Continued expansion of cloud computing offerings now includes SmartSSDs. A SmartSSD is a solid-state disk (SSD) augmented with an FPGA. Through public cloud providers, it is now possible to rent on-demand virtual machines enabled with SmartSSDs. Because of the FPGA component of the SmartSSD, cloud users who access the SmartSSD can instantiate custom circuits within the FPGA. This includes possibly malicious circuits for measurement of power and temperature. Normally, cloud users have no remote access to power and temperature data, but with SmartSSDs they could abuse the FPGA component to learn this information. This paper shows for the first time that heat generated by a cloud user accessing the SSD component of the SmartSSD and the resulting temperature increase, can be measured by a different cloud user accessing the FPGA component of the same SmartSSD by using the ring oscillators circuits to measure temperature. The thermal state remains elevated for a few minutes after the SSD is heated up and can be measured from the FPGA side by a subsequent user for up to a few minutes after the SSD heating is done. Further, in a future multi-tenant SmartSSD setting, the thermal changes can be measured in parallel if one user controls the SSD and the other the FPGA. Based on this temporal thermal state of the SmartSSD, a novel thermal communication channel is demonstrated for the first time.

翻译：云计算服务的持续扩展如今包括了SmartSSD。SmartSSD是一种配备FPGA的固态硬盘（SSD）。通过公有云提供商，用户现在能够按需租用启用SmartSSD的虚拟机。由于SmartSSD中FPGA组件的存在，访问SmartSSD的云用户可以在FPGA内实例化自定义电路，其中可能包括用于测量功率和温度的恶意电路。通常，云用户无法远程访问功率和温度数据，但借助SmartSSD，他们可能滥用FPGA组件获取此类信息。本文首次证明：访问SmartSSD中SSD组件的云用户产生的热量及其导致的温度升高，可由访问同一个SmartSSD中FPGA组件的另一云用户通过环形振荡器电路测量温度而检测到。该热状态在SSD升温后可持续数分钟，且可在SSD发热结束后从FPGA端被后续用户测量长达数分钟。此外，在未来多租户SmartSSD场景中，若一个用户控制SSD而另一个控制FPGA，热变化可被并行测量。基于SmartSSD的瞬态热状态，本文首次展示了一种新颖的热通信信道。