Question

How do I configure SNAT on IPTables

Posted on June 16, 2014
Asked by EmperorEarth

Goal (for if you have a better solution than my idea): Securely host a purely golang backend webapp on a domain that people don’t have to type “:port number” to access.

My current situation: I am learning golang, and want to create a golang http-server.

(Yes, I know about nginx & reverse-proxy)

Right now, my golang’s web servers are serving on nonprivileged ports, e.g. 8080, instead of port: 80. (I’d like not to run the golang http server as root to run on a privileged port, but that’s just me)

I was wanting my golang http server to serve to port 8080 , and have the IPTables monitor port 80 and redirect port 80 requests to my golang server @ 8080 via SNAT.

Hopefully I’m making myself clear.

I’ve read some documentation on it, but I’m better at learning by example.

Also, with everything on one droplet, I don’t need the entire address SNAT’d, just the ports.

Relevant environment info: Ubuntu 14.04 x64 golang 1.2.2

putty as my ssh client

limited ubuntu xp

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EmperorEarth • October 13, 2016

Accepted Answer

setcap 'cap_net_bind_service=+ep' /path/to/binary

This command needs to be escalated. sudo as necessary
Every new version of your program will result in a new binary that will need to be reauthorized by setcap

[setcap documentation] (http://man7.org/linux/man-pages/man8/setcap.8.html) cap_net_bind_service documentation

EmperorEarth • July 21, 2014

Still haven’t received a more elegant solution.

I have SSL needs now too, so add a line into console: sudo iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-port 10443

EmperorEarth • June 16, 2014

Here’s a temporary solution I worked out:

Enter the following into console: sudo iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080

Source was: http://serverfault.com/questions/112795/how-can-i-run-a-server-on-linux-on-port-80-as-a-normal-user