java - What is the point of Authentication tokens on REST services

Question

What is the value of using a authentication token when using a REST webservice instead of sending a username, password over HTTPS/Encryption each time you make a request?

I understand that for instance OAUTH has some benefits cause you don't need to give away your password to 3rd parties, you can pass a token to trusted 3rd parties whom you dont want to share the username/password..etc

But other than this special benefits above which I certainly dont need in my case, why would I use tokens instead of sending username/password everytime.

This might be to make life easy for client, and it does not have to send the username/password everytime. Well ok but then now client has to remember my token and send me the token on every request. So instead of remembering/sending username/password now it will do the same for tokens! So client implementation code does not get any less.

So what is the real value here?

Answer 1

It really depends on the scenario - it's hard to tell without knowing more about the API - but usage of "authentication tokens" is far from universal, you're right that many APIs don't need (and don't use) them. Many APIs simply require an API key to be sent with every request (often via HTTPS to prevent it from being intercepted), or require an API key to identify the user and also a digital signature with a "secret key" to prove the user's identity (see When working with most APIs, why do they require two types of authentication, namely a key and a secret? ).

Usernames/passwords are not often used in public APIs because they're not flexible enough and do not provide enough "separation" between the user identity and the application identity. E.g. you register as a developer to use the Flickr API and create an iPhone app that uses that API - would you really want your developer username/password to be built into the app? What if you change your password later? What if you want to develop 5 apps and track usage for them separately and be able to shut off any app at any time without affecting the others?

However, for cases where you truly want to identify a human user only, not an appplication (e.g. a private API back-end that will only serve your own applications, not a public API), in most scenarios I don't see anything wrong with what you suggested, i.e. username/password over HTTPS with every request. Oh, by the way, auth tokens have the added advantage of being "restrictable" (can expire at a certain time, can be restricted to certain actions only, etc), but obviously this is only useful in very specific scenarios.

ALSO: As user "Dan" pointed out above, when designing an API that requires sending the username/password with every request (or with any request really, even if it's just the login request), be careful how you do it. If you're using a technique which browsers support by default (e.g. HTTP Basic Auth), you're preventing yourself from ever exposing the API safely to cross-domain users (i.e. most likely your API can never be safely called directly from the browser, i.e. from AJAX / Flash / Silverlight code).

This is a complex topic which can't be explained fully here, but just remember that if your API is relying on any security credentials that the browser can remember and then "silently" inject in every request (e.g. HTTP Basic Auth, cookies), then it's NOT safe to enable cross-domain access to that API using any cross-domain technique (CORS, JSONP, crossdomain.xml, etc).