ELF x86: Format string bug basic 1

root-me challenge: … or how to read through the stack.

Environment configuration:

PIE 	Position Independent Executable 	 No 
RelRO 	Read Only relocations 	                 No 
NX 	Non-Executable Stack 	                 No 
ASLR 	Address Space Layout Randomization 	 No 
SF 	Source Fortification 	                 No 
SSP 	Stack-Smashing Protection 	         No 
SRC 	Source code access 	                 Yes 

Source code:

#include <stdio.h>
#include <unistd.h>
int main(int argc, char *argv[]){
        FILE *secret = fopen("/challenge/app-systeme/ch5/.passwd", "rt");
        char buffer[32];
        fgets(buffer, sizeof(buffer), secret);
        return 0;