Custom Auth: PostgreSQL & JWT Implementation Guide

Introduction

In this comprehensive guide, we'll walk through the process of implementing a custom, self-hosted user authentication system. This system will leverage PostgreSQL for robust data storage and JSON Web Tokens (JWT) for secure session management. We are transitioning from Clerk to have more control and customization over our authentication process. This article aims to provide a detailed specification for the backend implementation of our user and authentication system.

Our goal is to create a secure, efficient, and scalable authentication system that meets our specific needs. By using PostgreSQL, we ensure reliable data storage, while JWTs enable stateless authentication, reducing server load and improving performance. This setup will give us greater flexibility and control over user management and security.

This guide will cover everything from setting up the database to implementing the API endpoints necessary for user registration, login, verification, logout, and accessing protected resources. We'll also delve into the specifics of using Bcrypt for password hashing, ensuring that our user data remains secure. By the end of this article, you'll have a solid understanding of how to build a custom authentication system using these technologies.

Core Requirements

To ensure our authentication system is robust and secure, we have several core requirements that must be met. These requirements cover the database technology, password hashing algorithm, and session management strategy. Let's dive into each of these to understand their importance and how they contribute to the overall security and functionality of our system.

1. Database: We will use PostgreSQL as our database. It is crucial that all passwords are stored securely, which means they must be hashed before being stored in the database. PostgreSQL offers excellent reliability and features that make it a great choice for handling sensitive user data. Using PostgreSQL ensures that we can leverage its robust features for data integrity and security.

2. Hashing: We will implement Bcrypt for password hashing and comparison. Bcrypt is a widely respected and secure hashing algorithm that adds a layer of protection to our user credentials. Bcrypt's adaptive hashing algorithm makes it resistant to brute-force attacks, which is essential for protecting user passwords. This ensures that even if our database is compromised, the passwords remain secure.

3. Session: We will employ JWTs for stateless authentication. JWTs allow us to authenticate users without needing to store session data on the server. Each JWT will contain the necessary user information, such as the user ID, and will be signed to ensure its integrity. This stateless approach reduces server load and improves scalability. JWTs provide a secure and efficient way to manage user sessions.

Backend API Endpoints Specification

To facilitate user authentication and authorization, we need to define a set of API endpoints. These endpoints will handle user registration, login, token verification, logout, and access to protected resources. Each endpoint has specific requirements to ensure security and functionality. Let's explore each endpoint in detail.

1. /api/auth/signup - User Registration

• Method: POST
• Purpose: This endpoint is responsible for registering new users in our system. It handles the process of receiving user credentials, securely storing them, and providing feedback to the user.
• Requirements:
  1. Receive email and password from the request body.
  2. Hash the password using Bcrypt to ensure it is stored securely.
  3. Store the email and the hashed password in the PostgreSQL database.
  4. Return a success message or a new JWT/session token to the client, indicating successful registration.

The signup endpoint is the first step for new users to access our system. It's crucial that this endpoint is implemented with security in mind. Bcrypt hashing ensures that even if the database is compromised, user passwords remain protected. Providing a JWT upon successful registration allows the user to immediately access protected resources.

2. /api/auth/signin - User Login

• Method: POST
• Purpose: This endpoint handles user login, verifying the provided credentials against those stored in the database.
• Requirements:
  1. Receive email and password from the request body.
  2. Find the user in the PostgreSQL database by their email.
  3. Compare the received password with the stored hash using Bcrypt to ensure they match.
  4. If the credentials match, generate a JWT containing the user ID and send it back to the frontend.

The signin endpoint is the gateway for existing users to access the system. Bcrypt is used again to compare the provided password with the stored hash, ensuring that only authorized users can gain access. Generating a JWT upon successful login allows the frontend to authenticate subsequent requests.

3. /api/auth/verify - Token/Session Validation

• Method: GET
• Purpose: This endpoint validates the JWT sent by the client, ensuring that the token is valid and has not expired.
• Requirements:
  1. Receive the JWT from the frontend's Authorization header.
  2. Verify the token's signature and expiration to ensure its integrity.
  3. If the token is valid, return a success status and basic user information (ID, email).

The verify endpoint is crucial for protecting resources. It allows the backend to confirm that the user is authenticated before granting access to protected routes. By verifying the JWT's signature and expiration, we can be confident that the token is legitimate and has not been tampered with.

4. /api/auth/signout - User Logout

• Method: POST
• Purpose: This endpoint handles user logout.
• Requirements:
  • (JWT Strategy): The server does nothing; the frontend deletes the token.

Since we are using a JWT strategy, the server-side implementation of the signout endpoint is minimal. The frontend is responsible for deleting the token, effectively logging the user out. This approach simplifies the backend and reduces the need for server-side session management.

5. /api/user/me - Protected Resource Example

• Method: GET
• Purpose: This endpoint provides an example of a protected resource that requires a valid JWT for access. It verifies that the authentication system is working correctly.
• Requirements:
  • Require a valid JWT in the Authorization header.
  • If the JWT is valid, return the authenticated user's profile data. This verifies that authentication is working correctly.

The /api/user/me endpoint serves as a test case for our authentication system. By requiring a valid JWT, we can ensure that only authenticated users can access this resource. Returning the user's profile data confirms that the token is correctly associated with a user in the database.

Definition of Done (DoD)

To ensure that our backend implementation is complete and meets the required standards, we have established a Definition of Done (DoD). This checklist outlines the criteria that must be met before considering the implementation finished. Let's review the key points:

• All five endpoints listed above (/api/auth/signup, /api/auth/signin, /api/auth/verify, /api/auth/signout, and /api/user/me) must be fully implemented and thoroughly unit/integration tested to ensure they function as expected.
• Password hashing must utilize Bcrypt to provide a high level of security for user credentials. This is a critical requirement for protecting user data.
• The /api/auth/signin endpoint must successfully generate and return a signed JWT upon successful authentication. This JWT will be used for subsequent requests to protected resources.
• The /api/auth/verify and /api/user/me endpoints must successfully validate an incoming JWT, ensuring that only authenticated users can access protected resources. This validation process is essential for maintaining the security of our system.

Meeting these criteria ensures that our backend implementation is robust, secure, and fully functional. Thorough testing and adherence to the defined requirements are crucial for delivering a high-quality authentication system.

Conclusion

Implementing a custom user authentication system with PostgreSQL and JWT offers greater control, flexibility, and security compared to relying on third-party services. By following this detailed specification, you can build a robust authentication system tailored to your specific needs.

From setting up the database to implementing the API endpoints, each step is crucial in ensuring a secure and efficient authentication process. Using Bcrypt for password hashing and JWTs for session management enhances the overall security and scalability of the system. Thorough testing and adherence to the Definition of Done are essential for a successful implementation.

This guide provides a solid foundation for building a custom authentication system. With careful planning and execution, you can create a secure and reliable authentication solution that meets your requirements.

For more information on JWT, you can check the official jwt.io website.