Support the web-wallet-selector for DC API polyfill

[leifj]

Problem Statement

We need to support the DC API somehow. It has been suggested that one (possibly the only) approach for web wallets is to polyfill the DC API to support web wallets using a browser plugin. Over at https://github.com/sirosfoundation/web-wallet-selector is an early attempt to do precisely that.

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Proposed Solution (Optional)

Implement support for the wallet registration call provided by the public API of the web-wallet-selector plugin https://github.com/sirosfoundation/web-wallet-selector

The suggested approach is to call the wallet registration API silently from the login page when a user visits the wallet and has the plugin installed. At some later stage we can decide to suggest the user install the plugin if it isn't already installed.

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Additional Information (Optional)

• Right now the plugin requires manual installation. As soon as we can do some testing we plan to publish on the broswer extension "stores"

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[leifj]

There are two open issues:

1. How does a web wallet instance make itself known to the web-wallet-selector. For an initial release this is relatively easy. The registration API in https://github.com/sirosfoundation/web-wallet-selector/blob/main/API_REFERENCE.md has a registration API that should work as a first version.
2. How does the web wallet handle the request and response. The current version of the web-wallet-selector has a very rough API for this.

Possibly the answer to (2) is for the web wallet to register a pair of callbacks - one for request and one for response handling. Right now the web-wallet-selector "knows" about protocols such as openid4vp but doesn't know about how the response from those protocols are passed back into the DC API spi.

[patatoid]

I gave a try to add the web-wallet-selector registration at wwWallet startup, it works pretty well, the extension registering the instance on wallet startup (sirosfoundation#1) Maybe we should better add an installation link?

The wallet registered, I am not sure how DC API handle this, having tested on chrome with no success. The browser native feature which should be triggered in my understanding while handling openid4vp:// requests. It may be enabled switching chrome://flags/#web-identity-digital-credentials. Maybe others will have better chance?

It is possible for the extension to have a hook to open the browser wallet if selected. This time I tried on Firefox and succeed to hook web+openid4vp:// calls to be redirected to an hardcoded wallet URL. I am not sure if it is the way to go but gives a functional flow to handle openid4vp requests.

[leifj]

so what would be a good way to pass the request over to the webwallet? Should the web wallet really just register two callbacks per "protocolID": one for passing the request to the webwallet and one for passing the response back to the plugin? Would that work?

[patatoid]

Not sure, I think we should have a deeper look at the ARF, there is a mention about DC API in there.

[leifj]

No I really don't think the ARF helps here at all. This is a pretty simple question: what is the preferred way to send an openid4vp request into a wwWallet instance. Should the wallet register a javascript function with "its own" implementation of openid4vp or should the plugin bundle its own implementation.

[leifj]

The current version is doing almost the right thing... but we need to add response types, hence the link to #935