I asked my system administrator to update the hosts.allow file on my server to allow my new IP Address. Recently, Singtel upgraded me to their 1000 Broadband on Mobile plan. The change in IP is quite expected. My sys admin updated the hosts.allow file but also went to change the ssh login scheme to the key-based authentication. It’s nice that he is hardening the box but i wasn’t sure how to do the ssh login now.

His reply to enquiry on the steps to the new login scheme came in the form of PuTTy keys(.ppk extension) and some steps. I am no longer a windows user so i had no choice but to try and do it Mac style. Quote from shinchi: It Just Works. Not so.

First i need to try and change the keys to openssh keys. I am using OpenSSH which is provided with Terminal.app. Problem is ppk work only on Putty. So i needed to see if Mac can run Putty. You can do that by installing Putty with MacPorts.

% sudo port install putty

Once you have PuTTy installed, PuTTy-gen is what you need to change the ppk keys to openssh.

% puttygen <putty key>.ppk -O private-openssh -o <your openssh key>.ssh

Now with my new openssh key, i can now login to my server with

% ssh <username>@<server ip or hostname> -i <my openssh key>.ssh

Well i got lazy to enter the -i all the time so i renamed the file to id_rsa. But i wonder if this is safe. =/

References:

• http://g-roc.com/29_ssh-vs-putty-private-key-files-ppk-on-mac-os-x.html
• http://leadingedgescripts.co.uk/converttosshkey.php

Tags: keys, mac, macports, privatekey, putty, putty-gen, ssh