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Re: Payload length 0

Martin Thomson <martin.thomson@gmail.com> Sun, 20 May 2018 07:15 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Sun, 20 May 2018 17:14:59 +1000
Message-ID: <CABkgnnXETJUkghZu=xxLNU7pBiEWmZ5O32bxDR7f_5Fo9SoK1Q@mail.gmail.com>
Subject: Re: Payload length 0
To: Christian Huitema <huitema@huitema.net>
Cc: Jana Iyengar <jri.ietf@gmail.com>, "Deval, Manasi" <manasi.deval@intel.com>, Marten Seemann <martenseemann@gmail.com>, Ian Swett <ianswett@google.com>, QUIC WG <quic@ietf.org>, Dmitri Tikhonov <dtikhonov@litespeedtech.com>
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It only works to ensure that the last packet remains the last packet.  That
doesn't seem like an actual defense against splitting.
On Sun, May 20, 2018 at 11:37 AM Christian Huitema <huitema@huitema.net>
wrote:

> On 5/19/2018 6:16 PM, Jana Iyengar wrote:

>> The only way to prevent middlebox from hacking some part of the protocol
>> is to use encryption. Any clear text hack will only be a slight road
>> bump for the middle-box hackers.


> Agreed, though I'll note that authenticating may be enough in some cases,
encrypting may not be necessary.

>> For example, if we coalesce a CI and a 0-RTT packet, we could have the
>> zero RTT encryption depend on the presence of the previous packet.


> What I'm suggesting is that the length field, which is part of the
authenticated header, include this signal as zero, or non-zero. I think
this may be one interpretation of what you're saying: the header field,
which is part of the AEAD hash, encodes the presence of another packet.


> Yes, something like that would work. Maybe a flag in the first octet, "is
coalesced".

> Note that, in the plausible CI + 0RTT coalescing, splitting the CI won't
work. It will be too short, and thus rejected by the server.

> -- Christian Huitema

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