FormActionXssTest.php

<?php

namespace Drupal\KernelTests\Core\Form;

use Drupal\Core\Form\FormInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\KernelTests\KernelTestBase;
use Drupal\user\Entity\User;
use Symfony\Component\HttpFoundation\Request;
// cspell:ignore attribute\'close

/**
 * Ensures that a form's action attribute can't be exploited with XSS.
 *
 * @group system
 */
class FormActionXssTest extends KernelTestBase implements FormInterface {
    
    /**
     * {@inheritdoc}
     */
    protected static $modules = [
        'user',
        'system',
    ];
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'external_form_url_test';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form['something'] = [
            '#type' => 'textfield',
            '#title' => 'What do you think?',
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
    }
    
    /**
     * {@inheritdoc}
     */
    protected function setUp() : void {
        parent::setUp();
        $this->installSchema('system', [
            'sequences',
        ]);
        $this->installEntitySchema('user');
        $test_user = User::create([
            'name' => 'foobar',
            'mail' => 'foobar@example.com',
        ]);
        $test_user->save();
        \Drupal::service('current_user')->setAccount($test_user);
    }
    
    /**
     * Tests form action attribute for XSS.
     */
    public function testFormActionXss() {
        // Create a new request with a uri which attempts XSS.
        $request_stack = \Drupal::service('request_stack');
        
        /** @var \Symfony\Component\HttpFoundation\RequestStack $original_request */
        $original_request = $request_stack->pop();
        // Just request some more so there is no request left.
        $request_stack->pop();
        $request_stack->pop();
        $request = Request::create($original_request->getSchemeAndHttpHost() . '/test/"injected=\'attribute\'close="');
        $request_stack->push($request);
        $form = \Drupal::formBuilder()->getForm($this);
        $markup = \Drupal::service('renderer')->renderRoot($form);
        $this->setRawContent($markup);
        $elements = $this->xpath('//form');
        $action = isset($elements[0]['action']) ? (string) $elements[0]['action'] : FALSE;
        $injected = isset($elements[0]['injected']) ? (string) $elements[0]['injected'] : FALSE;
        $this->assertSame('/test/"injected=\'attribute\'close="', $action);
        $this->assertRaw('action="/test/&quot;injected=&#039;attribute&#039;close=&quot;"');
        $this->assertNotSame('attribute', $injected);
    }

}