Malware Guard Extension: Using SGX to Conceal Cache Attacks

TL;DR

This paper demonstrates a novel malware attack on Intel SGX enclaves that uses cache side-channel techniques to extract RSA private keys, even with SGX protections in place, highlighting security vulnerabilities.

Contribution

It introduces the first malware running on real SGX hardware that exploits SGX features to conceal cache side-channel attacks targeting co-located enclaves.

Findings

Successfully extracted 96% of RSA private key from a single trace

Automated attack recovered full RSA key within 5 minutes from 11 traces

Demonstrated cache attacks across Docker containers on SGX hardware

Abstract

In modern computer systems, user processes are isolated from each other by the operating system and the hardware. Additionally, in a cloud scenario it is crucial that the hypervisor isolates tenants from other tenants that are co-located on the same physical machine. However, the hypervisor does not protect tenants against the cloud provider and thus the supplied operating system and hardware. Intel SGX provides a mechanism that addresses this scenario. It aims at protecting user-level software from attacks from other processes, the operating system, and even physical attackers. In this paper, we demonstrate fine-grained software-based side-channel attacks from a malicious SGX enclave targeting co-located enclaves. Our attack is the first malware running on real SGX hardware, abusing SGX protection features to conceal itself. Furthermore, we demonstrate our attack both in a native environment and across multiple Docker containers. We perform a Prime+Probe cache side-channel attack on a co-located SGX enclave running an up-to-date RSA implementation that uses a constant-time multiplication primitive. The attack works although in SGX enclaves there are no timers, no large pages, no physical addresses, and no shared memory. In a semi-synchronous attack, we extract 96% of an RSA private key from a single trace. We extract the full RSA private key in an automated attack from 11 traces within 5 minutes.