Different REST resource content based on user viewing privileges

Question

I want to provide different answers to the same question for different users, based on the access rights. I read this question:

Excluding private data in RESTful respons

Answer 1

I agree that the other solution doesn't seem right. It makes the URL structure complicated and more difficult to find the resource. However, if you did REST properly, it shouldn't matter what the URL for the resource is as the server controls it (and is free to relocate it as it sees fit). If your client is really "REST", it would discover the resources it needed through prior negotiation with the server. So the path truly would not matter on the client. I don't like it because its confusing to use - not because of some violation of REST principles.

But that probably doesn't answer your question - What you didn't mention is your security setup - presumably you are a passing a session token with the request as part of the request header. So your back-end processing should have the ability to tie it to particular set of security constraints. From there, you form the list with whatever business logic you need and return a limited resource based on the user's security tied to the session.

For the algorithm itself, one usually implements a least or most restrictive type algorithm that merges the allowable data into a response (very similar to java realms or Microsoft's user security model).

If the data is structured differently for the restricted/non-restricted case, you could create two different representations of the data and return which ever one the user was authorized to see. The client should be asking for the accepted mime response types anyway, and it would just provide different answers based on the session security in the request header. Alternatively, you could provide optional elements with the representations and fill out the appropriate one base on authorization (although this is a little hack-ee in my opinion).