controlador-descarga/controllers/LoginController.php

<?php

namespace app\controllers;

use app\models\Login;
use Yii;

class LoginController extends \yii\web\Controller {

  public function beforeAction($action) {
    Yii::$app->getRequest()->enableCsrfValidation = false;
    return parent::beforeAction($action);
  }

  public function actionIndex() {
    if(\Yii::$app->getRequest()->isPost) {
      $model = new Login();
      if ($model->load(Yii::$app->request->getBodyParams(), '') && $model->login()) {
        \Yii::$app->getResponse()->format = \yii\web\Response::FORMAT_JSON;
        return ['success' => true];
      }

      return ['success' => false, 'errors' => $model->getErrors()];
    }

    if(!\Yii::$app->user->isGuest) {
      return $this->redirect('inicio');
    }

    return $this->render('index');
  }

}