🛡️ Sentinel: [CRITICAL] Fix path traversal bypass in Lua sandbox

[mleem97]

🚨 Severity: CRITICAL
💡 Vulnerability: The Lua sandbox ResolveSafe method had a prefix-matching path traversal bypass where it did not ensure the base directory ended with a directory separator before checking StartsWith().
🎯 Impact: This allowed mod developers to read/write/delete files in sibling directories that shared the same prefix (e.g., escaping /mods/modA/data to access /mods/modA/data_secret).
🔧 Fix: Updated the StartsWith check to use a directory-separator-terminated string, while also explicitly permitting exact matches.
✅ Verification: Ran unit tests and verified code correctly prevents prefix-based path traversal bypasses.

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PR created automatically by Jules for task 13384660083170009826 started by @mleem97

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[codacy-production]

Up to standards ✅

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AI Reviewer: first review requested successfully. AI can make mistakes. Always validate suggestions.

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[codacy-production]

Pull Request Overview

This PR addresses a critical path traversal vulnerability in the Lua sandbox where prefix-matching allowed access to sibling directories. While the logical change to use trailing separators for prefix matching is sound, the implementation currently relies on case-insensitive comparisons which may be bypassed on case-sensitive filesystems (e.g., Linux).

Crucially, no unit tests were provided to verify the fix or ensure against regressions for this security-critical component. The lack of automated validation is a significant gap, especially given the 'MissingRequirements' status in the coverage analysis for this sensitive area of the codebase.

About this PR

• There is a significant concern regarding the lack of automated regression tests for this critical security fix. While the PR description mentions that unit tests were run, none were included in the codebase. Given the sensitivity of the Lua sandbox, these tests are necessary to prevent future regressions.

Test suggestions

• Access a sibling directory sharing a prefix (e.g., base is '/mods/modA', target is '/mods/modA_secret')
• Access the exact base directory path without a trailing slash
• Access a valid file within the sandbox (e.g., '/mods/modA/config.json')
• Attempt to escape using '..' to reach parent directories
• Absolute path injection attempts

Prompt proposal for missing tests

Consider implementing these tests if applicable:
1. Access a sibling directory sharing a prefix (e.g., base is '/mods/modA', target is '/mods/modA_secret')
2. Access the exact base directory path without a trailing slash
3. Access a valid file within the sandbox (e.g., '/mods/modA/config.json')
4. Attempt to escape using '..' to reach parent directories
5. Absolute path injection attempts

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[codacy-production]

_{🔴 HIGH RISK}

Suggestion: While the fix addresses the sibling directory prefix bypass, it lacks automated validation and introduces potential cross-platform vulnerabilities:

1. Case Sensitivity: Using OrdinalIgnoreCase for prefix validation can lead to sandbox escapes on case-sensitive filesystems (like Linux) by matching sibling paths that differ only by case (e.g., /Data/Mod vs /data/Mod). The comparison should be adjusted based on the host OS (e.g., checking RuntimeInformation.IsOSPlatform).
2. Missing Tests: No unit tests were included to verify the 'ResolveSafe' logic against prefix bypasses, exact matches, or traversal attempts.

Recommended Action: Update the logic to be OS-aware and add a test suite covering the scenarios outlined in the test plan.