Twine: An Embedded Trusted Runtime for WebAssembly

WebAssembly is an Increasingly popular lightweight binary instruction format, which can be efficiently embedded and sandboxed. Languages like C, C++, Rust, Go, and many others can be compiled into WebAssembly. This paper describes Twine, a WebAssembly trusted runtime designed to execute unmodified, language-independent applications. We leverage Intel SGX to build the runtime environment without dealing with language-specific, complex APIs. While SGX hardware provides secure execution within the processor, Twine provides a secure, sandboxed software runtime nested within an SGX enclave, featuring a WebAssembly system interface (WASI) for compatibility with unmodified WebAssembly applications. We evaluate Twine with a large set of general-purpose benchmarks and real-world applications. In particular, we used Twine to implement a secure, trusted version of SQLite, a well-known full-fledged embeddable database. We believe that such a trusted database would be a reasonable component to build many larger application services. Our evaluation shows that SQLite can be fully executed inside an SGX enclave via WebAssembly and existing system interface, with similar average performance overheads. We estimate that the performance penalties measured are largely compensated by the additional security guarantees and its full compatibility with standard WebAssembly. An indepth analysis of our results indicates that performance can be greatly improved by modifying some of the underlying libraries. We describe and implement one such modification in the paper, showing up to 4.1 × speedup. Twine is open-source, available at GitHub along with instructions to reproduce our experiments.

I. Introduction

Trusted code execution is currently one of the major open challenges for distributed systems. Data is a key asset for many companies and the ability to execute code and process data out of premises is a prerequisite for outsourcing computing tasks, either to large data centres in the cloud or to the edge of the network on thin clients and IoT devices. Trusted execution environments (TEEs) such as Intel SGX [1], ARM TrustZone [2], AMD SME/SEV [3] and RISC-V Keystone [4] gathered much attention lately as they provide hardware support for secure code execution within special hardware constructs that are shielded from the outside world, including the operating system and privileged users. Still, despite the many frameworks and runtime environments that have been developed recently, programming applications for TEEs remains a complex task. Developers must generally use custom tools and APIs, and they are restricted to a few supported programming languages.