Re: [TLS] Thoughts on Version Intolerance

Hubert Kario <hkario@redhat.com> Sat, 23 July 2016 22:10 UTC

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Date: Sat, 23 Jul 2016 18:10:50 -0400 (EDT)
From: Hubert Kario <hkario@redhat.com>
To: David Benjamin <davidben@chromium.org>
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Thread-Topic: Thoughts on Version Intolerance
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Cc: tls <tls@ietf.org>
Subject: Re: [TLS] Thoughts on Version Intolerance
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----- Original Message ----- 

> From: "David Benjamin" <davidben@chromium.org>;
> To: "Brian Smith" <brian@briansmith.org>;, "Hubert Kario" <hkario@redhat.com>;
> Cc: "<tls@ietf.org>"; <tls@ietf.org>;
> Sent: Saturday, July 23, 2016 8:03:41 AM
> Subject: Re: [TLS] Thoughts on Version Intolerance

> On Sat, Jul 23, 2016 at 3:37 AM Brian Smith < brian@briansmith.org > wrote:

> > Hubert Kario < hkario@redhat.com > wrote:
> 
> > > I'm quite sure that if I were sending a huge extension or many big
> > > extensions,
> 
> > > the percentage of servers that are incompatible to them would be similar,
> > > if
> 
> > > not worse. A relatively small 3KiB client hello already causes issues and
> > > this
> 
> > > is not exactly something impossible to achieve with just TLSv1.2 and
> > > session
> 
> > > tickets.
> 

> (Note that one must complete the handshake to get a full picture. Sending the
> ClientHello isn't enough. Full analysis pending, but sending a 1.2
> ServerHello and failing around the Finished message seems to happen often
> enough.)

technically, it's a regular bug, not intolerance

intolerance is when we can't get Server Hello message

On the other hand we have servers like clkmon.com, which seem to choke on measly
1356 byte long Client Hello messages...
-- 
Regards,
Hubert Kario
Quality Engineer, QE BaseOS Security team
Email: hkario@redhat.com
Web: www.cz.redhat.com
Red Hat Czech s.r.o., Purkyňova 99/71, 612 45, Brno, Czech Republic