fix: Null protection on Security Descriptor owner - BED-9499

[definitelynotagoblin]

Description

Don't throw when Security Descriptor has no owner.

Motivation and Context

This PR addresses: BED-9499

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Chore (a change that does not modify the application functionality)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have met the contributing prerequisites
  • Assigned myself to this PR
  • Added the appropriate labels
  • Associated an issue: Issues and Pull Requests README BloodHound#672
  • Read the Contributing guide: https://github.com/SpecterOps/BloodHound/wiki/Contributing
• I have ensured that related documentation is up-to-date
  • Open API docs
  • Code comments
• I have followed proper test practices
  • Added/updated tests to cover my changes
  • All new and existing tests passed

Summary by CodeRabbit

• Bug Fixes
  • Security descriptor ownership checks now safely return no owner when none is configured, instead of causing an error.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 0848d2f7-51c7-42da-a867-7c92577eedd7

📥 Commits

Reviewing files that changed from the base of the PR and between fcb6cb9 and 8c125f5.

📒 Files selected for processing (2)

• src/CommonLib/SecurityDescriptor.cs
• test/unit/SecurityDescriptorTests.cs

Included review availability: 4 reviews are currently available. Your included PR review attempts over the past 7 days set your current allowance at 5 reviews per hour.

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Walkthrough

GetOwner now returns null for security descriptors without an owner. A Windows-only unit test verifies this behavior.

Changes

Owner handling

Layer / File(s)	Summary
Handle missing owners src/CommonLib/SecurityDescriptor.cs, test/unit/SecurityDescriptorTests.cs	GetOwner preserves a null owner instead of throwing. A Windows-only xUnit test verifies the behavior.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Merge Risk: 🔵 Low · up to 8c125

The null-owner fix is localized, but its nullable return-type annotation may trigger a compiler diagnostic because nullable reference types are not enabled for this project. The PR is mergeable with explicit owner follow-up to adjust the annotation or project configuration.

Poem

I’m a rabbit with ears held high

No owner? null now passes by
The descriptor stays calm and clear
A Windows test confirms it here
No null reference makes me fear
Hop, hop, the fix is near

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description identifies the bug, motivation, issue ID BED-9499, bug-fix type, test coverage, and checklist status. The detailed testing section is not completed, but the description is otherwise mo…
Title check	✅ Passed	The title clearly identifies the null-protection fix for the Security Descriptor owner and includes the related issue ID.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description identifies the bug, motivation, issue ID BED-9499, bug-fix type, test coverage, and checklist status. The detailed testing section is not completed, but the description is otherwise mostly complete.

• Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch anemeth/null-owner-fix

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