nock

A minimal X11 screen locker built with XCB and PAM.

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Features

• Fullscreen lockscreen window covering 1920x1080
• PAM authentication against the current user account
• Keyboard grab to prevent input routing to other windows
• Toggle password visibility on/off with a mouse click
• Supports letters, numbers, symbols, spacebar, and backspace
• Escape key exits (useful during development/testing)

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Installation

Dependencies

• libxcb
• libxcb-keysyms
• libxcb-util
• libpam
• libpam-misc

On Arch-based systems:

sudo pacman -S libxcb xcb-util-keysyms pam

On Debian/Ubuntu-based systems:

sudo apt install libxcb1-dev libxcb-keysyms1-dev libxcb-util-dev libpam0g-dev

PAM config

Run the install script once as root to set up the PAM service file:

sudo ./install.sh

This creates /etc/pam.d/nock which delegates auth to system-local-login.

Build

make

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Usage

Run the binary directly:

./nock

nock will grab the keyboard and display a fullscreen white window. Type your password and press Enter. Click anywhere to toggle whether the password is shown or hidden.

To unlock: type your user password and press Enter.
To exit during development: press Escape.

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Todo

• Proper fullscreen support
• Error handling for font/graphics context setup
• Error handling for keyboard grab
• Configurable resolution (currently hardcoded to 1920x1080)
• PAM error message display in the window
• Support for more special characters and key combinations
• Mouse pointer grab alongside keyboard grab
• Proper session unlock integration (e.g. hook into a display manager or systemd-logind)