Re: [TLS] TLS 1.3 ServerConfiguration

Eric Rescorla <ekr@rtfm.com> Mon, 07 December 2015 13:37 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 7 Dec 2015 05:36:22 -0800
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To: Ilari Liusvaara <ilariliusvaara@welho.com>
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Subject: Re: [TLS] TLS 1.3 ServerConfiguration
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On Mon, Dec 7, 2015 at 3:09 AM, Ilari Liusvaara <ilariliusvaara@welho.com>
wrote:

> This came up while writing serializers/deserializers for various TLS
> 1.2 and 1.3 stuff... Didn't see issues/pull requests for any of
> these...
>
> 1) ServerConfiguration has field early_data_type, which is of type
> EarlyDataType. I don't see definition of that type anywhere. I
> guess it was missed when that type was removed?
>

Oops. This got removed. Will re-add.



> 2) If ServerConfiguration contains an unknown extension, how should
> the client behave? Ignore the unknown extension, ignore the entiere
> ServerConfiguration or send a fatal alert?
>

Ignore the unknown extension seems consistent.


3) Could the group and server_key fields be combined into a single
> field of type KeyShareEntry? The layout would be identical, and
> one could clearly reuse KeyShareEntry parsing


This is a great idea. I will do it!




> (especially
> considering some groups have 2-byte interrior length fields
> as opposed to 1-byte).
>

I noticed this in my implementation as well. I actually propose to just
remove that extra interior length field. Can't see any reason to keep
it.


BTW: The new TLS 1.3 extensions don't have even test values
> assigned. The values I put in were:
> - early_data: 13000 (0x32C8)
> - pre_shared_key: 13001 (0x32C9)
> - key_share: 13002 (0x32CA)
>
- cookie: 13003 (0x32CB)
>

I suggest 40-44 in the order you list above, since we've agreed not to have
specified ranges any more.

-Ekr





>
>
> -Ilari
>
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