Re: [TLS] RSA-PSS in TLS 1.3

Ilari Liusvaara <ilariliusvaara@welho.com> Mon, 07 March 2016 16:04 UTC

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Date: Mon, 7 Mar 2016 18:04:23 +0200
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Hannes Mehnert <hannes@mehnert.org>
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Subject: Re: [TLS] RSA-PSS in TLS 1.3
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On Mon, Mar 07, 2016 at 01:51:41PM +0000, Hannes Mehnert wrote:
> On 01/03/2016 11:32, Yoav Nir wrote:
> >> On 1 Mar 2016, at 6:56 AM, Martin Thomson <martin.thomson@gmail.com> wrote:
> >>
> >> On 1 March 2016 at 04:32, Joseph Salowey <joe@salowey.net> wrote:
> >>> We make RSA-PSS mandatory to implement (MUST implement instead of MUST
> >>> offer).   Clients can advertise support for PKCS-1.5 for backwards
> >>> compatibility in the transition period.
> >>
> >>> From my perspective, this is fine.  I would like to say that we won't
> >> ever support PKCS#1.5 for TLS 1.3, but I think that I would rather
> >> have users on 1.3 with PKCS#1.5 than have them stuck on 1.2.
> >>
> >> It seems like others are taking the position that we should say "MUST
> >> NOT use PKCS#1.5”.  
> > 
> > I’d go even further. I’d remove the rsapss(4) value from SignatureAlgorithm,
> > leaving just rsa(1), and say that in TLS 1.3 an RSA signature is PSS just
> > as it was PKCS#1.5 in TLS 1.2.
> 
> I strongly agree to Yoav's proposal!  No need to have both RSA(-PKCS)
> and RSA-PSS numbers in SignatureAlgorithms.

Doesn't SignatureAlgorithms also negotiate the algorithms supported for
the cert chain? If it does, I think that complicates things.

Also, making the same ClientHello mean two different things depending
on yet-unnegotiated version seems odd to me.


-Ilari