[TLS] PR ¤468: Cookie for hrr

Ilari Liusvaara <ilariliusvaara@welho.com> Sun, 22 May 2016 14:22 UTC

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Date: Sun, 22 May 2016 17:22:12 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: tls@ietf.org
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Subject: [TLS] =?utf-8?q?PR_=C2=A4468=3A_Cookie_for_hrr?=
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Looking at PR #468:
- It isn't at all obvious how to use it for stateless rejection.
- It is even less obvious how to recover (not causing non-retryable
  fault) from bad cookie (e.g. expired) remembered from previous

There are some tricks for both, but with latter, the 255-byte
cookie space can become quite cramped...

I think it would be easier if either:
- Cookies could not be remembered across connections.
- HRR and EE cookies had separate slots those go to in CH.

(Of course, neither of those solves the "failed 0-RTT" case...)

Also, some clients do burst connects, where multiple TLS
connections are connected in parallel. Through quite frequently
these would be pure-PSK, keyed off one master GDHE-CERT