Name based SSH proxy

Kasper Dupont
Wed, 27 May 2015 10:09:00 -0000

On 27/05/15 11.07, Dirk-Willem van Gulik wrote:
> As a practical suggestion - we ran for a while with a hack where we abuse
the version human readable string with a
> base64 string of a _salted_ hash of the server we where trying to get to.
>
> Sharing both salt and hash.
>
> This let the server figure out the right key to present without too much
ado; but without leaking all that much*.  The idea was to make it a tiny bit
more costly to get a decent selector really early in a connection.

That approach seems to rely on the proxy knowing the full
list of possible hostnames in advance. In my case the
proxy doesn't know the list of hostnames in advance.

>
> However - as keeping a few 10?s of packets in state is no longer that
costly; key init and exchange always start at a packet; And the DH modulus
(identical but for its last for bytes) in the DH group exchange (31) and what
not follow soon thereafter; it seems all a bit superfluous.

That sentence I did not understand. Could you elaborate
or explain it differently?