Subject: RE: Cert Path Validation Bug in pkix-new-part1-00

From: "Pawling, John" <[email-masked]>
Date: Thu, 2 Mar 2000 13:41:15 -0500

Tim/Santosh,

I apologize for the confusion caused by my reply to Stephen's message.  I
misinterpreted Stephen's use of the term "algorithm gap".  I strongly agree
that algorithm parameter inheritance MUST NOT occur across an "algorithm
gap" as defined in Stephen's and Tim's messages.  I strongly agree that
parameter inheritance may only occur when the subject and issuer share the
same parameters.  Recommend that sentence should be added to the first
paragraph in section 7.3, Subject Public Key Algorithms.

Stephen's recommended text enforces the rule that algorithm parameter
inheritance must not occur across an "algorithm gap".  He recommended: "if
the signing algorithm and subject public key algorithms in a certificate
differ, then the issuer MUST include all algorithm parameters in the
subjectPublicKeyInfo as parameter inheritance is not supported in such
cases". Recommend that Stephen's text should be included in the first
paragraph in section 7.3.  Recommend adding "(if applicable)" after "all
algorithm parameters" in the above sentence.

I agree with Santosh's statement that there is no such thing as parameters
in the RSA.  However, I still believe that the pkix-new-part1-00 cert path
validation procedures need to be clarified.  Recommend that the following
text be added to the description of the working_public_key_parameters
variable in section 6.1.2, bullet (i): "Note: There are no algorithm
parameters associated with an RSA public key; therefore, the certification
path validation procedures described in this section specify that the
working_public_key_parameters variable is set to NULL when associated with
an RSA working_public_key."  

I stand by my original comment documented in the attached message that
started this message exchange.

-John

-------------------- Original Message -------------------------------

From:	Pawling, John [[email-masked]]
Sent:	Friday, February 25, 2000 5:08 PM
To:	[email-masked]
Subject:	Cert Path Validation Bug in pkix-new-part1-00 

All,

There is a bug in the certification path validation Wrap-up procedures
section (6.1.5) in the October 22, 1999 PKIX Certificate and CRL Profile
<draft-ietf-pkix-new-part1-00.txt>.  If an issuer cert containing a DSS
public key is used to verify an end-entity cert containing an RSA public
key, then the current Wrap-up procedure does not properly set the
working_public_key_parameters variable to NULL.  With the current procedure,
the working_public_key_parameters is still set to the issuer's DSS algorithm
parameters.  Recommend the following change to section 6.1.5:

OLD:  (d) If the subjectPublicKeyInfo field of the certificate contains an
algorithm field with non-null parameters, assign the parameters to the
working_public_key_parameters variable.

NEW:  (d) If the subjectPublicKeyInfo field of the certificate contains an
algorithm field with non-null parameters, assign the parameters to the
working_public_key_parameters variable.  If the subjectPublicKeyInfo field
of the certificate contains an algorithm field with null parameters, compare
the certificate subjectPublicKey algorithm to the
working_public_key_algorithm.  If the certificate subjectPublicKey algorithm
and the working_public_key_algorithm are different, set the
working_public_key_parameters to null.

============================================
John Pawling, Director - Systems Engineering
J.G. Van Dyke & Associates, Inc;
a Wang Government Services Company
[email-masked]
============================================

---

From: Tim Polk <[email-masked]>
Date: Thu, 02 Mar 2000 17:54:14 -0500

John,

I'm glad we're in agreement.  It was a rather stimulating dicussion and
ensured I review this text exhaustively - both good things.  I see I have
some clean-up work to perform on that section, including your changes to
the wrap-up procedure.  They were needed either way.

Thanks!

Tim