Re: Open Issue in Part1: path length constraints

["David A. Cooper" <david.cooper@xxxxxxxx>]

Steve,

 From a policy point of view, it may make sense to say that only CAs
should be issuing CRLs, but what does this mean from a certificate path
processing point of view?

X.509 states "[t]he cA component indicates if
the certified public key may be used to verify certificate
signatures". It says nothing about CRLs. Similarly, as you note, RFC
2459 ties keyCertSign to CA certificates but does do so with cRLSign. Are
you arguing that we should change the standards to require
basicConstraints with cA=TRUE in certificates that only authorize the use
of the subject's public key to verify signatures on CRLs? Or are you
suggesting that a certificate should be treated as a CA certificate if
cRLSign is set in keyUsage even if basicConstraints is absent?

To be more specific, if we accept the idea that pathLenConstraint should
be computed differently depending on what type of certificate the last
one in the path is, should CA1's relying parties accept CRLs issued by
CA3 in the certification path below?

CA1 ----------------------------> CA2 ----------------------------------> CA3
        basicConstraints:                               keyUsage:
                cA=TRUE                                 cRLSign
                pathLenConstraint=0

                keyUsage:                               CRLDistributionPoints:
                        keyCertSign, cRLSign            cRLIssuer: CA3

At 04:48 PM 3/2/01 -0500, Stephen Kent wrote:
> 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.