SAML Artifact Information Flow Revisited

The standardized OASIS Security Assertion Markup Language (SAML) has become one of the most deployed frameworks in federated identity management even though it focuses only on single sign-on. Answering industry’s pursuit of the reduction of user-management costs and enabling cost-efficient deployment because of its browser-based profiles, SAML is believed to become widely used soon. With the revision to Version 2.0, especially SAML’s browser/artifact profile has gained new security measures defeating old vulnerabilities. We analyze this profile and focus on the problem of artifact information flow. We devise a concrete exploit to demonstrate the impact of this problem. We address this problem by a new browser/artifact profile called Janus. The innovation is to split the artifact into two independent shares that have different information flow in a standard web browser. This new method defeats artifact information flow efficiently without relying on assumptions on the artifact lifetime.