Jorijn van der Graaf
ffad29ba4e
Fingerprintd:Ta is the second core module: request payloads, response fields,
the error table, and the rule that decides what a frame meant. Payload building
and response reading only -- no TEE, no transport.
Very little of this is guessable, so each constant carries where it came from.
Three were found only because QTEE recorded a fault naming the instruction that
read them:
* the event context's scan-slot count at +712, which do_enroll branches on to
skip the entire slot loop -- an all-zero payload logged "groups->,
results->" and read exactly like a gate failing deep in the trustlet, when
it was zero iterations;
* CAPTURE_IMAGE's flags at payload+0x18, without which preprocessing, the
classifier and the enrol grouper never run at all, whatever is on the
sensor;
* SYNC_STATISTICS, whose absence leaves g_statistics NULL so the first enrol
frame that gets far enough takes a data abort and every later command
answers -90.
The verdict rule gets the most attention because it was mislabelled three times
before the comparison producing it was read. A frame is one of three things and
only the third is a verdict: the poison intact means the matcher never ran,
rc=-11 means not identified yet with attempts remaining, and only rc=0 carries
a match or a rejection. The poison exists because a zero-initialised buffer
cannot tell a released finger from a rejected one.
The tests are in two halves that cannot prop each other up. Explicit wire
conditions pin the classifier; three recorded runs pin the counting policy,
which is what actually went wrong. In the stock-budget run 31 of 48 frames
answered "not identified yet" and every frame that carried an image matched --
counting those 31 as attempts turns 8-for-8 into 8-of-39 and reads as a flaky
sensor. The wrong-finger control pins zero false accepts.
Fixtures are verdict-line excerpts, not the 40 KB transcripts, which are thick
with the device's SFS container names the test has no use for.
Verified by mutation: classifying -11 as a rejection, dropping SYNC_STATISTICS
from the init chain, and forgetting the +0x10 response payload offset each fail
the suite.
54 lines
1.9 KiB
C++
54 lines
1.9 KiB
C++
// SPDX-License-Identifier: GPL-3.0-only
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// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®
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// lint-disable-file no-char-pointer
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import std;
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import Crafter.Build;
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#include "lint-rules.h"
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namespace fs = std::filesystem;
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using namespace Crafter;
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extern "C" Configuration CrafterBuildProject(std::span<const std::string_view> args) {
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// fingerprintd-core — the wire formats and state machines as a static
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// library of pure C++ modules. Deliberately free of GLib, libqcomtee and
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// every system header: the byte-level decisions in here were the whole
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// cost of this project, so they are pinned by tests that run on a dev box
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// with no phone, no TEE and no sensor.
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static auto Core = std::make_unique<Configuration>();
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Core->path = "./";
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Core->name = "fingerprintd-core";
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Core->outputName = "fingerprintd-core";
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ApplyStandardArgs(*Core, args);
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Core->type = ConfigurationType::LibraryStatic;
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{
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std::array<fs::path, 3> ifaces = {
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"interfaces/Fingerprintd",
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"interfaces/Fingerprintd-Sfs",
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"interfaces/Fingerprintd-Ta",
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};
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std::array<fs::path, 0> impls = {};
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Core->GetInterfacesAndImplementations(ifaces, impls);
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}
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// fingerprintd — the daemon: sensor rail, QTEE session, the gpfile and
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// RPMB listeners, and the bus surface, wrapped around the core.
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Configuration cfg;
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cfg.path = "./";
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cfg.name = "fingerprintd";
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cfg.outputName = "fingerprintd";
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ApplyStandardArgs(cfg, args);
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cfg.type = ConfigurationType::Executable;
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cfg.dependencies = { Core.get() };
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{
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std::array<fs::path, 0> ifaces = {};
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std::array<fs::path, 1> impls = { "implementations/main" };
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cfg.GetInterfacesAndImplementations(ifaces, impls);
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}
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cfg.AddTest("Sfs").Dependencies({ Core.get() });
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cfg.AddTest("Ta").Dependencies({ Core.get() });
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ProjectLint::AddProjectLintRules(cfg);
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return cfg;
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}
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