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.
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Maya: Using Formal Control to Obfuscate Power Side Channels
The security of computers is at risk because of information leaking through their power consumption. Attackers can use advanced signal measurement and analysis to recover sensitive data from this side channel. To address this problem, this paper presents Maya, a simple and effective defense against power side channels. The idea is to use formal control to re-shape the power dissipated by a computer in an application-transparent manner—preventing attackers from learning any information about the applications that are running. With formal control, a controller can reliably keep power close to a desired target function even when runtime conditions change unpredictably. By selecting the target function intelligently, the controller can make power to follow any desired shape, appearing to carry activity information which, in reality, is unrelated to the application. Maya can be implemented in privileged software, firmware, or simple hardware. In this paper, we implement Maya on three machines using privileged threads only, and show its effectiveness and ease of deployment. Maya has already thwarted a newly-developed remote power attack.
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- Award ID(s):
- 1763658
- PAR ID:
- 10227437
- Date Published:
- Journal Name:
- International Conference on Computer Architecture (ISCA)
- Volume:
- 1
- Issue:
- 1
- Page Range / eLocation ID:
- 234-248
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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