A survey on the (in)security of trusted execution environments

As the number of security and privacy attacks continue to grow around the world, there is an ever increasing need to protect our personal devices. As a matter of fact, more and more manufactures are relying on Trusted Execution Environments (TEEs) to shield their devices. In particular, ARM TrustZone (TZ) is being widely used in numerous embedded devices, especially smartphones, and this technology is the basis for secure solutions both in industry and academia. However, as shown in this paper, TEE is not bullet-proof and it has been successfully attacked numerous times and in very different ways. To raise awareness among potential stakeholders interested in this technology, this paper provides an extensive analysis and categorization of existing vulnerabilities in TEEs and highlights the design flaws that led to them. The presented vulnerabilities, which are not only extracted from existing literature but also from publicly available exploits and databases, are accompanied by some effective countermeasures to reduce the likelihood of new attacks. The paper ends with some appealing challenges and open issues.Funding for open access charge: Universidad de Málaga / CBUA This work has been partially supported by the Spanish Ministry of Science and Innovation through the SecureEDGE project (PID2019-110565RB-I00), and by the by the Andalusian FEDER 2014–2020 Program through the SAVE project (PY18-3724)

Binary Exploitation in Industrial Control Systems: Past, Present and Future

Despite being a decades-old problem, binary exploitation still remains a serious issue in computer security. It is mainly due to the prevalence of memory corruption errors in programs written with notoriously unsafe but yet indispensable programming languages like C and C++. For the past 30 years, the nip-and-tuck battle in memory between attackers and defenders has been getting more technical, versatile, and automated. With raised bar for exploitation in common information technology (IT) systems owing to hardened mitigation techniques, and with unintentionally opened doors into industrial control systems (ICS) due to the proliferation of industrial internet of things (IIoT), we argue that we will see an increased number of cyber attacks leveraging binary exploitation on ICS in the near future. However, while this topic generates a very rich and abundant body of research in common IT systems, there is a lack of systematic study targeting this topic in ICS. The present work aims at filling this gap and serves as a comprehensive walkthrough of binary exploitation in ICS. Apart from providing an analysis of the past cyber attacks leveraging binary exploitation on ICS and the ongoing attack surface transition, we give a review of the attack techniques and mitigation techniques on both general-purpose computers and embedded devices. At the end, we conclude this work by stressing the importance of network-based intrusion detection, considering the dominance of resource-constrained real-time embedded devices, low-end embedded devices in ICS, and the limited ability to deploy arbitrary defense mechanism directly on these devices

SECURITY AND PRIVACY ASPECTS OF MOBILE PLATFORMS AND APPLICATIONS

Mobile smart devices (such as smartphones and tablets) emerged to dominant computing platforms for end-users. The capabilities of these convenient mini-computers seem nearly boundless: They feature compelling computing power and storage resources, new interfaces such as Near Field Communication (NFC) and Bluetooth Low Energy (BLE), connectivity to cloud services, as well as a vast number and variety of apps. By installing these apps, users can turn a mobile device into a music player, a gaming console, a navigation system, a business assistant, and more. In addition, the current trend of increased screen sizes make these devices reasonable replacements for traditional (mobile) computing platforms such as laptops. On the other hand, mobile platforms process and store the extensive amount of sensitive information about their users, ranging from the user’s location data to credentials for online banking and enterprise Virtual Private Networks (VPNs). This raises many security and privacy concerns and makes mobile platforms attractive targets for attackers. The rapid increase in number, variety and sophistication of attacks demonstrate that the protection mechanisms offered by mobile systems today are insufficient and improvements are necessary in order to make mobile devices capable of withstanding modern security and privacy threats. This dissertation focuses on various aspects of security and privacy of mobile platforms. In particular, it consists of three parts: (i) advanced attacks on mobile platforms and countermeasures; (ii) online authentication security for mobile systems, and (iii) secure mobile applications and services. Specifically, the first part of the dissertation concentrates on advanced attacks on mobile platforms, such as code re-use attacks that hijack execution flow of benign apps without injecting malicious code, and application-level privilege escalation attacks that allow malicious or compromised apps to gain more privileges than were initially granted. In this context, we develop new advanced code re-use attack techniques that can bypass deployed protection mechanisms (e.g., Address Space Layout Randomization (ASLR)) and cannot be detected by any of the existing security tools (e.g., return address checkers). Further, we investigate the problem of application-level privilege escalation attacks on mobile platforms like Android, study and classify them, develop proof of concept exploits and propose countermeasures against these attacks. Our countermeasures can mitigate all types of application-level privilege escalation attacks, in contrast to alternative solutions proposed in literature. In the second part of the dissertation we investigate online authentication schemes frequently utilized by mobile users, such as the most common web authentication based upon the user’s passwords and the recently widespread mobile 2-factor authentication (2FA) which extends the password-based approach with a secondary authenticator sent to a user’s mobile device or generated on it (e.g, a One-time Password (OTP) or Transaction Authentication Number (TAN)). In this context we demonstrate various weaknesses of mobile 2FA schemes deployed for login verification by global Internet service providers (such as Google, Dropbox, Twitter, and Facebook) and by a popular Google Authenticator app. These weaknesses allow an attacker to impersonate legitimate users even if their mobile device with the secondary authenticator is not compromised. We then go one step further and develop a general attack method for bypassing mobile 2FA schemes. Our method relies on a cross-platform infection (mobile-to-PC or PC-to-mobile) as a first step in order to compromise the Personal Computer (PC) and a mobile device of the same user. We develop proof-of-concept prototypes for a cross-platform infection and show how an attacker can bypass various instantiations of mobile 2FA schemes once both devices, PC and the mobile platform, are infected. We then deliver proof-of-concept attack implementations that bypass online banking solutions based on SMS-based TANs and visual cryptograms, as well as login verification schemes deployed by various Internet service providers. Finally, we propose a wallet-based secure solution for password-based authentication which requires no secondary authenticator, and yet provides better security guaranties than, e.g., mobile 2FA schemes. The third part of the dissertation concerns design and development of security sensitive mobile applications and services. In particular, our first application allows mobile users to replace usual keys (for doors, cars, garages, etc.) with their mobile devices. It uses electronic access tokens which are generated by the central key server and then downloaded into mobile devices for user authentication. Our solution protects access tokens in transit (e.g., while they are downloaded on the mobile device) and when they are stored and processed on the mobile platform. The unique feature of our solution is offline delegation: Users can delegate (a portion of) their access rights to other users without accessing the key server. Further, our solution is efficient even when used with constraint communication interfaces like NFC. The second application we developed is devoted to resource sharing among mobile users in ad-hoc mobile networks. It enables users to, e.g., exchange files and text messages, or share their tethering connection. Our solution addresses security threats specific to resource sharing and features the required security mechanisms (e.g., access control of resources, pseudonymity for users, and accountability for resource use). One of the key features of our solution is a privacy-preserving access control of resources based on FoF Finder (FoFF) service, which provides a user-friendly means to configure access control based upon information from social networks (e.g., friendship information) while preserving user privacy (e.g., not revealing their social network identifiers). The results presented in this dissertation were included in several peer-reviewed publications and extended technical reports. Some of these publications had significant impact on follow up research. For example, our publications on new forms of code re-use attacks motivated researchers to develop more advanced forms of ASLR and to re-consider the idea of using Control-Flow Integrity (CFI). Further, our work on application-level privilege escalation attacks was followed by many other publications addressing this problem. Moreover, our access control solution using mobile devices as access tokens demonstrated significant practical impact: in 2013 it was chosen as a highlight of CeBIT – the world’s largest international computer expo, and was then deployed by a large enterprise to be used by tens of thousands of company employees and millions of customers

Physical Fault Injection and Side-Channel Attacks on Mobile Devices:A Comprehensive Analysis

Today's mobile devices contain densely packaged system-on-chips (SoCs) with multi-core, high-frequency CPUs and complex pipelines. In parallel, sophisticated SoC-assisted security mechanisms have become commonplace for protecting device data, such as trusted execution environments, full-disk and file-based encryption. Both advancements have dramatically complicated the use of conventional physical attacks, requiring the development of specialised attacks. In this survey, we consolidate recent developments in physical fault injections and side-channel attacks on modern mobile devices. In total, we comprehensively survey over 50 fault injection and side-channel attack papers published between 2009-2021. We evaluate the prevailing methods, compare existing attacks using a common set of criteria, identify several challenges and shortcomings, and suggest future directions of research

Design and evaluation of information flow signature for secure computation of applications

This thesis presents an architectural solution that provides secure and reliable execution of an application that computes critical data, in spite of potential hardware and software vulnerabilities. The technique does not require source code of or specifications about the malicious library function(s) called during execution of an application. The solution is based on the concept of Information Flow Signatures (IFS). The technique uses both a model-checker-based symbolic fault injection analysis tool called SymPLFIED to generate an IFS for an application or operating system, and runtime signature checking at the level of hardware to protect the integrity of critical data. The runtime checking is implemented in the IFS module. Reliable computation of data is ensured by the critical value re-computation (CVR) module. Prototype implementation of the signature checking and reliability module on a soft processor within an FPGA incurs no performance overhead and about 12% chip area overhead. The security module itself incurs about 7.5% chip area overhead. Performance evaluations indicate that the IFS module incurs as little as 3-4% overhead compared to 88-100% overhead when the runtime checking is implemented as a part of software. Preliminary testing indicates that the technique can provide 100% coverage for insider attacks that manifest as memory corruption and change the architectural state of the processor. Hence the IFS and CVR implementation offers a flexible, low-overhead, high-coverage method for ensuring reliable and secure computing

Resilient Authenticated Execution of Critical Applications in Untrusted Environments

Abstract-Modern computer systems are built on a foundation of software components from a variety of vendors. While critical applications may undergo extensive testing and evaluation procedures, the heterogeneity of software sources threatens the integrity of the execution environment for these trusted programs. For instance, if an attacker can combine an application exploit with a privilege escalation vulnerability, the operating system (OS) can become corrupted. Alternatively, a malicious or faulty device driver running with kernel privileges could threaten the application. While the importance of ensuring application integrity has been studied in prior work, proposed solutions immediately terminate the application once corruption is detected. Although, this approach is sufficient for some cases, it is undesirable for many critical applications. In order to overcome this shortcoming, we have explored techniques for leveraging a trusted virtual machine monitor (VMM) to observe the application and potentially repair damage that occurs. In this paper, we describe our system design, which leverages efficient coding and authentication schemes, and we present the details of our prototype implementation to quantify the overhead of our approach. Our work shows that it is feasible to build a resilient execution environment, even in the presence of a corrupted OS kernel, with a reasonable amount of storage and performance overhead

Demystifying Internet of Things Security

Break down the misconceptions of the Internet of Things by examining the different security building blocks available in Intel Architecture (IA) based IoT platforms. This open access book reviews the threat pyramid, secure boot, chain of trust, and the SW stack leading up to defense-in-depth. The IoT presents unique challenges in implementing security and Intel has both CPU and Isolated Security Engine capabilities to simplify it. This book explores the challenges to secure these devices to make them immune to different threats originating from within and outside the network. The requirements and robustness rules to protect the assets vary greatly and there is no single blanket solution approach to implement security. Demystifying Internet of Things Security provides clarity to industry professionals and provides and overview of different security solutions What You'll Learn Secure devices, immunizing them against different threats originating from inside and outside the network Gather an overview of the different security building blocks available in Intel Architecture (IA) based IoT platforms Understand the threat pyramid, secure boot, chain of trust, and the software stack leading up to defense-in-depth Who This Book Is For Strategists, developers, architects, and managers in the embedded and Internet of Things (IoT) space trying to understand and implement the security in the IoT devices/platforms

ECONOMICALLY PROTECTING COMPLEX, LEGACY OPERATING SYSTEMS USING SECURE DESIGN PRINCIPLES

In modern computer systems, complex legacy operating systems, such as Linux, are deployed ubiquitously. Many design choices in these legacy operating systems predate a modern understanding of security risks. As a result, new attack opportunities are routinely discovered to subvert such systems, which reveal design flaws that spur new research about secure design principles and other security mechanisms to thwart these attacks. Most research falls into two categories: encapsulating the threat and redesigning the system from scratch. Each approach has its challenge. Encapsulation can only limit the exposure to the risk, but not entirely prevent it. Rewriting the huge codebase of these operating systems is impractical in terms of developer effort, but appealing inasmuch as it can comprehensively eliminate security risks. This thesis pursues a third, understudied option: retrofitting security design principles in the existing kernel design. Conventional wisdom discourages retrofitting security because retrofitting is a hard problem, may require the use of new abstractions or break backward compatibility, may have unforeseen consequences, and may be equivalent to redesigning the system from scratch in terms of effort. This thesis offers new evidence to challenge this conventional wisdom, indicating that one can economically retrofit a comprehensive security policy onto complex, legacy systems. To demonstrate this assertion, this thesis firstly surveys the alternative of encapsulating the threat to the complex, legacy system by adding a monitoring layer using a technique called Virtual Machine Introspection, and discusses the shortcomings of this technique. Secondly, this thesis shows how to enforce the principle of least privilege by removing the need to run setuid-to-root binaries with administrator privilege. Finally, this thesis takes the first steps to show how to economically retrofit secure design principles to the OS virtualization feature of the Linux kernel called containers without rewriting the whole system. This approach can be applied more generally to other legacy systems.Doctor of Philosoph

SyzTrust: State-aware Fuzzing on Trusted OS Designed for IoT Devices

Trusted Execution Environments (TEEs) embedded in IoT devices provide a deployable solution to secure IoT applications at the hardware level. By design, in TEEs, the Trusted Operating System (Trusted OS) is the primary component. It enables the TEE to use security-based design techniques, such as data encryption and identity authentication. Once a Trusted OS has been exploited, the TEE can no longer ensure security. However, Trusted OSes for IoT devices have received little security analysis, which is challenging from several perspectives: (1) Trusted OSes are closed-source and have an unfavorable environment for sending test cases and collecting feedback. (2) Trusted OSes have complex data structures and require a stateful workflow, which limits existing vulnerability detection tools. To address the challenges, we present SyzTrust, the first state-aware fuzzing framework for vetting the security of resource-limited Trusted OSes. SyzTrust adopts a hardware-assisted framework to enable fuzzing Trusted OSes directly on IoT devices as well as tracking state and code coverage non-invasively. SyzTrust utilizes composite feedback to guide the fuzzer to effectively explore more states as well as to increase the code coverage. We evaluate SyzTrust on Trusted OSes from three major vendors: Samsung, Tsinglink Cloud, and Ali Cloud. These systems run on Cortex M23/33 MCUs, which provide the necessary abstraction for embedded TEEs. We discovered 70 previously unknown vulnerabilities in their Trusted OSes, receiving 10 new CVEs so far. Furthermore, compared to the baseline, SyzTrust has demonstrated significant improvements, including 66% higher code coverage, 651% higher state coverage, and 31% improved vulnerability-finding capability. We report all discovered new vulnerabilities to vendors and open source SyzTrust.Comment: To appear in the IEEE Symposium on Security and Privacy (IEEE S&P) 2024, San Francisco, CA, US