SERVAS! Secure Enclaves via RISC-V Authenticryption Shield

TL;DR

This paper introduces SERVAS, a novel RISC-V enclave architecture that uses an authenticryption shield for cryptographic isolation, enabling efficient secure memory sharing with significantly reduced overhead compared to existing solutions.

Contribution

It proposes the authenticryption shield primitive for unified security policies and designs SERVAS, a RISC-V enclave system with improved security and efficiency for memory sharing.

Findings

SERVAS achieves secure enclave memory sharing with low overhead.

The authenticryption shield provides cryptographic isolation guarantees.

Enclave entry/exit overhead is significantly reduced compared to Intel SGX.

Abstract

Isolation is a long-standing challenge of software security. Traditional privilege rings and virtual memory are more and more augmented with concepts such as capabilities, protection keys, and powerful enclaves. At the same time, we are evidencing an increased need for physical protection, shifting towards full memory encryption schemes. This results in a complex interplay of various security mechanisms, increasing the burden for system architects and security analysts. In this work, we tackle the isolation challenge with a new isolation primitive called authenticryption shield that unifies both traditional and advanced isolation policies while offering the potential for future extensibility. At the core, we build upon an authenticated memory encryption scheme that gives cryptographic isolation guarantees and, thus, streamlines the security reasoning. We showcase the versatility of our approach by designing and prototyping SERVAS -- an innovative enclave architecture for RISC-V. Unlike current enclave systems, SERVAS facilitates efficient and secure enclave memory sharing. While the memory encryption constitutes the main overhead, entering or exiting a SERVAS enclave requires only 3.5x of a simple syscall, instead of 71x for Intel SGX.