Subject: [TLS] TLS 1.3 draft version extension (0xff02)

From: Peter Wu <[email-masked]>
Date: Mon, 22 Aug 2016 14:29:10 +0200

Hi,

The Implementations wiki page in the Github repository
(https://github.com/tlswg/tls13-spec/wiki/Implementations) states that
extension 0xff02 (65282) defines the TLS draft version in use.

I cannot seem to find an official registration with IANA though which
might cause implementation issues in the future if this extension type
is re-purposed.

Question: can we rely on this extension being used only for specifying
the TLS draft version? We are working on adding TLS 1.3 support to the
Wireshark SSL/TLS dissector, if this extension type is not official we
should probably not add it.
-- 
Kind regards,
Peter Wu
https://lekensteyn.nl

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From: Ilari Liusvaara <[email-masked]>
Date: Mon, 22 Aug 2016 15:48:03 +0300

> extension 0xff02 (65282) defines the TLS draft version in use.

Also, nice surprise mentioning it only there and not in the draft spec
itself (complete with appropriate RFC-Editor notes).

> might cause implementation issues in the future if this extension type

There is no registration for it. However, only draft implmentations
send it (final ones won't), which should limit the damage, as draft
implementations are meant for testing only, and not for general-
purpose use.

> should probably not add it.

Well, I don't suppose it will be re-used quickly...

-Ilari

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From: Xiaoyin Liu <[email-masked]>
Date: Mon, 22 Aug 2016 13:09:07 +0000

I think it will be nice if IANA can reserve some extension ID numbers for private use, so that whenever we need an extension for testing purpose only, we can pick an ID from the private pool without fear of collisions in the future.

Best,

Xiaoyin

From: Ilari Liusvaara<mailto:[email-masked]>
Sent: Monday, August 22, 2016 8:48
To: Peter Wu<mailto:[email-masked]>
Cc: [email-masked]<mailto:[email-masked]>; Alexis La Goutte<mailto:[email-masked]>
Subject: Re: [TLS] TLS 1.3 draft version extension (0xff02)

-Ilari

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From: Peter Wu <[email-masked]>
Date: Mon, 22 Aug 2016 20:07:29 +0200

> implementations are meant for testing only, and not for general-

The same page notes:

    "Implementations of the final version should check for this
    extension and fail to negotiate TLS 1.3 if it is present. That check
    might be removed once sufficient time has passed."

...which suggests that implementations of the final version could
actually care about it.

> Well, I don't suppose it will be re-used quickly...

I don't have a crystal ball, but it would be nice if use of an extension
type is registered somewhere. Either directly with IANA or, as suggested
by Xiaoyin, by reserving a range.
-- 
Kind regards,
Peter Wu
https://lekensteyn.nl

---

From: Martin Thomson <[email-masked]>
Date: Tue, 23 Aug 2016 16:44:22 +1000

> itself (complete with appropriate RFC-Editor notes).

It's in the newly minted experimental space, and as you say, this is
for private testing of implementations.  (If two major browsers count
for that ;)