Question

int main()

{

system("ls");

return 0;

}

Please compile the above program, and change its owner to root, and make it a Set-UID program. Can you let this Set-UID program run your code instead of /bin/ls? If you can, is your code running with the root privilege? Describe and explain your observations.

Answer 1

To change the file permission use chmod command to give the permission to the file.

in the command prompt enter the chmod u+s "File_Name.c". It will set the UID of the file

The code is not running with root privilege. But the file is running with the root privilege.

//include the header file

#include<stdio.h>

#include <stdlib.h>

int main()

{

    system("ls"); //it will execute the command

    return 0;

}

USER$ ls -l systemLSS.c
---------- 1 USER staff 134 Sep 15 19:08 systemLSS.c
USER$ chmod u+s systemLSS.c
USER$ ls -l systemLSS.c
---S------ 1 USER staff 134 Sep 15 19:08 systemLSS.c
USER$ gcc systemLSS.c -o systemLSS
error: error reading 'systemLSS.c'
1 error generated.

Enter the command with sudo to run the program and enter the root password
USER$ sudo gcc systemLSS.c -o systemLSS
Password:

Run the program to list the file in the directory which the user has the file
USER$ ./systemLSS
Animal                   filreadwrite.c
AnimalBirdChoose.cpp           filreadwrite.layout
ArraySum.cpp               filreadwrite.o