Question

Hi all,

I access the Internet through an HTTP proxy firewall at college. And I need to login to a computer, via SSH, which is outside our network. I tried it as Linux command and on Windows using PuTTY. I also configured PuTTY to use our server's address. But still, "Proxy error: 403 forbidden" pops up. They must've blocked SSH access to outside systems. (college systems as accessible).

I can SSH a web server (not the proxy server) at the college, which I use to browse proxy-free by tunneling. Now this server allows to browse restricted sites, but still no SSH.

Any workaround, please?

Answer 1

It may be that the proxy is only allowing access to HTTP/HTTPS ports (80 or 443). I've worked around that by changing the SSH server to listed on port 443. That made the proxy I had to go through allow the connection, but if you can't change the SSH server then you may be out of luck.

Answer 2

If you can bypass the proxy for web, you can bypass it for SSH by tunneling SSH:

ssh -L 55555:remote-computer-to-ssh-to:22 login@webserver

and once that's in place:

ssh -oPort=55555 remote-login@localhost

This will give you an SSH tunnel to the webserver machine, which then forwards your SSH traffic to the remote machine.