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How I Got Node.js Talking on EC2's Port 80
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| 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 system's resources, so proxying through nginx or Apache seemed suboptimal.) | |
| THE TEMPTINGLY EASY BUT TOTALLY 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 POSSIBLE 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 | |
| Chain OUTPUT (policy ACCEPT) | |
| target prot opt source destination | |
| Chain POSTROUTING (policy ACCEPT) | |
| target prot opt source destination | |
| [ec2-user@ip-10-205-14-7 ~]$ sudo iptables -t nat -L | |
| Chain PREROUTING (policy ACCEPT) | |
| target prot opt source destination | |
| REDIRECT tcp -- anywhere anywhere tcp dpt:http redir ports 8000 | |
| Chain OUTPUT (policy ACCEPT) | |
| target prot opt source destination | |
| Chain POSTROUTING (policy ACCEPT) | |
| target prot opt source destination | |
| I checked my Node script, which was running on port 8000, and (yes!) it was responding on port 80. | |
| During my early fumbling 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. | |
| FINAL NOTE: I DID NOT DO THIS MYSELF BUT I HAVE A VERY STRONG FEELING I SHOULD BE VERY CAREFUL NOT TO SCREW UP PORT 22, WHICH IS MY ONLY WAY IN. | |
| Thanks to @rckenned, @jrconlin, and @spullara ... see also http://iptables.rlworkman.net/chunkyhtml for a pretty definitive-looking iptables tutorial from @frozentux. | |
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