1. Introduction

Goal of this Tutorial

This tutorial will guide you through the process of implementing authentication and authorization in an API. These are key security features that help control who can access your application and what they can do.

Learning Outcomes

By the end of this tutorial, you will be able to:
- Understand the difference between authentication and authorization
- Implement basic authentication in your API
- Implement role-based access control for authorization
- Protect your API endpoints using authentication and authorization techniques

Prerequisites

You should be familiar with:
- Basic concepts of Web Development
- JavaScript (ES6+)
- Node.js and Express.js
- Basic knowledge of HTTP requests and responses

2. Step-by-Step Guide

Understanding Authentication and Authorization

Authentication is the process of verifying the identity of a user, device, or system. It often involves usernames and passwords, but can also include any other method of demonstrating identity, such as multi-factor authentication.

Authorization, on the other hand, is the process of granting or denying access to specific resources or actions. Once a user/device/system is authenticated, they are then authorized to perform certain actions.

Implementing Basic Authentication

In this tutorial, we will use the Passport.js library to implement basic authentication in a Node.js and Express.js application.

First, install Passport.js and the passport-local strategy:

npm install passport passport-local

Then, configure Passport.js in your main server file:

const express = require('express');
const passport = require('passport');
const LocalStrategy = require('passport-local').Strategy;

const app = express();

// Configure Passport.js
passport.use(new LocalStrategy(
  function(username, password, done) {
    // Insert your logic to authenticate a user here.
  }
));

app.use(passport.initialize());

// Your routes go here

app.listen(3000, () => console.log('Server started on port 3000'));

3. Code Examples

Implementing Authorization

Let's continue with the code from the authentication example and add role-based authorization. We will use the connect-roles library for this:

First, install the package:

npm install connect-roles

Then, implement role-based authorization:

const express = require('express');
const passport = require('passport');
const LocalStrategy = require('passport-local').Strategy;
const ConnectRoles = require('connect-roles');

const app = express();
const user = new ConnectRoles();

// Configure Passport.js
passport.use(new LocalStrategy(
  function(username, password, done) {
    // Insert your logic to authenticate a user here.
  }
));

// Configure connect-roles
user.use('access admin content', function (req) {
  if (req.user.role === 'admin') {
    return true;
  }
});

app.use(passport.initialize());
app.use(user.middleware());

// Protect your routes
app.get('/admin', user.can('access admin content'), (req, res) => {
  res.send('This is the admin area, only admins can see this!');
});

app.listen(3000, () => console.log('Server started on port 3000'));

4. Summary

In this tutorial, you've learned how to implement authentication and authorization in a Node.js and Express.js application. You've also learned the difference between these two concepts and why they're important for securing your applications.

5. Practice Exercises

Exercise 1

Implement a registration route that adds new users to an array of users. Each user should have a username, password and role.

Exercise 2

Implement a login route that authenticates a user based on the username and password. Upon successful authentication, the user's role should be stored in the session for authorization in subsequent requests.

Exercise 3

Implement a route that only authenticated admins can access. Use the role stored in the session to verify whether the user is an admin.

Further Practice

Try implementing other types of authentication like JWT authentication and OAuth. Try implementing other types of authorization like Attribute-Based Access Control (ABAC) and Mandatory Access Control (MAC).