Add Goodix 27c6:5e0a (fw 10034) driver with dual TLS-PSK and SIGFM

[carminezac]

Description

This PR adds full enrollment and verification support for the Goodix 27c6:5e0a
fingerprint sensor (firmware GFUSB_GM168SEC_APP_10034), commonly found in
realme Book Prime and other laptop models.

Device details

• USB ID: 27c6:5e0a
• Firmware: GFUSB_GM168SEC_APP_10034
• Sensor: 80x88 pixels, 12-bit depth, 4/6 packed encoding
• Chip family: Goodix "Chicago H" / Milan HU series

What was reverse-engineered

The Windows driver (Wbdi.dll V3.0.141.150) was analyzed with radare2 to
reconstruct:

• The complete MCU command map (0x00 NOP through 0xe4 PresetPskRead)
• OTP (one-time programmable) data parsing with triple-redundancy validation
• Chip configuration construction from OTP values (tcode, DAC, FDT delta)
• FDT calibration algorithm (GetFdtManualBase / CalcFdtBase)
• The dual-TLS session architecture (command channel vs. image channel)
• Frame decoding (4/6 byte packing, no header/footer unlike 5110)
• Scan state machine transitions (FDT_DOWN, capture, FDT_UP cycle)

Key technical contributions

1. Dual TLS-PSK architecture. The 5e0a establishes two independent TLS-PSK
   sessions over a single USB pipe: a command channel (PSK = all zeros,
   flags 0xbb020001) for MCU commands, and an image channel using a
   device-specific PSK extracted from the Windows driver via DPAPI. The driver
   manages both sessions through the existing goodixtls socketpair model.

2. Dynamic FDT calibration. Instead of using static FDT thresholds, the
   driver reads the sensor's FDT manual base data (cmd 0x36) at init time and
   computes per-zone touch detection thresholds dynamically. This matches the
   Windows driver's CalcFdtBase algorithm and is essential for reliable
   finger-down/finger-up detection across different hardware units.

3. SIGFM matcher integration. The 80x88 sensor produces images too small
   for NBIS/Bozorth3 to match reliably (typically only 5-12 minutiae). This
   PR integrates SIGFM, a
   SIFT-based matcher that extracts far more features from small images.
   SIGFM uses OpenCV SIFT keypoints with Lowe's ratio test, geometric
   verification (vector length + angle consistency), and requires a minimum
   of 25 keypoints per image and 5 good matches for a positive result.

4. Baseline subtraction. A calibration frame is captured at init (no finger
   present) and subtracted from every scan to remove fixed-pattern noise.

5. "Thirds" normalization. Pixel intensities are mapped through a
   percentile-based three-band normalization (similar to Elan drivers) rather
   than simple min/max scaling, improving contrast on the small sensor area.

6. Correct FDT_UP prefix. The FDT_UP command uses prefix 0x0E (not
   0x0C), confirmed through RE of the Windows driver. This is critical for
   proper finger-lift detection between enrollment stages.

PSK extraction

The image-channel PSK is device-specific and must be extracted from a Windows
installation where the Goodix driver has been used at least once:

1. Boot Windows and enroll at least one fingerprint.
2. Locate the PSK blob stored by the Goodix driver (protected with DPAPI).
3. Decrypt using the machine DPAPI master key (tools like mimikatz or
   dpapi.py from Impacket work).
4. Place the resulting 32-byte hex key at /etc/libfprint/goodix-5e0a.psk.

Python tooling for the extraction process:
https://github.com/carminezac/libfprint-goodix/blob/goodixtls/tools/extract_psk.py

Build dependencies

• Standard libfprint dependencies (glib, libusb, OpenSSL, meson, ninja)
• OpenCV 4.x (libopencv-dev / opencv package) -- required for the SIGFM matcher
• C++17 compiler -- SIGFM is written in C++

Testing status

• Enrollment: 20/20 stages passed, 0 retries required
• Verification: match on first attempt
• Tested on a single hardware unit with firmware 10034
• GNOME/GDM integration: not yet tested

Files changed

New files:

• libfprint/drivers/goodixtls/goodix5e0a.c (~1000 lines) -- driver implementation
• libfprint/drivers/goodixtls/goodix5e0a.h -- constants, FDT payloads, frame geometry
• libfprint/sigfm/sigfm.cpp -- SIFT extraction and matching
• libfprint/sigfm/sigfm.hpp -- C API header
• libfprint/sigfm/binary.hpp -- serialization for enrolled print storage
• libfprint/sigfm/img-info.hpp -- keypoint/descriptor container
• libfprint/sigfm/meson.build -- build config for libsigfm

Modified files:

• meson.build -- add 5e0a driver, OpenCV dependency, SIGFM subdir
• libfprint/drivers/goodixtls/goodix.c -- dual-TLS session support
• libfprint/drivers/goodixtls/goodix.h -- image PSK field in device struct

Documentation:

• RE_INIT_SEQUENCE.md -- full MCU command map and init flow
• RE_FDT_CALIBRATION.md -- FDT threshold computation algorithm
• RE_SCAN_FLOW.md -- scan state machine and FDT response parsing
• RE_IMAGE_PROCESSING.md -- frame decode and normalization
• RE_OTP_SENSOR_CONFIG.md -- OTP data layout and config construction

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