ssh compat information

[Chris Rapier]

On 11/7/24 5:06 PM, David Leadbeater wrote:
> 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

It's possible that this could work very well. Is there a reference 
implementation? If not I can still use SSH_FXP_EXTENDED as described in 
the draft as I'm assuming if I send an unknown request type to the 
server I'll get a null/empty/whatever response. As an aside, this 
implementation would not fully meet the implementation requirements of 
the draft but as I'm not sure I'll have the bandwidth to implement all 
of the required hashes but It would be a reasonable basis for it.

Chris