linux下防火墙配置

Chapter 1: Care and Feeding of iptables

Chapter 1 provides an introduction to packet filtering with iptables, including kernel build specifics and iptables administration. A default policy and network diagram is provided in this chapter and is referenced throughout the book. The Linux machine that runs the default policy functions as the firewall for a local area network (LAN), and attacks against this system are illustrated in later chapters.

Here is a that used throughout the book. This script is meant to be executed on the iptables firewall system in the following diagram, and you can modify this script to your liking for your own systems (the script is displayed below for reference as well).

 

 

#!/bin/sh
#
#############################################################################
#
# File: iptables.sh
#
# Purpose: To build a basic iptables policy with default log and drop rules.
# This script was written for the book "Linux Firewalls: Attack
# Detection and Response" published by No Starch Press.
#
# Copyright (C) 2006-2009 Michael Rash ([e-mail])
#
# License (GNU Public 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; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
# USA
#
#
#############################################################################
#
# $Id: index.html 2884 2010-08-23 01:52:49Z mbr $
#

IPTABLES=/sbin/iptables
IP6TABLES=/sbin/ip6tables
MODPROBE=/sbin/modprobe
INT_NET=192.168.10.0/24

### flush existing rules and set chain policy setting to DROP
echo "[+] Flushing existing iptables rules..."
$IPTABLES -F
$IPTABLES -F -t nat
$IPTABLES -X
$IPTABLES -P INPUT DROP
$IPTABLES -P OUTPUT DROP
$IPTABLES -P FORWARD DROP

### this policy does not handle IPv6 traffic except to drop it.
#
echo "[+] Disabling IPv6 traffic..."
$IP6TABLES -P INPUT DROP
$IP6TABLES -P OUTPUT DROP
$IP6TABLES -P FORWARD DROP

### load connection-tracking modules
#
$MODPROBE ip_conntrack
$MODPROBE iptable_nat
$MODPROBE ip_conntrack_ftp
$MODPROBE ip_nat_ftp

###### INPUT chain ######
#
echo "[+] Setting up INPUT chain..."

### state tracking rules
$IPTABLES -A INPUT -m state --state INVALID -j LOG --log-prefix "DROP INVALID " --log-ip-options --log-tcp-options
$IPTABLES -A INPUT -m state --state INVALID -j DROP
$IPTABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

### anti-spoofing rules
$IPTABLES -A INPUT -i eth1 -s ! $INT_NET -j LOG --log-prefix "SPOOFED PKT "
$IPTABLES -A INPUT -i eth1 -s ! $INT_NET -j DROP

### ACCEPT rules
$IPTABLES -A INPUT -i eth1 -p tcp -s $INT_NET --dport 22 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A INPUT -p icmp --icmp-type echo-request -j ACCEPT

### default INPUT LOG rule
$IPTABLES -A INPUT -i ! lo -j LOG --log-prefix "DROP " --log-ip-options --log-tcp-options

### make sure that loopback traffic is accepted
$IPTABLES -A INPUT -i lo -j ACCEPT

###### OUTPUT chain ######
#
echo "[+] Setting up OUTPUT chain..."

### state tracking rules
$IPTABLES -A OUTPUT -m state --state INVALID -j LOG --log-prefix "DROP INVALID " --log-ip-options --log-tcp-options
$IPTABLES -A OUTPUT -m state --state INVALID -j DROP
$IPTABLES -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

### ACCEPT rules for allowing connections out
$IPTABLES -A OUTPUT -p tcp --dport 21 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p tcp --dport 22 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p tcp --dport 25 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p tcp --dport 43 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p tcp --dport 80 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p tcp --dport 443 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p tcp --dport 4321 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p tcp --dport 53 -m state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p udp --dport 53 -m state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT

### default OUTPUT LOG rule
$IPTABLES -A OUTPUT -o ! lo -j LOG --log-prefix "DROP " --log-ip-options --log-tcp-options

### make sure that loopback traffic is accepted
$IPTABLES -A OUTPUT -o lo -j ACCEPT

###### FORWARD chain ######
#
echo "[+] Setting up FORWARD chain..."

### state tracking rules
$IPTABLES -A FORWARD -m state --state INVALID -j LOG --log-prefix "DROP INVALID " --log-ip-options --log-tcp-options
$IPTABLES -A FORWARD -m state --state INVALID -j DROP
$IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

### anti-spoofing rules
$IPTABLES -A FORWARD -i eth1 -s ! $INT_NET -j LOG --log-prefix "SPOOFED PKT "
$IPTABLES -A FORWARD -i eth1 -s ! $INT_NET -j DROP

### ACCEPT rules
$IPTABLES -A FORWARD -p tcp -i eth1 -s $INT_NET --dport 21 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -p tcp -i eth1 -s $INT_NET --dport 22 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -p tcp -i eth1 -s $INT_NET --dport 25 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -p tcp -i eth1 -s $INT_NET --dport 43 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -p tcp --dport 80 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -p tcp --dport 443 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -p tcp -i eth1 -s $INT_NET --dport 4321 --syn -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -p tcp --dport 53 -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -p udp --dport 53 -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -p icmp --icmp-type echo-request -j ACCEPT

### default LOG rule
$IPTABLES -A FORWARD -i ! lo -j LOG --log-prefix "DROP " --log-ip-options --log-tcp-options

###### NAT rules ######
#
echo "[+] Setting up NAT rules..."
$IPTABLES -t nat -A PREROUTING -p tcp --dport 80 -i eth0 -j DNAT --to 192.168.10.3:80
$IPTABLES -t nat -A PREROUTING -p tcp --dport 443 -i eth0 -j DNAT --to 192.168.10.3:443
$IPTABLES -t nat -A PREROUTING -p udp --dport 53 -i eth0 -j DNAT --to 192.168.10.4:53
$IPTABLES -t nat -A POSTROUTING -s $INT_NET -o eth0 -j MASQUERADE

###### forwarding ######
#
echo "[+] Enabling IP forwarding..."
echo 1 > /proc/sys/net/ipv4/ip_forward

exit
### EOF ###