SSH Server change for aidan

Introduction

On XXX, the SSH server software on the aidan time-sharing service will be upgraded to OpenSSH. Unfortunately OpenSSH and the existing software (provided by SSH.com) do not have a compatible way of storing key-pairs. Therefore, existing connection arrangements that use public-key authentication will stop working.

Will this affect me?

If you have not setup public-key authentication for connections to aidan, then you are not affected by this change.

With SSH, it is possible to setup a pair of keys that allow you to log into an SSH server without typing a password. To find out more about public-key authentication, please visit XXX

Fixing public-key authentication

OpenSSH will read the file .ssh/authorized_keys for public key fingerprints that it will accept. If you have existing keys on your client, you may need to convert them to a format understood by OpenSSH.

You can use the ssh-keygen tool distributed with OpenSSH (and available on the time sharing servers) to convert between file types as described in the document Getting OpenSSH to work with ssh.com and itself. You can also use the PuttyGen tool on windows machines.

First ensure that a directory .ssh exists: 

test ! -d ~/.ssh && mkdir ~/.ssh
Now you can convert the file key.pub into a fingerprint and append it to the authorized_keys file: 

ssh-keygen -if key.pub >> ~/.ssh/authorized_keys
TODO: what mechanism for creating keys exists in the ssh.com software on the common desktop? RESULTS: ssh2 only; RSA or DSA; 2048 default length; ssh.com format; upload feature specific to ssh.com server

Testing the results

The OpenSSH server software is currently running on aidan but on port 802. You can therefore test your SSH software connecting to this port now, in order to check that any new key arrangement works.

External links