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FreeBSD ipfw 防火墙基础指南

一、内核配置
/usr/src/sys/i386/conf/HQ_SuperServer
代码:
options   IPFIREWALL
options   IPFIREWALL_DEFAULT_TO_ACCEPT
options   IPDIVERT     # IPDIVERT enables the divert IP sockets, used by ""ipfw divert""
options   IPFIREWALL_VERBOSE
options   IPFIREWALL_VERBOSE_LIM_blank>IT=30
#options  IPFILTER     #ipfilter support
#options  IPFILTER_LOG   #ipfilter logging
# traffic shaper, bandwidth manager and delay emulator
options   DUMMYNET     # enables the "dummynet" bandwidth limiter. You need IPFIREWALL as well.
# Statically Link in accept filters for a web server on this box
options   ACCEPT_FILTER_DATA
options   ACCEPT_FILTER_HTTP
options  ICMP_BANDLIM   # D.O.S. protection
options   IPSTEALTH     #To hide firewall from traceroute
options   TCP_DROP_SYNFIN   #To hide from nmap OS fingerprint, remove if create web server


二、rc.conf配置
/etc/rc.conf
代码:
firewall_enable="YES"
firewall_logging="YES"
firewall_script="/etc/rc.firewall"
firewall_quiet="NO"               #change to YES once happy with rules
firewall_logging_enable="YES"
#extra firewalling options
log_in_vain="YES"
#This option prevents something known as OS fingerprinting, must have TCP_DROP_SYNFIN compiled into kernel to use
tcp_drop_synfin="NO"  #change to NO if create webserver
tcp_restrict_rst="YES"
icmp_drop_redirect="YES"

三、ipfw使用
代码:
ipfw add allow tcp from  to  in recv 

添加和除去规则例子:
代码:
$ sudo ipfw add deny tcp from 61.49.203.115 to 61.49.203.114 22 in recv fxp0
$ sudo ipfw -t list
$ sudo ipfw delete 00100

禁止icmp
代码:
$ sudo ipfw add deny icmp from any to any in recv fxp0

显示rules
代码:
$ sudo ipfw show

按照序号显示规则
代码:
$ sudo ipfw -t list

列出信息包的数目,和与它们相对应的规则匹配
代码:
$ sudo ipfw -a list

四、/etc/ipfw.rules规则文件
代码:
allow 00010 udp from any to me 67 in via $iif
allow 00020 udp from me 68 to any out via $iif

五、/etc/rc.firewall脚本
代码:
# mv /etc/rc.firewall /etc/rc.firewall.orig
# touch /etc/rc.firewall
# chmod u=+rx,og=-rwx /etc/ipfw.rules

/etc/rc.firewall
代码:
#!/bin/sh
# This will flush the existing rules - sudo ipfw -f flush
# You can execute this script without dropping existing connections/states
fwcmd="/sbin/ipfw -q"
extif="fxp0"
myip="10.1.8.114"
mybcast="10.1.8.119"
mynetwork="10.1.8.112/29"
dns_server="10.1.8.1"
# Reset all rules in case script run multiple times
$ -f flush
$ add 200 check-state
# Block RFC 1918 networks - the , syntax only works in ipfw2
$ add 210 deny all from 0.0.0.0/7,1.0.0.0/8,2.0.0.0/8,5.0.0.0/8,10.0.0.0/8,23.0.0.0/8,
27.0.0.0/8,31.0.0.0/8,67.0.0.0/8,68.0.0.0/6,72.0.0.0/5,80.0.0.0/4,96.0.0.0/3,127.0.0.0/8,
128.0.0.0/16,128.66.0.0/16,169.254.0.0/16,172.16.0.0/12,191.255.0.0/16,192.0.0.0/16,
192.168.0.0/16,197.0.0.0/8,201.0.0.0/8,204.152.64.0/23,224.0.0.0/3,240.0.0.0/8 to any
# Allow all via loopback to loopback
$ add 220 allow all from any to any via lo0
# Allow from me to anywhere
$ add 240 allow tcp from $ to any setup keep-state
$ add 260 allow udp from $ to any keep-state
$ add 280 allow icmp from $ to any
# Allow local LAN to connect to us
$ add 300 allow ip from $ to $
# Allow INCOMING SSH,SMTP,HTTP from anywhere on the internet
$ add 320 allow log tcp from any to $ 22,25,80 in keep-state setup
# Disable icmp
$ add 340 allow icmp from any to any icmptype 0,3,11
# Block all other traffic and log in
$ add 360 deny log all from any to any
# End of /etc/rc.firewall


六、 ipfw日志纪录配置

/etc/syslog.conf
代码:
!ipfw    
*.*                    /var/log/ipfw.log

代码:
$ sudo touch /var/log/ipfw.log
$ sudo killall -HUP syslogd

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