54 lines
1.3 KiB
Ruby
54 lines
1.3 KiB
Ruby
# -*- coding: binary -*-
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require 'rex/encoder/xor/dword_additive'
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##
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#
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# Jmp/Call Dword Additive Feedback Encoder
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# Author: skape
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# Arch: x86
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#
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##
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module Rex
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module Encoders
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class XorDwordAdditive < Rex::Encoder::Xor::DwordAdditive
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module Backend
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def _unencoded_transform(data)
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# check for any dword aligned zeros that would falsely terminate the decoder
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idx = 0
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while true
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idx = data.index("\x00\x00\x00\x00", idx)
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break if !idx
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if idx & 3 == 0
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raise RuntimeError, "Unencoded data cannot have a dword aligned 0 dword!", caller()
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end
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idx += 1
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end
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# pad to a dword boundary and append null dword for termination
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data = data + ("\x00" * ((4 - data.length & 3) & 3)) + "\x00\x00\x00\x00"
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end
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def _prepend
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"\xfc" + # cld
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"\xbb" + key + # mov ebx, key
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"\xeb\x0c" + # jmp short 0x14
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"\x5e" + # pop esi
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"\x56" + # push esi
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"\x31\x1e" + # xor [esi], ebx
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"\xad" + # lodsd
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"\x01\xc3" + # add ebx, eax
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"\x85\xc0" + # test eax, eax
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"\x75\xf7" + # jnz 0xa
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"\xc3" + # ret
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"\xe8\xef\xff\xff\xff" # call 0x8
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end
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end
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include Backend
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end
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end end
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