In this case, the application is authenticated per se by using its client id and secret.ĭevice Authorization Flow: A grant that enables use by apps on input-constrained devices, such as smart TVs. It has the advantage that no redirect to the Authorization server is involved, so it is applicable in the use cases where a redirect is infeasible.Ĭlient Credentials Grant Type: Used for non-interactive applications e.g., automated processes, microservices, etc. It is, therefore, limited to Clients that are completely trusted. Resource Owner Credentials Grant Type: This grant requires the Client first to acquire the resource owner’s credentials, which are passed to the Authorization server.
The first option is now deprecated due to potential token leakage.Īuthorization Code Grant with Proof Key for Code Exchange (PKCE): This authorization flow is similar to the Authorization Code grant, but with additional steps that make it more secure for mobile/native apps and SPAs. In the Implicit flow, the authorization server may return the Access Token as a parameter in the callback URI or as a response to a form post. Implicit Grant: A simplified flow where the Access Token is returned directly to the Client. A better alternative is the Authorization Code with PKCE grant, below. However, here, the client secret cannot be stored securely, and so authentication, during the exchange, is limited to the use of client id alone. The Authorization Code flow might be used by Single Page Apps (SPA) and mobile/native apps. This is the best option for traditional web apps where the exchange can securely happen on the server side. The authorization framework provides several grant types to address different scenarios:Īuthorization Code grant: The Authorization server returns a single-use Authorization Code to the Client, which is then exchanged for an Access Token. In OAuth 2.0, grants are the set of steps a Client has to perform to get resource access authorization. With the Access Token, the Client requests access to the resource from the Resource server. The Authorization server redirects back to the Client with either an Authorization Code or Access Token, depending on the grant type, as it will be explained in the next section. The Resource owner interacts with the Authorization server to grant access. The Authorization server authenticates the Client and verifies that the requested scopes are permitted. The Client requests authorization ( authorization request) from the Authorization server, supplying the client id and secret to as identification it also provides the scopes and an endpoint URI ( redirect URI) to send the Access Token or the Authorization Code to. The token request, exchange, and response follow this general flow:
Using OAuth 2.0, access requests are initiated by the Client, e.g., a mobile app, website, smart TV app, desktop application, etc. It accepts and validates an Access Token from the Client and returns the appropriate resources to it.Īt the most basic level, before OAuth 2.0 can be used, the Client must acquire its own credentials, a client id and client secret, from the Authorization Server in order to identify and authenticate itself when requesting an Access Token.
Resource Server: A server that protects the user’s resources and receives access requests from the Client. The authorization server exposes two endpoints: the Authorization endpoint, which handles the interactive authentication and consent of the user, and the Token endpoint, which is involved in a machine to machine interaction. To access resources, the Client must hold the appropriate Access Token.Īuthorization Server: This server receives requests from the Client for Access Tokens and issues them upon successful authentication and consent by the Resource Owner.
Resource Owner: The user or system that owns the protected resources and can grant access to them.Ĭlient: The client is the system that requires access to the protected resources. These define the essential components of an OAuth 2.0 system, and are as follows: The idea of roles is part of the core specification of the OAuth2.0 authorization framework.