Webhooks

To obtain automatic transaction updates, or for notifications were the response is delayed, Tyro Health supports the following events for each Comcare transaction:

Use cases

Partners can use webhook event notifications to alert them:

• That an invoice has been cancelled ( invoiceCancelled )
• That an invoice has been approved ( healthFundApprovedInvoice ). This would be for Comcare delayed decision transactions where the claim was approved.
• That an invoice has been rejected ( healthFundRejectedInvoice ). This would be for Comcare delayed decision transactions where the claim was paid.

Steps to receive webhooks

Use the webhooks attribute and provide:

1.URL (This is usually transaction specific)
2.Webhook event: one of the above listed events
3.Method: POST/GET/PUT/DELETE
4.Any required headers

Example

medipassTransactionSDK.renderCreateTransaction({
  ...
  webhooks: [
    {
      url: 'https://your-site.com/transactions/your-transactionId/cancelled',
      event: 'invoiceCancelled',
      method: 'POST',
      headers: { sessionKey: 'your required header' }
    },
    {
      url: 'https://your-site.com/transactions/your-transactionId/approved',
      event: 'healthFundApprovedInvoice',
      method: 'POST',
      headers: { sessionKey: 'your required header' }
    },
    {
      url: 'https://your-site.com/transactions/your-transactionId/rejected',
      event: 'healthFundRejectedInvoice',
      method: 'POST',
      headers: { sessionKey: 'your required header' }
    }
  ]

  
  ...
})

or

medipassTransactionSDK.renderCreateTransaction({
  ...
  webhooks: [
    {
      url: 'https://your-site.com/transactions/your-transactionId/event-triggers',
      event: 'invoiceCancelled,healthFundApprovedInvoice,healthFundRejectedInvoice',
      method: 'POST',
      headers: { sessionKey: 'your required header' }
    }
  ]
  ...
})

Event handling

Retries

We will attempt to retry failed webhooks if a timeout or '500' response is received from your endpoint. Retries are performed every 15 minutes for up to 24 hours or until a successful response is received.

Sequencing & ordering

We do not guarantee delivery of webhook events in the order in which they are generated. Although it is rare, payment and invoice status events could be received out of sequence.

To handle this, we suggest to use the modified timestamp to determine if an update to status is appropriate for a given transaction. Alternatively, you can use our GET Invoice API to determine to current status.

Webhook signature (optional)

To enhance the webhook security further, we support signing the payload with SHA-256 hmac signature for each of the POST <base-url>/v3/auth/token webhook we sent. This will allow your server to ensure it’s only receiving requests coming from Tyro Health.

Setup

To set up the webhook signing, please contact the customer support to apply for a secret token that will be used for signature signing. Once the secret key is generated, it will be delivered either via keybase (preferred) or secure email.

Validating requests from Tyro Health Online

Once your secret token is set by Tyro Health Online , every POST <base-url>/v3/auth/token request coming from Tyro Health Online will include two additional headers:

• X-Sender-Signature | A SHA-256 HMAC hash that's generated based on X-Sender-Timestamp value and JSON stringified payload.
• X-Sender-Timestamp | Date in ISO date string format. It represents the date the request was sent. Also, It will be used for HMAC hash calculation.

...
X-Sender-Signature=215d022a9e9c95fab7ca7c618d0d7b8d9e6dca1055d544b3d2421312a16a5651
X-Sender-Timestamp="2021-01-13T04:23:50.659Z"

To verify the hmac signature, you will need to compute your own SHA-256 HMAC signature and compare it with the signature provided in the header. So the code will be something like this:

const hmacSignature = Crypto.createHmac("sha256", SECRET_TOKEN)
                            .update(`${headers["X-Sender-Timestamp"]}${JSON.stringify(payload)}`)
                            .digest("hex");
return Crypto.timingSafeEqual(new Buffer.from(hmacSignature, "utf-8"), new Buffer.from(headers["X-Sender-Signature"], "utf-8"));

Implementation between different languages might be different. However, things to note above are:

• The HMAC function has to use SHA256 method
• The base for computing the hash is comprised of the timestamp in the header and stringified payload in the request
• Try to use timingSafeEqual equivalent function to compare the HMAC result to avoid timing attack on large string comparison