Reverse engineering a Windows Hello fingerprint reader

The problem

My laptop has a fingerprint reader that works perfectly in Windows Hello and not at all in Linux. There’s no driver, no libfprint support, and no documentation. I want to get the device working like a regular fingerprint reader for Linux, but I don’t know anything about hardware drivers or fingerprint readers.

The Plan™

Initial Approach

Find out how to access the hardware device on Linux
Write a script that can read and write raw data from/to the reader

This is where things get really hazy:

Switch to Windows, and somehow monitor the data stream between the OS and the sensor
- I’ll need to check if/how the data stream is encrypted.
Collect readings on the following actions:
- Fingerprint registration (successful)
- Fingerprint registration (unsuccessful)
- Fingerprint deregistration
- Fingerprint verification (successful)
- Fingerprint verification (unsuccessful)
Try to find any documentation on the chipset used in the fingerprint reader (pinout, etc)
Find the driver and attempt to extract any information from it
Build a basic schema of the protocol
Check if there’s a boot-up handshake / authentication sequence between the OS and the reader, and document it
Switch back to Linux, and attempt to replicate the handshake (if relevant)
Use the low-level read/write script to communicate with the reader using its protocol
Write a driver for the device so it appears to Linux as a USB fingerprint reader.

In case it isn’t clear from the hand-wavyness of The Plan™, I have no idea what I’m doing, and I’ve never attempted anything like this before. However, I think this would be a great exercise in reverse engineering, it would be really nice to have my fingerprint reader working, and it would be a nice opensource contribution to the Linux community.

Reference Material

TouchID support for Omarchy on Macbooks