HMAC Troubleshooting: script to calculate KCV

[gcatanese]

Provide an additional script to help developers calculate the KVC of an HMAC key

[gemini-code-assist]

Hello @gcatanese, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

Summary of Changes

As gemini-code-assist, I've reviewed this pull request. The main purpose of this change is to add a new utility script to help developers calculate the Key Check Value (KCV) for HMAC keys. This is a valuable addition for troubleshooting and verifying keys. The PR introduces a new Node.js script that performs the KCV calculation and updates the README file to include instructions on how to use it.

Highlights

• KCV Calculation Method: The script calculates the KCV by computing the HMAC-SHA256 of the fixed input string "00000000" using the provided HMAC key and then taking the last 3 bytes (6 hex characters) of the resulting hash.
• Documentation Update: Updates the tools/hmac/README.md file to include a new section with clear instructions and an example command demonstrating how to run the calculateKcv.js script.

Changelog

• tools/hmac/README.md
  • Added a new section titled 'Calculate KCV of the HMAC key'.
  • Included instructions on how to run the calculateKcv.js script.
  • Provided an example command using a sample HMAC key.
• tools/hmac/calculateKcv.js
  • Added a new Node.js script to calculate the KCV of an HMAC key.
  • Implements HMAC-SHA256 calculation on the input "00000000".
  • Extracts the last 3 bytes of the HMAC result as the KCV.
  • Includes basic command-line argument validation.
  • Outputs the calculated KCV in uppercase hex format.

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Key bytes hide deep,
KCV shows just a glimpse,
Troubleshoot with ease.

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[gemini-code-assist]

Code Review

This pull request introduces a helpful utility script, calculateKcv.js, for calculating the Key Check Value (KCV) of an HMAC key, along with corresponding documentation updates in the README. The script is a good addition for developers working with HMAC keys.

I've found a critical issue regarding the documented HMAC key input format and a point for clarification on the KCV calculation logic. Addressing these will improve the script's usability and robustness.

Also, note a minor typo in the PR description: it mentions "KVC", while the script and common terminology use "KCV". This is just for your information and doesn't require a code change here.

Summary of Findings

• HMAC Key Input Format Inconsistency: The script's usage error message (line 11) states it expects a Base64 encoded HMAC key, but the implementation (line 19) and examples use a Hex encoded key. This is a critical inconsistency.
• KCV Data for HMACing: The script HMACs the literal string "00000000" (line 23). It would be beneficial to clarify if this specific string is intentional or if actual null bytes were intended, as KCV standards can vary. This was commented on with medium severity.
• Typo in Inline Comment: There's a minor typo in the comment on line 18: // Convert the hex stringc should be // Convert the hex string. This was not commented on due to review settings (low severity).
• Redundant Buffer.from() Call: On line 26, Buffer.from(hmacSignature.subarray(...)) is used. Since hmacSignature.subarray() already returns a Buffer, the outer Buffer.from() is redundant. This is a minor inefficiency and was not commented on due to review settings (low severity).

Merge Readiness

The script is a useful addition, but there's a critical issue regarding the HMAC key input format that needs to be addressed before merging. The clarification on the KCV data would also be valuable. Therefore, I recommend that these changes be made before the pull request is merged. As a reviewer, I am not authorized to approve the pull request; please ensure further review and approval as per your team's process once the suggested changes are incorporated.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud