Security Hardening Skill

Implement comprehensive security practices to protect web applications from common vulnerabilities.

OWASP Top 10 (2024)

Risk	Prevention
Injection	Parameterized queries, input validation
Broken Auth	MFA, secure sessions, rate limiting
Sensitive Data	Encryption at rest/transit, minimal exposure
XXE	Disable external entities, use JSON
Broken Access	RBAC, verify ownership
Misconfig	Security headers, disable debug
XSS	Output encoding, CSP
Insecure Deserialization	Validate input, use safe formats
Vulnerable Components	Audit deps, update regularly
Logging Gaps	Log security events, monitor

Security Headers

Next.js Configuration

// next.config.js
const securityHeaders = [
  {
    key: 'X-DNS-Prefetch-Control',
    value: 'on'
  },
  {
    key: 'Strict-Transport-Security',
    value: 'max-age=63072000; includeSubDomains; preload'
  },
  {
    key: 'X-Frame-Options',
    value: 'SAMEORIGIN'
  },
  {
    key: 'X-Content-Type-Options',
    value: 'nosniff'
  },
  {
    key: 'X-XSS-Protection',
    value: '1; mode=block'
  },
  {
    key: 'Referrer-Policy',
    value: 'strict-origin-when-cross-origin'
  },
  {
    key: 'Permissions-Policy',
    value: 'camera=(), microphone=(), geolocation=()'
  },
  {
    key: 'Content-Security-Policy',
    value: `
      default-src 'self';
      script-src 'self' 'unsafe-inline';
      style-src 'self' 'unsafe-inline';
      img-src 'self' blob: data: https:;
      font-src 'self';
      connect-src 'self' https://api.frankx.ai;
      frame-ancestors 'none';
    `.replace(/\n/g, '')
  }
];

module.exports = {
  async headers() {
    return [
      {
        source: '/:path*',
        headers: securityHeaders,
      },
    ];
  },
};

Input Validation

Zod Schema Validation

import { z } from 'zod';

const UserInputSchema = z.object({
  email: z.string().email().max(255),
  name: z.string().min(1).max(100).regex(/^[a-zA-Z\s]+$/),
  age: z.number().int().min(0).max(150),
  url: z.string().url().optional(),
});

// Sanitize HTML content
import DOMPurify from 'isomorphic-dompurify';

const sanitizedHtml = DOMPurify.sanitize(userInput, {
  ALLOWED_TAGS: ['b', 'i', 'em', 'strong', 'a'],
  ALLOWED_ATTR: ['href'],
});

SQL Injection Prevention

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

// BAD: String interpolation - NEVER do this
// const user = db.query(`SELECT * FROM users WHERE email = '${email}'`);

Authentication Best Practices

Password Hashing

import { hash, verify } from 'argon2';

// Hash password
const hashedPassword = await hash(password, {
  type: 2, // Argon2id
  memoryCost: 65536,
  timeCost: 3,
  parallelism: 4,
});

// Verify password
const isValid = await verify(hashedPassword, password);

Session Security

// lib/session.ts
import { cookies } from 'next/headers';
import { SignJWT, jwtVerify } from 'jose';

const secret = new TextEncoder().encode(process.env.SESSION_SECRET);

export async function createSession(userId: string) {
  const token = await new SignJWT({ userId })
    .setProtectedHeader({ alg: 'HS256' })
    .setIssuedAt()
    .setExpirationTime('7d')
    .sign(secret);

  (await cookies()).set('session', token, {
    httpOnly: true,
    secure: process.env.NODE_ENV === 'production',
    sameSite: 'lax',
    maxAge: 60 * 60 * 24 * 7, // 7 days
    path: '/',
  });
}

Rate Limiting

import { Ratelimit } from '@upstash/ratelimit';
import { Redis } from '@upstash/redis';

const ratelimit = new Ratelimit({
  redis: Redis.fromEnv(),
  limiter: Ratelimit.slidingWindow(5, '1 m'), // 5 attempts per minute
  analytics: true,
});

export async function loginRateLimit(ip: string) {
  const { success, remaining } = await ratelimit.limit(`login:${ip}`);
  if (!success) {
    throw new Error('Too many login attempts. Try again later.');
  }
  return remaining;
}

Authorization (RBAC)

// lib/permissions.ts
type Role = 'admin' | 'editor' | 'viewer';
type Permission = 'read' | 'write' | 'delete' | 'admin';

const rolePermissions: Record<Role, Permission[]> = {
  admin: ['read', 'write', 'delete', 'admin'],
  editor: ['read', 'write'],
  viewer: ['read'],
};

export function hasPermission(role: Role, permission: Permission): boolean {
  return rolePermissions[role]?.includes(permission) ?? false;
}

// Middleware usage
export async function requirePermission(permission: Permission) {
  const session = await getSession();
  if (!session || !hasPermission(session.role, permission)) {
    throw new Error('Forbidden');
  }
}

CSRF Protection

// For forms in Next.js, use Server Actions which have built-in CSRF protection
// For API routes, use the double-submit cookie pattern:

import { cookies } from 'next/headers';
import { nanoid } from 'nanoid';

export async function generateCsrfToken() {
  const token = nanoid(32);
  (await cookies()).set('csrf', token, {
    httpOnly: true,
    secure: true,
    sameSite: 'strict',
  });
  return token;
}

export async function verifyCsrfToken(submittedToken: string) {
  const storedToken = (await cookies()).get('csrf')?.value;
  if (!storedToken || storedToken !== submittedToken) {
    throw new Error('Invalid CSRF token');
  }
}

Secrets Management

// NEVER commit secrets to git
// Use environment variables

// .env.local (gitignored)
DATABASE_URL=postgresql://...
JWT_SECRET=super-long-random-string
API_KEY=sk-...

// Access in code
const apiKey = process.env.API_KEY;

// Validate required secrets at startup
const requiredEnvVars = ['DATABASE_URL', 'JWT_SECRET'];
for (const envVar of requiredEnvVars) {
  if (!process.env[envVar]) {
    throw new Error(`Missing required environment variable: ${envVar}`);
  }
}

Security Checklist

• HTTPS only (HSTS enabled)
• Secure headers configured
• Input validation on all user input
• Parameterized database queries
• Passwords hashed with Argon2id
• Sessions: httpOnly, secure, sameSite
• Rate limiting on auth endpoints
• RBAC implemented
• CSRF protection enabled
• Dependencies audited (

  npm audit

  )
• Secrets in environment variables
• Error messages don't leak info
• Logging security events

Anti-Patterns

Avoid these dangerous practices:

• Storing passwords in plain text
• Trusting client-side validation only
• Exposing stack traces to users
• Using MD5/SHA1 for passwords
• Hardcoding secrets in code
• Executing arbitrary user input as code

Best practices:

• Hash with Argon2id/bcrypt
• Server-side validation always
• Generic error messages
• Modern hashing algorithms
• Environment variables for secrets
• Never execute untrusted input