Program obfuscation is a popular cryptographic construct with a wide range of uses such as IP theft prevention. Although cryptographic solutions for program obfuscation impose impractically high overheads, a recent breakthrough leveraging trusted hardware has shown promise. However, the existing solution is based on special-purpose trusted hardware, restricting its use-cases to a limited few.
In this paper, we first study if such obfuscation is feasible based on commodity trusted hardware, Intel SGX, and we observe that certain important security considerations are not
afforded by commodity hardware. In particular, we found that existing obfuscation/obliviousness schemes are insecure if directly applied to Intel SGX primarily due to side-channel limitations. To this end, we present OBFUSCURO, the first system providing
program obfuscation using commodity trusted hardware, Intel SGX. The key idea is to leverage ORAM operations to perform secure code execution and data access. Initially, OBFUSCURO transforms the regular program layout into a side-channel secure and ORAM-compatible layout. Then, OBFUSCURO ensures that its ORAM controller performs data oblivious accesses in order to protect itself from all memory-based side-channels.
Furthermore, OBFUSCURO ensures that the program is secure from timing attacks by ensuring that the program always runs for a pre-configured time interval. Along the way, OBFUSCURO also introduces a systematic optimization such as register-based ORAM stash. We provide a thorough security analysis of OBFUSCURO along with empirical attack evaluations showing that OBFUSCURO can protect the SGX program execution from
being leaked by access pattern-based and timing-based channels. We also provide a detailed performance benchmark results in order to show the practical aspects of OBFUSCURO.
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ENCIDER: Detecting Timing and Cache Side Channels in SGX Enclaves and Cryptographic APIs
Confidential computing aims to secure the code and data in use by providing a Trusted Execution Environment (TEE) for applications using hardware features such as Intel SGX.Timing and cache side-channel attacks, however, are often outside the scope of the threat model, although once exploited they are able to break all the default security guarantees enforced by hardware. Unfortunately, tools detecting potential side-channel vulnerabilities within applications are limited and usually ignore the strong attack model and the unique programming model imposed by Intel SGX. This paper proposes a precise side-channel analysis tool, ENCIDER, detecting both timing and cache side-channel vulnerabilities within SGX applications via inferring potential timing observation points and incorporating the SGX programming model into analysis. ENCIDER uses dynamic symbolic execution to decompose the side-channel requirement based on the bounded non-interference property and implements byte-level information flow tracking via API modeling. We have applied ENCIDER to 4 real-world SGX applications, 2 SGX crypto libraries, and 3 widely-used crypto libraries, and found 29 timing side channels and 73 code and data cache side channels. We have reported our findings to the corresponding parties, e.g., Intel and ARM, who have confirmed most of the vulnerabilities detected.
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- NSF-PAR ID:
- 10344244
- Date Published:
- Journal Name:
- IEEE Transactions on Dependable and Secure Computing
- ISSN:
- 1545-5971
- Page Range / eLocation ID:
- 1 to 1
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Speculative-execution attacks, such as SgxSpectre, Foreshadow, and MDS attacks, leverage recently disclosed CPU hardware vulnerabilities and micro-architectural side channels to breach the confidentiality and integrity of Intel Software Guard eXtensions (SGX). Unlike traditional micro-architectural side-channel attacks, speculative-execution attacks extract any data in the enclave memory, which makes them very challenging to defeat purely from the software. However, to date, Intel has not completely mitigated the threats of speculative-execution attacks from the hardware. Hence, future attack variants may emerge. This paper proposes a software-based solution to speculative-execution attacks, even with the strong assumption that confidentiality of enclave memory is compromised. Our solution extends an existing work called HyperRace, which is a compiler-assisted tool for detecting Hyper-Threading based side-channel attacks against SGX enclaves, to thwart speculative-execution attacks from within SGX enclaves. It requires supports from the untrusted operating system, e.g., for temporarily disabling interrupts, but verifies the OS's behaviors. Additional microcode upgrades are required from Intel to secure the attestation flow.more » « less
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Speculative execution side-channel vulnerabilities in micro-architecture processors have raised concerns about the security of Intel SGX. To understand clearly the security impact of this vulnerability against SGX, this paper makes the following studies: First, to demonstrate the feasibility of the attacks, we present SgxPectre Attacks (the SGX-variants of Spectre attacks) that exploit speculative execution side-channel vulnerabilities to subvert the confidentiality of SGX enclaves. We show that when the branch prediction of the enclave code can be influenced by programs outside the enclave, the control flow of the enclave program can be temporarily altered to execute instructions that lead to observable cache-state changes. An adversary observing such changes can learn secrets inside the enclave memory or its internal registers, thus completely defeating the confidentiality guarantee offered by SGX. Second, to determine whether real-world enclave programs are impacted by the attacks, we develop techniques to automate the search of vulnerable code patterns in enclave binaries using symbolic execution. Our study suggests that nearly any enclave program could be vulnerable to SgxPectre Attacks since vulnerable code patterns are available in most SGX runtimes (e.g., Intel SGX SDK, Rust-SGX, and Graphene-SGX). Third, we apply SgxPectre Attacks to steal seal keys and attestation keys from Intel signed quoting enclaves. The seal key can be used to decrypt sealed storage outside the enclaves and forge valid sealed data; the attestation key can be used to forge attestation signatures. For these reasons, SgxPectre Attacks practically defeat SGX's security protection. Finally, we evaluate Intel's existing countermeasures against SgxPectre Attacks and discusses the security implications.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1109/TDSC.2022.3160346
