metasploit-framework/modules/encoders/x86/nonupper.rb

##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# web site for more information on licensing and terms of use.
#   http://metasploit.com/
##


require 'msf/core'
require 'rex/encoder/nonupper'


class Metasploit3 < Msf::Encoder::NonUpper

	Rank = LowRanking

	def initialize
		super(
			'Name'             => "Non-Upper Encoder",
			'Description'      => %q{
					Encodes payloads as non-alpha based bytes. This allows
				payloads to bypass tolower() calls, but will fail isalpha().
				Table based design from Russel Sanford.
			},
			'Author'           => [ 'pusscat'],
			'Arch'             => ARCH_X86,
			'License'          => BSD_LICENSE,
			'EncoderType'      => Msf::Encoder::Type::NonUpper,
			'Decoder'          =>
				{
					'BlockSize' => 1,
				})
	end

	#
	# Returns the decoder stub that is adjusted for the size of the buffer
	# being encoded.
	#
	def decoder_stub(state)
		state.key                   = ""
		state.decoder_key_size      = 0
		Rex::Encoder::NonUpper::gen_decoder()
	end

	#
	# Encodes a one byte block with the current index of the length of the
	# payload.
	#
	def encode_block(state, block)
		begin
			newchar, state.key, state.decoder_key_size =
				Rex::Encoder::NonUpper::encode_byte(datastore['BadChars'], block.unpack('C')[0], state.key, state.decoder_key_size)
		rescue RuntimeError => e
			# This is a bandaid to deal with the fact that, since it's in
			# the Rex namespace, the encoder itself doesn't have access to the
			# Msf exception classes.  Turn it into an actual EncodingError
			# exception so the encoder doesn't look broken when it just fails
			# to encode.
			raise BadcharError if e.message == "BadChar"
		end
		return newchar
	end

	#
	# Fix stuff, and add the table :)
	#
	def encode_end(state)
		state.encoded.gsub!(/A/, state.decoder_key_size.chr)
		state.encoded.gsub!(/B/, (state.decoder_key_size+5).chr)
		state.encoded[0x24, 0] = state.key
	end
end