Class: Rex::Poly::MachineX86

Inherits:
Machine
  • Object
show all
Defined in:
lib/rex/poly/machine/x86.rb

Overview

A subclass to represent a Rex poly machine on the x86 architecture.

Constant Summary

Constants inherited from Machine

Rex::Poly::Machine::BYTE, Rex::Poly::Machine::DWORD, Rex::Poly::Machine::QWORD, Rex::Poly::Machine::WORD

Instance Method Summary collapse

Methods inherited from Machine

#assemble, #block_exist?, #block_next, #block_offset, #block_previous, #create_block, #create_variable, #generate, #is_valid?, #make_safe_byte, #make_safe_dword, #make_safe_qword, #make_safe_word, #release_temp_variable, #resolve_value, #solution_is_valid?, #solution_pop, #solution_push, #variable_exist?, #variable_value

Constructor Details

#initialize(badchars = '', consume_base_pointer = nil, consume_stack_pointer = true) ⇒ MachineX86

Returns a new instance of MachineX86.



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# File 'lib/rex/poly/machine/x86.rb', line 12

def initialize( badchars='', consume_base_pointer=nil, consume_stack_pointer=true )
  super( badchars, Metasm::Ia32.new )

  @reg_available << Rex::Arch::X86::EAX
  @reg_available << Rex::Arch::X86::EBX
  @reg_available << Rex::Arch::X86::ECX
  @reg_available << Rex::Arch::X86::EDX
  @reg_available << Rex::Arch::X86::ESI
  @reg_available << Rex::Arch::X86::EDI
  @reg_available << Rex::Arch::X86::EBP
  @reg_available << Rex::Arch::X86::ESP

  # By default we consume the EBP register if badchars contains \x00. This helps speed
  # things up greatly as many instructions opperating on EBP introduce a NULL byte. For
  # example, a MOV instruction with EAX as the source operand is as follows:
  #     8B08    mov ecx, [eax]
  # but the same instruction with EBP as the source operand is as follows:
  #     8B4D00  mov ecx, [ebp] ; This is assembled as 'mov ecx, [ebp+0]'
  # we can see that EBP is encoded differently with an offset included. We can still
  # try to generate a solution with EBP included and \x00 in the badchars list but
  # it can take considerably longer.
  if( ( consume_base_pointer.nil? and not Rex::Text.badchar_index( "\x00", @badchars ).nil? ) or consume_base_pointer == true )
    create_variable( 'base_pointer', 'ebp' )
  end

  # By default we consume the ESP register to avoid munging the stack.
  if( consume_stack_pointer )
    create_variable( 'stack_pointer', 'esp' )
  end

  # discover all the safe FPU instruction we can use.
  @safe_fpu_instructions = ::Array.new
  Rex::Arch::X86.fpu_instructions.each do | fpu |
    if( is_valid?( fpu ) )
      @safe_fpu_instructions << fpu
    end
  end
end

Instance Method Details

#create_block_primitive(block_name, primitive_name, *args) ⇒ Object

Overload this method to intercept the ‘set’ primitive with the ‘location’ keyword and create the block with the ‘_set_variable_location’. We do this to keep a consistent style.



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# File 'lib/rex/poly/machine/x86.rb', line 63

def create_block_primitive( block_name, primitive_name, *args )
  if( primitive_name == 'set' and args.length == 2 and args[1] == 'location' )
    _create_block_primitive( block_name, '_set_variable_location', args[0] )
  else
    super
  end
end

#native_size ⇒ Object

The general purpose registers are 32bit



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# File 'lib/rex/poly/machine/x86.rb', line 54

def native_size
  Rex::Poly::Machine::DWORD
end