Prime+Snoop : CXL.cache side channel attack by a rogue CXL device

다국어 초록 (Multilingual Abstract)

Compute Express Link (CXL) enables cache-coherent memory sharing between a host CPU and attached accelerators through its CXL.cache protocol. However, its asymmetric coherence model—where the host exclusively manages cache states—introduces a novel and unexplored attack surface.

We present Prime+Snoop, a side-channel attack that leverages CXL coherence messages as a high-fidelity leakage vector. In Prime+Snoop, a malicious CXL device (rCXL) primes a targeted set in the host’s cache directory by claiming ownership of selected memory addresses. When a victim process accesses addresses mapped to the set, the resulting eviction generates snoop invalidation packets from the host to the rCXL. By monitoring these coherence messages, the attacker obtains a precise, low-noise signal of the victim’s memory activity.

We demonstrate Prime+Snoop on a cycle-accurate gem5 simulator and show that the covert channel achieves a peak capacity of 1.35 Mbps, highlighting both efficiency and robustness. We further validate its impact by recovering private keys from a vulnerable RSA implementation, establishing Prime+Snoop as a concrete and severe security threat for emerging CXL-enabled systems.

목차 (Table of Contents)

• I. INTRODUCTION 1
• II. BACKGROUND 3
• III. RELATED WORK. 6
• IV. PRIME+SNOOP MECHANISM 10
• V. SIMULATOR ENVIRONMENT. 15
• VI. COVERT CHANNEL. 18
• VII. SIDE CHANNEL ATTACK 22
• VIII. MITIGATIONS. 27
• IX. CONCLUSION. 29