Confidential vms get fast secure persistent storage with cif protection
CVM-Store: A Secure Storage System for Confidential Virtual Machines
Cryptography and Security
Summary
Running sensitive programs in the cloud is risky because data saved on disk isn’t as protected as data in memory. The authors introduce CVM-Store, a way to securely save data from confidential virtual machines while keeping the speed close to that of direct hardware storage. They combine encryption, integrity checks, and freshness guarantees to prevent tampering or rollback without needing special hardware. The system tailors protection to different ways programs save data, making it efficient and secure.
What this means in practice
- •For cloud infrastructure teams: Enable high-speed secure storage for confidential workloads on untrusted cloud platforms with minimal performance loss.
- •For enterprise security teams: Protect stored sensitive data in virtual machines from rollback and tampering without requiring specialized hardware support.
Authors
Thore Sommer, Masanori Misono, Dimitrios Stavrakakis, Pramod Bhatotia
Abstract
Stateful cloud workloads require high-performance persistent storage when running on untrusted cloud infrastructure. Confidential Virtual Machines (CVMs) promise to protect these workloads through hardware-enforced memory encryption and isolation without requiring application changes. However, they protect only data in use; persistent storage lies outside the CVM trust boundary, exposing all stateful data to the cloud provider. Extending the trust boundary to persistent storage presents inherent challenges. High-bandwidth workloads require near-raw NVMe throughput, yet the default kernel CVM I/O stacks are inadequate, and userspace I/O libraries are not designed with CVM use cases in mind. Access patterns and storage semantics vary between workloads, necessitating access-pattern-aware security abstractions rather than uniform block-level encryption. In order to mitigate against rollback, freshness is needed, but CVMs lack hardware primitives for this purpose, requiring alternative solutions. We present CVM-Store, a storage system that co-designs a high-throughput userspace I/O engine with CIF (confidentiality, integrity, freshness) data protection. The key insight is that neither authenticated encryption nor I/O is a bottleneck by itself, but their naive combination is. CVM-Store exploits this by interleaving them, eliminating redundant copies and OS/hypervisor mediation. CIF guarantees are provided as composable primitives that adapt protection to workload access patterns, from which we derive three concrete authenticated abstractions: a KVS, a log, and a filesystem. An asynchronous trusted counter service provides freshness guarantees with epoch-based batching, which enables rollback protection without dedicated hardware support. CVM-Store delivers full CIF guarantees within $\approx$1% (write) and 1-19% (read) of raw NVMe bandwidth for large objects.