#!/bin/sh
#
service iptables stop

# variable
IPTABLES="/sbin/iptables"
LO_IFACE="lo"
LO_IP="127.0.0.1"
INET_IFACE="eth2"
INET_IP="193.X/maska"
LAN_IFACE1="eth0"
LAN_IP1="10.X/255.255.255.0"
LAN_IFACE2="eth1"
LAN_IP2="10.X/255.255.255.0"

# Set policies
$IPTABLES -P INPUT DROP
$IPTABLES -P OUTPUT DROP
$IPTABLES -P FORWARD DROP

# clear all
$IPTABLES -F
$IPTABLES -X

# Create chain for bad tcp packets
$IPTABLES -N bad_tcp_packets

# Create separate chains for ICMP, TCP and UDP to traverse
$IPTABLES -N allowed
$IPTABLES -N tcp_packets
$IPTABLES -N udp_packets
$IPTABLES -N icmp_packets

# bad_tcp_packets chain
$IPTABLES -A bad_tcp_packets -p tcp --tcp-flags SYN,ACK SYN,ACK -m state --state NEW -j REJECT --reject-with tcp-reset
$IPTABLES -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j LOG --log-prefix "New not syn:"
$IPTABLES -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j DROP

# allowed chain
$IPTABLES -A allowed -p TCP --syn -j ACCEPT
$IPTABLES -A allowed -p TCP -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A allowed -p TCP -j DROP

# TCP rules
# ftp(20,21),ssh(22),smtp(25),pop3(110),imap(143)
$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 20 -j allowed
$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 21 -j allowed
$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 22 -j allowed
$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 25 -j allowed
$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 110 -j allowed
$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 143 -j allowed

# UDP ports
$IPTABLES -A udp_packets -p UDP -s 0/0 --source-port 20 -j ACCEPT
$IPTABLES -A udp_packets -p UDP -s 0/0 --source-port 21 -j ACCEPT
$IPTABLES -A udp_packets -p UDP -s 0/0 --source-port 22 -j ACCEPT
$IPTABLES -A udp_packets -p UDP -s 0/0 --source-port 25 -j ACCEPT
$IPTABLES -A udp_packets -p UDP -s 0/0 --source-port 110 -j ACCEPT
$IPTABLES -A udp_packets -p UDP -s 0/0 --source-port 143 -j ACCEPT

# ICMP rules
$IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 8 -j ACCEPT
$IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 11 -j ACCEPT

# 
#    INPUT chain
#

# Bad TCP packets we don't want.
$IPTABLES -A INPUT -p tcp -j bad_tcp_packets

# Rules for special networks not part of the Internet
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LO_IP -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LAN_IP1 -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LAN_IP2 -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $INET_IP -j ACCEPT

# Rules for incoming packets from anywhere.
$IPTABLES -A INPUT -p ALL -d $INET_IP -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A INPUT -p TCP -j tcp_packets
$IPTABLES -A INPUT -p UDP -j udp_packets
$IPTABLES -A INPUT -p ICMP -j icmp_packets

# Log weird packets that don't match the above.
$IPTABLES -A INPUT -m limit --limit 3/minute --limit-burst 3 -j LOG \
--log-level DEBUG --log-prefix "IPT INPUT packet died: "

#
#    FORWARD chain
#

# Bad TCP packets we don't want
$IPTABLES -A FORWARD -p tcp -j bad_tcp_packets

# Accept the packets we actually want to forward
$IPTABLES -A FORWARD -p tcp --dport 21 -i $LAN_IFACE1 -j ACCEPT
$IPTABLES -A FORWARD -p tcp --dport 21 -i $LAN_IFACE2 -j ACCEPT
$IPTABLES -A FORWARD -p tcp --dport 80 -i $LAN_IFACE1 -j ACCEPT
$IPTABLES -A FORWARD -p tcp --dport 110 -i $LAN_IFACE1 -j ACCEPT
$IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

# Log weird packets that don't match the above.
$IPTABLES -A FORWARD -m limit --limit 3/minute --limit-burst 3 -j LOG \
--log-level DEBUG --log-prefix "IPT FORWARD packet died: "

#
#    OUTPUT chain
#

# Bad TCP packets we don't want.
$IPTABLES -A OUTPUT -p tcp -j bad_tcp_packets

# Special OUTPUT rules to decide which IP's to allow.
$IPTABLES -A OUTPUT -p ALL -s $LO_IP -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -s $LAN_IP -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -s $INET_IP -j ACCEPT

# Log weird packets that don't match the above.
$IPTABLES -A OUTPUT -m limit --limit 3/minute --limit-burst 3 -j LOG \
--log-level DEBUG --log-prefix "IPT OUTPUT packet died: "

#
#    nat table
#

$IPTABLES -t nat -A PREROUTING -s $LAN_IP1 -p tcp -m tcp --dport 80   -j REDIRECT --to-ports 3128 
$IPTABLES -t nat -A PREROUTING -s $LAN_IP2 -p tcp -m tcp --dport 80   -j REDIRECT --to-ports 3128 
$IPTABLES -t nat -A PREROUTING -s $LAN_IP1 -p tcp -m tcp --dport 8080 -j REDIRECT --to-ports 3128 
$IPTABLES -t nat -A PREROUTING -s $LAN_IP2 -p tcp -m tcp --dport 8080 -j REDIRECT --to-ports 3128 
$IPTABLES -t nat -A PREROUTING -s $LAN_IP1 -p tcp -m tcp --dport 8081 -j REDIRECT --to-ports 3128 
$IPTABLES -t nat -A PREROUTING -s $LAN_IP2 -p tcp -m tcp --dport 8081 -j REDIRECT --to-ports 3128 
$IPTABLES -t nat -A PREROUTING -s $LAN_IP1 -p tcp -m tcp --dport 1080 -j REDIRECT --to-ports 3128 
$IPTABLES -t nat -A PREROUTING -s $LAN_IP2 -p tcp -m tcp --dport 1080 -j REDIRECT --to-ports 3128 
$IPTABLES -t nat -A PREROUTING -s $LAN_IP1 -p tcp -m tcp --dport 3128 -j REDIRECT --to-ports 3128 
$IPTABLES -t nat -A PREROUTING -s $LAN_IP2 -p tcp -m tcp --dport 3128 -j REDIRECT --to-ports 3128 


service iptables save