Ubuntu – How to setup the reverse of ssh -D

PROXYssh

I have two machines: my laptop and a remote server. The server sits behind a firewall that only allows incoming ssh connections. I can use ssh on my laptop to login to the server without any issues.
Since I don't want to (can't) change the firewall, I'd still like to be able to run apt-get upgrade and similar commands on the server, and thought that I could easily do the "reverse" of ssh -D 1234 user@remote – ie change the -D to something else so that I get a "reverse socks proxy" available on the remote end. (This I could later use, after setting up the right environment variables.)

Both machines run Ubuntu 15.04 and I'm using OpenSSH.

What command (or commands) should I issue in order to setup a tunnel with SSH, which has a proxy on my end (the laptop with internet access) and the remote server (which only accepts incoming tcp on port 22)?

Best Answer

OpenSSH 7.6 introduced reverse dynamic proxy as a native option. It is implemented entirely in the client, so the server does not need to be updated.

ssh -R 1080 server

Related Solutions

Ubuntu – SOCKS proxy to SSH server behind HTTP proxy

You would do a lot better to "forward" the remote network's proxy server over SSH rather than using the built-in SOCKS server (which just expects a bare gateway-addressable network at the other end).

ssh -L 8080:internal_ip_of_proxy:8080 user@ssh_server

This exposes the proxy server locally, allowing you to set your browser's proxy settings to localhost:8080 and that will tunnel over SSH to the remote proxy.

And you can apply this to any remote service. You could, for example, tunnel Imgur from your server (in effect a single-host proxy):

ssh -L 8080:imgur.com:80 user@ssh_host

And on a local terminal:

curl --header 'Host: imgur.com' localhost:8080

The Host header is required otherwise curl will request a non-existent localhost site. You could also work around that by adding a line in /etc/hosts, resolving imgur.com to 127.0.0.1... But I'm getting off-topic, you don't need any of this for your purposes.

Ubuntu – auto start a reverse ssh tunnel on system startup

Just add sleep 60; before your ssh command:

@reboot sleep 60;ssh -N -f -R 0.0.0.0:1234:localhost:22  -i /home/username/.ssh/id_rsa  username@remote-server.com
after reboot your network is still down

Best Answer

Related Solutions

Ubuntu – SOCKS proxy to SSH server behind HTTP proxy

Ubuntu – auto start a reverse ssh tunnel on system startup

Related Question