Re: [TLS] AD review of draft-ietf-tls-oldversions-deprecate-06

Benjamin Kaduk <kaduk@mit.edu> Wed, 14 October 2020 03:24 UTC

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Date: Tue, 13 Oct 2020 20:24:07 -0700
From: Benjamin Kaduk <kaduk@mit.edu>
To: "Michael D'Errico" <mike-list@pobox.com>
Cc: TLS List <tls@ietf.org>, draft-ietf-tls-oldversions-deprecate.all@ietf.org
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Subject: Re: [TLS] AD review of draft-ietf-tls-oldversions-deprecate-06
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Hi Mike,

On Tue, Oct 13, 2020 at 03:59:27PM -0400, Michael D'Errico wrote:
> > Saying that it's your preference without saying why is likely
> > to have little effect, yes.  (We endeavor to make decisions
> > based on technical merit, not voting, after all.)  Why do you
> > want this?
> 
> Hi,
> 
> I think the advice should be: "If your code currently
> only supports TLS 1.0, please spend a week or two
> adding support for both TLS 1.1 and the downgrade
> protection SCSV."
> 
> Since the vast majority of the 1.0 and 1.1 specifications
> is the same, someone who takes the advice has a
> good chance of succeeding.
> 
> (You could then also say which other extensions are
> important and why, roughly in order of importance.)

I don't see much to object to in that advice, but the precondition is
rather limiting.  Have you considered writing a draft that covers it
(including fleshing out the important extensions)?

> Recommending that people wholesale abandon
> their legacy system and implement TLS (1.2 and)
> 1.3 is asking too much, and will largely be ignored
> by the people who would be able to add 1.1 to their
> 1.0 code.

It may be true that such recommendations will largely be ignored by people
who have 1.0-only implementations (recall that the IETF does not have an
enforcement arm!), but draft-ietf-tls-oldversions-deprecate aims to be a
Best Current Practice, and there are not preconditions to that Best.  The
Best thing you can do for TLS involves TLS 1.3, and TLS 1.2 is probably
okay, too.  I don't see anyone arguing that the Best Curent Practice for
TLS, in general, involves TLS 1.0 or 1.1, at this point.

-Ben