Webhooks

import crypto from "node:crypto";

/**
 * Checks a Crypto Merchant webhook and returns the event.
 * rawBody: the request body exactly as it arrived (string or Buffer).
 */
export function verifyWebhook(rawBody, signatureHeader, secret, toleranceSec = 300) {
  const parts = Object.fromEntries(
    String(signatureHeader ?? "")
      .split(",")
      .map((part) => part.trim().split("=")),
  );
  const t = parts.t;
  const v1 = parts.v1 ?? "";
  if (!t || !v1) throw new Error("Missing signature");

  const body = Buffer.isBuffer(rawBody) ? rawBody.toString("utf8") : rawBody;
  const expected = crypto
    .createHmac("sha256", secret) // your endpoint secret, whsec_…
    .update(`${t}.${body}`)
    .digest("hex");

  const a = Buffer.from(expected);
  const b = Buffer.from(v1);
  if (a.length !== b.length || !crypto.timingSafeEqual(a, b)) {
    throw new Error("Bad signature");
  }
  if (Math.abs(Date.now() / 1000 - Number(t)) > toleranceSec) {
    throw new Error("Timestamp too old");
  }
  return JSON.parse(body);
}

import express from "express";
import { verifyWebhook } from "./verify-webhook.js";
import { db } from "./db.js"; // your database, e.g. a pg Pool

// CREATE TABLE webhook_events (
//   id text PRIMARY KEY, type text NOT NULL, payload jsonb NOT NULL,
//   received_at timestamptz NOT NULL DEFAULT now(), processed_at timestamptz
// );

const app = express();

// Keep the raw body: re-serialised JSON would not match the signature.
app.post(
  "/webhooks/crypto-merchant",
  express.raw({ type: "application/json" }),
  async (req, res) => {
    let event;
    try {
      event = verifyWebhook(req.body, req.get("CM-Signature"), process.env.CM_WEBHOOK_SECRET);
    } catch {
      return res.sendStatus(400);
    }

    try {
      // 1. Save the event before replying. A repeat delivery has the same id and is ignored.
      await db.query(
        "INSERT INTO webhook_events (id, type, payload) VALUES ($1, $2, $3) ON CONFLICT (id) DO NOTHING",
        [event.id, event.type, event],
      );
    } catch {
      return res.sendStatus(500); // not saved: we send it again later
    }

    // 2. It's stored, so confirm it.
    res.sendStatus(200);

    // 3. Do the work from what you saved, here or in a background job.
    //    If your server stops now, the event is still waiting in the table.
    processEvents().catch(console.error);
  },
);

async function processEvents() {
  const { rows } = await db.query(
    "SELECT payload FROM webhook_events WHERE processed_at IS NULL ORDER BY received_at",
  );
  for (const { payload: event } of rows) {
    if (event.type === "invoice.paid") {
      // Mark the order in event.data.order_id as paid. Doing it twice must change nothing.
    }
    await db.query("UPDATE webhook_events SET processed_at = now() WHERE id = $1", [event.id]);
  }
}

import hashlib, hmac, json, time

def verify_webhook(raw_body: bytes, signature_header: str, secret: str, tolerance_sec: int = 300) -> dict:
    """Checks a Crypto Merchant webhook and returns the event. raw_body: the request body exactly as it arrived."""
    parts = dict(part.strip().split("=", 1) for part in (signature_header or "").split(",") if "=" in part)
    t, v1 = parts.get("t"), parts.get("v1")
    if not t or not v1:
        raise ValueError("Missing signature")
    signed = t.encode() + b"." + raw_body
    expected = hmac.new(secret.encode(), signed, hashlib.sha256).hexdigest()  # your endpoint secret, whsec_…
    if not hmac.compare_digest(expected, v1):
        raise ValueError("Bad signature")
    if abs(time.time() - int(t)) > tolerance_sec:
        raise ValueError("Timestamp too old")
    return json.loads(raw_body)

<?php
// Checks a Crypto Merchant webhook and returns the event.
// Read the raw body with file_get_contents('php://input') and the header with $_SERVER['HTTP_CM_SIGNATURE'].
function verify_webhook(string $rawBody, string $signatureHeader, string $secret, int $toleranceSec = 300): array {
    $parts = [];
    foreach (explode(',', $signatureHeader) as $part) {
        [$key, $value] = array_pad(explode('=', trim($part), 2), 2, '');
        $parts[$key] = $value;
    }
    $t = $parts['t'] ?? '';
    $v1 = $parts['v1'] ?? '';
    if ($t === '' || $v1 === '') {
        throw new RuntimeException('Missing signature');
    }
    $expected = hash_hmac('sha256', $t . '.' . $rawBody, $secret); // your endpoint secret, whsec_…
    if (!hash_equals($expected, $v1)) {
        throw new RuntimeException('Bad signature');
    }
    if (abs(time() - (int) $t) > $toleranceSec) {
        throw new RuntimeException('Timestamp too old');
    }
    return json_decode($rawBody, true, 512, JSON_THROW_ON_ERROR);
}