RFR: 8317431: Implement simpler Comparator when building certification paths

[Kevin Driver]

On Wed, 3 Jan 2024 16:55:39 GMT, Sean Mullan <mullan at openjdk.org> wrote:

> This enhancement simplifies and improves the performance of the Comparator that the PKIX CertPathBuilder uses to sort candidate certificates.
> 
> [RFC 5280](https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.1) requires that certificates include authority and subject key identifiers to facilitate cert path discovery. When the certificates comply with RFC 5280, the sorting algorithm is fast and efficient. However, there may be cases where certificates do not include the proper KIDs, for legacy or other reasons. This enhancement targets those cases and has shown an increase in performance of `CertPathBuilder.build` by up to 2x in tests involving certificates that do not contain KIDs. Specific changes include:
> 
> - Removed and simplified some of the steps in `PKIXCertComparator.compare` method. Some of these steps were not a good representation of common certificate hierarchies and were overly expensive to perform. 
> - Several methods in `X500Name` and `Builder` have been made obsolete and thus removed.
> - `X500Name` has been changed to use shared secrets instead of reflection to access non-public members of `X500Principal`, and vice-versa.
> - The `CertificateBuilder` test code has been enhanced to set reasonable defaults for serial number and validity fields of a certificate

src/java.base/share/classes/sun/security/provider/certpath/ForwardBuilder.java line 523:

> 521:                 }
> 522:                 if (tAo1 != null) {
> 523:                     if (tAo2 != null) {

Maybe it's unfamiliarity with this code, but I think we could use some comments here, especially since a similar condition is tested on line 534 (except tAo1 would be null in that case?).

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PR Review Comment: https://git.openjdk.org/jdk/pull/17248#discussion_r1447668592