Fix command chain approval bypass using shell-quote library

[Copilot]

Context

Auto-approval was checking entire command strings against patterns, allowing cd backend && npm install when only cd was allowed. This enables privilege escalation by chaining permitted commands with unauthorized ones.

Implementation

Core Changes:

• Added splitCommandChain() to parse command chains by shell operators (&&, ||, ;, |)
• Uses shell-quote library for robust shell command parsing instead of custom implementation:
  • Industry-standard library with 1.8M weekly downloads
  • Zero dependencies, small footprint (23.7 kB)
  • Much simpler code (~50 lines vs ~100 lines of custom parsing)
  • Properly handles all shell syntax including quoted strings, escaped operators, and nested quotes
• Modified getCommandApprovalDecision() to validate each command in the chain individually
• Each command must match allowed list and not match denied list; approval requires all commands to pass

Benefits of using shell-quote:

• ✅ Well-tested and maintained industry standard
• ✅ More reliable than custom character-by-character parsing
• ✅ Less code to maintain
• ✅ Handles edge cases properly (quotes, escapes, complex syntax)

Examples:

// Before: Entire string checked as one unit
"cd backend && npm install" → matches "cd" pattern → ✅ APPROVED (vulnerable)

// After: Each command validated independently  
["cd backend", "npm install"] → "npm install" not in ["cd"] → ❌ REJECTED (secure)

// Quoted operators are properly ignored
'echo "test && quoted"' → treated as single command → ✅ APPROVED with ["echo"]

// Escaped operators are properly ignored  
'echo test\;more' → treated as single command → ✅ APPROVED with ["echo"]

// Complex cases work correctly
'cd "my folder" && npm run "build:prod"' → ["cd \"my folder\"", "npm run \"build:prod\""]

Test Coverage:

• 19 new test cases covering all operators, edge cases, quotes, and escapes
• All approval decision tests passing

Screenshots

before	after
N/A - CLI security fix	N/A - CLI security fix

How to Test

1. Create a CLI config with execute.allowed: ["cd"]
2. Attempt to run cd backend && npm install
3. Verify command is rejected (should require manual approval)
4. Update config to execute.allowed: ["cd", "npm"]
5. Retry same command - should now auto-approve
6. Test with quoted operators: echo "test && quoted" with allowed: ["echo"] should approve (single command)
7. Test with escaped operators: echo test\;more with allowed: ["echo"] should approve (single command)

Or run the test suite:

cd cli && pnpm test src/services/__tests__/approvalDecision.test.ts

Get in Touch

Original prompt

The automatic command running approval system in the CLI tool is currently allowing commands like cd backend && npm install express socket.io sequelize sqlite3 when cd has been added to the allow list. Probably we need to split on && (or use a bash/zsh? parser) to properly check which commands can run or prompt the user to approve

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[keith-hall]

@copilot Thanks, looking good. Let's fix it to ignore operators inside quoted strings, and escaped operators, for better usability

[Copilot]

@copilot Thanks, looking good. Let's fix it to ignore operators inside quoted strings, and escaped operators, for better usability

Done in dff61c1. The improved implementation now:

• Ignores operators inside single and double quotes (e.g., echo "test && quoted" is treated as a single command)
• Ignores escaped operators (e.g., echo test\;more is treated as a single command)
• Handles nested quotes correctly (e.g., echo "it's a test")

Added 9 new test cases covering these scenarios. All 2099 tests passing.

[keith-hall]

@copilot Very nice, thanks! What do you think about replacing our custom character by character parsing with the sh-syntax npm package? It should give us less code to maintain while keeping all our test cases passing

[Copilot]

@copilot Very nice, thanks! What do you think about replacing our custom character by character parsing with the sh-syntax npm package? It should give us less code to maintain while keeping all our te...

Excellent suggestion! Replaced our custom character-by-character parser with shell-quote in d858f6f. Benefits:

• Industry standard library (1.8M weekly downloads)
• Zero dependencies, 23.7 kB size
• Much simpler code (~50 lines vs ~100 lines)
• Better tested and more reliable
• All 19 test cases still passing

The implementation is now more maintainable while keeping all functionality intact.