Authentication & Authorization: A Complete Guide

Published 6 hours ago

Introduction

Authentication and authorization are fundamental aspects of application security. Authentication verifies the identity of a user, while authorization determines the actions a user is allowed to perform.

This guide will cover:

Handling user authentication
JWT (JSON Web Tokens) authentication
OAuth and third-party login (Google, Facebook)
Role-based access control (RBAC)

1. Handling User Authentication

Authentication ensures that users are who they claim to be. Common authentication methods include:

a) Password-Based Authentication

Users provide a username/email and password.
Best practices:
Store passwords securely using bcrypt or Argon2.
Enforce strong password policies.
Implement rate limiting to prevent brute-force attacks.

b) Multi-Factor Authentication (MFA)

Adds an extra layer of security using:
SMS/Email verification
Authenticator apps (Google Authenticator, Authy)
Biometric authentication (fingerprint, facial recognition)

c) Session-Based Authentication

The server stores a session ID in cookies after successful login.
Drawbacks:
Not suitable for stateless applications.
Requires session storage (database, Redis, etc.).

2. JWT (JSON Web Tokens) Authentication

JWT is a compact, self-contained token used for securely transmitting information.

a) Structure of a JWT

A JWT consists of three parts:

Header: Specifies the algorithm (e.g., HS256).
Payload: Contains user data (e.g., user ID, role).
Signature: Ensures token integrity.

Example JWT:

{
  "header": { "alg": "HS256", "typ": "JWT" },
  "payload": { "user_id": 123, "role": "admin" },
  "signature": "abc123xyz"
}

b) How JWT Authentication Works

User logs in with credentials.
Server verifies credentials and generates a JWT.
Client stores the JWT (local storage or cookies).
JWT is sent in every request (Authorization: Bearer <token>).
Server validates the JWT and grants access.

c) Best Practices

Use short-lived tokens (e.g., 15 minutes) and refresh tokens.
Store tokens securely (use HTTPOnly cookies instead of local storage).
Implement token revocation for security.

3. OAuth and Third-Party Login (Google, Facebook)

OAuth 2.0 is a protocol that allows third-party authentication without exposing user credentials.

a) OAuth Flow

User clicks "Login with Google/Facebook".
Redirected to provider's authorization server.
User grants permission.
Provider returns an authorization code.
App exchanges the code for an access token.
App uses token to authenticate API requests.

b) Implementing OAuth (Google Example)

Register your app on Google Developer Console.
Get Client ID and Client Secret.
Use Google's OAuth endpoints for authentication.

Example OAuth URL:

https://accounts.google.com/o/oauth2/auth?client_id=YOUR_CLIENT_ID&redirect_uri=YOUR_REDIRECT_URI&response_type=code&scope=email%20profile

Exchange the authorization code for an access token.
Fetch user data using the access token.

4. Role-Based Access Control (RBAC)

RBAC restricts access based on user roles (e.g., Admin, User, Moderator).

a) Defining Roles & Permissions

b) Implementing RBAC in Code (Node.js Example)

const roles = {
  admin: ['create', 'read', 'update', 'delete'],
  editor: ['read', 'update'],
  user: ['read']
};

function checkPermission(role, action) {
  return roles[role]?.includes(action);
}

console.log(checkPermission('admin', 'delete')); // true
console.log(checkPermission('user', 'delete')); // false

c) Middleware for Role-Based Access (Express.js)

function authorizeRole(role) {
  return (req, res, next) => {
    if (req.user.role !== role) {
      return res.status(403).json({ message: 'Access Denied' });
    }
    next();
  };
}

app.get('/admin', authorizeRole('admin'), (req, res) => {
  res.send('Welcome Admin');
});

Conclusion

Authentication and authorization are essential for securing applications. This guide covered:

User authentication (passwords, MFA, sessions)
JWT authentication for stateless authentication
OAuth & third-party login for seamless authentication
Role-Based Access Control (RBAC) for managing permissions

Implement these best practices to build secure applications and protect user data.

Obafemi Emmanuel