Getting Access Token from Amazon Cognito using Postman

Amazon Cognito is a user authentication and management service that allows you to easily add authentication to your web and mobile applications. In this article, we will explore how to get an access token from Amazon Cognito using Postman, focusing on the Authorization Code Grant and Implicit Grant.

Authorization Code Grant

The Authorization Code Grant is a method for getting an access token from Amazon Cognito that is suitable for web applications. It involves the following steps:

1. Register your web application with Amazon Cognito to obtain a client ID and client secret.
2. Redirect the user to the Amazon Cognito authorization endpoint, passing along your client ID, desired scopes, redirect URI, and response type (code).
3. The user will be prompted to log in and authenticate themselves. Once authenticated, Amazon Cognito will redirect the user back to your web application with an authorization code in the URL query string.
4. Use the authorization code to make a POST request to the Amazon Cognito token endpoint, including your client ID, client secret, redirect URI, grant type (authorization_code), and the authorization code.
5. Amazon Cognito will respond with an access token, which you can use to make authenticated requests to your backend APIs.

Implicit Grant

The Implicit Grant is a method for getting an access token from Amazon Cognito that is suitable for single-page applications and mobile apps. It involves the following steps:

1. Register your client application with Amazon Cognito to obtain a client ID.
2. Redirect the user to the Amazon Cognito authorization endpoint, passing along your client ID, desired scopes, redirect URI, and response type (token).
3. The user will be prompted to log in and authenticate themselves. Once authenticated, Amazon Cognito will redirect the user back to your client application with an access token in the URL fragment.
4. You can then extract the access token from the URL fragment and use it to make authenticated requests to your backend APIs.

Now that we have a basic understanding of the Authorization Code Grant and Implicit Grant, let’s explore how to use Postman to obtain an access token from Amazon Cognito.

Using Postman

To use Postman to obtain an access token from Amazon Cognito, you will need to create a new request and configure it as follows:

1. Set the request method to POST.
2. Set the request URL to the Amazon Cognito token endpoint.
3. Set the Content-Type header to application/x-www-form-urlencoded.
4. Add the following parameters to the request body:
   • grant_type: authorization_code or implicit, depending on the grant type you are using
   • client_id: your client ID
   • client_secret: your client secret (for the Authorization Code Grant only)
   • redirect_uri: your redirect URI
   • code: the authorization code (for the Authorization Code Grant only)
5. Click Send to make the request.

Once the request is successful, you will receive a response containing the access token, which you can then use to make authenticated requests to your backend APIs.

By following the steps outlined in this article, you should now be able to successfully obtain an access token from Amazon Cognito using Postman, using either the Authorization Code Grant or Implicit Grant.