Re: [TLS] PSS and 1.2

Ilari Liusvaara <ilariliusvaara@welho.com> Sun, 24 July 2016 11:26 UTC

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Date: Sun, 24 Jul 2016 14:26:31 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Martin Thomson <martin.thomson@gmail.com>
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Subject: Re: [TLS] PSS and 1.2
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On Sun, Jul 24, 2016 at 11:45:48AM +0200, Martin Thomson wrote:
> David Benjamin noted that we really need to decide whether PSS was
> something that we should have supported in TLS 1.2.  We can't have a
> situation where there are two implementations of 1.3 that for some
> reason have 1.3 disabled where they disagree whether PSS is
> acceptable.

My arguing about support for new signature algorithms predated the
crypto negotiation revamp. Back then, one had to assign legacy type
for each TLS 1.3-valid end-entity signature scheme, which for all
practical purposes makes it work in TLS 1.2.

However, since the revamped mechanism entierely dumps legacy types,
it could be possible to have legacy-untyped signatures, which definitely
are not allowed in TLS 1.2 (one could even assign legacy type post-hoc,
which would make it legal for TLS 1.2, but would not affect TLS 1.3
in any way).

However, it is separate matter if backport would make sense for
other reasons...
 

> I have opened a PR that makes it clear that PSS is defined for TLS 1.2.

The legacy type of RSA-PSS is RSA, right?



-Ilari