fix(terminal-security): prevent newline bypass in command validation

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Summary

Fixes a security vulnerability where an attacker could bypass the terminal command allow-list by using newline characters (\n, \r\n, \r) as command separators.

The Vulnerability

The shell-quote library treats literal newline characters as whitespace rather than command separators. This caused multiple newline-separated commands to be evaluated as a single command, allowing dangerous commands to be hidden after safe ones.

Attack Examples

• ls\nopen -a Calculator → Bypassed to allowedWithoutPermission (should require permission)
• ls\nnpm install malicious → Bypassed to allowedWithoutPermission (should require permission)
• echo hello\nopen -a Calculator → Bypassed to allowedWithoutPermission (should require permission)

The Fix

The solution splits input on line breaks (/\r?\n|\r/) before parsing with shell-quote, evaluating each line independently and returning the most restrictive policy.

Changes

• Source Code: Modified evaluateTerminalCommandSecurity() to split on newlines before parsing
• Tests: Added 32 comprehensive tests covering:
  • Critical commands with newline separators
  • High-risk commands with newline separators
  • All newline variations (\n, \r\n, \r)
  • Multiple commands on separate lines
  • Realistic attack scenarios
  • Edge cases (empty lines, whitespace, etc.)

Security Impact

✅ Fixed: Newline bypass for medium/high-risk commands
✅ Maintained: Critical commands (sudo, rm -rf /) still properly blocked
✅ Maintained: Existing security checks for semicolons, pipes, etc.

Testing

All 224 tests pass, including:

• 32 new tests for newline bypass scenarios
• 192 existing security tests remain passing

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This agent session was co-authored by nate and Continue.

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Summary by cubic

Prevents a newline-based bypass in terminal command validation by splitting input on line breaks and evaluating each line separately. Applies the most restrictive policy across lines to stop hidden dangerous commands.

• Bug Fixes
  • Blocks critical commands placed after safe ones via newline (e.g., sudo, rm -rf /).
  • Requires permission for high-risk commands after newline (e.g., npm install, curl, docker).
  • Supports Unix, Windows, and old Mac line endings; skips empty lines.
  • Added 32 tests for newline scenarios; all 224 tests pass.

^{Written for commit 28cdb4e. Summary will update automatically on new commits.}

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[cubic-dev-ai]

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