Click to Pay - Hosted Payment Page

Mastercard Click to Pay securely stores users credit cards so that they can retrieve them during a checkout process. You can direct this integration to retrieve a particular user's cards by providing the email or mobile query parameters in the request.

Mastercard Click to Pay will also remember users across different checkout sessions, even across different merchants. If the user is known via this route, they will be taken straight to their list of cards within the "User Flow" section shown below.

User Flow

When these parameters are passed, this integration will automatically perform a Click to Pay user lookup. If the user is found, then the user will be prompted to enter an OTP code to verify themselves with the Click to Pay system:

If the OTP code is correct, then the user will be shown a list of their cards:

When the card is selected, the confirmation screen appears:

Clicking "Confirm payment" will show the Mastercard Click to Pay confirmation loading screen while the payment is being processed:

Once the payment has been processed, you will see a receipt screen:

Alternatively, if you have provided a return_path parameter during the initial checkout flow, the user will be redirected to that path instead.

URLs

There are two different URLs for the PayNow service - one for the Sandbox environment and one for the Live environment:

Request

In order to direct the customer to the hosted payment page the merchants website should prepare the following URL and either use this as the redirect destination, or as the IFRAME source:

https://paynow.pmnts.io/v3/clicktopay/[username]/[reference]/[currency]/[amount]/[hash]

User identification URL Parameters

The Click to Pay integration also allows you to pass in two parameters to identify your users.

If you pass both, a lookup will be attempted first for email, and then mobile.

URL Parameters

The following parameters are required and are used to build the URL which the user should be redirected to (or as the source for the IFRAME):

Options

Provide any of the following as query parameters to specify display options - these are optional parameters:

Note on external CSS: When external CSS specified in the options the hosted payment page a number of verification and sanitisation steps are taken before rendering the CSS in the page, including:

• Verifying the URL specified is served over HTTPS and is in-fact a CSS file
• Verifying that the css_signature matches the URL
• Scrubbing any potentially dangerous CSS statements from the file

After successful verification and sanitising , the filtered CSS is cached by the Hosted Payment Page for 5 minutes. If the cache needs to be updated, the following options are available:

• Change the URL and update the signature to reflect - the CSS cache uses the filename and merchant ID as the cache key, so changing this will force the cache to be updated

Verification Value Calculation

There are two points of verification for requests - once when the request is received by Fat Zebra (when the hosted page is rendered to the user), and once when the response is returned to the merchant - it is important that the response is verified by the merchant to ensure that the response has not been tampered with by malicious users.

Request Verification (Redirect to Fat Zebra)

The request received by Fat Zebra will be verified with the following steps:

1. The reference, currency, amount will be concatenated into a string, joined by colons:

https://paynow.pmnts.io/v3/clicktopay/samsbooks/INV1121/AUD/100.25/xxxxxxxxxxx -> "INV1121:100.25:AUD"

2. The value of this string will then be hashed with a HMAC-MD5, using the shared-secret known by Fat Zebra and the merchant (please contact Fat Zebra Support if you are unsure of where to find this shared secret).

shared_secret = "<<sharedSecret>>"
verification = hmac_md5(shared_secret, "INV1121:100.25:AUD")

Response Verification (Purchases)

For purchases the response verification will consist of the response code, success indicator, amount, currency, transaction ID and the card token:

https://www.samsbooks.com/payment/callback?r=1&successful=true&amount=10025&currency=AUD&id=001-P-ABCDG1124&token=abcd1234&v=xxxxx....... -> "1:true:10025:AUD:001-P-ABCDG1123:abcd1234"
shared_secret = "<<sharedSecret>>"
verification = hmac_md5(shared_secret, "1:true:10025:AUD:001-P-ABCDG1123:abcd1234")
 
# v == verification should be true

The response for purchases will also include the following:

The following Click to Pay transaction metadata will also be appended where available:

Response Verification (Tokenization)

For tokenization the response verification will consist of the response code, and the card token:

https://www.samsbooks.com/payment/callback?r=1&token=abcd1234&v=xxxxxxxxx........ -> "1:abcd1234"
shared_secret = "<<sharedSecret>>"
verification = hmac_md5(shared_secret, "1:abcd1234")
# v == verification should be true

The response for tokenization will also include the following:

The following Click to Pay transaction metadata will also be appended where available:

Response Codes

The following response codes are used when a redirect URL is provided: