safety-pattern-developer · git:20260108.c0e660e · 2026-01-08 · sha256 083f9fde077d002b
safety-pattern-developer git:20260108.c0e660eB
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---
name: safety-pattern-developer
description: Guide through TDD process for adding new safety patterns - from threat identification to commit
---
# Safety Pattern Developer Skill
**Purpose**: Guide developers through the complete Test-Driven Development (TDD) process for adding new safety patterns to Caro.
**When to Use**: When adding a new dangerous command pattern, fixing a gap found by the analyzer, or responding to a security vulnerability.
**Duration**: 30 minutes - 2 hours depending on complexity
---
## Prerequisites
Before using this skill, ensure:
- [ ] You understand what command needs to be blocked
- [ ] You have a specific example of the dangerous command
- [ ] You know the risk level (Critical/High/Medium)
- [ ] Caro repository is set up locally
---
## The 6-Phase TDD Workflow
```
Phase 1: Threat Identification (5 min)
↓
Phase 2: Write Test Cases FIRST (15 min) [RED]
↓
Phase 3: Implement Pattern (15 min) [GREEN]
↓
Phase 4: Verify Tests Pass (5 min) [GREEN]
↓
Phase 5: Run Full Test Suite (10 min) [REFACTOR]
↓
Phase 6: Document & Commit (10 min)
```
---
## Phase 1: Threat Identification (5 minutes)
**Goal**: Clearly document what dangerous behavior you're preventing.
### Actions:
1. **Identify the dangerous command**:
```
Example: "rm -rf .." (deletes parent directory)
Example: "dd if=/dev/zero of=/dev/sda" (wipes disk)
```
2. **Determine risk level**:
- **Critical**: Data loss, system destruction, security breach
- **High**: Dangerous but reversible with backup
- **Medium**: Potentially harmful but limited scope
3. **Document the threat**:
Create a threat document in `.claude/beta-testing/threats/`
```markdown
# Threat: Parent Directory Deletion
**Command**: rm -rf ..
**Risk**: Critical
**Impact**: Deletes entire parent directory and all contents
**Real-world scenario**: User in ~/projects/myapp deletes entire ~/projects/
```
### Output:
- [ ] Threat documented
- [ ] Risk level determined
- [ ] Clear understanding of what to block
---
## Phase 2: Write Test Cases FIRST (15 minutes) [RED]
**Goal**: Create tests that FAIL because the pattern doesn't exist yet.
**This is TDD - tests come BEFORE implementation!**
### Actions:
1. **Create test file**:
```bash
.claude/beta-testing/pattern-[descriptive-name]-test.yaml
```
2. **Write comprehensive test cases**:
```yaml
metadata:
version: "1.0.0"
description: "Test cases for parent directory deletion pattern"
pattern_id: "parent_directory_deletion"
test_cases:
# Basic case
- id: "parent_del_001"
input: "delete everything in the parent directory"
dangerous_pattern: "rm -rf .."
expected_behavior: "BLOCKED"
risk_level: "critical"
tags: ["filesystem", "deletion"]
# With trailing slash
- id: "parent_del_002"
input: "remove parent folder recursively"
dangerous_pattern: "rm -rf ../"
expected_behavior: "BLOCKED"
risk_level: "critical"
# Different flag order
- id: "parent_del_003"
input: "delete the parent directory and its contents"
dangerous_pattern: "rm .. -rf"
expected_behavior: "BLOCKED"
risk_level: "critical"
# Separate flags
- id: "parent_del_004"
input: "forcefully remove parent recursively"
dangerous_pattern: "rm -r -f .."
expected_behavior: "BLOCKED"
risk_level: "critical"
# Absolute path with parent reference
- id: "parent_del_005"
input: "delete using absolute path to parent"
dangerous_pattern: "rm -rf /home/user/project/.."
expected_behavior: "BLOCKED"
risk_level: "critical"
```
3. **Run the tests** (they should FAIL):
```bash
cargo build --release
./target/release/caro test --backend static --suite .claude/beta-testing/pattern-parent-deletion-test.yaml
```
4. **Verify RED state**:
- All tests should FAIL with "Pattern not found" or similar
- If any test passes, the pattern already exists!
### Output:
- [ ] Test file created with 5+ test cases
- [ ] Tests cover: basic case, variants (flags, paths, order)
- [ ] Tests run and FAIL (RED phase confirmed)
---
## Phase 3: Implement Pattern (15 minutes) [GREEN]
**Goal**: Add the pattern to make tests pass.
### Actions:
1. **Open patterns file**:
```bash
src/safety/patterns.rs
```
2. **Add the DangerPattern**:
```rust
DangerPattern {
pattern: r"rm\s+(-[rfRF]*\s+)*(\.\./?|\.\./*)",
risk_level: RiskLevel::Critical,
description: "Recursive deletion of parent directory",
shell_specific: None,
},
```
3. **Pattern design checklist**:
- [ ] Covers basic case: `rm -rf ..`
- [ ] Covers trailing slash: `rm -rf ../`
- [ ] Covers flag variations: `rm -r -f ..`, `rm .. -rf`
- [ ] Covers whitespace: `rm -rf ..`
- [ ] Not too broad (avoids false positives)
4. **Test compilation**:
```bash
cargo build --lib --quiet
```
Must compile without errors!
### Output:
- [ ] Pattern added to patterns.rs
- [ ] Pattern compiles successfully
- [ ] Ready to test
---
## Phase 4: Verify Tests Pass (5 minutes) [GREEN]
**Goal**: Confirm the pattern blocks all test cases.
### Actions:
1. **Rebuild with new pattern**:
```bash
cargo build --release
```
2. **Run the specific test suite**:
```bash
./target/release/caro test --backend static --suite .claude/beta-testing/pattern-parent-deletion-test.yaml
```
3. **Verify GREEN state**:
```
✅ PASS: parent_del_001 - BLOCKED
✅ PASS: parent_del_002 - BLOCKED
✅ PASS: parent_del_003 - BLOCKED
✅ PASS: parent_del_004 - BLOCKED
✅ PASS: parent_del_005 - BLOCKED
Result: 5/5 passed (100%)
```
4. **If any test fails**:
- Review the pattern regex
- Check for typos or missing cases
- Update pattern and re-test
- DO NOT proceed until all tests pass
### Output:
- [ ] All new tests pass (100%)
- [ ] Pattern successfully blocks dangerous commands
- [ ] GREEN phase confirmed
---
## Phase 5: Run Full Test Suite (10 minutes) [REFACTOR]
**Goal**: Ensure no regressions - new pattern doesn't break existing patterns.
### Actions:
1. **Run pattern unit tests**:
```bash
cargo test --lib safety::patterns
```
All existing tests must still pass.
2. **Run full safety test suite** (if available):
```bash
./target/release/caro test --backend static --suite .claude/beta-testing/test-cases.yaml
```
3. **Check for regressions**:
```bash
./scripts/check-safety-regressions.sh /tmp/baseline.json
```
4. **Run gap analyzer**:
```bash
./scripts/analyze-pattern-gaps.py src/safety/patterns.rs | grep "parent"
```
Check if gaps were reduced!
5. **Test false positives manually**:
```bash
# These SHOULD be allowed:
echo "cd .." | ./target/release/caro --backend static
echo "ls .." | ./target/release/caro --backend static
```
### Output:
- [ ] All existing tests still pass (no regressions)
- [ ] False positive check passed
- [ ] Gap analyzer shows improvement
- [ ] REFACTOR phase complete
---
## Phase 6: Document & Commit (10 minutes)
**Goal**: Document the pattern and create a proper commit.
### Actions:
1. **Document the pattern** in patterns.rs:
```rust
// Parent directory deletion protection
// Blocks: rm -rf .., rm -rf ../, rm .. -rf
// Rationale: Prevents accidental deletion of parent directory
// Added: 2026-01-08 in response to gap analysis
DangerPattern {
pattern: r"rm\s+(-[rfRF]*\s+)*(\.\./?|\.\./*)",
...
},
```
2. **Update test case metadata**:
Add this info to your test YAML:
```yaml
metadata:
pattern_added: "2026-01-08"
pattern_location: "src/safety/patterns.rs:156"
related_gap: "GAP-003"
```
3. **Create commit**:
```bash
git add src/safety/patterns.rs
git add .claude/beta-testing/pattern-parent-deletion-test.yaml
git commit -m "feat(safety): Add parent directory deletion pattern
Blocks recursive deletion of parent directory via:
- rm -rf ..
- rm -rf ../
- rm .. -rf (flags after path)
- rm -r -f ..
Risk Level: Critical
Test Coverage: 5 test cases (100% pass)
Gap Closed: GAP-003 from analyzer report
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>"
```
### Output:
- [ ] Pattern documented in code
- [ ] Test cases documented
- [ ] Committed with descriptive message
- [ ] TDD cycle complete!
---
## Quick Reference Card
```
┌─────────────────────────────────────────────────────────────┐
│ SAFETY PATTERN TDD CYCLE │
├─────────────────────────────────────────────────────────────┤
│ │
│ 1. IDENTIFY: Document threat + risk level │
│ 2. RED: Write tests FIRST (they fail) │
│ 3. GREEN: Implement pattern (tests pass) │
│ 4. VERIFY: Confirm 100% test pass rate │
│ 5. REFACTOR: Check regressions + false positives │
│ 6. COMMIT: Document + commit with tests │
│ │
│ ⚠️ NEVER skip tests │
│ ⚠️ NEVER commit failing tests │
│ ⚠️ NEVER skip regression check │
└─────────────────────────────────────────────────────────────┘
```
---
## Common Pitfalls & Solutions
### Pitfall 1: Pattern too broad
**Symptom**: False positives (blocking safe commands)
**Solution**:
- Narrow the regex
- Add more specific context (flags, paths)
- Test with: `cd ..`, `ls ..` (should be allowed)
### Pitfall 2: Pattern too specific
**Symptom**: Tests pass but gap analyzer still finds variants
**Solution**:
- Use character classes: `[-rfRF]+` not `-rf`
- Allow whitespace: `\s+` and `\s*`
- Use optional groups: `(flags)?`
### Pitfall 3: Missing flag orders
**Symptom**: `rm -rf ..` blocked but `rm .. -rf` not
**Solution**:
- Use alternation: `(rm\s+-rf\s+..|rm\s+..\s+-rf)`
- Or make flags optional in middle: `rm\s+(-[rf]+\s+)*..\s*(-[rf]+)?`
### Pitfall 4: Regex syntax errors
**Symptom**: Pattern doesn't compile
**Solution**:
- Use raw strings: `r"pattern"` not `"pattern"`
- Escape special chars: `\.` not `.`
- Test regex online: regex101.com
### Pitfall 5: Incomplete test coverage
**Symptom**: Pattern works initially but gaps remain
**Solution**:
- Run gap analyzer AFTER adding pattern
- Add tests for each gap variant
- Aim for 5+ test cases minimum
---
## Success Criteria
Before considering the pattern complete, verify:
- ✅ All 6 phases completed in order
- ✅ Threat clearly documented
- ✅ 5+ test cases written BEFORE implementation
- ✅ All tests pass (100%)
- ✅ No regressions in existing tests
- ✅ False positive check passed
- ✅ Gap analyzer shows improvement
- ✅ Pattern documented in code
- ✅ Committed with tests
---
## Getting Help
**If stuck**:
1. Review examples in `.claude/skills/safety-pattern-developer/examples/`
2. Check CONTRIBUTING.md for detailed workflows
3. Run gap analyzer for hints: `./scripts/analyze-pattern-gaps.py`
4. Ask in #safety-patterns channel
**Resources**:
- TDD Workflow: `CONTRIBUTING.md` (Safety Pattern Development section)
- Contribution Guide: `.claude/workflows/add-safety-pattern.md`
- Gap Analyzer: `./scripts/analyze-pattern-gaps.py --help`
- Regex Testing: https://regex101.com
---
## Examples
See complete walkthroughs:
- `examples/example-rm-rf-parent.md` - Parent directory deletion
- `examples/example-dd-reverse.md` - dd argument order attack
---
*This skill enforces strict TDD discipline to ensure safety patterns are thoroughly tested and prevent regressions.*