As I noted a few weeks ago, October is cyber security awareness month. I’d planned on writing a big how-to for remotely and securely connecting to another computer, but time has escaped me, so what I’ll give here is the quick and dirty version, and trust that my readers can use Google to fill in the backstory.
Back in May, I wrote an article about using SSH as a proxy to help secure your web browsing when away from home. SSH was designed primarily to provide shell (command line) access to remote machines using encryption and other features to prevent someone from eavesdropping, but it can be used to tunnel all kinds of other traffic. For example, you can tunnel your Subversion version control over SSH, using the svn+ssh argument (e.g. svn co svn+ssh my_svn_files). Or you could tunnel your VNC (a remote desktop protocol) over an SSH connection.
Why would you want to tunnel VNC? The first reason is that VNC by default passes all traffic in plain text, which means all of your keystrokes (read: passwords) are exposed. By using an SSH tunnel, your session is encrypted. The second reason is that by using an SSH tunnel, you don’t have to open the firewall for the VNC port(s).
So how do you tunnel VNC, or another protocol? The -L argument to SSH (or LocalForward in the config file) tells SSH to forward locally. To tunnel to a VNC server running on display :1, you’d do something like: ssh -L 5901:localhost:5901 email@example.com and then point your VNC viewer to localhost:1.
In addition to interactive-type uses, SSH can be used for file transport as well. The scp command copies files to and from a remote server in the same manner that the cp command works locally. sftp can be used as a secure replacement for the FTP protocol (but there’s no provision for anonymous access). And most importantly, the venerable rsync command can be used with SSH by specifying it as the argument to the -e flag (e.g. rsync -e “ssh” -av /some/local/directory firstname.lastname@example.org:/the/remote/directory).
So the moral of the story is: SSH can help keep you secure.