WS-Federation Single Sign-on Profiles Explained

WS-Federation is a legacy protocol that facilitates identity sharing across different security realms, primarily used in older systems like SharePoint and on-premises Windows servers. Despite its age and reliance on XML and SOAP, WS-Federation remains relevant, particularly in sectors like finance and healthcare, where Microsoft ADFS is prevalent. The protocol operates through a Security Token Service (STS) and a Relying Party (RP), utilizing claims-based identity for detailed access control. It functions through browser redirects, similar to OAuth's implicit flow, and its security depends on validating digital signatures against federation metadata. Although WS-Federation is seen as clunky compared to modern protocols like OIDC, it continues to secure millions of enterprise logins, serving as a critical component in hybrid cloud setups. Despite being in maintenance mode, with no new features being developed, transitioning away from WS-Federation requires careful planning and often involves bridging solutions to gradually integrate modern protocols like OIDC, ensuring security and compatibility across legacy and new systems.