81 lines
1.9 KiB
Ruby
81 lines
1.9 KiB
Ruby
##
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# $Id$
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##
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##
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# This file is part of the Metasploit Framework and may be subject to
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# redistribution and commercial restrictions. Please see the Metasploit
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# Framework web site for more information on licensing and terms of use.
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# http://metasploit.com/framework/
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##
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require 'msf/core'
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class Metasploit3 < Msf::Encoder
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# Has some issues, but overall it's pretty good
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# - printf(1) may not be available
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# - requires: "\x7c\x73\x68\x5c\x78"
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# - doesn't work on windows
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# - min size increase: 4x + 9
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# - max size increase: 4x + 14
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Rank = GoodRanking
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def initialize
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super(
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'Name' => 'Generic printf(1) Utility Command Encoder',
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'Version' => '$Revision$',
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'Description' => %q{
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This encoder uses the printf(1) utility to avoid restricted
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characters. Some shell variable substituion may also be used
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\if needed symbols are blacklisted.
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},
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'Author' => 'jduck',
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'Arch' => ARCH_CMD,
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'EncoderType' => Msf::Encoder::Type::PrintfUtil)
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end
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#
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# Encodes the payload
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#
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def encode_block(state, buf)
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# Skip encoding for empty badchars
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if(state.badchars.length == 0)
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return buf
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end
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# If backslash is bad, we are screwed.
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if (state.badchars.include?("\\")) or
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(state.badchars.include?("|")) or
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# We must have at least ONE of these two..
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(state.badchars.include?("x") and state.badchars.include?("0"))
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raise RuntimeError
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end
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# Now we build a string of the original payload with bad characters
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# into \0<NNN> or \x<HH>
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if (state.badchars.include?('x'))
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hex = buf.unpack('C*').collect { |c| "\\0%o" % c }.join
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else
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hex = buf.unpack('C*').collect { |c| "\\x%x" % c }.join
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end
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# Build the final output
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ret = "printf"
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# Special case: <SPACE>, try to use ${IFS}
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if (state.badchars.include?(" "))
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ret << '${IFS}'
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else
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ret << " "
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end
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ret << hex << "|sh"
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return ret
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end
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end
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