System software is often complex and hides exploitable security vulnerabilities. Formal verification promises bug-free software but comes with a prohibitive proof cost. We present Spoq2, the first verification framework to highly automate security verification of unmodified system software. Spoq2 is based on the observation that many security properties, such as noninterference, can be reduced to establishing inductive invariants on individual transitions of a transition system that models system software. However, directly verifying such invariants for real system code overwhelms existing SMT solvers. Spoq2 makes this possible by automatically reducing verification complexity. It decomposes transitions into individual execution paths, extends cone-of-influence analysis to the individual transition level, and eliminates irrelevant machine states, clauses, and control-flow paths before invoking the SMT solver. Spoq2 further optimizes how pointer operations are modeled and verified through pointer abstractions that eliminate expensive bit-wise operations from SMT queries. We demonstrate the effectiveness of Spoq2 by verifying security properties of four unmodified, real-world system codebases with minimal manual effort.

Trusted Execution Environments (TEE) have been widely adopted as a protection approach for security-critical applications. Although feature extensions have been previously proposed to improve the usability of enclaves, their provision patterns are still confronted with security challenges. This paper presents Palantir, a verifiable multi-layered inter-enclave privilege model for secure feature extensions to enclaves. Specifically, a parent-children inter-enclave relationship, with which a parent enclave is granted two privileged permissions, the Execution Control and Spatial Control, over its children enclaves to facilitate secure feature extensions, is introduced. Moreover, by enabling nesting parent-children relationships, Palantir achieves multi-layered privileges (MLP) that allow feature extensions to be placed in various privilege layers following the Principle of Least Privilege. To prove the security of Palantir, we verified that our privilege model does not break or weaken the security guarantees of enclaves by building and verifying a formal model named TAP^∞. Furthermore, We implemented a prototype of Palantir on Penglai, an open-sourced RISC-V TEE platform. The evaluation demonstrates the promising performance of Palantir in runtime overhead and startup latencies.