I know the title isn't very descriptive. Here's my problem: I work at three sites at three organizations. Let's call them "A", "B", and "Home". I can only connect to sites A and B using cisco vpn connections (vpnc). Home I can connect to from anywhere.

Unfortunately, when I am physically at site B, the firewall (apparnetly) will not allow me to create a vpnc connection to site A. However, I can ssh to Home, create a VPN connection to A from there, and then ssh to site A. Great.

The problem is that I also frequently need to transfer files from site B to site A. I can sftp them to Home, then ssh to Home and sftp them to A, but this is getting very tedious. I'd like a more convenient way. I have no control over the firewalls or networking at sites A or B but I have root access to my machine at all three locations. I can also configure the network and router at Home.

What is the simplest way to transfer files from site B to site A going through my computer at Home?

I've been googling ssh tunnelling, but it's not something I'm familiar with at the moment, and I'm not sure it's the right tool for the job.

Why can't you find out the network topology of this odd site? Knowing the controls would help you decide better than guessing.

A ssh tunnel may be termed stunnel. There are some web pages on how to do that.

Just to clarify, do you mean that I should find out why site B won't let me vpn to site A? To give you an idea of what's going on, B is a university, A is a firm I consult for, and Home is, of course, my home network. The sysadmins at the university are not real accessible (a little hostile, actually), but it sounds like you think I might be able to find out a direct way from them to get to A without going through my home network. Is that right?

I would suggest caution. Bear in mind that the network admins at the university are there to keep THEIR network secure...circumventing network access restrictions (however lame they may be), would be a really good way to get in trouble/fired/prosecuted.

sshfs ?