Purpose

A Library for setting up login routes in a Chalice app.

Basic Usage

Below is an example of a basic application making use of a Cognito User Pool.

First set up a new Chalice app:

$ chalice new-project test-auth
$ cd test-auth

Next we add chalice-cognito-auth as a dependency:

$ echo "chalice-cognito-auth" >> requirements.txt

Now update the app.py file to configure a default user pool handler.

from chalice import Chalice

import chalice_cognito_auth


app = Chalice(app_name='test-auth')

app.experimental_feature_flags.update([
    'BLUEPRINTS',
])

user_pool_handler = chalice_cognito_auth.default_user_pool_handler()
app.register_blueprint(user_pool_handler.blueprint)


@app.route('/whoami', authorizer=user_pool_handler.auth)
def index():
    return {
        'username': user_pool_handler.current_user
    }

This will create a UserPoolHandler object using the environment variables APP_CLIENT_ID for the Cognito Userpool application client id. POOL_ID for the ID of the Cognito Userpool itself. And AWS_REGION for the region. AWS_REGION is set by the AWS Lambda runtime, but the other two we need to set ourselves. Update the file .chalice/config.json to look something like the following:

{
    "version": "2.0",
    "app_name": "test-auth",
    "environment_variables": {
        "APP_CLIENT_ID": "...client id here...",
        "POOL_ID": "...pool id here..."
    },
    "stages": {
        "dev": {
            "api_gateway_stage": "api"
        }
    }
}

Substitute the client id and pool id values for ones that match an existing cognito user pool you have and can use for testing.

Now deploy the application using:

$ chalice deploy
Creating deployment package.
Updating policy for IAM role: test-auth-dev
Updating lambda function: test-auth-dev
Updating lambda function: test-auth-dev-UserPoolAuth
Updating rest API
Resources deployed:
  - Lambda ARN: arn:aws:lambda:us-west-2:...:function:test-auth-dev
  - Lambda ARN: arn:aws:lambda:us-west-2:...:function:test-auth-dev-UserPoolAuth
  - Rest API URL: https://id.execute-api.us-west-2.amazonaws.com/api/

Now that it has been deployed we can access the API using the Rest API URL. chalice-cognito-auth injects a login route which accepts a POST request with a JSON payload containing the two keys username and password. Make sure your configured userpool has a user in it that can be used for testing and send something like the following:

$ curl -X POST -H Content-Type:application/json https://id.execute-api.us-west-2.amazonaws.com/api/login -d '{"username":"StealthyCoin", "password": "secret"}'
{"id_token":"...","refresh_token":"...","access_token":"...","token_type":"Bearer"}

The above JSON response contains all the tokens needed to send authorized requests. To test our authorizer we will use the whoami route which simply takes a request and either rejects it if unauthorized, or sends back the username associated with the request. To do this we will send a GET request with an Authorization header with the value of our id_token from the result JSON above.

In my case:

$ curl -H Authorization:...id token here... https://id.execute-api.us-west-2.amazonaws.com/api/whoami
{"username":"StealthyCoin"}

Which sends back JSON object with the username that goes with my id token.

To check that a requset with a bad authorization token is rejected, run the following curl command:

$ curl -H Authorization:foobar https://id.execute-api.us-west-2.amazonaws.com/api/whoami
{"Message":"User is not authorized to access this resource"}