**Course Title:** Mastering Express.js: Building Scalable Web Applications and APIs **Section Title:** Authentication and Authorization **Topic:** Role-based access control and securing routes **Introduction** In the previous topic, we implemented user authentication using Passport.js and created user sessions. However, authentication is only half the battle. Once users are authenticated, we need to ensure that they only have access to resources and actions that they are authorized to perform. This is where role-based access control (RBAC) comes in. **What is Role-Based Access Control?** Role-based access control (RBAC) is a security approach that restricts system access to authorized users based on their roles within an organization. In a RBAC system, roles are defined based on the specific responsibilities of users, and access to resources is determined by the roles to which users are assigned. **Securing Routes with RBAC** In Express.js, we can implement RBAC by defining middleware functions that check the role of the authenticated user before granting access to specific routes. Here's an example of how we can implement RBAC middleware: ```javascript // roles.js const roles = { admin: ['create-post', 'edit-post', 'delete-post'], moderator: ['edit-post'], user: ['create-post'] }; module.exports = roles; ``` ```javascript // auth.js const express = require('express'); const router = express.Router(); const roles = require('./roles'); const authenticateRole = (requiredRole) => { return (req, res, next) => { const userRole = req.user.role; if (!userRole || !roles[userRole].includes(requiredRole)) { return res.status(403).send('Access denied'); } next(); }; }; module.exports = authenticateRole; ``` ```javascript // routes.js const express = require('express'); const router = express.Router(); const authenticateRole = require('./auth'); router.post('/create-post', authenticateRole('create-post'), (req, res) => { // Create post logic }); router.put('/edit-post', authenticateRole('edit-post'), (req, res) => { // Edit post logic }); router.delete('/delete-post', authenticateRole('delete-post'), (req, res) => { // Delete post logic }); ``` In this example, we define a set of roles and their corresponding permissions in the `roles.js` file. We then create an RBAC middleware function, `authenticateRole`, which checks if the authenticated user has the required role to access a specific route. We then apply this middleware function to each route that requires authorization. **Practical Takeaways** 1. Implementing RBAC helps to ensure that users only have access to resources and actions that they are authorized to perform. 2. Use middleware functions to check the role of the authenticated user before granting access to specific routes. 3. Define a set of roles and their corresponding permissions to ensure clarity and consistency in your authorization system. **Additional Resources** * [OWASP's Role-Based Access Control Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Role_Based_Access_Control_Cheat_Sheet.html) * [Wikipedia's article on Role-Based Access Control](https://en.wikipedia.org/wiki/Role-based_access_control) **Exercise** Implement RBAC in your existing Express.js application. Define a set of roles and their corresponding permissions, and apply RBAC middleware functions to each route that requires authorization. **Leave a comment/ask for help** If you have any questions or need further clarification on implementing RBAC in Express.js, please leave a comment below. **What's next?** In the next topic, we'll cover the principles of RESTful API design and learn how to build scalable and maintainable APIs.