fingerprintd/interfaces/Fingerprintd.cppm

// SPDX-License-Identifier: GPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

/*
fingerprintd — fingerprint daemon for the Fairphone 6 on mainline Linux.

The sensor is a FocalTech FT9391 on a TrustZone-owned SPI bus: the normal world
cannot reach it, and raw frames never leave the TEE. All capture, enrolment and
matching happen inside the focal64 trustlet. This daemon owns the sensor rail,
holds the QTEE session open, serves the storage callbacks QTEE makes back into
the normal world, and reports the matched finger id.
*/

export module Fingerprintd;
export import :Sfs;
Initial commit: the gpfile wire format, pinned by two real containers fingerprintd will own the FP6's fingerprint sensor: the rail, the QTEE session, the storage callbacks QTEE makes back into the normal world, and net.reactivated.Fprint so pam_fprintd and the desktop need no changes. None of that runs yet. What is here is the first core module and the machinery around it. Fingerprintd:Sfs is the gpfile listener's frame -- the callback that carries 47 of 66 storage requests during an enrolment. It is parse, reply and root mapping only: no file I/O, no TEE, no allocation of the shared buffer. The daemon shell supplies those, which is what lets every byte-level decision be tested on a dev box with no phone. The module exists mainly to hold one fact. READ answers at req+0x00c and WRITE reads its payload from req+0x110, because the frame is a union: a WRITE still needs its path while the payload is copied out, so it sits past the 256-byte path field, while a READ has consumed the path and packs its reply over it. Conflating them is wrong in both directions with the same symptom -- the container does not round-trip, QTEE's HMAC check fails, and the file is unlinked as tampered on the next session. So the tests do not assert the constants against themselves. They load two real containers off the phone -- one written correctly, one written with the offsets conflated -- and re-derive the bug: the broken one opens with ASCII path text rather than a binary HMAC, that text is the group name from character 8 because the read offset is 8 bytes into the path field, and the real container sits exactly 0x104 further in. Then a write-store-read round trip must be the identity, and the same round trip through a single offset must not be. O_TRUNC gets a static_assert of its own. QTEE writes a container as write(0,4096), write(4096,N), write(0,4096), so truncating on open leaves 4096 bytes where a 258850-byte template belongs; it unlinks a file it means to shorten rather than relying on the opener. Verified by mutation: conflating the offsets, making DataOffset return the read offset for writes, and setting O_TRUNC each fail the suite. 2026-09-02 16:02:46 +02:00			`// SPDX-License-Identifier: GPL-3.0-only`
			`// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®`

			`/*`
			`fingerprintd — fingerprint daemon for the Fairphone 6 on mainline Linux.`

			`The sensor is a FocalTech FT9391 on a TrustZone-owned SPI bus: the normal world`
			`cannot reach it, and raw frames never leave the TEE. All capture, enrolment and`
			`matching happen inside the focal64 trustlet. This daemon owns the sensor rail,`
			`holds the QTEE session open, serves the storage callbacks QTEE makes back into`
			`the normal world, and reports the matched finger id.`
			`*/`

			`export module Fingerprintd;`
			`export import :Sfs;`