rc.firewall脚本代码,即第七章的例子
#!/bin/sh # # rc.firewall - Initial SIMPLE IP 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. # #连接到internet网上的IP，设备 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 # 连接内部网络的IP，设备 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. # 定议变量IPTABLES IPTABLES="/usr/sbin/iptables" # # 1.6 Other Configuration. # ########################################################################### # # 2. Module loading. # # # Needed to initially load modules # 初始化 /sbin/depmod -a # # 2.1 Required modules # 加载必需的模块 /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 # 打开转发功能 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 # 缺省策略的设置,用来处理那些在相应的链里没被规则匹配的包 $IPTABLES -P INPUT DROP $IPTABLES -P OUTPUT DROP $IPTABLES -P FORWARD DROP # # 4.1.2 Create userspecified chains # 创建用户自定义链 # # Create chain for bad tcp packets # $IPTABLES -N bad_tcp_packets # # Create separate chains for ICMP, TCP and UDP to traverse # 分别为tcp,udp,icmp建立新链 $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 # 这条链包含的规则检查进入包（incoming packet）的包头是否不正常或有没有其他问题。 # 没有设置SYN位但又是NEW状态的TCP包，还有那些设置了SYN/ACK但也被认为是NEW状态的TCP包。 # 这条链可以用来检查所有可能的不一致的东西 $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 # 检查这个包是否是SYN包，如果是，它很可能是新连接的第一个包，则接受 # 如果不是，那就检查包是否来自某个ESTABLISHED或RELATED状态的连接，是的话，就接受 # 最后一条规则将DROP所有其他的包, 目前没有什么TCP/ IP程序会使用SYN包以外的包来打开一个TCP连接。 # 因此，我们要把这样的包DROP掉，一般来说它们是端口扫描用的 $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 # 充许所有地址访问21，22，80，113端口，并交给allowed链处理。 $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 $IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 113 -j allowed # # UDP ports # 允许访问UDP的2047,它是某些实时的多媒体应用程序使用的。比如speak freely # 端口4000相应的协议是ICQ协议，由ICQ使用 #$IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 53 -j ACCEPT #$IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 123 -j ACCEPT $IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 2074 -j ACCEPT $IPTABLES -A udp_packets -p UDP -s 0/0 --destination-port 4000 -j ACCEPT # # In Microsoft Networks you will be swamped by broadcasts. These lines # will prevent them from showing up in the logs. # 阻塞目的端口是135到139的广播包 # 阻塞所有位于外网的那些Microsoft Network产生的广播包 #$IPTABLES -A udp_packets -p UDP -i $INET_IFACE -d $INET_BROADCAST #--destination-port 135:139 -j DROP # # If we get DHCP requests from the Outside of our network, our logs will # be swamped as well. This rule will block them from getting logged. # 阻止外网的DHCP查询 #$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. # 把所有的tcp包送到bad_tcp_packets链，由其中的规则进行检查进入的tcp包的形态 # 是否是不正常的或我们不想要的 $IPTABLES -A INPUT -p tcp -j bad_tcp_packets # # Rules for special networks not part of the Internet # 处理被信任的网络的数据传输,“连接内网的网卡”的流量,所有来自和发往loopback的流量 # 把处理LAN的流量的规则放在防火墙的上部，因为我们的局域网产生的流量要远远多于Internet连接。 # 这样，规则会更有效率，防火墙就能以较小的开销去匹配包 $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 # # Special rule for DHCP requests from LAN, which are not caught properly # otherwise. # $IPTABLES -A INPUT -p UDP -i $LAN_IFACE --dport 67 --sport 68 -j ACCEPT # # Rules for incoming packets from the internet. # 这是个处理状态的规则，允许所有处于状态ESTABLISHED或RELATED且发往 Internet接口的包进入 # 把从$INET_IFACE进入的所有TCP包发往tcp_packets链 $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 $INET_IFACE -j icmp_packets # # If you have a Microsoft Network on the outside of your firewall, you may # also get flooded by Multicasts. We drop them so we do not get flooded by # logs # Microsoft的客户机有个坏习惯，就是向地址224.0.0.0/8发送大量的多播包。 # 因此我们要有这条规则来阻塞那些包，以免我们的日志被它们填满 #$IPTABLES -A INPUT -i $INET_IFACE -d 224.0.0.0/8 -j DROP # # Log weird packets that don't match the above. # 每分钟最多记录3个包，对所有的记录设置了前缀。 $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 # $IPTABLES -A FORWARD -p tcp -j bad_tcp_packets # # Accept the packets we actually want to forward # 第一个允许所有来自$LAN_IFACE的数据通过 # 第二个允许ESTABLISHED和RELATED状态的包能通过防火墙。 # 就是所有对我们的内网发出的连接的回应都可以返回局域网 # $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. # 记录没被上面任何规则匹配的包 $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. # 把所有出去TCP包发到bad_tcp_packets链检查 $IPTABLES -A OUTPUT -p tcp -j bad_tcp_packets # # Special OUTPUT rules to decide which IP's to allow. # 允许所有从防火墙的IP（包括 LOCALHOST_IP，$LAN_IP或$STATIC_IP ）出发的数据 $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 # 构造网络地址转换 $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 #