/lib/Cake/Controller/Component/Auth/FormAuthenticate.php

<?php
/**
 * PHP 5
 *
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright 2005-2011, Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright 2005-2011, Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
 */

App::uses('BaseAuthenticate', 'Controller/Component/Auth');

/**
 * An authentication adapter for AuthComponent.  Provides the ability to authenticate using POST
 * data.  Can be used by configuring AuthComponent to use it via the AuthComponent::$authenticate setting.
 *
 * {{{
 *	$this->Auth->authenticate = array(
 *		'Form' => array(
 *			'scope' => array('User.active' => 1)
 *		)
 *	)
 * }}}
 *
 * When configuring FormAuthenticate you can pass in settings to which fields, model and additional conditions
 * are used. See FormAuthenticate::$settings for more information.
 *
 * @package       Cake.Controller.Component.Auth
 * @since 2.0
 * @see AuthComponent::$authenticate
 */
class FormAuthenticate extends BaseAuthenticate {

/**
 * Authenticates the identity contained in a request.  Will use the `settings.userModel`, and `settings.fields`
 * to find POST data that is used to find a matching record in the `settings.userModel`.  Will return false if
 * there is no post data, either username or password is missing, of if the scope conditions have not been met.
 *
 * @param CakeRequest $request The request that contains login information.
 * @param CakeResponse $response Unused response object.
 * @return mixed.  False on login failure.  An array of User data on success.
 */
	public function authenticate(CakeRequest $request, CakeResponse $response) {
		$userModel = $this->settings['userModel'];
		list($plugin, $model) = pluginSplit($userModel);

		$fields = $this->settings['fields'];
		if (empty($request->data[$model])) {
			return false;
		}
		if (
			empty($request->data[$model][$fields['username']]) ||
			empty($request->data[$model][$fields['password']])
		) {
			return false;
		}
		return $this->_findUser(
			$request->data[$model][$fields['username']],
			$request->data[$model][$fields['password']]
		);
	}

}