Re: [TLS] Last Call: <draft-ietf-tls-downgrade-scsv-03.txt> (TLS Fallback Signaling Cipher Suite Value (SCSV) for Preventing Protocol Downgrade Attacks) to Proposed Standard

> This does not mean that every browser will do it.

True, but if FF is able to stick with this, and roll it out into production, that's a strong indication that other browsers may be able to do the same. And, of course, this eliminates the fallback problem at the root.

One remaining issue, however, is reported high rates of TLS 1.3 version intolerance.

Cheers,

Andrei

-----Original Message-----
From: TLS [mailto:tls-bounces@ietf.org] On Behalf Of Yuhong Bao
Sent: Friday, January 16, 2015 12:05 PM
To: Hanno Böck; tls@ietf.org
Cc: ietf@ietf.org
Subject: Re: [TLS] Last Call: <draft-ietf-tls-downgrade-scsv-03.txt> (TLS Fallback Signaling Cipher Suite Value (SCSV) for Preventing Protocol Downgrade Attacks) to Proposed Standard

This does not mean that every browser will do it.

----------------------------------------
Date: Fri, 16 Jan 2015 21:03:27 +0100
From: hanno@hboeck.de
To: tls@ietf.org
CC: ietf@ietf.org
Subject: Re: [TLS] Last Call: <draft-ietf-tls-downgrade-scsv-03.txt> (TLS Fallback Signaling Cipher Suite Value (SCSV) for Preventing Protocol Downgrade Attacks) to Proposed Standard

Recently Mozilla has disabled the now so-called protocol dance, which makes adding another workaround (SCSV) pretty much obsolete:
https://bugzilla.mozilla.org/show_bug.cgi?id=1084025#c7

And a few days ago mozilla dev Brian Smith tweetet this:
"Fx experiment to disable non-secure TLS version fallback is going even better than expected. Starting to feel silly for delaying it so long."
https://twitter.com/BRIAN_____/status/555138042428526593

I think this adds further evidence that adding another workaround layer
(SCSV) is the wrong thing to do. Instead browsers should just stop doing weird things with protocols that compromise security and drop the protocol dance completely.

(By the way: Has anyone thought what happens when people implement TLS hardware that is version intolerant to versions> 1.2 and at the same time send SCSV in the handshake? I'm pretty sure that at some point some hardware will appear that does exactly that. Will we need another SCSV standard for every TLS version then?)

--
Hanno Böck
http://hboeck.de/

mail/jabber: hanno@hboeck.de
GPG: BBB51E42

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