How do I tunnel SSH over SSH?

Question

I have successfully setup a tunnel over SSH on linux mint, and can browse the web.

However, when I try to ssh using the same port, I get:

Couldn't establish connection to proxy: Network is unreachable ssh_exchange_identification: Connection closed by remote host

In my mate-network-properties I have selected manual proxy configuration, and socks host is 127.0.0.1

So why doesn't ssh use that proxy information, and can I make it use said proxy?

Answer 1

You don't need to tunnel ssh. You can ssh to the intermediary host then ssh to anywhere else you need.

You can even do it in a single command by forcing allocation of a pseudo-tty using the -t flag:

me@inside$ ssh -t intermediary ssh external
Last login: Fri Sep 21 14:13:25 2012 from intermediary
me@external$ logout
Connection to external closed.
Connection to intermediary closed.
me@inside$ 

The only down side is that you have multiple SSH sessions. But I can't really see why that would be a problem.

Answer 2

Agree with @bahamat, just ssh over ssh directly, without using the SOCKS proxy. There is a way to do it automatically through .ssh/config (requires netcat/nc on the ssh middleman host):

Host my-host-behind-the-firewall
ProxyCommand ssh my-ssh-front-server exec nc %h %p 2>/dev/null

Now you can just

ssh my-host-behind-the-firewall

and it just works. Especially convenient if you have password-free access to the front server using keys.

http://blog.ociru.net/2013/09/24/ssh-proxycommand/

Answer 3

First instance:

# ssh -D 1080 username@first.host

The second instance will use this socks5 proxy:

$ cat /etc/tsocks.conf
....
server = 127.0.0.1
server_port = 1080

Launch,

$ tsocks ssh username@second.host