Tuesday, January 31, 2012

iptables NAT port forward 443 (https) to 8443

I recently wanted to setup port forwarding on an Ubuntu Linux server (AWS EC2) to redirect https traffic (port 443) to a Tomcat server listening for SSL connections on port 8443. I really did not want to learn anything about UFW or iptables - I just wanted to setup the forwarding and get on with my day, so I proceeded to Google away and read man pages and finally figured out the following commands after learning more than I wanted to learn - which was a complete waste, because I'll forget it all anyway:

sudo iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-ports 8443

sudo iptables -t nat -A OUTPUT -p tcp --dport 443 -o lo -j REDIRECT --to-port 8443

The first command adds (-A) a rule to iptable's PREROUTING table to redirect incoming packets bound for port 443 over to port 8443. The second rule adds a similar rule to the OUTPUT table that redirects packets outgoing to port 443 on the loopback interface (-o lo).

Of course there's another trick - those rules disappear on reboot unless we save them somewhere. If you're running UFW, then add the rules to /etc/ufw/before.rules. Otherwise one solution is to install the iptables-persistent extension (on Ubunutu: sudo apt-get install iptables-persistent), and save the rules to /etc/iptables/rules.v4.

I hate this sysadmin garbage ...

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