SharePoint - passing info to external application

[Patman]

Hi All:

 

I wonder if anyone has implemented this.

 

We have SharePoint and we have developed some nice tools in it. We have developed other tools outside of SharePoint, but they require the user to authenticate against AD.

 

I want the user to be able to click a link in SharePoint and be sent to the external applications, but not have to explicitly log in. I would like the external application to be able to extract the username. That external application can then determine if the user is authorised to use the application.

 

We have on premises SharePoint that we want to move to the cloud. I see lots of documentation regarding using REST to put apps in O365 or using federated services for accessing other applications or fairly complicated OAuth discussions, but I think the above is simpler. But it might not be possible.

 

Am I over-simplifying? Over-thinking?

 

Has anyone done this?

 

Thanks in advance.

 

Patman