**Course Title:** Mastering NestJS: Building Scalable Server-Side Applications **Section Title:** Security Best Practices in NestJS **Topic:** Implementing authentication and authorization (JWT and Passport) **Overview** In this topic, we will explore the implementation of authentication and authorization in NestJS applications using JSON Web Tokens (JWT) and Passport.js. We will cover the basics of authentication and authorization, the benefits of using JWT and Passport, and provide practical examples of implementing authentication and authorization in a NestJS application. **What is Authentication and Authorization?** Authentication is the process of verifying the identity of a user, while authorization is the process of determining what actions a user can perform on a system. In the context of a web application, authentication typically involves verifying a user's credentials (e.g., username and password) and authorization involves checking the user's permissions to access certain resources. **Benefits of Using JWT and Passport** JSON Web Tokens (JWT) are a popular choice for authentication in web applications because they provide a secure and efficient way to verify user identities. Passport.js is a popular authentication middleware for Node.js that provides a simple and flexible way to implement authentication and authorization in web applications. **Implementing Authentication with JWT and Passport** To implement authentication with JWT and Passport in a NestJS application, we need to follow these steps: 1. **Install Passport and JWT**: Install the `passport` and `jsonwebtoken` packages using npm or yarn. 2. **Configure Passport**: Configure Passport to use a strategy (e.g., local, JWT) to authenticate users. 3. **Create a Login Controller**: Create a login controller to handle user login requests. 4. **Generate a JWT Token**: Generate a JWT token for the authenticated user. 5. **Store the JWT Token**: Store the JWT token in a secure location (e.g., cookie, local storage). **Example Code** Here is an example of implementing authentication with JWT and Passport in a NestJS application: ```typescript // Import required modules import { Controller, Post, Body, Req, Res } from '@nestjs/common'; import { AuthService } from './auth.service'; import { User } from './user.entity'; import * as passport from 'passport'; import * as jwt from 'jsonwebtoken'; // Create a login controller @Controller('login') export class LoginController { constructor(private readonly authService: AuthService) {} // Handle user login requests @Post() async login(@Body() user: User, @Req() req: Request, @Res() res: Response) { // Authenticate the user using Passport passport.authenticate('local', (err, user) => { if (err) { return res.status(401).send({ message: 'Invalid credentials' }); } // Generate a JWT token for the authenticated user const token = jwt.sign({ userId: user.id }, process.env.SECRET_KEY, { expiresIn: '1h', }); // Store the JWT token in a secure location req.session.token = token; // Return the JWT token to the client return res.send({ token }); })(req, res); } } ``` **Implementing Authorization with JWT and Passport** To implement authorization with JWT and Passport in a NestJS application, we need to follow these steps: 1. **Verify the JWT Token**: Verify the JWT token sent by the client. 2. **Check User Permissions**: Check the user's permissions to access certain resources. **Example** Here is an example of implementing authorization with JWT and Passport in a NestJS application: ```typescript // Import required modules import { Controller, Get, UseGuards } from '@nestjs/common'; import { AuthGuard } from './auth.guard'; // Create a protected controller @Controller('protected') export class ProtectedController { // Use the AuthGuard to verify the JWT token @Get() @UseGuards(AuthGuard) async getProtectedResource() { // Return a protected resource to the client return { message: 'Hello, World!' }; } } ``` **Conclusion** In this topic, we have covered the implementation of authentication and authorization in NestJS applications using JSON Web Tokens (JWT) and Passport.js. We have provided practical examples of implementing authentication and authorization in a NestJS application and highlighted the benefits of using JWT and Passport. **Additional Resources** * [JSON Web Tokens (JWT) documentation](https://jwt.io/) * [Passport.js documentation](https://www.passportjs.org/docs/) * [NestJS documentation](https://docs.nestjs.com/) **Leave a comment or ask for help if you have any questions or need further clarification on any of the concepts covered in this topic.**