Which interface in Liferay is commonly used for user authentication?

The OAuth2 implementation is widely used for user authentication in Liferay due to its robust framework for securing authorization and authentication processes. OAuth2 allows delegated access to a user's resources without exposing their credentials, making it particularly suitable for modern applications where securing user data is paramount. In Liferay, this implementation enables third-party applications to authenticate users through a secure token-based system, facilitating seamless integration with external services and applications.

The significance of this approach lies in its alignment with industry standards for security, enhancing user experience by allowing single sign-on (SSO) capabilities. This means users can authenticate once and gain access to multiple applications without needing to log in separately for each one. The adoption of OAuth2 also supports various flows, including authorization code, implicit, resource owner password credentials, and client credentials, offering flexibility in how different applications can interact securely with Liferay.

REST API, SOAP API, and GraphQL API primarily serve as methods to interact with the server to access and manipulate data rather than being specifically tailored for user authentication. While they may play a role in user-related operations, they are not primarily focused on the secure authentication process like OAuth2 is.