I'm currently developing an app for my university using Ionic 2 and Firebase. So, the problem is how to restrict user from signing up unless they're using specific domain eg.(@ukm.edu.my)? It's for my university, I don't want anyone else to use this app. So, anyone without that specific email domain can't sign up for my app.
From what I've read, Firebase database rules only affect authorization. So, how to setup rules for authentication?