SIGY: Breaking Intel SGX Enclaves with Malicious Exceptions & Signals

TL;DR

SIGY is a novel attack exploiting Intel SGX's exception handling to inject fake signals, compromising enclave confidentiality and integrity across multiple runtimes, languages, and real-world applications.

Contribution

This paper introduces SIGY, a new attack vector on Intel SGX that manipulates exception handling to breach enclave security guarantees.

Findings

7 runtimes and library OSes are vulnerable to SIGY

8 programming languages in SGX are susceptible to SIGY

Demonstrated 4 proof-of-concept exploits on webservers and data workloads

Abstract

User programs recover from hardware exceptions and respond to signals by executing custom handlers that they register specifically for such events. We present SIGY attack, which abuses this programming model on Intel SGX to break the confidentiality and integrity guarantees of enclaves. SIGY uses the untrusted OS to deliver fake hardware events and injects fake signals in an enclave at any point. Such unintended execution of benign program-defined handlers in an enclave corrupts its state and violates execution integrity. 7 runtimes and library OSes (OpenEnclave, Gramine, Scone, Asylo, Teaclave, Occlum, EnclaveOS) are vulnerable to SIGY. 8 languages supported in Intel SGX have programming constructs that are vulnerable to SIGY. We use SIGY to demonstrate 4 proof of concept exploits on webservers (Nginx, Node.js) to leak secrets and data analytics workloads in different languages (C and Java) to break execution integrity.