flexport-webhooks

Flexport Webhooks

When to Use This Skill

• Setting up Flexport webhook handlers
• Debugging Flexport signature verification failures (X-Hub-Signature-256)
• Understanding Flexport Event objects and milestone identifiers
• Handling shipment, shipment leg, container, document, invoice, and purchase order events

Verification (core)

Flexport signs the raw request body with HMAC keyed on your per-endpoint secret token and sends two GitHub/X-Hub-style headers, each a hex digest prefixed with the algorithm:

• X-Hub-Signature-256 — HMAC-SHA256, formatted sha256=<hex> (use this)
• X-Hub-Signature — HMAC-SHA1, formatted sha1=<hex> (legacy, being deprecated)

Verify against the raw UTF-8 body before parsing JSON, and compare timing-safe.

Node:

const crypto = require('crypto');

function verify(rawBody, signatureHeader, secret) {
  const [algo, sig] = (signatureHeader || '').split('=');
  if (algo !== 'sha256' || !sig) return false;
  const expected = crypto.createHmac('sha256', secret).update(rawBody).digest('hex');
  try {
    return crypto.timingSafeEqual(Buffer.from(sig, 'hex'), Buffer.from(expected, 'hex'));
  } catch {
    return false;
  }
}

Python:

import hmac, hashlib

def verify(raw_body: bytes, signature_header: str, secret: str) -> bool:
    algo, _, sig = (signature_header or "").partition("=")
    if algo != "sha256" or not sig:
        return False
    expected = hmac.new(secret.encode(), raw_body, hashlib.sha256).hexdigest()
    return hmac.compare_digest(sig, expected)

There is no official Flexport SDK, so verify manually in every framework.

For complete handlers with route wiring, event dispatch, and tests, see:

• examples/express/
• examples/nextjs/
• examples/fastapi/

Event Object & Dispatch

The delivered payload is a Flexport Event object. Dispatch on the type field, which holds the milestone identifier in /object#event format (note: /object#event, not object.event). The affected object is under data.