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Re: [TLS] Extensions "supported_groups" and "key_share" in TLS 1.3

Dave Garrett <davemgarrett@gmail.com> Thu, 26 November 2015 22:50 UTC

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From: Dave Garrett <davemgarrett@gmail.com>
To: Ilari Liusvaara <ilariliusvaara@welho.com>, Eric Rescorla <ekr@rtfm.com>
Date: Thu, 26 Nov 2015 17:50:11 -0500
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Subject: Re: [TLS] Extensions "supported_groups" and "key_share" in TLS 1.3
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On Thursday, November 26, 2015 02:15:25 pm Ilari Liusvaara wrote:
> I actually looked at the Editors's Copy. The description is a mess: It
> seemingly first requires key_share extension, even for the first
> ClientHello... Now, that extension can't be empty... And then proceeds
> to say to omit it if client has no shares to send... Which looks like
> it is mutually contradictionary.

We went back and forth on whether to omit or require an empty extension. It looks like we have a mix of the two left in there that need fixing. (I think something got merged weird) Thanks for pointing this out.

I think it might be easier if we just required the extension for all cases where (EC)DHE suites are offered, and have it empty to request a server choice, instead of an omitted extension. If I remember correctly, that's what I had originally. One way or another, it needs to be fixed to be consistent.


Dave

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