insert-code-function.php

// RECAPTCHA V3

// MENU OPTIONS
function no_captcha_recaptcha_menu() {
  add_menu_page("reCapatcha Options", "reCaptcha Options", "manage_options", "recaptcha-options", "recaptcha_options_page", "", 100);
}
function recaptcha_options_page() { ?>
  <div class="wrap">
  <h1>reCaptcha Options</h1>
  <form method="post" action="options.php">
  <?php settings_fields("header_section");
  do_settings_sections("recaptcha-options");
  submit_button(); ?>  
  </form>
  </div>
<?php }

add_action("admin_menu", "no_captcha_recaptcha_menu");

function display_recaptcha_options() {
  add_settings_section("header_section", "Keys", "display_recaptcha_content", "recaptcha-options");
  add_settings_field("captcha_site_key", __("Site Key"), "display_captcha_site_key_element", "recaptcha-options", "header_section");
  add_settings_field("captcha_secret_key", __("Secret Key"), "display_captcha_secret_key_element", "recaptcha-options", "header_section");
  register_setting("header_section", "captcha_site_key");
  register_setting("header_section", "captcha_secret_key");
}
function display_recaptcha_content() {
  echo __('<p>You need to <a href="https://www.google.com/recaptcha/admin" rel="external">register you domain</a> and get keys to make this plugin work.</p>');
  echo __("Enter the key details below");
}
function display_captcha_site_key_element() { ?>
  <input type="text" name="captcha_site_key" id="captcha_site_key" value="<?php echo get_option('captcha_site_key'); ?>" />
<?php }
function display_captcha_secret_key_element() { ?>
  <input type="text" name="captcha_secret_key" id="captcha_secret_key" value="<?php echo get_option('captcha_secret_key'); ?>" />
<?php }

add_action("admin_init", "display_recaptcha_options");

//LOGIN PAGE
function login_recaptcha_script() {
  $recaptcha_key= get_option('captcha_site_key');
  wp_register_script("recaptcha_login", "https://www.google.com/recaptcha/api.js?render=". $recaptcha_key ."");
  wp_enqueue_script("recaptcha_login");
}

add_action("login_enqueue_scripts", "login_recaptcha_script");

function display_login_captcha() { ?>
<script>grecaptcha.ready(function () {              
grecaptcha.execute('<?php echo get_option('captcha_site_key'); ?>', 
{ action: 'login' }).then(function (token) {                  
var recaptchaResponse = document.getElementById('recaptchaResponse');                  
recaptchaResponse.value = token;              
  });          
});      
</script> 
<input type="hidden" name="recaptcha_response" id="recaptchaResponse">  

<?php }

add_action( "login_form", "display_login_captcha" );

function verify_login_captcha($user, $password) {
  if (isset($_POST['recaptcha_response'])) {
  $recaptcha_secret = get_option('captcha_secret_key');
  $response = wp_remote_get("https://www.google.com/recaptcha/api/siteverify?secret=". $recaptcha_secret ."&response=". $_POST['recaptcha_response']);
  $response = json_decode($response);
  if ($response->score >= 0.5) {
  return $user;
  } else {
  return new WP_Error("Captcha Invalid", __("<strong>ERROR</strong>: You are a bot"));
  } 
  } else {
  return new WP_Error("Captcha Invalid", __("<strong>ERROR</strong>: You are a bot. If not then enable JavaScript"));
  }  
}

add_filter("wp_authenticate_user", "verify_login_captcha", 10, 2);