Re: [TLS] weird ECDSA interop problem with cloudflare/nginx

Viktor Dukhovni <ietf-dane@dukhovni.org> Tue, 26 July 2016 12:08 UTC

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Date: Tue, 26 Jul 2016 12:08:33 +0000
From: Viktor Dukhovni <ietf-dane@dukhovni.org>
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Subject: Re: [TLS] weird ECDSA interop problem with cloudflare/nginx
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On Tue, Jul 26, 2016 at 01:09:04PM +0300, Ilari Liusvaara wrote:

> > Failure:
> > openssl s_client -connect regmedia.co.uk:443 -cipher ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-CHACHA20-POLY1305
> 
> If you swap the order of these two ciphersuites, does it suceed or fail?
> 
> I.e.
> 
> openssl s_client -connect regmedia.co.uk:443 -cipher ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-AES128-GCM-SHA256

I can reproduce the reported failure in the original order, and at
least for me the swapped variant succeeds.

> Well, your test results certainly blow basic "negotiation accidentially
> blows off all valid candidates and then fails" hypothesis out of the
> water. So it has to be soemthing more complicated.
> 
> Succeeding with the ciphersuites swapped would suggest (as somebody
> else in this thread already said) that it only considers Chacha in
> the first place, not noticing that it may be the only choice after
> certificate selection.

Perhaps that's the issue.

-- 
	Viktor.