Protecting the content of public/ in a Rails app

Question

I'm maintaining a Rails app that has content in the public/ folder that will now need to be protected by a login. We're considering moving those folders of files into a path outside of public/ and writing a Rails controller to serve up the content.

Before we begin writing this, I was curious if anyone else has ran into this sort of problem? I looked for some gems / plugins that might already do this but didn't find anything. Has anyone created a gem for this?

Answer 1

I've done this on a site where people pay to download certain files, and the files are stored in RAILS_ROOT/private. The first thing to know is that you want the web server to handle sending the file, otherwise your app will be held up transmitting large files and this will quickly bring your site to a halt if you have any kind of download volume. So, if you need to check authorization in a controller, then you also need a way to pass control of the download back to the web server. The best way of doing this (that I know of) is the X-Sendfile header, which is supported by Nginx, Apache (with module), and others. With X-Sendfile configured, when your web server receives a X-Sendfile header from your app, it takes over sending the file to the client.

Once you have X-Sendfile working for your web server, a private controller method like this is helpful:

##
# Send a protected file using the web server (via the x-sendfile header).
# Takes the absolute file system path to the file and, optionally, a MIME type.
#
def send_file(filepath, options = {})
  options[:content_type] ||= "application/force-download"
  response.headers['Content-Type'] = options[:content_type]
  response.headers['Content-Disposition'] = "attachment; filename=\"#{File.basename(filepath)}\""
  response.headers['X-Sendfile'] = filepath
  response.headers['Content-length'] = File.size(filepath)
  render :nothing => true
end

Then your controller action could look something like this:

##
# Private file download: check permission first.
#
def download
  product = Product.find_by_filename!(params[:filename])
  if current_user.has_bought?(product) or current_user.is_superuser?
    if File.exist?(path = product.filepath)
      send_file path, :content_type => "application/pdf"
    else
      not_found
    end
  else
    not_authorized
  end
end

Obviously your authorization method will vary and you'll need to change the headers if you're offering files other than PDFs or you want the file to be viewed in the browser (get rid of application/force-download content type).