Abstract Interpretation of Stateful Networks

Modern networks achieve robustness and scalability by maintaining states on their nodes. These nodes are referred to as middleboxes and are essential for network functionality. However, the presence of middleboxes drastically complicates the task of network verification. Previous work showed that the problem is undecidable in general and EXPSPACE-complete when abstracting away the order of packet arrival. We describe a new algorithm for conservatively checking isolation properties of stateful networks. The asymptotic complexity of the algorithm is polynomial in the size of the network, albeit being exponential in the maximal number of queries of the local state that a middlebox can do, which is often small. Our algorithm is sound, i.e., it can never miss a violation of safety but may fail to verify some properties. The algorithm performs on-the fly abstract interpretation by (1) abstracting away the order of packet processing and the number of times each packet arrives, (2) abstracting away correlations between states of different middleboxes and channel contents, and (3) representing middlebox states by their effect on each packet separately, rather than taking into account the entire state space. We show that the abstractions do not lose precision when middleboxes may reset in any state. This is encouraging since many real middleboxes reset, e.g., after some session timeout is reached or due to hardware failure

Embedding Session Types in HML

Recent work on the enhancement of multiparty session types with logical annotations enable the effective verification of properties on (1) the structure of the conversations, (2) the sorts of the messages, and (3) the actual values exchanged. In [3] we extend this work to enable the specification and verification of mutual effects of multiple cross-session interactions. Here we give a sound and complete embedding into the Hennessy-Milner logic to justify the expressiveness of the approach in [3] and to provide it with a logical background that will enable us to compare it with similar approaches

LightBox: Full-stack Protected Stateful Middlebox at Lightning Speed

Running off-site software middleboxes at third-party service providers has been a popular practice. However, routing large volumes of raw traffic, which may carry sensitive information, to a remote site for processing raises severe security concerns. Prior solutions often abstract away important factors pertinent to real-world deployment. In particular, they overlook the significance of metadata protection and stateful processing. Unprotected traffic metadata like low-level headers, size and count, can be exploited to learn supposedly encrypted application contents. Meanwhile, tracking the states of 100,000s of flows concurrently is often indispensable in production-level middleboxes deployed at real networks. We present LightBox, the first system that can drive off-site middleboxes at near-native speed with stateful processing and the most comprehensive protection to date. Built upon commodity trusted hardware, Intel SGX, LightBox is the product of our systematic investigation of how to overcome the inherent limitations of secure enclaves using domain knowledge and customization. First, we introduce an elegant virtual network interface that allows convenient access to fully protected packets at line rate without leaving the enclave, as if from the trusted source network. Second, we provide complete flow state management for efficient stateful processing, by tailoring a set of data structures and algorithms optimized for the highly constrained enclave space. Extensive evaluations demonstrate that LightBox, with all security benefits, can achieve 10Gbps packet I/O, and that with case studies on three stateful middleboxes, it can operate at near-native speed.Comment: Accepted at ACM CCS 201

Foundational Verification of Stateful P4 Packet Processing

P4 is a standardized programming language for the network data plane. But P4 is not just for routing anymore. As programmable switches support stateful objects, P4 programs move beyond just stateless forwarders into new stateful applications: network telemetry (heavy hitters, DDoS detection, performance monitoring), middleboxes (firewalls, NAT, load balancers, intrusion detection), and distributed services (in-network caching, lock management, conflict detection). The complexity of stateful programs and their richer specifications are beyond what existing P4 program verifiers can handle. Verifiable P4 is a new interactive verification framework for P4 that (1) allows reasoning about multi-packet properties by specifying the per-packet relation between initial and final states; (2) performs modular verification, especially providing a modular description for stateful objects; (3) is foundational, i.e., with a machine-checked soundness proof with respect to a formal operational semantics of P4_{16} (the current specification of P4) in Coq. In addition, our framework includes a proved-correct reference interpreter. We demonstrate the framework with the specification and verification of a stateful firewall that uses a sliding-window Bloom filter on a Tofino switch to block (most) unsolicited traffic