Re: [quicwg/base-drafts] Describe interaction between QUIC and TLS regarding saved 0-RTT state (#2947)

Martin Thomson <notifications@github.com> Thu, 10 October 2019 23:58 UTC

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Date: Thu, 10 Oct 2019 16:58:10 -0700
From: Martin Thomson <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Describe interaction between QUIC and TLS regarding saved 0-RTT state (#2947)
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martinthomson commented on this pull request.



> @@ -644,6 +647,27 @@ A client MAY attempt to send 0-RTT again if it receives a Retry or Version
 Negotiation packet.  These packets do not signify rejection of 0-RTT.
 
 
+## Validating 0-RTT Configuration
+
+When a server receives a ClientHello with the "early_data" extension, it has to
+decide whether to accept or reject early data from the client. Some of this
+decision is made by the TLS stack (e.g., checking that the cipher suite being
+resumed was included in the ClientHello; see Section 4.2.10 of {{!TLS13}}). Even
+when the TLS stack has no reason to reject early data, the QUIC stack or the
+application protocol using QUIC might reject early data because the
+configuration of the transport or application associated with the resumed
+session is not compatible with the server's current configuration.
+
+QUIC requires additional transport state to be associated with a 0-RTT session
+ticket. If stateless session tickets are used, this information must be stored
+in the session ticket. Application protocols that use QUIC might have similar

That would be fine.  The use of "must", implying "MUST", is a little too strong.

I would probably say that the choice of location (NEW_TOKEN vs NST) is an implementation-dependent one.  Implementations might want to use NST as that has better fate-sharing and they might not want to concern themselves with path validation for 0-RTT (or to allow a limited amount of 0-RTT in the case the token is bad).  Or, they could insist on a token and strong path validation, so moving the larger state necessary for 0-RTT into the token makes more sense.

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