99 lines
2.2 KiB
Ruby
99 lines
2.2 KiB
Ruby
#!/usr/bin/env ruby
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require 'rex/text'
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module Rex
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module Encoder
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module Alpha2
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class Generic
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@@default_accepted_chars = ('a' .. 'z').to_a + ('B' .. 'Z').to_a + ('0' .. '9').to_a
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def Generic.gen_decoder_prefix(reg, offset)
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# Should never happen - have to pick a specifc
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# encoding:
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# alphamixed, alphaupper, unicodemixed, unicodeupper
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''
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end
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def Generic.gen_decoder(reg, offset)
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# same as above
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return ''
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end
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def Generic.gen_base_set(ignored_max=0x0f)
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# 0xf is max for XOR encodings - non-unicode
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max = 0x0f
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Rex::Text.shuffle_a(
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[* ( (0..(max-1)).map { |i| i *= 0x10 } ) ]
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)
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end
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def Generic.gen_second(block, base)
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# XOR encoder for ascii - unicode uses additive
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(block^base)
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end
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def Generic.encode_byte(block, badchars)
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accepted_chars = @@default_accepted_chars.dup
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# Remove bad chars from the accepted_chars list. Sadly 'A' must be
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# an accepted char or we'll certainly fail at this point. This could
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# be fixed later maybe with some recalculation of the encoder stubs...
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# - Puss
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(badchars || '').split('').each { |c| accepted_chars.delete(c) }
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first = 0
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second = 1
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randbase = 0
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gen_base_set(block).each do |randbase|
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second = gen_second(block, randbase)
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next if second < 0
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break if accepted_chars.include?(second.chr)
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end
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raise RuntimeError, "Negative" if second < 0
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raise RuntimeError, "BadChar; #{block} to #{second}" if not accepted_chars.include?(second.chr)
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if (randbase > 0xa0)
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# first num must be 4
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first = (randbase/0x10) + 0x40
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elsif (randbase == 0x00) || (randbase == 0x10)
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# first num must be 5
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first = (randbase/0x10) + 0x50
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else
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# pick one at "random"
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first = (randbase/0x10)
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if (first % 2)
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first += 0x40
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else
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randbase += 0x50
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end
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end
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# now add our new bytes :)
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first.to_i.chr + second.chr
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end
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def Generic.encode(buf, reg, offset, badchars = '')
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encoded = gen_decoder(reg, offset)
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buf.each_byte {
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|block|
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encoded += encode_byte(block, badchars)
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}
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encoded += add_terminator()
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return encoded
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end
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# 'A' signifies the end of the encoded shellcode
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def Generic.add_terminator()
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'AA'
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end
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end end end end |