Passkeys AutoFill Provider

The answer is that it's mostly up to you! Your passkey provider can implement passkey creation and management however you want, as long as you give us back a valid passkey WebAuthn response at the end. For details about how the individual fields need to be formatted, the best documentation is the WebAuthn spec itself.

Thank you for the quick response, @garrett-davidson.

Below is a piece of code that we are trying to use, along with comments to clarify the situation. Your comments will be greatly appreciated.

// Example: We visit https://example.com and press the register button, which internally triggers `navigator.credentials.create()`.
override func prepareInterface(forPasskeyRegistration registrationRequest: ASCredentialRequest) {
    self.request = registrationRequest as! ASPasskeyCredentialRequest
    
    let response = ASPasskeyRegistrationCredential(
        // What string should be used here? example.com or https://example.com?
        // Is this the correct documentation? Refer to: https://www.w3.org/TR/webauthn-2/#relying-party-identifier
        relyingParty: self.request.credentialIdentity.serviceIdentifier.identifier,
        
        // Is this the correct documentation for `clientDataHash`? See: https://www.w3.org/TR/webauthn-2/#collectedclientdata-hash-of-the-serialized-client-data
        clientDataHash: self.request.clientDataHash,
        
        // Is this the correct documentation? Check: https://www.w3.org/TR/webauthn-2/#credential-id
        credentialID: Data(UUID().uuidString.utf8),
        
        // Is this the correct documentation? See: https://www.w3.org/TR/webauthn-2/#sctn-generating-an-attestation-object
        // Should the attestationObject be a CBOR map in bytes?
        attestationObject: Data()
    )
    
    self.extensionContext.completeRegistrationRequest(using: response)
}

After a few days of research, we finally found out why it didn't work.

The problem lies here: https://www.w3.org/TR/webauthn-3/#flags According to the official documentation, Bits 3-5 are reserved for future use (RFU2), and they MUST remain as zeros. However, in this source https://developer.mozilla.org/en-US/docs/Web/API/Web_Authentication_API/Authenticator_data,) those bits are used. It seems that on iOS, if those bits are zeros, you always get an error. This aspect is not mentioned anywhere.