FileFieldWidgetTest.php

<?php

declare (strict_types=1);
namespace Drupal\Tests\file\Functional;

use Drupal\comment\Entity\Comment;
use Drupal\comment\Tests\CommentTestTrait;
use Drupal\Component\Serialization\Json;
use Drupal\Core\Url;
use Drupal\field\Entity\FieldConfig;
use Drupal\field\Entity\FieldStorageConfig;
use Drupal\Tests\field_ui\Traits\FieldUiTestTrait;
use Drupal\user\RoleInterface;
use Drupal\file\Entity\File;
use Drupal\user\Entity\User;
use Drupal\user\UserInterface;

/**
 * Tests the file field widget with public and private files.
 *
 * @group file
 * @group #slow
 */
class FileFieldWidgetTest extends FileFieldTestBase {
    use CommentTestTrait;
    use FieldUiTestTrait;
    
    /**
     * {@inheritdoc}
     */
    protected static $modules = [
        'comment',
        'block',
    ];
    
    /**
     * {@inheritdoc}
     */
    protected $defaultTheme = 'stark';
    
    /**
     * {@inheritdoc}
     */
    protected function setUp() : void {
        parent::setUp();
        $this->drupalPlaceBlock('system_breadcrumb_block');
    }
    
    /**
     * Creates a temporary file, for a specific user.
     *
     * @param string $data
     *   A string containing the contents of the file.
     * @param \Drupal\user\UserInterface $user
     *   The user of the file owner.
     *
     * @return \Drupal\file\FileInterface
     *   A file object, or FALSE on error.
     */
    protected function createTemporaryFile($data, ?UserInterface $user = NULL) {
        
        /** @var \Drupal\file\FileRepositoryInterface $file_repository */
        $file_repository = \Drupal::service('file.repository');
        $file = $file_repository->writeData($data, "public://");
        if ($file) {
            if ($user) {
                $file->setOwner($user);
            }
            else {
                $file->setOwner($this->adminUser);
            }
            // Change the file status to be temporary.
            $file->setTemporary();
            // Save the changes.
            $file->save();
        }
        return $file;
    }
    
    /**
     * Tests upload and remove buttons for a single-valued File field.
     */
    public function testSingleValuedWidget() : void {
        $node_storage = $this->container
            ->get('entity_type.manager')
            ->getStorage('node');
        $type_name = 'article';
        $field_name = $this->randomMachineName();
        $this->createFileField($field_name, 'node', $type_name);
        $test_file = $this->getTestFile('text');
        // Create a new node with the uploaded file and ensure it got uploaded
        // successfully.
        $nid = $this->uploadNodeFile($test_file, $field_name, $type_name);
        $node = $node_storage->loadUnchanged($nid);
        $node_file = File::load($node->{$field_name}->target_id);
        $this->assertFileExists($node_file->getFileUri());
        // Ensure the file can be downloaded.
        $this->drupalGet($node_file->createFileUrl());
        $this->assertSession()
            ->statusCodeEquals(200);
        // Ensure the edit page has a remove button instead of an upload button.
        $this->drupalGet("node/{$nid}/edit");
        $this->assertSession()
            ->buttonNotExists('Upload');
        $this->assertSession()
            ->buttonExists('Remove');
        $this->submitForm([], 'Remove');
        // Ensure the page now has an upload button instead of a remove button.
        $this->assertSession()
            ->buttonNotExists('Remove');
        $this->assertSession()
            ->buttonExists('Upload');
        // Test label has correct 'for' attribute.
        $input = $this->assertSession()
            ->fieldExists("files[{$field_name}_0]");
        $this->assertSession()
            ->elementExists('xpath', '//label[@for="' . $input->getAttribute('id') . '"]');
        // Save the node and ensure it does not have the file.
        $this->submitForm([], 'Save');
        $node = $node_storage->loadUnchanged($nid);
        $this->assertEmpty($node->{$field_name}->target_id, 'File was successfully removed from the node.');
    }
    
    /**
     * Tests upload and remove buttons for multiple multi-valued File fields.
     */
    public function testMultiValuedWidget() : void {
        $node_storage = $this->container
            ->get('entity_type.manager')
            ->getStorage('node');
        $type_name = 'article';
        // Use explicit names instead of random names for those fields, because of a
        // bug in submitForm() with multiple file uploads in one form, where the
        // order of uploads depends on the order in which the upload elements are
        // added to the $form (which, in the current implementation of
        // FileStorage::listAll(), comes down to the alphabetical order on field
        // names).
        $field_name = 'test_file_field_1';
        $field_name2 = 'test_file_field_2';
        $cardinality = 3;
        $this->createFileField($field_name, 'node', $type_name, [
            'cardinality' => $cardinality,
        ]);
        $this->createFileField($field_name2, 'node', $type_name, [
            'cardinality' => $cardinality,
        ]);
        $test_file = $this->getTestFile('text');
        // Visit the node creation form, and upload 3 files for each field. Since
        // the field has cardinality of 3, ensure the "Upload" button is displayed
        // until after the 3rd file, and after that, isn't displayed. Because
        // the last button with a given name is triggered by default, upload to the
        // second field first.
        $this->drupalGet("node/add/{$type_name}");
        foreach ([
            $field_name2,
            $field_name,
        ] as $each_field_name) {
            for ($delta = 0; $delta < 3; $delta++) {
                $edit = [
                    'files[' . $each_field_name . '_' . $delta . '][]' => \Drupal::service('file_system')->realpath($test_file->getFileUri()),
                ];
                // If the Upload button doesn't exist, submitForm() will
                // automatically fail with an assertion message.
                $this->submitForm($edit, 'Upload');
            }
        }
        $this->assertSession()
            ->buttonNotExists('Upload');
        $num_expected_remove_buttons = 6;
        foreach ([
            $field_name,
            $field_name2,
        ] as $current_field_name) {
            // How many uploaded files for the current field are remaining.
            $remaining = 3;
            // Test clicking each "Remove" button. For extra robustness, test them out
            // of sequential order. They are 0-indexed, and get renumbered after each
            // iteration, so array(1, 1, 0) means:
            // - First remove the 2nd file.
            // - Then remove what is then the 2nd file (was originally the 3rd file).
            // - Then remove the first file.
            foreach ([
                1,
                1,
                0,
            ] as $delta) {
                // Ensure we have the expected number of Remove buttons, and that they
                // are numbered sequentially.
                $buttons = $this->xpath('//input[@type="submit" and @value="Remove"]');
                $this->assertCount($num_expected_remove_buttons, $buttons, "There are {$num_expected_remove_buttons} \"Remove\" buttons displayed.");
                foreach ($buttons as $i => $button) {
                    $key = $i >= $remaining ? $i - $remaining : $i;
                    $check_field_name = $field_name2;
                    if ($current_field_name == $field_name && $i < $remaining) {
                        $check_field_name = $field_name;
                    }
                    $this->assertSame($check_field_name . '_' . $key . '_remove_button', $button->getAttribute('name'));
                }
                // "Click" the remove button (emulating either a nojs or js submission).
                $button_name = $current_field_name . '_' . $delta . '_remove_button';
                $this->getSession()
                    ->getPage()
                    ->findButton($button_name)
                    ->press();
                $num_expected_remove_buttons--;
                $remaining--;
                // Ensure an "Upload" button for the current field is displayed with the
                // correct name.
                $upload_button_name = $current_field_name . '_' . $remaining . '_upload_button';
                $button = $this->assertSession()
                    ->buttonExists($upload_button_name);
                $this->assertSame('Upload', $button->getValue());
                // Ensure only at most one button per field is displayed.
                $expected = $current_field_name == $field_name ? 1 : 2;
                $this->assertSession()
                    ->elementsCount('xpath', '//input[@type="submit" and @value="Upload"]', $expected);
            }
        }
        // Ensure the page now has no Remove buttons.
        $this->assertSession()
            ->buttonNotExists('Remove');
        // Save the node and ensure it does not have any files.
        $this->submitForm([
            'title[0][value]' => $this->randomMachineName(),
        ], 'Save');
        preg_match('/node\\/([0-9])/', $this->getUrl(), $matches);
        $nid = $matches[1];
        $node = $node_storage->loadUnchanged($nid);
        $this->assertEmpty($node->{$field_name}->target_id, 'Node was successfully saved without any files.');
        // Try to upload more files than allowed on revision.
        $upload_files_node_revision = [
            $test_file,
            $test_file,
            $test_file,
            $test_file,
        ];
        foreach ($upload_files_node_revision as $i => $file) {
            $edit['files[test_file_field_1_0][' . $i . ']'] = \Drupal::service('file_system')->realpath($test_file->getFileUri());
        }
        // @todo Replace after https://www.drupal.org/project/drupal/issues/2917885
        $this->drupalGet('node/' . $node->id() . '/edit');
        $this->assertSession()
            ->fieldExists('files[test_file_field_1_0][]');
        $submit_xpath = $this->assertSession()
            ->buttonExists('Save')
            ->getXpath();
        $client = $this->getSession()
            ->getDriver()
            ->getClient();
        $form = $client->getCrawler()
            ->filterXPath($submit_xpath)
            ->form();
        $client->request($form->getMethod(), $form->getUri(), $form->getPhpValues(), $edit);
        $node = $node_storage->loadUnchanged($nid);
        $this->assertCount($cardinality, $node->{$field_name}, 'More files than allowed could not be saved to node.');
        $upload_files_node_creation = [
            $test_file,
            $test_file,
        ];
        // Try to upload multiple files, but fewer than the maximum.
        $nid = $this->uploadNodeFiles($upload_files_node_creation, $field_name, $type_name, TRUE, []);
        $node = $node_storage->loadUnchanged($nid);
        $this->assertSameSize($upload_files_node_creation, $node->{$field_name}, 'Node was successfully saved with multiple files.');
        // Try to upload exactly the allowed number of files on revision.
        $this->uploadNodeFile($test_file, $field_name, $node->id(), 1);
        $node = $node_storage->loadUnchanged($nid);
        $this->assertCount($cardinality, $node->{$field_name}, 'Node was successfully revised to maximum number of files.');
        // Try to upload exactly the allowed number of files, new node.
        $upload_files = [
            $test_file,
            $test_file,
            $test_file,
        ];
        $nid = $this->uploadNodeFiles($upload_files, $field_name, $type_name, TRUE, []);
        $node = $node_storage->loadUnchanged($nid);
        $this->assertCount($cardinality, $node->{$field_name}, 'Node was successfully saved with maximum number of files.');
    }
    
    /**
     * Tests a file field with a "Private files" upload destination setting.
     */
    public function testPrivateFileSetting() : void {
        $node_storage = $this->container
            ->get('entity_type.manager')
            ->getStorage('node');
        // Grant the admin user required permissions.
        user_role_grant_permissions($this->adminUser->roles[0]->target_id, [
            'administer node fields',
        ]);
        $type_name = 'article';
        $field_name = $this->randomMachineName();
        $this->createFileField($field_name, 'node', $type_name);
        $field = FieldConfig::loadByName('node', $type_name, $field_name);
        $field_id = $field->id();
        $test_file = $this->getTestFile('text');
        // Change the field setting to make its files private, and upload a file.
        $edit = [
            'field_storage[subform][settings][uri_scheme]' => 'private',
        ];
        $this->drupalGet("admin/structure/types/manage/{$type_name}/fields/{$field_id}");
        $this->submitForm($edit, 'Save');
        $nid = $this->uploadNodeFile($test_file, $field_name, $type_name);
        $node = $node_storage->loadUnchanged($nid);
        $node_file = File::load($node->{$field_name}->target_id);
        $this->assertFileExists($node_file->getFileUri());
        // Ensure the private file is available to the user who uploaded it.
        $this->drupalGet($node_file->createFileUrl());
        $this->assertSession()
            ->statusCodeEquals(200);
        // Ensure we can't change 'uri_scheme' field settings while there are some
        // entities with uploaded files.
        $this->drupalGet("admin/structure/types/manage/{$type_name}/fields/{$field_id}");
        $this->assertSession()
            ->fieldDisabled("edit-field-storage-subform-settings-uri-scheme-public");
        // Delete node and confirm that setting could be changed.
        $node->delete();
        $this->drupalGet("admin/structure/types/manage/{$type_name}/fields/{$field_id}");
        $this->assertSession()
            ->fieldEnabled("edit-field-storage-subform-settings-uri-scheme-public");
    }
    
    /**
     * Tests that download restrictions on private files work on comments.
     */
    public function testPrivateFileComment() : void {
        $user = $this->drupalCreateUser([
            'access comments',
        ]);
        // Grant the admin user required comment permissions.
        $roles = $this->adminUser
            ->getRoles();
        user_role_grant_permissions($roles[1], [
            'administer comment fields',
            'administer comments',
        ]);
        // Revoke access comments permission from anon user, grant post to
        // authenticated.
        user_role_revoke_permissions(RoleInterface::ANONYMOUS_ID, [
            'access comments',
        ]);
        user_role_grant_permissions(RoleInterface::AUTHENTICATED_ID, [
            'post comments',
            'skip comment approval',
        ]);
        // Create a new field.
        $this->addDefaultCommentField('node', 'article');
        $name = $this->randomMachineName();
        $label = $this->randomMachineName();
        $storage_edit = [
            'settings[uri_scheme]' => 'private',
        ];
        $this->fieldUIAddNewField('admin/structure/comment/manage/comment', $name, $label, 'file', $storage_edit);
        // Manually clear cache on the tester side.
        \Drupal::service('entity_field.manager')->clearCachedFieldDefinitions();
        // Create node.
        $edit = [
            'title[0][value]' => $this->randomMachineName(),
        ];
        $this->drupalGet('node/add/article');
        $this->submitForm($edit, 'Save');
        $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
        // Add a comment with a file.
        $text_file = $this->getTestFile('text');
        $edit = [
            'files[field_' . $name . '_' . 0 . ']' => \Drupal::service('file_system')->realpath($text_file->getFileUri()),
            'comment_body[0][value]' => $comment_body = $this->randomMachineName(),
        ];
        $this->drupalGet('node/' . $node->id());
        $this->submitForm($edit, 'Save');
        // Get the comment ID.
        preg_match('/comment-([0-9]+)/', $this->getUrl(), $matches);
        $cid = $matches[1];
        // Log in as normal user.
        $this->drupalLogin($user);
        $comment = Comment::load($cid);
        $comment_file = $comment->{'field_' . $name}->entity;
        $this->assertFileExists($comment_file->getFileUri());
        // Test authenticated file download.
        $url = $comment_file->createFileUrl();
        $this->assertNotNull($url, 'Confirmed that the URL is valid');
        $this->drupalGet($comment_file->createFileUrl());
        $this->assertSession()
            ->statusCodeEquals(200);
        // Ensure that the anonymous user cannot download the file.
        $this->drupalLogout();
        $this->drupalGet($comment_file->createFileUrl());
        $this->assertSession()
            ->statusCodeEquals(403);
        // Unpublishes node.
        $this->drupalLogin($this->adminUser);
        $edit = [
            'status[value]' => FALSE,
        ];
        $this->drupalGet('node/' . $node->id() . '/edit');
        $this->submitForm($edit, 'Save');
        // Ensures normal user can no longer download the file.
        $this->drupalLogin($user);
        $this->drupalGet($comment_file->createFileUrl());
        $this->assertSession()
            ->statusCodeEquals(403);
    }
    
    /**
     * Tests validation with the Upload button.
     */
    public function testWidgetValidation() : void {
        $type_name = 'article';
        $field_name = $this->randomMachineName();
        $this->createFileField($field_name, 'node', $type_name);
        $this->updateFileField($field_name, $type_name, [
            'file_extensions' => 'txt',
        ]);
        $type = 'nojs';
        // Create node and prepare files for upload.
        $node = $this->drupalCreateNode([
            'type' => 'article',
        ]);
        $nid = $node->id();
        $this->drupalGet("node/{$nid}/edit");
        $test_file_text = $this->getTestFile('text');
        $test_file_image = $this->getTestFile('image');
        $name = 'files[' . $field_name . '_0]';
        // Upload file with incorrect extension, check for validation error.
        $edit[$name] = \Drupal::service('file_system')->realpath($test_file_image->getFileUri());
        $this->submitForm($edit, 'Upload');
        $this->assertSession()
            ->pageTextContains("Only files with the following extensions are allowed: txt.");
        // Upload file with correct extension, check that error message is removed.
        $edit[$name] = \Drupal::service('file_system')->realpath($test_file_text->getFileUri());
        $this->submitForm($edit, 'Upload');
        $this->assertSession()
            ->pageTextNotContains("Only files with the following extensions are allowed: txt.");
    }
    
    /**
     * Tests file widget element.
     */
    public function testWidgetElement() : void {
        $field_name = $this->randomMachineName();
        $html_name = str_replace('_', '-', $field_name);
        $this->createFileField($field_name, 'node', 'article', [
            'cardinality' => FieldStorageConfig::CARDINALITY_UNLIMITED,
        ]);
        $file = $this->getTestFile('text');
        $xpath = "//details[@data-drupal-selector='edit-{$html_name}']/table";
        $this->drupalGet('node/add/article');
        // If the field has no item, the table should not be visible.
        $this->assertSession()
            ->elementNotExists('xpath', $xpath);
        // Upload a file.
        $edit['files[' . $field_name . '_0][]'] = $this->container
            ->get('file_system')
            ->realpath($file->getFileUri());
        $this->submitForm($edit, "{$field_name}_0_upload_button");
        // If the field has at least one item, the table should be visible.
        $this->assertSession()
            ->elementsCount('xpath', $xpath, 1);
        // Test for AJAX error when using progress bar on file field widget.
        $http_client = $this->getHttpClient();
        $key = $this->randomMachineName();
        $post_request = $http_client->request('POST', $this->buildUrl('file/progress/' . $key), [
            'headers' => [
                'Accept' => 'application/json',
                'Content-Type' => 'application/x-www-form-urlencoded',
            ],
            'http_errors' => FALSE,
        ]);
        $this->assertNotEquals(500, $post_request->getStatusCode());
        $body = Json::decode($post_request->getBody());
        $this->assertStringContainsString('Starting upload...', $body['message']);
    }
    
    /**
     * Tests exploiting the temporary file removal of another user using fid.
     */
    public function testTemporaryFileRemovalExploit() : void {
        // Create a victim user.
        $victim_user = $this->drupalCreateUser();
        // Create an attacker user.
        $attacker_user = $this->drupalCreateUser([
            'access content',
            'create article content',
            'edit any article content',
        ]);
        // Log in as the attacker user.
        $this->drupalLogin($attacker_user);
        // Perform tests using the newly created users.
        $this->doTestTemporaryFileRemovalExploit($victim_user, $attacker_user);
    }
    
    /**
     * Tests exploiting the temporary file removal for anonymous users using fid.
     */
    public function testTemporaryFileRemovalExploitAnonymous() : void {
        // Set up an anonymous victim user.
        $victim_user = User::getAnonymousUser();
        // Set up an anonymous attacker user.
        $attacker_user = User::getAnonymousUser();
        // Set up permissions for anonymous attacker user.
        user_role_change_permissions(RoleInterface::ANONYMOUS_ID, [
            'access content' => TRUE,
            'create article content' => TRUE,
            'edit any article content' => TRUE,
        ]);
        // Log out so as to be the anonymous attacker user.
        $this->drupalLogout();
        // Perform tests using the newly set up anonymous users.
        $this->doTestTemporaryFileRemovalExploit($victim_user, $attacker_user);
    }
    
    /**
     * Tests maximum upload file size validation.
     */
    public function testMaximumUploadFileSizeValidation() : void {
        // Grant the admin user required permissions.
        user_role_grant_permissions($this->adminUser->roles[0]->target_id, [
            'administer node fields',
        ]);
        $type_name = 'article';
        $field_name = $this->randomMachineName();
        $this->createFileField($field_name, 'node', $type_name);
        
        /** @var \Drupal\Field\FieldConfigInterface $field */
        $field = FieldConfig::loadByName('node', $type_name, $field_name);
        $field_id = $field->id();
        $this->drupalGet("admin/structure/types/manage/{$type_name}/fields/{$field_id}");
        // Tests that form validation trims the user input.
        $edit = [
            'settings[max_filesize]' => ' 5.1 megabytes ',
        ];
        $this->submitForm($edit, 'Save settings');
        $this->assertSession()
            ->pageTextContains('Saved ' . $field_name . ' configuration.');
        // Reload the field config to check for the saved value.
        
        /** @var \Drupal\Field\FieldConfigInterface $field */
        $field = FieldConfig::loadByName('node', $type_name, $field_name);
        $settings = $field->getSettings();
        $this->assertEquals('5.1 megabytes', $settings['max_filesize'], 'The max filesize value had been trimmed on save.');
    }
    
    /**
     * Tests configuring file field's allowed file extensions setting.
     */
    public function testFileExtensionsSetting() : void {
        // Grant the admin user required permissions.
        user_role_grant_permissions($this->adminUser->roles[0]->target_id, [
            'administer node fields',
        ]);
        $type_name = 'article';
        $field_name = $this->randomMachineName();
        $this->createFileField($field_name, 'node', $type_name);
        $field = FieldConfig::loadByName('node', $type_name, $field_name);
        $field_id = $field->id();
        // By default allowing .php files without .txt is not permitted.
        $this->drupalGet("admin/structure/types/manage/{$type_name}/fields/{$field_id}");
        $edit = [
            'settings[file_extensions]' => 'jpg php',
        ];
        $this->submitForm($edit, 'Save settings');
        $this->assertSession()
            ->pageTextContains('Add txt to the list of allowed extensions to securely upload files with a php extension. The txt extension will then be added automatically.');
        // Test allowing .php and .txt.
        $edit = [
            'settings[file_extensions]' => 'jpg php txt',
        ];
        $this->submitForm($edit, 'Save settings');
        $this->assertSession()
            ->pageTextContains('Saved ' . $field_name . ' configuration.');
        // If the system is configured to allow insecure uploads, .txt is not
        // required when allowing .php.
        $this->config('system.file')
            ->set('allow_insecure_uploads', TRUE)
            ->save();
        $this->drupalGet("admin/structure/types/manage/{$type_name}/fields/{$field_id}");
        $edit = [
            'settings[file_extensions]' => 'jpg php',
        ];
        $this->submitForm($edit, 'Save settings');
        $this->assertSession()
            ->pageTextContains('Saved ' . $field_name . ' configuration.');
        // Check that a file extension with an underscore can be configured.
        $edit = [
            'settings[file_extensions]' => 'x_t x.t xt x_y_t',
        ];
        $this->drupalGet("admin/structure/types/manage/{$type_name}/fields/{$field_id}");
        $this->submitForm($edit, 'Save settings');
        $field = FieldConfig::loadByName('node', $type_name, $field_name);
        $this->assertEquals('x_t x.t xt x_y_t', $field->getSetting('file_extensions'));
        // Check that a file field with an invalid value in allowed extensions
        // property throws an error message.
        $invalid_extensions = [
            'x_.t',
            'x._t',
            'xt_',
            'x__t',
            '_xt',
        ];
        foreach ($invalid_extensions as $value) {
            $edit = [
                'settings[file_extensions]' => $value,
            ];
            $this->drupalGet("admin/structure/types/manage/{$type_name}/fields/{$field_id}");
            $this->submitForm($edit, 'Save settings');
            $this->assertSession()
                ->pageTextContains("The list of allowed extensions is not valid. Allowed characters are a-z, 0-9, '.', and '_'. The first and last characters cannot be '.' or '_', and these two characters cannot appear next to each other. Separate extensions with a comma or space.");
        }
    }
    
    /**
     * Helper for testing exploiting the temporary file removal using fid.
     *
     * @param \Drupal\user\UserInterface $victim_user
     *   The victim user.
     * @param \Drupal\user\UserInterface $attacker_user
     *   The attacker user.
     */
    protected function doTestTemporaryFileRemovalExploit(UserInterface $victim_user, UserInterface $attacker_user) {
        $type_name = 'article';
        $field_name = 'test_file_field';
        $this->createFileField($field_name, 'node', $type_name);
        $test_file = $this->getTestFile('text');
        $type = 'no-js';
        // Create a temporary file owned by the victim user. This will be as if
        // they had uploaded the file, but not saved the node they were editing
        // or creating.
        $victim_tmp_file = $this->createTemporaryFile('some text', $victim_user);
        $victim_tmp_file = File::load($victim_tmp_file->id());
        $this->assertTrue($victim_tmp_file->isTemporary(), 'New file saved to disk is temporary.');
        $this->assertNotEmpty($victim_tmp_file->id(), 'New file has an fid.');
        $this->assertEquals($victim_user->id(), $victim_tmp_file->getOwnerId(), 'New file belongs to the victim.');
        // Have attacker create a new node with a different uploaded file and
        // ensure it got uploaded successfully.
        $edit = [
            'title[0][value]' => $type . '-title',
        ];
        // Attach a file to a node.
        $edit['files[' . $field_name . '_0]'] = $this->container
            ->get('file_system')
            ->realpath($test_file->getFileUri());
        $this->drupalGet(Url::fromRoute('node.add', [
            'node_type' => $type_name,
        ]));
        $this->submitForm($edit, 'Save');
        $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
        
        /** @var \Drupal\file\FileInterface $node_file */
        $node_file = File::load($node->{$field_name}->target_id);
        $this->assertFileExists($node_file->getFileUri());
        $this->assertEquals($attacker_user->id(), $node_file->getOwnerId(), 'New file belongs to the attacker.');
        // Ensure the file can be downloaded.
        $this->drupalGet($node_file->createFileUrl());
        $this->assertSession()
            ->statusCodeEquals(200);
        // "Click" the remove button (emulating either a nojs or js submission).
        // In this POST request, the attacker "guesses" the fid of the victim's
        // temporary file and uses that to remove this file.
        $this->drupalGet($node->toUrl('edit-form'));
        $file_id_field = $this->assertSession()
            ->hiddenFieldExists($field_name . '[0][fids]');
        $file_id_field->setValue((string) $victim_tmp_file->id());
        $this->submitForm([], 'Remove');
        // The victim's temporary file should not be removed by the attacker's
        // POST request.
        $this->assertFileExists($victim_tmp_file->getFileUri());
    }

}