As a suggestion, I always place the ESTABLISHED,RELATED rules first.
It has to check every packet against each rule in turn. Since most
packets will be part of an established connection placing that rule
first minimizes the amount of processing needed.
Steve on iPhone
On 4 Jun 2008, at 02:29, john@xxxxxxxxxxxx wrote:
First, thanks for taking the time to look.
I've been poking at this for almost 2 weeks and am quite stuck.
Here's the nutshell version of what I'm trying to do:
Client machine has an IP address of 192.168.100.101. The only way I
want this client to be able to communicate with machines on the
10.138.x.x network is via HTTPS (443), plus make DNS lookup
requests. I don't want PING, or any windows SMB type connections to
succeed. Just HTTPS and DNS. Also, the linux box provides dhcp
services to the 192.168.200.x network.
I think my fundamental understanding of iptables is wrong.
I 'think' the INPUT is what's allowed to the local machine (i.e.
firewall box)
FORWARD is what's passed from NIC to NIC.
OUTPUT is what's allowed off the NIC.
Would anybody please give me a hand here? I learn quickly by
examples. I've poked at a large number of websites, but am not
making much headway.
Respectfully,
John
Here's my script as it sits. It's driving me nuts that I can
connect via SMB from the clients on the 192 network to windows SMB
shares on the 10. network.
IPT="/sbin/iptables"
# THE NETWORK CONTAINING THE SITE SYSTEMS
DMZ_IP="10.138.2.117"
DMZ_IFACE="eth0"
DMZ_BROADCAST="10.138.2.255"
# THE IP RANGE FOR CLIENT COMPUTERS (disconnected network)
CLIENTS_IP="192.168.200.1"
CLIENTS_IP_RANGE="192.168.200.0/24"
CLIENTS_IFACE="eth1"
$IPT --flush
$IPT --table nat --flush
$IPT --delete-chain
$IPT --table nat --delete-chain
$IPT -A INPUT -j LOG --log-prefix "INPUT_PACKETS: "
$IPT -A FORWARD -j LOG --log-prefix "FORWARD_PACKETS: "
$IPT -A OUTPUT -j LOG --log-prefix "OUTPUT_PACKETS: "
$IPT --policy INPUT DROP
#$IPT --policy OUTPUT DROP
$IPT -A INPUT -p tcp --dport 22 -j ACCEPT
$IPT -A INPUT -p tcp --dport 80 -j ACCEPT
$IPT -A INPUT -p tcp --dport 443 -j ACCEPT
$IPT -A INPUT -p tcp --dport 53 -j ACCEPT
$IPT -A INPUT -p udp --dport 53 -j ACCEPT
#$IPT -A INPUT -p udp -j ACCEPT
#$IPT -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
#$IPT -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
#$IPT -A FORWARD -p tcp --dport 80 -j ACCEPT
$IPT -A FORWARD -p tcp --dport 443 -j ACCEPT
$IPT -A FORWARD -p udp --dport 53 -j ACCEPT
$IPT -A FORWARD -p tcp --dport 53 -j ACCEPT
$IPT -A FORWARD -p tcp --dport 445 -j DROP
$IPT -N LOGDROP
$IPT -A LOGDROP -j LOG
$IPT -A LOGDROP -j DROP
$IPT -A INPUT -j LOG
$IPT -A FORWARD -j LOG
$IPT --table nat --append POSTROUTING --out-interface $DMZ_IFACE -j
MASQUERADE
echo 1 > /proc/sys/net/ipv4/ip_forward
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