Re: [TLS] Simplifying signature algorithm negotiation

Hubert Kario <hkario@redhat.com> Mon, 18 January 2016 11:42 UTC

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From: Hubert Kario <hkario@redhat.com>
To: tls@ietf.org
Date: Mon, 18 Jan 2016 12:42:12 +0100
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Subject: Re: [TLS] Simplifying signature algorithm negotiation
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On Friday 15 January 2016 17:13:29 Brian Smith wrote:
> David Benjamin <davidben@chromium.org>; wrote:
> > (Whether such certificates exist on the web is probably answerable
> > via CT logs, but I haven't checked.)
> 
> Me neither, and I think that's the key thing that would need to be
> checked to see if my suggestion is viable.
> 
> 3. You get better interoperability with TLS 1.2's NSA Suite B profile
> [1].
> >> (I don't have any particular affinity for that profile other than
> >> it seems to have made choices that have historically been shown to
> >> be above average, and it might be a good idea to avoid interop
> >> failure with other implementations that might have a special
> >> affinity for it.)
> > 
> > What interop faliures are you worried about here?
> 
> The way I proposed things to work for TLS 1.3 is what the Suite B
> profile does for TLS 1.2. A Suite B client cannot describe the Suite
> B profile policy with the signature_algorithms extension as-is, so in
> theory if a Suite B profile client even exists, it would work better
> if servers assumed that ecdsa_sha256 implies P-256 and ecdsa_sha384
> implies P-384. I don't know if any such "Suite B client" actually
> exists, though.

OpenSSL since version 1.0.2 has a setting to enforce strict Suite B 
compliance

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