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+#!/bin/sh
+
+# A Sample OpenVPN-aware firewall.
+
+# eth0 is connected to the internet.
+# eth1 is connected to a private subnet.
+
+# Change this subnet to correspond to your private
+# ethernet subnet.  Home will use HOME_NET/24 and
+# Office will use OFFICE_NET/24.
+PRIVATE=10.0.0.0/24
+
+# Loopback address
+LOOP=127.0.0.1
+
+# Delete old iptables rules
+# and temporarily block all traffic.
+iptables -P OUTPUT DROP
+iptables -P INPUT DROP
+iptables -P FORWARD DROP
+iptables -F
+
+# Set default policies
+iptables -P OUTPUT ACCEPT
+iptables -P INPUT DROP
+iptables -P FORWARD DROP
+
+# Prevent external packets from using loopback addr
+iptables -A INPUT -i eth0 -s $LOOP -j DROP
+iptables -A FORWARD -i eth0 -s $LOOP -j DROP
+iptables -A INPUT -i eth0 -d $LOOP -j DROP
+iptables -A FORWARD -i eth0 -d $LOOP -j DROP
+
+# Anything coming from the Internet should have a real Internet address
+iptables -A FORWARD -i eth0 -s 192.168.0.0/16 -j DROP
+iptables -A FORWARD -i eth0 -s 172.16.0.0/12 -j DROP
+iptables -A FORWARD -i eth0 -s 10.0.0.0/8 -j DROP
+iptables -A INPUT -i eth0 -s 192.168.0.0/16 -j DROP
+iptables -A INPUT -i eth0 -s 172.16.0.0/12 -j DROP
+iptables -A INPUT -i eth0 -s 10.0.0.0/8 -j DROP
+
+# Block outgoing NetBios (if you have windows machines running
+# on the private subnet).  This will not affect any NetBios
+# traffic that flows over the VPN tunnel, but it will stop
+# local windows machines from broadcasting themselves to
+# the internet.
+iptables -A FORWARD -p tcp --sport 137:139 -o eth0 -j DROP
+iptables -A FORWARD -p udp --sport 137:139 -o eth0 -j DROP
+iptables -A OUTPUT -p tcp --sport 137:139 -o eth0 -j DROP
+iptables -A OUTPUT -p udp --sport 137:139 -o eth0 -j DROP
+
+# Check source address validity on packets going out to internet
+iptables -A FORWARD -s ! $PRIVATE -i eth1 -j DROP
+
+# Allow local loopback
+iptables -A INPUT -s $LOOP -j ACCEPT
+iptables -A INPUT -d $LOOP -j ACCEPT
+
+# Allow incoming pings (can be disabled)
+iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
+
+# Allow services such as www and ssh (can be disabled)
+iptables -A INPUT -p tcp --dport http -j ACCEPT
+iptables -A INPUT -p tcp --dport ssh -j ACCEPT
+
+# Allow incoming OpenVPN packets
+# Duplicate the line below for each
+# OpenVPN tunnel, changing --dport n
+# to match the OpenVPN UDP port.
+#
+# In OpenVPN, the port number is
+# controlled by the --port n option.
+# If you put this option in the config
+# file, you can remove the leading '--'
+#
+# If you taking the stateful firewall
+# approach (see the OpenVPN HOWTO),
+# then comment out the line below.
+
+iptables -A INPUT -p udp --dport 1194 -j ACCEPT
+
+# Allow packets from TUN/TAP devices.
+# When OpenVPN is run in a secure mode,
+# it will authenticate packets prior
+# to their arriving on a tun or tap
+# interface.  Therefore, it is not
+# necessary to add any filters here,
+# unless you want to restrict the
+# type of packets which can flow over
+# the tunnel.
+
+iptables -A INPUT -i tun+ -j ACCEPT
+iptables -A FORWARD -i tun+ -j ACCEPT
+iptables -A INPUT -i tap+ -j ACCEPT
+iptables -A FORWARD -i tap+ -j ACCEPT
+
+# Allow packets from private subnets
+iptables -A INPUT -i eth1 -j ACCEPT
+iptables -A FORWARD -i eth1 -j ACCEPT
+
+# Keep state of connections from local machine and private subnets
+iptables -A OUTPUT -m state --state NEW -o eth0 -j ACCEPT
+iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
+iptables -A FORWARD -m state --state NEW -o eth0 -j ACCEPT
+iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
+
+# Masquerade local subnet
+iptables -t nat -A POSTROUTING -s $PRIVATE -o eth0 -j MASQUERADE