Re: Portsentry tcpd and iptables question

["Patrick Kirk" <patrick@kirks.net>]

Comments please - it seems to work but there may be obviuos gotchas I need
to be aware of.
Thanks.

#!/bin/sh

#Be secure, ish
PATH=/sbin:$PATH; export PATH

modprobe ip_conntrack
modprobe ip_conntrack_ftp
modprobe iptable_nat

hostname=enterprise
any="0.0.0.0/0.0.0.0"

#Flush things
iptables -F
iptables -F -t nat
iptables -F -t mangle
iptables -X

## Create chain which blocks new connections, except if coming from inside.
iptables -N block
iptables -N DLOG

# anti-spoofing rule
iptables -A block -m state --state INVALID -j DLOG

#Continuations
iptables -A block -m state --state ESTABLISHED,RELATED -j ACCEPT

#Allow services on lo in entirety
#Without this Squirrelmail can't authenticate so not sure what it does.
iptables -A block -s 127.0.0.1/32 -i lo -j ACCEPT

#Allow LAN on eth0 in entirety
iptables -A block -s 192.168.0.0/16 -i eth0 -j ACCEPT

#Open ports
iptables -A block -p tcp --destination-port 22 -j ACCEPT
iptables -A block -p tcp --destination-port 80 -j ACCEPT
iptables -A block -p udp --destination-port 58800 -j ACCEPT


#identd
iptables -A block -p tcp --destination-port 113 -j REJECT \
         --reject-with tcp-reset

#Catch-all
iptables -A block -j DLOG

#The DLOG (drop+log) chain
iptables -A DLOG -j LOG --log-prefix="catch-all " --log-tcp-options \
         --log-ip-options
iptables -A DLOG -j DROP

## Jump to that chain from INPUT and FORWARD chains.
iptables -A INPUT -j block
iptables -A FORWARD -j block

## set up masquerading as well
iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE

## Turn on IP forwarding
echo 1 > /proc/sys/net/ipv4/ip_forward