Re: [TLS] Earlier exporters

Nick Harper <nharper@google.com> Fri, 07 October 2016 20:59 UTC

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From: Nick Harper <nharper@google.com>
Date: Fri, 7 Oct 2016 13:59:08 -0700
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To: Eric Rescorla <ekr@rtfm.com>
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Subject: Re: [TLS] Earlier exporters
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Does the wording of this PR mean that the value from the exporter changes
depending on whether it's run before or after exporter_secret can be
computed? I think it would be better to keep an RFC 5705-style exporter
that remains constant for the connection. The 0-RTT exporter from an API
perspective can be a separate thing that a caller has to explicitly choose
to use.

On Fri, Oct 7, 2016 at 8:10 AM, Eric Rescorla <ekr@rtfm.com>; wrote:

> Please see the following PR:
>   https://github.com/tlswg/tls13-spec/pull/673
>
> This includes various changes to make exporters/resumption work better.
>
> Basically:
> 1. Add a 0-RTT exporter and change the transcript for the regular exporter
> so it
>     only includes the transcript up to ServerFinished. This gives it
> parity with the
>     rest of the traffic keys. If we need an exporter with the full
> transcript we can
>     always add it later
>
> 2. Point out that you can predict ClientFinished for NST when not doing
>     Client auth. This lets you issue tickets on the server's first flight,
> while still
>     ensuring that if you do client auth you still bind resumption to the
> client's
>     full transcript.
>
> These are pretty straightforward changes, so absent objections I'll merge
> them early next week.
>
> -Ekr
>
>
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