3

I have a content type with a (private) file field. Content is protected by a node access module.

I would like to log (in a particular way) when a user is about to download a file.

hook_file_download looks like it will do the trick, but on the other hand, its stated purpose is to "control access". I'm letting Drupal Core control access; I just want to log a (successful) download.

Is there a better hook to do this with?

  • 3
    there isn't a D7 version out there, but drupal.org/project/filefield_stats is a great module for D6, and maybe some of its code could be of use to you if you are already writing a module... – Jimajamma Apr 5 '12 at 17:45
  • yeah, good tip, thanks. Basically that module makes a page callback function to deal with it. Had hoped there was a more graceful way to compliment the D7 private/'managed' files API – artfulrobot Apr 5 '12 at 19:07
  • Just by the way, for public files it could be easily done at webserver level. Sadly won't work for private. – Mołot Sep 8 '15 at 21:46
2

hook_file_download() is invoked in two occasions:

  • When Drupal is verifying the users have access to the file they are trying to download

    function file_download_access($uri) {
      return count(file_download_headers($uri)) > 0;
    }
    
  • When Drupal is returning the headers for the file to download (and then the data for the file to download)

    function file_download() {
      // Merge remainder of arguments from GET['q'], into relative file path.
      $args = func_get_args();
      $scheme = array_shift($args);
      $target = implode('/', $args);
      $uri = $scheme . '://' . $target;
      if (file_stream_wrapper_valid_scheme($scheme) && file_exists($uri)) {
        $headers = file_download_headers($uri);
        if (count($headers)) {
          file_transfer($uri, $headers);
        }
        drupal_access_denied();
      }
      else {
        drupal_not_found();
      }
      drupal_exit();
    }
    

In both the cases, the function invoking the hook is file_download_headers().

function file_download_headers($uri) {
  // Let other modules provide headers and control access to the file.
  // module_invoke_all() uses array_merge_recursive() which merges header
  // values into a new array. To avoid that and allow modules to override
  // headers instead, use array_merge() to merge the returned arrays.
  $headers = array();
  foreach (module_implements('file_download') as $module) {
    $function = $module . '_file_download';
    $result = $function($uri);
    if ($result == -1) {
      // Throw away the headers received so far.
      $headers = array();
      break;
    }
    if (isset($result) && is_array($result)) {
      $headers = array_merge($headers, $result);
    }
  }
  return $headers;
}

Watching the Drupal code, I cannot assure the hook is always called twice in row, during the same page request; if it were so, you could take the necessary action when the hook is invoked for the second time.

I would rather change the callbacks for $directory_path . '/styles/%image_style' (where $directory_path contains the value returned from file_stream_wrapper_get_instance_by_scheme('public')->getDirectoryPath()), system/files/styles/%image_style, system/files, and system/temporary to verify when a file is going to be downloaded, and log what happening.

This is not going to change in Drupal 8, as it doesn't split hook_file_download() in two hooks.

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