# 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
crafter-build -- --target=aarch64-alpine-linux-musl --sysroot=~/.cache/fingerprintd/sysroot-aarch64-alpine --march=armv8.6-a+fp16fml+aes+sha3+sm4 --mtune=cortex-a720
crafter-build test --target=aarch64-alpine-linux-musl --sysroot=~/.cache/fingerprintd/sysroot-aarch64-alpine --march=armv8.6-a+fp16fml+aes+sha3+sm4 --mtune=cortex-a720
```

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
```

## Lock-screen unlock

Two routes, both on by default:

- **PAM.** The daemon provides `fprintd`, so a lock screen that runs
  `pam_fprintd` beside its password prompt unlocks by finger the usual way.
  Plasma's does (`kde-fingerprint`; the `fingerprint-auth` and `postlogin`
  services it needs are shipped here). Phosh's cannot: its PAM conversation
  answers every prompt with the password, so a fingerprint module in its stack
  would only stall the password behind the fingerprint timeout.
- **Standby.** While the session in front on its seat is locked and the
  display is on, the daemon runs a verify of its own and answers a match with
  logind's `Session.Unlock`, which Phosh honours. No verify runs while the
  display is off (an open verify polls the sensor at ~5 Hz; the display state
  comes from the backlight's `bl_power` or the panel's DRM `dpms`, and a
  device with neither is treated as always on). Any fprintd client takes
  precedence: a `Claim` cancels the standby verify, a `Release` re-arms it.
  Only fingers named in that session owner's map unlock, and the map is
  re-read at every arm, so a finger deleted while locked stops counting at
  once. Per-finger `no-unlock` rules apply here too, and every match is
  announced as `FingerMatched` for the session agent. `--standby-unlock=off`
  disables it.

## Runtime dependencies

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 other firmware in fp6-img is.

## License

GPL-3.0-only, see LICENSE.

## Copyright

Copyright (C) 2026 Catcrafts® catcrafts.net