Side-channel attacks, such as Spectre and Meltdown, that leverage speculative execution pose a serious threat to computing systems. Worse yet, such attacks can be perpetrated by compromised operating system (OS) kernels to bypass defenses that protect applications from the OS kernel.
This work evaluates the performance impact of three different defenses against in-kernel speculation side-channel attacks within the context of Virtual Ghost, a system that protects user data from compromised OS kernels: Intel MPX bounds checks, which require a memory fence; address bit-masking and testing, which creates a dependence between the bounds check and the load/store; and the use of separate virtual address spaces for applications, the OS kernel, and the Virtual Ghost virtual machine, forcing a speculation boundary. Our results indicate that an instrumentation-based bit-masking approach to protection incurs the least overhead by minimizing speculation boundaries. Our work also highlights possible improvements to Intel MPX that could help mitigate speculation side-channel attacks at a lower cost.
more »
« less
Shielding Software From Privileged Side-Channel Attacks
Commodity operating system (OS) kernels, such as Windows, Mac OS X, Linux, and FreeBSD, are susceptible to numerous security vulnerabilities. Their monolithic design gives successful attackers complete access to all application data and system resources. Shielding systems such as InkTag, Haven, and Virtual Ghost protect sensitive application data from compromised OS kernels. However, such systems are still vulnerable to side-channel attacks. Worse yet, compromised OS kernels can leverage their control over privileged hardware state to exacerbate existing side channels; recent work has shown that a compromised OS kernel can steal entire documents via side channels.
This paper presents defenses against page table and last-level cache (LLC) side-channel attacks launched by a compromised OS kernel. Our page table defenses restrict the OS kernel’s ability to read and write page table pages and defend against page allocation attacks, and our LLC defenses utilize the Intel Cache Allocation Technology along with memory isolation primitives. We proto- type our solution in a system we call Apparition, building on an optimized version of Virtual Ghost. Our evaluation shows that our side-channel defenses add 1% to 18% (with up to 86% for one application) overhead to the optimized Virtual Ghost (relative to the native kernel) on real-world applications.
more »
« less
- Award ID(s):
- 1652280
- PAR ID:
- 10094849
- Date Published:
- Journal Name:
- Proceedings of the Twenty Seventh Usenix Security Symposium
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Last-Level Cache (LLC) attacks typically exploit timing side channels in hardware, and thus rely heavily on timers for their operation. Many proposed defenses against such side-channel attacks capitalize on this reliance. This paper presents PRIME+ABORT, a new cache attack which bypasses these defenses by not depending on timers for its function. Instead of a timing side channel, PRIME+ABORT leverages the Intel TSX hardware widely available in both server- and consumer-grade processors. This work shows that PRIME+ABORT is not only invulnerable to important classes of defenses, it also outperforms state-of-the-art LLC PRIME+PROBE attacks in both accuracy and efficiency, having a maximum detection speed (in events per second) 3× higher than LLC PRIME+PROBE on Intel’s Skylake architecture while producing fewer false positives.more » « less
-
Intel Software Guard Extension (SGX) protects the confidentiality and integrity of an unprivileged program running inside a secure enclave from a privileged attacker who has full control of the entire operating system (OS). Program execution inside this enclave is therefore referred to as shielded. Unfortunately, shielded execution does not protect programs from side-channel attacks by a privileged attacker. For instance, it has been shown that by changing page table entries of memory pages used by shielded execution, a malicious OS kernel could observe memory page accesses from the execution and hence infer a wide range of sensitive information about it. In fact, this page-fault side channel is only an instance of a category of side-channel attacks, here called privileged side-channel attacks, in which privileged attackers frequently preempt the shielded execution to obtain fine-grained side-channel observations. In this paper, we present Déjà Vu, a software framework that enables a shielded execution to detect such privileged side-channel attacks. Specifically, we build into shielded execution the ability to check program execution time at the granularity of paths in its control-flow graph. To provide a trustworthy source of time measurement, Déjà Vu implements a novel software reference clock that is protected by Intel Transactional Synchronization Extensions (TSX), a hardware implementation of transactional memory. Evaluations show that Déjà Vu effectively detects side-channel attacks against shielded execution and against the reference clock itself.more » « less
-
The security of isolated execution architectures such as Intel SGX has been significantly threatened by the recent emer- gence of side-channel attacks. Cache side-channel attacks allow adversaries to leak secrets stored inside isolated en- claves without having direct access to the enclave memory. In some cases, secrets can be leaked even without having the knowledge of the victim application code or having OS-level privileges. We propose the concept of Composable Cachelets (CC), a new scalable strategy to dynamically partition the last-level cache (LLC) for completely isolating enclaves from other applications and from each other. CC supports enclave isolation in caches with the capability to dynamically readjust the cache capacity as enclaves are created and destroyed. We present a cache-aware and enclave-aware operational seman- tics to help rigorously establish security properties of CC, and we experimentally demonstrate that CC thwarts side-channel attacks on caches with modest performance and complexity impact.more » « less
-
null (Ed.)Cache side-channel attacks aim to breach the confidentiality of a computer system and extract sensitive secrets through CPU caches. In the past years, different types of side-channel attacks targeting a variety of cache architectures have been demonstrated. Meanwhile, different defense methods and systems have also been designed to mitigate these attacks. However, quantitatively evaluating the effectiveness of these attacks and defenses has been challenging. We propose a generic approach to evaluating cache side-channel attacks and defenses. Specifically, our method builds a deep neural network with its inputs as the adversary's observed information, and its outputs as the victim's execution traces. By training the neural network, the relationship between the inputs and outputs can be automatically discovered. As a result, the prediction accuracy of the neural network can serve as a metric to quantify how much information the adversary can obtain correctly, and how effective a defense solution is in reducing the information leakage under different attack scenarios. Our evaluation suggests that the proposed method can effectively evaluate different attacks and defenses.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
