How To Run ANY COMMAND As The Owner Of The Script (setuid)

1. Save the below code as file a.c

    int main(int ac, char **av) {
        int uid;
        uid = geteuid();
        setreuid(uid, uid);

        char **arguments = av + 1;
        system(*arguments);

        return 0;
    }

2. As userA, compile it, ie

    gcc a.c -o aaa

3. As userA, set the sticky bit, ie

    chmod 4755 aaa

4. now you can run any command as UserA, like this:

    >aaa 'whoami'
    userA

    >aaa 'touch file1'
    >ls -al file1
    -rw-r----- 1 userA group