Bash drop priviliges

shell.c

int main()
{
	running_setuid = uidget();
	...
	if (running_setuid && privileged_mode == 0)
		disable_priv_mode();
	...	
	// start interactive shell or execute command
}


/* Fetch uids and gids, return 1 if we're running setuid or setgid. */
static int uidget()
{
	...
	current_user.uid = getuid();
	current_user.gid = getgid();
	current_user.euid = geteuid();
	current_user.egid = getegid();

	/* See whether or not we are running setuid or setgid. */
	return (current_user.uid != current_user.euid) ||
		(current_user.gid != current_user.egid);
}

void disable_priv_mode()
{
	setuid (current_user.uid);
	setgid (current_user.gid);
	current_user.euid = current_user.uid;
	current_user.egid = current_user.gid;
}