Security Skill

Load with: base.md

Security best practices and automated security testing for all projects.

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Core Principle

Security is not optional. Every project must pass security checks before merge. Assume all input is malicious, all secrets will leak if committed, and all dependencies have vulnerabilities.

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Required Security Setup

1. Gitignore (Non-Negotiable)

Every project must have these in .gitignore:

# Environment files - NEVER commit
.env
.env.*
!.env.example

# Secrets
*.pem
*.key
*.p12
*.pfx
credentials.json
secrets.json
*-credentials.json
service-account*.json

# IDE and OS
.idea/
.vscode/settings.json
.DS_Store
Thumbs.db

# Dependencies
node_modules/
__pycache__/
*.pyc
.venv/
venv/

# Build outputs
dist/
build/
*.egg-info/

# Logs that might contain sensitive data
*.log
logs/

2. Environment Variables

Create .env.example with all required vars (no values):

# .env.example - Copy to .env and fill in values

# Server-side only (NEVER prefix with VITE_ or NEXT_PUBLIC_)
DATABASE_URL=
ANTHROPIC_API_KEY=
SUPABASE_SERVICE_ROLE_KEY=

# Client-side safe (public, non-sensitive)
VITE_SUPABASE_URL=
VITE_SUPABASE_ANON_KEY=

Frontend Environment Variables (Critical!)

NEVER put secrets in client-exposed env vars:

// WRONG - Secret exposed to browser bundle!
const apiKey = import.meta.env.VITE_ANTHROPIC_API_KEY;

// CORRECT - Only public values client-side
const supabaseUrl = import.meta.env.VITE_SUPABASE_URL;

// CORRECT - Secrets stay server-side only
// In API route or server function:
const apiKey = process.env.ANTHROPIC_API_KEY;

Vercel Environment Variables:

• In Vercel dashboard, secrets without VITE_ prefix are server-only
• Only VITE_* vars are bundled into client code
• Always verify in browser devtools → Sources → your bundle that secrets aren't exposed

Validate environment at startup:

// config/env.ts
import { z } from 'zod';

const envSchema = z.object({
  DATABASE_URL: z.string().url(),
  ANTHROPIC_API_KEY: z.string().min(1),
  NODE_ENV: z.enum(['development', 'production', 'test']),
});

export const env = envSchema.parse(process.env);

# config/env.py
from pydantic_settings import BaseSettings

class Settings(BaseSettings):
    database_url: str
    anthropic_api_key: str
    environment: str = "development"

    class Config:
        env_file = ".env"

settings = Settings()

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Security Tests

Pre-Commit Security Checks

Add to pre-commit hooks:

For all projects:

# .pre-commit-config.yaml (add to existing)
repos:
  # Detect secrets
  - repo: https://github.com/Yelp/detect-secrets
    rev: v1.4.0
    hooks:
      - id: detect-secrets
        args: ['--baseline', '.secrets.baseline']

  # Check for security issues in dependencies
  - repo: local
    hooks:
      - id: security-check
        name: security-check
        entry: ./scripts/security-check.sh
        language: script
        pass_filenames: false

TypeScript/JavaScript:

// package.json scripts
{
  "scripts": {
    "security:audit": "npm audit --audit-level=high",
    "security:secrets": "npx secretlint '**/*'",
    "security:deps": "npx better-npm-audit audit"
  }
}

Python:

# Add to dev dependencies
pip install safety bandit

# Commands
safety check           # Check dependencies for vulnerabilities
bandit -r src/        # Static security analysis

Security Check Script

Create scripts/security-check.sh:

#!/bin/bash
set -e

echo "Running security checks..."

# Check for secrets in staged files
echo "Checking for secrets..."
if command -v detect-secrets &> /dev/null; then
  detect-secrets scan --baseline .secrets.baseline
fi

# Check .env is not staged
if git diff --cached --name-only | grep -E '^\.env$|^\.env\.' | grep -v '\.example$'; then
  echo "ERROR: .env file is staged for commit!"
  exit 1
fi

# Check for common secret patterns in staged files
STAGED_FILES=$(git diff --cached --name-only --diff-filter=ACM)
if echo "$STAGED_FILES" | xargs grep -l -E '(password|secret|api_key|apikey|token|private_key)\s*[:=]\s*["\047][^"\047]+["\047]' 2>/dev/null; then
  echo "ERROR: Possible secrets found in staged files!"
  exit 1
fi

# Language-specific checks
if [ -f "package.json" ]; then
  echo "Checking npm dependencies..."
  npm audit --audit-level=high || echo "Warning: npm audit found issues"
fi

if [ -f "pyproject.toml" ] || [ -f "requirements.txt" ]; then
  echo "Checking Python dependencies..."
  if command -v safety &> /dev/null; then
    safety check || echo "Warning: safety found issues"
  fi
fi

echo "Security checks passed!"

chmod +x scripts/security-check.sh

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