#!/bin/sh

EXT_IF="eth0"
INT_IF="eth1"
LOCAL_LAN="192.168.114.0/24"
REMOTE_LAN1="192.168.0.0/24"
REMOTE_LAN2="192.168.1.0/24"
REMOTE_LAN3="10.20.0.0/8"
IPTABLES="/sbin/iptables"

$IPTABLES -t mangle -F
$IPTABLES -t mangle -X
$IPTABLES -t nat -F
$IPTABLES -t nat -X
$IPTABLES -F
$IPTABLES -X

case "$1" in
   start)
     echo -n "Starting firewall.." 

#Flush then restrict
$IPTABLES -F
$IPTABLES -P FORWARD DROP
$IPTABLES -P INPUT DROP 
$IPTABLES -P OUTPUT ACCEPT


# Public Networks
$IPTABLES -A INPUT -s 202.X.X.0/28 -j ACCEPT

# Allowed Services
$IPTABLES -A INPUT -p tcp -m multiport --dport 80,443 -i eth0 -j ACCEPT

# Allow DNS
$IPTABLES -A INPUT -p tcp --dport 53 -j ACCEPT
$IPTABLES -A INPUT -p udp --dport 53 -j ACCEPT

# Allow FTP
$IPTABLES -A INPUT -p tcp -m tcp --dport 21 -j ACCEPT

# Allow SSH
$IPTABLES -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT

# Allow access from LAN
$IPTABLES -t nat -A POSTROUTING -s $LOCAL_LAN -o $EXT_IF -j SNAT --to 202.X.X.10

# Mark VPN packets
$IPTABLES -t mangle -A PREROUTING -i $EXT_IF -p esp -j MARK --set-mark 1 #VPN

$IPTABLES -t nat -A PREROUTING -s $REMOTE_LAN1 -i $EXT_IF -m mark --mark 1 -j ACCEPT
$IPTABLES -t nat -A PREROUTING -s $REMOTE_LAN2 -i $EXT_IF -m mark --mark 1 -j ACCEPT
$IPTABLES -t nat -A PREROUTING -s $REMOTE_LAN3 -i $EXT_IF -m mark --mark 1 -j ACCEPT

$IPTABLES -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

$IPTABLES -A INPUT -i eth1 -p icmp -j ACCEPT
$IPTABLES -A INPUT -i $EXT_IF -p udp -m udp --dport 500 -j ACCEPT #VPN
$IPTABLES -A INPUT -i $EXT_IF -m mark --mark 1 -j ACCEPT

$IPTABLES -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
$IPTABLES -A FORWARD -i $EXT_IF -m mark --mark 1 -j ACCEPT
$IPTABLES -A FORWARD -i $INT_IF -j ACCEPT

# Allow loopback-device
$IPTABLES -A INPUT -i lo -j ACCEPT

# Spoof protection
$IPTABLES -t nat -A PREROUTING -d $LOCAL_LAN -i $EXT_IF -j DROP

echo "..done"
     ;;
   stop)
     echo -n "Stopping firewall.."
     $IPTABLES -F
     $IPTABLES -P FORWARD DROP
     $IPTABLES -P OUTPUT ACCEPT
     $IPTABLES -P INPUT ACCEPT
     echo "done"
     ;;
   *)
     echo "Usage: $NAME {start|stop}"
     exit 1
     ;;
esac

iptables -I FORWARD -p ICMP --icmp-type 11 -j DROP