DMA Security in the Presence of IOMMUs

Faulty, vulnerable or malicious PCIe devices can harm a system through DMA. IOMMUs can act as a security mechanism to protect against this problem by restricting the memory that is accessible via DMA. Unfortunately, there exist methods to bypass the IOMMU restrictions. This can be exploited from any untrusted source of DMA, which includes peripheral PCIe devices, virtual machines using SR-IOV, and even RDMA network cards which enable remote attacks. Key strategies for the attacks presented here are Rowhammer, cache side-channels, and the exploitation of weaknesses in protocols like PCIe or Ethernet OAM, or device drivers e.g. for network cards. An attacker can potentially break all the CIA principles and achieve denial of service, the reading of confidential data, and even arbitrary code execution in some cases. Fortunately, there are some precautions to reduce the risks for affected systems. The focus will be on plattforms based on the Linux kernel, running on hardware with the x86 architecture and Intel’s IOMMU implementation (VT-d).

(Hauptseminar)