On Sep 4, 2013, at 6:04 PM, Ehsan Akhgari <[email protected]> wrote:
> On 2013-09-04 5:03 PM, Kumar McMillan wrote: >> Hi all, >> >> After gaining much experience using navigator.mozPay() >> (https://wiki.mozilla.org/WebAPI/WebPayment) to implement Firefox OS >> payments it feels like the API may not be useful as a generic API for the >> broader web. I'd like to propose deprecating navigator.mozPay() and >> replacing it with lower-level primitives that payment providers can use >> directly. Thoughts and feedback on this? >> >> The problem: mozPay() adds some features for carrier billing but does so by >> imposing a rigid end to end transaction flow. Not all payment providers need >> to adopt this end to end flow and many providers already have their own end >> to end flow. Awkwardly, mozPay also has a whitelist of who can use it which >> means Mozilla (or whoever builds B2G) has to grant access to each provider. >> >> mozPay comes in two parts: >> >> * Developers use navigator.mozPay() to conduct a transaction and disperse >> digital goods within their app. This is roughly the equivalent of doing >> window.open() and using postMessage to communicate with the new window. >> * Whitelisted payment providers (such as Firefox Marketplace) host their >> custom payment flow in an iframe controlled by the chrome layer of mozPay. >> That iframe has a special global called window.mozPaymentProvider which is >> defined here: https://wiki.mozilla.org/WebAPI/WebPaymentProvider >> >> I'd like to propose deprecating mozPay and instead figuring out a way to >> securely expose mozPaymentProvider since it exposes primitives that websites >> can use to implement mobile payments themselves. This would be a big win for >> Firefox OS: anyone on the web could process payments just the same as >> Mozilla does. >> >> What are the exact primitives we need to expose? >> >> 1. To optimize carrier billing authentication mozPaymentProvider provides an >> observeSilentSms method. This allows the payment provider to exchange a >> challenge/response via SMS to get an unspoofable link to the user's phone >> bill. We could expose this to all web content but we couldn't allow >> arbitrary numbers if it were publicly accessible. We would have to whitelist >> the short codes that can be used in this function (a short code incurs no >> cost to the user; it is paid for by the payment authority). We might also >> need to prevent DOS'ing a short code? There won't be too many of these to >> whitelist. Mozilla could also host a web service for the whitelist which >> would make it easy to maintain. >> >> This covers the use case we have for Mozilla's carrier billing and it is a >> somewhat typical pattern. FaceTime registration works via silent SMS: >> http://theiphonewiki.com/wiki/FaceTime#FaceTime_Activation_.2F_Registration >> >> (Note that some operators support HTTP header injection to link to a user's >> phone bill. In that case, the web doesn't need a new API; you can use HTTP >> redirects.) > > Would that not tie us down to the payment providers who use one of the > white-listed numbers? I suppose it would, yes. However, the current mozPay already ties us down to white-listed payment providers, only more brutally. If we expose observeSilentSms to all web content, we need to protect it from abuse somehow. It could be abused by web content entering a number that charges the user money repeatedly in the background without anyone knowing it. Maybe someone has another idea for protecting it? > >> 2. Payment providers need to know the user's network. Use cases: the >> provider may need to enable/disable certain regions (e.g. when in >> pre-production) and the provider needs to know which whitelisted short code >> to use for silent SMS. This is currently available as MCC/MNC on >> mozPaymentProvider. What is the danger of exposing this to all web content? >> Do we need to prompt the user like geolocation? > > Can't they just use the client's IP address to obtain that information? I've been told that IP address is not reliable enough to detect region and network. There seems to be proxying scenarios that create a lot of edge cases. Anyway, the fact that IP addresses are already exposed on the web makes me think that exposing MCC/MNC is not such a big deal. > >> 3. Since carrier billing is tied to SIMs the payment provider must know when >> a SIM is/isn't present, when a new SIM is inserted, and when a SIM is >> removed. Multiple SIMs should be supported too. Mozilla's payment provider >> persists carrier billing identity in a cookie (to avoid repeat >> authentication) so we need to know when to delete / recreate that cookie. >> Currently mozPaymentProvider exposes an array of ICCs that can be used for >> this so we'd want to expose this to all web content. A provider doesn't need >> to know the *exact* ICCs, it could use obfuscated values. Can we safely >> expose these data/events separately to web content? > > Wouldn't that raise fingerprinting concerns? I guess that depends on what > kind of obfuscation you had in mind though. The main use case here is detecting when one SIM is removed and another one inserted. That's all we need to solve for payments -- there are probably a couple different ways to do it safely without enabling fingerprinting. I also thought of window.addEventListener('moz-sim-changed', ...) or something. > >> That's it! These are the only primitives in mozPaymentProvider that we need >> to expose to web content if we want to deprecate mozPay(). >> >> >> Also, we've heard from partners that they want to access the Secure Element >> present on UICC SIMs. This primitive will enable them to set up carrier >> billing easier -- an API is in the works for NFC related needs. >> >> I mentioned that mozPay is roughly the equivalent of window.open() and >> postMessage. The way I envision apps doing payments is by including a >> JavaScript file in their app built by the payment provider. For example, an >> app would include a JS file to do Stripe payments (like they do already). If >> Stripe were to support carrier billing in addition to credit cards, it would >> benefit from access to the mozPaymentProvider data above. >> >> Exposing low level payment functionality to the app (or any web content) is >> a paradigm shift from mozPay. The *app* would be managing a new payment >> window instead of how mozPay's innards currently manage the new window. >> However, this is pretty standard practice on today's web (PayPal, Google >> Wallet, Stripe, etc, all work by injecting javascript into web pages). >> >> As a consequence of deprecating mozPay() Firefox Marketplace will need >> something like window.open(url, {mozTrusted: true}). This flag could be >> restricted to whitelisted domains; it would open the current trusted UI >> which is used by Firefox Marketplace and Persona. This would *not* be meant >> as a fix or evolution to the current trusted UI but as a way for Mozilla to >> transition out of mozPay(). Making the trusted UI more flexible is a >> separate ongoing discussion. > > Why is mozTrusted needed? When a developer calls navigator.mozPay(), the chrome layer opens a Trusted UI which is a special window that makes it more secure to enter sensitive payment details. You can see Gaia's interface for it here: https://github.com/mozilla-b2g/gaia/blob/master/apps/system/js/trusted_ui.js If we were to deprecate mozPay, web content would need a way to retain this functionality. The Trusted UI is not very well understood (yet) so the easiest way to retain this functionality would be to continue whitelisting Marketplace and Persona as the only domains who are allowed to open a Trusted UI. My idea was to let web content do window.open(url, {mozTrusted: true}) to open a Trusted UI which decouples it from mozPay. Only whitelisted domains would be allowed to do that; any other URLs would trigger an error. In the future, the Trusted UI might evolve into something that all web content can use if we can figure out how to trust content :) > >> On a separate but related note, Request Autocomplete >> (http://www.chromium.org/developers/using-requestautocomplete) would add >> additional benefit to users who make payments on mobile. For example, typing >> a credit card on mobile is painful. > > I never understood what the point of requestAutocomplete was. The point of it is to enable users to autocomplete forms that they are asked to fill out regularly. Imagine that you are using your mobile phone for the first time and you want to pay for something on a web app. The app might ask you to enter your credit card number, expiration, and CVV. This is cumbersome to type on a mobile device. Now, imagine that another unrelated app asks you to pay for something the next day. You have to enter you credit card number again! This would repeat infinitely for all unique payment providers on the web that you encounter. With request autocomplete, you would only need to enter your credit card number once -- you could auto-complete it the next time. Everyone on the web wins :) > It seems to me like Google is pushing this so that they can integrate Google > Wallet in Chrome's UI, but if that is not a requirement for us, then why > wouldn't we just let the UA provide the autocomplete service as it does today? In the context of Firefox OS, request autocomplete has nothing to do with Google Wallet. It would improve the user experience around payments and other cumbersome form entry. -Kumar > > Cheers, > Ehsan > _______________________________________________ dev-webapps mailing list [email protected] https://lists.mozilla.org/listinfo/dev-webapps
