Hi @serso. While the experimental Permissions API initially seemed promising for the purposes of opt-in provider access, key limitations made it less than ideal for this specific use case.
The current Permissions API doesn’t offer the ability to define custom permissions and was only intended to provide a better API to request native browser permissions like “geolocation” or “notification”. Requesting a non-standard permission - like “ethereum” - throws an Error. While dapp browsers could override the permissions.query method to explicitly handle a non-standard “ethereum” permission request, malicious sites could then initiate this non-standard request and know they’re in a dapp browser if no Error is thrown as expected. For example:
The following non-standard permission request will immediately throw:
navigator.permissions.query({ name: 'ethereum' });
// TypeError: The provided value ethereum is not a valid PermissionName.
If dapp browsers override permissions.query to handle “ethereum” requests, it will not immediately throw:
const originalQuery = navigator.permissions.query;
navigator.permissions.query = (query) => {
if (query.name === 'ethereum') {
// Handle provider request...
} else {
return originalQuery.apply(navigator.permissions, arguments);
}
};
navigator.permissions.query({ name: 'ethereum' });
// undefined
Because the Permissions API is meant only for predefined permissions and doesn’t (yet) allow for dynamically-defined permissions in a given context, any support at all for a non-standard “ethereum” permission would allow malicious websites to fingerprint and track Ethereum users. The Permissions API also displays a default browser confirmation dialog and doesn’t allow custom confirmation UIs; this limits the type of information that can be presented to the user, but this issue is less important.
Thanks for your comment, let me know if you have any other ideas around this. I agree that the Permissions API would be great to leverage if it was safely usable for non-standard permission types. We’ll continue to monitor it closely for EIP-1102 applicability.
