SSH as socks proxy through multiple hosts

Can the following be achieved with SSH.

There are three machines involved:

A. My local machine at home
B. The SSH gateway server at school
C. A workstation in a lab, only reachable through B

I want to setup a SOCKS proxy. I want to be able to surf on my local computer at home, like I am in the lab. This is due some sites that are only reachable from the school's public ip.

So I want to run a SOCKS proxy on host C. But I do not manage to make it work from host A.

I connect to the gateway and from the gateway I connect to the workstation. But I can't make the gateway transfer the traffic properly from and to the proxy.

How can I do this?

Answer

Three slightly different methods. (Replace $PORTX and $PORTY with port numbers of your choice.)

First method: ProxyCommand

machine-a$ ssh -f -N -D $PORT -oProxyCommand="ssh -W %h:%p machine-b" machine-c

Second method:

1. 
   

   Connect from A to B, with "local forwarding" of $PORT to localhost:$PORT.

   
   

   machine-a$ ssh -L $PORT:localhost:$PORT machine-b
   



2. 
   

   Connect from B to C, with "dynamic forwarding" enabled.

   
   

   machine-b$ ssh -f -N -D $PORT machine-c
   



3. 
   

   Configure your browser to use proxy at localhost:$PORT.

   
   

Steps #1 and #2 can be summarized to:

ssh -f -L $PORT:localhost:$PORT machine-b "ssh -f -N -D $PORT machine-c"

Third method:

1. 
   

   Connect from A to B, with "local forwarding" of $PORTX to machine-c:22.

   
   

   machine-a$ ssh -f -N -L $PORTX:machine-c:22 machine-b
   



2. 
   

   Connect from A to C over the tunnel, with "dynamic forwarding".

   
   

   machine-a$ ssh -f -N -D $PORTY localhost -p $PORTX
   

   
   

   (You can omit -f -N if you want to use the same tunnel for interactive connections too.)

   
   


3. 
   

   Configure your browser to use proxy at localhost:$PORTY.