It's a Feature, Not a Bug: Secure and Auditable State Rollback for Confidential Cloud Applications

TL;DR

Rebound is a general-purpose security framework that preserves rollback protection while enabling policy-authorized legitimate rollbacks of application binaries, configuration, and data and emits a tamper-evident log that provides transparency to applications and auditors.

Abstract

Replay and rollback attacks threaten cloud application integrity by reintroducing authentic yet stale data through an untrusted storage interface to compromise application decision-making. Prior security frameworks mitigate these attacks by enforcing forward-only state transitions (state continuity) with hardware-backed mechanisms, but they categorically treat all rollback as malicious and thus preclude legitimate rollbacks used for operational recovery from corruption or misconfiguration. We present Rebound, a general-purpose security framework that preserves rollback protection while enabling policy-authorized legitimate rollbacks of application binaries, configuration, and data. Key to Rebound is a reference monitor that mediates state transitions, enforces authorization policy, guarantees atomicity of state updates and rollbacks, and emits a tamper-evident log that provides transparency to applications and auditors. We formally prove Rebound's security properties and show through an application case study -- with software deployment workflows in GitLab CI -- that it enables robust control over binary, configuration, and raw data versioning with low end-to-end overhead.

Figures (13)

• Figure 1: Confidential applications run inside TEEs on untrusted cloud infrastructure. The TEE protects code and data in memory and must check data integrity and freshness when reading/writing to storage.
• Figure 2:
• Figure 3: Rebound high-level system architecture.
• Figure 4: In Rebound, rollback is represented and executed as a forward state transition that creates a new state and records lineage metadata (i.e., origin pointer) that can be used by auditors to reconstruct lineage.
• Figure 5: Rebound uses a tailored authenticated dictionary to accumulate prior object versions and policy provenance under the authoritative root $R$.