RFR: 8346094: Harden X509CertImpl.getExtensionValue for NPE cases [v6]

[Weijun Wang]

On Wed, 19 Feb 2025 10:27:26 GMT, Konanki Sreenath <duke at openjdk.org> wrote:

>> Earlier code will trigger NPE if the certificate does not contain the extensions or if the requested extensions does not exist. The better approach for hardening **getExtensionValue** here is to to check for NULL explicitly before calling **getExtensionValue()** and avoding try-catch block which ensures the readability and maintainability.
>> 
>> After scanning in multiple places where invokng getExtensions on the X509CertInfo reference, the check for NULL is added in the **getKeyUsage()** as well while calling before **getExtensionValue()**
>> 
>> The associated tests are written and added in test class **CertificateExtensions**. Which will ensure to validate the 
>> **getExtensionValue()** and **getKeyUsage()** methods in **X509CertImpl** class.
>
> Konanki Sreenath has updated the pull request incrementally with one additional commit since the last revision:
> 
>   JDK-8346094 : Harden X509CertImpl.getExtensionValue for NPE cases

Only a small nit. Copyright year for `TestHostnameChecker.java` should also be updated.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/23315#issuecomment-2668815018