Creating Webhook Handlers

Overview

Create secure webhook receiver endpoints with HMAC signature verification, idempotent event processing, and automatic retry handling. Support ingestion from providers like Stripe, GitHub, Twilio, and Slack with provider-specific signature validation schemes and payload parsing.

Prerequisites

• Web framework with raw body access (Express with express.raw(), FastAPI with Request.body())
• Webhook provider credentials: signing secret or shared secret key
• Persistent storage for idempotency tracking (Redis or database table for processed event IDs)
• Queue system for async processing (optional: Bull, Celery, SQS)
• ngrok or similar tunnel for local development testing

Instructions

1. Examine existing route definitions and middleware using Grep and Read to identify where webhook endpoints integrate into the application.
2. Create a dedicated webhook route (e.g., POST /webhooks/:provider) that captures the raw request body before any JSON parsing middleware runs.
3. Implement HMAC-SHA256 signature verification by computing HMAC(raw_body, signing_secret) and comparing against the provider's signature header (X-Hub-Signature-256, Stripe-Signature, X-Twilio-Signature).
4. Add idempotency protection by storing processed event IDs (e.g., evt_xxx) in Redis or a database table, rejecting duplicates with 200 OK to prevent provider retries.