Is there a way to integrate elfinder with my current user permissions system? I would need some kind of hook which would be triggered before e.g. a file gets deleted. There I should be able to abort the delete command and return some kind of response if the logged in user doesn't have enough permissions.
Closest thing I found until now is this: Connector Configuration options - Bind
But it doesn't look like I'm able to abort the current action there....
It all depends on the way you implemented the server-side connector.
For example, I have a custom connector for PHP backend which saves and returns the files / folders based on a database table. This way, I can set the read and write options for each file / folder (check the Client-Server API docs).
To answer your question, you'll need to tweak the server side connector to set the read and write attributes, like stated in this wiki page.