Address Space Layout Randomization Comparative Analysis on Windows 10 and Ubuntu 18.04 LTS

Memory management is one of the main tasks of an Operating System, where the data of each process running in the system is kept. In this context, there exist several types of attacks that exploit memory-related vulnerabilities, forcing Operating Systems to feature memory protection techniques that make difficult to exploit them. One of these techniques is ASLR, whose function is to introduce randomness into the virtual address space of a process. The goal of this work was to measure, analyze and compare the behavior of ASLR on the 64-bit versions of Windows 10 and Ubuntu 18.04 LTS. The results have shown that the implementation of ASLR has improved significantly on these two Operating Systems compared to previous versions. However, there are aspects, such as partial correlations or a frequency distribution that is not always uniform, so it can still be improved.

Breaking KASLR Using Memory Deduplication in Virtualized Environments

Recent operating systems (OSs) have adopted a defense mechanism called kernel page table isolation (KPTI) for protecting the kernel from all attacks that break the kernel address space layout randomization (KASLR) using various side-channel analysis techniques. In this paper, we demonstrate that KASLR can still be broken, even with the latest OSs where KPTI is applied. In particular, we present a novel memory-sharing-based side-channel attack that breaks the KASLR on KPTI-enabled Linux virtual machines. The proposed attack leverages the memory deduplication feature on a hypervisor, which provides a timing channel for inferring secret information regarding the victim. By conducting experiments on KVM and VMware ESXi, we show that the proposed attack can obtain the kernel address within a short amount of time. We also present several countermeasures that can prevent such an attack.

Securely Sharing Randomized Code that Flies

Address Space Layout Randomization (ASLR) was a great role model being a light-weight defense technique that could prevent early return-oriented programming attacks. Simple yet effective, ASLR was quickly widely-adopted. Conversely, today only a trickle of defense techniques are being integrated or adopted mainstream. As code reuse attacks have evolved, defenses have strived to keep up. To do so, many have had to take unfavorable tradeoffs like using background threads or protecting only a subset of sensitive code. In reality, these tradeoffs were unavoidable steps necessary to improve the strength of the state-of-the-art. We present Goose, an on-demand system-wide runtime re-randomization technique capable of scalable protection of application as well as shared library code most defenses have forgone. We achieve code sharing with diversification by implementing reactive and scalable, rather than continuous or one-time diversification. Enabling code sharing further removes redundant computation like tracking, patching, along with memory overheads required by prior randomization techniques. In its baseline state, the code transformations needed for Goose security hardening incur a reasonable performance overhead of 5.5% on SPEC and minimal degradation of 4.4% in NGINX, demonstrating its applicability to both compute-intensive and scalable real-world applications. Even when under attack, Goose only adds from less than 1% up to 15% depending on application complexity.

A Review of Memory Errors Exploitation in x86-64

Memory errors are still a serious threat affecting millions of devices worldwide. Recently, bounty programs have reached a new record, paying up to USD 2.5 million for one single vulnerability in Android and up to USD 2 million for Apple’s operating system. In almost all cases, it is common to exploit memory errors in one or more stages to fully compromise those devices. In this paper, we review and discuss the importance of memory error vulnerabilities, and more specifically stack buffer overflows to provide a full view of how memory errors are exploited. We identify the root causes that make those attacks possible on modern x86-64 architecture in the presence of modern protection techniques. We have analyzed how unsafe library functions are prone to buffer overflows, revealing that although there are secure versions of those functions, they are not actually preventing buffer overflows from happening. Using secure functions does not result in software free from vulnerabilities and it requires developers to be security-aware. To overcome this problem, we discuss the three main security protection techniques present in all modern operating system; the non-eXecutable bit (NX), the Stack Smashing Protector (SSP) and the Address Space Layout Randomization (ASLR). After discussing their effectiveness, we conclude that although they provide a strong level of protection against classical exploitation techniques, modern attacks can bypass them.

Lightweight and Seamless Memory Randomization for Mission-Critical Services in a Cloud Platform

Nowadays, various computing services are often hosted on cloud platforms for their availability and cost effectiveness. However, such services are frequently exposed to vulnerabilities. Therefore, many countermeasures have been invented to defend against software hacking. At the same time, more complicated attacking techniques have been created. Among them, code-reuse attacks are still an effective means of abusing software vulnerabilities. Although state-of-the-art address space layout randomization (ASLR) runtime-based solutions provide a robust way to mitigate code-reuse attacks, they have fundamental limitations; for example, the need for system modifications, and the need for recompiling source codes or restarting processes. These limitations are not appropriate for mission-critical services because a seamless operation is very important. In this paper, we propose a novel ASLR technique to provide memory rerandomization without interrupting the process execution. In addition, we describe its implementation and evaluate the results. In summary, our method provides a lightweight and seamless ASLR for critical service applications.

Address Space Layout Randomization Next Generation

Systems that are built using low-power computationally-weak devices, which force developers to favor performance over security; which jointly with its high connectivity, continuous and autonomous operation makes those devices specially appealing to attackers. ASLR (Address Space Layout Randomization) is one of the most effective mitigation techniques against remote code execution attacks, but when it is implemented in a practical system its effectiveness is jeopardized by multiple constraints: the size of the virtual memory space, the potential fragmentation problems, compatibility limitations, etc. As a result, most ASLR implementations (specially in 32-bits) fail to provide the necessary protection. In this paper we propose a taxonomy of all ASLR elements, which categorizes the entropy in three dimensions: (1) how, (2) when and (3) what; and includes novel forms of entropy. Based on this taxonomy we have created, ASLRA, an advanced statistical analysis tool to assess the effectiveness of any ASLR implementation. Our analysis show that all ASLR implementations suffer from several weaknesses, 32-bit systems provide a poor ASLR, and OS X has a broken ASLR in both 32- and 64-bit systems. This is jeopardizing not only servers and end users devices as smartphones but also the whole IoT ecosystem. To overcome all these issues, we present ASLR-NG, a novel ASLR that provides the maximum possible absolute entropy and removes all correlation attacks making ASLR-NG the best solution for both 32- and 64-bit systems. We implemented ASLR-NG in the Linux kernel 4.15. The comparative evaluation shows that ASLR-NG overcomes PaX, Linux and OS X implementations, providing strong protection to prevent attackers from abusing weak ASLRs.