Creating AWS Cognito User to Authenticate Postman Requests

Photo courtesy of Dan Nelson on Unsplash

Introduction

We have an API automation test suite in Postman that covers 20+ endpoints. We faced a challenge when we needed to use a user created in the Cognito User Pool exclusively for authentication to execute our test suite. Since these tests run in our deployment pipeline — right after the backend deployment — it was crucial to find a reliable solution.

Solution

We use the Cognito endpoint to generate an auth token, which is then used in subsequent requests.

Step 1: Create User

Let’s create a user in Cognito.

import time

import boto3


def create_cognito_user(user_pool_id, username, temporary_password, user_attributes):
    client = boto3.client('cognito-idp')

    response = client.admin_create_user(
        UserPoolId=user_pool_id,
        Username=username,
        TemporaryPassword=temporary_password,
        UserAttributes=user_attributes,
        MessageAction='SUPPRESS'  # To suppress sending the welcome email
    )
    time.sleep(5)

    response = client.admin_set_user_password(
        UserPoolId=user_pool_id,
        Username=username,
        Password=temporary_password,
        Permanent=True
    )

    return response


if __name__ == "__main__":
    user_pool_id = 'eu-central-test' # Change this to correct user pool id
    username = 'api-test-user' # Change username to a unique value
    temporary_password = 'i63nhN^&NQKbM1xh' # Change this  
    user_attributes = [
        {"Name": "email", "Value": "[email protected]"},
        {"Name": "email_verified", "Value": "true"},
        {"Name": "family_name", "Value": "User"},
        {"Name": "given_name", "Value": "API Test"},
        {"Name": "address",
         "Value": "{\"street_address\":\"Test Str. 11\",\"locality\":\"Berlin\",\"postal_code\":\"12683\"}"},
        {"Name": "gender", "Value": "Herr"},
        {"Name": "custom:company_name", "Value": "Test Firma"},
    
    ]

    response = create_cognito_user(user_pool_id, username, temporary_password, user_attributes)
    print(response)  

You can adjust the user attributes based on your requirements.

Step 2: Integrate User

To integrate the user created in the Cognito User Pool into our system, we trigger an event to create the user record.

To achieve this, create a Lambda function that listens for the event and consumes it accordingly. Then, trigger the function using the following test data:

{
  "source": "cognito",
  "detail-type": "userCreation",
  "detail": {
    "id": "<User ID (Sub) created from above action>",
    "email": "[email protected]",
    "firstName": "API Test",
    "lastName": "User",
    "salutation": "Herr",
    "username": "api-test-user",
    "identityProvider": "Third Party",
    "street": "Test Str. 11",
    "city": "Berlin",
    "postalCode": "12683",
    "companyName": "Test Firma",

  }
}

The above action creates a user record in the database, which is now ready to interact with other tables for CRUD operations.

Step 3: Set Up Postman

We can configure the username, password, and the specific Cognito User Pool client_id as Postman environment variables.

This POST request generates an AuthenticationResult, which includes the AccessToken.

Eventually, we can use the AccessToken to authenticate subsequent requests in Postman.