voidf

Quick Start

$ make
$ ./voidf

setuid/setgid support

The application supports temporary privilege escalation via setuid/setgid bits. It uses the privilege only to scan /dev/input/* folder and open the selected input device. After that it lowers its privilege down to its real uid/gid and continues to function like a regular user application.

setuid example

# cp voidf /usr/local/bin
# chown root:root /usr/local/bin/voidf
# chmod 4755 /usr/local/bin/voidf

setgid example on Debian

On my Debian Stale 10 I have a group called input that has the access to /dev/input/* files. So this is what I do on my machine:

# cp voidf /usr/local/bin
# chown root:input /usr/local/bin/voidf
# chmod g+s /usr/local/bin/voidf

This way voidf is never ran with root privileges. It is only ran with temporary input group privilege just to open the input device file.

Controls

To increment the counter you have to type the sequence of characters voidf. Focus on the main window is not required.

The following actions do require the window focus tho:

References

• https://github.com/freedesktop-unofficial-mirror/evtest/blob/b8343ec1124da18bdabcc04809a8731b9e39295d/evtest.c
• https://www.gnu.org/software/libc/manual/html_node/Setuid-Program-Example.html