03 April 2017, 11:00, A6-007

Session chair: Mathias Payer, Purdue University, USA

Detecting Privileged Side-Channel Attacks in Shielded Execution with Déjà Vu

Sanchuan Chen, Xiaokuan Zhang, Michael K. Reiter, Yinqian Zhang

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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 Deja 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, Deja 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 Deja Vu effectively detects side-channel attacks against shielded execution and against the reference clock itself.

SGX-Log: Securing System Logs With SGX

Vishal Karande, Erick Buaman, Zhiqiang Lin, Latifur Khan

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System logs are the greatest forensics assets that capture how an operating system or a program behaves. System logs are often the next immediate attack target once a system is compromised, and it is thus paramount to protect them. This paper introduces SGX-Log, a new logging system that ensures the integrity and confidentiality of log data. The key idea is to redesign a logging system by leveraging a recent hardware extension, called Intel SGX, which provides a secure enclave with sealing and unsealing primitives to protect program code and data in both memory and disk from being modified in an unauthorized manner even from high privilege code. We have implemented SGX-Log atop the recent Ubuntu 14.04 for secure logging using real SGX hardware. Our evaluation shows that SGX-Log introduces no observable performance overhead to the programs that generate the log requests, and it also imposes very small overhead to the log daemons.

The Circle Game: Scalable Private Membership Test Using Trusted Hardware

Sandeep Tamrakar, Jian Liu, Andrew Paverd, Jan-Erik Ekberg, Benny Pinkas, N. Asokan

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Malware checking is changing from being a local service to a cloud-assisted one where users’ devices query a cloud server, which hosts a dictionary of malware signatures, to check if particular applications are potentially malware. Whilst such an architecture gains all the benefits of cloud-based services, it opens up a major privacy concern since the cloud service can infer personal traits of the users based on the lists of applications queried by their devices. Private membership test (PMT) schemes can remove this privacy concern. However, known PMT schemes do not scale well to a large number of simultaneous users and high query arrival rates. We propose a simple PMT approach using a carousel: circling the entire dictionary through trusted hardware on the cloud server. Users communicate with the trusted hardware via secure channels. We show how the carousel approach, using different data structures to represent the dictionary, can be realized on two different commercial hardware security architectures (ARM TrustZone and Intel SGX). We highlight subtle aspects of securely implementing seemingly simple PMT schemes on these architectures. Through extensive experimental analysis, we show that for the malware checking scenario our carousel approach surprisingly outperforms Path ORAM on the same hardware by supporting a much higher query arrival rate while guaranteeing acceptable response latency for individual queries.