tmux guest session

tmux.c

// tmux.c
// compile using: cc -o tmux tmux.c
// makeit setuid executable by: chmod +s tmux
// also change owner to desired user: [sudo] chown {usernamehere} tmux
// give it to guests' shell (passwd entry): guest::9999:99:guest user:/tmp:/opt/tmux
// you can delete password with passwd -du {login}
// allow empty passwords with PermitEmptyPasswords yes in sshd_config

// update (18 aug 2016): added dynamic owner change, for security ofc :)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>

#define BUFFER_SIZE 80

int main(int argc, char **argv)
{
	// get owner of current executable
	struct stat fstat;
	stat(argv[0],&fstat);
	setuid(fstat.st_uid);
	// allocate buffer to set commandline
	char buf[BUFFER_SIZE];
	// set tmux parameters to attach
	sprintf(buf,"/usr/bin/tmux -S /tmp/tmux-%d/default attach -r || echo failed;",fstat.st_uid);
	// execute!
	execlp("/bin/sh","$SHELL","-c",buf,NULL);
	return 0;
}