OAuth (Open Authorization)

OAuth (Open Authorization) is an open standard protocol that allows secure authorization and authentication of users in a client-server application scenario. It provides a way for users to grant permission to third-party applications to access their protected resources without sharing their credentials (such as username and password).

Here’s an example scenario to illustrate OAuth:

1. User wants to access a service or application (referred to as the “client”) that requires authorization to access their resources.

2. The client redirects the user to the OAuth authorization server, where the user is prompted to authenticate themselves.

3. Once authenticated, the authorization server presents the user with a consent screen, requesting their permission to grant the client access to specific resources.

4. If the user grants permission, the authorization server generates an authorization code or access token and redirects the user back to the client application.

5. The client application sends a request to the authorization server, including the authorization code or access token received from the previous step.

6. The authorization server validates the code or token and issues an access token to the client.

7. The client can then use the access token to make authorized requests to the protected resources on behalf of the user.

Here’s a sequence diagram illustrating the interactions between the different entities involved in the OAuth flow:

Now, let’s explain each step in detail:

1. User requests to access protected resources: The user initiates a request to access protected resources within the client application, such as viewing personal information or performing actions on their behalf.

2. Client redirects user to AuthorizationServer: The client application redirects the user to the authorization server for authentication and authorization. This typically involves redirecting the user to a login page or an authorization endpoint.

3. User authenticates and provides credentials: The user authenticates themselves with the authorization server by providing their credentials, such as username and password.

4. Authorization server presents consent screen: Upon successful authentication, the authorization server presents the user with a consent screen. This screen explains the permissions and access rights requested by the client application.

5. User grants permission: The user reviews the requested permissions and decides whether to grant permission to the client application. If they grant permission, they proceed to the next step.

6. Authorization server redirects to client with authorization code or access token: The authorization server redirects the user back to the client application, providing an authorization code or an access token as part of the redirection URL. The authorization code or access token serves as proof of the user’s consent.

7. Client requests access token: The client sends a request to the authorization server to exchange the authorization code or access token for an access token that can be used to make authorized requests to protected resources.

8. Authorization server issues access token: The authorization server validates the authorization code or access token and, if valid, issues an access token to the client. The access token is a credential that represents the user’s authorization to access specific resources.

9. Client requests protected resources with access token: The client includes the access token in subsequent requests to the resource server when requesting protected resources. The access token serves as proof of authorization.

10. Resource server provides requested resources: The resource server receives the client’s request along with the access token. It verifies the access token to ensure its validity and then provides the requested resources back to the client.

What is Scope in OAuth?

In OAuth, scopes are used to define the specific permissions or access rights requested by an application when requesting authorization from a user. Scopes allow users to control and limit the access that an application has to their protected resources. When a user authorizes an application, they can grant or deny specific scopes requested by the application.

Scopes are typically represented as strings and are defined by the OAuth provider. The specific scopes available may vary depending on the provider and the API or services it offers. Here are some common examples of scopes:

1. read: Grants read-only access to certain resources or data.
2. write: Grants the ability to create, update, or delete resources.
3. profile: Grants access to the user’s profile information, such as name, email, and profile picture.
4. email: Grants access to the user’s email address.
5. offline_access: Grants long-lasting access to resources even when the user is not actively present or authenticated.
6. calendar: Grants access to the user’s calendar events.
7. contacts: Grants access to the user’s contacts or address book.

When an application requests authorization from a user, it specifies the desired scopes in the authorization request. The user then sees the requested scopes during the authorization process and can choose to grant or deny each scope individually. The granted scopes determine the level of access the application will have to the user’s protected resources.

It’s important to request only the necessary scopes required for your application’s functionality to minimize the permissions granted to the application and enhance user privacy and security. Additionally, be sure to clearly communicate to users why you are requesting specific scopes and how their data will be used to build trust and transparency.

The available scopes and their specific names and meanings may vary between OAuth providers and their respective APIs. It’s recommended to refer to the documentation of the OAuth provider you are integrating with to understand the available scopes and their descriptions