security-review

Security Review Skill

This skill ensures all code follows security best practices and identifies potential vulnerabilities.

When to Activate

• Implementing authentication or authorization
• Handling user input or file uploads
• Creating new API endpoints
• Working with secrets or credentials
• Implementing payment features
• Storing or transmitting sensitive data
• Integrating third-party APIs

Security Checklist

1. Secrets Management

NEVER Do This

const apiKey = "sk-proj-xxxxx"  // Hardcoded secret
const dbPassword = "password123" // In source code

ALWAYS Do This

const apiKey = process.env.OPENAI_API_KEY
const dbUrl = process.env.DATABASE_URL

// Verify secrets exist
if (!apiKey) {
  throw new Error('OPENAI_API_KEY not configured')
}

Verification Steps

• No hardcoded API keys, tokens, or passwords
• All secrets in environment variables
• .env.local in .gitignore
• No secrets in git history
• Production secrets in hosting platform

2. Input Validation

Always Validate User Input

import { z } from 'zod'

const CreateUserSchema = z.object({
  email: z.string().email(),
  name: z.string().min(1).max(100),
  age: z.number().int().min(0).max(150)
})

export async function createUser(input: unknown) {
  try {
    const validated = CreateUserSchema.parse(input)
    return await db.users.create(validated)
  } catch (error) {
    if (error instanceof z.ZodError) {
      return { success: false, errors: error.errors }
    }
    throw error
  }
}

File Upload Validation

function validateFileUpload(file: File) {
  const MAX_SIZE = 5 * 1024 * 1024
  if (file.size > MAX_SIZE) {
    throw new Error('File too large (max 5MB)')
  }

  const ALLOWED_TYPES = ['image/jpeg', 'image/png', 'image/gif']
  if (!ALLOWED_TYPES.includes(file.type)) {
    throw new Error('Invalid file type')
  }

  return true
}

3. SQL Injection Prevention

NEVER Concatenate SQL

// DANGEROUS
const query = `SELECT * FROM users WHERE email = '${userEmail}'`

ALWAYS Use Parameterized Queries

// Safe - parameterized query
const { data } = await supabase
  .from('users')
  .select('*')
  .eq('email', userEmail)

// Or with raw SQL
await db.query(
  'SELECT * FROM users WHERE email = $1',
  [userEmail]
)

4. Authentication & Authorization

JWT Token Handling

// WRONG: localStorage (vulnerable to XSS)
localStorage.setItem('token', token)

// CORRECT: httpOnly cookies
res.setHeader('Set-Cookie',
  `token=${token}; HttpOnly; Secure; SameSite=Strict; Max-Age=3600`)

Authorization Checks

export async function deleteUser(userId: string, requesterId: string) {
  const requester = await db.users.findUnique({
    where: { id: requesterId }
  })

  if (requester.role !== 'admin') {
    return NextResponse.json(
      { error: 'Unauthorized' },
      { status: 403 }
    )
  }

  await db.users.delete({ where: { id: userId } })
}

5. XSS Prevention

Sanitize HTML

import DOMPurify from 'isomorphic-dompurify'

function renderUserContent(html: string) {
  const clean = DOMPurify.sanitize(html, {
    ALLOWED_TAGS: ['b', 'i', 'em', 'strong', 'p'],
    ALLOWED_ATTR: []
  })
  return <div dangerouslySetInnerHTML={{ __html: clean }} />
}

6. CSRF Protection

CSRF Tokens

export async function POST(request: Request) {
  const token = request.headers.get('X-CSRF-Token')

  if (!csrf.verify(token)) {
    return NextResponse.json(
      { error: 'Invalid CSRF token' },
      { status: 403 }
    )
  }

  // Process request
}

7. Rate Limiting

import rateLimit from 'express-rate-limit'

const limiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 100,
  message: 'Too many requests'
})

app.use('/api/', limiter)

8. Sensitive Data Exposure

Logging

// WRONG: Logging sensitive data
console.log('User login:', { email, password })

// CORRECT: Redact sensitive data
console.log('User login:', { email, userId })

Error Messages

// WRONG: Exposing internal details
catch (error) {
  return NextResponse.json(
    { error: error.message, stack: error.stack },
    { status: 500 }
  )
}

// CORRECT: Generic error messages
catch (error) {
  console.error('Internal error:', error)
  return NextResponse.json(
    { error: 'An error occurred. Please try again.' },
    { status: 500 }
  )
}

9. Dependency Security

# Check for vulnerabilities
npm audit

# Fix automatically fixable issues
npm audit fix

# Always commit lock files
git add package-lock.json

Security Testing

test('requires authentication', async () => {
  const response = await fetch('/api/protected')
  expect(response.status).toBe(401)
})

test('requires admin role', async () => {
  const response = await fetch('/api/admin', {
    headers: { Authorization: `Bearer ${userToken}` }
  })
  expect(response.status).toBe(403)
})

test('rejects invalid input', async () => {
  const response = await fetch('/api/users', {
    method: 'POST',
    body: JSON.stringify({ email: 'not-an-email' })
  })
  expect(response.status).toBe(400)
})

Pre-Deployment Security Checklist

• Secrets: No hardcoded secrets, all in env vars
• Input Validation: All user inputs validated
• SQL Injection: All queries parameterized
• XSS: User content sanitized
• CSRF: Protection enabled
• Authentication: Proper token handling
• Authorization: Role checks in place
• Rate Limiting: Enabled on all endpoints
• HTTPS: Enforced in production
• Security Headers: CSP, X-Frame-Options configured
• Error Handling: No sensitive data in errors
• Logging: No sensitive data logged
• Dependencies: Up to date, no vulnerabilities

Resources

• OWASP Top 10
• Web Security Academy

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Remember: Security is not optional. One vulnerability can compromise the entire platform. When in doubt, err on the side of caution.