Ubuntu not giving root permissions to file, works on debian

Question

I'm trying to make a program a privileged program by doing the following:

1. sudo chown root
2. sudo chmod u+s

So now whenever someone runs , that user will be running that program with root privilege. This works as expected in debian. However, when I try on Ubuntu 20.0.4 LTS on Google compute engine, it doesn't run with root privileges.

The program's permissions are as follows: -rwsr-xr-x 1 root But for some reasons, whenever I run it on Ubuntu, it runs with the current users privilege. On debian, it runs as root (as outputted by ps -elf). Anyone know why this is?

Answer 1

It's per security measure on Ubuntu that the kernel just ignores the suid bit on all non-compiled executables ( Interpreted ).

It can be a serious security breach because anyone can change the script and populate it by anything he wants.

To do so ; knowing the risks ; You have to wrap your script with a non-interpreted language like C.

You can do ; create C file <path_to_to_your_prog>.c :

#include <stdio.h>
#include <stdlib.h> 
#include <sys/types.h> 
#include <unistd.h> 
int main() { 
    setuid( 0 );  
    system("<path_to_your_script>.sh" );
    return 0;
 }

Then compile it :

gcc <path_to_to_your_prog>.c -o 
 <path_to_the compiled_prog>

Then set the correct permissions :

chmod 4755   <path_to_the compiled_prog> # note the suid set here
chown root:root <path_to_the compiled_prog> <path_to_your_script>.sh
chmod 700 <path_to_your_script>.sh

Then run it :

<path_to_the_compiled_prog>

Solution 2 : Preferred

You can add a new group and make it as the secondary group of all the concerned users, then add it to your sudoers so they can run : sudo <script_path>.sh then set the correct permissions : 750 and onwership root:<gid> so they will be unable edit it.