[cabfpub] Recourse for domain owners who discover unknown certificates issued to their domain

[Ryan Sleevi]

On Mon, Oct 10, 2016 at 8:34 PM, Peter Bowen via Public <public at cabforum.org
> wrote:

>
> > On Oct 10, 2016, at 5:31 PM, public at cabforum.org wrote:
> >
> > During the discussions about CT name redaction ([1], [2]), it became
> clear
> > that there is no formal policy regarding what actions a CA should take
> if a
> > domain owner approached the CA to get information about a certificate
> issued
> > by the CA for a domain owned by the domain owner. We'd like to start a
> > discussion to craft such a policy. Note that this is not specific to name
> > redaction. A domain owner might discover a non-redacted certificate in a
> CT
> > log or public web crawl, and if the owner doesn't recognize the
> certificate,
> > they should be able to get detailed information from the CA so that the
> > domain owner can determine if the cert was properly issued, and request
> > revocation if it was not.
>
> Rick,
>
> Before we discuss how we authenticate the domain registrant, I think need
> to discuss what a CA must do when so asked by a domain registrant.
>
> As a straw man, I’m going to suggest that an authenticated domain
> registrant can do the following:
>
> - Require revocation of a certificate containing a FQDN or Wildcard DN
> under their registered domain by providing the CA the issuer DN and serial
> number of the certificate
>
> - Require revocation of all certificates containing a FQDN or Wildcard DN
> under their registered domain or a portion of the namespace under their
> registered domain
>
> - Authorize the issuance of certificates containing a FQDN or Wildcard DN
> under their registered domain
>
> - Require the CA to only allow certain named people or email addresses to
> authorize future issuance
>
> The registrant cannot:
>
> - Require the CA to provide a list of all certificates containing a FQDN
> or Wildcard DN under their registered domain
>
> - Require the CA to provide details on the applicant/subscriber for a
> certificate containing a FQDN or Wildcard DN under their registered domain
>
> - Require the CA to provide an unredacted version of a redacted
> certificate containing a FQDN or Wildcard DN under their registered domain
>
> To come up with this list, I considered the situation where domain
> foo.example is registered to Alice (potentially using a proxy as the
> registrant).  Mallory is a nefarious individual and wants to bring harm to
> Alice or Alice’s organization.  Mallory manages to take over foo.example
> (either due to Alice letting it expire or via domain transfer fraud) and
> then proceeds to contact CAs to get info about foo.example and Alice.  What
> should a CA be required to release?
>

I think I'd disagree with most of the "cannot", but I agree, it's a
slippery slope.

As we've seen during the discussion of CAA, several CAs feel that it's
perfectly acceptable for the domain operator to be distinct from the
certificate applicant - that is, that it's OK to issue certificates not
necessarily approved by a central 'policy' team or other business controls.
This has come up both in discussion of why CAA hard-fail is undesirable,
and why "Letter from the CEO" is seen as an acceptable override.

If we accept this - that an organization may not necessarily be internally
aware of the certificates they issue and their policies - then it would
seem revocation may be a heavy handed response, especially for
hypothetically redacted certs. Instead, it may be appropriate to disclose
first - so that these teams can then internally collaborate and figure out
of revocation is the right answer.

That is, if the risk you have to accept is that you could break some
critical piece of your infrastructure if you revoke a redacted cert, simply
because one team didn't talk to another team, internally, then I don't
believe that's a good policy.

I use redaction here, but I think the same applies to "Revoke all
certificates under this namespace"
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