8346094: Harden X509CertImpl.getExtensionValue for NPE cases

[ksreenath-ora]

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.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• Commit message must refer to an issue
• JDK-8346094 needs maintainer approval

Issue

• JDK-8346094: Harden X509CertImpl.getExtensionValue for NPE cases (Bug - P4 - Approved)

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• 01: Full - Incremental (8030273c)
• 00: Full (2fcfe10f)

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@ksreenath-ora Please do not rebase or force-push to an active PR as it invalidates existing review comments. Note for future reference, the bots always squash all changes into a single commit automatically as part of the integration. See OpenJDK Developers’ Guide for more information.

[openjdk]

This backport pull request has now been updated with issue from the original commit.