Example: Python3 Flask API Authentication and Authorization

This example shows you how to create a Python3 API using Flask.

Overview

The API will have a public, private, and private-scoped route and check if a user is authenticated and authorized to access the routes. Our private routes expect an authorization header with an valid access_token in the request. The API will validate the access_token on the introspect endpoint and receives the user's roles.

The API application uses Client Secret Basic to authenticate against ZITADEL and access the introspection endpoint. You can use any valid access_token from a user or service account to send requests to the example API. In this example we will use a service account with a personal access token which can be used directly to access the example API.

  graph LR;
      User-- request auth:access_token -->API;
      API<-- get claims auth:clientSecret -->introspect_endpoint
      API-- response -->User
      subgraph backend
        API-- validate -->API
      end
      subgraph zitadel
        introspect_endpoint
      end

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Running the example

In order to run the example you need to have python3 and pip installed.

ZITADEL configuration

You need to setup a couple of things in ZITADEL. If you don't have an instance yet, please go ahead and create an instance following our Get Started Guide.

1. Create an application

Follow our guide to create a new application with type "API" and authentication method "Basic".

Save both the ClientID and ClientSecret.

2. Create a service user and PAT

Follow our guide to create a service user.

Create a personal access token, following this guide. No need to add the the user as manager.

3. Authorization

Follow this guide to create a role read:messages on your project.

Authorize the service user, by adding the role read:messages to the user.

Client configuration

You just need to create a file named .env in the directory. There is in example configuration in the .env.example file.

Set the values with the Instance Domain, Client ID, and Client Secret from the previous steps, and the client should work.

Start the service

1. Install required dependencies with pip install -r requirements.txt
2. Start the server with python3 server.py
3. Open another terminal and follow the next step to test the API

You can optionally create a virtual environment before installing the dependencies by running python3 -m venv venv

Testing the API

Public route

Try calling the public route

curl --request GET \
    --url http://127.0.0.1:5000/api/public

You should get a response with Status Code 200 and the following message.

{"message":"Public route - You don't need to be authenticated to see this."}

Private route

Try calling the private route without authorization headers

curl --request GET \
    --url http://127.0.0.1:5000/api/private

You should get a response with Status Code 401 and an error message.

So let's add an authorization header to your request. Save the personal access token for your service user to a variable.

PAT=nr9vnUTkQkn4rxWk...

Then call the private route with the PAT in the authorization header.

curl --request GET \
    --url http://127.0.0.1:5000/api/private \
    --header "authorization: Bearer $PAT"

Now you should get a response with Status Code 200 and the following message.

{"message":"Private route - You need to be authenticated to see this."}

Private route, protected

Try calling the private route that requires the user to have a certain role

curl --request GET \
    --url http://127.0.0.1:5000/api/private-scoped \
    --header "authorization: Bearer $PAT"

You should get a response with Status Code 200 and the following message.

{"message":"Private, scoped route - You need to be authenticated and have the role read:messages to see this."}

You can remove the role from the service user in ZITADEL and try again. You should then get Status Code 401, unauthorized.