We present the first formally-verified Internet router, which is part of the SCION Internet architecture. SCION routers run a cryptographic protocol for secure packet forwarding in an adversarial environment. We verify both the protocol's network-wide security properties and the low-level properties of its implementation. Namely, we develop a series of protocol models by refinement in Isabelle/HOL and we use an automated program verifier to prove that the router's Go code satisfies crash freedom, freedom from data races, and adheres to the most concrete model in our series of refinements. Both verification efforts are soundly linked together.

Today’s Internet is built on decades-old networking protocols that lack scalability, reliability and security. In response, the networking community has developed path-aware Internet architectures that solve these problems while simultaneously empowering end hosts to exert some control on their packets’ route through the network. In these architectures, autonomous systems authorize forwarding paths in accordance with their routing policies, and protect these paths using cryptographic authenticators. For each packet, the sending end host selects an authorized path and embeds it and its authenticators in the packet header. This allows routers to efficiently determine how to forward the packet. The central security property of the data plane, i.e., of forwarding, is that packets can only travel along authorized paths. This property, which we call path authorization, protects the routing policies of autonomous systems from malicious senders. The fundamental role of packet forwarding in the Internet’s ecosystem and the complexity of the authentication mechanisms employed call for a formal analysis. We develop IsaNet, a parameterized verification framework for data plane protocols in Isabelle/HOL. We first formulate an abstract model without an attacker for which we prove path authorization. We then refine this model by introducing a Dolev–Yao attacker and by protecting authorized paths using (generic) cryptographic validation fields. This model is parametrized by the path authorization mechanism and assumes five simple verification conditions. We propose novel attacker models and different sets of assumptions on the underlying routing protocol. We validate our framework by instantiating it with nine concrete protocol variants and prove that they each satisfy the verification conditions (and hence path authorization). The invariants needed for the security proof are proven in the parametrized model instead of the instance models. Our framework thus supports low-effort security proofs for data plane protocols. In contrast to what could be achieved with state-of-the-art automated protocol verifiers, our results hold for arbitrary network topologies and sets of authorized paths.

Today’s Internet is built on decades-old networking protocols that lack scalability, reliability, and security. In response, the networking community has developed path-aware Internet architectures that solve these issues while simultaneously empowering end hosts. In these architectures, autonomous systems construct authenticated forwarding paths based on their routing policies. Each end host then selects one of these authorized paths and includes it in the packet header, thus allowing routers to efficiently determine how to forward the packet. A central security property of these architectures is path authorization, requiring that packets can only travel along authorized paths. This property protects the routing policies of autonomous systems from malicious senders.The fundamental role of packet forwarding in the Internet and the complexity of the authentication mechanisms employed call for a formal analysis. In this vein, we develop in Isabelle/HOL a parameterized verification framework for path-aware data plane protocols. We first formulate an abstract model without an attacker for which we prove path authorization. We then refine this model by introducing an attacker and by protecting authorized paths using (generic) cryptographic validation fields. This model is parameterized by the protocol’s authentication mechanism and assumes five simple verification conditions that are sufficient to prove the refinement of the abstract model. We validate our framework by instantiating it with several concrete protocols from the literature and proving that they each satisfy the verification conditions and hence path authorization. No invariants must be proven for the instantiation. Our framework thus supports low-effort security proofs for data plane protocols. The results hold for arbitrary network topologies and sets of authorized paths, a guarantee that state-of-the-art automated security protocol verifiers cannot currently provide.

Lighthouse projects like CompCert, seL4, IronFleet, and DeepSpec have demonstrated that full system verification is feasible by establishing a refinement between an abstract system specification and an executable implementation. Existing approaches however impose severe restrictions on the abstract system specifications due to their limited expressiveness or versatility, or on the executable code due to their use of suboptimal code extraction or inexpressive program logics. We propose a novel methodology that combines the compositional refinement of event-based models of distributed systems with the verification of full-fledged program code using expressive separation logics, which support features of realistic programming languages like heap data structures and concurrency. Our main technical contribution is a formal framework that soundly relates event-based system models to program specifications in separation logics. This enables protocol development tools to soundly interoperate with program verifiers to establish a refinement between the model and the code. We formalized our framework, Igloo, in Isabelle/HOL. We report on three case studies, a leader election protocol, a replication protocol, and a security protocol, for which we refine formal requirements into program specifications that we implement in Java and Python and prove correct using the VeriFast and Nagini tools.

The Internet will undergo a major transformation as satellite-based Internet service providers start to disrupt the market. Constellations of hundreds to thousands of satellites promise to offer low-latency Internet to even the most remote areas. We anticipate exciting business and research opportunities.