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Re: [TLS] Additional warnings on 0-RTT data

Martin Thomson <martin.thomson@gmail.com> Thu, 24 November 2016 03:31 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Thu, 24 Nov 2016 14:31:25 +1100
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To: Colm MacCárthaigh <colm@allcosts.net>
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Subject: Re: [TLS] Additional warnings on 0-RTT data
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On 24 November 2016 at 13:18, Colm MacCárthaigh <colm@allcosts.net> wrote:
> Can I break this into two parts then? First, do you agree that it would be
> legitimate for a client, or an implementation (library), to deliberately
> replay 0-RTT data? E.g. browsers and TLS libraries MAY implement this as a
> safety mechanism, to enforce and audit the server's and application's
> ability to handle the challenges of replay-ability correctly.

OK, let's be clear: I don't agree that the level of paranoia
surrounding 0-RTT is warranted.  I'm of the belief that end-to-end
replay is a property we should be building in to protocols, not just
something a transport layer does for you.  On the web, that's what
happens, and it contributes greatly to overall reliability.

The reaction to perceived problems in 0-RTT is disproportionate.  You
are asking for a license to replay here at some arbitrary layer of the
stack.  That's not principled, it's just on the basis that you don't
like 0-RTT and want to innoculate other people's software against the
ill effects it might create.  What I object to here is the
externalizing that this represents.  Now if I have the audacity to
deploy 0-RTT, I have to tolerate some amount of extra trash traffic
from legitimate clients?

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