91 lines
2.1 KiB
Ruby
91 lines
2.1 KiB
Ruby
##
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# This module requires Metasploit: http://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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require 'msf/core'
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class Metasploit < Msf::Encoder
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Rank = GoodRanking
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def initialize
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super(
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'Name' => 'Echo Command Encoder',
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'Description' => %q{
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This encoder uses echo and backlash escapes to avoid commonly restricted characters.
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},
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'Author' => 'hdm',
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'Arch' => ARCH_CMD,
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'Platform' => 'unix',
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'EncoderType' => Msf::Encoder::Type::CmdUnixEcho)
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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 state.badchars.include?("-")
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raise EncodingError
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else
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# Without an escape character we can't escape anything, so echo
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# won't work.
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if state.badchars.include?("\\")
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raise EncodingError
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else
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buf = encode_block_bash_echo(state,buf)
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end
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end
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return buf
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end
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#
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# Uses bash's echo -ne command to hex encode the command string
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#
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def encode_block_bash_echo(state, buf)
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hex = ''
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# Can we use single quotes to enclose the echo arguments?
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if state.badchars.include?("'")
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hex = buf.unpack('C*').collect { |c| "\\\\\\x%.2x" % c }.join
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else
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hex = "'" + buf.unpack('C*').collect { |c| "\\x%.2x" % c }.join + "'"
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end
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# Are pipe characters restricted?
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if state.badchars.include?("|")
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# How about backticks?
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if state.badchars.include?("`")
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# Last ditch effort, dollar paren
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if state.badchars.include?("$") or state.badchars.include?("(")
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raise EncodingError
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else
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buf = "$(/bin/echo -ne #{hex})"
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end
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else
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buf = "`/bin/echo -ne #{hex}`"
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end
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else
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buf = "/bin/echo -ne #{hex}|sh"
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end
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# Remove spaces from the command string
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if state.badchars.include?(" ")
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buf.gsub!(/\s/, '${IFS}')
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end
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return buf
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end
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end
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