/owasp-security

name: owasp-security
description: Implement secure coding practices following OWASP Top 10. Use when preventing security vulnerabilities, implementing authentication, securing APIs, or conducting security reviews. Triggers on OWASP, security, XSS, SQL injection, CSRF, authentication security, secure coding, vulnerability.

OWASP Top 10 Security

Prevent common security vulnerabilities in web applications.

OWASP Top 10 (2021)

| # | Vulnerability | Prevention | |---|---------------|------------| | A01 | Broken Access Control | Proper authorization checks | | A02 | Cryptographic Failures | Strong encryption, secure storage | | A03 | Injection | Input validation, parameterized queries | | A04 | Insecure Design | Threat modeling, secure patterns | | A05 | Security Misconfiguration | Hardened configs, no defaults | | A06 | Vulnerable Components | Dependency scanning, updates | | A07 | Auth Failures | MFA, secure session management | | A08 | Data Integrity Failures | Input validation, signed updates | | A09 | Logging Failures | Comprehensive audit logs | | A10 | SSRF | URL validation, allowlists |

A01: Broken Access Control

Prevention Patterns

// ❌ BAD: No authorization check
app.get('/api/users/:id', async (req, res) => {
  const user = await db.users.findById(req.params.id);
  res.json(user);
});

// ✅ GOOD: Verify ownership
app.get('/api/users/:id', authenticate, async (req, res) => {
  const userId = req.params.id;
  
  // Users can only access their own data
  if (req.user.id !== userId && req.user.role !== 'admin') {
    return res.status(403).json({ error: 'Forbidden' });
  }
  
  const user = await db.users.findById(userId);
  res.json(user);
});

// ✅ GOOD: Role-based access control (RBAC)
const requireRole = (...roles: string[]) => {
  return (req: Request, res: Response, next: NextFunction) => {
    if (!roles.includes(req.user?.role)) {
      return res.status(403).json({ error: 'Insufficient permissions' });
    }
    next();
  };
};

app.delete('/api/posts/:id', authenticate, requireRole('admin', 'moderator'), deletePost);

Insecure Direct Object Reference (IDOR)

// ❌ BAD: Predictable IDs exposed
GET /api/invoices/1001
GET /api/invoices/1002  // Can enumerate others' invoices

// ✅ GOOD: Use UUIDs + ownership check
app.get('/api/invoices/:id', authenticate, async (req, res) => {
  const invoice = await db.invoices.findOne({
    id: req.params.id,
    userId: req.user.id,  // Enforce ownership
  });
  
  if (!invoice) {
    return res.status(404).json({ error: 'Not found' });
  }
  
  res.json(invoice);
});

A02: Cryptographic Failures

Password Hashing

import bcrypt from 'bcrypt';
import crypto from 'crypto';

// ✅ Hash passwords with bcrypt
const SALT_ROUNDS = 12;

async function hashPassword(password: string): Promise<string> {
  return bcrypt.hash(password, SALT_ROUNDS);
}

async function verifyPassword(password: string, hash: string): Promise<boolean> {
  return bcrypt.compare(password, hash);
}

// ✅ Secure token generation
function generateSecureToken(length = 32): string {
  return crypto.randomBytes(length).toString('hex');
}

// ✅ Encrypt sensitive data
const ALGORITHM = 'aes-256-gcm';
const KEY = crypto.scryptSync(process.env.ENCRYPTION_KEY!, 'salt', 32);

function encrypt(text: string): { encrypted: string; iv: string; tag: string } {
  const iv = crypto.randomBytes(16);
  const cipher = crypto.createCipheriv(ALGORITHM, KEY, iv);
  
  let encrypted = cipher.update(text, 'utf8', 'hex');
  encrypted += cipher.final('hex');
  
  return {
    encrypted,
    iv: iv.toString('hex'),
    tag: cipher.getAuthTag().toString('hex'),
  };
}

function decrypt(encrypted: string, iv: string, tag: string): string {
  const decipher = crypto.createDecipheriv(ALGORITHM, KEY, Buffer.from(iv, 'hex'));
  decipher.setAuthTag(Buffer.from(tag, 'hex'));
  
  let decrypted = decipher.update(encrypted, 'hex', 'utf8');
  decrypted += decipher.final('utf8');
  
  return decrypted;
}

Secure Headers

import helmet from 'helmet';

app.use(helmet());
app.use(helmet.hsts({ maxAge: 31536000, includeSubDomains: true }));
app.use(helmet.contentSecurityPolicy({
  directives: {
    defaultSrc: ["'self'"],
    scriptSrc: ["'self'", "'strict-dynamic'"],
    styleSrc: ["'self'", "'unsafe-inline'"],
    imgSrc: ["'self'", 'data:', 'https:'],
    connectSrc: ["'self'"],
    fontSrc: ["'self'"],
    objectSrc: ["'none'"],
    frameAncestors: ["'none'"],
  },
}));

A03: Injection

SQL Injection Prevention

// ❌ BAD: String concatenation
const query = `SELECT * FROM users WHERE email = '${email}'`;

// ✅ GOOD: Parameterized queries
// With Prisma
const user = await prisma.user.findUnique({ where: { email } });

// With raw SQL (parameterized)
const user = await db.query('SELECT * FROM users WHERE email = $1', [email]);

// With Knex
const user = await knex('users').where({ email }).first();

NoSQL Injection Prevention

// ❌ BAD: Direct user input in query
const user = await User.findOne({ username: req.body.username });
// Attack: { "username": { "$gt": "" } } returns first user

// ✅ GOOD: Validate input type
import { z } from 'zod';

const loginSchema = z.object({
  username: z.string().min(3).max(50),
  password: z.string().min(8),
});

app.post('/login', async (req, res) => {
  const { username, password } = loginSchema.parse(req.body);
  const user = await User.findOne({ username: String(username) });
  // ...
});

Command Injection Prevention

import { execFile } from 'child_process';

// ❌ BAD: Shell injection
exec(`convert ${userInput} output.png`);  // userInput: "; rm -rf /"

// ✅ GOOD: Use execFile with array args
execFile('convert', [userInput, 'output.png'], (error, stdout) => {
  // Safe - arguments are not shell-interpreted
});

// ✅ GOOD: Validate and sanitize
const allowedFormats = ['png', 'jpg', 'gif'];
if (!allowedFormats.inclu