Hi folks,
I'd like to expose a few ideas about the possible inclusion of a "silent SMS"
flow within the current payment flow triggered by the navigator.mozPay API [1].
*** Why an SMS? ***
In order to charge a user for a purchased digital good via carrier billing, the
payment provider needs to identify the user as an authenticated carrier user.
The way the user is identified depends on the capabilities of the carrier's
network and on the device connection status. Some carriers provide a network
based authentication mechanism where the users can be identified and
authenticated by IP. This mechanism requires the user's device to have an
active data connection (i.e. 3G) and it obviously won't work if the user's
device is connected via WiFi. The network based authentication mechanism
provides a seamless UX where the user can be "silently" authenticated. However,
the requirements for this authentication mechanism are unfortunately not always
met, so we also need to provide fallback mechanisms as an alternative to the
network based one. One of this fallbacks is the SMS MT flow, where the user is
asked to enter her phone number, so the payment provider can send an SMS
with a challenge that the user needs to retrieve and send back to the payment
provider.
*** Why silent? ***
The above described SMS flow provides a bad UX, where the user might even need
to leave the actual payment flow to check her SMS inbox looking for the
challenge to be sent back to the payment provider. This flow is the one that it
is currently implemented for Firefox OS payments in v1 and the one that we
might be able to change with the introduction of the silent SMS flow.
With the current implementation, the first time a user wants to buy an app via
the Firefox Marketplace, she needs to go through the following steps:
1) Click on purchase the app
2) Enter her email and submit it to login with Firefox Accounts
3) Enter her password twice to create the Firefox Account
4) Enter a new PIN for the marketplace
5) Type the PIN again to confirm its right
6) Enter her phone number and mobile operator
7) Receive an SMS with a PIN
8) Enter the SMS with the PIN
9) Authorise the payment
10) Confirm the installation
As you can see, the flow is pretty painful. The idea of the silent SMS proposal
is to get rid of steps 6 to 8.
*** How? ***
There have already been a few discussions about how to implement a silent SMS
flow [2]. The comment at [3] mentions the possibility of having an SMS flow
only with SMS MO [4], which would be absolutely great, but I can't see how this
flow can work in a secure way since it is possible to replace the sender of an
SMS [5]. So I will explain my proposal based on the need of having an SMS MO
<-> SMS MT flow. However, I am including David Lozano (author of that comment)
in CC so he can explain that flow in more detail. Hopefully we might only need
to send an SMS and the flow would be significantly simpler :).
At a high level overview, the silent SMS flow would consist in the following
steps:
a. The payment provider requests the send of an SMS to a short number defined
by the carrier. The short number could be stored as a preference in the device
and might be tied to the payment provider's origin.
b. An SMS containing a randomly generated ID is sent to that short number. The
ID would be used later to identify the corresponding reply.
c. Once the carrier receives the SMS, it generates a token an replies back to
the origin number with a new SMS containing the ID and the generated token.
d. The device receives the SMS and gets back to the payment provider flow (via
DOMRequest callback) with the generated token.
e. The payment provider can use the received token to check with the carrier
the user's identity to continue with the payment process.
The first challenge here is how to achieve step (a) so we let the payment
provider request the send of an SMS knowing that the payment provider flow is
web content that has not the possibility of requesting WebSMS API permissions.
As some of you already know, the navigator.mozPay API triggers the creation of
a trusted UI that embeds the content of the payment provider flow. The API
implementation injects [6] two functions in the corresponding payment flow to
allow the payment provider to complete or cancel the payment process and to
return the control to the caller application. Basically, the idea for the
silent SMS flow is to inject an additional function in the payment flow to
allow the payment provider to request a silent SMS flow to get the user's
authentication. So the payment provider facing API would have a new function
like:
DOMRequest doSilentSMS();
This function might probably need a new explicit permission, so we let the user
choose if she wants to allow or not the payment provider to send SMSs on her
behalf. Jonas, any thought about this? You already expressed some concerns
about privacy regarding navigator.mozPay before [7].
In order to get the "silence" for this flow we will need to modify the current
SMS implementation to allow sending (step b) and receiving (step d) SMSs
without storing them in the mobile messages database. Note that depending on
the flow required by the carrier (only an SMS MT as suggested in [3]) we might
only need to modify the sending methods. Vicamo, any thoughts about this?
Sorry for the long email. Any feedback would be highly appreciated.
Cheers!
/ Fernando
[1] https://wiki.mozilla.org/WebAPI/WebPayment
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=816564
[3] https://bugzilla.mozilla.org/show_bug.cgi?id=816564#c4
[4] http://en.wikipedia.org/wiki/Short_Message_Service#Early_development
[5] http://en.wikipedia.org/wiki/SMS_spoofing
[6] https://wiki.mozilla.org/WebAPI/WebPaymentProvider#Completion
[7]
https://groups.google.com/forum/#!searchin/mozilla.dev.b2g/pay/mozilla.dev.b2g/YGITHnnjh0M/ciQO9Y_AdGoJ
_______________________________________________
dev-b2g mailing list
[email protected]
https://lists.mozilla.org/listinfo/dev-b2g
