一句话：提出 Blade，用类型系统与 protect 原语自动切断推测性秘密的数据流，消除密码代码中的推测泄漏。
该论文研究推测执行导致密码代码通过缓存等途径泄漏秘密的问题。现有防护要么完全禁止推测，要么难以自动消除泄漏。Blade 的核心思想是：只需切断可能推测性引入秘密的表达式（source）到泄漏秘密的表达式（sink）之间的数据流，而非禁止所有推测。作者提出静态类型系统，将表达式分为 transient（可能含推测性秘密）与 stable，并要求所有 sink 都是 stable；同时引入抽象原语 protect，以细粒度阻止推测，并由类型系统自动合成最少 protect。Blade 在 Cranelift WebAssembly 编译器中实现，用于修复多个已验证但存在推测泄漏的密码原语实现。评估表明，Blade 能自动修复现有程序，无需用户干预，即使以 fence 实现 protect 也保持高效。
We introduce Blade, a new approach to automatically and efficiently eliminate speculative leaks from cryptographic code. Blade is built on the insight that to stop leaks via speculative execution, it suffices to cut the dataflow from expressions that speculatively introduce secrets ( sources ) to those that leak them through the cache ( sinks ), rather than prohibit speculation altogether. We formalize this insight in a static type system that (1) types each expression as either transient , i.e., possibly containing speculative secrets or as being stable , and (2) prohibits speculative leaks by requiring that all sink expressions are stable. Blade relies on a new abstract primitive, protect , to halt speculation at fine granularity. We formalize and implement protect using existing architectural mechanisms, and show how Blade’s type system can automatically synthesize a minimal number of protect s to provably eliminate speculative leaks. We implement Blade in the Cranelift WebAssembly compiler and evaluate our approach by repairing several verified, yet vulnerable WebAssembly implementations of cryptographic primitives. We find that Blade can fix existing programs that leak via speculation automatically , without user intervention, and efficiently even when using fences to implement protect .
@article{paperbot1148,
title = {Automatically eliminating speculative leaks from cryptographic code with blade},
author = {Marco Vassena and Craig Disselkoen and Klaus von Gleissenthall and Sunjay Cauligi and Rami Gökhan Kıcı and Ranjit Jhala and Dean Tullsen and Deian Stefan},
journal = {Proceedings of the ACM on Programming Languages},
volume = {5},
number = {POPL},
year = {2021},
doi = {10.1145/3434330}
}