Webhooks

Listen for events so you can automatically trigger reactions.

When integrating with Dfns, you might want your applications to receive events as they occur in your Dfns account, so that your backend systems can execute actions accordingly.

To start being notified about Webhook Events, you first need to register webhooks. After you register them, Dfns can push real-time event data to your application’s webhook endpoint when events happen in your Dfns account. Dfns uses a POST http/https request to send webhook events to your app, as a JSON payload which includes a Webhook Event Object.

Receiving webhook events are particularly useful for listening to asynchronous events, such as doing a wallet transfer request.

Webhook Events

When an event occurs in the system which a Webhook is subscribed to, we create a Webhook Event object containing data around the event that happened. We then:

1. Send the event to your Webhook endpoint

2. Capture a trace of the event so you can later check all Webhook Events sent to your webhooks (through List Webhook Events or Get Webhook Event endpoints)

We only keep a trace of Webhook Events in our system for a retention period of 31 days. Past that, they are discarded, so you cannot see them using List Webhook Events or Get Webhook Event endpoints.

Here's an example of a Webhook Event of kind "wallet.transfer.requested" delivered to your webhook:

{
  "id": "wh-xxx-xxxxxxx",
  "kind": "wallet.transfer.requested",
  "date": "2023-12-04T10:02:22.280Z",
  "data": {
    "transferRequest": {
      "id": "xfr-1vs8g-c1ub1-xxxxxxxxxxxxxxxx",
      "walletId": "wa-39abb-e9kpk-xxxxxxxxxxxxxxxx",
      "network": "EthereumSepolia",
      "requester": {
        "userId": "us-3v1ag-v6b36-xxxxxxxxxxxxxxxx",
        "tokenId": "to-7mkkj-c831n-xxxxxxxxxxxxxxxx",
        "appId": "ap-24vva-92s32-xxxxxxxxxxxxxxxx"
       },
      "requestBody": {
        "kind": "Native",
        "to": "0xb282dc7cde21717f18337a596e91ded00b79b25f",
        "amount": "1000000000"
      },
      "dateRequested": "2023-05-08T19:14:25.568Z",
      "status": "Pending"
    }
  },
  "status": "200",
  "timestampSent": 1701684144,
}

Supported Webhook Events

Currently, here are the event kinds which webhooks can subscribe to ⬇️

Event Enum	Description
policy.approval.pending	A new Approval process has been created and is pending.
policy.approval.resolved	A new Approval process is finalized: it's either approved or rejected.
wallet.blockchainevent.detected	A wallet event has been detected on chain (eg. a deposit). Note: This is only available for Tier-1 chains.
wallet.created	A wallet has been created.
wallet.exported	A wallet has been exported.
wallet.delegated	A wallet has been delegated.
wallet.signature.requested	A generate signature request has been created.
wallet.signature.failed	A generate signature request has failed to process.
wallet.signature.rejected	A generate signature request with a policy approval has been rejected.
wallet.signature.signed	A generate signature request has completed.
wallet.transaction.requested	A broadcast transaction request has been created.
wallet.transaction.failed	A broadcast transaction request has failed to process.
wallet.transaction.rejected	A broadcast transaction request with a policy approval has been rejected.
wallet.transaction.broadcasted	A broadcast transaction request has been submitted to the mempool.
wallet.transaction.confirmed	A broadcast transaction request has been confirmed on chain. Note: This is only available for Tier-1 chains.
wallet.transfer.requested	A wallet transfer request has been created.
wallet.transfer.failed	A wallet transfer request has failed to process.
wallet.transfer.rejected	A wallet transfer request with a policy approval has been rejected.
wallet.transfer.broadcasted	A wallet transfer request has been submitted to the mempool.
wallet.transfer.confirmed	A wallet transfer request has been confirmed on chain. Note: This is only available for Tier-1 chains.

Webhook Event Data

Depending on its kind, every event holds data that corresponds to this kind. Here's an overview of what kind of data each event kind

• For policy.approval.pending and policy.approval.resolved, see the List Approvals response:

data

{ // Approval object
  "approval": {      
    "activityId": "cr-2100g-xxxxxxxxx",
    ...
  }
}

• For wallet.created, wallet.exported, wallet.delegated see the Get Wallet response:

data

{ // Wallet object, as in "Create Wallet" endpoint response
  "wallet": {      
    "id": "wa-xxx-xxxxxxxxx",
    ...
  }
}

• For wallet.transfer.requested, wallet.transfer.failed, wallet.transfer.rejected, wallet.transfer.broadcasted, wallet.transfer.confirmed see the Get Transfer response:

data:

{ // Wallet Transfer Request object as in "Wallet Send Transfer" endpoint
  "transferRequest": {
    "id": "xfr-xxx-xxxxxxxxx",
    "walletId": "wa-xxx-xxxxxxxx",
    ...
  }
}

• For wallet.transaction.requested, wallet.transaction.failed, wallet.transaction.rejected, wallet.transaction.broadcasted, wallet.transaction.confirmed see the Get Transaction response :

data

{ // Wallet Transaction Request as in "Wallet Broadcast Transaction" endpoint
  "transactionRequest": {
    "id": "tx-xxx-xxxxxxxxx",
    "walletId": "wa-xxx-xxxxxxxx",
    ...
  }
}

• For wallet.signature.requested, wallet.signature.failed, wallet.signature.rejected, wallet.signature.signed see the Get Signature response:

data

{ // Wallet Signature Request object as in "Wallet Generate Signature" endpoint
  "signatureRequest": {
    "id": "sig-xxx-xxxxxxxxx",
    "walletId": "wa-xxx-xxxxxxxx",
    ...
  }
}

• For wallet.blockchainevent.detected see the Get History response:

data

{ // Blockchain Event object as in "Wallet Get Wallet History" endpoint
  "kind": "Erc20Transfer",
  "contract": "0x......",
  "from": "0x......",
  "to": "0x......",
  ...
}

Webhook Event Ordering

Dfns doesn’t guarantee delivery of events in the order in which they’re generated. For example, when a wallet Transfer is picked up on-chain by our blockchain indexers, we might generate the following events:

• wallet.transfer.confirmed - this event notifies you that the Transfer Request that you made has been confirmed on chain

• wallet.blockchainevent.detected- this event notifies you of the new Blockchain Event detected and added to your Wallet History blockchain events

Your endpoint shouldn’t expect delivery of these events in this order, and needs to handle delivery accordingly.

Webhook Event Deliveries & Retries

During an webhook event delivery attempt, if we cannot reach your webhook endpoint, or if your endpoint returns anything else than a 200 status code in the response, we consider the delivery of this event has failed.

In such a case, Dfns is going to retry delivering it to your webhook, up to 5 total attempts over 24 hours, with an exponential backoff (delays from first attempt: 1m, 12min, 2h, 1d).

Every event delivery attempt will create a new Webhook Event, with its own unique ID, containing the same data than the previous event which failed delivering. So in the List Webhook Events endpoint, every Webhook Event you will see is a unique delivery attempt (potentially of the same original event).

The event that your webhook handler will receive (in your server), will include the attempt number in the payload (deliveryAttempt: 1 for the first attempt). Also, if it includes the field retryOf: "whe-xxxxxxx" , it indicates that this event you are receiving, is a "retry of" a previous Webhook Event which failed delivering.

Additionally, if you fetch Webhook Events we tried delivering, using the List Webhook Events or Get Webhook , you will be able to see the deliveryFailed boolean field indicating if delivery succeeded or not, as well as the nextAttemptDate: "2024-01-24-xxxxxx" date showing you around which time the next delivery attempt to your webhook will occur (if delivery failed).

If you want to fetch all Webhook Events which failed delivering to your webhook, you can use the List Webhook Events with the query parameter deliveryFailed=true. And amongst all those returned, you can see those which failed delivering, and will not retry in future (because reached maximum retry attempt), by filtering those which have no nextAttemptDate .

If your webhook has been disabled or deleted when Dfns attempts a retry, future retries of that event are prevented. However, if you disable and then re-enable a webhook endpoint before Dfns can retry, you can still expect to see future retry attempts.

Webhooks best practices

Review these best practices to make sure your Webhooks remain secure and work properly.

Respond quickly with a 200

The webhook event handler defined on your server, when it receives a new event from Dfns, should be quick to handle it, and return quickly a 200 status code to indicate that the event was indeed delivered. If your handler expects to do some processing taking longer than a few seconds, you should consider adding this to a queue for processing on your side. Otherwise the request delivering the event might timeout.

Also, your handler should catch any error that happens on your side, so it still respond with a 200 response to Dfns, indicating that you received it already, otherwise the same event might be retried a few times and fail all the same.

Verify events are sent from Dfns

Verify webhook signatures to confirm that received events are sent from Dfns. Dfns signs webhook events it sends to your endpoints by including a signature in each event’s X-DFNS-WEBHOOK-SIGNATURE header. This allows you to verify that the events were sent by Dfns, not by a third party.

Dfns signatures is a HMAC of the received event payload, using SHA-256 hash function and the webhook secret as the secret. It has this shape:

X-DFNS-WEBHOOK-SIGNATURE: sha256=33008aa9673b764cc752362034dfe49ef466315c45d62b3e8cb8588b23d0d06a

Here is an example function showing how you can validate the webhook event signature:

NodeJS

const crypto = require('crypto')

const WEBHOOK_SECRET = process.env.WEBHOOK_SECRET // the webhook secret you got upon webhook creation
const REPLAY_ATTACK_TOLERANCE = 5 * 60 // 5 minutes

function verifyDfnsWebhookSignature(eventPayload, eventSignature) {
  const messageToSign = JSON.stringify(eventPayload) // this assumes "eventPayload" was already JSON-parsed, and is an object (the full payload of the webhook event)

  const signature = crypto
    .createHmac('sha256', WEBHOOK_SECRET)
    .update(messageToSign)
    .digest('hex')

  const trustedSig = Buffer.from(`sha256=${signature}`, 'ascii')
  const untrustedSig = Buffer.from(eventSignature, 'ascii')

  const isSignatureValid = crypto.timingSafeEqual(trustedSig, untrustedSig) // using a constant-time equality comparison (to avoid timing attacks)

  const now = new Date().getTime() / 1000 // your server unix timestamp
  const isTimestampWithinTolerance = Math.abs(now - eventPayload.timestampSent) < REPLAY_ATTACK_TOLERANCE

  return isSignatureValid && isTimestampWithinTolerance
}

Only listen to event types your integration requires

Configure your webhook endpoints to receive only the types of events required by your integration. Listening for extra events (or all events) puts undue strain on the server and we don’t recommend it.

Handle duplicate events

Webhook endpoints might occasionally receive the same event more than once. You can guard against duplicated event receipts by making sure your your event processing is idempotent.

Receive events with an HTTPS server

If you use an HTTPS URL for your webhook, we validate that the connection to your server is secure before sending your webhook data. For this to work, your server must be correctly configured to support HTTPS with a valid server certificate.

Exempt webhook route from CSRF protection

If you’re using Rails, Django, or another web framework, your site might automatically check that every POST request contains a CSRF token. This is an important security feature that helps protect you and your users from cross-site request forgery attempts. However, this security measure might also prevent your site from processing legitimate events. If so, you might need to exempt the webhooks route from CSRF protection.

Rails

class DfnsController < ApplicationController
  # If your controller accepts requests other than webhooks,
  # you'll probably want to use `protect_from_forgery` to add CSRF
  # protection for your application. But don't forget to exempt
  # your webhook route!
  protect_from_forgery except: :webhook

  def webhook
    # Process webhook data in `params`
  end
end

Django

import json

# Webhooks are always sent as HTTP POST requests, so ensure
# that only POST requests reach your webhook view by
# decorating `webhook()` with `require_POST`.
#
# To ensure that the webhook view can receive webhooks,
# also decorate `webhook()` with `csrf_exempt`.
@require_POST
@csrf_exempt
def webhook(request):
  # Process webhook data in `request.body`

Local Development

To add a new webhook, you first need a http server which can receive requests from public internet.

During development, one way to achieve this (without deploying a new server on a cloud provider), is to spin up a local server on your machine (localhost), and then use a tunnel services (eg https://ngrok.com) to create a public url pointing to your local server.

As an example, here are steps to create a basic Express server in NodeJS:

• Create a new npm project, install express

mkdir basic-server && cd basic-server
npm init
npm install express

• Add a new file index.js :

const express = require('express')

const app = express()
const port = 3000

app.use(express.json())

app.post('/', (req) => {
  console.log('Received event:', req.body)
})

app.listen(port, () => {
  console.log(`Listening on port ${port}`)
})

• In one terminal, run your server

node index.js

• In another terminal, start a ngrok tunnel pointing to your local server

ngrok http 3000

• Now, you can Create a Webhook using the url displayed in the result of above the terminal (looking like "https://xxxxxx.ngrok-free.dev"), and test that the webhook is setup properly by using Ping Webhook. If properly setup, you should see incoming events received by your local server.

If you use a free Ngrok account, every time you re-launch the tunnel you'll get a new url, so make sure you update the Dfns webhook url to test.