I have been recently going through emberjs 3.x.I have done a basic CRUD application which stores contacts and updates them.
I wanted to create users and store separate contacts for each of them.
But If I search about it in google I end up only in examples using only addons.
Is there any way to do login/signup without addons in ember?
You will struggle to find any tutorial that does everything that you are mentioning - I've not seen one yet. You can look at this tutorial Implementing Authentication with Ember Services (note: last reviewed with Ember 2.5.x), which walks you through the principles of how you might build your own authentication service. However, the purpose of this article is to build your understanding of how authentication works before encouraging you to use ember-simple-auth (highly recommended).
The ember-simple-auth docs and dummy app are a good place to start with building authentication into your app and there are numerous tutorials out there on how to use it with a variety of backends - try to find a recent tutorial if you can though.
I would also say that if you want to learn Ember in-depth then you should be prepared to use some add-ons - they are not evil or just for the weak but are there to help us all build feature-rich apps. If you are not sure how to find a good add-on, search on Ember Observer to help you identify which add-ons are highly-rated by the Ember community and well-supported, etc.
Wishing you every success with your learning.