Secure Your API with Authentication

Add user registration, JWT login, and per-user data isolation to your FastAPI expense tracker.

Intermediate

3 hours

4 lessons

Course Content

27 chapters across 4 lessons

Build Your Auth Module

Create auth.py with a User model, password hashing, and JWT token creation and verification.

9 chapters

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Why Authentication Matters

Continue

Understand why your API needs authentication and what you will build

Install Auth Packages

Install passlib and python-jose for password hashing and JWT tokens

The User Model

Create auth.py with a User model that stores email and hashed password

Hash Passwords Safely

Add password hashing and verification functions using bcrypt

Create a JWT Token

Add a function that generates signed JSON Web Tokens for authenticated users

How Token Verification Works

Understand how your app will extract, decode, and validate tokens from incoming requests

Set Up Token Extraction

Add the OAuth2 scheme that reads JWT tokens from the Authorization header

Build the Token Verifier

Write get_current_user — the function that decodes tokens and finds users

Lesson Complete

You finished Build Your Auth Module

Registration and Login

Add registration and login endpoints to your API using the auth module.

6 chapters

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How Token Authentication Works

Understand the full authentication flow from registration to protected requests

The Registration Endpoint

Add a POST /register endpoint that creates user accounts

Try Registering a User

Test the registration endpoint with a curl command

The Login Endpoint

Add a POST /login endpoint that verifies credentials and returns a JWT

Try Logging In

Test the login endpoint and receive a JWT token

Lesson Complete

You finished Registration and Login

Protect Your Endpoints

Lock down every expense endpoint with token authentication and per-user data isolation.

7 chapters

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One Small Change, Big Impact

Learn how FastAPI dependencies act as gatekeepers for your endpoints

Link Expenses to Users

Add a user_id field to the Expense model

Protect Create Expense

Add authentication to the create expense endpoint

Protect List and Get

Add authentication and user filtering to the list and get endpoints

Protect Update and Delete

Add authentication and ownership checks to the update and delete endpoints

Protect Summary

Add authentication to the spending summary endpoint

Lesson Complete

You finished Protect Your Endpoints

Update Your Tests

Update the test suite to work with authenticated endpoints and test data isolation.

5 chapters

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Why Your Tests Broke

Understand why every test returns 401 and how to fix them

Auth Test Helpers

Write register_user and auth_header helper functions for authenticated tests

Test Registration and Login

Write tests for the registration and login endpoints

Test Data Isolation

Write a test that proves two users each see only their own expenses

Lesson Complete

You finished Update Your Tests