Editing Scanco Administration (section)

====SSH Tunneling====

This is an alternative to VPN through kinesiology.  It may come in handy if for some reason VPN is not working.

If you're outside the university system and want to access, for example, svn on mike.kin, which is normally blocked by the university firewall, you can do that with ssh tunneling.  Here is an example:

 ssh eric@mighty-mac.kin.ucalgary.ca -L 2000:mike.kin.ucalgary.ca:443 -N

Here is what is going on:
* I want to access port 443 (which is https) on mike.kin.ucalgary.ca.
* I have an account on mighty-mac, so I'm using that server to create an ssh tunnel inside the university firewall.  I could use any machine I had an account on inside the university system, even mike.kin.ucalgary.ca, the one I'm trying to get to (in fact, that would be best, but for purposes of demonstration I'm using a different machine).
* I'm mapping the local port 2000 to port 443 on mike.  Anything I send to localhost:2000 will by sent by ssh or the ssh tunnel to mighty-mac, which will then send it on to port 443 on mike.
* 2000 is a random 4-digit port number.  If by some fluke you happen to choose one that is in use, ssh will complain and you will have to try another port number.

Now I can fire up my browser and point it to

 https://localhost:200/trac/

And what I get is the trac site on mike.

If I want to get the code, I can do this:

 svn checkout https://localhost:2000/svn/numerics88/trunk trunk_tunnel

("trunk_tunnel" is just the directory name where it will end up.  It can be named anything, but this will remind me that it only works when the tunnel is up.)


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