iptables例子1

#!/bin/bash
#
# Script name: ipt_server
# A simple script for firewall, used in Linux (kernel 2.4.x),
# with certain services provided to outside world.
#
# Copyleft 2002 by netman ().
#
# Redistribution of this file is permitted under the terms of
# the GNU General Public License (GPL).
#
# Date: 2002/07/03
# Version: 1.4

PATH=/sbin:/usr/sbin:/bin:/usr/bin
RC_SQUID=/etc/rc.d/init.d/squid
EXT_IF=ppp0
INT_IF=eth0
TRUSTED_TCP_PORT="20 21 22 25 53 80 110 113 143 220 443 465 993 995"
TRUSTED_UDP_PORT="53"
ALLOWED_ICMP="0 3 3/4 4 11 12 14 16 18"

#
# ------------- ensure iptables ----------
which iptables &>/dev/null || {
 echo
 echo "$(basename $0): iptables program is not found."
 echo " Please install the program first."
 echo
 exit 1
}

# ------------- disable ipchains ----------
lsmod | grep ipchains &>/dev/null && {
 echo "Disabling ipchains..."
 rmmod ipchains
}

# ------------- modules -----------
echo "Loading modules..."
modprobe ip_tables &>/dev/null || {
    echo -n "$(basename $0): loading ip_tables module failure."
    echo " Please Fix it!"
    exit 3
}
for file in /lib/modules/`uname -r`/kernel/net/ipv4/netfilter/ip_conntrack_*.o
do
    module=$(basename $file)
    modprobe ${module%.*} &>/dev/null
done
for file in /lib/modules/`uname -r`/kernel/net/ipv4/netfilter/ip_nat_*.o
do
    module=$(basename $file)
    modprobe ${module%.*} &>/dev/null
done

# ------------- ipforwarding -----------
echo "Turning on IP forwarding..."
echo "1" > /proc/sys/net/ipv4/ip_forward

# ------------- anti spoofing -----------
echo "Turning on anti-spoofing..."
for file in /proc/sys/net/ipv4/conf/*/rp_filter; do
 echo "1" > $file
done

# ------------- flushing ----------
echo "Cleaning up..."
iptables -F -t filter
iptables -X -t filter
iptables -Z -t filter
iptables -F -t nat
iptables -X -t nat
iptables -Z -t nat

# ------------- policies -------------
echo "Setting up policies to ACCEPT..."
iptables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -t nat -P PREROUTING ACCEPT
iptables -t nat -P POSTROUTING ACCEPT
iptables -t nat -P OUTPUT ACCEPT

# ------------- ICMP -------------
echo "Creating icmpfilter chain..."
iptables -N icmpfilter
for TYPE in $ALLOWED_ICMP; do
    iptables -A icmpfilter -i $EXT_IF -p icmp --icmp-type $TYPE -j ACCEPT
done

# ------------- services ------------
echo "Creating services chain...."
iptables -N services
for PORT in $TRUSTED_TCP_PORT; do
    iptables -A services -i $EXT_IF -p tcp --dport $PORT -j ACCEPT
done
for PORT in $TRUSTED_UDP_PORT; do
    iptables -A services -i $EXT_IF -p udp --dport $PORT -j ACCEPT
done

# ------------- block -------------
echo "Creating block chain..."
iptables -N block
iptables -A block -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A block -m state --state NEW -i ! $EXT_IF -j ACCEPT
iptables -A block -j DROP

# ------------- filter -------------
echo "Filtering packets..."
iptables -A INPUT -j icmpfilter
iptables -A INPUT -j services
iptables -A INPUT -j block
iptables -A FORWARD -j icmpfilter
iptables -A FORWARD -j block

# ------------- masq -------------
echo "Masquerading internel network..."
iptables -t nat -A POSTROUTING -o $EXT_IF -j MASQUERADE

# ------------- tproxy -------------
$RC_SQUID status | grep pid &>/dev/null && {
 echo "Enabling transparent proxy...."
 INT_IP=$(ifconfig | grep $INT_IF -A 1 | \
  awk '/inet/ {print $2}' | sed -e s/addr\://)
 if [ -z "$INT_IP" ]; then
  echo
  echo "$(basename $0): there is no IP found on $INT_IF."
  echo " Please make sure $INT_IF is setup properly."
  echo
  exit 3
 fi
 iptables -t nat -A PREROUTING -d $INT_IP -i $INT_IF \
  -p tcp -m tcp --dport 80 -j ACCEPT
 iptables -t nat -A PREROUTING -i $INT_IF -p tcp -m tcp \
  --dport 80 -j REDIRECT --to-ports 3128
}
exit 0
## EOS