About this:
> TLS dealt with this to some extent by adding a mechanism
> bacronym'd as GREASE for sending random information in
> extensions to detect implementations that broke on them,
> perhaps something similar could be done for SSH.
The challenge with this is that some widely used implementation - *cough*OpenSSH*cough* - would need to exercise all functions of the protocol that are legal, but not necessarily in widespread use. If they want to prevent rusting at the joints, OpenSSH would have to do so for most features, including those they do not CURRENTLY find useful.
For example, if a common problem is that clients fail to correctly handle global requests if they receive them while waiting for channel open confirmation - this is a bug that both OpenSSH and PuTTY had, at some point long ago - then the way to exercise that would be to include a trivial global request, in say 10% of cases, before a channel open confirmation.
I would welcome that, personally, and hence that's why I originally included Damien in this thread. :)
denis