Question

Using this code (below) create a diagram that shows what the heap layout looks like and explain how to exploit it (Include a diagram) Include the following items:

1. Each chunk of memory allocated by malloc() and their metadata.
2. Their sizes in bytes.
3. The overflow direction in the heap.
4. The size of the overflowing buffer to reach and overwrite the metadata.
5. Overflow data that is meaningful for an exploit (this can be general).

Code:

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

int main(int a, char**b)

{

              char *c;

              c = malloc (10);

             

              strcpy(c, b[1]);

             

              free(c);

}

Answer 1

Heap based overflow is a type of buffer overflow that occurs in the heap data area. memory on the heap is dynamically allocated by the application at runtime and typically contains program data.

Exploitation is performed by corrupting this data in specific ways to cause the application to overwrite internal structures such as linked list pointer as shown in diagram.

The canonical heap overflow technique overwrites dynamic memory allocation linkage(such as malloc mata data) and uses the resulting pointer exchange to overwrite a program function pointer.

In order avoid heap overflow free blocks of heap memory are concatenated.