Hello World Full-Stack Security: React/JavaScript + Flask/Python

Published on February 8, 2022

Developers can easily secure a full-stack application using Auth0 by Okta. This code sample demonstrates how to implement authentication in a client application built with React and JavaScript, as well as how to implement authorization in an API server built with Flask and Python. You'll connect the client and server applications to see the full security flow in action!

Let's get started!

Quick Auth0 Set Up

To get started, create an Auth0 account to connect your application with the Auth0 Identity Platform. You can also use any of your existing Auth0 accounts.

Get the Auth0 domain and client ID

• Open the Applications section of the Auth0 Dashboard.

• Click on the Create Application button and fill out the form with the following values:

  • Name: Hello World Client

  • Application Type: Single Page Web Applications

• Click on the Create button.

An Auth0 Application page loads up.

As such, click on the "Settings" tab of your Auth0 Application page, locate the "Application URIs " section, and fill in the following values:

• Allowed Callback URLs: http://localhost:4040/callback

• Allowed Logout URLs: http://localhost:4040

• Allowed Web Origins: http://localhost:4040

Scroll down and click the "Save Changes" button.

Next, locate the "Basic Information" section.

When you enter a value in the input fields present on this page, any code snippet that uses such value updates to reflect it. Using the input fields makes it easy to copy and paste code as you follow along.

As such, enter the "Domain" and "Client ID" values in the following fields to set up your single-page application in the next section:

Get the Auth0 audience

• Open the APIs section of the Auth0 Dashboard.

• Click on the Create API button and fill out the "New API" form with the following values:

  • Name: Hello World Server

  • Identifier: https://hello-world.example.com

• Click on the Create button.

When setting up APIs, we also refer to the API identifier as the Audience value. Store that value in the following field to set up your API server in the next section:

Set Up and Run the Flask Project

Start by cloning the Flask project:

git clone https://github.com/auth0-developer-hub/api_flask_python_hello-world.git

Make the project directory your current working directory:

cd api_flask_python_hello-world

Then, check out the basic-role-based-access-control branch, which holds all the code related to implementing token-based authorization to protect resources in a Flask API:

git checkout basic-role-based-access-control

Create a virtual environment under the root project directory:

macOS/Linux:

python3 -m venv venv

Windows:

py -3 -m venv venv

Activate the virtual environment:

macOS/Linux:

. venv/bin/activate

Windows:

venv\Scripts\activate

Install the Flask project dependencies:

pip install -r requirements.txt

Now, create a .env file under the project directory and populate it as follows:

CLIENT_ORIGIN_URL=http://localhost:4040
AUTH0_AUDIENCE=AUTH0-AUDIENCE
AUTH0_DOMAIN=AUTH0-DOMAIN

Execute the following command to run the Flask API server:

flask run

Set Up and Run the React Project

Start by cloning the project into your local machine:

git clone https://github.com/auth0-developer-hub/spa_react_javascript_hello-world.git

Make the project directory your current working directory:

cd spa_react_javascript_hello-world

Then, check out the basic-authentication-with-api-integration branch, which holds all the React code related to implementing user login with Auth0 and requesting protected resources from an API:

git checkout basic-authentication-with-api-integration

Next, install the React project dependencies:

npm install

Once you have access to the React project, create a .env file under the project directory and populate it as follows:

REACT_APP_AUTH0_DOMAIN=AUTH0-DOMAIN
REACT_APP_AUTH0_CLIENT_ID=AUTH0-CLIENT-ID
REACT_APP_AUTH0_CALLBACK_URL=http://localhost:4040/callback
REACT_APP_API_SERVER_URL=http://localhost:6060
REACT_APP_AUTH0_AUDIENCE=AUTH0-AUDIENCE

Run the React application by issuing the following command:

npm start

You can now visit http://localhost:4040/ to access the application.

There's something missing in this React code sample. There's no login or sign-up forms!

When you use Auth0, you don't need to build any login or sign-up forms! Your users can log in to your application through a page hosted by Auth0, which provides a secure, standards-based login experience. You can customize the Auth0 login page with your branding and enable different authentication methods, such as logging in with a username/password combination or a social provider like Facebook or Google.

Once you log in, visit the protected "Profile" page (http://localhost:4040/profile) to see all the user profile information that Auth0 securely shares with your application using ID tokens.

Then, visit the "Protected" page (http://localhost:4040/protected) or the "Admin" page (http://localhost:4040/admin) to practice requesting protected resources from an external API server using access tokens.

Set Up Role-Based Access Control (RBAC)

The access token present in the authorization header of a request must include a permissions claim that contains the read:admin-messages permission to access the GET /api/messages/admin endpoint.

You can use the Auth0 Dashboard to enable Role-Based Access Control (RBAC) and then implement it by creating API permissions, assigning those permissions to a role, and assigning that role to a user.

Enable Role-Based Access Control (RBAC)

• Open the APIs section of the Auth0 Dashboard and select your "Hello World Server" registration.

• Click on the "Settings" tab and locate the "RBAC Settings" section.

• Switch on the "Enable RBAC" and "Add Permissions in the Access Token" options.

Create an API permission

In the same Auth0 API registration page, follow these steps:

• Click on the "Permissions" tab and fill a field from the "Add a Permission (Scope)" section with the following information:

  • Permission (Scope): read:admin-messages
  • Description: Read admin messages

• Click the "+ Add" button to store the permission.

Create a role with permissions

Create a role

• Open the Roles section of the Auth0 Dashboard.

• Click on the Create role button and fill out the "New Role" form with the following values:

  • Name: messages-admin

  • Description: Read admin messages.

• Click on the Create button.

Add permissions to the role

• Click on the "Permissions" tab of the roles page.

• Click on the "Add Permissions" button.

• Select the "Hello World Server" from the dropdown menu that comes up and click the "Add Permissions" button.

• Select all the permissions available by clicking on them one by one or by using the "All" link.

• Finally, click on the "Add Permissions" button to finish up.

Create an admin user

• Open the Users section from the Auth0 Dashboard.

• Click on the "Create user" button and fill out the form with the required information. Alternatively, you can also click on any of your existing users to give one of them the admin role.

• On the user's page, click on the "Roles" tab and then click on the "Assign Roles" button.

• Select the messages-admin role from the dropdown menu and click on the "Assign" button.

Access the admin endpoint

Head to the client application, log in and visit the guarded http://localhost:4040/admin page.

When you log in to a "Hello World" client application as a user who has the messages-admin role, your access token will have the required permissions to access the GET /api/messages/admin endpoint, and you'll get the following response:

{
  "text": "This is an admin message."
}

However, when you log in as a user who doesn't have the messages-admin role, you'll get a 403 Forbidden status code and the following response:

{
  "message": "Permission denied"
}