Transient execution is one of the most critical features used in CPUs to achieve high performance. Recent Spectre attacks demonstrated how this feature can be manipulated to force applications to reveal sensitive data. The industry quickly responded with a series of software and hardware mitigations among which microcode patches are the most prevalent and trusted. In this paper, we argue that currently deployed protections still leave room for constructing attacks. We do so by presenting transient trojans, software modules that conceal their malicious activity within transient execution mode. They appear completely benign, pass static and dynamic analysis checks, but reveal sensitive data when triggered. To construct these trojans, we perform a detailed analysis of the attack surface currently present in today's systems with respect to the recommended mitigation techniques. We reverse engineer branch predictors in several recent x86_64 processors which allows us to uncover previously unknown exploitation techniques. Using these techniques, we construct three types of transient trojans and demonstrate their stealthiness and practicality.
more »
« less
Verification of serialising instructions for security against transient execution attacks
Transient execution attacks such as Spectre and Meltdown exploit speculative execution in modern microprocessors to leak information via cache side‐channels. Software solutions to defend against many transient execution attacks employ the
- Award ID(s):
- 2117190
- NSF-PAR ID:
- 10416662
- Publisher / Repository:
- DOI PREFIX: 10.1049
- Date Published:
- Journal Name:
- IET Computers & Digital Techniques
- Volume:
- 17
- Issue:
- 3-4
- ISSN:
- 1751-8601
- Page Range / eLocation ID:
- p. 127-140
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
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
-
Memory safety invariants extracted from a program can help defend and detect against both software and hardware memory violations. For instance, by allowing only specific instructions to access certain memory locations, system can detect out-of-bound or illegal pointer dereferences that lead to correctness and security issues. In this paper, we propose CPU abstractions, called, to specify and check program invariants to provide defense mechanism against both software and hardware memory violations at runtime. ensures that the invariants must be satisfied at every memory accesses. We present a fast invariant address translation and retrieval scheme using a specialized cache. It stores and checks invariants related to global, stack and heap objects. The invariant checks can be performed synchronously or asynchronously. uses synchronous checking for high security-critical programs, while others are protected by asynchronous checking. A fast exception is proposed to alert any violations as soon as possible in order to close the gap for transient attacks. Our evaluation shows that can detect both software and hardware, spatial and temporal memory violations. incurs 53% overhead when checking synchronously, or 15% overhead when checking asynchronously.more » « less
-
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.more » « less
-
null (Ed.)Due to the globalization of semiconductor manufacturing and test processes, the system-on-a-chip (SoC) designers no longer design the complete SoC and manufacture chips on their own. This outsourcing of the design and manufacturing of Integrated Circuits (ICs) has resulted in several threats, such as overproduction of ICs, sale of out-of-specification/rejected ICs, and piracy of Intellectual Properties (IPs). Logic locking has emerged as a promising defense strategy against these threats. However, various attacks about the extraction of secret keys have undermined the security of logic locking techniques. Over the years, researchers have proposed different techniques to prevent existing attacks. In this article, we propose a novel attack that can break any logic locking techniques that rely on the stored secret key. This proposed TAAL attack is based on implanting a hardware Trojan in the netlist, which leaks the secret key to an adversary once activated. As an untrusted foundry can extract the netlist of a design from the layout/mask information, it is feasible to implement such a hardware Trojan. All three proposed types of TAAL attacks can be used for extracting secret keys. We have introduced the models for both the combinational and sequential hardware Trojans that evade manufacturing tests. An adversary only needs to choose one hardware Trojan out of a large set of all possible Trojans to launch the TAAL attack.more » « less
