SFTP – How to Use SFTP Over Reverse SSH Tunnel

dolphinkdesftpsshssh-tunneling

I want to SFTP to a remote computer that is behind NAT. I can't modify the NAT router, so I have set up a reverse SSH tunnel using a middleman server.

Here's what my SSH tunnel looks like:

laptop--->nat--->middleman<--nat<--desktop

The full details are here:
Remote desktop over SSH reverse tunnel to replace TeamViewer

I am currently using SSH and VNC over this tunnel.

How do I use SFTP over the tunnel?

I assume the command will look something like 

sftp://localhost:port

SSH login is via key pair only (no password) so we need to consider that in the solution. And I use KDE, so I need to get this working with Dolphin file manager. I've heard that setting up SFTP authentication in Dolphin can be a pain…

I'll be running Dolphin on the laptop and connecting to the file system on the desktop like this.

laptop(SFTP client)--->nat--->middleman<--nat<--desktop(SFTP server)

P.S. I would consider sshfs too, if that would be easier. I assume it won't because I don't have a domain name or IP address for the server.

Best Answer

First, this is a prerequesite (at least for me): Remote desktop over SSH reverse tunnel to replace TeamViewer

The reverse SSH tunnel looks like this:

laptop(SFTP client)--->nat--->middleman<--nat<--desktop(SFTP server)

On laptop edit ~/.ssh/config and add this:

Host SftpToDesktop
  HostName localhost
  Port %p
  User admin
  PasswordAuthentication no
  IdentityFile ~/.ssh/my_id_rsa

Then, with an existing SSH leg from laptop to middleman established already (as per above link), do the following:

$ ssh -fNL 1234:localhost:1234 -i ~/.ssh/some_id_rsa admin@middleman.com

Finally, open Dolphin (if using KDE like me) and enter this location:

sftp://SftpToDesktop:1234
Related Question