An Info-Leak Resistant Kernel Randomization for Virtualized Systems

Given the significance that the cloud paradigm has in modern society, it is extremely important to provide security to users at all levels, especially at the most fundamental ones since these are the most sensitive and potentially harmful in the event of an attack. However, the cloud computing paradigm brings new challenges in which security mechanisms are weakened or deactivated to improve profitability and exploitation of the available resources. Kernel randomization is an important security mechanism that is currently present in all main operating systems. Function-Granular Kernel Randomization is a new step that aims to be the future of the kernel randomization, because it provides much more security than current kernel randomization approaches. Unfortunately, function-granular kernel randomization also impacts significantly on the performance and potential benefits of memory deduplication. Both function-granular kernel randomization and memory deduplication are desired and beneficial; the first for the strong protection it gives, and the second for the reduction of costs in terms of memory consumption. In this paper, we analyse the impact of function-granular kernel randomization on memory deduplication revealing why it cannot offer maximum security and shareability of memory simultaneously. We also discuss the reasons why having a full position independent kernel code counter-intuitively does not solve the problem introducing a challenge to kernel randomization designers. To solve these problems, we propose a function-granular kernel randomization modification for cloud systems that enables full function-granular kernel randomization while reduces memory deduplication cancellations to almost zero. The proposed approach forces guest kernels of the same tenant to have the same random memory layout of memory regions with high impact on deduplication, ensuring a high rate of deduplicated pages while the kernel randomization is fully enabled. Our approach enables cloud providers to have both, high levels of security and an efficient use of resources.