#!/bin/sh # # rc.DMZ.firewall - DMZ IP Firewall script for Linux 2.4.x and iptables # # Copyright (C) 2001 Oskar Andreasson <bluefluxATkoffeinDOTnet> # # 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="194.236.50.152" HTTP_IP="194.236.50.153" DNS_IP="194.236.50.154" INET_IFACE="eth0" # # 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="192.168.0.1" LAN_IFACE="eth1" # # 1.3 DMZ Configuration. # DMZ_HTTP_IP="192.168.1.2" DMZ_DNS_IP="192.168.1.3" DMZ_IP="192.168.1.1" DMZ_IFACE="eth2" # # 1.4 Localhost Configuration. # LO_IFACE="lo" LO_IP="127.0.0.1" # # 1.5 IPTables Configuration. # IPTABLES="/usr/sbin/iptables" # # 1.6 Other Configuration. # ########################################################################### # # 2. Module loading. # # # Needed to initially load modules # /sbin/depmod -a # # 2.1 Required modules # /sbin/modprobe ip_tables /sbin/modprobe ip_conntrack /sbin/modprobe iptable_filter /sbin/modprobe iptable_mangle /sbin/modprobe iptable_nat /sbin/modprobe ipt_LOG /sbin/modprobe ipt_limit /sbin/modprobe ipt_state # # 2.2 Non-Required modules # #/sbin/modprobe ipt_owner #/sbin/modprobe ipt_REJECT #/sbin/modprobe ipt_MASQUERADE #/sbin/modprobe ip_conntrack_ftp #/sbin/modprobe ip_conntrack_irc #/sbin/modprobe ip_nat_ftp #/sbin/modprobe ip_nat_irc ########################################################################### # # 3. /proc set up. # # # 3.1 Required proc configuration # echo "1" > /proc/sys/net/ipv4/ip_forward # # 3.2 Non-Required proc configuration # #echo "1" > /proc/sys/net/ipv4/conf/all/rp_filter #echo "1" > /proc/sys/net/ipv4/conf/all/proxy_arp #echo "1" > /proc/sys/net/ipv4/ip_dynaddr ########################################################################### # # 4. rules set up. # ###### # 4.1 Filter table # # # 4.1.1 Set policies # $IPTABLES -P INPUT DROP $IPTABLES -P OUTPUT DROP $IPTABLES -P FORWARD DROP # # 4.1.2 Create userspecified chains # # # 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 icmp_packets # # 4.1.3 Create content in userspecified chains # # # 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 # # 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 #