Re: [Trans] Relaxing section 5.1

Peter Bowen <pzbowen@gmail.com> Fri, 04 November 2016 14:07 UTC

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From: Peter Bowen <pzbowen@gmail.com>
Date: Fri, 04 Nov 2016 07:07:50 -0700
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To: Ben Laurie <benl@google.com>
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Cc: Melinda Shore <melinda.shore@gmail.com>, "trans@ietf.org" <trans@ietf.org>
Subject: Re: [Trans] Relaxing section 5.1
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On Fri, Nov 4, 2016 at 6:33 AM, Ben Laurie <benl@google.com> wrote:
>
> The bit you didn't quote does say they the log has to accept valid
> certs, tho: "Logs MUST accept certificates and precertificates that
> are fully valid according to RFC 5280 [RFC5280] verification rules and
> are submitted with such a chain."

Sorry about that.  So the three MUSTs together are:

- Logs MUST verify that each submitted certificate or precertificate
has a valid signature chain to an accepted trust anchor, using the
chain of intermediate CA certificates provided by the submitter.

- Logs MUST reject submissions without a valid signature chain to an
accepted trust anchor.

- Logs MUST accept certificates and precertificates that are fully
valid according to RFC 5280 verification rules and are submitted with
such a chain.

When I read these together, I read that Logs must accept _any_
certificate that is fully valid according to RFC 5280 verification
rules and chains to any root the log trusts and logs must _only_ log
such certificates (and no others).

If this is accurate, we need to account for all types of certificates
being logged, as a log cannot choose to reject certificates for usages
other than server authentication and the log cannot reject
certificates that have personal information (e.g. an server
authentication certificate that states which human requested the
certificate in the subject).

This seems like a very strong assertion of policy rather than a
technical discussion of how the CT protocol works.  I would again ask
the WG to reconsider the requirement levels specified in this section.

Thanks,
Peter