JWT-based email authentication middleware for Express.js

emailVerificationService.ts

import SimpleEmailService from '../amazon/SimpleEmailService';
import { Express, Request, Response, NextFunction } from 'express';
import { sign, verify } from 'jsonwebtoken';

const simpleEmailService = new SimpleEmailService();

/**
 * Middleware function to verify a JWT token.
 */
export async function verifyToken(
  req: Request,
  res: Response,
  next: NextFunction
) {
  const { token } = req.body;
  const decodedToken = decodeURIComponent(token);

  try {
    const jwtSecret = process.env.JWT_SECRET || 'secret';
    const decoded = verify(decodedToken, jwtSecret) as {
      email: string;
    };
    // Set the email in the request body so it can be used by the next middleware function.
    req.body.email = decoded.email;
    next(); // Continue to the next middleware function.
  } catch (error) {
    console.log(error);
    return res.status(401).json({
      status: 401, // Unauthorized
      message: 'Invalid or expired token',
    });
  }
}

/**
 * Middleware function to create a JWT token and send an email with a link to verify the email address.
 */
export function createTokenAndSendEmail(htmlTemplate: string) {
  return async (req: Request, res: Response, next: NextFunction) => {
    const { email } = req.body;
    const jwtSecret = process.env.JWT_SECRET || 'secret';
    const expiresIn = process.env.JWT_EXPIRES_IN || '24h';
    const token = sign({ email }, jwtSecret, { expiresIn });
    const encodedToken = encodeURIComponent(token);
    const mailOptions = {
      from: '[email protected]',
      to: email,
      subject: 'SSIT Dev Status: Verify your email address',
      html: htmlTemplate.replace('${token}', encodedToken),
    };

    await simpleEmailService.send(mailOptions);
    next();
  };
}

// Example Middleware Usage.

function requestAuthJwtController(req: Request, res: Response) {
  return res.json({
    status: 200,
    message: 'success',
  });
}

function verifyEmailController(req: Request, res: Response) {
  // The email was set in the request body by the verifyToken middleware.
  const { email } = req.body;
  return res.json({
    status: 200,
    message: 'success',
    data: { email },
  });
}

export function tokenAuthRoutes(app: Express) {
  const tokenAuthUrl = process.env.TOKEN_AUTH_URL || 'https://localhost:4200/home';
  const htmlTemplate = `
<p>Click the link below to verify your email address.</p>
<a href="${tokenAuthUrl}?token=\${token}">Verify Email</a>
`;
  
  /**
   * Step 1. The client requests a JWT token and an email is sent to the user.
   * @todo this should have an async error handler.
   */
  app
    .route('/api/auth/request-jwt-auth')
    .post(createTokenAndSendEmail(htmlTemplate), requestAuthJwtController);

  /**
   * Step 2. The client clicks the link in the email and the email address is verified.
   * Note: The verifyToken middleware verifies the JWT token.
   *  If the token is valid, the email address is set in the request body and the
   * email address is returned in the response.
   * If the token is invalid, a 401 response is returned.
   */
  app.route('/api/auth/verify-email').post(verifyToken, verifyEmailController);
}