Re: CA vs. EE cert processing

["David P. Kemp" <dpkemp@xxxxxxxxxxxxxx>]

> From: John_Wray@iris.com
> 
> The PKIX working group doesn't have the ability to change X.509; we
> only have control of the PKIX specs.  A change to RFC 2459 would allow
> us to avoid stumbling into into this ambiguity in X.509, with the result
> that:
> 
> i)  PKIX certificates would not be ambiguous to an X.509 verifier,
> 
> and ii) PKIX verifiers would be able to distinguish ambiguous non-PKIX
> certs
> from unambiguous certs, without having to know whether the certificate
> issuer was PKIX-compliant.


The ITU has the ability to change X.509; this ambiguity should qualify
for treatment as a defect, if someone takes it upon themselves to generate
a DR.

You are correct that requiring the extension in EE certs would eliminate
the ambiguity.  But so would any one of:

 * correcting the incompletely-specified X.509 / ISO 9594-8
 * providing for manual intervention in user agents
 * including the Key Usage extension in EE certs
 * choosing to include the Basic Constraints extension in EE certs - PKIX
    does not prohibit that practice, just discourages it.

Changing PKIX from SHOULD NOT to SHOULD would not help - the ambiguity
would remain.  And changing it to MUST would suddenly bring all previously
conforming EE certs into non-conformance, as well as forcing the inclusion
of redundant information in newly-issued certs.

The right answer is to fix X.509 to require the basic constraints
extension in CA certs.  It already requires the version number to be
present in v3 certs; certs with the version number omitted
unambiguously default to v1.