You shall not (by)pass!: practical, secure, and fast PKU-based sandboxing

VOULIMENEAS ALEXIOS, Jonas Vinck, Ruben Mechelinck, Stijn Volckaert

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

20 Citations (Scopus)

Abstract

Memory Protection Keys for Userspace (PKU) is a recent hardware feature that allows programs to assign virtual memory pages to protection domains, and to change domain access permissions using inexpensive, unprivileged instructions. Several in-process memory isolation approaches leverage this feature to prevent untrusted code from accessing sensitive program state and data. Typically, PKU-based isolation schemes need to be used in conjunction with mitigations such as CFI because untrusted code, when compromised, can otherwise bypass the PKU access permissions using unprivileged instructions or operating system APIs. Recently, researchers proposed fully self-contained PKU-based memory isolation schemes that do not rely on other mitigations. These systems use exploit-proof call gates to transfer control between trusted and untrusted code, as well as a sandbox that prevents tampering with the PKU infrastructure from untrusted code. In this paper, we show that these solutions are not complete. We first develop two proof-of-concept attacks against a state-of-the-art PKU-based memory isolation scheme. We then present Cerberus, a PKU-based sandboxing framework that can overcome limitations of existing sandboxes. We apply Cerberus to several memory isolation schemes, and show that it is practical, efficient, and secure.

Original languageEnglish
Title of host publicationEuroSys 2022 - Proceedings of the 17th European Conference on Computer Systems
Pages266-282
Number of pages17
ISBN (Electronic)9781450391627
DOIs
Publication statusPublished - 28 Mar 2022
Externally publishedYes

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