# be swamped as well. This rule will block them from getting logged.
#
#$IPTABLES -A udp_packets -p UDP -i $INET_IFACE -d 255.255.255.255 \
#–destination-port 67:68 -j DROP
#
# 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 $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
#
# 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
$IPTABLES -A INPUT -p ICMP -j icmp_packets
#
# If you have a Microsoft Network on the outside of your firewall, you may
# also get flooded by Multicasts. We drop them so we do not get flooded by
# logs
#
#$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
#
# Accept the packets we actually want to forward
#
$IPTABLES -A FORWARD -p tcp –dport 21 -i $LAN_IFACE -j ACCEPT
$IPTABLES -A FORWARD -p tcp –dport 80 -i $LAN_IFACE -j ACCEPT
$IPTABLES -A FORWARD -p tcp –dport 110 -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
#
#
# 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
#
I.4. Пример rc.DHCP.firewall
#!/bin/sh
#
# rc.firewall – DHCP 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_IFACE="eth0"
#
# 1.1.1 DHCP
#
#
# Information pertaining to DHCP over the Internet, if needed.
#
# Set DHCP variable to no if you don't get IP from DHCP. If you get DHCP
# over the Internet set this variable to yes, and set up the proper IP
# address for the DHCP server in the DHCP_SERVER variable.
#
DHCP="no"
DHCP_SERVER="195.22.90.65"
#
# 1.1.2 PPPoE
#
# Configuration options pertaining to PPPoE.
#
# If you have problem with your PPPoE connection, such as large mails not
# getting through while small mail get through properly etc, you may set
# this option to «yes» which may fix the problem. This option will set a
# rule in the PREROUTING chain of the mangle table which will clamp
# (resize) all routed packets to PMTU (Path Maximum Transmit Unit).
#
# Note that it is better to set this up in the PPPoE package itself, since
# the PPPoE configuration option will give less overhead.
#
PPPOE_PMTU="no"
#
# 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"
#
# 1.6 Other Configuration.
#
###########################################################################
#
# 2. Module loading.
#
#
# Needed to initially load modules
#
/sbin/depmod -a
#
# 2.1 Required modules
#
/sbin/modprobe ip_conntrack
/sbin/modprobe ip_tables
/sbin/modprobe iptable_filter
/sbin/modprobe iptable_mangle
/sbin/modprobe iptable_nat
/sbin/modprobe ipt_LOG
/sbin/modprobe ipt_limit
/sbin/modprobe ipt_MASQUERADE
#
# 2.2 Non-Required modules
#
#/sbin/modprobe ipt_owner
#/sbin/modprobe ipt_REJECT
#/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 tcp_packets
$IPTABLES -N udp_packets
$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
#
# TCP rules
#
$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 80 -j allowed
$IPTABLES -A tcp_packets -p TCP -s 0/0 –dport 113 -j allowed
#
# UDP ports
#
$IPTABLES -A udp_packets -p UDP -s 0/0 –source-port 53 -j ACCEPT
if [ $DHCP == «yes» ] ; then
$IPTABLES -A udp_packets -p UDP -s $DHCP_SERVER –sport 67 \
–dport 68 -j ACCEPT
fi
#$IPTABLES -A udp_packets -p UDP -s 0/0 –source-port 53 -j ACCEPT