Elan 04f3:0c6e Fingerprint Reader Fix for Linux

This repository provides a working libfprint driver (elanpress) for the Elan 04f3:0c6e fingerprint sensor, commonly found in various ASUS laptops (such as the Zenbook 14, ROG Flow X13, and others).

---

The Problem

Upstream libfprint misclassifies the 04f3:0c6e sensor under the standard elan swipe driver:

1. Swipe vs. Touch Misclassification: The sensor is physically a touch/press pad, but upstream hardcodes the driver class to FP_SCAN_TYPE_SWIPE. As a result, the desktop environment and fprintd expect continuous swiping gestures, leading to "swipe too short" errors.
2. Hardware Wedging / Protocol Error: When polling the hardware presence byte (pre_scan_cmd), the sensor unblocks once and then wedges at "finger present" until a power cycle or times out, returning unexpected status bytes (0x00, 0xaf). The standard driver treats this as a fatal FP_DEVICE_ERROR_PROTO, aborting the session and reporting "device disconnected".
3. Matcher Incompatibility: Upstream libfprint uses the NIST NBIS Bozorth3 minutiae matcher. Bozorth3 expects large swiped impressions with many minutiae points (threshold 24). The compact touch pad yields too few minutiae for Bozorth3, causing "verify-no-match" even when enrollment succeeds.

---

The Solution

This fork integrates the dedicated elanpress driver:

• Native Press/Touch Support: Configured natively as a press sensor (FP_SCAN_TYPE_PRESS).
• Image-Based Presence Detection: Bypasses the unreliable hardware status byte by inferring finger presence directly from sensor image data.
• SIFT Keypoint Matching: Replaces Bozorth3 with a robust SIFT (Scale-Invariant Feature Transform) keypoint matcher designed specifically for compact touch pads.
• Multi-Stage Enrollment: Captures 12 presses during enrollment to construct a complete composite representation of the finger pad.

---

How to Build & Install

1. Install Build Dependencies

• Fedora:

  sudo dnf install meson ninja gcc git libgusb-devel pixman-devel openssl-devel systemd-devel glib2-devel
  

• Ubuntu / Debian:

  sudo apt install meson ninja-build gcc git libgusb-dev libpixman-1-dev libssl-dev libsystemd-dev libglib2.0-dev
  

• Arch Linux: Available via the AUR as libfprint-elanpress-git.

2. Build the Library

git clone -b elan-0c6e-touch-support https://github.com/FCsab/Elan-04f3-0c6e-fingerprint-reader-fix.git
cd Elan-04f3-0c6e-fingerprint-reader-fix
meson setup build --prefix=/usr -Ddoc=false -Dintrospection=false
ninja -C build

3. Install & Restart Service

[!IMPORTANT] Keep backups outside of /usr/lib64/: Do not store backup copies (such as .stock or .bak) directly in /usr/lib64/. Because shared libraries contain an internal SONAME (libfprint-2.so.2), ldconfig automatically scans all files in /usr/lib64/ and will repoint the active symlink back to the stock library on the next system update! Always store backups in /var/backups/libfprint/.

# 1. Safely backup stock library outside the library linker search path
sudo mkdir -p /var/backups/libfprint
sudo cp /usr/lib64/libfprint-2.so.2.0.0 /var/backups/libfprint/ 2>/dev/null || \
sudo cp /usr/lib/x86_64-linux-gnu/libfprint-2.so.2.0.0 /var/backups/libfprint/ 2>/dev/null

# 2. Install compiled library
sudo ninja -C build install

# 3. Update linker cache and restart fprintd
sudo ldconfig
sudo systemctl restart fprintd

---

Enrolling & Testing

1. Delete any old prints:

   fprintd-delete $USER
   

2. Enroll your fingerprint:

   fprintd-enroll
   

   [!TIP] Enrollment Tips & Responsiveness:

   • Lift your finger completely between presses for about 1 second. The driver requires 10 consecutive empty polls to ensure you have lifted your finger so the same press isn't sampled twice. Tapping too quickly before the sensor registers a full release will ignore the press.
   • Press firmly. Light or partial touches with low contrast are automatically filtered out to ensure template quality, requiring an extra press.
   • Vary your position slightly (center, left side, right side, fingertip) across the 12 stages to allow SIFT to map the entire finger pad.

3. Verify:

   fprintd-verify
   

   Touch the sensor once to confirm recognition.

4. Lock Screen: Lock your screen (Super + L) and unlock using your fingerprint sensor.

---

Troubleshooting & Surviving System Updates

If an update reverts the fix or fprintd reports a protocol error:

1. Check where the symlink points:

   ls -l /usr/lib64/libfprint-2.so.2
   

   If it points to a .stock or .bak file, move the backup file out of /usr/lib64/:

   sudo mkdir -p /var/backups/libfprint
   sudo mv /usr/lib64/libfprint-2.so.2.0.0.* /var/backups/libfprint/ 2>/dev/null || true
   sudo ldconfig
   sudo systemctl restart fprintd
   

2. If a Fedora update overwrites libfprint-2.so.2.0.0 with upstream stock: Simply re-install from your build directory:

   cd ~/git/libfprint  # or wherever your repo is cloned
   sudo ninja -C build install
   sudo ldconfig
   sudo systemctl restart fprintd
   

---

AI Disclosure

In the spirit of transparency, AI tools were used in the development of this repository:

• Codebase research, driver porting/integration onto modern libfprint, meson build configurations, protocol debugging, and documentation were performed with the assistance of Google DeepMind's Antigravity AI coding assistant.
• All changes were compiled, inspected, and tested on actual hardware (04f3:0c6e on ASUS laptop) before committing.

---

Credits & Acknowledgements

• Dedicated driver logic and SIFT matcher based on the work by Filip Spanne (elanpress).
• Upstream driver framework provided by the libfprint project.