Re: [TLS] Don't Split HelloRetryRequest

Stephen Farrell <stephen.farrell@cs.tcd.ie> Thu, 01 April 2021 18:07 UTC

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To: Christopher Patton <cpatton=40cloudflare.com@dmarc.ietf.org>, Martin Thomson <mt@lowentropy.net>
Cc: tls@ietf.org
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From: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Date: Thu, 1 Apr 2021 19:07:08 +0100
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/y0inKQRW9dX6JH1KpoIWAkYpMjw>
Subject: Re: [TLS] Don't Split HelloRetryRequest
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Given the range of Martin's comments, I'd be surprised
if that could be reduced to a PR;-)

But let me ask a question meanwhile - how often does HRR
actually happen and could we not just let ECH fail in a
bunch of situations that would otherwise require all this
new complexity?

Thanks,
S.


On 01/04/2021 18:29, Christopher Patton wrote:
> Hi Martin, would you mind working out a PR? I think being able to compare
> 407 to a concrete alternative would be helpful. Just so that we're on the
> same page, here's a quick summary of the issues that 407 is designed to
> solve. (These may or may not be problems in your view, and I don't claim
> this list is exhaustive.)
> - 233: No acceptance signal until after HRR, so the procedure for computing
> CH2 is underspecified. This can be avoided by advertising the same
> preferences in CHI/CHO, but the spec doesn't require this.
> - 373: To fix 3233, can we put an acceptance signal in HRR.random? Probably
> not, since HRR.random has a value specified in RFC8446.
> - 358: RFC8446 allows the value of an extension in CH2 to differ from CH1
> only if the extension appears in HRR.
> - 333: "Split mode" is broken, since the client doesn't know who the cookie
> is for.
> 
> Best,
> Chris P.
> 
> 
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