Re: [quicwg/base-drafts] token-based greasing / initial packet protection (#3166)

Kazuho Oku <notifications@github.com> Tue, 05 November 2019 06:58 UTC

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Date: Mon, 04 Nov 2019 22:58:47 -0800
From: Kazuho Oku <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] token-based greasing / initial packet protection (#3166)
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kazuho commented on this pull request.



> +* Initial salt; a 16-byte binary blob that is to be used in place of the initial
+  salt defined in section 5.2 of {{QUIC-TLS}}.
+
+A server advertises these seeds using a NEW_TOKEN frame {{frame-new-token}}.
+The token MUST permit the server to recover these seeds.  This property can be
+achieved for example by embedding these seeds in the encrypted token.
+
+For the non-default seeds to work, all the servers within the scope of a
+NEW_TOKEN token are required to have a shared knowledge of those seeds being
+issued and / or how they can be recovered from the tokens. Certain server
+deployments might have difficulty in meeting such a requirement.
+
+A server (or a set of servers) that cannot satisfy this requirement can stick to
+using the default values by consistently advertising the default version number,
+default initial salt, and a packet type modifier of zero in the NEW_TOKEN frames
+it sends.

Am I correct in assuming that what you are looking for is a clarification that servers can announce a set of alternative versions, each of them tied to a fixed initial salt and packet type modifier?

I think that this is the correct text explaining the multi-CDN use-case, where servers cannot agree on anything.

To paraphrase, we'd be explaining:
1. a server that generates a new initial salt for every connection and embeds it into NEW_TOKEN
2. a server that has a fixed mapping between alternative versions vs. salt (and packet type modifier).
3. a server that does not do greasing at all (multi-CDN).

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