Re: [TLS] certificate_request_context

Ilari Liusvaara <ilariliusvaara@welho.com> Fri, 07 October 2016 08:34 UTC

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Date: Fri, 7 Oct 2016 11:34:16 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Hannes Tschofenig <hannes.tschofenig@gmx.net>
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Subject: Re: [TLS] certificate_request_context
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On Fri, Oct 07, 2016 at 09:48:32AM +0200, Hannes Tschofenig wrote:
> Hi all,
> 
> I am wondering why the certificate_request_context field found in the
> CertificateRequest and in the Certificate message is so long. It is
> supposed to be used to match a certificate request against incoming
> certificate.
> 
> Does the field really need to be up to 256 bytes long? I think 8 bytes
> should be more than enough.

I presume 255, but whatever...

If application supports any sort of multiplexing (e.g. HTTP/2), one
presumably wants the context to be non-opaque and identify the stream
that caused the request + some parameters about the request (to avoid
duplicating those in application layer).


-Ilari