openssh unix dev - Nov 2024 - ssh compat information

On Thu, 7 Nov 2024 at 07:55, Chris Rapier <rapier at psc.edu>
wrote:
>[...]I had been using
> Blake2b512 for the hashing algorithm but I want to put in a path to use
> xxhash instead. Maintaining backward compatibility means I need to know
> something about the remote.
In the case of sftp at least, that sounds like a function of the
sftp-server not sshd, in which case could you advertise the capability
as an sftp extension?  (look for the SSH2_FXP_VERSION handling)

-- 
Darren Tucker (dtucker at dtucker.net)
GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860  37F4 9357 ECEF 11EA A6FA
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

On Fri, 8 Nov 2024 at 03:16, Darren Tucker <dtucker at dtucker.net>
wrote:
>
> On Thu, 7 Nov 2024 at 07:55, Chris Rapier <rapier at psc.edu> wrote:
> >[...]I had been using
> > Blake2b512 for the hashing algorithm but I want to put in a path to
use
> > xxhash instead. Maintaining backward compatibility means I need to
know
> > something about the remote.
Could you use the already (draft) specified sftp check-file
extension[1] for this?

It takes a comma separated list of algorithms and the server picks the
first it supports.

David

[1]:
https://datatracker.ietf.org/doc/html/draft-ietf-secsh-filexfer-extensions-00#section-3