Introduction: In this knowledge base article, we will provide you with Python code snippets for validating HMAC signatures in webhook requests received from HashiCorp Cloud Platform (HCP).
It demonstrates a serverless approach through AWS lambda function to handle webhook events from HCP, perform actions based on the event type, and integrate with external services like GitHub and Slack for automation and notifications.
Webhook requests from HCP include an X-HCP-Webhook-Signature header containing an HMAC signature computed using the SHA-512 digest algorithm. It's crucial to validate this signature to ensure the authenticity and integrity of incoming webhook requests.
Prerequisites:
- Basic understanding of Python programming language
- Familiarity with handling HTTP requests and headers
Python Code for HMAC Validation:
Explanation:
This Python code is intended to handle webhook events received from HashiCorp Cloud Platform (HCP) and perform various actions based on the event type. Let's break down the code and understand its functionality:
Importing Libraries: The code begins by importing necessary libraries such as os, json, urllib3, hmac, and hashlib.
Lambda Handler Function: The lambda_handler function is the entry point for AWS Lambda. It receives the event and context parameters.
Verifying HMAC Signature: The function first checks if the HMAC signature is provided in the request headers. If not provided, it returns a 403 Forbidden response.
Validating HMAC: The verify_hmac function computes the HMAC using the secret token and compares it with the signature from the request headers to ensure the authenticity of the webhook request.
Event Action Functions: Depending on the value of the event_action attribute in the request body, different actions are performed. These actions include verification, revocation, completion, and deletion of images.
Helper Functions: Several helper functions are defined to perform specific tasks such as retrieving secrets, triggering GitHub actions, sending Slack notifications, and extracting image IDs from the request payload.
Handling Webhook Events: The code processes webhook events received from HCP, validates HMAC signatures, and performs corresponding actions based on the event type.
Error Handling: The code includes error handling mechanisms to handle cases where HMAC validation fails or certain operations encounter errors.
Conclusion: By implementing the provided Python code for HMAC signature validation, you can ensure the authenticity and integrity of webhook requests received from HashiCorp Cloud Platform. Incorporate this code into your webhook receiver logic to enhance the security of your applications and services.
References:
https://developer.hashicorp.com/hcp/docs/hcp/admin/projects/webhooks#viewing-and-managing-webhooks
https://developer.hashicorp.com/hcp/docs/hcp/admin/projects/webhooks#webhook-authenticity