Stack buffer overflow

overflow.c

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

int main(int argc, char **argv) {
  char buff[15];
  int auth = 0;
  
  printf("\nEnter password: ");
  gets(buff);

  if (strcmp(buff, "password") != 0) {
    printf("\nAccess denied\n");
  } else {
    auth = 1;
  }

  // Let's bypass this check!
  if (auth) {
    printf("\nAccess granted\n");
  }

  return 0;
}