T5 Unique Log-in Field

t5-unique-login-field.php

<?php  # -*- coding: utf-8 -*-
namespace Unique_Login;
/**
 * Plugin Name: T5 Unique Log-in Field
 * Description: Adds a checkbox with a unique name to the login form to prevent scripted log-in attempts.
 * Plugin URI:
 * Version:     2013.06.14
 * Author:      Thomas Scholz
 * Author URI:  http://toscho.de
 * Licence:     MIT
 * License URI: http://opensource.org/licenses/MIT
 */

\add_action(
	'login_init',
	array ( 'Unique_Login\Unique_Login_Controller', 'init' ),
	1
);

/**
 * Front class to create the needed instances.
 */
class Unique_Login_Controller
{
	/**
	 * Callback for add_action(). Creates a new instance.
	 *
	 * @wp-hook login_init
	 */
	public function init()
	{
		return new self;
	}

	/**
	 * Set up objects, register footer action callback.
	 *
	 * @wp-hook login_init
	 */
	protected function __construct()
	{
		if ( ! empty ( $GLOBALS['interim_login'] ) )
			return;

		$data = new Unique_Login_Data;
		$form = new Unique_Login_Form( $data );
		\add_action( 'login_footer', array ( $form, 'run' ) );

		if ( 'POST' === $_SERVER[ 'REQUEST_METHOD' ] )
		{
			$check = new Unique_Login_Check( $data );
			$check->run();
		}
	}
}

/**
 * Create a unique string for validation.
 *
 * @wp-hook login_init
 */
class Unique_Login_Data
{
	/**
	 * Unique string to check for.
	 *
	 * @type string
	 */
	public $unique;

	/**
	 * Create public unique string.
	 */
	public function __construct()
	{
		if ( defined( 'LOGGED_IN_SALT' ) )
			$salt = LOGGED_IN_SALT;
		else
			$salt = filemtime( __FILE__ );

		$this->unique = md5( $_SERVER[ 'HTTP_HOST' ] . $salt );
	}
}

/**
 * Base structure for output.
 */
abstract class Unique_Login_View
{
	/**
	 * Instance of Unique_Login_Data
	 *
	 * @type Unique_Login_Data
	 */
	protected $data;

	/**
	 * Set $data.
	 *
	 * @param Unique_Login_Data $data
	 */
	public function __construct( Unique_Login_Data $data )
	{
		$this->data = $data;
	}

	/**
	 * Do the actual work.
	 *
	 * @return void
	 */
	abstract public function run();
}

/**
 * Check the POST data for valid clicked checkbox.
 *
 */
class Unique_Login_Check extends Unique_Login_View
{
	/**
	 * Check POST request for clicked checkbox.
	 *
	 * @wp-hook login_init
	 * @see Unique_Login.Unique_Login_View::run()
	 */
	public function run()
	{
		if ( ! isset ( $_POST[ 'log' ] ) )
			return;

		if ( empty ( $_POST[ 'name_' . $this->data->unique ] )
			or 'on' !== strtolower( $_POST[ 'name_' . $this->data->unique ] )
		)
		{
			header( 'Location: http://localhost' );
			exit;
		}
	}
}

/**
 * Adds a checkbox with a unique name to the login form.
 */
class Unique_Login_Form extends Unique_Login_View
{
	/**
	 * Create the checkbox and add it to the form.
	 *
	 * @wp-hook login_footer
	 * @see Unique_Login.Unique_Login_View::run()
	 */
	public function run()
	{
		$u    = $this->data->unique;
		$html = "<p class='forgetmenot' style='clear:both;float:none'><label for='id_$u'>"
			. "<input type='checkbox' name='name_$u' id='id_$u'> I am human</label></p>";
		?>
<script>var p = document.createElement( 'p' );
p.innerHTML = "<?php echo $html; ?>";
document.getElementById( 'loginform' ).appendChild( p );</script>
		<?php
	}
}