I talked about the need for PS/2 keyboard against the setting of malicious USB devices. Are USB Keyboards actually ruining the isolation-based security?
I think there may be a good way to ensure the secure login from USB keyboards, although I don’t know if Qubes OS already has this mechanism. Here is the step:
- Insert a FIDO2 or any physical key to the PC and touch it (in this phase only physical keys can be recognized)
- When prompted by the login screen, insert the USB keyboard to type the physical key’s PIN (lets make, say, a very simple program with minimum attack surface, that can only recognize PIN / keyboard input)
- If succeeded, continue the normal login procedure (i.e. account and password)
By doing so, I think we can minimize the USB threat. Anyway, it is worth considering, given we cannot use something like registering a unique identifier of a hardware device to the Qubes OS in advance.