fix(policy): enhance shell command safety and parsing

[allenhutchison]

Addressing feedback from PR #15006.

Changes:

• Implemented recursive checking for shell command substitutions (e.g., echo $(rm -rf /)).
• Enforced stricter validation for chained commands.
• Added fail-safe mechanisms: if command parsing fails, the decision defaults to ASK_USER.
• Refactored toml-loader for better testability.
• Added comprehensive tests for command injection and substitution scenarios.

[gemini-code-assist[bot]]

Summary of Changes

Hello @allenhutchison, I'm Gemini Code Assist[^1]! 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 significantly enhances the security and robustness of the policy engine's handling of shell commands. It introduces advanced parsing capabilities to detect and prevent various forms of command injection and substitution, ensuring that only explicitly allowed commands and their sub-components are executed. The changes also include a critical fail-safe mechanism to handle unparseable commands securely, alongside refactoring for better maintainability and comprehensive new tests to validate these security improvements.

Highlights

• Enhanced Shell Command Safety: Implemented recursive checking for shell command substitutions (e.g., echo $(rm -rf /)) and enforced stricter validation for chained commands (e.g., cmd1; cmd2).
• Fail-Safe Mechanism: Introduced a fail-safe where if shell command parsing fails, the policy decision defaults to ASK_USER to prevent unsafe execution of unparseable commands.
• Improved Testability and Modularity: Refactored the toml-loader module by extracting argsPattern building logic into a dedicated helper function, improving code organization and testability.
• Comprehensive Test Coverage: Added extensive new test cases to cover various command injection and substitution scenarios, ensuring robust validation of shell commands.

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[github-actions[bot]]

Size Change: +152 B (0%)

Total Size: 21.6 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	21.6 MB	+152 B (0%)
./bundle/sandbox-macos-permissive-closed.sb	1.03 kB	0 B
./bundle/sandbox-macos-permissive-open.sb	890 B	0 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB	0 B
./bundle/sandbox-macos-restrictive-closed.sb	3.29 kB	0 B
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B

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