[stefanberger]

When the Carmichael-computed private exponent D is too small, the code falls back to the Euler computation, which assigns a newly allocated BIGNUM to *D and thereby leaks the one allocated by the Carmichael computation. Free the first D (clearing it since it is secret) and reset the pointer before falling back.

Summary by CodeRabbit

• Bug Fixes
  • Improved reliability of cryptographic key calculations by ensuring an earlier intermediate result is cleared before an alternate calculation is used. This helps prevent an unsuitable result from affecting the final calculation.

[coderabbitai]

No actionable comments were generated in the recent review.

Walkthrough

When the Carmichael-derived D has at most half the bit length of N, ComputePrivateExponentD now clears D and sets it to NULL before computing the Euler fallback.

Changes: Private exponent calculation

Layer / File(s)	Summary
Clear D before Euler fallback src/tpm2/TPMCmd/tpm/cryptolibs/Ossl/Helpers.c	The fallback branch clears the existing Carmichael-derived D and sets it to NULL before computing the Euler result.

Estimated code review effort: 2 (Simple) | ~5 minutes

Change: Bug fix

Merge Risk: Minimal · up to cd7ba

The targeted private-exponent cleanup is safe and introduces no identified merge-blocking risk.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title names the specific fix: a memory leak of the private exponent D in ComputePrivateExponentD. The raw summary and objectives both describe clearing, freeing, and resetting the Carmichael-deriv…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title names the specific fix: a memory leak of the private exponent D in ComputePrivateExponentD. The raw summary and objectives both describe clearing, freeing, and resetting the Carmichael-derived D before the Euler fallback. The title is specific and matches the main change, and it is 70 characters long, within a typical title length.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 1 functions across 1 files.

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

Finishing Touches

Generate docstrings

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Generate unit tests (beta)

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• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

Warning

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ast-grep (0.51.1)

ast-grep could not parse rule config: /ast-grep-rules/ast-grep-essentials/rules/rust/security/weak-hash-md5-rust.yml

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Recent review info

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• Run ID: 9b1aa831-4e39-4455-be98-a603c026cb34

Commits

Reviewing files that changed from the base of the PR and between ff2be88 and cd7ba9c.

Files selected for processing: 1

• src/tpm2/TPMCmd/tpm/cryptolibs/Ossl/Helpers.c

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