Re: [TLS] Encryption of TLS 1.3 content type

Nikos Mavrogiannopoulos <nmav@redhat.com> Mon, 28 July 2014 08:55 UTC

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From: Nikos Mavrogiannopoulos <nmav@redhat.com>
To: Colm =?ISO-8859-1?Q?MacC=E1rthaigh?= <colm@allcosts.net>
Date: Mon, 28 Jul 2014 10:55:53 +0200
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Subject: Re: [TLS] Encryption of TLS 1.3 content type
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On Sat, 2014-07-26 at 10:59 -0700, Colm MacCárthaigh wrote:
> On Sat, Jul 26, 2014 at 10:43 AM, Watson Ladd <watsonbladd@gmail.com>
wrote:
> > This is a change with no rationale: the content type leaks extremely
> > limited information. It complicates implementations that wish to
keep
> > a high degree of codepath similarity between TLS 1.2 and TLS 1.3.
> Leaking alert messages has been a recurring theme common to several
> attacks; hindering a MITM's ability to discern alert messages seems
> like a rational rationale.

Are there any pointers to these attacks? Will these attacks be countered
with such a change? I believe not as alert messages consist of only two
bytes and will be distinct from any other higher protocol messages
transferred by the TLS record protocol. Unless TLS 1.3 intended to
include a length hiding mechanism I see this change as unnecessary and I
agree with Watson on that.

If we cannot avoid changes to TLS 1.3 charter, I believe that any new
proposal comes with a concrete case for it and associated costs of
implementing vs not-implementing. The initial agreement was for a small
revision to TLS (even though I didn't agree on that), and that is now
used as a vehicle to push unrelated to the charter major changes with no
planning whatsoever. I'm afraid in the end the result will be an
ISO-type of protocol.

regards,
Nikos