🔐 Securing Webhooks with Nginx + njs (SHA-256 HMAC)

A production-ready guide to validating incoming webhooks at the Nginx layer using njs (Nginx JavaScript) and HMAC SHA-256.

📌 Overview

This setup ensures that:

Only trusted webhook sources are accepted

Payload integrity is verified using HMAC

Unauthorized or tampered requests are rejected before reaching your backend

🧱 Architecture Flow

Webhook Request → Nginx (njs validation) → Backend App
                     ⛔ Reject invalid
                     ✅ Forward valid

⚙️ Requirements

Nginx compiled with ngx_http_js_module (njs)

Backend application (e.g., Laravel running on 127.0.0.1:8000)

📁 Step 1: Create njs Validation Script

Path:

/etc/nginx/webhook_auth.js

Code:

⚙️ Step 2: Configure Nginx

🔐 Security Best Practices

✅ Use Constant-Time Comparison

Use a constant-time comparison method (if available in your njs version) to prevent timing attacks instead of:

✅ Store Secrets Securely

Avoid hardcoding secrets. Use:

Environment variables

Secret managers (e.g., Vault, AWS Secrets Manager)

✅ Enable HTTPS

✅ Rate Limiting

🧪 Testing

Generate Signature (Node.js)

Test with cURL

❌ Common Errors

Error	Cause
Missing Security Headers	Headers not sent
Invalid Store ID	Unknown store
Empty Payload	No request body
Invalid Signature	Signature mismatch

🚀 Summary

Validation is handled at the Nginx layer

Protects backend from malicious requests

Uses HMAC SHA-256 for verification

High performance and scalable

Webhook For Nginx

🔐 Securing Webhooks with Nginx + njs (SHA-256 HMAC)#

📌 Overview#

🧱 Architecture Flow#

⚙️ Requirements#

📁 Step 1: Create njs Validation Script#

⚙️ Step 2: Configure Nginx#

🔐 Security Best Practices#

✅ Use Constant-Time Comparison#

✅ Store Secrets Securely#

✅ Enable HTTPS#

✅ Rate Limiting#

🧪 Testing#

Generate Signature (Node.js)#

Test with cURL#

❌ Common Errors#

🚀 Summary#