From: Jeff Mesch <mesch@NanoTech.Wisc.EDU>
To: netfilter@lists.netfilter.org
Subject: Newbie - Default Deny Setup
Date: Wed, 07 May 2003 14:52:15 -0500 [thread overview]
Message-ID: <3EB963EF.2060506@nanotech.wisc.edu> (raw)
I'm completely new to iptables, and am having a problem setting up a
basic firewall, that follows default deny. I'm guessing it's a very
basic error that I'm overlooking. I'm using FWBuilder to create the rules.
I cannot get any traffic out from the internal side. According to the
log file, it is dropping the traffic as a result of RULE_4.
Any suggestions would be greatly appreciated.
Thanks.
->Jeff
-------
#
# Rule 0(NAT)
#
#
$IPTABLES -t nat -A POSTROUTING -o eth0 -s 192.168.0.0/24 -j SNAT
--to-source 198.150.6.16
#
#
$IPTABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
#
# Rule 0(eth0)
#
# Anti-spoofing rule
#
$IPTABLES -N eth0_In_RULE_0
$IPTABLES -A INPUT -i eth0 -s 198.150.6.16 -j eth0_In_RULE_0
$IPTABLES -A INPUT -i eth0 -s 192.168.1.1 -j eth0_In_RULE_0
$IPTABLES -A INPUT -i eth0 -s 192.168.0.0/24 -j eth0_In_RULE_0
$IPTABLES -A FORWARD -i eth0 -s 198.150.6.16 -j eth0_In_RULE_0
$IPTABLES -A FORWARD -i eth0 -s 192.168.1.1 -j eth0_In_RULE_0
$IPTABLES -A FORWARD -i eth0 -s 192.168.0.0/24 -j eth0_In_RULE_0
$IPTABLES -A eth0_In_RULE_0 -j LOG --log-level info --log-prefix
"RULE 0 -- DROP "
$IPTABLES -A eth0_In_RULE_0 -j DROP
#
# Rule 1(eth0)
#
# Anti-spoofing rule
#
$IPTABLES -N Cid3EB03CD7.0
$IPTABLES -A OUTPUT -o eth0 -j Cid3EB03CD7.0
$IPTABLES -A Cid3EB03CD7.0 -o eth0 -j RETURN
$IPTABLES -A Cid3EB03CD7.0 -o eth0 -j DROP
$IPTABLES -N Cid3EB03CD7.1
$IPTABLES -A FORWARD -o eth0 -j Cid3EB03CD7.1
$IPTABLES -A Cid3EB03CD7.1 -o eth0 -s 192.168.0.0/24 -j RETURN
$IPTABLES -N eth0_Out_RULE_1_3
$IPTABLES -A Cid3EB03CD7.1 -o eth0 -j eth0_Out_RULE_1_3
$IPTABLES -A eth0_Out_RULE_1_3 -j LOG --log-level info --log-prefix
"RULE 1 -- DROP "
$IPTABLES -A eth0_Out_RULE_1_3 -j DROP
#
# Rule 0(lo)
#
# allow everything on loopback
#
$IPTABLES -A INPUT -i lo -j ACCEPT
$IPTABLES -A FORWARD -i lo -j ACCEPT
$IPTABLES -A OUTPUT -o lo -j ACCEPT
$IPTABLES -A FORWARD -o lo -j ACCEPT
#
# Rule 0(global)
#
# block fragments
#
$IPTABLES -N RULE_0
$IPTABLES -A OUTPUT -p ip -f -j RULE_0
$IPTABLES -A INPUT -p ip -f -j RULE_0
$IPTABLES -A FORWARD -p ip -f -j RULE_0
$IPTABLES -A RULE_0 -j LOG --log-level info --log-prefix "RULE 0 --
DROP "
$IPTABLES -A RULE_0 -j DROP
#
# Rule 1(global)
#
# ssh access to firewall
#
$IPTABLES -A OUTPUT -p tcp -d 198.150.6.16 --destination-port 22 -m
state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p tcp -d 192.168.1.1 --destination-port 22 -m
state --state NEW -j ACCEPT
$IPTABLES -A INPUT -p tcp --destination-port 22 -m state --state NEW
-j ACCEPT
#
# Rule 2(global)
#
# firewall uses DNS server on Inet
#
$IPTABLES -A INPUT -p udp -s 198.150.6.16 --destination-port 53 -m
state --state NEW -j ACCEPT
$IPTABLES -A INPUT -p udp -s 192.168.1.1 --destination-port 53 -m
state --state NEW -j ACCEPT
$IPTABLES -A OUTPUT -p udp --destination-port 53 -m state --state NEW
-j ACCEPT
#
# Rule 3(global)
#
# 'masquerading' rule
#
$IPTABLES -A INPUT -s 192.168.0.0/24 -m state --state NEW -j ACCEPT
$IPTABLES -A FORWARD -s 192.168.0.0/24 -m state --state NEW -j ACCEPT
#
# Rule 4(global)
#
# 'catch all' rule
#
$IPTABLES -N RULE_4
$IPTABLES -A OUTPUT -j RULE_4
$IPTABLES -A INPUT -j RULE_4
$IPTABLES -A FORWARD -j RULE_4
$IPTABLES -A RULE_4 -j LOG --log-level info --log-prefix "RULE 4 --
DROP "
$IPTABLES -A RULE_4 -j DROP
#
#
echo 1 > /proc/sys/net/ipv4/ip_forward
next reply other threads:[~2003-05-07 19:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-07 19:52 Jeff Mesch [this message]
2003-05-07 21:18 ` Newbie - Default Deny Setup Myles Uyema
2003-05-07 21:41 ` Jeff Mesch
2003-05-07 22:19 ` Myles Uyema
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