What am I doing wrong with Iptables?

[Jason Staudenmayer]

You default policy is ACCEPT
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
Change to DROP
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
It's ok to leave the output ACCEPT (so I've heard)
-----Original Message-----
From: Ryan Golhar [mailto:golharam at umdnj.edu] 
Sent: Thursday, April 08, 2004 9:21 AM
To: redhat-list at redhat.com
Subject: What am I doing wrong with Iptables?


I'm trying to secure a server using iptables.  My iptables looks like
this:

# Firewall configuration written by redhat-config-securitylevel
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
#-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
#-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
#-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j
ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
COMMIT


If I understand it correctly, it should only allow traffic on tcp port
22.  However, if I start the dhcp server, and request a dhcp address
from another machine, it succeeds.  I would expect iptables to block
this traffic.  I'm apparently doing something wrong, but I'm not sure
what it is

-----
Ryan Golhar
Computational Biologist
The Informatics Institute at
The University of Medicine & Dentistry of NJ

Phone: 973-972-5034
Fax: 973-972-7412
Email: golharam at umdnj.edu


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