Re: Should a CRL be required for an OCSP service provider to assert status.

On 06/09/2016 02:30 PM, daniel bryan wrote:

Regarding question 2: should the ocsp service be able to
assert good.. It sounds like your saying, it's ok for it to
assert good, as long as it was learned from an authorized
source, for example, if the CA allows the ocsp service to view
the database of issued certs. But it is NOT ok for the OCSP
service to just say good, when it has no idea if the cert was
issued or valid. This is also semi related to pre-computed
databases. Alot of OCSP service software allows you to
"assume" certs are good as long as they are not on a CRL. for
example, if the CA issued certs 0x1to 0x500 and only revoked
serial 0x100. the software allows you to assume good based on
the CRL. you might say that you want to assume 500 up, and 500
down as good. so 0x1 to 0x600 would be good (with the
exception of the revoked 0x100) But in reality, serials 501 -
600 have never been issued. I can see the certhash extension
being of use here also. Overall, it sounds like your saying,
it is absolutely against standard to assume a cert is good,
unless you have been explicitly told by the CA that its been
issued and is not revoked. Am i understanding this right?

Actually, this is incorrect. RFC 6960
says:

The "good" state indicates a
positive response to the status inquiry. At a minimum, this
positive response indicates that no certificate with the
requested certificate serial number currently within its
validity interval is revoked. This state does not necessarily
mean that the certificate was ever issued or that the
time at which the response was produced is within the
certificate's validity interval. Response extensions may be used
to convey additional information on assertions made by the
responder regarding the status of the certificate, such as a
positive statement about issuance, validity, etc.

The "revoked" state indicates that the certificate has been
revoked, either temporarily (the revocation reason is
certificateHold) or permanently. This state MAY also be
returned if the associated CA has no record of ever having
issued a certificate with the certificate serial number in the
request, using any current or previous issuing key (referred to
as a "non-issued" certificate in this document).

Some OCSP responders act as you describe. They have knowledge about
which certificates have been issued and respond "revoked" for a
certificate that has not been issued. However, this is not required
by the standard, as "good" does not necessarily mean that the
certificate was issued, just that it has not been revoked.

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