fingerprintd/README.md
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# 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.
```
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