Re: [secdir] dir review of draft-laurie-pki-sunlight-05

Ben Laurie <> Sat, 09 February 2013 20:47 UTC

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Date: Sat, 09 Feb 2013 20:47:01 +0000
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From: Ben Laurie <>
To: Tobias Gondrom <>
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Cc: "" <>, The IESG <>,, Jeffrey Hutzelman <>
Subject: Re: [secdir] dir review of draft-laurie-pki-sunlight-05
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On 9 February 2013 13:34, Tobias Gondrom <> wrote:
> Hi Ben,
> I also just read through your draft in version -07.
> I can see the draft consists of two parts:
> 1. data structure
> 2. protocol.
> For part #1 the data structure: in case you are not aware of it, some
> years ago the IETF LTANS WG has done something a bit similar in a more
> generic way (i.e. for any data not only for certificates) in form of
> RFC4998 and RFC6283

Interesting. I was not aware of these. From a quick skim they are
indeed similar, but would need a bunch of added machinery to get them
to where CT is (e.g. not append only, no concept of MMD).

> with a number of implementations by major ECM and
> DMS vendors.

No idea what ECM or DMS are in this context.

> Just as a thought, maybe helpful looking at or even for re-use instead
> of re-inventing the wheel?
> Best regards, Tobias
> On 30/01/13 18:15, Ben Laurie wrote:
>> On 29 January 2013 21:28, Jeffrey Hutzelman <> wrote:
>>> On Tue, 2013-01-29 at 11:35 +0000, Ben Laurie wrote:
>>>> On 24 January 2013 19:06, Jeffrey Hutzelman <> wrote:
>>>>> Similarly, as an anti-spam measure, this document proposes that logs accept
>>>>> only certificates which chain back to a known CA, and requires that logs
>>>>> validate each submitted certificate before appending it to the log.  This
>>>>> sounds good, but it's not the only possible mechanism, and so I think MUST
>>>>> is too strong here.  Additionally, there is no discussion of the security
>>>>> implications if a client depends on a log to do this and the log does not
>>>>> actually do so.  Rather than requiring that logs validate every submitted
>>>>> certificate, the document should only RECOMMEND that they do so, and make
>>>>> clear that clients MUST NOT depend on such validation having been done.
>>>> On second thoughts, whilst that is an effective anti-spam measure, it
>>>> is also part of the functionality of CT: i.e. to identify misissue and
>>>> give some means to do something about it. The CA check ensures we have
>>>> someone to blame for misissue.
>>> Hrm.  I sort of thought the idea was for the logs to be untrusted
>>> repositories, able to be audited but not themselves expected to detect
>>> problems.  If logs are expected to do validation of this sort, is there
>>> a way for a third party to discover whether they are doing so (or at
>>> least, whether they are accepting certificates they shouldn't)?
>> A third party can indeed verify this - they just watch the log like
>> any monitor does.
>>>> I am not averse to suggestions that achieve the overall aim, but I
>>>> don't see the virtue of leaving it vague in the description of the
>>>> experiment we are actually running.
>>> I'm not suggesting vagueness; rather, I'm merely suggesting downgrading
>>> a MUST to a SHOULD, which is still quite strong.  What happens if
>>> someone wants to start logging certs issued by a private CA, or
>>> self-signed certs they have observed, or...?
>> I don't see an issue with logging certs from a private CA. As for
>> self-signed certs, I don't see the point, but I guess if someone
>> figures out a point we can relax it in the next version.
>>> I'm suppose I'm OK with keeping the scope narrower than that for
>>> purposes of the experiment, as long as it is possible to relax the
>>> requirement later without breaking the system.  Hence the importance of
>>> making it clear that clients must not rely on logs to have done
>>> validation (on which point I think we've already reached agreement).
>> Cool.
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