Implement CSRF Protection with Node.js Express

const express = require('express');
const cookieParser = require('cookie-parser');
const session = require('express-session');
const csurf = require('csurf');
const bodyParser = require('body-parser');

const app = express();

app.use(cookieParser());
app.use(session({
  secret: 'super-secret-key-for-session', // Use a strong, unique secret
  resave: false,
  saveUninitialized: true,
  cookie: { secure: process.env.NODE_ENV === 'production', httpOnly: true, sameSite: 'Lax' }
}));
app.use(bodyParser.urlencoded({ extended: false }));

// CSRF protection middleware
const csrfProtection = csurf({ cookie: true });

// Route to render a form with a CSRF token
app.get('/form', csrfProtection, (req, res) => {
  res.send(`
    <form action="/process" method="POST">
      <input type="hidden" name="_csrf" value="${req.csrfToken()}">
      <input type="text" name="message" placeholder="Your message">
      <button type="submit">Submit</button>
    </form>
  `);
});

// Route to process the form submission
app.post('/process', csrfProtection, (req, res) => {
  // Access req.body here after CSRF check
  res.send(`Message received: ${req.body.message}`);
});

// Error handling for CSRF issues
app.use((err, req, res, next) => {
  if (err.code !== 'EBADCSRFTOKEN') return next(err);
  res.status(403).send('CSRF token invalid or missing');
});

const PORT = 3000;
app.listen(PORT, () => console.log(`Server running on http://localhost:${PORT}`));