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RE: Binary packet protocol rethink

Peter Gutmann <pgut001@cs.auckland.ac.nz> Mon, 30 November 2015 08:55 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Niels Möller <nisse@lysator.liu.se>
CC: Damien Miller <djm@mindrot.org>, Simon Tatham <anakin@pobox.com>, Simon Josefsson <simon@josefsson.org>, "ietf-ssh@netbsd.org" <ietf-ssh@netbsd.org>
Subject: RE: Binary packet protocol rethink
Thread-Topic: Binary packet protocol rethink
Thread-Index: AQHRK0VdMJRbFzQ1ukq+Xs4ulafSe560QstW
Date: Mon, 30 Nov 2015 08:55:35 +0000
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References: <87egfdxebo.fsf@latte.josefsson.org> <87egfdxebo.fsf@latte.josefsson.org> <nny4dksr3i.fsf@armitage.lysator.liu.se> <1448554180-sup-7145@atreus.tartarus.org> <9A043F3CF02CD34C8E74AC1594475C73F4B857C7@uxcn10-5.UoA.auckland.ac.nz> <alpine.BSO.2.20.1511292228450.12629@natsu.mindrot.org> <9A043F3CF02CD34C8E74AC1594475C73F4B92EF0@uxcn10-5.UoA.auckland.ac.nz>, <nn37vnsyoi.fsf@armitage.lysator.liu.se>
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Niels Möller <nisse@lysator.liu.se> writes:

>One can do all of these with the current ssh wire protocol. It's even
>straight-forward to do. But if we switch to clear text lengths (with no
>other, deeper, changes to the protocol), it gets a lot more difficult.

Why?  The length just tells you how much to decrypt in one block, what you put
inside it is up to you.  At a lower level, the TCP headers already give length
information, and if you can deal with that then you can just as easily deal
with plaintext lengths.

Peter.

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