Subject: Re: 3280bis: CRL validation

From: "Denis Pinkas" <[email-masked]>
Date: Thu, 16 Jun 2005 13:34:11 +0100

David,

About "case 3",  I noticed major error in your description :

>(1) The certificate must include a cRLDistributionPoints extension with 
>a distribution point that has the cRLIssuer field present and include 
>the DN from the issuer field of the certificate.

RFC 3280 states on page 42:

   "If the certificate issuer is not the CRL issuer, then the cRLIssuer field 
    MUST be present and contain the Name of the CRL issuer".

Hence it does NOT contain "the DN from the issuer field of the certificate".

Denis

---

From: "David A. Cooper" <[email-masked]>
Date: Thu, 16 Jun 2005 09:08:52 -0400

> Hence it does NOT contain "the DN from the issuer field of the 

Denis,

Yes, this was a typographical error on my part. The final word in the 
sentence should have been "CRL", not "certificate".  The cRLIssuer field 
must include the DN from the issuer field of the CRL.

Denis Pinkas wrote:

>> The concept of indirect CRLs is very simple: If the scope of the CRL
>> includes certificates that have an issuer name (i.e., the contents of
>> the issuer field in the certificate) that is different that the issuer
>> name of the CRL (i.e., the contents of the issuer field in the CRL),
>> then it is an indirect CRL.
>
> I am very sorry, but what you say is in contradiction with 3280bis 
> (see page 51):
>
> "Whenever the CRL issuer is not the CA that issued the
> certificates, the CRL is referred to as an indirect CRL."

OK.  So, I guess that according to this definition a CRL cover covers 
certificates issued by the issuer of the CRL in addition to certificates 
issued by other CAs is both an indirect CRL and a direct CRL. 

> There exists three cases:
>
> 1) The CA is also issuing the CRL (i.e. it uses the same key to both
> create certificates and sign CRLs).

CAs are identified by name, not name plus key, so your "i.e." is not 
correct.  You could subdivide this into two cases if you want:

1a)  The CA is also issuing the CRL and the same key is used to sign 
both the certificate and the CRL.

1b)  The CA is also issuing the CRL and different keys are used to sign 
the certificate and the CRL.

As long as the issuer names in the certificate and CRL are the same it 
is not an indirect CRL (unless, of course, the scope of the CRL also 
includes certificates issued by other CAs).

> 2) The CA is delegating responsibility to one CRL Issuer and that CRL 
> Issuer
> is only taking care of revocation status information for certificates 
> issued by that CA.
>
> 3) The CA is delegating responsibility to one CRL Issuer and that CRL 
> Issuer
> is taking care of revocation status information for certificates 
> issued different CAs.
>
> From the definition on page 51 (unless we change it) cases 2 and 3 are 
> "indirect CRLs".
> This is was I was referring to as cases a) and b) in my earlier e-mails.
>
>> The scope of an indirect CRL may include certificates issued by one or
>> more CAs, but the mechanisms work the same way no matter how many
>> different CA's certificates are included in the scope of the CRL.
>
> So you are taking of case 3, whereas I say let us first agree on cases 
> 1 and 2,
> where case 2 is also called in my earlier e-mails case b).

How does case 3 differ from case 2?  How is the number of CAs whose 
certificates are covered by a CRL matter?

Dave