509 lines
19 KiB
Ruby
509 lines
19 KiB
Ruby
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module Rex
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module Poly
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#
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# A subclass to represent a Rex poly machine on the x86 architecture.
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#
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class MachineX86 < Rex::Poly::Machine
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def initialize( badchars='', consume_base_pointer=nil, consume_stack_pointer=true )
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super( badchars, Metasm::Ia32.new )
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@reg_available << Rex::Arch::X86::EAX
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@reg_available << Rex::Arch::X86::EBX
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@reg_available << Rex::Arch::X86::ECX
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@reg_available << Rex::Arch::X86::EDX
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@reg_available << Rex::Arch::X86::ESI
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@reg_available << Rex::Arch::X86::EDI
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@reg_available << Rex::Arch::X86::EBP
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@reg_available << Rex::Arch::X86::ESP
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# By default we consume the EBP register if badchars contains \x00. This helps speed
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# things up greatly as many instructions opperating on EBP introduce a NULL byte. For
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# example, a MOV instruction with EAX as the source operand is as follows:
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# 8B08 mov ecx, [eax]
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# but the same instruction with EBP as the source operand is as follows:
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# 8B4D00 mov ecx, [ebp] ; This is assembled as 'mov ecx, [ebp+0]'
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# we can see that EBP is encoded differently with an offset included. We can still
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# try to generate a solution with EBP included and \x00 in the badchars list but
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# it can take considerably longer.
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if( ( consume_base_pointer.nil? and not Rex::Text.badchar_index( "\x00", @badchars ).nil? ) or consume_base_pointer == true )
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create_variable( 'base_pointer', 'ebp' )
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end
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# By default we consume the ESP register to avoid munging the stack.
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if( consume_stack_pointer )
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create_variable( 'stack_pointer', 'esp' )
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end
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# discover all the safe FPU instruction we can use.
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@safe_fpu_instructions = ::Array.new
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Rex::Arch::X86.fpu_instructions.each do | fpu |
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if( is_valid?( fpu ) )
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@safe_fpu_instructions << fpu
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end
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end
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end
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#
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# The general purpose registers are 32bit
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#
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def native_size
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Rex::Poly::Machine::DWORD
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end
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#
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# Overload this method to intercept the 'set' primitive with the 'location' keyword
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# and create the block with the '_set_variable_location'. We do this to keep a
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# consistent style.
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#
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def create_block_primitive( block_name, primitive_name, *args )
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if( primitive_name == 'set' and args.length == 2 and args[1] == 'location' )
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_create_block_primitive( block_name, '_set_variable_location', args[0] )
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else
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super
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end
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end
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#
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# XXX: If we have a loop primitive, it is a decent speed bump to force the associated variable
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# of the first loop primitive to be assigned as ECX (for the x86 LOOP instruction), this is not
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# neccasary but can speed generation up significantly.
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#
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#def generate
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# @blocks.each_value do | block |
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# if( block.first.primitive == 'loop' )
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# @variables.delete( block.first.args.first )
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# create_variable( block.first.args.first, 'ecx' )
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# break
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# end
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# end
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# # ...go go go
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# super
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#end
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protected
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#
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# Resolve a register number into a suitable register name.
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#
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def _register_value( regnum, size=nil )
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value = nil
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# we default to a native 32 bits if no size is specified.
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if( size.nil? )
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size = native_size()
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end
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if( size == Rex::Poly::Machine::DWORD )
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value = Rex::Arch::X86::REG_NAMES32[ regnum ]
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elsif( size == Rex::Poly::Machine::WORD )
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value = Rex::Arch::X86::REG_NAMES16[ regnum ]
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elsif( size == Rex::Poly::Machine::BYTE )
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# (will return nil for ESI,EDI,EBP,ESP)
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value = Rex::Arch::X86::REG_NAMES8L[ regnum ]
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else
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raise RuntimeError, "Register number '#{regnum}' (size #{size.to_i}) is unavailable."
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end
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return value
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end
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#
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# Create the x86 primitives.
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#
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def _create_primitives
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#
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# Create the '_set_variable_location' primitive. The first param it the variable to place the current
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# blocks location value in.
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#
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_create_primitive( '_set_variable_location',
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::Proc.new do | block, machine, variable |
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if( @safe_fpu_instructions.empty? )
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raise UnallowedPermutation
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end
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[
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"dw #{ "0x%04X" % [ @safe_fpu_instructions[ rand(@safe_fpu_instructions.length) ].unpack( 'v' ).first ] }",
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"mov #{machine.variable_value( 'temp' )}, esp",
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"fnstenv [ #{machine.variable_value( 'temp' )} - 12 ]",
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"pop #{machine.variable_value( variable )}"
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]
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end,
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::Proc.new do | block, machine, variable |
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if( @safe_fpu_instructions.empty? )
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raise UnallowedPermutation
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end
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[
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"dw #{ "0x%04X" % [ @safe_fpu_instructions[ rand(@safe_fpu_instructions.length) ].unpack( 'v' ).first ] }",
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"mov #{machine.variable_value( 'temp' )}, esp",
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"fnstenv [ #{machine.variable_value( 'temp' )} - 12 ]",
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"pop #{machine.variable_value( variable )}"
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]
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end,
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::Proc.new do | block, machine, variable |
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if( @safe_fpu_instructions.empty? )
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raise UnallowedPermutation
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end
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[
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"dw #{ "0x%04X" % [ @safe_fpu_instructions[ rand(@safe_fpu_instructions.length) ].unpack( 'v' ).first ] }",
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"push esp",
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"pop #{machine.variable_value( 'temp' )}",
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"fnstenv [ #{machine.variable_value( 'temp' )} - 12 ]",
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"pop #{machine.variable_value( variable )}"
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]
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end,
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::Proc.new do | block, machine, variable |
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if( @safe_fpu_instructions.empty? )
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raise UnallowedPermutation
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end
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[
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"dw #{ "0x%04X" % [ @safe_fpu_instructions[ rand(@safe_fpu_instructions.length) ].unpack( 'v' ).first ] }",
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"fnstenv [ esp - 12 ]",
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"pop #{machine.variable_value( variable )}"
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]
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end,
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::Proc.new do | block, machine, variable |
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[
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"call $+5",
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"pop #{machine.variable_value( variable )}",
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"push #{machine.block_offset( block ) + 5}",
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"pop #{machine.variable_value( 'temp' )}",
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"sub #{machine.variable_value( variable )}, #{machine.variable_value( 'temp' )}"
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]
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end,
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::Proc.new do | block, machine, variable |
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[
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"db 0xE8, 0xFF, 0xFF, 0xFF, 0xFF, 0xC0",
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"pop #{machine.variable_value( variable )}",
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"push #{machine.block_offset( block ) + 5}",
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"pop #{machine.variable_value( 'temp' )}",
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"sub #{machine.variable_value( variable )}, #{machine.variable_value( 'temp' )}"
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]
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end
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)
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#
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# Create the 'loop' primitive. The first param it the counter variable which holds the number of
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# times to perform the loop. The second param it the destination block to loop to.
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#
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_create_primitive( 'loop',
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::Proc.new do | block, machine, counter, destination |
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if( machine.variable_value( counter ) != Rex::Arch::X86::REG_NAMES32[ Rex::Arch::X86::ECX ] )
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# we raise and UndefinedPermutation exception to indicate that untill a valid register (ECX) is
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# chosen we simply can't render this. This lets the machine know we can still try to use this
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# permutation and at a later stage the requirements (counter==ecx) may be satisfied.
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raise UndefinedPermutation
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end
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offset = -( machine.block_offset( machine.block_next( block ) ) - machine.block_offset( destination ) )
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Rex::Arch::X86.loop( offset )
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end,
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::Proc.new do | block, machine, counter, destination |
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offset = -( machine.block_offset( machine.block_next( block ) ) - machine.block_offset( destination ) )
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[
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"dec #{machine.variable_value( counter )}",
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"test #{machine.variable_value( counter )}, #{machine.variable_value( counter )}",
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# JNZ destination
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"db 0x0F, 0x85 dd #{ "0x%08X" % [ offset & 0xFFFFFFFF ] }"
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]
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end
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)
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#
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# Create the 'xor' primitive. The first param it the variable to xor with the second param value which
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# can be either a variable, literal or block offset.
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#
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_create_primitive( 'xor',
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::Proc.new do | block, machine, variable, value |
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[
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"xor #{machine.variable_value( variable )}, #{machine.resolve_value( value )}"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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# a ^ b == (a | b) & ~(a & b)
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[
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"mov #{machine.variable_value( 'temp' )}, #{machine.variable_value( variable )}",
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"or #{machine.variable_value( 'temp' )}, #{machine.resolve_value( value )}",
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"and #{machine.variable_value( variable )}, #{machine.resolve_value( value )}",
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"not #{machine.variable_value( variable )}",
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"and #{machine.variable_value( variable )}, #{machine.variable_value( 'temp' )}"
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]
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end
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)
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#
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# Create the 'goto' primitive. The first param is a destination block to jump to.
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#
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_create_primitive( 'goto',
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::Proc.new do | block, machine, destination |
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offset = -( machine.block_offset( machine.block_next( block ) ) - machine.block_offset( destination ) )
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if( ( offset > 0 and offset > 127 ) or ( offset < 0 and offset < -127 ) )
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raise UnallowedPermutation
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end
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[
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# short relative jump
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"db 0xEB db #{ "0x%02X" % [ offset & 0xFF ] }"
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]
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end,
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::Proc.new do | block, machine, destination |
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offset = -( machine.block_offset( machine.block_next( block ) ) - machine.block_offset( destination ) )
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[
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# near relative jump
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"db 0xE9 dd #{ "0x%08X" % [ offset & 0xFFFFFFFF ] }"
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]
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end
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)
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#
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# Create the 'add' primitive. The first param it the variable which will be added to the second
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# param, which may either be a literal number value, a variables assigned register or a block
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# name, in which case the block offset will be used.
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#
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_create_primitive( 'add',
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::Proc.new do | block, machine, variable, value |
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if( machine.variable_exist?( value ) )
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raise UnallowedPermutation
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end
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[
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"lea #{machine.variable_value( variable )}, [ #{machine.variable_value( variable )} + #{machine.resolve_value( value )} ]"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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[
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"push #{machine.resolve_value( value )}",
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"add #{machine.variable_value( variable )}, [esp]",
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"pop #{machine.variable_value( 'temp' )}"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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[
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"add #{machine.variable_value( variable )}, #{machine.resolve_value( value )}"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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if( machine.variable_exist?( value ) )
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raise UnallowedPermutation
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end
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[
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"sub #{machine.variable_value( variable )}, #{ "0x%08X" % [ ~(machine.resolve_value( value ) - 1) & 0xFFFFFFFF ] }"
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]
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end
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# ::Proc.new do | block, machine, variable, value |
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# if( machine.variable_exist?( value ) )
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# raise UnallowedPermutation
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# end
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# [
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# "push #{ "0x%08X" % [ ~(machine.resolve_value( value ) - 1) & 0xFFFFFFFF ] }",
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# "pop #{machine.variable_value( 'temp' )}",
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# "not #{machine.variable_value( 'temp' )}",
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# "add #{machine.variable_value( variable )}, #{machine.variable_value( 'temp' )}"
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# ]
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# end,
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# ::Proc.new do | block, machine, variable, value |
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# if( machine.variable_exist?( value ) )
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# raise UnallowedPermutation
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# end
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# [
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# "xor #{machine.variable_value( 'temp' )}, #{machine.variable_value( 'temp' )}",
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# "mov #{machine.variable_value( 'temp', 16 )}, #{ "0x%04X" % [ ~(machine.resolve_value( value ) - 1) & 0xFFFF ] }",
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# "not #{machine.variable_value( 'temp', 16 )}",
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# "add #{machine.variable_value( variable )}, #{machine.variable_value( 'temp' )}"
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# ]
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# end,
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)
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#
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# Create the 'set' primitive. The first param it the variable which will be set. the second
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# param is the value to set the variable to (a variable, block or literal).
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#
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_create_primitive( 'set',
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::Proc.new do | block, machine, variable, value |
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if( machine.variable_exist?( value ) )
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raise UnallowedPermutation
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end
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[
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"push #{ "0x%08X" % [ ~machine.resolve_value( value ) & 0xFFFFFFFF ] }",
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"pop #{machine.variable_value( variable )}",
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"not #{machine.variable_value( variable )}"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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if( machine.variable_exist?( value ) )
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raise UnallowedPermutation
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end
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if( machine.resolve_value( value, WORD ) > 0xFFFF )
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raise UndefinedPermutation
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end
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[
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"xor #{machine.variable_value( variable )}, #{machine.variable_value( variable )}",
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"mov #{machine.variable_value( variable, WORD )}, #{ "0x%04X" % [ ~machine.resolve_value( value, WORD ) & 0xFFFF ] }",
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"not #{machine.variable_value( variable, WORD )}"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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[
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"push #{machine.resolve_value( value )}",
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"pop #{machine.variable_value( variable )}"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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[
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"mov #{machine.variable_value( variable )}, #{machine.resolve_value( value )}"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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if( machine.variable_exist?( value ) )
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raise UnallowedPermutation
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end
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if( machine.resolve_value( value, WORD ) > 0xFFFF )
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raise UndefinedPermutation
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end
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[
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"xor #{machine.variable_value( variable )}, #{machine.variable_value( variable )}",
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"mov #{machine.variable_value( variable, WORD )}, #{ "0x%04X" % [ machine.resolve_value( value, WORD ) & 0xFFFF ] }"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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if( machine.variable_exist?( value ) )
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raise UnallowedPermutation
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end
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dword = machine.make_safe_dword( machine.resolve_value( value ) )
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[
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"mov #{machine.variable_value( variable )}, #{ "0x%08X" % [ dword ] }",
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"sub #{machine.variable_value( variable )}, #{ "0x%08X" % [ dword - machine.resolve_value( value ) ] }"
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]
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end,
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::Proc.new do | block, machine, variable, value |
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if( machine.variable_exist?( value ) )
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raise UnallowedPermutation
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end
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dword = machine.make_safe_dword( machine.resolve_value( value ) )
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[
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"mov #{machine.variable_value( variable )}, #{ "0x%08X" % [ dword - machine.resolve_value( value ) ] }",
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"add #{machine.variable_value( variable )}, #{ "0x%08X" % [ ~dword & 0xFFFFFFFF ] }",
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"not #{machine.variable_value( variable )}"
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]
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end
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)
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#
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# Create the 'load' primitive. The first param it the variable which will be set. The second
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# param is the value (either a variable or literal) to load from. the third param is the size
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# of the load operation, either DWORD, WORD or BYTE.
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#
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_create_primitive( 'load',
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::Proc.new do | block, machine, variable, value, size |
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result = nil
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if( size == Rex::Poly::Machine::DWORD )
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result = [ "mov #{machine.variable_value( variable )}, [#{machine.resolve_value( value )}]" ]
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elsif( size == Rex::Poly::Machine::WORD )
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result = [ "movzx #{machine.variable_value( variable )}, word [#{machine.resolve_value( value )}]" ]
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elsif( size == Rex::Poly::Machine::BYTE )
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result = [ "movzx #{machine.variable_value( variable )}, byte [#{machine.resolve_value( value )}]" ]
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else
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raise InvalidPermutation
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end
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result
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end,
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::Proc.new do | block, machine, variable, value, size |
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result = nil
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if( size == Rex::Poly::Machine::DWORD )
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# we raise and UnallowedPermutation here as this permutation should only satisfy requests for
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# sizes of WORD or BYTE, any DWORD requests will be satisfied by the above permutation (otherwise
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# we would just be duplicating a 'mov dest, [src]' sequence which is the same as above.
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raise UnallowedPermutation
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elsif( size == Rex::Poly::Machine::WORD )
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result = [
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"mov #{machine.variable_value( variable )}, [#{machine.resolve_value( value )}]",
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"shl #{machine.variable_value( variable )}, 16",
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"shr #{machine.variable_value( variable )}, 16"
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]
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elsif( size == Rex::Poly::Machine::BYTE )
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result = [
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"mov #{machine.variable_value( variable )}, [#{machine.resolve_value( value )}]",
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"shl #{machine.variable_value( variable )}, 24",
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"shr #{machine.variable_value( variable )}, 24"
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]
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else
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raise InvalidPermutation
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end
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result
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end,
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::Proc.new do | block, machine, variable, value, size |
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result = nil
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if( size == Rex::Poly::Machine::DWORD )
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result = [
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"push [#{machine.resolve_value( value )}]",
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"pop #{machine.variable_value( variable )}"
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]
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elsif( size == Rex::Poly::Machine::WORD )
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result = [
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"push [#{machine.resolve_value( value )}]",
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"pop #{machine.variable_value( variable )}",
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"shl #{machine.variable_value( variable )}, 16",
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"shr #{machine.variable_value( variable )}, 16"
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]
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elsif( size == Rex::Poly::Machine::BYTE )
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result = [
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"push [#{machine.resolve_value( value )}]",
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"pop #{machine.variable_value( variable )}",
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"shl #{machine.variable_value( variable )}, 24",
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"shr #{machine.variable_value( variable )}, 24"
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]
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else
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raise InvalidPermutation
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end
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result
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end
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)
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#
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# Create the 'store' primitive.
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#
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|
_create_primitive( 'store',
|
|
::Proc.new do | block, machine, variable, value, size |
|
|
result = nil
|
|
if( size == Rex::Poly::Machine::DWORD )
|
|
result = [ "mov [#{machine.variable_value( variable )}], #{machine.resolve_value( value )}" ]
|
|
elsif( size == Rex::Poly::Machine::WORD )
|
|
result = [ "mov word [#{machine.variable_value( variable )}], #{machine.resolve_value( value, WORD )}" ]
|
|
elsif( size == Rex::Poly::Machine::BYTE )
|
|
if( machine.resolve_value( value, BYTE ).nil? )
|
|
# so long as we cant resolve the variable to an 8bit register value (AL,BL,CL,DL) we must raise
|
|
# an UndefinedPermutation exception (this will happen when the variable has been assigned to ESI,
|
|
# EDI, EBP or ESP which dont have a low byte representation)
|
|
raise UndefinedPermutation
|
|
end
|
|
result = [ "mov byte [#{machine.variable_value( variable )}], #{machine.resolve_value( value, BYTE )}" ]
|
|
else
|
|
raise InvalidPermutation
|
|
end
|
|
result
|
|
end,
|
|
::Proc.new do | block, machine, variable, value, size |
|
|
result = nil
|
|
if( size == Rex::Poly::Machine::DWORD )
|
|
result = [
|
|
"push #{machine.resolve_value( value )}",
|
|
"pop [#{machine.variable_value( variable )}]"
|
|
]
|
|
elsif( size == Rex::Poly::Machine::WORD )
|
|
result = [
|
|
"push #{machine.resolve_value( value, WORD )}",
|
|
"pop word [#{machine.variable_value( variable )}]"
|
|
]
|
|
else
|
|
# we can never do this permutation for BYTE size (or any other size)
|
|
raise UnallowedPermutation
|
|
end
|
|
result
|
|
end
|
|
)
|
|
end
|
|
|
|
end
|
|
|
|
end
|
|
|
|
end
|