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Re: [Curdle] [saag] Time for SSH3?

Peter Gutmann <pgut001@cs.auckland.ac.nz> Thu, 21 December 2023 14:25 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Theodore Ts'o <tytso@mit.edu>
CC: Matt Johnston <matt@ucc.asn.au>, John Mattsson <john.mattsson=40ericsson.com@dmarc.ietf.org>, saag <saag@ietf.org>, "curdle@ietf.org" <curdle@ietf.org>
Thread-Topic: [saag] [Curdle] Time for SSH3?
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Date: Thu, 21 Dec 2023 14:23:12 +0000
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Subject: Re: [Curdle] [saag] Time for SSH3?
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Theodore Ts'o <tytso@mit.edu> writes:

>"The attack can be performed in practice, allowing an attacker to downgrade
>the connection's security [...]

I read that too, but that's the theoretical impact, not the practical one.
For example for the SSH implementation I'm most familiar with I can't actually
think of any real weakness that this introduces.  On a scale of dogwash to
Heartbleed, it's definitely on the dogwash end of things.

(As I mentioned earlier, it's a neat attack, but unless it can be extended
from its current form it doesn't appear to be much of a threat to most
implementations beyond AsyncSSH).

And as an aside, this is the exact thing that
https://datatracker.ietf.org/doc/draft-gutmann-ssh-preauth/ would stop dead in
its tracks.

Peter.

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