kentbrew/node-on-ec2-port-80.md

## node-on-ec2-port-80.md

      
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              node-on-ec2-port-80.md
            
          
    The Problem

Standard practices say no non-root process gets to talk to the Internet on a port less than 1024.  How, then, could I get Node talking on port 80 on EC2?  (I wanted it to go as fast as possible and use the smallest possible share of my teeny tiny little micro-instance's resources, so proxying through nginx or Apache seemed suboptimal.)
The temptingly easy but ultimately wrong solution:

Alter the port the script talks to from 8000 to 80:
}).listen(80);

.. and run it as root:
sudo /usr/local/bin/node foo.js

This is a Bad Idea, for all the standard reasons.  (Here's one:  if Node has access to the filesystem for any reason, you're hosed.)
One possibly-right way:

Add a port forwarding rule via iptables.
Oh dear familiar feeling: you are a total n00b and know not one thing about iptables.

First, I listed the rules currently running on the NAT (Network Address Translation) table:
[ec2-user@ip-XX-XXX-XX-X ~]$ sudo iptables -t nat -L

Chain INPUT (policy ACCEPT)
target     prot opt source    destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source    destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source    destination

I saw nothing, so I felt free to add a rule forwarding packets sent to external port 80 to internal port 8000:
[ec2-user@ip-XX-XXX-XX-X ~]$ sudo iptables -t nat -A PREROUTING -p tcp --dport 80 -j     REDIRECT --to-ports 8000
When I listed again, I saw a new PREROUTING chain:
[ec2-user@ip-XX-XXX-XX-X ~]$ sudo iptables -t nat -L

Chain PREROUTING (policy ACCEPT)
target     prot opt source     destination         
REDIRECT   tcp  --  anywhere   anywhere     tcp dpt:http redir ports 8000 

I checked my Node script, which was running on port 8000, and (yes!) it was responding on port 80.
Fumbling

During my early attempts I screwed up a bunch of times. I removed busted rules by specifying the right table, the right chain, and the right line number, like so:
[ec2-user@ip-XX-XXX-XX-X ~]$ sudo iptables -t nat -D PREROUTING 1

This removed the first line from the PREROUTING chain in my nat table.
Careful, now....

I did not do this myself but throughout this process I had a very strong feeling I should be very careful not to screw up port 22, which was my only way in.
Acknowledgements:


@rckenned,
@jrconlin,
@spullara,
@frozentux for http://iptables.rlworkman.net/chunkyhtml, which is a pretty definitive iptables tutorial.