47 lines
1.0 KiB
Ruby
47 lines
1.0 KiB
Ruby
require 'msf/core'
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module Msf
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module Encoders
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module X86
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class Call4Dword < Msf::Encoder::Xor
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def initialize
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super(
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'Name' => 'Call+4 Dword XOR Encoder',
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'Version' => '$Revision$',
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'Description' => 'Call+4 Dword XOR Encoder',
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'Author' => [ 'hdm', 'spoonm' ],
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'Arch' => ARCH_X86,
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'Decoder' =>
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{
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'KeySize' => 4,
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'BlockSize' => 4,
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})
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end
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#
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# Returns the decoder stub that is adjusted for the size of
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# the buffer being encoded
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#
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def decoder_stub(state)
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decoder =
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Rex::Arch::X86.sub(-(((state.buf.length - 1) / 4) + 1), Rex::Arch::X86::ECX,
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state.badchars) +
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"\xe8\xff\xff\xff" + # call $+4
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"\xff\xc0" + # inc eax
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"\x5e" + # pop esi
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"\x81\x76\x0eXORK" + # xor [esi + 0xe], xork
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"\x83\xee\xfc" + # sub esi, -4
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"\xe2\xf4" # loop xor
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# Calculate the offset to the XOR key
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state.decoder_key_offset = decoder.index('XORK')
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return decoder
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end
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end
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end end end
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