Re: [Trans] Certificate and Precertificate extensions ordering

Eran Messeri <eranm@google.com> Thu, 11 September 2014 11:52 UTC

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Date: Thu, 11 Sep 2014 12:52:33 +0100
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From: Eran Messeri <eranm@google.com>
To: Rob Stradling <rob.stradling@comodo.com>
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Cc: "trans@ietf.org" <trans@ietf.org>, Erwann Abalea <eabalea@gmail.com>, Ben Laurie <benl@google.com>
Subject: Re: [Trans] Certificate and Precertificate extensions ordering
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On Thu, Sep 11, 2014 at 12:45 PM, Rob Stradling <rob.stradling@comodo.com>
wrote:

> On 11/09/14 12:31, Ben Laurie wrote:
>
>> On 11 September 2014 12:27, Ben Laurie <benl@google.com> wrote:
>>
>>> On 11 September 2014 12:17, Rob Stradling <rob.stradling@comodo.com>
>>> wrote:
>>>
>>>> On 11/09/14 11:56, Eran Messeri wrote:
>>>>
>>>>>
>>>>> The poison extension is removed from the Precertificate prior to the
>>>>> log
>>>>> producing an SCT over it, so a client never has to know about it. What
>>>>> the TLS client has to do is to remove the "embedded SCTs" extension
>>>>>    from the certificate prior to validating the signature.
>>>>>
>>>>
>>>> Ditto for the future "redactedlabels" extension.
>>>>
>>>
>>> That one appears in the cert, too, doesn't it?
>>>
>>
>> Sorry, ignore that, it is in the cert but not the precert (though that
>> seems like an arbitrary decision to me).
>>
>
> I was ditto-ing Eran's second sentence, not his first.  Sorry if I wasn't
> clear.
>
> Yes, I think we could put the "redactedlabels" extension in the precert
> too.  Or, might those who wish to use the redaction mechanism also want to
> keep secret the number of redacted domain components?
>
> Hmmm...if we do decide that the number of redacted domain components can
> be revealed by the precert, then it might be simpler to scrap the
> "redactedlabels" extension altogether and instead say that "(PRIVATE)"
> always covers precisely 1 domain component.  Then, if you want to redact 3
> components, you'd put "SAN:dNSName=(PRIVATE).(PRIVATE).(PRIVATE).mydomain.
> com" in the precert.
>
> (To reduce bloat, we could shrink "(PRIVATE)" to "?".  e.g.
> "SAN:dNSName=?.?.?.mydomain.com").
>
+1 to that - seems like it would significantly simplify the implementation
of redacted domain name label: The risk of misalignment between the values
in the extension that counts the number of redacted subdomains for each SAN
and the actual SANs goes away.

>
> <snip>
>
>
> --
> Rob Stradling
> Senior Research & Development Scientist
> COMODO - Creating Trust Online
>