accounts/usbwallet: fails to list Trezors

[jtolio]

System information

OS & Version: Linux and macOS
Commit hash : c8be0f9

Expected behaviour

I expect the following code to print out wallets when my Trezor is attached (and working with Trezor Suite):

	hub, err := usbwallet.NewTrezorHubWithWebUSB()
	if err != nil {
		panic(err)
	}
	for _, wallet := range hub.Wallets() {
		fmt.Println(wallet)
	}

Actual behaviour

No USB wallets found.

Steps to reproduce the behaviour

I have spent a bunch of time trying to understand what's happening. As far as I can tell, on both macOS and Linux, when I connect my Trezor (I have tried both a Trezor Model One with the latest firmware and a Trezor Model T with the latest firmware), github.com/karalabe/hid does find a USB entry for the Trezor, but it is for Interface 1, not Interface 0. No matter what I do, on Linux and macOS, only the FIDO/U2F interface shows up. However, the Trezor Suite still works, of course.

So it might be a change to recent Trezor firmware builds? It doesn't appear to be OS specific (Linux and Mac both have this problem). It doesn't appear to be Trezor specific (two different models of Trezor have this problem). So I think we need to rework how Trezors talk to the usbwallet library? Perhaps they need to be initialized or something?

[jtolio]

Trezor Model T won't let me downgrade back past 2.8.7, and Trezor Model T 2.8.7 has this problem.

[prusnak]

go-ethereum's USB library, github.com/karalabe/hid, does find a USB entry for the Trezor, but it is for USB Interface 1, not Interface 0.

This is expected. Interface 0 is a WebUSB interface, not HID interface (which is only used for FIDO).

However, this does not explain why usbwallet.NewTrezorHubWithWebUSB() does not work (hopefully that uses WebUSB correctly).

[jtolio]

You're saying it's expected that github.com/karalabe/hid only returns USB interface 1?

This part of the usbwallet library hasn't changed in 6 years (https://github.com/ethereum/go-ethereum/blame/master/accounts/usbwallet/hub.go#L95-L104), definitely worked in that time range, and is explicitly looking for interface 0.

So this is a hint that it used to return USB interface 0 and maybe what changed is that?

(Hmm, github.com/karalabe/hid hasn't appreciably changed in over a year either)

[prusnak]

You're saying it's expected that github.com/karalabe/hid only returns USB interface 1?

Yes. Interface 0 is WebUSB not HID.

Ignore NewTrezorHubWithHID - this is for very ancient versions of Trezor One devices. The code should have been removed imo.

Pay attention only to NewTrezorHubWithWebUSB‎.