On the Security of Single Sign-On Vladislav Mladenov (Place of birth: Pleven/Bulgaria)
[email protected] 30th June 2017 Ruhr-University Bochum Horst G¨ortz Institute for IT-Security Chair for Network and Data Security Dissertation zur Erlangung des Grades eines Doktor-Ingenieurs der Fakult¨atf¨urElektrotechnik und Informationstechnik an der Ruhr-Universit¨atBochum First Supervisor: Prof. Dr. rer. nat. J¨org Schwenk Second Supervisor: Prof. Dr.-Ing. Felix Freiling www.nds.rub.de Abstract Single Sign-On (SSO) is a concept of delegated authentication, where an End- User authenticates only once at a central entity called Identity Provider (IdP) and afterwards logs in at multiple Service Providers (SPs) without reauthenti- cation. For this purpose, the IdP issues an authentication token, which is sent to the SP and must be verified. There exist different SSO protocols, which are implemented as open source libraries or integrated in commercial products. Google, Facebook, Microsoft and PayPal belong to the most popular SSO IdPs. This thesis provides a comprehensive security evaluation of the most popular and widely deployed SSO protocols: OpenID Connect, OpenID, and SAML. A starting point for this research is the development of a new concept called malicious IdP, where a maliciously acting IdP is used to attack SSO. Generic attack classes are developed and categorized according to the requirements, goals, and impact. These attack classes are adapted to different SSO proto- cols, which lead to the discovery of security critical vulnerabilities in Software- as-a-Service Cloud Providers, eCommerce products, web-based news portals, Content-Management systems, and open source implementations.