Publications
Automated exposure notification for COVID-19
February 14, 2023
Technical Report
Published in:
MIT Lincoln Laboratory Report TR-1288
Summary
Private Automated Contact Tracing (PACT) was a collaborative team and effort formed during the beginning of the Coronavirus Disease 2019 (COVID-19) pandemic. PACT's mission was to enhance contact tracing in pandemic response by designing exposure-detection functions in personal digital communication devices that have maximal public health utility while preserving privacy. This report explains and discusses the use of automated exposure notification during the COVID-19 pandemic and to provide some recommendations for those who may try to design and deploy similar technologies in future pandemics.
Summary
Private Automated Contact Tracing (PACT) was a collaborative team and effort formed during the beginning of the Coronavirus Disease 2019 (COVID-19) pandemic. PACT's mission was to enhance contact tracing in pandemic response by designing exposure-detection functions in personal digital communication devices that have maximal public health utility while preserving privacy...
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Mission resilience experimentation and evaluation testbed
November 28, 2022
Conference Paper
Published in:
IEEE Military Communications Conf., MILCOM, 28 November - 2 December 2022.
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As the complexity of DoD systems increases exponentially, the DoD continues to struggle with understanding and improving the resilience of its mission software. The Applied Resilience for Mission Systems (ARMS) Testbed is an environment that enables resilience improvement by experimentation and assessment of different mission system architectures and approaches. This Testbed consists of components for deploying mission system software for testing, capturing system performance, generating traffic, introducing disruptions into the mission system, orchestrating controlled experiments, and assessing and comparing the performance of mission systems. This paper covers the implementation of this Testbed, analysis for mission resilience comparisons, and their application to an operational terrestrial network architecture. Additionally, we introduce the Distance to Failure metric for comparing the resilience of arbitrary mission systems variations.
Summary
As the complexity of DoD systems increases exponentially, the DoD continues to struggle with understanding and improving the resilience of its mission software. The Applied Resilience for Mission Systems (ARMS) Testbed is an environment that enables resilience improvement by experimentation and assessment of different mission system architectures and approaches. This...
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On randomization in MTD systems
November 7, 2022
Conference Paper
Published in:
Proc. of the 9th ACM Workshop on Moving Target Defense, MTD ’22, 7 November 2022.
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Randomization is one of the main strategies in providing security in moving-target-defense (MTD) systems. However, randomization has an associated cost and estimating this cost and its impact on the overall system is crucial to ensure adoption of the MTD strategy. In this paper we discuss our experience in attempting to estimate the cost of path randomization in a message transmission system that used randomization of paths in the network. Our conclusions are (i) the cost crucially depends on the underlying network control technology, (ii) one can reduce this cost by better implementation, and (iii) reducing one type of cost may result in increased costs of a different type, for example a higher device cost. These suggest that estimating the cost of randomization is a multivariable optimization problem that requires a full understanding of the system components.
Summary
Randomization is one of the main strategies in providing security in moving-target-defense (MTD) systems. However, randomization has an associated cost and estimating this cost and its impact on the overall system is crucial to ensure adoption of the MTD strategy. In this paper we discuss our experience in attempting to...
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The tale of discovering a side channel in secure message transmission systems
August 13, 2022
Conference Paper
Published in:
The Conf. for Failed Approaches and Insightful Losses in Cryptology, CFAIL, 13 August 2022.
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Secure message transmission (SMT) systems provide information theoretic security for point-to-point message transmission in networks that are partially controlled by an adversary. This is the story of a research project that aimed to implement a flavour of SMT protocols that uses "path hopping" with the goal of quantifying the real-life efficiency of the system, and while failing to achieve this initial goal, let to the discovery a side-channel that affects the security of a wide range of SMT implementations.
Summary
Secure message transmission (SMT) systems provide information theoretic security for point-to-point message transmission in networks that are partially controlled by an adversary. This is the story of a research project that aimed to implement a flavour of SMT protocols that uses "path hopping" with the goal of quantifying the real-life...
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The thundering herd: Amplifying kernel interference to attack response times
May 4, 2022
Conference Paper
Published in:
2022 IEEE 28th Real-Time and Embedded Technology and Applications Symp., RTAS, 4-6 May 2022.
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Embedded and real-time systems are increasingly attached to networks. This enables broader coordination beyond the physical system, but also opens the system to attacks. The increasingly complex workloads of these systems include software of varying assurance levels, including that which might be susceptible to compromise by remote attackers. To limit the impact of compromise, u-kernels focus on maintaining strong memory protection domains between different bodies of software, including system services. They enable limited coordination between processes through Inter-Process Communication (IPC). Real-time systems also require strong temporal guarantees for tasks, and thus need temporal isolation to limit the impact of malicious software. This is challenging as multiple client threads that use IPC to request service from a shared server will impact each other's response times. To constrain the temporal interference between threads, modern u-kernels often build priority and budget awareness into the system. Unfortunately, this paper demonstrates that this is more challenging than previously thought. Adding priority awareness to IPC processing can lead to significant interference due to the kernel's prioritization logic. Adding budget awareness similarly creates opportunities for interference due to the budget tracking and management operations. In both situations, a Thundering Herd of malicious threads can significantly delay the activation of mission-critical tasks. The Thundering Herd effects are evaluated on seL4 and results demonstrate that high-priority threads can be delayed by over 100,000 cycles per malicious thread. This paper reveals a challenging dilemma: the temporal protections u-kernels add can, themselves, provide means of threatening temporal isolation. Finally, to defend the system, we identify and empirically evaluate possible mitigations, and propose an admission-control test based upon an interference-aware analysis.
Summary
Embedded and real-time systems are increasingly attached to networks. This enables broader coordination beyond the physical system, but also opens the system to attacks. The increasingly complex workloads of these systems include software of varying assurance levels, including that which might be susceptible to compromise by remote attackers. To limit...
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Preventing Kernel Hacks with HAKCs
April 22, 2022
Conference Paper
Published in:
Network and Distributed System Security (NDSS) Symposium 2022.
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Commodity operating system kernels remain monolithic for practical and historical reasons. All kernel code shares a single address space, executes with elevated processor privileges, and has largely unhindered access to all data, including data irrelevant to the completion of a specific task. Applying the principle of least privilege, which limits available resources only to those needed to perform a particular task, to compartmentalize the kernel would realize major security gains, similar to microkernels yet without the major redesign effort. Here, we introduce a compartmentalization design, called a Hardware-Assisted Kernel Compartmentalization (HAKC), that approximates least privilege separation, while minimizing both developer effort and performance overhead. HAKC divides code and data into separate partitions, and specifies an access policy for each partition. Data is owned by a single partition, and a partition’s access-control policy is enforced at runtime, preventing unauthorized data access. When a partition needs to transfer control flow to outside itself, data ownership is transferred to the target, and transferred back upon return. The HAKC design allows for isolating code and data from the rest of the kernel, without utilizing any additional Trusted Computing Base while compartmentalized code is executing. Instead, HAKC relies on hardware for enforcement. Loadable kernel modules (LKMs), which dynamically load kernel code and data providing specialized functionality, are the single largest part of the Linux source base. Unfortunately, their collective size and complexity makes LKMs the cause of the majority of CVEs issued for the Linux kernel. The combination of a large attack surface in kernel modules, and the monolithic design of the Linux kernel, make LKMs ideal candidates for compartmentalization. To demonstrate the effectiveness of our approach, we implement HAKC in Linux v5.10 using extensions to the Arm v8.5-A ISA, and compartmentalize the ipv6.ko LKM, which consists of over 55k LOC. The average overhead measured in Apachebench tests was just 1.6%–24%. Additionally, we compartmentalize the nf_tables.ko packet filtering LKM, and measure the combined impact of using both LKMs. We find a reasonable linear growth in overhead when both compartmentalized LKMs are used. Finally, we measure no significant difference in performance when using the compartmentalized ipv6.ko LKM over the unmodified LKM during real-world web browsing experiments on the Alexa Top 50 websites.
Summary
Commodity operating system kernels remain monolithic for practical and historical reasons. All kernel code shares a single address space, executes with elevated processor privileges, and has largely unhindered access to all data, including data irrelevant to the completion of a specific task. Applying the principle of least privilege, which limits...
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Cross-language attacks
April 22, 2022
Conference Paper
Published in:
Network and Distributed System Security (NDSS) Symposium 2022.
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Memory corruption attacks against unsafe programming languages like C/C++ have been a major threat to computer systems for multiple decades. Various sanitizers and runtime exploit mitigation techniques have been shown to only provide partial protection at best. Recently developed ‘safe’ programming languages such as Rust and Go hold the promise to change this paradigm by preventing memory corruption bugs using a strong type system and proper compile-time and runtime checks. Gradual deployment of these languages has been touted as a way of improving the security of existing applications before entire applications can be developed in safe languages. This is notable in popular applications such as Firefox and Tor. In this paper, we systematically analyze the security of multi-language applications. We show that because language safety checks in safe languages and exploit mitigation techniques applied to unsafe languages (e.g., Control-Flow Integrity) break different stages of an exploit to prevent control hijacking attacks, an attacker can carefully maneuver between the languages to mount a successful attack. In essence, we illustrate that the incompatible set of assumptions made in various languages enables attacks that are not possible in each language alone. We study different variants of these attacks and analyze Firefox to illustrate the feasibility and extent of this problem. Our findings show that gradual deployment of safe programming languages, if not done with extreme care, can indeed be detrimental to security.
Summary
Memory corruption attacks against unsafe programming languages like C/C++ have been a major threat to computer systems for multiple decades. Various sanitizers and runtime exploit mitigation techniques have been shown to only provide partial protection at best. Recently developed ‘safe’ programming languages such as Rust and Go hold the promise...
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Keeping Safe Rust safe with Galeed
December 6, 2021
Conference Paper
Published in:
Annual Computer Security Applications Conf., ACSAC, December 2021, pp. 824-36.
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Rust is a programming language that simultaneously offers high performance and strong security guarantees. Safe Rust (i.e., Rust code that does not use the unsafe keyword) is memory and type safe. However, these guarantees are violated when safe Rust interacts with unsafe code, most notably code written in other programming languages, including in legacy C/C++ applications that are incrementally deploying Rust. This is a significant problem as major applications such as Firefox, Chrome, AWS, Windows, and Linux have either deployed Rust or are exploring doing so. It is important to emphasize that unsafe code is not only unsafe itself, but also it breaks the safety guarantees of ‘safe’ Rust; e.g., a dangling pointer in a linked C/C++ library can access and overwrite memory allocated to Rust even when the Rust code is fully safe. This paper presents Galeed, a technique to keep safe Rust safe from interference from unsafe code. Galeed has two components: a runtime defense to prevent unintended interactions between safe Rust and unsafe code and a sanitizer to secure intended interactions. The runtime component works by isolating Rust’s heap from any external access and is enforced using Intel Memory Protection Key (MPK) technology. The sanitizer uses a smart data structure that we call pseudo-pointer along with automated code transformation to avoid passing raw pointers across safe/unsafe boundaries during intended interactions (e.g., when Rust and C++ code exchange data). We implement and evaluate the effectiveness and performance of Galeed via micro- and macro-benchmarking, and use it to secure a widely used component of Firefox.
Summary
Rust is a programming language that simultaneously offers high performance and strong security guarantees. Safe Rust (i.e., Rust code that does not use the unsafe keyword) is memory and type safe. However, these guarantees are violated when safe Rust interacts with unsafe code, most notably code written in other programming...
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Practical principle of least privilege for secure embedded systems
May 18, 2021
Conference Paper
Published in:
2021 IEEE 27th Real-Time and Embedded Technology and Applications Symp., RTAS. 18-21 May 2021.
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Many embedded systems have evolved from simple bare-metal control systems to highly complex network-connected systems. These systems increasingly demand rich and feature-full operating-systems (OS) functionalities. Furthermore, the network connectedness offers attack vectors that require stronger security designs. To that end, this paper defines a prototypical RTOS API called Patina that provides services common in featurerich OSes (e.g., Linux) but absent in more trustworthy u-kernel-based systems. Examples of such services include communication channels, timers, event management, and synchronization. Two Patina implementations are presented, one on Composite and the other on seL4, each of which is designed based on the Principle of Least Privilege (PoLP) to increase system security. This paper describes how each of these u-kernels affect the PoLP-based design, as well as discusses security and performance tradeoffs in the two implementations. Results of comprehensive evaluations demonstrate that the performance of the PoLP-based implementation of Patina offers comparable or superior performance to Linux, while offering heightened isolation.
Summary
Many embedded systems have evolved from simple bare-metal control systems to highly complex network-connected systems. These systems increasingly demand rich and feature-full operating-systems (OS) functionalities. Furthermore, the network connectedness offers attack vectors that require stronger security designs. To that end, this paper defines a prototypical RTOS API called Patina that...
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A cybersecurity moonshot
May 1, 2021
Journal Article
Published in:
IEEE Secur. Priv., Vol. 19, No. 3, May-June 2021, pp. 8-16.
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Cybersecurity needs radical rethinking to change its current landscape. This article charts a vision for a cybersecurity moonshot based on radical but feasible technologies that can prevent the largest classes of vulnerabilities in modern systems.
Summary
Cybersecurity needs radical rethinking to change its current landscape. This article charts a vision for a cybersecurity moonshot based on radical but feasible technologies that can prevent the largest classes of vulnerabilities in modern systems.
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