Oskar Andreasson - Iptables Tutorial 1.1.19

$IPTABLES -A allowed -p TCP -m state –state ESTABLISHED,RELATED -j ACCEPT

$IPTABLES -A allowed -p TCP -j DROP

#

# ICMP rules

#

# Changed rules totally

$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

#

# Packets from the Internet to this box

#

$IPTABLES -A INPUT -p ICMP -i $INET_IFACE -j icmp_packets

#

# Packets from LAN, DMZ or LOCALHOST

#

#

# From DMZ Interface to DMZ firewall IP

#

$IPTABLES -A INPUT -p ALL -i $DMZ_IFACE -d $DMZ_IP -j ACCEPT

#

# From LAN Interface to LAN firewall IP

#

$IPTABLES -A INPUT -p ALL -i $LAN_IFACE -d $LAN_IP -j ACCEPT

#

# From Localhost interface to Localhost IP's

#

$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

#

# Special rule for DHCP requests from LAN, which are not caught properly

# otherwise.

#

$IPTABLES -A INPUT -p UDP -i $LAN_IFACE –dport 67 –sport 68 -j ACCEPT

#

# All established and related packets incoming from the internet to the

# firewall

#

$IPTABLES -A INPUT -p ALL -d $INET_IP -m state –state ESTABLISHED,RELATED \

–j ACCEPT

#

# In Microsoft Networks you will be swamped by broadcasts. These lines

# will prevent them from showing up in the logs.

#

#$IPTABLES -A INPUT -p UDP -i $INET_IFACE -d $INET_BROADCAST \

#–destination-port 135:139 -j DROP

#

# If we get DHCP requests from the Outside of our network, our logs will

# be swamped as well. This rule will block them from getting logged.

#

#$IPTABLES -A INPUT -p UDP -i $INET_IFACE -d 255.255.255.255 \

#–destination-port 67:68 -j DROP

#

# If you have a Microsoft Network on the outside of your firewall, you may

# also get flooded by Multicasts. We drop them so we do not get flooded by

# logs

#

#$IPTABLES -A INPUT -i $INET_IFACE -d 224.0.0.0/8 -j DROP

#

# 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

#

# DMZ section

#

# General rules

#

$IPTABLES -A FORWARD -i $DMZ_IFACE -o $INET_IFACE -j ACCEPT

$IPTABLES -A FORWARD -i $INET_IFACE -o $DMZ_IFACE -m state \

–state ESTABLISHED,RELATED -j ACCEPT

$IPTABLES -A FORWARD -i $LAN_IFACE -o $DMZ_IFACE -j ACCEPT

$IPTABLES -A FORWARD -i $DMZ_IFACE -o $LAN_IFACE -m state \

–state ESTABLISHED,RELATED -j ACCEPT

#

# HTTP server

#

$IPTABLES -A FORWARD -p TCP -i $INET_IFACE -o $DMZ_IFACE -d $DMZ_HTTP_IP \

–dport 80 -j allowed

$IPTABLES -A FORWARD -p ICMP -i $INET_IFACE -o $DMZ_IFACE -d $DMZ_HTTP_IP \

–j icmp_packets

#

# DNS server

#

$IPTABLES -A FORWARD -p TCP -i $INET_IFACE -o $DMZ_IFACE -d $DMZ_DNS_IP \

–dport 53 -j allowed

$IPTABLES -A FORWARD -p UDP -i $INET_IFACE -o $DMZ_IFACE -d $DMZ_DNS_IP \

–dport 53 -j ACCEPT

$IPTABLES -A FORWARD -p ICMP -i $INET_IFACE -o $DMZ_IFACE -d $DMZ_DNS_IP \

–j icmp_packets

#

# LAN section

#

$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

#

# 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

#

#

# 4.2.1 Set policies

#

#

# 4.2.2 Create user specified chains

#

#

# 4.2.3 Create content in user specified chains

#

#

# 4.2.4 PREROUTING chain

#

$IPTABLES -t nat -A PREROUTING -p TCP -i $INET_IFACE -d $HTTP_IP –dport 80 \

–j DNAT –to-destination $DMZ_HTTP_IP

$IPTABLES -t nat -A PREROUTING -p TCP -i $INET_IFACE -d $DNS_IP –dport 53 \

–j DNAT –to-destination $DMZ_DNS_IP

$IPTABLES -t nat -A PREROUTING -p UDP -i $INET_IFACE -d $DNS_IP –dport 53 \

–j DNAT –to-destination $DMZ_DNS_IP

#

# 4.2.5 POSTROUTING chain

#

#

# Enable simple IP Forwarding and Network Address Translation

#

$IPTABLES -t nat -A POSTROUTING -o $INET_IFACE -j SNAT –to-source $INET_IP

#

# 4.2.6 OUTPUT chain

#

######

# 4.3 mangle table

#

#

# 4.3.1 Set policies

#

#

# 4.3.2 Create user specified chains

#

#

# 4.3.3 Create content in user specified chains

#

#

# 4.3.4 PREROUTING chain

#

#

# 4.3.5 INPUT chain

#

#

# 4.3.6 FORWARD chain

#

#

# 4.3.7 OUTPUT chain

#

#

# 4.3.8 POSTROUTING chain

#

#!/bin/sh

#

# rc.firewall – UTIN Firewall script for Linux 2.4.x and iptables

#

# Copyright (C) 2001 Oskar Andreasson

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; version 2 of the License.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program or from the site that you downloaded it

# from; if not, write to the Free Software Foundation, Inc., 59 Temple

# Place, Suite 330, Boston, MA 02111-1307 USA

#

###########################################################################

#

# 1. Configuration options.

#

#

# 1.1 Internet Configuration.

#

INET_IP="194.236.50.155"

INET_IFACE="eth0"

INET_BROADCAST="194.236.50.255"

#

# 1.1.1 DHCP

#

#

# 1.1.2 PPPoE

#

#

# 1.2 Local Area Network configuration.

#

# your LAN's IP range and localhost IP. /24 means to only use the first 24

# bits of the 32 bit IP address. the same as netmask 255.255.255.0

#

LAN_IP="192.168.0.2"

LAN_IP_RANGE="192.168.0.0/16"

LAN_IFACE="eth1"

#

# 1.3 DMZ Configuration.

#

#

# 1.4 Localhost Configuration.

#

LO_IFACE="lo"

LO_IP="127.0.0.1"

#

# 1.5 IPTables Configuration.

#

IPTABLES="/usr/sbin/iptables"