Access Control as Verified Parse Constraints

2026-09-11

AI Summary

研究解决了安全网关中因实现错误导致的访问控制问题，通过使用经验证的解析约束和SMT求解器一次性验证所有策略，确保了固定端点集下策略执行的正确性。

Abstract

Commercial security gateways repeatedly ship implementation bugs in the code path between the network and the policy decision: hand-written enforcement logic that diverges from the policy author's intent, and ad-hoc request parsers at the network boundary that introduce memory-safety flaws of their own. In both cases the bug is in the deployed enforcement code, not in the policy. Existing approaches either leave the enforcement runtime unverified or connect a formal model to a hand-written engine only by differential testing. Our contribution is a class result: a forward-only, backtrack-free EverParse validator is a verified recognizer for a bounded, finite-state class, and access-control decision functions with fixed-offset fields and bounded disjunction belong to it, so one machine-checked proof transfers to every policy in the class rather than being re-established per policy. Concretely, we encode a bounded policy language's decision function into a fixed-size byte buffer and verify the enforcement code once---covering all byte values---with an SMT solver, proving the validator accepts if and only if the decision function accepts, for every policy, request, and session. Editing rule content over a fixed endpoint set then needs no new proof; adding endpoints reruns the toolchain; extending the language needs new proofs. We establish faithful enforcement of a policy, not that a policy is itself secure. The verified gate is platform-independent, requiring only EverParse/Z3 and a C compiler, whose correctness we assume. We demonstrate a deployment on the seL4 microkernel, which ensures every request passes through the gate and that unverified components cannot corrupt the verified enforcement chain.

Problem

• Access Control
• Verified Parse Constraints
• Implementation Bugs
• Policy Enforcement
• Memory-safety Flaws

Innovation

• Verified Parse Constraints
• Access Control
• SMT Solver
• EverParse
• Platform-Independent