Integrate Your Python Flask Application With FusionAuth

In this article, you are going to learn how to integrate a Python Flask application with FusionAuth.

Here’s a typical application login flow before integrating FusionAuth into your Python Flask application.

Here’s the same application login flow when FusionAuth is introduced.

Prerequisites

For this tutorial, you’ll need to have python3 and pip3 installed.

You’ll also need Docker, since that is how you’ll install FusionAuth.

The commands below are for macOS, but are limited to mkdir and cd, which have equivalents in Windows and Linux.

Download and Install FusionAuth

First, make a project directory:

   
mkdir integrate-fusionauth && cd integrate-fusionauth

Then, install FusionAuth:

   
curl -o docker-compose.yml https://raw.githubusercontent.com/FusionAuth/fusionauth-containers/master/docker/fusionauth/docker-compose.yml
curl -o .env https://raw.githubusercontent.com/FusionAuth/fusionauth-containers/master/docker/fusionauth/.env
docker-compose up -d

Create a User and an API Key

Next, log into your FusionAuth instance. You’ll need to set up a user and a password, as well as accept the terms and conditions.

Then, you’re at the FusionAuth admin UI. This lets you configure FusionAuth manually. But for this tutorial, you’re going to create an API key and then you’ll configure FusionAuth using our client library.

Navigate to Settings -> API Keys. Click the + button to add a new API Key. Copy the value of the Key field and then save the key. It might be a value like CY1EUq2oAQrCgE7azl3A2xwG-OEwGPqLryDRBCoz-13IqyFYMn1_Udjt.

Doing so creates an API key that can be used for any FusionAuth API call. Save that key value off as you’ll be using it later.

Configure FusionAuth

Next, you need to set up FusionAuth. This can be done in different ways, but we’re going to use the Python client library. You can use the client library with an IDE of your preference as well.

First, create the required files:

   
touch requirements.txt setup.py

Now, cut and paste the following requirements into requirements.txt:

   
fusionauth-client==1.42.0

Then, copy and paste the following code into the setup.py file.

   
from fusionauth.fusionauth_client import FusionAuthClient
import os
import sys

APPLICATION_ID = "e9fdb985-9173-4e01-9d73-ac2d60d1dc8e";

#  You must supply your API key
api_key_name = 'fusionauth_api_key'
api_key = os.getenv(api_key_name)
if not api_key:
  sys.exit("please set api key in the '" + api_key_name + "' environment variable")

client = FusionAuthClient(api_key, 'http://localhost:9011')

# set the issuer up correctly
client_response = client.retrieve_tenants()
if client_response.was_successful():
  tenant = client_response.success_response["tenants"][0]
else:
  sys.exit("couldn't find tenants " + str(client_response.error_response))

client_response = client.patch_tenant(tenant["id"], {"tenant": {"issuer":"http://localhost:9011"}})
if not client_response.was_successful():
  sys.exit("couldn't update tenant "+ str(client_response.error_response))

# generate RSA keypair for signing
rsa_key_id = "356a6624-b33c-471a-b707-48bbfcfbc593"

client_response = client.generate_key({"key": {"algorithm":"RS256", "name":"For PythonExampleApp", "length": 2048}}, rsa_key_id)
if not client_response.was_successful():
  sys.exit("couldn't create RSA key "+ str(client_response.error_response))

# create application
# too much to inline it

application = {}
application["name"] = "PythonExampleApp"

# configure oauth
application["oauthConfiguration"] = {}
application["oauthConfiguration"]["authorizedRedirectURLs"] = ["http://localhost:5001/callback"]
application["oauthConfiguration"]["requireRegistration"] = True
application["oauthConfiguration"]["enabledGrants"] = ["authorization_code", "refresh_token"]
application["oauthConfiguration"]["logoutURL"] = "http://localhost:5001/logout"
application["oauthConfiguration"]["clientSecret"] = "change-this-in-production-to-be-a-real-secret"

# assign key from above to sign tokens. This needs to be asymmetric
application["jwtConfiguration"] = {}
application["jwtConfiguration"]["enabled"] = True
application["jwtConfiguration"]["accessTokenKeyId"] = rsa_key_id
application["jwtConfiguration"]["idTokenKeyId"] = rsa_key_id

client_response = client.create_application({"application": application}, APPLICATION_ID)
if not client_response.was_successful():
  sys.exit("couldn't create application "+ str(client_response.error_response))

# register user, there should be only one, so grab the first
client_response = client.search_users_by_query({"search": {"queryString":"*"}})
if not client_response.was_successful():
  sys.exit("couldn't find users "+ str(client_response.error_response))

user = client_response.success_response["users"][0]

# patch the user to make sure they have a full name, otherwise OIDC has issues
client_response = client.patch_user(user["id"], {"user": {"fullName": user["firstName"]+" "+user["lastName"]}})
if not client_response.was_successful():
  sys.exit("couldn't patch user "+ str(client_response.error_response))

# now register the user
client_response = client.register({"registration":{"applicationId":APPLICATION_ID}}, user["id"])
if not client_response.was_successful():
  sys.exit("couldn't register user "+ str(client_response.error_response))

Then, you can run the setup script.

The setup script is designed to run on a newly installed FusionAuth instance with only one user and no tenants other than Default. To follow this guide on a FusionAuth instance that does not meet these criteria, you may need to modify the above script.

Refer to the Python client library documentation for more information.

You’ll use a virtual environment venv to keep your workspace clean.

   
python -m venv venv && \
source venv/bin/activate && \
pip install -r requirements.txt

Now run the setup script, replacing <your API key> with the value of the API key noted earlier.

   
fusionauth_api_key=YOUR_API_KEY_FROM_ABOVE python setup.py

If you are using PowerShell, you will need to set the environment variable in a separate command before executing the script.

   
$env:fusionauth_api_key='YOUR_API_KEY_FROM_ABOVE'
python setup.py

This configures FusionAuth for your Python Flask application.

When you’re done, you can log in to your instance and examine the new application configuration that the script created for you.

Create Your Python Flask Application

Now you are going to create a Python Flask application. While this section builds a simple Python Flask application, you can use the same configuration to integrate your complex Python Flask application with FusionAuth.

First, make a directory:

   
mkdir setup-flask && cd setup-flask

Now, create a new requirements.txt file to include Python Flask. Add the flask, python-dotenv, and authlib plugins so that your requirements file looks like this:

   
flask
python-dotenv
authlib

Then, rerun pip install to install these new packages.

   
pip install -r requirements.txt

Next, create a file called .env and insert the following into it.

   
CLIENT_ID=e9fdb985-9173-4e01-9d73-ac2d60d1dc8e
CLIENT_SECRET=change-this-in-production-to-be-a-real-secret
ISSUER=http://localhost:9011
APP_SECRET_KEY=my_super_secret_key_that_needs_to_be_changed

You can now start writing the code for your Flask application. Create a new file called server.py and add the following code into it:

   
import json
from os import environ as env
from urllib.parse import quote_plus, urlencode

from authlib.integrations.flask_client import OAuth
from dotenv import find_dotenv, load_dotenv
from flask import Flask, redirect, render_template, session, url_for

ENV_FILE = find_dotenv()
if ENV_FILE:
    load_dotenv(ENV_FILE)

app = Flask(__name__)
app.secret_key = env.get("APP_SECRET_KEY")

oauth = OAuth(app)

oauth.register(
    "FusionAuth",
    client_id=env.get("CLIENT_ID"),
    client_secret=env.get("CLIENT_SECRET"),
    client_kwargs={
        "scope": "openid profile email",
        'code_challenge_method': 'S256' # This enables PKCE
    },
    server_metadata_url=f'{env.get("ISSUER")}/.well-known/openid-configuration'
)

@app.route("/login")
def login():
    return oauth.FusionAuth.authorize_redirect(
        redirect_uri=url_for("callback", _external=True)
    )


@app.route("/callback", methods=["GET", "POST"])
def callback():
    token = oauth.FusionAuth.authorize_access_token()
    session["user"] = token
    return redirect("/")


@app.route("/logout")
def logout():
    session.clear()
    return redirect("/")


@app.route("/")
def home():
    logout = env.get("ISSUER") + "/oauth2/logout?" + urlencode({"client_id": env.get("CLIENT_ID")},quote_via=quote_plus)

    return render_template(
        "home.html",
        session=session.get('user'),
        profile=json.dumps(session.get('user'), indent=2),
        logoutUrl=logout)


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=env.get("PORT", 3000))

The code uses json to process data from the FusionAuth API, os.environ, dotenv.find_dotenv, and dotenv.load_dontenv to load environment variables, urllib.parse.quote_plus and urllib.parse.urlencode to build the logout URL, authlib.integrations.flask_client.OAuth to handle OIDC verification, and various flask modules to facilitate the app’s functionality.

The login route redirects to FusionAuth to handle user authentication and the callback route, is called by FusionAuth after a successful login to generate an access token. The, logout route, simply clears the session and redirects the user to the base URL. This route will be called by FusionAuth after a successful logout from FusionAuth.

Now create a new folder called templates and navigate to it.

   
mkdir templates && cd templates

Add a new file called home.html and insert the following into it.

   
<html>
<head>
  <meta charset="utf-8" />
  <title>FusionAuth OpenID and PKCE example</title>
</head>
<body>
  {% if session %}
      <h1>You are logged in as {{session.userinfo.email}}</h1>
      <h2>Here is your OpenID profile</h2>
      <div><pre>{{profile}}</pre></div>
      <br/>

      <p><a href="{{logoutUrl}}">Logout</a></p>
  {% else %}
    <h1>Hello Guest</h1>
    <p>Please <a href="/login">Login</a> to see your profile</p>
  {% endif %}
</body>
</html>

Testing the Authentication Flow

Once you have completed the steps above, you should have a folder that is structured as follows.

   
integrate-fusionauth
|
|__ .env
|
|__ docker-compose.yml
|
|__ requirements.txt
|
|__ setup.py
|
|__ setup-flask
|  |
|  |__ .env
|  |
|  |__ requirements.txt
|  |
|  |__ server.py
|  |
|  |__ templates
|     |
|     |__ home.html
|
|__ venv
   |
   |__ ...

Navigate to the setup-flask directory and execute the following command to run your app:

   
python server.py

This should return the following.

   
 * Serving Flask app 'server.py'
 * Debug mode: off
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://localhost:5001

Testing the Authentication Flow

Open an incognito window and navigate to http://localhost:5001.

Flask application home page.

Then click Login.

Flask application login page.

Enter the email and password that you assigned to your FusionAuth user. If login is successful, you should see your OpenID profile information.

Now, click Logout. If successful, you should be brought back to the Hello Guest homepage.

The full code for this guide can be found here.

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