Correct HTTP status code when resource is available but not accessible because of permissions

I am building a RESTful protocol for Dynamic Carpooling applic开发者_StackOverflow中文版ations, for my Computer Science thesis.

In the Protocol I also have to formally specify the HTTP status code for each operation. I've got this "privacy related" problem. Suppose the following:

GET /api/persons/angela/location

Retrieves the current position of user "angela". It is obvious that not everybody should be able to obtain a result. Only angela itself and a possible driver that is going to pick her should be able to know it.

I can not decide whether to return a 404 Not Found or a 401 Forbidden here.

Any hints? What would be the best one and why?

---

According to Wikipedia (and RFC 2616), a 401 code is used when a page exists but requires authentication; 403 is for a page where authenticating won't change anything. (In the wild, 403 usually means the permissions on something are wrong, whereas a 401 will prompt the user for a username/password). 404 is for where the document simply doesn't exist.

In your case, it seems like 401 is the most appropriate code, since there is some way of authenticating the users who DO have access to the page.

---

If authorization credentials are provided in the request and the requester does not have permissions to access this resource then you should return 403.

If no authorization credentials are provided in the request then you should return 401.

---

Definitely NOT 404. 404 is just Not Found.
401 is access denied.
403 is forbidden.

I would go with 401

---

To me I will use 400 Bad request.
Because my application will not go unaccessable resources in programmatically.
Filtering users permission and hide unaccessable resources is good user experience in my opinion. If my server got unaccessable request which means some person trying to do something.
That is why I choose 400 - Bad request in my applications.