Signing with Trezor is broken

[dennisreimann]

Describe the bug

Importing a Trezor wallet using the Vault works, but signing a transaction does not.

Your BTCPay Environment (please complete the following information):

• BTCPay Server Version: 1.2.1

• BTCPay Server Vault app version: 2.0.1

• Deployment Method: Dev Env

Your local environment (please complete the following information):

• Your operating system: macOS
• Browser: Firefox

Your hardware wallet details (please complete the following information):

• Hardware wallet name: Trezor
• Hardware wallet version: Trezor Bridge 2.0.27
• Hardware wallet firmware, bootloader, microcontroller verisons (where applicable): 1.9.3 and 1.10.2 (latest)

Additional context

Original bug report by @pavlenex, maybe he can provide additional information. I confirmed the issue.

Screenshots / Video / GIf (if applicable)

1.9.3 Firmware

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1.10.2 Firmware

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[pavlenex]

cc @NicolasDorier

[NicolasDorier]

checking

[NicolasDorier]

the new release of hwi doesn't see to solve any trezor related stuff... that's weird.

[mikeyyyv]

I'm having the exact same issue here. Thank you.

[NicolasDorier]

@mikeyyyv trying to find out what happened.

[NicolasDorier]

Does the Trezor T has this issue? Sadly I don't have a trezor 1...
Also @mikeyyyv have you tried, in the send wallet, go to advanced and check

[pavlenex]

Yes issue reported on Trezor T as well @NicolasDorier.

[NicolasDorier]

I lost the cable, so I need to order a new one. Will take a bit of time to look at it

[gruve-p]

@pavlenex @mikeyyyv @dennisreimann
On Trezor devices its mandatory to include non witness UTXO otherwise signing will always fail:
On the send wallet go to advanced settings and check Always include non-witness UTXO if available

[dennisreimann]

@gruve-p @NicolasDorier Yes, I can confirm that setting the "Always include non-witness UTXO" fixes the problem.

Can we circumvent this issue by detecting if it is a hardware wallet that needs this setting and include it later on, instead of relying on the user to know about it and dig it up from the "Advanced settings"?

Upload.from.GitHub.for.iOS.MOV

[gruve-p]

Maybe best way is if a Trezor device is detected that the checkbox is automatically checked? Or maybe save user preferences when sending so user does not need to check it again ( and write a big text that if you are a Trezor user that you need to check that box the first time)

P.S. This issue was reported to Nicolas on 12 April 2021 (via Mattermost) while porting BTCPayServer.Vault to GRSPayServer.Vault

[dennisreimann]

The PSBT one is about to sign gets created before we even know which wallet will be used for signing. I think we need to tackle this differently -- maybe by specifying preconditions which need to be met and which we can check once the wallet is defined. This way we could deliberately point out to the user what needs to be done or which kind of information is missing.

[NicolasDorier]

@dennisreimann while we can't automatically add the previous transactions once we clicked through, I think we can still pass this information to be available in the signing screen and show error message. Bit pain in the ass though.

[piliugin-anton]

Did you tried to report the problem to Trezor team?

[NicolasDorier]

@piliugin-anton they probably know already about it, but won't fix it. Ask them why their wallet requires the previous tx and not only non_witness_utxo.

[gruve-p]

cc @prusnak @matejcik

[prusnak]

Ask them why their wallet requires the previous tx and not only non_witness_utxo.

We need previous TX to mitigate the design flaw of Bitcoin which makes it possible to steal user funds via really high transaction fee.

Good news is that the issue will be fixed with Taproot. When all inputs are Taproot then it is not required to provide previous TX to Trezor device because Taproot fixes this design flaw.