Last-Level Cache Side-Channel Attacks Are Feasible in the Modern Public Cloud (Extended Version)

TL;DR

This paper demonstrates that last-level cache side-channel attacks are feasible in modern cloud environments, introducing new techniques to overcome noise and limited attack windows, successfully extracting sensitive data in real-world cloud settings.

Contribution

The paper presents novel techniques for cache eviction, high-resolution monitoring, and frequency domain analysis to enable practical side-channel attacks in cloud environments.

Findings

Achieved 81% extraction of secret bits in 19 seconds

Developed new methods for eviction set generation and victim monitoring

Proved feasibility of cache attacks in noisy, multi-tenant cloud settings

Abstract

Last-level cache side-channel attacks have been mostly demonstrated in highly-controlled, quiescent local environments. Hence, it is unclear whether such attacks are feasible in a production cloud environment. In the cloud, side channels are flooded with noise from activities of other tenants and, in Function-as-a-Service (FaaS) workloads, the attacker has a very limited time window to mount the attack. In this paper, we show that such attacks are feasible in practice, although they require new techniques. We present an end-to-end, cross-tenant attack on a vulnerable ECDSA implementation in the public FaaS Google Cloud Run environment. We introduce several new techniques to improve every step of the attack. First, to speed-up the generation of eviction sets, we introduce L2-driven candidate address filtering and a Binary Search-based algorithm for address pruning. Second, to monitor victim memory accesses with high time resolution, we introduce Parallel Probing. Finally, we leverage power spectral density from signal processing to easily identify the victim's target cache set in the frequency domain. Overall, using these mechanisms, we extract a median value of 81% of the secret ECDSA nonce bits from a victim container in 19 seconds on average.