PortSmash – A New Side Channel Vulnerability in SMT/Hyper-Threading That Allows Attackers To Steal Sensitive Data

Researchers discovered a new critical side-channel vulnerability dubbed PortSmash that can allow attackers to steal from other simultaneous process running in the same CPU core with that has SMT/Hyper-Threading enabled.

The Simultaneous multithreading process is to improve the overall efficiency and reduces tile by carrying out a number of parallel computing tasks.

The vulnerability named PortSmash CVE-2018-5407 discovered by a group of researchers Billy Bob Brumley, Cesar Pereida Garcia, Sohaib ul Hassan, Nicola
Tuveri from Tampere University of Technology, Finland and
Alejandro Cabrera Aldaya from Universidad Tecnologica de la Habana CUJAE, Cuba.

Researchers tested and confirmed vulnerability with Skylake and Kaby Lake processers, they are able to recover the elliptic curve private key from an OpenSSL-powered TLS server.

We able to detect a port carry out timing side-channel attack to exfiltrate a private key from processes running in parallel on the same CPU core. To exploit the vulnerability root permission is not required, researchers said.

Billy Brumley said, “Our attack has nothing to do with the memory subsystem or caching, the nature of the leakage is due to execution engine sharing on SMT (e.g. Hyper-Threading) architectures.”

Researchers also published proof-of-concept (PoC) on Github that targets the OpenSSL, the library addressed the flaw in OpenSSL 1.1.0h or lower. the exploit code was written in x64 assembly that runs locally on a vulnerable machine.

“We steal an OpenSSL (<= 1.1.0h) P-384 private key from a TLS server using this new side-channel vector. It is a local attack in the sense that the malicious process must be running on the same physical core as the victim,” reads Security Advisory.

Affected Software/hardware

SMT/Hyper-Threading architectures Skylake and Kaby Lake verified by researchers and they expect to work with AMD Ryzen.

OpenSSL – 1.1.0h & Ubuntu 18.04 affected with the vulnerability.

Fix for PortSmash

To fix the vulnerability researchers suggested upgrading with the OpenSSL 1.1.1 or 1.1.0i to fix the issue.

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