Webhooks

Pay can be configured to send webhook events to notify your application any time an event happens on your transaction. Pay sends a response, via a HTTP request, to any endpoint URLs that you have provided us in the Pay dashboard.

To listen to events, create a webhook in the Pay dashboard. Webhook URLs must start with https://.

Triggered when a transaction is confirmed onchain. This event provides information about the new status of the order and its transactionHash, as well as other relevant information.

Example Response:

{
  "data": {
    "buyWithFiatStatus": {
      "intentId": "f4cf8ab7-bb62-4b3b-a180-70fc7d72446c",
      "status": "ON_RAMP_TRANSFER_COMPLETED",
      "toAddress": "0xebfb127320fcbe8e07e5a03a4bfb782219f4735b",
      "quote": {
        "createdAt": "2024-06-18T23:46:46.024Z",
        "fromCurrency": {
          "amountUnits": "279",
          "amount": "2.79",
          "currencySymbol": "USD",
          "decimals": 2,
          "amountUSDCents": 279
        },
        "fromCurrencyWithFees": {
          "amountUnits": "294",
          "amount": "2.94",
          "currencySymbol": "USD",
          "decimals": 2,
          "amountUSDCents": 279
        },
        "onRampToken": {
          "chainId": 137,
          "tokenAddress": "0xeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
          "name": "Matic",
          "symbol": "MATIC",
          "decimals": 18,
          "priceUSDCents": 54.797200000000004
        },
        "toToken": {
          "chainId": 137,
          "tokenAddress": "0xeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
          "name": "Matic",
          "symbol": "MATIC",
          "decimals": 18,
          "priceUSDCents": 54.797200000000004
        },
        "estimatedOnRampAmountWei": "5000000000000000000",
        "estimatedOnRampAmount": "5",
        "estimatedToTokenAmount": "5",
        "estimatedToTokenAmountWei": "5000000000000000000",
        "estimatedDurationSeconds": 30
      },
      "source": {
        "completedAt": "2024-06-18T23:49:00.347Z",
        "amount": "5",
        "amountWei": "5000000000000000000",
        "token": {
          "chainId": 137,
          "tokenAddress": "0xeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
          "name": "Matic",
          "symbol": "MATIC",
          "decimals": 18,
          "priceUSDCents": 54.797200000000004
        },
        "transactionHash": "0x4bb089f6a60b49235a817b52bf39bc078f1246df15731b85837526bb62cf4e70",
        "explorerLink": "https://polygonscan.com/tx/0x4bb089f6a60b49235a817b52bf39bc078f1246df15731b85837526bb62cf4e70",
        "amountUSDCents": 275
      }
    }
  }
}

Since any outside origin can call your webhook endpoint, it is recommended to verify the webhook signature to ensure a request comes from your Pay instance.

The payload body is signed with the webhook secret and provided in the X-Pay-Signature request header.

Get the webhook secret for your webhook endpoint from the dashboard.

This code example checks if the signature is valid:

const generateSignature = (
  body: string,
  timestamp: string,
  secret: string,
): string => {
  const payload = `${timestamp}.${body}`;
  return crypto
    .createHmac("sha256", secret)
    .update(payload)
    .digest("hex");
};
 
const isValidSignature = (
  body: string,
  timestamp: string,
  signature: string,
  secret: string,
): boolean => {
  const expectedSignature = generateSignature(
    body,
    timestamp,
    secret,
  );
  return crypto.timingSafeEqual(
    Buffer.from(expectedSignature),
    Buffer.from(signature),
  );
};

Check the timestamp The event timestamp is provided in the X-Pay-Timestamp request header.

This code example checks if the event exceeds a given expiration duration:

export const isExpired = (
  timestamp: string,
  expirationInSeconds: number,
): boolean => {
  const currentTime = Math.floor(Date.now() / 1000);
  return currentTime - parseInt(timestamp) > expirationInSeconds;
};

This NodeJS code example listens for event notifications on the /webhook endpoint:

import express from "express";
import bodyParser from "body-parser";
import { isValidSignature, isExpired } from "./webhookHelper";
 
const app = express();
const port = 3000;
 
const WEBHOOK_SECRET = "<your_webhook_auth_secret>";
 
app.use(bodyParser.text());
 
app.post("/webhook", (req, res) => {
  const signatureFromHeader = req.header("X-Pay-Signature");
  const timestampFromHeader = req.header("X-Pay-Timestamp");
 
  if (!signatureFromHeader || !timestampFromHeader) {
    return res
      .status(401)
      .send("Missing signature or timestamp header");
  }
 
  if (
    !isValidSignature(
      req.body,
      timestampFromHeader,
      signatureFromHeader,
      WEBHOOK_SECRET,
    )
  ) {
    return res.status(401).send("Invalid signature");
  }
 
  if (isExpired(timestampFromHeader, 300)) {
    // Assuming expiration time is 5 minutes (300 seconds)
    return res.status(401).send("Request has expired");
  }
 
  // Process the request
  res.status(200).send("Webhook received!");
});
 
app.listen(port, () => {
  console.log(`Server started on http://localhost:${port}`);
});