Re: is ssh tunneling a security risk?

David: Among other tricks which can be played with SSH tunnels (for good or ill, just the facts) are that if you set up your external host to do "GatewayPorts yes" and open its firewall, you could accidentally (or intentionally, from your ITSec groups' point of view) allow anyone in the world to connect to your external host and traverse your SSH tunnel, in reverse, to the inside of your corporate LAN.

"Security risk" is always a subjective decision made by your IT Security group based on your organizations' priorities, assets, data, etc -- but my guess would be that if they feel it's a risk, it's probably due to your potential to bypass corporate firewalls for incoming traffic.

David M. Kaplan wrote:

My IT department is really heavy on security. From outside the
building, they have a rather complex system setup so that you can get
around the firewall and ssh into a single machine. From there, you have
to ssh into the machine you want to use.

To simplify things, I have been using a tunnel to hop from my machine
directly (through the tunnel) to the machine I want to use in the
building. This has worked fine until a couple of days ago when IT
decided to prohibit tunneling for "security reasons" (attempting to use
the tunnel now responds with "channel 3: open failed: administratively
prohibited: open failed"). This has made it almost impossible to work
with the system.

What I am wondering is exactly what "security risk" does an ssh tunnel
pose? I thought you used an ssh tunnel to enhance security, not the
other way around. Can someone give me a reason why it is a risk to
leave this open or give me good arguments that I can forward to IT for
why they should not prohibit tunneling?