Subject: RE: Open Issue in Part1: path length constraints

From: Ambarish Malpani <[email-masked]>
Date: Fri, 02 Mar 2001 14:25:17 -0800

Hi Steve,
    Is there anything that restricts indirect CRL issuance only
to CAs? I think the concept of an entity other than the CA
issuing CRLs is reasonably old.

Regards,
Ambarish

---------------------------------------------------------------------
Ambarish Malpani
Architect                                                650.567.5457
ValiCert, Inc.                                  [email-masked]
339 N. Bernardo Ave.                          http://www.valicert.com
Mountain View, CA 94043

-----Original Message-----
From: Stephen Kent [mailto:[email-masked]]
Sent: Friday, March 02, 2001 1:49 PM
To: David Simonetti
Cc: [email-masked]
Subject: Re: Open Issue in Part1: path length constraints

<STUFF DELETED>

I am too bothered by the emergence of the notion that entities other than
CAs issues CRLs. I reread 2459 and it does not seem to make a case for this,
although I did note that the CRLSign bit in key usage did not limit its use
to CAs, even though the KeyCertSign bit is so restricted. But 5.2.5 (the CRL
distribution point extension) does say: "The CRL is signed using the CA's
private key" and that certainly argues for what I would consider the usual
interpretation, i.e., only CAs sign CRLs.

OCSP clearly introduced the notion of a non CA entity vouching for
certificate status. But we're talking about CRLs here and I still think they
should be issued only by CAs. I view the CRLSign bit to be a means by which
a CA can have different keys and certs for cert signing vs. CRL signing, and
appropriate split  that can enhance security in many instances.

Steve

---

From: Stephen Kent <[email-masked]>
Date: Fri, 2 Mar 2001 17:50:43 -0500

Ambarish,

>issuing CRLs is reasonably old.

Well, 5.3.4 (the indirect CRL section) of 2459 says:

    This CRL entry extension identifies the certificate issuer 
associated with an entry in an indirect CRL, i.e. a CRL that has the 
indirectCRL indicator set in its issuing distribution point 
extension. If this extension is not present on the first entry in an 
indirect CRL, the certificate issuer defaults to the CRL issuer. On 
subsequent entries in an indirect CRL, if this extension is not 
present, the certificate issuer for the entry is the same as that for 
the preceding entry.
    This field is defined as follows:

    id-ce-certificateIssuer   OBJECT IDENTIFIER ::= { id-ce 29 }

    certificateIssuer ::=     GeneralNames

    If used by conforming CAs that issue CRLs, this extension is 
always critical.  If an implementation ignored this extension it 
could not correctly attribute CRL entries to certificates.  This 
specification RECOMMENDS that implementations recognize this 
extension.

The text avoids referring to a CA as the indirect CRL issuer at 
first, but then refers to conforming CAs in the last paragraph. If 
something other than a CA issues an indirect CRL, or any kind of CRL, 
then the wording used throughout 2459 seems to not apply to such an 
entity, because we almost always seem to come back to phrases like 
"if used by a fonforming CA ..." The best rationale I've usually 
heard for indirect CRLs has been for one CA to issue a CRL for 
another, e.g., if the latter CA looses the ability to issue CRLs to 
to destruction of its private key.

Steve