How can I access server localhost ports via OpenVPN connection?

Question

I have OpenVPN up and running on a server and serving as a gateway to the internet for private browsing.

I also have several apps running on the same server that I would like to access only via OpenVPN.

For example, if I have etherpad active on port 127.0.0.1:8000 on my server, how do I access that website through my OpenVPN connection on my client? Please let me know what setting changes from the standard configurations are required.

Thank you. I have read many OpenVPN posts and have not been able to understand how to do this...and it seems like it should be simple.

Answer 1

In the general case you would want to allow the port on all interfaces, then use a firewall to drop all connections on that port except through the VPN IP range (and localhost)

If you can get it to work, the rule would be something like

iptables -t nat -D PREROUTING -i tun+ -p tcp --dport 8000 -j DNAT --to-destination 127.0.0.1

(The tun+ bit means any tun devices)

In order for this to work, you will probably also need to have 2 other things set -

sysctl -w net.ipv4.conf.all.route_localnet=1
echo 1 > /proc/sys/net/ipv4/ip_forward