I've been asked a tricky question. Here is the schema. A user have access to a custom web interface, no SharePoint. He wants, through this interface, to access data on SharePoint. He has no account on SharePoint 2013. From there, via the API, a service account will go on SharePoint and read or modify the data for the user.
The question is : can a person log into SharePoint with that service account ? Because we don't want that.
Thank you, and if I'm not clear, don't hesitate to say so.