REST user authentication

Question

OK... the basic idea is to have SERVER and CLIENT physically separated (two systems).

My idea is to build a stand-alone web service (REST, XML, API-KEY) that will provide

1. Authentication: User login, logout
2. Data: Get list of products

Then I will create clients in different languages (Flash, PHP, JavaScript). Data will be served only to authenticated users.

Tipical communication for user to get list of products will be:

1. (1 request) Login / start session
2. (1 request) Get list of products
3. (1 request) Get list of products
4. ...

OK... Now the problem I have is the user session. Say we want to build Javascript client, we actually have to create PHP client that will communicate with REST (PHP knows about REST API-KEY) and will forward info to Javascript (CLIENT) right? User will login through PHP to REST server right and then request data through PHP to REST server?

Questions:

• Now how does PHP store info about opened user session on REST server?
• If my idea is bad, what is the right way of implementation?
• Alternatives?

Answer 1

You should probably use HTTP authentication for the user auth, and so not need to do any sort of session management.

Answer 2

You don't need PHP to store an API-KEY if you make your client classes in javascript smart enough to append the API-KEY (loaded when logging in) into the headers of each XmlHttpRequest your class will spawn.

Also it might be good to note that API-KEY does not necessary mean authentication key.

Answer 3

To your first question: XmlHttpRequest requests to a service will still pass along cookies, which can be used to propagate a session ID. You can even (assuming the enduser's browser supports it) mark cookies as 'HttpOnly' to reduce your XSS footprint. See Jeff Atwood's article for some detail on that.

Answer 4

A RESTful interface does not store any information about a particular user's session. It is the client's job to maintain the information about what it is doing.

Authenticate the user on every request by providing information in the Authorization HTTP header. IF this becomes a performance problem, then look at alternative solutions to optimize perf.