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Re: [TLS] Don't Split HelloRetryRequest

Christopher Patton <cpatton@cloudflare.com> Thu, 01 April 2021 17:30 UTC

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From: Christopher Patton <cpatton@cloudflare.com>
Date: Thu, 01 Apr 2021 10:29:55 -0700
Message-ID: <CAG2Zi216sYnwmZFdHxnMC+8vP0Ewr7tBr0TBc2PKkpJsgRFjiA@mail.gmail.com>
To: Martin Thomson <mt@lowentropy.net>
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Subject: Re: [TLS] Don't Split HelloRetryRequest
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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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