SSH, The Secure Shell: The Definitive Guide, 2nd Edition

Client Features: ssh, scp, and sftp

OpenSSH clients have new features pertaining to keyboard-interactive authentication, connection sharing, known-hosts handling, port forwarding, and command-line editing and history.

KbdInteractiveDevices Keyword

The KbdInteractiveDevices keyword was undocumented in OpenSSH 3.9, but now it’s officially supported. It determines the devices that the client will try for keyboard-interactive authentication.

    KbdInteractiveDevices = pam,skey,bsdauth

More Control for Connection Sharing

If you’re using the connection-sharing feature of ssh, you can now control the master process of that connection with the -O option. To check whether you’re using connection sharing, run the following:

    $ ssh -O check server.example.com

To request the master process to exit, run the following:

    $ ssh -O exit server.example.com

Hashing of Hostnames

In previous versions of OpenSSH, known_host files contain the hostnames and IP addresses of the computer’s you’ve visited via SSH. If you’d like to keep this information more private, use the new HashKnownHosts configuration keyword in your client configuration file:

    HashKnownHosts yes

SSH clients will now hash the hostnames so they look like random strings—for example:

    |1|Un5Q61BdVPCq65Yj3ec/HH6r+zI=|2pPQE/qjP7rrPLblvS1epjYbUOs=

This feature is experimental at the moment, so use it at your own risk.

Port Forwarding

When you construct a port forwarding, you can now specify a bind address: the address on which the accepting side of the forwarding ...