Re: [TLS] Fixing TLS

Hubert Kario <hkario@redhat.com> Wed, 13 January 2016 12:14 UTC

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From: Hubert Kario <hkario@redhat.com>
To: Dmitry Belyavsky <beldmit@gmail.com>
Date: Wed, 13 Jan 2016 13:14:48 +0100
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Subject: Re: [TLS] Fixing TLS
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On Wednesday 13 January 2016 15:11:47 Dmitry Belyavsky wrote:
> Hello Hubert,
> 
> On Wed, Jan 13, 2016 at 2:52 PM, Hubert Kario <hkario@redhat.com>; 
wrote:
> > On Tuesday 12 January 2016 17:31:34 Watson Ladd wrote:
> > > On Tue, Jan 12, 2016 at 5:12 PM, Peter Gutmann
> > > 
> > > <pgut001@cs.auckland.ac.nz>; wrote:
> > > > Yoav Nir <ynir.ietf@gmail.com>; writes:
> > > > 
> > > > To expand on this, I'll take Ilari Liusvaara's comments:
> > > >>Bleeding edge ideas? They essentially re-invented SIGMA, which
> > > >>is
> > > >>over 10 years old. The basic framework for doing 0-RTT is the
> > > >>obvious one. The only new algorithm prsent since TLS 1.2 is
> > > >>HKDF,
> > > >>which is just 5 years old.
> > > >>
> > > >>So I don't see anything "experimential" ideas, mechanisms or
> > > >>algorithms in there
> > > >>
> > > > When SSLv3 was introduced, it also used ideas that were 10-20
> > > > years
> > > > old (DH, RSA, DES, etc, only SHA-1 was relatively new).  They
> > > > were
> > > > mature algorithms, lots of research had been published on them,
> > > > and
> > > > yet we're still fixing issues with them 20 years later (DH =
> > > > 1976,
> > > > SSLv3 = 1996, Logjam = 2015).
> > > 
> > > We all understand that the security of a protocol is not a
> > > function
> > > not of the primitives but of the way the protocol works. The
> > > confusion between export and nonexport DH shares was noted almost
> > > immediately in SSLv3. Furthermore, 512 bit DH is weak: I don't
> > > know how this is a discovery in 2015, given that the reasons for
> > > this were all worked out in the early 90's. So no, Logjam is not
> > > a result of unknown issues appearing after 20 years, but ignoring
> > > known issues.
> > > 
> > > > TLS 2.0-called-1.3 will roll back the 20 years of experience we
> > > > have
> > > > with all the things that can go wrong and start again from
> > > > scratch.
> > > > 
> > > >  SIGMA, at ten years old, is a relative newcomer to DH's 20
> > > >  years
> > > > 
> > > > when it was used in SSLv3, but in either case we didn't discover
> > > > all the problems with it until after the protocol that used it
> > > > was
> > > > rolled out.  We currently have zero implementation and
> > > > deployment
> > > > experience with 2.0-called-1.3 [0], which means we're likely to
> > > > have another 10-20 years of patching holes ahead of us.  This is
> > > > what I meant by "experimental, bleeding-edge".
> > > 
> > > There is an old joke about the resume with one years experience
> > > repeated 20 times. All of the problems in TLS have been known for
> > > decades, as I've repeatedly demonstrated on this list. All of them
> > > were known to cryptographers at the time TLS was being designed
> > > and
> > > deployed. It does not take deployment to trigger analysis.
> > 
> > Exactly this: BEAST and Lucky 13 "possible" problem was described in
> > the RFC itself. Same thing for the "new" Bicycle attack - described
> > in the RFC for TLS 1.0 and repeated in each version since.
> > 
> > So lets not repeat those mistakes - if there are possible issues,
> > lets fix those, now.
> 
> But we should leave the description of the fixed problems somewhere to
> avoid them in future.

yes, decisions and recommendations should have rationale attached to 
them. And especially for recommendations, I don't see why we couldn't 
incorporate them in the RFC - at least for one, if the rationale is 
proven wrong it will be easier to explain why the recommendation should 
be disregarded.

-- 
Regards,
Hubert Kario
Senior Quality Engineer, QE BaseOS Security team
Web: www.cz.redhat.com
Red Hat Czech s.r.o., Purky┼łova 99/71, 612 45, Brno, Czech Republic