Here is the scenario.
We have a product built on linux systems and the data is available through REST API. The web application which is built on JAVA is also hosted on the same environment.
Few of our clients use SharePoint. SSO to our web application(on linux) is implemented through ADFS from the client's network. So the services and applications are accessible seamlessly.
There is a necessity to build an APP for SharePoint( SP hosted or provider hosted) to use the REST API's to pull the data. Can a SharePoint app make calls to the REST API while authorizing the user who is already logged on to SharePoint. I know SP Hosted APP has limitations in calling external REST APIs which require authentication. Can provider hosted apps work in this scenario?