fingerprintd/packaging
Repository files (latest commit first)
Filename Latest commit message Latest commit date
Jorijn van der Graaf b228287c5b A verify nobody answered is not a failure, and the trustlet is not ours to ship
Two things the packaging left behind.

A verify that ran its 600-frame budget without the sensor being touched was
reported to the client as verify-unknown-error. Nothing had gone wrong: nobody
had pressed. It cost three verifications during packaging, each reading as a
broken daemon. fprintd's contract is that a verify runs until the client stops
it, so the frame cap bounds one trustlet scan session rather than the user's
patience, and a window with no press simply runs again. Verified across the
rollover: 600 frames untouched, "still waiting", then a press matching on its
first contact frame in 44 ms.

Presses that happen and never reach a verdict now report verify-retry-scan --
a bad scan, which fprintd has a word for, and not the matcher saying no.

The cost is that an unanswered verify polls every ~200 ms for as long as the
client holds it. The cure is measured and available -- gpio75 is silent at
idle and bursts on contact -- but it would make the IRQ the only way a press
is ever noticed, deleting the poll under every rate this daemon has been
measured at. Noted where the loop waits, not done.

And the trustlet: focal64.mbn is a proprietary OEM-signed blob, so the package
ships a fp6-vendor-blobs manifest fragment instead, the same mechanism
soc-fairphone-fp6-audio uses for the amp config. It needed a new directive
there -- a QTEE image is an ELF header file plus one payload per program
header, not one file -- and reassembly on the phone reproduces the image QTEE
has accepted since August, byte for byte.
2026-09-05 04:01:06 +02:00
..
20-focal64.manifest A verify nobody answered is not a failure, and the trustlet is not ours to ship 2026-09-05 04:01:06 +02:00
80-fingerprintd.preset Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00
APKBUILD A verify nobody answered is not a failure, and the trustlet is not ours to ship 2026-09-05 04:01:06 +02:00
build-package.sh Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00
deploy-dev.sh Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00
fingerprintd.json Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00
fingerprintd.modules-load.conf Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00
fingerprintd.service A verify nobody answered is not a failure, and the trustlet is not ours to ship 2026-09-05 04:01:06 +02:00
fingerprintd.tmpfiles.conf Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00
fpenrol.sh fpenrol.sh: no enrolment ever received the position guidance this script claims 2026-09-03 17:44:35 +02:00
fplearn.sh fplearn.sh: a wipe leaves learning off too 2026-09-05 02:07:26 +02:00
fptrial.sh Hold, do not tap -- and stop spending the verdict on a frame that cannot carry it 2026-09-05 00:17:13 +02:00
make-bin-tarball.sh A verify nobody answered is not a failure, and the trustlet is not ours to ship 2026-09-05 04:01:06 +02:00
make-libqcomtee.sh Reach QTEE: credentials, client env and the app loader, with no QCBOR 2026-09-02 18:02:28 +02:00
make-sysroot.sh Add the cross-build sysroot recipe, verified on the device 2026-09-02 17:34:27 +02:00
mnt-persist.mount Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00
net.reactivated.Fprint.conf Become a daemon: a held session, a worker, and net.reactivated.Fprint 2026-09-02 22:10:51 +02:00
net.reactivated.fprint.device.policy Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00
net.reactivated.Fprint.service Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00
README.config.md Package the daemon, so a fingerprint survives a reflash 2026-09-05 02:52:01 +02:00

fingerprintd.json — where it comes from, and why this exact file

The trustlet gates its config file on common.configuration_uuid and silently falls back to built-in defaults on a mismatch, so the file is not decorative: SYNC_CONFIG returning 0 is what makes the whole init chain run.

This copy is generated, not hand-written. Its source is fp6fpcfg.py in the fp6 bring-up repo, which builds it from the captured stock configuration dump (journal/fingerprint/captures/2026-08-25-focal64-effective-config-from-stock.txt):

utilities/fp6fpcfg.py --daemon --verbose > packaging/fingerprintd.json

sha256 begins b205c756914a66f1.

Why the --verbose variant

--verbose here is the trustlet's own log level, not the daemon's. It is shipped because it is the file every accuracy number was measured on — 30/30 held presses, zero false accepts, 36-330 ms to a verdict — and the TA's log level cannot be raised again by a runtime SYNC_CONFIG, so a session that needs the matcher's own lines has to have started with it.

--daemon alone produces the same file with trustlet logging off (sha256 6c4503e628406424, four diagnosis.* keys differ and nothing else). It is plausibly the better shipping default and it is untested: no rate in the journal was measured on it. Switching is a measurement, not an edit.

The two policy keys

  • common.max_authentication_rescan_times: 0 — at the stock budget a wrong finger never yields a terminal frame, so a PAM client waits forever for the verify-no-match it needs.
  • trustlet.enable_trusted_enrollment: false — skips the challenge compare and the hw_auth_token HMAC verify. pmOS has no Gatekeeper to issue a token and nothing on pmOS verifies one.