Skill: Semgrep Analyze

Analyze code with Semgrep and plan fixes for identified issues.

Usage

/semgrep-analyze [path] [--rules <ruleset>]

Arguments:

path - Directory or file to analyze (default: current directory)
--rules - Semgrep ruleset to use (default: auto)

Examples:

/semgrep-analyze
/semgrep-analyze src/
/semgrep-analyze --rules p/security-audit
/semgrep-analyze src/utils --rules p/javascript

Process

1. Check Semgrep Installation

First, verify semgrep is installed:

semgrep --version

If not installed, install via pip (recommended):

# Install semgrep via pip
pip install semgrep

# Or via pipx for isolated environment
pipx install semgrep

# Or via Homebrew on macOS
brew install semgrep

2. Run Semgrep Analysis

Run semgrep with appropriate rules:

# Auto-detect language and use recommended rules
semgrep scan --config auto .

# Use specific ruleset
semgrep scan --config p/javascript .
semgrep scan --config p/typescript .
semgrep scan --config p/security-audit .
semgrep scan --config p/owasp-top-ten .

# Output as JSON for parsing
semgrep scan --config auto --json -o semgrep-results.json .

# Scan specific directory
semgrep scan --config auto src/

3. Common Rulesets

| Ruleset | Description | |---------|-------------| | auto | Auto-detect language, use recommended rules | | p/javascript | JavaScript-specific rules | | p/typescript | TypeScript-specific rules | | p/react | React-specific rules | | p/nodejs | Node.js security rules | | p/security-audit | General security audit | | p/owasp-top-ten | OWASP Top 10 vulnerabilities | | p/ci | Rules suitable for CI/CD | | p/default | Semgrep default ruleset |

4. Analyze Results

For each finding, document:

Rule ID - The semgrep rule that triggered
Severity - ERROR, WARNING, INFO
Location - File and line number
Message - Description of the issue
Code snippet - The problematic code

5. Plan Fixes

For each issue, create a fix plan:

## Issue: [Rule ID]

**Severity:** [ERROR/WARNING/INFO]
**File:** [path:line]

**Problem:**
[Description of the issue]

**Current Code:**
```[language]
[code snippet]

Proposed Fix:

[fixed code]

Rationale: [Why this fix addresses the issue]


### 6. Prioritize Fixes

Order fixes by:

1. **Critical** - Security vulnerabilities, data exposure
2. **High** - Bugs that could cause runtime errors
3. **Medium** - Code quality issues, potential bugs
4. **Low** - Style issues, minor improvements

## Example Workflow

```bash
# 1. Check installation
semgrep --version

# 2. If not installed
pip install semgrep

# 3. Run scan
semgrep scan --config auto --json -o semgrep-results.json .

# 4. View summary
semgrep scan --config auto . 2>&1 | tail -20

# 5. Scan specific areas if needed
semgrep scan --config p/security-audit src/

Output Format

After analysis, provide:

Summary - Total findings by severity
Critical Issues - Detailed breakdown of critical/high issues
Fix Plan - Prioritized list of fixes with code changes
Verification - Commands to verify fixes

Semgrep Configuration

Create .semgrep.yml for custom rules or to ignore paths:

# .semgrep.yml
rules: []

# Or reference external rules
# rules:
#   - p/javascript
#   - p/security-audit

# Ignore paths
# paths:
#   exclude:
#     - node_modules
#     - dist
#     - "*.test.js"

Common Fixes by Category

Security

| Issue | Fix | |-------|-----| | Hardcoded secrets | Move to environment variables | | SQL injection | Use parameterized queries | | XSS vulnerability | Sanitize user input | | Insecure randomness | Use crypto.randomUUID() |

Code Quality

| Issue | Fix | |-------|-----| | Unused variables | Remove or prefix with _ | | Missing error handling | Add try/catch or error callbacks | | Deprecated API usage | Update to modern API | | Inefficient patterns | Refactor to optimal approach |

React/Svelte Specific

| Issue | Fix | |-------|-----| | Missing key prop | Add unique key to list items | | Direct DOM manipulation | Use framework methods | | Memory leaks | Clean up subscriptions/listeners | | Unsafe innerHTML | Use safe rendering methods |

Integration with Quality Gates

After fixing issues:

# Verify fixes
semgrep scan --config auto .

# Run existing quality gates
pnpm test && pnpm build && pnpm lint

Troubleshooting

Semgrep not found

# Check if pip is available
pip --version

# If pip not found, install Python first
# macOS: brew install python
# Ubuntu: sudo apt install python3-pip

# Then install semgrep
pip install semgrep

Rate limiting

# Login to avoid rate limits
semgrep login

# Or use offline mode with local rules
semgrep scan --config ./local-rules.yml .

Memory issues on large codebases

# Scan specific directories
semgrep scan --config auto src/

# Exclude large directories
semgrep scan --config auto --exclude node_modules --exclude dist .

Done Criteria

[ ] Semgrep installed and working
[ ] Full scan completed
[ ] All findings documented
[ ] Fix plan created for each issue
[ ] Critical/high issues addressed
[ ] Verification scan shows no regressions
[ ] Quality gates still pass