DISCLAIMER: Don't take it seriously, super low quality code that not even necessarily correct. To show some hints for the one who's curious, I left it here.
This tool decodes the QR code generated by browsers when login with Passkeys. But it won't decode the QR code itself, you need another one, such as this.
This new specification will likely to be called "CTAP 2.2", and will be published as a draft soon. The wait is over: Client to Authenticator Protocol (CTAP)
Review Draft, March 21, 2023.
While I've added the basic ability to connect to the tunnel servers, it never really worked with Apple's. And I've found the reason in the draft:
The protocol between the authenticator and the tunnel service, and details about how the service later contacts the authenticator, are a private detail of the authenticator's implementation.
For convenience I built 2 binaries.
$ hs-qr-cable-exe
Usage: hs-qr-cable-exe FIDO:/00112233445566778899...
$ hs-qr-cable-exe FIDO:/aaaa
# caBLEv2 Initiator FIDO:/ URL Decoder
## Input
"FIDO:/aaaa"
## CBOR data
### CBOR bytes (hex)
Error decoding URL: contains non-digit characters