Jorijn van der Graaf
928fe1482e
The trustlet has always reported WHICH finger matched and the daemon only ever used it to answer yes. A table in /etc/fingerprintd/actions.conf now gives each finger a meaning: run a command as root, tell the user's session, or report no-match while doing one of those anyway -- which is duress, where the phone should look like it simply did not recognise the finger. Two rules shaped the design. Root does not launch applications. The daemon has no session bus, no display and no user environment, so a `session` rule carries no command at all: the daemon emits net.catcrafts.Fingerprintd1.FingerMatched(finger, uid) and an agent in the user's own session decides what that means from the user's own configuration. The only commands in the file are ones root is meant to run. Which makes the file a root shell, and the parser treats it as one. It is refused outright unless root owns it and nobody else can write it, group included. A malformed line rejects the WHOLE file rather than being skipped: applying the prefix would leave a policy nobody wrote, and the missing half could be the one that mattered. That property is tested, and the test caught it being false the first time -- rules accumulated before the bad line survived the rejection. A system command must be an absolute path, because resolving a bare name through PATH makes what root runs depend on an environment this daemon does not control. It is double-forked with a scrubbed environment so an action may outlive the daemon (a reboot) without ever stalling the worker thread that is the only thread allowed to touch the trustlet. Ordering is deliberate: the verdict override happens before the client is told, because that is the point of duress; the session signal and the root command happen after, on the same principle that keeps the harvest and the save off the unlock path. No actions.conf ships. An example goes to /usr/share/doc, because shipping a root shell nobody asked for is not a default. Not yet exercised on hardware.
22 lines
754 B
C++
22 lines
754 B
C++
// SPDX-License-Identifier: GPL-3.0-only
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// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®
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/*
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fingerprintd — fingerprint daemon for the Fairphone 6 on mainline Linux.
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The sensor is a FocalTech FT9391 on a TrustZone-owned SPI bus: the normal world
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cannot reach it, and raw frames never leave the TEE. All capture, enrolment and
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matching happen inside the focal64 trustlet. This daemon owns the sensor rail,
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holds the QTEE session open, serves the storage callbacks QTEE makes back into
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the normal world, and reports the matched finger id.
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*/
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export module Fingerprintd;
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export import :Sfs;
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export import :Rpmb;
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export import :Ta;
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export import :Engine;
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export import :Store;
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export import :Tee;
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export import :Sensor;
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export import :Actions;
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