Florian Helmschmidt, Pedram Hosseyni, Ralf Küsters, Klaas Pruiksma, Clara Waldmann, and Tim Würtele, “The Grant Negotiation and Authorization Protocol: Attacking, Fixing, and Verifying an Emerging Standard,” in 28th European Symposium on Research in Computer Security (ESORICS 2023), 2023. To appear.
Abstract
The Grant Negotiation and Authorization Protocol (GNAP) is an emerging authorization and authentication protocol which aims to consolidate and unify several use-cases of OAuth 2.0 and many of its common extensions while providing a higher degree of security. OAuth 2.0 is an essential cornerstone of the security of authorization and authentication for the Web, IoT, and beyond, and is used, among others, by many global players, like Google, Facebook, and Microsoft. Historical limitations of OAuth 2.0 and its extensions have led prominent members of the OAuth community to create GNAP, a newly designed protocol for authorization and authentication. Given GNAP's advantages over OAuth 2.0 and its support within the OAuth community, GNAP is expected to become at least as important as OAuth 2.0. In this paper, we present the first formal security analysis of GNAP. We build a detailed formal model of GNAP, based on the Web Infrastructure Model (WIM) of Fett, Küsters, and Schmitz, and provide formal statements of the key security properties of GNAP, namely authorization, authentication, and session integrity. We discovered several attacks on GNAP in the process of trying to prove these properties. We present these attacks, as well as changes to the protocol that prevent them. These modifications have been incorporated into the GNAP specification after discussion with the GNAP working group. We give the first formal security guarantees for GNAP, by proving that GNAP, with our modifications applied, satisfies the mentioned security properties. GNAP was still an early draft when we began our analysis, but is now on track to be adopted as an IETF standard. Hence, our analysis is just in time to help ensure the security of this important emerging standard.BibTeX
Florian Helmschmidt, Pedram Hosseyni, Ralf Küsters, Klaas Pruiksma, Clara Waldmann, and Tim Würtele, “The Grant Negotiation and Authorization Protocol: Attacking, Fixing, and Verifying an Emerging Standard,” Cryptology ePrint Archive, Technical Report 2023/1325, 2023.
Abstract
The Grant Negotiation and Authorization Protocol (GNAP) is an emerging authorization and authentication protocol which aims to consolidate and unify several use-cases of OAuth 2.0 and many of its common extensions while providing a higher degree of security. OAuth 2.0 is an essential cornerstone of the security of authorization and authentication for the Web, IoT, and beyond, and is used, among others, by many global players, like Google, Facebook, and Microsoft. Historical limitations of OAuth 2.0 and its extensions have led prominent members of the OAuth community to create GNAP, a newly designed protocol for authorization and authentication. Given GNAP's advantages over OAuth 2.0 and its support within the OAuth community, GNAP is expected to become at least as important as OAuth 2.0. In this paper, we present the first formal security analysis of GNAP. We build a detailed formal model of GNAP, based on the Web Infrastructure Model (WIM) of Fett, Küsters, and Schmitz, and provide formal statements of the key security properties of GNAP, namely authorization, authentication, and session integrity. We discovered several attacks on GNAP in the process of trying to prove these properties. We present these attacks, as well as changes to the protocol that prevent them. These modifications have been incorporated into the GNAP specification after discussion with the GNAP working group. We give the first formal security guarantees for GNAP, by proving that GNAP, with our modifications applied, satisfies the mentioned security properties. GNAP was still an early draft when we began our analysis, but is now on track to be adopted as an IETF standard. Hence, our analysis is just in time to help ensure the security of this important emerging standard.BibTeX
Karthikeyan Bhargavan, Abhishek Bichhawat, Pedram Hosseyni, Ralf Küsters, Klaas Pruiksma, Guido Schmitz, Clara Waldmann, and Tim Würtele, “Layered Symbolic Security Analysis in DY*,” in 28th European Symposium on Research in Computer Security (ESORICS 2023), 2023. To appear.
Abstract
While cryptographic protocols are often analyzed in isolation, they are typically deployed within a stack of protocols, where each layer relies on the security guarantees provided by the protocol layer below it, and in turn provides its own security functionality to the layer above. Formally analyzing the whole stack in one go is infeasible even for semi-automated verification tools, and impossible for pen-and-paper proofs. The DY* protocol verification framework offers a modular and scalable technique that can reason about large protocols, specified as a set of F* modules. However, it does not support the compositional verification of layered protocols since it treats the global security invariants monolithically. In this paper, we extend DY* with a new methodology that allows analysts to modularly analyze each layer in a way that compose to provide security for a protocol stack. Importantly, our technique allows a layer to be replaced by another implementation, without affecting the proofs of other layers. We demonstrate this methodology on two case studies. We also present a verified library of generic authenticated and confidential communication patterns that can be used in future protocol analyses and is of independent interest.BibTeX
Karthikeyan Bhargavan, Abhishek Bichhawat, Pedram Hosseyni, Ralf Küsters, Klaas Pruiksma, Guido Schmitz, Clara Waldmann, and Tim Würtele, “Layered Symbolic Security Analysis in DY*,” Cryptology ePrint Archive, Technical Report 2023/1329, 2023.
Abstract
While cryptographic protocols are often analyzed in isolation, they are typically deployed within a stack of protocols, where each layer relies on the security guarantees provided by the protocol layer below it, and in turn provides its own security functionality to the layer above. Formally analyzing the whole stack in one go is infeasible even for semi-automated verification tools, and impossible for pen-and-paper proofs. The DY* protocol verification framework offers a modular and scalable technique that can reason about large protocols, specified as a set of F* modules. However, it does not support the compositional verification of layered protocols since it treats the global security invariants monolithically. In this paper, we extend DY* with a new methodology that allows analysts to modularly analyze each layer in a way that compose to provide security for a protocol stack. Importantly, our technique allows a layer to be replaced by another implementation, without affecting the proofs of other layers. We demonstrate this methodology on two case studies. We also present a verified library of generic authenticated and confidential communication patterns that can be used in future protocol analyses and is of independent interest.BibTeX
