iptables question.

Applications Cybersecurity
1

I am setting up a new squid daemon to run on my server. I want to make sure that everyone inside my network can access squid but I want to make sure everyone on the internet is blocked.

eth0 is connected to my internal LAN via: 192.168.0.5/255.255.255.0
eth1 is connected to the internet via: 1.1.1.1/255.255.255.248

Squid listens on port 3124

So far I have the following script for my iptables.

iptables -F
iptables -t nat -F
iptables -X
iptables -P FORWARD DROP
iptables -P INPUT DROP
iptables -P OUTPUT ACCEPT
iptables -A INPUT -p tcp --dport 3124 -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

Is this correct? Will this allow all my LAN users access to squid while blocking outward attempts from the net to my server?

Thanks in advance!

-Ash

2

You should insert another rule to block incoming traffic from the internet to port 3124 above

iptables -A INPUT -p tcp --dport 3124 -j ACCEPT

eg:

iptables -A INPUT -i eth0 -p tcp --dport 3124 -j DROP
iptables -A INPUT -p tcp --dport 3124 -j ACCEPT