composer ownership permissions

I was pleased in starting with the composer approach to drupal installation and dependency managing. Though I'm still facing something contentious: composer is launched by a user with his shell but files are originally though as if they have to be managed by the user with no shell related to the httpd process, at least as far as disk writes are concerned - i.e. possibly file uploads... I wonder what is the best practice someone else before might have already found in order to make composer usage compatible with the usage of the drupal administration interface?

Thanks in advance!

Andrea