Protostar/Stack 0

If you get stuck, you can watch the solution and explanation here:

We will write our first Buffer Overflow for the stack0 level of exploit-exercises.com.

This level introduces the concept that memory can be accessed outside of its allocated region, how the stack variables are laid out, and that modifying outside of the allocated memory can modify program execution.

This level is at /opt/protostar/bin/stack0

stack0.c

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

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

  modified = 0;
  gets(buffer);

  if(modified != 0) {
      printf("you have changed the 'modified' variable\n");
  } else {
      printf("Try again?\n");
  }
}

See also

This video introduces http://exploit-exercises.com, how to connect to the VM with ssh and explains what setuid binaries are.

This is a mirror. Copyright and original can be found here: exploit-exercises.com/protostar/stack0/