Virtual Fingerprint HAL

This is a virtual HAL implementation that is backed by system properties instead of actual hardware. It's intended for testing and UI development on debuggable builds to allow devices to masquerade as alternative device types and for emulators.

Supported Devices

This HAL can be used on emulators, like cuttlefish, or on real devices. Add the following to your device's .mk file to include it:

PRODUCT_PACKAGES_DEBUG += android.hardware.biometrics.fingerprint-service.example

The virtual HAL will be ignored if a real HAL is also installed on the target device. Set the biometric_virtual_enabled settings and reboot the device to switch to the virtual HAL. Unset it and reboot again to switch back.

Getting Started

First, set the type of sensor the device should use, enable the virtual extensions in the framework, and reboot.

$ adb root
$ adb shell settings put secure biometric_virtual_enabled 1
$ adb shell setprop persist.vendor.fingerprint.virtual.type rear
$ adb reboot

Enrollments

Next, setup enrollments on the device. This can either be done through the UI, or via adb directly.

Direct Enrollment

To set enrollment directly without the UI:

$ adb root
$ adb shell locksettings set-pin 0000
$ adb shell setprop persist.vendor.fingerprint.virtual.enrollments 1
$ adb shell cmd fingerprint sync

UI Enrollment

Set pin
```
$ adb shell locksettings set-pin 0000
```

Tee up the results of the enrollment before starting the process:

$ adb shell setprop vendor.fingerprint.virtual.next_enrollment 1:100,100,100:true

Navigate to Settings -> Security -> Fingerprint Unlock and follow the prompts.

Verify the enrollments in the UI:

$ adb shell getprop persist.vendor.fingerprint.virtual.enrollments

Authenticate

To authenticate successfully set the enrolled id that should succeed. Unset it or change the value to make authenticate operations fail:

$ adb shell setprop vendor.fingerprint.virtual.enrollment_hit 1

Acquired Info Insertion

Fingerprint image acquisition states at HAL are reported to framework via onAcquired() callback. The valid acquired state info for AIDL HAL include

{UNKNOWN(0), GOOD(1), PARTIAL(2), INSUFFICIENT(3), SENSOR_DIRTY(4), TOO_SLOW(5), TOO_FAST(6), VENDOR(7), START(8), TOO_DARK(9), TOO_BRIGHT(10), IMMOBILE(11), RETRYING_CAPTURE(12)}

Refer to AcquiredInfo.aidl for details

The states can be specified in sequence for the HAL operations involving fingerprint image captures, namely authenticate, enrollment and detectInteraction

$ adb shell setprop vendor.fingerprint.virtual.operation_authenticate_acquired 6,9,1
$ adb shell setprop vendor.fingerprint.virtual.operation_detect_interaction_acquired 6,1
$ adb shell setprop vendor.fingerprint.virtual.next_enrollment 2:1000-[5,1],500:true

#next_enrollment format example:
.---------------------- enrollment id (2)
|   .------------------ the image capture 1 duration (1000ms)
|   |   .--------------   acquired info first (TOO_SLOW)
|   |   | .------------   acquired info second (GOOD)
|   |   | |   .-------- the image capture 2 duration (500ms)
|   |   | |   |   .---- enrollment end status (success)
|   |   | |   |   |
|   |   | |   |   |
|   |   | |   |   |
2:1000-[5,1],500:true

For vendor specific acquired info, acquiredInfo = 1000 + vendorAcquiredInfo

Error Insertion

The valid error codes for AIDL HAL include

{UNKNOWN(0), HW_UNAVAILABLE(1), UNABLE_TO_PROCESS(2), TIMEOUT(3), NO_SPACE(4), CANCELED(5), UNABLE_TO_REMOVE(6), VENDOR(7), BAD_CALIBRATION(8)}

Refer to Error.aidl for details

There are many HAL operations which can result in errors, refer to here file for details.

$ adb shell setprop vendor.fingerprint.virtual.operation_authenticate_error 8

For vendor specific error, errorCode = 1000 + vendorErrorCode

View HAL State

To view all the properties of the HAL (see fingerprint.sysprop file for the API):

$ adb shell getprop | grep vendor.fingerprint.virtual