Connect with SSH through a proxy

Question

I have no real idea what I'm doing here so please bear that in mind if you can help me!

I am trying to connect to my virtual server through a proxy but I can't connect, it just hangs. I'm assuming this is because it's not getting through our proxy.

I have tried exactly the same thing at home and it works perfectly. I'm on OSX using Terminal to connect.

Can anyone advise me how I can get through the proxy with SSH?

Answer 1

Here's how to do Richard Christensen's answer as a one-liner, no file editing required (replace capitalized with your own settings, PROXYPORT is frequently 80):

 ssh USER@FINAL_DEST -o "ProxyCommand=nc -X connect -x PROXYHOST:PROXYPORT %h %p"

You can use the same -o ... option for scp as well, see my superuser answer.

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If you get this in OS X:

 nc: invalid option -- X
 Try `nc --help' for more information.

it may be that you're accidentally using the homebrew version of netcat (you can see by doing a which -a nc command--/usr/bin/nc should be listed first). If there are two then one workaround is to specify the full path to the nc you want, like ProxyCommand=/usr/bin/nc ...

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For CentOS nc has the same problem of invalid option --X. connect-proxy is an alternative, easy to install using yum and works --

ssh -o ProxyCommand="connect-proxy -S PROXYHOST:PROXYPORT %h %p" USER@FINAL_DEST

Answer 2

If your SSH proxy connection is going to be used often, you don't have to pass them as parameters each time. you can add the following lines to ~/.ssh/config

Host foobar.example.com
    ProxyCommand          nc -X connect -x proxyhost:proxyport %h %p
    ServerAliveInterval   10

then to connect use

ssh foobar.example.com

Source here