Webhook Signature Contract Repair

The problem

Webhook verification logic often drifts across middleware, request parsers, and background workers, leading to security gaps like parse-before-verify vulnerabilities or broken idempotency. Developers struggle to repair these fragile integration points without risking production outages or replaying sensitive customer data.

What it does

• Identifies parse-before-verify bugs, JSON re-serialization issues, and encoding mismatches in your request handlers.
• Traces webhook lifecycles from raw-byte capture through signature verification, event dispatch, and queue execution.
• Standardizes provider-specific contracts for headers, algorithms, timestamp tolerance, and secret rotation.
• Implements durable idempotency boundaries to prevent duplicate side effects in workers and retries.
• Generates small, reviewable repository patches and deterministic local tests using synthetic fixtures.

Why this beats prompting it yourself

General-purpose LLMs often suggest insecure shortcuts like bypassing verification in development or using unstable JSON stringification for signature checks. This skill enforces a strict security-first architecture that separates cryptographic validity from payload parsing and ensures exact-byte integrity across your entire stack.

Use cases

• Fixing webhook failures caused by middleware whitespace or encoding changes.
• Implementing secure secret rotation with explicit key IDs and overlap periods.
• Migrating process-local replay protection to durable, worker-safe idempotency.
• Redacting sensitive payloads and signatures from application logs.

Known limitations

Cannot contact live provider APIs, rotate production secrets, or verify historical events. Works only with repository files and materials provided in the environment.