Re: Rekey issue

[nisse%lysator.liu.se@localhost (Niels Möller)]

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

>>> I can see at least three ways of dealing with this: (1) [...], (2)
>>> [...], and (3) when rekeying, behave as normal except that a second
>>> copy of the host key from the first time around is, effectively,
>>> added as a trusted key for the host.
>
>> OpenSSH does:
>
>> (4) silently accept the hostkey if it is identical to the one used to
>> authenticte the previous KEX, search the known hostkeys otherwise and
>> if not found there then do whatever is configured for hiterto-unknown
>> hostkeys.
>
> I must be missing something.  To me, this sounds like (3).  What's the
> difference?

Not sure if the distinction was intended, and if so, if it matters, but
consider the case where the same (previously unknown) host key A occurs
in the first and third key exchange, but a distinct host key B is used
(and somehow accepted) in the second keyexchange.

In this scenario, (3) unconditionally accepts A as trusted when it
returns in the third key exchange, while (4) doesn't.

Regards,
/Niels

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