🛡️ Sentinel: Fix TOCTOU vulnerability in cache creation by abhimehro · Pull Request #428 · abhimehro/ctrld-sync

abhimehro · 2026-02-26T11:04:53Z

Replaced open() followed by chmod() with atomic os.open(..., 0o600) to prevent a race condition where the cache file could be world-readable during creation. Also fixed a syntax error in validate_folder_data that was preventing proper validation.

PR created automatically by Jules for task 6458894056978274991 started by @abhimehro

Co-authored-by: abhimehro <84992105+abhimehro@users.noreply.github.com>

google-labs-jules · 2026-02-26T11:04:54Z

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github-actions · 2026-02-26T11:05:15Z

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gemini-code-assist · 2026-02-26T11:05:19Z

Summary of Changes

Hello @abhimehro, 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!

This pull request enhances the application's security posture by fixing a potential race condition during cache file creation, ensuring sensitive data is not exposed due to temporary incorrect permissions. Additionally, it improves data integrity by correcting a critical bug in the data validation logic, ensuring that incoming folder data is parsed and validated as intended.

Highlights

TOCTOU Vulnerability Fix: Addressed a Time-of-Check to Time-of-Use (TOCTOU) vulnerability in the disk cache creation by replacing open() and chmod() with an atomic os.open() call, ensuring cache files are created with 0o600 permissions securely.
Data Validation Logic Correction: Corrected a syntax error and indentation issues within the validate_folder_data function, which previously prevented the proper validation of rule_groups and their nested rules.

Changelog

main.py
- Implemented atomic file creation for _disk_cache using os.open to set 0o600 permissions, mitigating a TOCTOU vulnerability.
- Refactored the save_disk_cache function to remove the separate chmod call and integrate permission setting into the file creation.
- Corrected syntax errors and indentation in the validate_folder_data function, specifically within the loop that validates rule_groups and their rules.
- Updated error logging messages in validate_folder_data to use correct indexing (i, j) and improve readability.
- Adjusted the scope of the return True statement in validate_folder_data to ensure correct function termination.

Activity

The pull request was automatically created by Jules for task 6458894056978274991, initiated by @abhimehro.

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main.py

+
+    return True
+



main.py

+        # Security: Create file with 0600 permissions atomically to prevent race condition (TOCTOU)
+        # os.open() allows setting mode at creation time, unlike open() which uses umask first.
+        # mode=0o600 ensures only the owner can read/write.
+        fd = os.open(temp_file, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)


main.py

+        # os.open() allows setting mode at creation time, unlike open() which uses umask first.
+        # mode=0o600 ensures only the owner can read/write.
+        fd = os.open(temp_file, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
+        with os.fdopen(fd, "w", encoding="utf-8") as f:


main.py

+                        return False
+
+    return True
+


main.py

+        # Security: Create file with 0600 permissions atomically to prevent race condition (TOCTOU)
+        # os.open() allows setting mode at creation time, unlike open() which uses umask first.
+        # mode=0o600 ensures only the owner can read/write.
+        fd = os.open(temp_file, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)


main.py

+        # os.open() allows setting mode at creation time, unlike open() which uses umask first.
+        # mode=0o600 ensures only the owner can read/write.
+        fd = os.open(temp_file, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
+        with os.fdopen(fd, "w", encoding="utf-8") as f:


main.py

+
+    return True
+



main.py

gemini-code-assist

Code Review

This pull request effectively addresses two separate issues. First, it resolves a TOCTOU (Time-of-Check to Time-of-Use) security vulnerability in the save_disk_cache function by replacing the non-atomic open() followed by chmod() with an atomic os.open() call that sets file permissions on creation. This is a solid security improvement. Second, it fixes significant syntax errors and a logic bug within the validate_folder_data function, which was previously preventing proper data validation and would have caused runtime errors. The function now correctly validates the structure of rule_groups and includes the necessary return True statement for valid data. The changes are well-implemented and improve both the security and correctness of the codebase.

abhimehro · 2026-02-28T08:38:19Z

🤖 Automated PR Review — Closing as duplicate

Duplicate of #435 — both fix the same TOCTOU vulnerability in cache file creation. #435 is the newer, cleaner implementation based on a more recent main. Closing.

google-labs-jules · 2026-02-28T08:39:06Z

🤖 Automated PR Review — Closing as duplicate

Duplicate of #435 — both fix the same TOCTOU vulnerability in cache file creation. #435 is the newer, cleaner implementation based on a more recent main. Closing.

Understood. Acknowledging that this PR is closed as a duplicate of #435 and stopping work on this task.

Security: Fix TOCTOU race condition in cache file creation

448e057

Co-authored-by: abhimehro <84992105+abhimehro@users.noreply.github.com>

github-actions bot added the python label Feb 26, 2026

github-advanced-security bot found potential problems Feb 26, 2026

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main.py

return True

Check warning

Code scanning / Prospector (reported by Codacy)

Use lazy % formatting in logging functions (logging-fstring-interpolation) Warning

Use lazy % formatting in logging functions (logging-fstring-interpolation)

github-advanced-security bot found potential problems Feb 26, 2026

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gemini-code-assist bot reviewed Feb 26, 2026

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abhimehro closed this Feb 28, 2026

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🛡️ Sentinel: Fix TOCTOU vulnerability in cache creation#428

🛡️ Sentinel: Fix TOCTOU vulnerability in cache creation#428
abhimehro wants to merge 1 commit intomainfrom
security/fix-toctou-cache-creation-6458894056978274991

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