Speculation Invariance (InvarSpec): Faster Safe Execution Through Program Analysis

Zhao, Zirui; Ji, Houxiang; Yan, Mengjia; Yu, Jun; Fletcher, Christopher W.; Morrison, Adam; Marinov, Darko; Torrellas, Josep

doi:10.1109/micro50266.2020.00094

Cited by 20 publications

(17 citation statements)

References 37 publications

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“…The sample set of fifteen co-running benchmark applications are selected from the SPEC2017rate suite [16]. For each SPEC application, we utilize the SimPoint methodology [21] to run up to 10 representative intervals of 50 million instructions each to accurately reflect the application's performance [35]. The caches are populated prior to interval data collection using 1 million warm-up instructions, and all simulations are run using gem5's system call emulation mode.…”

Section: Evaluation 61 Experimental Setupmentioning

confidence: 99%

DAGguise: mitigating memory timing side channels

Deutsch

Yang

Bourgeat

et al. 2022

Proceedings of the 27th ACM International Conference on Architectural Support for Programming Languages and Operating Systems

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This paper studies the mitigation of memory timing side channels, where attackers utilize contention within DRAM controllers to infer a victim's secrets. Already practical, this class of channels poses an important challenge to secure computing in shared memory environments.Existing state-of-the-art memory timing side channel mitigations have several key performance and security limitations. Prior schemes require onerous static bandwidth partitioning, extensive profiling phases, or simply fail to protect against attacks which exploit fine-grained timing and bank information.We present DAGguise, a defense mechanism which fully protects against memory timing side channels while allowing for dynamic traffic contention in order to achieve good performance. DAGguise utilizes a novel abstract memory access representation, the Directed Acyclic Request Graph (𝑟 DAG for short), to model memory access patterns which experience contention. DAGguise shapes a victim's memory access patterns according to a publicly known 𝑟 DAG obtained through a lightweight profiling stage, completely eliminating information leakage.We formally verify the security of DAGguise, proving that it maintains strong security guarantees. Moreover, by allowing dynamic traffic contention, DAGguise achieves a 12% overall system speedup relative to Fixed Service, which is the state-of-the-art mitigation mechanism, with up to a 20% relative speedup for co-located applications which do not require protection. We further claim that the principles of DAGguise can be generalized to protect against other types of scheduler-based timing side channels, such as those targeting on-chip networks, or functional units in SMT cores. CCS CONCEPTS• Security and privacy → Side-channel analysis and countermeasures.

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Section: Evaluation 61 Experimental Setupmentioning

confidence: 99%

DAGguise: mitigating memory timing side channels

Deutsch

Yang

Bourgeat

et al. 2022

Proceedings of the 27th ACM International Conference on Architectural Support for Programming Languages and Operating Systems

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“…InvarSpec is not itself a speculative side-channel defense but rather a framework that detects when a speculative instruction becomes speculation invariant and upon detection lifts any existing protections for the instruction [16]. InvarSpec consists of two main parts.…”

Section: B Speculation Invariance: Invarspecmentioning

confidence: 99%

“…Each instruction has its safe set (SS) defined by the compiler and corresponds to the instruction's control and data dependencies on the instructions in the set [16].…”

Section: B Speculation Invariance: Invarspecmentioning

confidence: 99%

“…Hardware defenses, such as DoM and InvisiSpec, add significant performance overhead [10], [12]. For this, Zhao et al proposed InvarSpec [16], a framework that detects and lifts the protection for speculative instructions that become speculation invariant. For an instruction to be speculative invariant, its data and control dependencies must be resolved during the speculation window.…”

Section: Introductionmentioning

confidence: 99%

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"It's a Trap!"-How Speculation Invariance Can Be Abused with Forward Speculative Interference

Aimoniotis¹,

Sakalis²,

Själander³

2021

Preprint

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Side-channel attacks based on speculative execution access sensitive data and use transmitters to leak such data during wrongpath execution. Speculative side-channel defenses have been proposed to prevent such information leakage. In one class of defenses, speculative instructions are considered unsafe and are delayed until they become non-speculative.However, not all speculative instructions are unsafe: Recent work demonstrates that speculative invariant instructions are independent of a speculative control-flow path and are guaranteed to eventually execute and commit, regardless of the outcome of the performed speculation. Compile time information coupled with run-time mechanisms can then selectively lift defenses for Speculative Invariant instructions, regaining some of the performance lost to "delay" defenses.Unfortunately, speculative invariance can be easily mishandled with Speculative Interference to leak information using a new side-channel that we introduce in this paper. Recent work shows that younger speculative instructions can interfere with older non-speculative instructions that are bound to commit. This "backward" speculative interference reveals speculatively accessed secrets through the non-speculative instructions, in a way that delay-defenses do not cover, rendering them ineffective for this type of attack.In our work, we show that the counterpart to backward speculative interference, i.e., forward speculative interference, enables older speculative instructions to interfere with younger speculative-invariant (bound-tocommit) instructions, effectively turning them into transmitters for secret data accessed during speculation. We demonstrate forward speculative interference on real hardware, by selectively filling the reorder buffer (ROB) with spurious instructions, pushing speculative-invariant instructions inor-out the ROB on demand, based on a speculatively accessed secret. This reveals the speculatively accessed secret, as the occupancy of the ROB itself becomes a new speculative side-channel. We also demonstrate that it is possible to use the x86 ISA REP prefix, which unrolls as a micro-op loop in the microarchitecture at decode time (before any sidechannel defenses have taken effect), as a method for generating spurious instructions. We propose several mitigations that range from changing compile-time decisions for speculative-invariance to run-time mechanisms that aim to make ROB occupancy operand-independent.

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“…In the most naïve approach, we can consider handles to be safe when they reach the head of the ROB and are retired, but this is awfully pessimistic. Instead, we draw from the existing research on speculative execution [3,6,[37][38][39]50,56] and consider handles as safe when they can no longer cause squashing, regardless of their position in the ROB. Specifically, we have adopted the approach of using speculative shadows by Sakalis et al [37][38][39], a mechanism for detecting the earliest point at which an instruction is no longer speculative.…”

Section: Handles and The Window Of Speculationmentioning

confidence: 99%

Selectively Delaying Instructions to Prevent Microarchitectural Replay Attacks

Sakalis,

Kaxiras,

Själander

2021

Preprint

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MicroScope, and microarchitectural replay attacks in general, take advantage of the characteristics of speculative execution to trap the execution of the victim application in an infinite loop, enabling the attacker to amplify a side-channel attack by executing it indefinitely. Due to the nature of the replay, it can be used to effectively attack security critical trusted execution environments (secure enclaves), even under conditions where a side-channel attack would not be possible. At the same time, unlike speculative side-channel attacks, MicroScope can be used to amplify the correct path of execution, rendering many existing speculative side-channel defences ineffective.In this work, we generalize microarchitectural replay attacks beyond MicroScope and present an efficient defence against them. We make the observation that such attacks rely on repeated squashes of so-called "replay handles" and that the instructions causing the side-channel must reside in the same reorder buffer window as the handles. We propose Delay-on-Squash, a technique for tracking squashed instructions and preventing them from being replayed by speculative replay handles. Our evaluation shows that it is possible to achieve full security against microarchitectural replay attacks with very modest hardware requirements, while still maintaining 97% of the insecure baseline performance.

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Speculation Invariance (InvarSpec): Faster Safe Execution Through Program Analysis

Cited by 20 publications

References 37 publications

DAGguise: mitigating memory timing side channels

DAGguise: mitigating memory timing side channels

"It's a Trap!"-How Speculation Invariance Can Be Abused with Forward Speculative Interference

Selectively Delaying Instructions to Prevent Microarchitectural Replay Attacks

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