Dorami: Privilege Separating Security Monitor on RISC-V TEEs

TL;DR

Dorami introduces a privilege separation method for RISC-V TEEs that isolates the security monitor from firmware, reducing attack surface with minimal overhead by leveraging existing ISA features.

Contribution

It presents Dorami, a novel privilege separation approach that isolates the security monitor from firmware in RISC-V TEEs, enhancing security without significant performance costs.

Findings

Reduces attack surface of RISC-V TEEs

Achieves isolation with minimal overhead

Leverages existing ISA features effectively

Abstract

TEE implementations on RISC-V offer an enclave abstraction by introducing a trusted component called the security monitor (SM). The SM performs critical tasks such as isolating enclaves from each other as well as from the OS by using privileged ISA instructions that enforce the physical memory protection. However, the SM executes at the highest privilege layer on the platform (machine-mode) along side firmware that is not only large in size but also includes third-party vendor code specific to the platform. In this paper, we present Dorami - a privilege separation approach that isolates the SM from the firmware thus reducing the attack surface on TEEs. Dorami re-purposes existing ISA features to enforce its isolation and achieves its goals without large overheads.