Re: [TLS] Closing on PSS. PR#1114

Ilari Liusvaara <ilariliusvaara@welho.com> Mon, 11 December 2017 14:51 UTC

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Date: Mon, 11 Dec 2017 16:51:01 +0200
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Nikos Mavrogiannopoulos <nmav@redhat.com>
Cc: Eric Rescorla <ekr@rtfm.com>, "tls@ietf.org" <tls@ietf.org>
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Subject: Re: [TLS] Closing on PSS. PR#1114
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On Mon, Dec 11, 2017 at 08:59:44AM +0100, Nikos Mavrogiannopoulos wrote:
> On Tue, 2017-12-05 at 12:00 +0100, Nikos Mavrogiannopoulos wrote:
> > On Mon, 2017-12-04 at 17:24 -0800, Eric Rescorla wrote:
> > > Hi folks,
> > > 
> > > I've put together a PR that attemps to address the PSS issue.
> > > 
> > > See:
> > > https://github.com/tlswg/tls13-spec/pull/1114
> 
> As I guess, we cannot mandate RSA-PSS private keys and certificates for
> TLS1.3, I've followed up with a subsection on security considerations
> for re-using the RSA and RSA-PSS private keys. That includes
> recommendations to reduce the impact from cross-protocol attacks
> affecting these keys.
> 
> https://github.com/tlswg/tls13-spec/pull/1123

Some comments:

- Shared keys between servers are fairly common. Some of those servers
  are very badly configured (e.g. Static RSA enabled).
- If another server does not share key, but has certificate valid for
  the name, that certificate can be used as well.

(These are the same considerations as for DROWN).


-Ilari