How do you choose between OAuth2 and OpenID Connect for web authorization?

OAuth2 is for authorization, allowing apps to act on behalf of users, while OpenID Connect (OIDC) is for authentication, verifying user identity. Choose OAuth2 if you need to access user data from another service, and OIDC if you need to verify who the user is. For example in a banking app, if you need to access account data from another bank on behalf of the user, use OAuth2. If you need to verify the user's identity before they can access their account, use OIDC.

P.S : the implicit ( aka: implicit flow or implicit grant ) & resource owner password ( aka: password grant ) grant types are now deprecated and recommended to NOT use them anymore. It's recommended to use Authorization Code grant Instead of implicit flow

Additional technical considerations: Scopes: The comment doesn't mention scopes, which define the level of access granted to the client (e.g., basic profile vs. full email access). Token validation: Resource servers validate access tokens issued by the authorization server, ensuring resource security. Refresh tokens: Access tokens are usually short-lived, while refresh tokens allow clients to obtain new access tokens without user interaction. Security best practices: Implementing secure token storage, transport, and validation is crucial for preventing unauthorized access.

OAuth2 is a framework that lets a third-party app (the client) access resources from a server (like an API) on behalf of a user. The user gives the client a limited access token to request resources. This token is issued by an authorization server, which checks the user’s identity and consent. OAuth2 defines four roles (resource owner, client, resource server, and authorization server) and four grant types (authorization code, implicit, password credentials, and client credentials) for different authorization scenarios.

If you only need to authorize a client to access resources on behalf of a user, OAuth2 is sufficient. However, if you also need to authenticate the user and get their basic profile information, OpenID Connect is the better choice as it extends OAuth2 with an identity layer. For example, in a banking app, if you want to allow a third-party app to access a user's account details OAuth2 would be enough. But if you also want the third-party app to authenticate the user and get their profile information (like name, email), you should use OpenID Connect.

Additional technical considerations: Standardized claims: OIDC defines a set of standard claims (name, email, address, etc.) for consistent user profile information exchange. Discovery and registration: Clients can dynamically discover and interact with IDPs using standardized endpoints, simplifying integration. Authentication flows: OIDC leverages OAuth 2.0 grant types (authorization code, implicit) for authentication flows, ensuring secure user login.

OpenID Connect expands on OAuth2 by introducing an identity component enabling a client to authenticate a users identity and obtain profile information. Users authenticate via an identity provider (such, as Google or Facebook) using OpenID Connect, which provides the client with an ID token. This ID token, encoded as a JSON Web Token (JWT) includes user information such as name, email address and profile picture. Additionally the client can ask for access. Refresh tokens, from the identity provider to access resources.

Overall, the comment effectively captures the primary distinctions between OAuth2 and OpenID Connect. Technical areas for potential expansion: Token introspection and revocation: OAuth2 defines mechanisms for token introspection (checking token validity) and revocation, enhancing security. Dynamic client registration: OIDC supports dynamic client registration for streamlined integration with identity providers. User consent: Both protocols emphasize user consent management for data access and sharing. To summarize, OAuth2 lays the groundwork for authorization, while OIDC builds upon it to provide a standardized identity layer, enabling secure authentication and user information management.

OAuth2 is widely adopted for delegated authorization, allowing apps to act on a user's behalf without sharing credentials. However, when identity verification is crucial, OpenID Connect provides an additional ID token, which is a significant enhancement. This ID token adheres to a standard format and can be reliably interpreted by multiple systems, ensuring consistent identity verification across different platforms. It's essential to evaluate whether your application requires just delegated access or also robust identity assurance to make an informed choice between the two.

Choosing between OAuth2 and OpenID Connect depends on what your web app needs. If you just need access to resources on behalf of a user and don't need their identity info, OAuth2 should suffice. You can choose an OAuth2 grant type that fits your app’s architecture and security needs. However, if you need to verify the user's identity and get basic profile information, OpenID Connect is the better option. It uses OAuth2 but also provides an ID token with an access token, using either the authorization code flow or implicit flow.

When implementing OAuth2 or OpenID Connect, it's crucial to prioritize security. HTTPS is a must for protecting data in transit. PKCE is particularly important for public clients, such as mobile and single-page applications, to mitigate the risk of code interception. The use of state and nonce parameters is a best practice for maintaining the integrity of the authentication process and should be non-negotiable. Token validation and secure storage are foundational to preventing unauthorized access, and keeping libraries up-to-date is a proactive measure against emerging security vulnerabilities.

If you're using OAuth2 or OpenID Connect for your web application, here are some tips to implement them securely and effectively: 1. Use HTTPS: Ensure all communication between the client, authorization server, resource server, and identity provider is encrypted. 2. Implement PKCE: Use Proof Key for Code Exchange to prevent authorization code interception attacks. 3. Use State and Nonce Parameters: Protect against CSRF and replay attacks. 4. Validate Tokens: Check the access and ID tokens according to their specifications. 5. Secure Token Storage: Store access and refresh tokens securely on the client side. 6. Respect Token Scope and Expiration: Follow the scope and expiration rules for tokens.