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

Adam Langley <agl@imperialviolet.org> Fri, 26 September 2014 18:43 UTC

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From: Adam Langley <agl@imperialviolet.org>
To: Andrei Popov <Andrei.Popov@microsoft.com>
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Subject: Re: [TLS] Working Group Last Call for draft-ietf-tls-downgrade-scsv-00
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On Fri, Sep 26, 2014 at 11:32 AM, Andrei Popov
<Andrei.Popov@microsoft.com> wrote:
>> But stepping down is a good idea because you want to lose as few features as possible.
> This may well be, but arguably the TLS protocol should not be creating new constraints on the upper SW layers, where it's possible to avoid doing so.
>
> Regardless of what the browser wants to do, the system admin will sometimes disable a specific TLS version machine-wide (or enterprise-wide), e.g. due to version-specific security concerns. I am pointing out that, with the current draft, the browser is forced to not send the SCSV when skipping versions.

If an administrator is worried that version x is too weak, then all
versions <= x need to be disabled too I believe? I can't think of a
security concern that is not monotonic with respect to TLS versions.


Cheers

AGL

-- 
Adam Langley agl@imperialviolet.org https://www.imperialviolet.org

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