firewall

#!/bin/sh 
#
# 1.1 Internet Configuration.
#

INET_IP="188.127.232.218"
INET_IFACE="eth1"
INET_BROADCAST="188.127.232.255"

#
# 1.2 Local Area Network configuration.
#

LAN_IP="10.4.2.4"
LAN_IP_RANGE="10.0.0.0/8"
LAN_IFACE="eth0"


LO_IFACE="lo"
LO_IP="127.0.0.1"

VPN_IFACE='tun0'
VPN_IP='10.197.0.1'
VPN_IP_RANGE='10.197.0.0/16'
VPN_REMOTE_RENGE='172.16.0.0/12'
#
# 1.5 IPTables Configuration.
#

IPTABLES="/sbin/iptables"

######
# 4.1 Filter table
#

#
# 4.1.1 Set policies
#

$IPTABLES -P INPUT DROP
$IPTABLES -P OUTPUT DROP
$IPTABLES -P FORWARD DROP

#
# 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 allowed TCP incoming connections
#

$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 12456 -j allowed

#
# UDP ports
#
$IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 12457 -j ACCEPT
$IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 1194 -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

#
# 4.1.4 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 $LAN_IFACE -s $LAN_IP_RANGE -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LO_IP -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LAN_IP -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $INET_IP -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $VPN_IFACE -s $VPN_IP_RANGE -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $VPN_IP_RANGE -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $VPN_IFACE -s $VPN_REMOTE_RENGE -j ACCEPT
#
# Rules for incoming packets from the internet.
#

$IPTABLES -A INPUT -p ALL -d $INET_IP -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A INPUT -p TCP -i $INET_IFACE -j tcp_packets
$IPTABLES -A INPUT -p UDP -i $INET_IFACE -j udp_packets
$IPTABLES -A INPUT -p ICMP -i $INET_IFACE -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: "

#
# 4.1.5 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 -i $VPN_IFACE -j ACCEPT
$IPTABLES -A FORWARD -i $LAN_IFACE -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: "

#
# 4.1.6 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
$IPTABLES -A OUTPUT -p ALL -s $VPN_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: "

######
# 4.2 nat table
#


#
# Enable simple IP Forwarding and Network Address Translation
#

$IPTABLES -t nat -A POSTROUTING -o $LAN_IFACE -j SNAT --to-source $LAN_IP
#
# 4.2.6 OUTPUT chain
#

######
# 4.3 mangle table
#

###########################################################################
#
# 3. /proc set up.
#

#
# 3.1 Required proc configuration
#

#echo "1" > /proc/sys/net/ipv4/ip_forward