In recent years, the disclosure of several significant security vulnerabilities has revealed the trust put in some presumed security properties of commonplace hardware to be misplaced. We propose to design hardware systems with security mechanisms, together with a formal statement of the security properties obtained, and a machine-checked proof that the hardware security mechanisms indeed implement the sought-for security property. Formally proving security properties about hardware systems might seem prohibitively complex and expensive. In this paper, we tackle this concern by designing a realistic and accessible methodology on top of the Kôlka Hardware Description Language for specifying and proving security properties during hardware development. Our methodology is centered around a verified compiler from high-level and inefficient to work with Kôlka models to an equivalent lower-level representation, where side effects are made explicit and reasoning is convenient. We apply this methodology to a concrete example: the formal specification and implementation of a shadow stack mechanism on an RV32I processor. We prove that this security mechanism is correct, i.e., any illegal modification of a return address does indeed result in the termination of the whole system. Furthermore, we show that this modification of the processor does not impact its behaviour in other, unexpected ways.

International audience

Abstract Modern computing systems have grown in complexity, and even though system components are generally carefully designed and even verified by different groups of people, thecompositionof these components is often regarded with less attention. Inconsistencies between components’ assumptions on the rest of the system can have significant repercussions on this system, and may ultimately lead to safety or security issues. In this article, we introduce FreeSpec, a formalismbuilt upon the key idea that components can bemodeled as programs with algebraic effects to be realized by other components. FreeSpec allows for the modular modeling of a complex system, by defining idealized components connected together, and the modular verification of the properties of their composition. In addition, we have implemented a framework for the Coq proof assistant based on FreeSpec.

Despite the deployment of preventive security mechanisms to protect the assets and computing platforms of users, intrusions eventually occur. We propose a novel intrusion survivability approach to withstand ongoing intrusions. Our approach relies on an orchestration of fine-grained recovery and per-service responses (e.g., privileges removal). Such an approach may put the system into a degraded mode. This degraded mode prevents attackers to reinfect the system or to achieve their goals if they managed to reinfect it. It maintains the availability of core functions while waiting for patches to be deployed. We devised a cost-sensitive response selection process to ensure that while the service is in a degraded mode, its core functions are still operating. We built a Linux-based prototype and evaluated the effectiveness of our approach against different types of intrusions. The results show that our solution removes the effects of the intrusions, that it can select appropriate responses, and that it allows services to survive when reinfected. In terms of performance overhead, in most cases, we observed a small overhead, except in the rare case of services that write many small files asynchronously in a burst, where we observed a higher but acceptable overhead.

At present, computer science studies generally offer courses addressing mobile development and they use mobile technologies for illustrating theoretical concepts such as operating system, design patterns, and compilation because Android and iOS use a large variety of technologies for developing applications. Teaching courses on security is also becoming an important concern for academics, and the use of mobile platforms (such as Android) as supporting material is becoming a reasonable option. In this paper, we intend to bridge a gap in the literature by reversing this paradigm: Android is not only an opportunity to learn security concepts but requires strong pedagogical efforts for covering all the aspects of mobile security. Thus, we propose teaching Android mobile security through a two-dimensional approach. The first dimension addresses the cognitive process of the Bloom taxonomy, and the second dimension addresses the technical layers of the architecture of the Android operating system. We describe a set of comprehensive security laboratory courses covering various concepts, ranging from the application development perspective to a deep investigation of the Android Open Source Project and its interaction with the Linux kernel. We evaluated this approach, and our results verify that the designed security labs impart the required knowledge to the students.

Highly privileged software, such as firmware, is an attractive target for attackers. Thus, BIOS vendors use cryptographic signatures to ensure firmware integrity at boot time. Nevertheless, such protection does not prevent an attacker from exploiting vulnerabilities at runtime. To detect such attacks, we propose an event-based behavior monitoring approach that relies on an isolated co-processor. We instrument the code executed on the main CPU to send information about its behavior to the monitor. This information helps to resolve the semantic gap issue. Our approach does not depend on a specific model of the behavior nor on a specific target. We apply this approach to detect attacks targeting the System Management Mode (SMM), a highly privileged x86 execution mode executing firmware code at runtime. We model the behavior of SMM using invariants of its control-flow and relevant CPU registers (CR3 and SMBASE). We instrument two open-source firmware implementations: EDKII and coreboot. We evaluate the ability of our approach to detect state-of-the-art attacks and its runtime execution overhead by simulating an x86 system coupled with an ARM Cortex A5 co-processor. The results show that our solution detects intrusions from the state of the art, without any false positives, while remaining acceptable in terms of performance overhead in the context of the SMM (i.e., less than the 150 us threshold defined by Intel).

Security is a major issue nowadays for the embedded systems community. Untrustworthy authorities may use a wide range of attacks in order to retrieve critical information. This paper introduces ARMHEx, a practical solution targeting DIFT (Dynamic Information Flow Tracking) on ARM-based SoCs (e.g. Xilinx Zynq). Current DIFT implementations suffer from two major drawbacks. First, recovering required information for DIFT is generally based on software instrumentation leading to high time overheads. ARMHEx takes profit of ARM CoreSight debug components and static analysis to drastically reduce instrumentation time overhead (up to 90% compared to existing works). Then, security of the DIFT hardware extension itself is not considered in related works. In this work, we tackle this issue by proposing a solution based on ARM Trustzone.

Security in embedded systems remains a major concern. Untrustworthy authorities use a wide range of software attacks. This demo introduces ARMHEx, a practical solution targeting DIFT (Dynamic Information Flow Tracking) implementations on ARM-based SoCs. DIFT is a solution that consists in tracking the dissemination of data inside the system and allows to enforce some security properties. In this demo, we show an implementation of ARMHEx on Xilinx Zynq SoC. Especially, we show how the required information for DIFT is recovered with the help of traces produced by CoreSight components, static analysis and instrumentation.

This work details a hardware-assisted approach for information flow tracking implemented on a reconfigurable chip. Current solutions are either time-consuming or hardly portable (modifications of both sofware/hardware layers). This work takes benefits from debug components included in ARMv7 processors to retrieve details on instructions committed by the CPU. First results in terms of silicon area and time overheads are also given.

The security of the web-browser and JavaScript is pivotal in today's world. The potency of information flow control in the context of JavaScript is quite appealing. In this paper, we propose a new secure information flow control model specifically designed for JavaScript. In our approach, we augment the standard symbol table with a mechanism that replaces the reference address for secret values based on the current execution stack. This mechanism also ensures that the secret is stored in a dedicated memory location that can only be accessed by the internal JIT compiler thereby protecting the variable from any unintended leakage or modification by a malicious JavaScript.

Network security products, such as NIDS or application firewalls, tend to focus on application level communication flows. However, adding support for new proprietary and often undocumented protocols, implies the reverse engineering of these protocols. Currently, this task is performed manually. Considering the difficulty and time needed for manual reverse engineering of protocols, one can easily understand the importance of automating this task. This is even given more significance in today's cybersecurity context where reaction time and automated adaptation become a priority. Several studies were carried out to infer protocol's specifications from traces. As shown in this article, they do not provide accurate results on complex protocols and are often not applicable in an operational context to provide parsers or traffic generators, some key indicators of the quality of obtained specifications. In addition, too few previous works have resulted in the publication of tools that would allow the scientific community to experimentally validate and compare the different approaches.

This article focuses on intrusion detection in systems using Web applications and COTS. We present a solution that combines policy-based intrusion detection and information flow control. We describe JBlare, an inline Java monitor that tracks inter-method flows in Java applications. This monitor collaborates with Blare, a monitor that tracks information flow in the whole system at the OS-level. The combination of these two detectors constitutes a policy-based Intrusion Detection System that can address a wide range of attacks.

This article focuses on intrusion detection in systems using Web applications and COTS. We present a solution that combines policy-based intrusion detection and information flow control. We describe JBlare, an inline Java monitor that tracks inter-method flows in Java applications. This monitor collaborates with Blare, a monitor that tracks information flow in the whole system at the OS-level. The combination of these two detectors constitutes a policy-based Intrusion Detection System that can address a wide range of attacks.