Using OpenSSH public keys with OpenVMS (and SSH2)

Every Linux box comes with OpenSSH, as does every BSD (at least, I don’t know of any that don’t). UNIX almost invariably comes with OpenSSH as well (although Tru64 is a dying hold-out).

However, OpenVMS 8 comes with an implementation of SSH that appears to be very similar to the commercial SSH produced by F-Secure and distributed by Attachmate.

To use your OpenSSH keys with VMS, a conversion is required – and the configuration files are different as well.

The versions of SSH used are:

VMS $ ssh "-V"
$1$dga010:[sys1.syscommon.][sysexe]tcpip$ssh_ssh2.exe: SSH Secure Shell OpenVMS
(V5.5) 3.2.0 on HP rx2660 (1.40GHz/6.0MB) - VMS V8.3

UNIX $ ssh -V
OpenSSH_5.1p1, OpenSSL 0.9.8g 19 Oct 2007

First, the key must be converted. Using OpenSSH this is easy (assume that the OpenSSH key my_key.pub already exists):

$ ssh-keygen -e -f my_key.pub > my_vmskey.pub
$

Then copy this file to your VMS login directory, putting it into the directory [.ssh2] (relative to your VMS login directory). Let's assume that the UNIX host is named openssh:

VMS $ scp openssh:~/my_vmskey.pub .
VMS $

Then edit the file AUTHORIZATIONS to include this line:

key my_vmskey.pub

Then be sure to test it out from your OpenSSH host:

openssh $ slogin vms
The authenticity of host 'vms (10.6.4.4)' can't be established.
DSA key fingerprint is 46:43:2f:df:0a:4b:37:e2:4f:f9:63:05:21:84:c9:44.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'vms' (DSA) to the list of known hosts.
Welcome to HP OpenVMS Industry Standard 64 Operating System, Version V8.3

$

Note that since you've not logged into the VMS machine previously, it must have its fingerprint added to the file known_hosts.

There is a good article about key conversions that seems to cover all the bases.

The Geek Stuff blog also has an excellent article on connecting to a SSH2 server using OpenSSH, as well as excellent articles on setting up SSH2 for logins and setting OpenSSH for logins.

Of course, the definitive book is SSH: The Definitive Guide by by Daniel Barrett, Richard Silverman, and Robert Byrnes. This book is also now online.