Connect to ssh-1 server from recent Ubuntu

[Colin Watson]

On Mon, Jun 30, 2025 at 12:13:32AM -0400, Jeffrey Walton wrote:
>On Sun, Jun 29, 2025 at 5:37 PM Liam Proven <lproven at gmail.com> wrote:
>> A chap on a vintage-computing list wants to connect to a SunOS machine
>> (pre-Solaris) with SSH from "recent Ubuntu".
>>
>> SunOS that old only understands ssh v1. He says that seems not to have
>> been available since Ubuntu 10.04.
>>
>> Is that right? You can't specify older versions of the protocol?
>
>Related, you might find the package openssh-client-ssh1 useful. See
><https://launchpad.net/ubuntu/+source/openssh-ssh1>.

Correct, this is exactly what it's for.  There was a long period where 
you could specify older versions of the protocol, but eventually 
upstream dropped it; protocol 1 and 2 were really quite different and it 
allowed dropping a great deal of complex but security-critical 
compatibility code.  At the time I discussed the option of providing a 
separate client package frozen at the last OpenSSH version to support 
protocol 1, and upstream were in favour, so that's what I did.

(I think the analysis above is slightly off, though.  Protocol 1 support 
was dropped in openssh 1:7.1p1-1, so the first version of Ubuntu without 
it would have been 16.04, not 10.04.)

-- 
Colin Watson (he/him)                              [cjwatson at ubuntu.com]