Re: [TLS] [tls13-spec] relax certificate_list ordering requirements to match current practice (#169)

mrex@sap.com (Martin Rex) Tue, 12 May 2015 21:46 UTC

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From: mrex@sap.com (Martin Rex)
Archived-At: <http://mailarchive.ietf.org/arch/msg/tls/CTW32ssL-iaeEWK5F79clUCVgeE>
Subject: Re: [TLS] [tls13-spec] relax certificate_list ordering requirements to match current practice (#169)
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Viktor Dukhovni wrote:
> On Tue, May 12, 2015 at 04:03:36PM -0400, Daniel Kahn Gillmor wrote:
>> Then:
>> 
>>  * it seems like we ought to explicitly permit servers to ship the
>>    certificates capable of forming multiple verification chains in the
>>    TLS handshake, so that clients have all the certs they need to find
>>    their preferred path, without having to do AIA fetching.
>> 
>> Given that servers *already do this*, the argument seems even stronger.
> 
> Allowing servers to send a heap seems mostly harmless, provided
> we're not also *requiring* clients to do the full combinatorial
> explosion path construction.


To the contrary, allowing servers to send a heap is the opening of
a rotten can of worms.

Next you see defective clients use that as an excuse for not fixing
e.g. their lack of recognizing a trust anchor when it is included
as crossCA variant in the certificate_list.

Next you see the users of particular broken, unfixed clients asking
why they can not configure a particular heap of junk, to cater their
broken clients, with a particular perfectly correct TLS implementation
(that properly encodes only a linear list of certificates into
certificate_list).

Really, with the proposed change, the shit already hits the fan.

-Martin