bcoles
74 lines
1.9 KiB
Ruby
74 lines
1.9 KiB
Ruby
##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < 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' => %w[linux unix],
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'EncoderType' => Msf::Encoder::Type::CmdPosixEcho)
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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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return buf if state.badchars.empty?
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raise EncodingError if state.badchars.include?('-')
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# echo won't work without an escape character
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raise EncodingError if state.badchars.include?('\\')
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encode_block_bash_echo(state, 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?('$') || state.badchars.include?('(')
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raise EncodingError
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else
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buf = "$(/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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