#!/bin/sh

#

# rc.firewall - Initial SIMPLE 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.

#定义网络参数变量

#

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"

#

# 1.6 Other Configuration.

#

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

#

# 2. Module loading.

#加载模块

#

#

# 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.

#设置/proc参数开启转发功能，主要用于nat

#

#

# 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

#开始配置具体的规则.

#

######

# 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

#作者的总体思路是先写好自定义的链，然后再后续的系统预定义链中调用，类似函数的概

#念

#

# 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

#拒绝或者记录不正常的数据包

#

$IPTABLES -A bad_tcp_packets -p tcp --tcp-flags SYN,ACK SYN,ACK

-m state --state NEW -j REJECT --reject-with tcp-reset

#拒绝带有SYN和ACK标记的状态为NEW的包并返回错误信息

$IPTABLES -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j LOG

--log-prefix "New not syn:"

#不是SYN标记但是状态时NEW的数据包并记录日志

$IPTABLES -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j DROP

#拒绝不是SYN标记但是状态时NEW的数据包并记录日志

#

# allowed chain

#允许特定的数据包

#

$IPTABLES -A allowed -p TCP --syn -j ACCEPT

#允许带有SYN标记的数据包

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

#允许状态为ESTABLISH和RELATED的数据包

$IPTABLES -A allowed -p TCP -j DROP

#拒绝其他所有的数据包

#

# TCP rules

#

$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 21 -j allowed

#允许访问ftp服务

$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 22 -j allowed

#允许访问ssh服务

$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 80 -j allowed

#允许访问www服务

$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 113 -j allowed

#允许访问IRC服务

#

# UDP ports

#

#$IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 53 -j ACCEPT

#允许DNS服务

#$IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 123 -j ACCEPT

#允许ntp服务

$IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 2074 -j ACCEPT

#允许多媒体服务

$IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 4000 -j ACCEPT

#允许ICQ服务

#

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

# will prevent them from showing up in the logs.

#

#$IPTABLES -A udp_packets -p UDP -i $INET_IFACE -d $INET_BROADCAST

#--destination-port 135:139 -j DROP

#拒绝微软的netbios的广播服务

#

# 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 udp_packets -p UDP -i $INET_IFACE -d 255.255.255.255

#--destination-port 67:68 -j DROP

#拒绝DHCP服务

#

# ICMP rules

#

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

#允许8类ICMP服务

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

#允许11类ICMP服务

#

# 4.1.4 INPUT chain

#

#

# Bad TCP packets we don't want.

#

$IPTABLES -A INPUT -p tcp -j bad_tcp_packets

#检查是否是坏包

#

# Rules for special networks not part of the Internet

#

$IPTABLES -A INPUT -p ALL -i $LAN_IFACE -s $LAN_IP_RANGE -j ACCEPT

#来自内部网络的包一律允许通过

$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LO_IP -j ACCEPT

#来自本地的包一律通过

$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

#允许DHCP服务

#

# Rules for incoming packets from the internet.

#

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

-j ACCEPT

#允许外部过来的响应本地请求或者和本地已有连接有关系的包

$IPTABLES -A INPUT -p TCP -i $INET_IFACE -j tcp_packets

#TCP包由对应链处理

$IPTABLES -A INPUT -p UDP -i $INET_IFACE -j udp_packets

#UDP包由对应链处理

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

#ICMP包由对应链处理

#

# 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

#拒绝组播包

#

# 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: "

#如果包与上述规则均不匹配则写入日志

#

# 4.1.5 FORWARD chain

#

#

# Bad TCP packets we don't want

#

$IPTABLES -A FORWARD -p tcp -j bad_tcp_packets

#先检查是否是坏包

#

# Accept the packets we actually want to forward

#

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

#允许由本地发来的包被转发

$IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

#允许ESTABLISHED,RELATED状态的包转发

#

# 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: "

#如果包与上述规则均不匹配则写入日志

#

# 4.1.6 OUTPUT chain

#

#

# Bad TCP packets we don't want.

#

$IPTABLES -A OUTPUT -p tcp -j bad_tcp_packets

#先检查是否是坏包

#

# Special OUTPUT rules to decide which IP's to allow.

#

$IPTABLES -A OUTPUT -p ALL -s $LO_IP -j ACCEPT

#允许所有包通过

$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: "

#如果包与上述规则均不匹配则写入日志

######

# 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

#对所有沿外网口出去的包执行SNAT

#

# 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

#

##本脚本来自http:

#www.faqs.org/docs/iptables/index.html