Re: [TLS] Commentary on the client authentication presentation slides

Ilari Liusvaara <ilari.liusvaara@elisanet.fi> Tue, 11 August 2015 05:00 UTC

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Date: Tue, 11 Aug 2015 08:00:40 +0300
From: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
To: David Benjamin <davidben@chromium.org>
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Subject: Re: [TLS] Commentary on the client authentication presentation slides
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On Mon, Aug 10, 2015 at 07:33:53PM +0000, David Benjamin wrote:
> 
> Why not do this using HTTP's own auth framework? Have the client sign
> something which includes a channel binding, placing it and the certificate
> chain in an Authorization header. You could even transition to it in TLS
> 1.2 deployments, provided EMS is negotiated. When TLS 1.3 and EMS are not
> negotiated, fall back to the legacy thing.

Yeah, that would be much cleaner (and indeed was one[1] of the two ways
I think HTTP/2 client auth can be done without gross hacks).

Except that because for clean operation HTTP needs request-level
authentication, one would have to transmit the authentication
on each request (fortunately, on subsequent retransmits, it
can be compressed very well[2]).


[1] The other would be signaling via HTTP 401 and using that to
trigger new connection with client-driven client auth.

[2] Unless the payload needs internal nonces (and I don't think
it does), one can assume the same certificate on the same connection
always generates the same cert+signature block (if using deterministic
signatures, that happens even if one tries to sign again).


-Ilari