[cabfpub] On the use of misuse - and the necessity to remove it

Ryan Sleevi sleevi at google.com
Thu Jun 7 15:16:58 UTC 2018


On Thu, Jun 7, 2018 at 11:04 AM, Geoff Keating <geoffk at apple.com> wrote:

>
>
> On Jun 7, 2018, at 3:32 PM, Ryan Sleevi <sleevi at google.com> wrote:
>
>
>
> On Thu, Jun 7, 2018 at 10:24 AM, Geoff Keating <geoffk at apple.com> wrote:
>
>>
>>
>> > On Jun 7, 2018, at 1:40 PM, Ryan Sleevi via Public <public at cabforum.org>
>> wrote:
>> >
>> > In the pursuit of a definition, we tried to work backwards - what are
>> situations we think are misuse.
>>
>> The dictionary definition of ‘misuse’ is:
>>
>> use (something) in the wrong way or for the wrong purpose
>>
>
> I'm not sure how this helps us move forward
>
>
> I’m not sure how any of this discussion helps us move forward.
>

Removing 4.9.1.1 (4) is an explicit proposal. The question is what will be
lost if we do. It's unclear if anything will be lost, and if so, whether
that thing can be articulated.


> 1) Do you believe the right purpose is wholly reflecting in the Subscriber
> Agreement or Terms of Use?
>
>
> I’m having great trouble understanding this question.  Why would I have
> any beliefs in this area?  What does ‘reflected’ mean?  Why are you asking
> me about a Subscriber Agreement I haven’t seen?
>
> 2) Do you believe the right way is wholly reflected in the definition I
> provided (from 1.1),
>
>
> (see above)
>

This seems pretty unhelpful, I'm not sure how best to align our discussion.
There's an explicit proposal - remove 4.9.1.1 (4). Would you (Apple) vote
in favor of this? Would you vote opposed to this? Would you abstain? By
understanding position and concerns, we can make forward progress.


>
> that the right way is "used for authenticating servers accessible through
> the Internet”
>
>
> That does seem like a partial definition of the right way to use a
> certificate.
>
>
> Let’s try to make things more concrete.  Your assertion is that auditors
> are having trouble with this wording.  I presume this means that the
> following things have happened:
>
> 1. A report was made that a certificate was misused.
> 2. The certificate was not revoked.
> 3. The auditors couldn’t tell if step 2 was correct.
>
> So, can you tell me more about the circumstances?  What kind of misuse was
> alleged?
>

Let's make it more concrete - no need to even get to the point of auditors.

I submit a problem report to a CA that says "This server operator is
infecting my brain with radio waves by using their certificate. I would
like you to revoke it for misuse."

As a CA, how do you determine whether or not that is misuse - so your
obligations are clear and followed.
As a CA, how do you determine whether or not browsers will sanction you for
not stopping the brain infections?


>
> > Another suggestion was that it involved scenarios where the Subscriber
>> private key was in an HSM, and itself was not compromised, but had signed
>> things it was not expected to. This wasn't elaborated on further - so I'm
>> uncertain if this meant things other than the TLS handshake transcript -
>> but this is already met by our definition of Key Compromise in 1.6.1, that
>> is:
>> > ""A Private Key is said to be compromised if its value has been
>> disclosed to an
>> >    unauthorized person, an unauthorized person has had access to it, or
>> there exists a
>> >    practical technique by which an unauthorized person may discover its
>> value. “""
>>
>> If a key is in a HSM and not exportable, then its value is not disclosed,
>> nor does an unauthorized person have access *to the key*.  Dictionary
>> definition of ‘access’ is 'obtain, examine, or retrieve’ none of which
>> apply here.  So it is not covered by Key Compromise.
>
>
> I'm not sure - what are you providing an example of?
>
>
> I didn’t use the word ‘example’ anywhere, I do not know what you are
> talking about.
>

It sounds like you may not have completed your thought then. I thought you
were providing a concrete example of an event that is a compromise key. I
provided a short summary of that. Your statement beginning with "If a key"
is fairly unclear - did you omit some concepts?


> I would think that, say, generating a signed message that was not
> authorized, then "an unauthorized person has access to it”.
>
>
> This does not follow.  If I there is an air conditioner behind a locked
> door, I do not have access to it, but maybe I can operate a thermostat and
> it will make me cold.
>

I'm struggling to follow your thinking and confusion, perhaps through the
argument-by-analogy not holding up well. Perhaps my confusion is that
you're treating access as access to the underlying numeric values of the
private key, rather than access to direct the inputs to combine with that
key use. If that's correct, are your concerns ameliorated by rewording that
section that:

A Private Key is said to be compromised if its value has been disclosed to
an unauthorized person, an unauthorized person has had access to the
underlying values of the key or the inputs to operations that use those
values, or there exists a practical technique by which an unauthorized
person may discover its value.
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