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Speculative execution attacks like Spectre and Meltdown exploit hardware performance optimization features to illegally access a secret and then leak the secret to an unauthorized recipient. Many variants of speculative execution attacks (also called transient execution attacks) have been proposed in the last few years, and new ones are constantly being discovered. While software mitigations for some attacks have been proposed, they often cause very significant performance degradation. Hardware solutions are also being proposed actively by the research community, especially as these are attacks on hardware microarchitecture. In this talk, we identify the critical steps in a speculative attack, and the root cause of successful attacks. We define the concept of "security dependencies", which should be implemented to prevent data leaks and other security breaches. We propose a taxonomy of defense strategies and show how proposed hardware defenses fall under each defense strategy. We discuss security-performance tradeoffs, which can decrease the performance overhead while still preventing security breaches. We suggest design principles for future security-aware microarchitecture.
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Position Paper: Consider Hardware-enhanced Defenses for Rootkit Attacks
Rootkits are malware that attempt to compromise the system’s functionalities while hiding their existence. Various rootkits have been proposed as well as different software defenses, but only very few hardware defenses. We position hardware-enhanced rootkit defenses as an interesting research opportunity for computer architects, especially as many new hardware defenses for speculative execution attacks are being actively considered. We first describe different techniques used by rootkits and their prime targets in the operating system. We then try to shed insights on what the main challenges are in providing a rootkit defense, and how these may be overcome. We show how a hypervisor-based defense can be implemented, and provide a full prototype implementation in an open-source cloud computing platform, OpenStack. We evaluate the performance overhead of different defense mechanisms. Finally, we point to some research opportunities for enhancing resilience to rootkit-like attacks in the hardware architecture.
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- Award ID(s):
- 1814190
- PAR ID:
- 10392198
- Date Published:
- Journal Name:
- HASP '20: Hardware and Architectural Support for Security and Privacy
- Page Range / eLocation ID:
- 1 to 9
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Speculative execution attacks leverage the speculative and out-of-order execution features in modern computer processors to access secret data or execute code that should not be executed. Secret information can then be leaked through a covert channel. While software patches can be installed for mitigation on existing hardware, these solutions can incur big performance overhead. Hardware mitigation is being studied extensively by the computer architecture community. It has the benefit of preserving software compatibility and the potential for much smaller performance overhead than software solutions. This paper presents a systematization of the hardware defenses against speculative execution attacks that have been proposed. We show that speculative execution attacks consist of 6 critical attack steps. We propose defense strategies, each of which prevents a critical attack step from happening, thus preventing the attack from succeeding. We then summarize 20 hardware defenses and overhead-reducing features that have been proposed. We show that each defense proposed can be classified under one of our defense strategies, which also explains why it can thwart the attack from succeeding. We discuss the scope of the defenses, their performance overhead, and the security-performance trade-offs that can be made.more » « less
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For many years there has been an arms race between designers and adversaries of secure hardware. Improvements in the strategies for attack spur new defense techniques, and better defenses lead to improved attacks. In this contribution, first, we examine the technological dimensions of this arms race. While defenders benefit from increased circuit density and decreasing feature size, attackers benefit from novel side-channel attack vectors based on optical and electromagnetic interactions with their target. Second, we analyze the feasibility and applicability of various side-channel attacks on primary units of cryptographic hardware. We also discuss the required time, cost, and expertise to mount these attacks. We then examine how well modern defense methods are capable of thwarting modern attack methods.more » « less
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Spectre and Meltdown attacks and their variants exploit hardware performance optimization features to cause security breaches. Secret information is accessed and leaked through covert or side channels. New attack variants keep appearing and we do not have a systematic way to capture the critical characteristics of these attacks and evaluate why they succeed or fail.In this paper, we provide a new attack-graph model for reasoning about speculative execution attacks. We model attacks as ordered dependency graphs, and prove that a race condition between two nodes can occur if there is a missing dependency edge between them. We define a new concept, “security dependency”, between a resource access and its prior authorization operation. We show that a missing security dependency is equivalent to a race condition between authorization and access, which is a root cause of speculative execution attacks. We show detailed examples of how our attack graph models the Spectre and Meltdown attacks, and is generalizable to all the attack variants published so far. This attack model is also very useful for identifying new attacks and for generalizing defense strategies. We identify several defense strategies with different performance-security tradeoffs. We show that the defenses proposed so far all fit under one of our defense strategies. We also explain how attack graphs can be constructed and point to this as promising future work for tool designersmore » « less
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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
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1145/3458903.3458909
