 2 Bridge # ################################################################################ PATH=$PATH:/sbin:/usr/sbin:/usr/local/sbin INTERFACES="eth0 eth1" BRIDGE="br0" do_stop() { echo "Stopping Bridge $BRIDGE" brctl delbr $BRIDGE for interface in $INTERFACES; do ip link set $interface down done } do_start() { echo "Starting Bridge $BRIDGE" for interface in $INTERFACES; do ip link set $interface up done brctl addbr $BRIDGE for interface in $INTERFACES; do brctl addif $BRIDGE $interface done } case "$1" in start) do_start ;; stop) do_stop ;; restart) do_stop sleep 1 do_start ;; *) echo "Usage: $0 {start|stop|restart}" exit 1 esac exit 0
/etc/sysconfig/network/ifcfg-br0
This file is SuSE-specific BOOTPROTO='dhcp' REMOTE_IPADDR='' STARTMODE='onboot' UNIQUE='3hqH.MjuOqWfSZ+C' WIRELESS='no' MTU=''
/etc/sysconfig/network/routes
This file is SuSE-specific 192.168.1.0/24 dev br0 proto kernel scope link src 192.168.1.5 127.0.0.0/8 dev lo scope link default via 192.168.1.254 dev br0