[linux-users:97093] NIC３枚でDMZをiｐtablesで

["成瀬 慶純" <louis _at_ xxxxxxxxxxxxxx>]

こんにちは、成瀬です。

RedHatLinux8.0でiptablesにてNIC３枚使いFirewallの
構築をしております。

［構成］

       ____|____ 専用線
    　|router|
       ~~~|~~
           |　　　　　　グローバル（aaa.bbb.ccc.ddd/27）
  ---┬┴--------
        |
eth0  |
     ___|____　eth1　　DMZ（192.168.255.0/24）
     | FW |--------┬-------------
     ~~|~~~　　　　  ___|___
        |               |www|  ←192.168.255.102（aaa.bbb.ccc.170)
  eth2|               ~~~~~
----┴--------------内部ネットワーク（192.168.2.0/24）



この構成で、DMZにあるwwwサーバがインターネット側からは
参照できるのですが、ローカル側からは、DMZのローカルアドレス
（192.168.255.102）でしかアクセスできません。
ローカルからaaa.bbb.ccc.170のアドレスでアクセス出来ません。

下記が現在設定している内容です。

#!/bin/sh
#
LAN_IP="192.168.0.1"
LAN_BCAST_ADRESS="192.168.0.255"
LAN_IFACE="eth2"

INET_IP="aaa.bbb.ccc.ddd"
INET_IFACE="eth0"

DMZ_IP="192.168.255.1"
DMZ_IFACE="eth1"

HTTP_IP="aaa.bbb.ccc.169"

DMZ_HTTP_IP="192.168.255.102"

LO_IP="127.0.0.1"
LO_IFACE="lo"

IPTABLES="/sbin/iptables"

###########################################
#
# Load all required IPTables modules
#

#
# Needed to initially load modules
#

/sbin/depmod -a

#
# Adds some iptables targets like LOG, REJECT and MASQUARADE.
#

/sbin/modprobe ipt_LOG
/sbin/modprobe ipt_MASQUERADE

#
# Support for connection tracking of FTP and IRC.
#
#/sbin/insmod ip_nat_irc
#/sbin/modprobe ip_conntrack_irc
/sbin/insmod ip_nat_ftp
/sbin/insmod ip_conntrack_ftp

#CRITICAL:  Enable IP forwarding since it is disabled by default.
#

echo "1" > /proc/sys/net/ipv4/ip_forward

#
# Dynamic IP users:
#
#echo "1" > /proc/sys/net/ipv4/ip_dynaddr

###########################################
#
# Chain Policies gets set up before any bad packets gets through
#

$IPTABLES -P INPUT DROP
$IPTABLES -P OUTPUT DROP
$IPTABLES -P FORWARD DROP

#
# the allowed chain for TCP connections, utilized in the FORWARD chain
#

$IPTABLES -N allowed
$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

#
# ICMP rules, utilized in the FORWARD chain
#


$IPTABLES -N icmp_packets

# Changed rules totally
$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

#
# bad_tcp_packets chain
#
# Take care of bad TCP packets that we don't want.
#

$IPTABLES -N bad_tcp_packets
$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

#
# Do some checks for obviously spoofed IP's
#

$IPTABLES -A bad_tcp_packets -i $INET_IFACE -s 192.168.0.0/16 -j DROP
$IPTABLES -A bad_tcp_packets -i $INET_IFACE -s 10.0.0.0/8 -j DROP
$IPTABLES -A bad_tcp_packets -i $INET_IFACE -s 172.16.0.0/12 -j DROP

###########################################
# POSTROUTING chain in the nat table
#
# Enable IP SNAT for all internal networks trying to get out on the Internet
#

$IPTABLES -t nat -A POSTROUTING -o $INET_IFACE -j SNAT --to-source $INET_IP



###########################################
# PREROUTING chain in the nat table
#
# Enable IP Destination NAT for DMZ zone
#

$IPTABLES -t nat -A PREROUTING -p TCP -i $INET_IFACE -d $HTTP_IP --dport 80 -j DNAT --to-destination $DMZ_HTTP_IP
$IPTABLES -t nat -A PREROUTING -p TCP -i $INET_IFACE -d $HTTP_IP --dport 443 -j DNAT --to-destination $DMZ_HTTP_IP

###########################################
#
# FORWARD chain
#
#
# Bad TCP packets we don't want
#

$IPTABLES -A FORWARD -p tcp -j bad_tcp_packets


#
# DMZ section
#
# General rules
#

$IPTABLES -A FORWARD -i $DMZ_IFACE -o $INET_IFACE -j ACCEPT
$IPTABLES -A FORWARD -i $INET_IFACE -o $DMZ_IFACE -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -i $LAN_IFACE -o $DMZ_IFACE -j ACCEPT
$IPTABLES -A FORWARD -i $DMZ_IFACE -o $LAN_IFACE -j ACCEPT

#
# HTTP server
#

$IPTABLES -A FORWARD -p TCP  -i $INET_IFACE -o $DMZ_IFACE -d $DMZ_HTTP_IP --dport 80 -j allowed
$IPTABLES -A FORWARD -p TCP  -i $INET_IFACE -o $DMZ_IFACE -d $DMZ_HTTP_IP --dport 443 -j allowed
$IPTABLES -A FORWARD -p ICMP -i $INET_IFACE -o $DMZ_IFACE -d $DMZ_HTTP_IP -j icmp_packets

#
# LAN section
#

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

#
# LOG all packets reaching here
#

$IPTABLES -A FORWARD -m limit --limit 3/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix "IPT FORWARD packet
died: "


###########################################################
#
# Firewall rules
# Rules applying to the firewall box
#
#
# INPUT chain
#
# Bad TCP packets we don't want
#

$IPTABLES -A INPUT -p tcp -j bad_tcp_packets

#
# Packets from the Internet to this box
#

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

#
# Packets from LAN, DMZ or LOCALHOST
#

# From DMZ Interface to DMZ firewall IP
$IPTABLES -A INPUT -p ALL -i $DMZ_IFACE -d $DMZ_IP -j ACCEPT

# From LAN Interface to LAN firewall IP
$IPTABLES -A INPUT -p ALL -i $LAN_IFACE -d $LAN_IP -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LAN_IFACE -d $LAN_BCAST_ADRESS -j ACCEPT

# From Localhost interface to Localhost IP
$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

# All established and related packets incoming from the internet to the
# firewall
$IPTABLES -A INPUT -p ALL -d $INET_IP -m state --state ESTABLISHED,RELATED -j ACCEPT

# Logging rule
$IPTABLES -A INPUT -m limit --limit 3/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix "IPT INPUT packet
died: "

###########################################################
#
# OUTPUT chain
#
#
# Bad TCP packets we don't want
#

$IPTABLES -A OUTPUT -p tcp -j bad_tcp_packets

#
# Allow ourself to send packets not spoofed everywhere
#

$IPTABLES -A OUTPUT -p ALL -o $LO_IFACE   -s $LO_IP   -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -o $LAN_IFACE  -s $LAN_IP  -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -o $INET_IFACE -s $INET_IP -j ACCEPT

#
# Logging rule
#

$IPTABLES -A OUTPUT -m limit --limit 3/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix "IPT OUTPUT packet
died: "

ご教授いただけたら幸いとおもいます。
どうかよろしくお願いします。