Consider disabling zcash: URI scheme

[daira]

This is @defuse's suggested mitigation for #1093 and #1094.

[LukasKorba]

Support for deplinks was impemented very long time ago, I think around mid 2022 because at that time it was a regular requirement but nobody defined actual and useful deeplinks. So the implementation is still in (nowadays) Zashi, doing:

• registering the URI
• parsing any URL that starts with zcash://

As a debug example sending some amount to a specific address URL was used but it's no longer valid because the infrastructure of (nowadays) Zashi changed.

We have 2 options:

1. Disable the whole feature, it would mean delete the URI support but I would leave at least the deeplink TCA dependency module in place for possible future re-open of the feature.
2. Make a use of deeplinks, define some useful URLs.

Please NOTE, I agree that definition of the URI automatically allows some other apps to discover Zashi but we can't do anything about it, it's how iOS designed.

Title of this issue says Consider disabling like it's a solution for Zashi 1.0 but it's only postponing the issue to some other day in the future. Only ultimate solution is to never use URI and deeplinks on iOS and that I can't decide, I don't know if product/leadership will ever make such call.

[daira]

Title of this issue says Consider disabling like it's a solution for Zashi 1.0 but it's only postponing the issue to some other day in the future. Only ultimate solution is to never use URI and deeplinks on iOS and that I can't decide, I don't know if product/leadership will ever make such call.

Yes it sucks. It would basically mean abandoning ZIP 321. But I want everyone to know that I am very serious about deprecating/removing features that can't in practice be made secure, even if we have expended a lot of work on them.

[pacu]

It would basically mean abandoning ZIP 321

Not actually. The Zashi app can choose not to tell the OS that it can handle the URI, but in fact handle it internally when scanning it from a QR or receiving a share item that contains a payment URI in the form of text. The UX wouldn't be "automagical" like Apple likes it but Zcash's mission is not to be super lean at any cost.

But I want everyone to know that I am very serious about deprecating/removing features that can't in practice be made secure, even if we have expended a lot of work on them.

I agree with this. It's the right thing to do