Introduction

Amazon Cognito is a powerful service provided by AWS that facilitates user sign-up, sign-in, and access control. It also provides user account verification through email or SMS. One common requirement after confirming the user account is to redirect the user to a specific URL – this is often a post-confirmation custom action. In this article, we'll explain how to achieve this redirection using a confirmation URL.

How Amazon Cognito Email Confirmation Works

When a user signs up, Amazon Cognito sends a confirmation email with a verification link. The user needs to click on the link to confirm their account and thereby complete the registration process. By default, this process does not handle custom redirection after confirmation.

Custom Redirection After Confirmation

To implement custom redirection, you need to leverage AWS Lambda functions and set up a URL that points to your redirection logic. Here's a step-by-step guide to set this up:

Step 1: Set Up AWS Lambda

1. Create a Lambda Function:
   • Navigate to the AWS Lambda console.
   • Choose "Create function" and set it up from scratch.
   • Define a name, like `UserConfirmationRedirectionFunction`, and select the Node.js or Python runtime.
2. Edit the Lambda Function:
   • Implement your business logic to run after user confirmation.
   • Configure the function to accept input events and handle output events - especially focus on success responses to achieve redirection.

Example in Python:

• Navigate to the Amazon Cognito console.
• Choose the User Pool that you are working with.
• Under "Triggers", select the "Post Confirmation" trigger.
• Attach the custom Lambda function you created.
• In the Cognito console, under "App integration", define a domain name for your user pool.
• Specify your redirect URIs within the "App integration" settings. These are the allowed destination URLs post confirmation.
• CloudWatch: Use AWS CloudWatch to keep an eye on Lambda functions for log analysis.
• AWS API Gateway: Consider wrapping your Lambda function under the AWS API Gateway to manage HTTP requests, which can help in handling various HTTP methods or advanced redirection scenarios.
• Validation: Ensure URLs and inputs in your Lambda function are fully validated to prevent attacks.
• Monitoring: Regularly audit and monitor redirects for any unexpected behavior.