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Re: [TLS] Working Group Last Call for draft-ietf-tls-downgrade-scsv-00

"Salz, Rich" <rsalz@akamai.com> Wed, 15 October 2014 16:08 UTC

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From: "Salz, Rich" <rsalz@akamai.com>
To: Florian Weimer <fweimer@redhat.com>, "tls@ietf.org" <tls@ietf.org>
Date: Wed, 15 Oct 2014 12:08:15 -0400
Thread-Topic: [TLS] Working Group Last Call for draft-ietf-tls-downgrade-scsv-00
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Subject: Re: [TLS] Working Group Last Call for draft-ietf-tls-downgrade-scsv-00
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> SCSV implementation would make things worse for Firefox users because it
> results in a reliable connection failure instead of a downgrade from TLS
> 1.1 to TLS 1.2.

Yes, exactly.  If a browser is going to fallback, it could ask the user "I'm going to retry, and you'll lose PFS; if the server is ever cracked by the NSA all your data will be readable.  Proceed?" If the usre clicks yes, then the browser tries again with the fallback SCSV.   (I would hope that the user-agent would provide more understable message, but I'm not optimistic.)

The point kis that a transient network error has highly visible security implications.

HTTP doesn't auto-retry, either.

--  
Principal Security Engineer, Akamai Technologies
IM: rsalz@jabber.me Twitter: RichSalz

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