const express = require('express');
const { createPublicKey, verify } = require('crypto');

const app = express();
app.use(express.raw({ type: 'application/json' }));

// Cache this -- fetch once from /api/.well-known/signing-key
const PUBLIC_KEY_BASE64 = 'MCowBQYDK2VwAyEA...';

app.post('/webhooks/phoenix-pay', (req, res) => {
  const signature = req.headers['x-phoenix-pay-signature'];
  const timestamp = req.headers['x-phoenix-pay-timestamp'];
  const body = req.body.toString();

  // 1. Reject old timestamps (prevent replay attacks)
  const age = Math.floor(Date.now() / 1000) - parseInt(timestamp);
  if (age > 300) {
    return res.status(400).json({ error: 'timestamp_too_old' });
  }

  // 2. Reconstruct signing input
  const signingInput = `${timestamp}.${body}`;

  // 3. Verify Ed25519 signature
  const publicKey = createPublicKey({
    key: Buffer.from(PUBLIC_KEY_BASE64, 'base64'),
    format: 'der',
    type: 'spki',
  });

  const isValid = verify(
    null,
    Buffer.from(signingInput),
    publicKey,
    Buffer.from(signature, 'base64')
  );

  if (!isValid) {
    return res.status(401).json({ error: 'invalid_signature' });
  }

  // 4. Process the webhook
  const event = JSON.parse(body);
  console.log(`Payment ${event.payment_id}: ${event.status}`);

  // Always respond 2xx quickly
  res.status(200).json({ received: true });
});

import time
import base64
from flask import Flask, request, jsonify
from nacl.signing import VerifyKey
from nacl.exceptions import BadSignatureError

app = Flask(__name__)

# Cache this -- fetch once from /api/.well-known/signing-key
PUBLIC_KEY_BASE64 = "MCowBQYDK2VwAyEA..."

@app.route("/webhooks/phoenix-pay", methods=["POST"])
def handle_webhook():
    signature_b64 = request.headers.get("X-Phoenix-Pay-Signature")
    timestamp = request.headers.get("X-Phoenix-Pay-Timestamp")
    body = request.get_data(as_text=True)

    # 1. Reject old timestamps
    age = int(time.time()) - int(timestamp)
    if age > 300:
        return jsonify({"error": "timestamp_too_old"}), 400

    # 2. Reconstruct signing input
    signing_input = f"{timestamp}.{body}"

    # 3. Verify Ed25519 signature
    try:
        public_key_bytes = base64.b64decode(PUBLIC_KEY_BASE64)
        verify_key = VerifyKey(public_key_bytes)
        signature = base64.b64decode(signature_b64)
        verify_key.verify(signing_input.encode(), signature)
    except BadSignatureError:
        return jsonify({"error": "invalid_signature"}), 401

    # 4. Process the webhook
    event = request.get_json(force=True)
    print(f"Payment {event['payment_id']}: {event['status']}")

    return jsonify({"received": True}), 200

defmodule MyApp.PhoenixPayWebhookController do
  use MyAppWeb, :controller

  # Cache this -- fetch once from /api/.well-known/signing-key
  @public_key_base64 "MCowBQYDK2VwAyEA..."

  def handle(conn, _params) do
    [signature_b64] = get_req_header(conn, "x-phoenix-pay-signature")
    [timestamp] = get_req_header(conn, "x-phoenix-pay-timestamp")
    {:ok, body, conn} = read_body(conn)

    # 1. Reject old timestamps
    age = System.os_time(:second) - String.to_integer(timestamp)

    if age > 300 do
      conn |> put_status(400) |> json(%{error: "timestamp_too_old"})
    else
      # 2. Reconstruct signing input
      signing_input = "#{timestamp}.#{body}"

      # 3. Verify Ed25519 signature
      public_key = Base.decode64!(@public_key_base64)
      signature = Base.decode64!(signature_b64)

      if Ed25519.valid_signature?(signature, signing_input, public_key) do
        # 4. Process the webhook
        event = Jason.decode!(body)
        IO.puts("Payment #{event["payment_id"]}: #{event["status"]}")

        conn |> put_status(200) |> json(%{received: true})
      else
        conn |> put_status(401) |> json(%{error: "invalid_signature"})
      end
    end
  end
end

curl https://pay.phoenixverse.io/api/deposits/01912e4a-7b3c-7def-8a90-1234567890ab \
  -H "Authorization: Bearer eyJhbGciOiJSUzI1NiIs..."

curl https://pay.phoenixverse.io/api/deposits/ref/order-12345 \
  -H "Authorization: Bearer eyJhbGciOiJSUzI1NiIs..."