IMIX: In-Process Memory Isolation EXtension


Tommaso Frassetto, Patrick Jauernig, Christopher Liebchen, and Ahmad-Reza Sadeghi, Technische Universität Darmstadt


Memory-corruption attacks have been subject to extensive research in the latest decades. Researchers demonstrated sophisticated attack techniques, such as (just-in-time/blind) return-oriented programming and counterfeit object-oriented programming, which enable the attacker to execute arbitrary code and data-oriented attacks that are commonly used for privilege escalation. At the same time, the research community proposed a number of effective defense techniques. In particular, control-flow integrity (CFI), code-pointer integrity (CPI), and fine-grained code randomization are effective mitigation techniques against code-reuse attacks. All of these techniques require strong memory isolation. For example, CFI's shadow stack, CPI's safe-region, and the randomization secret must be protected from adversaries able to perform arbitrary read-write accesses.

In this paper we propose IMIX, a lightweight, in-process memory isolation extension for the Intel-based x86 CPUs. Our solution extends the x86 ISA with a new memory-access permission to mark memory pages as security sensitive. These memory pages can then only be accessed with a newly introduced instruction. Unlike previous work, IMIX is not tailored towards a specific defense (technique) but can be leveraged as a primitive to protect the data of a wide variety of memory-corruption defenses. We provide a proof of concept of IMIX using Intel's Simulation and Analysis Engine. We extend Clang/LLVM to include our new instruction, and enhance CPI by protecting CPI's safe region using IMIX.

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@inproceedings {217644,
author = {Tommaso Frassetto and Patrick Jauernig and Christopher Liebchen and Ahmad-Reza Sadeghi},
title = {{IMIX}: In-Process Memory Isolation EXtension},
booktitle = {27th {USENIX} Security Symposium ({USENIX} Security 18)},
year = {2018},
isbn = {978-1-931971-46-1},
address = {Baltimore, MD},
pages = {83--97},
url = {},
publisher = {{USENIX} Association},