Resource constrained embedded devices are often expected to be deployed and stay active in the field for prolonged amounts of time (sometimes decades!). The increasing scale of deployment of Internet of Things (IoT) devices has made security challenges in embedded systems more visible and pervasive. The risks posed by deployed devices left unpatched and vulnerable in the field is forcing the industry to rethink the assumptions about how these devices are actually used and maintained. Concerns about the state of IoT security are becoming increasingly urgent, and technology that improves the resilience of embedded systems against different security threats are necessary for the sustainability of IoT devices, in particular devices that operate unattended.

More powerful IoT devices capable of running general purpose operating systems (such as embedded flavors of Linux) may leverage security mechanisms designed for desktop or mobile devices. However, many existing solutions target a specific class of devices with regards to the hardware and operating system setup (e.g. Windows PC, Android phone, Linux server). As such, existing solutions are not able to address the requirements of the very broad set of IoT devices. In particular, they do not scale to small microcontroller class devices which run simple Real-Time Operating Systems (RTOSs) or no operating systems at all.  The goal of the Embedded Systems Security (ESS) project is to study and develop technologies that can be used to harden such resource-constrained devices against modern security threats, such as run-time attacks.

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Research Topics

Research topics in this are include:

C-FLAT: Control-Flow Attestation for Embedded Systems Software

Remote attestation is a crucial security service particularly relevant to increasingly popular IoT (and other embedded) devices. It allows a trusted party (verifier) to learn the state of a remote, and potentially malware-infected, device (prover). Most existing approaches are static in nature and only check whether benign software is initially loaded on the prover. However, they are vulnerable to runtime attacks that hijack the application’s control or data flow, e.g., via return-oriented programming or data-oriented exploits.

As a concrete step towards more comprehensive runtime remote attestation, we present the design and implementation of Control- FLow ATtestation (C-FLAT) that enables remote attestation of an application’s control-flow path, without requiring the source code. We describe a full prototype implementation of C-FLAT on Raspberry Pi using its ARM TrustZone hardware security extensions. We evaluate C-FLAT’s performance using a real-world embedded (cyber-physical) application, and demonstrate its efficacy against control-flow hijacking attacks.

CFI CaRE: Hardware-supported Call and Return Enforcement for Commercial Microcontrollers

With the increasing scale of deployment of Internet of Things (IoT), concerns about IoT security have become more urgent. In particular, memory corruption attacks play a predominant role as they allow remote compromise of IoT devices. Control-flow integrity (CFI) is a promising and generic defense technique against these attacks. However, given the nature of IoT deployments, existing protection mechanisms for traditional computing environments (including CFI) need to be adapted to the IoT setting. In this paper, we describe the challenges of enabling CFI on microcontroller (MCU) based IoT devices. We then present CaRE, the first interrupt-aware CFI scheme for low-end MCUs. CaRE uses a novel way of protecting the CFI metadata by leveraging TrustZone-M security extensions introduced in the ARMv8-M architecture. Its binary instrumentation approach preserves the memory layout of the target MCU software, allowing pre-built bare-metal binary code to be protected by CaRE. We describe our implementation on a Cortex-M Prototyping System and demonstrate that CaRE is secure while imposing acceptable performance and memory impact.

HardScope: Thwarting DOP attacks with Hardware-assisted Run-time Scope Enforcement

Widespread use of memory unsafe programming languages (e.g., C and C++) leaves many systems vulnerable to memory corruption attacks. A variety of defenses have been proposed to mitigate attacks that exploit memory errors to hijack the control flow of the code at run-time, e.g., (fine-grained) randomization or Control Flow Integrity. However, recent work on data-oriented programming (DOP) demonstrated highly expressive (Turing-complete) attacks, even in the presence of these state-of-the-art defenses. Although multiple real-world DOP attacks have been demonstrated, no efficient defenses are yet available. We propose run-time scope enforcement (RSE), a novel approach designed to efficiently mitigate all currently known DOP attacks by enforcing compile-time memory safety constraints (e.g., variable visibility rules) at run-time. We present HardScope, a proof-of-concept implementation of hardware-assisted RSE for the new RISC-V open instruction set architecture. We discuss our systematic empirical evaluation of HardScope which demonstrates that it can mitigate all currently known DOP attacks, and has a real-world performance overhead of 3.2% in embedded benchmarks.

Publications

  • T. Abera, N. Asokan , L. Davi , J-E. Ekberg, T. Nyman , A. Paverd , A-R. Sadeghi and G. Tsudik: C-FLAT: Control-Flow Attestation for Embedded Systems Software.  In Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security (CCS ’16). ACM, New York, NY, USA, 743-754.
    DOI: https://doi.org/10.1145/2976749.2978358
    Technical report available at: https://arxiv.org/abs/1605.07763
  • G. Dessouky, S. Zeitouni, T. Nyman, A. Paverd, L. Davi, P. Koeberl, N. Asokan and A-R. Sadeghi. LO-FAT: Low-Overhead Control Flow ATtestation in Hardware. In Proceedings of the 54th Annual Design Automation Conference 2017 (DAC ’17). ACM, New York, NY, USA, Article 24, 6 pages.
    DOI: https://doi.org/10.1145/3061639.3062276
    Technical report available at: https://arxiv.org/abs/1706.03754
  • T. Nyman, J-E. Ekberg, L. Davi and N. Asokan: CFI CaRE: Hardware-supported Call and Return Enforcement for Commercial Microcontrollers. In: Dacier M., Bailey M., Polychronakis M., Antonakakis M. (eds) Research in Attacks, Intrusions, and Defenses. RAID 2017. Lecture Notes in Computer Science, vol 10453. Springer, Cham, 259-284.
    DOI: https://doi.org/10.1007/978-3-319-66332-6_12
    Technical report available at: https://arxiv.org/abs/1706.05715
  • T. Nyman. G. Dessouky, S. Zeitouni. A. Lehikoinen, A. Paverd, N. Asokan and A-R. Sadeghi. HardScope: Thwarting DOP attacks with Hardware-assisted Run-time Scope Enforcement.
    Technical report available at: https://arxiv.org/abs/1705.10295

Doctoral Dissertations

Master’s Theses

  • Aaro Lehikoinen: HardScope: Run-time Variable Scope Enforcement as a Defense Against Data-oriented Programming Attacks, Helsinki University, 2017.

Demo’s & Posters

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