Re: Fixing exchange of host keys in the SSH key exchange

[Peter Gutmann <pgut001%cs.auckland.ac.nz@localhost>]

Mouse <mouse%Rodents-Montreal.ORG@localhost> writes:

>As far as I can see, this affects the user only in that "pick up the host key
>on first connect" no longer works.

It breaks TOFU.  Since this is how the vast majority of all users use SSH
(ref: https://www.usenix.org/system/files/login/articles/105484-Gutmann.pdf),
it means it would break SSH for them.  Conversely, it means the vast majority
won't use it.

>Then this suggestion has the additional feature that it will smoke out such
>bugs!

Trying to smoke out non-standards-compliant implementations at this point,
about twenty-odd after SSH2 started getting deployed, is probably a bit late
in the game.

Also, does this mean any implemenation that doesn't correctly implement a MUST
or MUST NOT can regarded as broken and discarded?

Peter.