What strategy should be used in an application that does not support identity providers but needs to upgrade to single sign-on?

The most effective strategy for an application that does not support identity providers but requires an upgrade to single sign-on (SSO) is to incorporate a header-based authentication system. This method allows you to implement a lightweight approach for transferring authentication credentials when traditional identity provider systems, such as OAuth or SAML, are not compatible.

By using header-based authentication, the application can receive token-based credentials such as JWT (JSON Web Tokens) or custom tokens that are passed via HTTP headers. This technique can bridge the gap for applications that don’t support identity providers, enabling them to leverage SSO capabilities while still keeping the integration simpler and more tailored to their existing architecture.

In addition, header-based authentication is adaptable, making it easier to integrate with various frontend technologies or API gateways that may not support complex protocols like SAML or OAuth directly. This approach also minimizes the need for extensive changes to the existing application codebase, allowing for a smoother transition to SSO capabilities.

Other options such as implementing SAML 2.0 or utilizing OAuth 2.0 might require significant changes to the application’s structure and require it to support these protocols directly. Similarly, incorporating federated authentication methods could also necessitate broader support for identity management systems, potentially exceeding