Question

In the three legged flow you have a callbackAuthorize which would allow you to retrieve the code, which you can exchange for an access token. I’m wondering if two legged oauth has something similar (which calls you back with your auth token) or if you simply provide the authorize url your client_id + client_secret and the response is your auth token?

Answer 1

The 2-legged flow in OAuth 2 is called Client Credentials flow and is really simple.

The step you are refering to as callbackAuthorize is the Autthorization Grant request and the documentation quite clearly negates the need for such a request:

Since the client authentication is used as the authorization grant, no additional authorization request is needed.