Saturday, December 25, 2010

Warming up to the stack #3

#include <stdio.h>
int main() {
  int cookie;
  char buf[80];
  printf("buf: %08x cookie: %08x\n", &buf, &cookie);
  if (cookie == 0x01020005)
    printf("you win!\n");

Not much is new here. We exploit this the same was we did the first two except that we have a null character (ctrl @).

I want to point out one thing that I didn't mention on my previous posts. The address of cookie and buf are printed out so we don't really need to "guess" where they are on the stack. I ignored this before, because in real programs, the address values are rarely printed out.

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