# fingerprintd

Fingerprint daemon for the Fairphone 6 (`milos`, SM7635) on mainline Linux.

`fingerprintd-core` is a static library with no GLib, no libqcomtee and no
system headers. Everything in it is a wire format or a state machine that was
recovered by reverse-engineering, so all of it is pinned by tests that run on a
dev box with no phone, no TEE and no sensor. The daemon shell holds everything
that touches hardware.

## Build

```sh
crafter-build              # bin/fingerprintd-<target>-<march>/fingerprintd
crafter-build test         # the unit suites
```

Cross-compiling for the phone:

```sh
packaging/make-sysroot.sh                        # once; no root, no qemu, no device
crafter-build -- --target=aarch64-alpine-linux-musl \
  --sysroot=~/.cache/fingerprintd/sysroot-aarch64-alpine \
  --march=armv8-a --mtune=generic
crafter-build test --target=aarch64-alpine-linux-musl --sysroot=... \
  --march=armv8-a --mtune=generic                # runs the suites under qemu-aarch64
```

The result links dynamically against the phone's own musl and libc++
(`libc++`, `libc++abi`, `libunwind`, `libgcc_s`, all already present on pmOS).
The research harness this replaces had to be built `-static`, but only because
it was built with the host's glibc toolchain — that constraint does not apply
to a real Alpine sysroot.

Verified on the device: all five suites pass cross-built and run on the phone
itself, not only under emulation.

```
fprintd-enroll -f right-index-finger user   ten stages, enroll-completed
fprintd-list user                            - #0: right-index-finger
fprintd-verify user   (wrong finger)         verify-no-match, on the first press
fprintd-verify user   (enrolled finger)      verify-match,    on the first press
```

## Runtime dependencies, not carried here

The `focal64` trustlet is proprietary and is not in this repo. It is
extracted from the device's own stock Android partition on first boot by the
`fp6-vendor-blobs` mechanism, the same way the audio firmware is.

## License

GPL-3.0-only, see LICENSE.

## Copyright

Copyright (C) 2026 Catcrafts® catcrafts.net