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 run-time 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 run-time 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.Comment: Extended version of article to appear in CCS '16 Proceedings of the 23rd ACM Conference on Computer and Communications Securit

Runtime protection of software programs against control- and data-oriented attacks

Software programs are everywhere and continue to create value for us at an incredible pace. But this comes at the cost of facing new risks as our well-being and the stability of societies become strongly dependent on their correctness. Even if the software loaded in the memory is considered legitimate or benign, this does not mean that the code will execute as expected at runtime. Software programs, particularly the ones developed in unsafe languages (e.g., C/C++), inevitably contain many memory bugs. Attackers exploiting these bugs can achieve malicious computations outside the original specification of the program by corrupting its control and data variables in the memory. A potential solution to such runtime attacks must either ensure the integrity of those variables or check the validity of the values they hold. A complete version of the former method, which requires inspection of all memory accesses, can eliminate all the performance benefits of the language used. Alternatively, checking whether specific variables constitute a legitimate state is a non-trivial task that needs to handle state explosion and over-approximation issues. Regardless of the method preferred, most runtime protections are subject to common challenges. For example, as the scope of protection widens, such as the inclusion of data-oriented attacks (in addition to control-oriented attacks), performance costs inevitably increase as well. This is especially true for software-based methods that also suffer from weaker security guarantees. On the contrary, most hardware-based techniques promise better security and performance. But they face substantial deployment challenges without offering any solution to existing devices already out there. In this thesis, we aim to tackle these research challenges by delivering multiple runtime protections in different settings. First, the thesis presents the design of a non-invasive hardware module that can enable attesting runtime correctness on critical embedded systems in real-time. Second, we address the performance burden of covering data-oriented attacks, by suggesting a novel technique to distinguish critical variables from those that are unlikely to be attacked. This is to develop a selective protection scheme with practical performance overheads, without having to check all data variables or corresponding memory accesses. Third, the thesis presents a software-based solution that promises hardware-level protection for critical variables. For this purpose, it leverages the CPU registers available in any architecture with extra help from cryptography. Lastly, we explore the use of runtime interactions with the operating system to identify malicious software executions

Contributions to Securing Software Updates in IoT

The Internet of Things (IoT) is a large network of connected devices. In IoT, devices can communicate with each other or back-end systems to transfer data or perform assigned tasks. Communication protocols used in IoT depend on target applications but usually require low bandwidth. On the other hand, IoT devices are constrained, having limited resources, including memory, power, and computational resources. Considering these limitations in IoT environments, it is difficult to implement best security practices. Consequently, network attacks can threaten devices or the data they transfer. Thus it is crucial to react quickly to emerging vulnerabilities. These vulnerabilities should be mitigated by firmware updates or other necessary updates securely. Since IoT devices usually connect to the network wirelessly, such updates can be performed Over-The-Air (OTA). This dissertation presents contributions to enable secure OTA software updates in IoT. In order to perform secure updates, vulnerabilities must first be identified and assessed. In this dissertation, first, we present our contribution to designing a maturity model for vulnerability handling. Next, we analyze and compare common communication protocols and security practices regarding energy consumption. Finally, we describe our designed lightweight protocol for OTA updates targeting constrained IoT devices. IoT devices and back-end systems often use incompatible protocols that are unable to interoperate securely. This dissertation also includes our contribution to designing a secure protocol translator for IoT. This translation is performed inside a Trusted Execution Environment (TEE) with TLS interception. This dissertation also contains our contribution to key management and key distribution in IoT networks. In performing secure software updates, the IoT devices can be grouped since the updates target a large number of devices. Thus, prior to deploying updates, a group key needs to be established among group members. In this dissertation, we present our designed secure group key establishment scheme. Symmetric key cryptography can help to save IoT device resources at the cost of increased key management complexity. This trade-off can be improved by integrating IoT networks with cloud computing and Software Defined Networking (SDN).In this dissertation, we use SDN in cloud networks to provision symmetric keys efficiently and securely. These pieces together help software developers and maintainers identify vulnerabilities, provision secret keys, and perform lightweight secure OTA updates. Furthermore, they help devices and systems with incompatible protocols to be able to interoperate

Secure FaaS orchestration in the fog: how far are we?

AbstractFunction-as-a-Service (FaaS) allows developers to define, orchestrate and run modular event-based pieces of code on virtualised resources, without the burden of managing the underlying infrastructure nor the life-cycle of such pieces of code. Indeed, FaaS providers offer resource auto-provisioning, auto-scaling and pay-per-use billing at no costs for idle time. This makes it easy to scale running code and it represents an effective and increasingly adopted way to deliver software. This article aims at offering an overview of the existing literature in the field of next-gen FaaS from three different perspectives: (i) the definition of FaaS orchestrations, (ii) the execution of FaaS orchestrations in Fog computing environments, and (iii) the security of FaaS orchestrations. Our analysis identify trends and gaps in the literature, paving the way to further research on securing FaaS orchestrations in Fog computing landscapes

TruSDN: Bootstrapping Trust in Cloud Network Infrastructure

Software-Defined Networking (SDN) is a novel architectural model for cloud network infrastructure, improving resource utilization, scalability and administration. SDN deployments increasingly rely on virtual switches executing on commodity operating systems with large code bases, which are prime targets for adversaries attacking the network infrastructure. We describe and implement TruSDN, a framework for bootstrapping trust in SDN infrastructure using Intel Software Guard Extensions (SGX), allowing to securely deploy SDN components and protect communication between network endpoints. We introduce ephemeral flow-specific pre-shared keys and propose a novel defence against cuckoo attacks on SGX enclaves. TruSDN is secure under a powerful adversary model, with a minor performance overhead

SOFIA : software and control flow integrity architecture

Microprocessors used in safety-critical systems are extremely sensitive to software vulnerabilities, as their failure can lead to injury, damage to equipment, or environmental catastrophe. This paper proposes a hardware-based security architecture for microprocessors used in safety-critical systems. The proposed architecture provides protection against code injection and code reuse attacks. It has mechanisms to protect software integrity, perform control flow integrity, prevent execution of tampered code, and enforce copyright protection. We are the first to propose a mechanism to enforce control flow integrity at the finest possible granularity. The proposed architectural features were added to the LEON3 open source soft microprocessor, and were evaluated on an FPGA running a software benchmark. The results show that the hardware area is 28.2% larger and the clock is 84.6% slower, while the software benchmark has a cycle overhead of 13.7% and a total execution time overhead of 110% when compared to an unmodified processor