Return-Oriented Rootkits: Bypassing Kernel Code Integrity Protection Mechanisms Ralf Hund Thorsten Holz Felix C. Freiling Laboratory for Dependable Distributed Systems University of Mannheim, Germany
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[email protected] Abstract In recent years, several mechanism to protect the in- tegrity of the kernel were introduced [6, 9, 15, 19, 22], Protecting the kernel of an operating system against at- as we now explain. The main idea behind all of these tacks, especially injection of malicious code, is an impor- approaches is that the memory of the kernel should be tant factor for implementing secure operating systems. protected against unauthorized injection of code, such as Several kernel integrity protection mechanism were pro- rootkits. Note that we focus in this work on kernel in- posed recently that all have a particular shortcoming: tegrity protection mechanisms and not on control-flow They cannot protect against attacks in which the attacker integrity [1, 7, 14, 18] or data-flow integrity [5] mech- re-uses existing code within the kernel to perform mali- anisms, which are orthogonal to the techniques we de- cious computations. In this paper, we present the design scribe in the following. and implementation of a system that fully automates the process of constructing instruction sequences that can be 1.1 Kernel Integrity Protection Mecha- used by an attacker for malicious computations. We eval- uate the system on different commodity operating sys- nisms tems and show the portability and universality of our Kernel Module Signing. Kernel module signing is a approach. Finally, we describe the implementation of a simple approach to achieve kernel code integrity.