reverse SSH / SSH over NAT traversal

[Konstantin Svist]

Hi all,

I'm trying to connect to a remote host to do some simple support. The 
remote host is behind a NAT/firewall and it's not possible to ask the 
admin to tunnel a port. The remote host has a live person working on it 
(a linux newbie).
The question is, can the remote user type in some command in their 
terminal to connect (SSH?) to my network - and thereby allow me to get a 
terminal on the remote machine. I think this is possible with a reverse 
SSH tunnel - but I don't really want to allow the remote user any access 
to my system. It's probably possible to set up some chroot or otherwise 
locked out environment (/bin/nologin ?), but I want to first check if 
there are any simpler options.

A better question: is it possible to establish an SSH connection if both 
networks have NAT/firewalls that can't be easily controlled? I know some 
programs (e.g. skype) are able to traverse NATs by various means (UDP). 
Can some tunnel of this sort be established so that an SSH connection 
can be established on top of that?


Thanks!