public function ImageStyleDownloadController::deliver

Generates a derivative, given a style and image path.

After generating an image, transfer it to the requesting agent.

Parameters

\Symfony\Component\HttpFoundation\Request $request: The request object.

string $scheme: The file scheme, defaults to 'private'.

\Drupal\image\ImageStyleInterface $image_style: The image style to deliver.

Return value

\Symfony\Component\HttpFoundation\BinaryFileResponse|\Symfony\Component\HttpFoundation\Response The transferred file as response or some error response.

Throws

\Symfony\Component\HttpKernel\Exception\NotFoundHttpException Thrown when the file request is invalid.

\Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException Thrown when the user does not have access to the file.

\Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException Thrown when the file is still being generated.

File

core/modules/image/src/Controller/ImageStyleDownloadController.php, line 95

Class

ImageStyleDownloadController

Defines a controller to serve image styles.

Namespace

Code

public function deliver(Request $request, $scheme, ImageStyleInterface $image_style) {
  $target = $request->query
    ->get('file');
  $image_uri = $scheme . '://' . $target;

  // Check that the style is defined, the scheme is valid, and the image
  // derivative token is valid. Sites which require image derivatives to be
  // generated without a token can set the
  // 'image.settings:allow_insecure_derivatives' configuration to TRUE to
  // bypass the latter check, but this will increase the site's vulnerability
  // to denial-of-service attacks. To prevent this variable from leaving the
  // site vulnerable to the most serious attacks, a token is always required
  // when a derivative of a style is requested.
  // The $target variable for a derivative of a style has
  // styles/<style_name>/... as structure, so we check if the $target variable
  // starts with styles/.
  $valid = !empty($image_style) && $this->streamWrapperManager
    ->isValidScheme($scheme);
  if (!$this
    ->config('image.settings')
    ->get('allow_insecure_derivatives') || strpos(ltrim($target, '\\/'), 'styles/') === 0) {
    $valid &= hash_equals($image_style
      ->getPathToken($image_uri), $request->query
      ->get(IMAGE_DERIVATIVE_TOKEN, ''));
  }
  if (!$valid) {

    // Return a 404 (Page Not Found) rather than a 403 (Access Denied) as the
    // image token is for DDoS protection rather than access checking. 404s
    // are more likely to be cached (e.g. at a proxy) which enhances
    // protection from DDoS.
    throw new NotFoundHttpException();
  }
  $derivative_uri = $image_style
    ->buildUri($image_uri);
  $headers = [];

  // If using the private scheme, let other modules provide headers and
  // control access to the file.
  if ($scheme == 'private') {
    $headers = $this
      ->moduleHandler()
      ->invokeAll('file_download', [
      $image_uri,
    ]);
    if (in_array(-1, $headers) || empty($headers)) {
      throw new AccessDeniedHttpException();
    }
  }

  // Don't try to generate file if source is missing.
  if (!file_exists($image_uri)) {

    // If the image style converted the extension, it has been added to the
    // original file, resulting in filenames like image.png.jpeg. So to find
    // the actual source image, we remove the extension and check if that
    // image exists.
    $path_info = pathinfo($image_uri);
    $converted_image_uri = $path_info['dirname'] . DIRECTORY_SEPARATOR . $path_info['filename'];
    if (!file_exists($converted_image_uri)) {
      $this->logger
        ->notice('Source image at %source_image_path not found while trying to generate derivative image at %derivative_path.', [
        '%source_image_path' => $image_uri,
        '%derivative_path' => $derivative_uri,
      ]);
      return new Response($this
        ->t('Error generating image, missing source file.'), 404);
    }
    else {

      // The converted file does exist, use it as the source.
      $image_uri = $converted_image_uri;
    }
  }

  // Don't start generating the image if the derivative already exists or if
  // generation is in progress in another thread.
  if (!file_exists($derivative_uri)) {
    $lock_name = 'image_style_deliver:' . $image_style
      ->id() . ':' . Crypt::hashBase64($image_uri);
    $lock_acquired = $this->lock
      ->acquire($lock_name);
    if (!$lock_acquired) {

      // Tell client to retry again in 3 seconds. Currently no browsers are
      // known to support Retry-After.
      throw new ServiceUnavailableHttpException(3, 'Image generation in progress. Try again shortly.');
    }
  }

  // Try to generate the image, unless another thread just did it while we
  // were acquiring the lock.
  $success = file_exists($derivative_uri) || $image_style
    ->createDerivative($image_uri, $derivative_uri);
  if (!empty($lock_acquired)) {
    $this->lock
      ->release($lock_name);
  }
  if ($success) {
    $image = $this->imageFactory
      ->get($derivative_uri);
    $uri = $image
      ->getSource();
    $headers += [
      'Content-Type' => $image
        ->getMimeType(),
      'Content-Length' => $image
        ->getFileSize(),
    ];

    // \Drupal\Core\EventSubscriber\FinishResponseSubscriber::onRespond()
    // sets response as not cacheable if the Cache-Control header is not
    // already modified. We pass in FALSE for non-private schemes for the
    // $public parameter to make sure we don't change the headers.
    return new BinaryFileResponse($uri, 200, $headers, $scheme !== 'private');
  }
  else {
    $this->logger
      ->notice('Unable to generate the derived image located at %path.', [
      '%path' => $derivative_uri,
    ]);
    return new Response($this
      ->t('Error generating image.'), 500);
  }
}