Python

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Python

Gravatar for andres.aguiar@auth0.com
By Andres Aguiar
Auth0

This tutorial demonstrates how to add user login to a Python web Application built with the Flask framework. We recommend you to Log in to follow this quickstart with examples configured for your account.

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System requirements: Python 2.7, 3.0 and up | Flask 0.10.1 and up | Python-dotenv 0.6.5 and up | Requests 2.3.0 and up | Flask-oauthlib 0.9.4 and up | Six 1.10.0 and up

New to Auth? Learn How Auth0 works, how it integrates with Regular Web Applications and which protocol it uses.

Configure Auth0

Get Your Application Keys

When you signed up for Auth0, a new application was created for you, or you could have created a new one.

Your will need some details about that application to communicate with Auth0. You can get these details from the Application Settings section in the Auth0 dashboard.

You need the following information:

  • Client ID
  • Domain

If you download the sample from the top of this page these details are filled out for you.

If you have more than one application in your account, the sample comes with the values for your Default App.

App Dashboard

Configure Callback URLs

A callback URL is a URL in your application where Auth0 redirects the user after they have authenticated.

You need to whitelist the callback URL for your app in the Allowed Callback URLs field in your Application Settings. If you do not set any callback URL, your users will see a mismatch error when they log in.

If you are following along with the sample project you downloaded from the top of this page, you should set the Callback URL to http://localhost:3000/callback.

Configure Flask to Use Auth0

Add the Dependencies

This example uses Flask and the Authlib OAuth library.

Add the following dependencies to your requirements.txt and run pip install -r requirements.txt.

// /requirements.txt

flask
python-dotenv
requests
authlib
six

Initialize Authlib

Create a file named server.py, and instantiate an application with your client keys, scopes, and OAuth endpoints.

# /server.py

from functools import wraps
import json
from os import environ as env
from werkzeug.exceptions import HTTPException

from dotenv import load_dotenv, find_dotenv
from flask import Flask
from flask import jsonify
from flask import redirect
from flask import render_template
from flask import session
from flask import url_for
from authlib.flask.client import OAuth
from six.moves.urllib.parse import urlencode

app = Flask(__name__)

oauth = OAuth(app)

auth0 = oauth.register(
    'auth0',
    client_id='YOUR_CLIENT_ID',
    client_secret='YOUR_CLIENT_SECRET',
    api_base_url='https://YOUR_AUTH0_DOMAIN',
    access_token_url='https://YOUR_AUTH0_DOMAIN/oauth/token',
    authorize_url='https://YOUR_AUTH0_DOMAIN/authorize',
    client_kwargs={
        'scope': 'openid profile',
    },
)

Add the Callback Handler

This handler exchanges the code that Auth0 sends to the callback URL for an Access Token and an ID Token.

The Access Token will be used to call the /userinfo endpoint to get the user profile. After the user information is obtained, store then in the flask session.

# /server.py

# Here we're using the /callback route.
@app.route('/callback')
def callback_handling():
    # Handles response from token endpoint
    auth0.authorize_access_token()
    resp = auth0.get('userinfo')
    userinfo = resp.json()

    # Store the user information in flask session.
    session['jwt_payload'] = userinfo
    session['profile'] = {
        'user_id': userinfo['sub'],
        'name': userinfo['name'],
        'picture': userinfo['picture']
    }
    return redirect('/dashboard')

Trigger Authentication

Add a /login route that uses the Authlib client instance to redirect the user to the login page.

# /server.py

@app.route('/login')
def login():
    return auth0.authorize_redirect(redirect_uri='YOUR_CALLBACK_URL', audience='https://YOUR_AUTH0_DOMAIN/userinfo')

Create a home.html file in a /template folder. Add a link to the /login route.

<div class="login-box auth0-box before">
    <img src="https://i.cloudup.com/StzWWrY34s.png" />
    <h3>Auth0 Example</h3>
    <p>Zero friction identity infrastructure, built for developers</p>
    <a class="btn btn-primary btn-lg btn-login btn-block" href="/login">Log In</a>
</div>

Check if the user is authenticated

Add the following decorator to your Flask app. Use it to decorate methods that require authentication.

You should import wraps first, adding the following line to your server.py file: from functools import wraps.

# /server.py

def requires_auth(f):
  @wraps(f)
  def decorated(*args, **kwargs):
    if 'profile' not in session:
      # Redirect to Login page here
      return redirect('/')
    return f(*args, **kwargs)

  return decorated

Display User Information

Add a /dashboard route to server.py that will render the user information stored in the Flask session.

Decorate it with @requires_auth. It will only be accessible if the user has been authenticated.

# /server.py

@app.route('/dashboard')
@requires_auth
def dashboard():
    return render_template('dashboard.html',
                           userinfo=session['profile'],
                           userinfo_pretty=json.dumps(session['jwt_payload'], indent=4))

Add a dashboard.html file in a /template folder to display the user information.

Add a link to allow users to Log Out.

<div class="logged-in-box auth0-box logged-in">
    <h1 id="logo"><img src="//cdn.auth0.com/samples/auth0_logo_final_blue_RGB.png" /></h1>
    <img class="avatar" src="{{userinfo['picture']}}"/>
    <h2>Welcome {{userinfo['name']}}</h2>
    <pre>{{userinfo_pretty}}</pre>
    <a class="btn btn-primary btn-lg btn-logout btn-block" href="/logout">Logout</a>
</div>

Logout

To log the user out, you have to clear the data from the session, and redirect the user to the Auth0 logout endpoint. You can find more information about this in our documentation logout documentation.

# /server.py

@app.route('/logout')
def logout():
    # Clear session stored data
    session.clear()
    # Redirect user to logout endpoint
    params = {'returnTo': url_for('home', _external=True), 'client_id': 'YOUR_CLIENT_ID'}
    return redirect(auth0.base_url + '/v2/logout?' + urlencode(params))

Please take into consideration that the return to URL needs to be in the list of Allowed Logout URLs in the settings section of the client as explained in our documentation

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