Jorijn van der Graaf
ac0a147e95
Phosh's lock screen cannot take a fingerprint: its PAM conversation answers every prompt with the password. So the daemon follows the seat session that is locked and in front (logind LockedHint + Active), runs a verify of its own while the display is on (backlight bl_power), and answers a match with logind's Session.Unlock. Only fingers named in that session owner's map unlock. The map is re-read at every arm and verdict, and a delete cancels a running standby verify, so a finger deleted while locked stops counting at once. A verdict from an earlier lock or another session is dropped. no-unlock rules and FingerMatched apply as for a client match. A client Claim cancels standby, and its Release, or a claim that fails while pending, re-arms it. --standby-unlock=off disables it. Tested on the dev phone before the review fixes (map re-read, front-session tracking, cancel ordering, pending-claim re-arm): under Phosh, six unlocks by two fingers and an unnamed template refused; under Plasma, kscreenlocker's pam_fprintd unlocks while standby yields and re-arms. With the fixes: suites 8/8, and a daemon restart under a lock screen picks the locked session up. Not exercised: standby's own Session.Unlock on kscreenlocker, user switching.
71 lines
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3 KiB
Markdown
71 lines
No EOL
3 KiB
Markdown
# fingerprintd
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Fingerprint daemon for the Fairphone 6 (`milos`, SM7635) on mainline Linux.
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`fingerprintd-core` is a static library with no GLib, no libqcomtee and no
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system headers. Everything in it is a wire format or a state machine that was
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recovered by reverse-engineering, so all of it is pinned by tests that run on a
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dev box with no phone, no TEE and no sensor. The daemon shell holds everything
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that touches hardware.
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## Build
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```sh
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crafter-build # bin/fingerprintd-<target>-<march>/fingerprintd
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crafter-build test # the unit suites
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```
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Cross-compiling for the phone:
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```sh
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packaging/make-sysroot.sh
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crafter-build -- --target=aarch64-alpine-linux-musl --sysroot=~/.cache/fingerprintd/sysroot-aarch64-alpine --march=armv8.6-a+fp16fml+aes+sha3+sm4 --mtune=cortex-a720
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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
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```
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Verified on the device: all five suites pass cross-built and run on the phone
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itself, not only under emulation.
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```
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fprintd-enroll -f right-index-finger user ten stages, enroll-completed
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fprintd-list user - #0: right-index-finger
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fprintd-verify user (wrong finger) verify-no-match, on the first press
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fprintd-verify user (enrolled finger) verify-match, on the first press
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```
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## Lock-screen unlock
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Two routes, both on by default:
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- **PAM.** The daemon provides `fprintd`, so a lock screen that runs
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`pam_fprintd` beside its password prompt unlocks by finger the usual way.
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Plasma's does (`kde-fingerprint`; the `fingerprint-auth` and `postlogin`
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services it needs are shipped here). Phosh's cannot: its PAM conversation
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answers every prompt with the password, so a fingerprint module in its stack
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would only stall the password behind the fingerprint timeout.
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- **Standby.** While the session in front on its seat is locked and the
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display is on, the daemon runs a verify of its own and answers a match with
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logind's `Session.Unlock`, which Phosh honours. No verify runs while the
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display is off (an open verify polls the sensor at ~5 Hz; the display state
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comes from the backlight's `bl_power` or the panel's DRM `dpms`, and a
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device with neither is treated as always on). Any fprintd client takes
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precedence: a `Claim` cancels the standby verify, a `Release` re-arms it.
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Only fingers named in that session owner's map unlock, and the map is
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re-read at every arm, so a finger deleted while locked stops counting at
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once. Per-finger `no-unlock` rules apply here too, and every match is
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announced as `FingerMatched` for the session agent. `--standby-unlock=off`
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disables it.
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## Runtime dependencies
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The `focal64` trustlet is proprietary and is not in this repo. It is
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extracted from the device's own stock Android partition on first boot by the
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`fp6-vendor-blobs` mechanism, the same way other firmware in fp6-img is.
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## License
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GPL-3.0-only, see LICENSE.
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## Copyright
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Copyright (C) 2026 Catcrafts® catcrafts.net |