50 years of isolation

The traditional means for isolating applications from each other is via the use of operating system provided “process” abstraction facilities. However, as applications now consist of multiple fine-grained components, the traditional process abstraction model is proving to be insufficient in ensuring this isolation. Statistics indicate that a high percentage of software failure occurs due to propagation of component failures. These observations are further bolstered by the attempts by modern Internet browser application developers, for example, to adopt multi-process architectures in order to increase robustness. Therefore, a fresh look at the available options for isolating program components is necessary and this paper provides an overview of previous and current research on the area

The Android Platform Security Model

Android is the most widely deployed end-user focused operating system. With its growing set of use cases encompassing communication, navigation, media consumption, entertainment, finance, health, and access to sensors, actuators, cameras, or microphones, its underlying security model needs to address a host of practical threats in a wide variety of scenarios while being useful to non-security experts. The model needs to strike a difficult balance between security, privacy, and usability for end users, assurances for app developers, and system performance under tight hardware constraints. While many of the underlying design principles have implicitly informed the overall system architecture, access control mechanisms, and mitigation techniques, the Android security model has previously not been formally published. This paper aims to both document the abstract model and discuss its implications. Based on a definition of the threat model and Android ecosystem context in which it operates, we analyze how the different security measures in past and current Android implementations work together to mitigate these threats. There are some special cases in applying the security model, and we discuss such deliberate deviations from the abstract model

Stronger secrecy for network-facing applications through privilege reduction

Despite significant effort in improving software quality, vulnerabilities and bugs persist in applications. Attackers remotely exploit vulnerabilities in network-facing applications and then disclose and corrupt users' sensitive information that these applications process. Reducing privilege of application components helps to limit the harm that an attacker may cause if she exploits an application. Privilege reduction, i.e., the Principle of Least Privilege, is a fundamental technique that allows one to contain possible exploits of error-prone software components: it entails granting a software component the minimal privilege that it needs to operate. Applying this principle ensures that sensitive data is given only to those software components that indeed require processing such data. This thesis explores how to reduce the privilege of network-facing applications to provide stronger confidentiality and integrity guarantees for sensitive data. First, we look into applying privilege reduction to cryptographic protocol implementations. We address the vital and largely unexamined problem of how to structure implementations of cryptographic protocols to protect sensitive data even in the case when an attacker compromises untrusted components of a protocol implementation. As evidence that the problem is poorly understood, we identified two attacks which succeed in disclosing of sensitive data in two state-of-the-art, exploit-resistant cryptographic protocol implementations: the privilege-separated OpenSSH server and the HiStar/DStar DIFC-based SSL web server. We propose practical, general, system-independent principles for structuring protocol implementations to defend against these two attacks. We apply our principles to protect sensitive data from disclosure in the implementations of both the server and client sides of OpenSSH and of the OpenSSL library. Next, we explore how to reduce the privilege of language runtimes, e.g., the JavaScript language runtime, so as to minimize the risk of their compromise, and thus of the disclosure and corruption of sensitive information. Modern language runtimes are complex software involving such advanced techniques as just-in-time compilation, native-code support routines, garbage collection, and dynamic runtime optimizations. This complexity makes it hard to guarantee the safety of language runtimes, as evidenced by the frequency of the discovery of vulnerabilities in them. We provide new mechanisms that allow sandboxing language runtimes using Software-based Fault Isolation (SFI). In particular, we enable sandboxing of runtime code modification, which modern language runtimes depend on heavily for achieving high performance. We have applied our sandboxing techniques to the V8 Javascript engine on both the x86-32 and x86-64 architectures, and found that the techniques incur only moderate performance overhead. Finally, we apply privilege reduction within the web browser to secure sensitive data within web applications. Web browsers have become an attractive target for attackers because of their widespread use. There are two principal threats to a user's sensitive data in the browser environment: untrusted third-party extensions and untrusted web pages. Extensions execute with elevated privilege which allows them to read content within all web applications. Thus, a malicious extension author may write extension code that reads sensitive page content and sends it to a remote server he controls. Alternatively, a malicious page author may exploit an honest but buggy extension, thus leveraging its elevated privilege to disclose sensitive information from other origins. We propose enforcing privilege reduction policies on extension JavaScript code to protect web applications' sensitive data from malicious extensions and malicious pages. We designed ScriptPolice, a policy system for the Chrome browser's V8 JavaScript language runtime, to enforce flexible security policies on JavaScript execution. We restrict the privileges of a variety of extensions and contain any malicious activity whether introduced by design or injected by a malicious page. The overhead ScriptPolice incurs on extension execution is acceptable: the added page load latency caused by ScriptPolice is so short as to be virtually indistinguishable by users

SEUSS: rapid serverless deployment using environment snapshots

Modern FaaS systems perform well in the case of repeat executions when function working sets stay small. However, these platforms are less effective when applied to more complex, large-scale and dynamic workloads. In this paper, we introduce SEUSS (serverless execution via unikernel snapshot stacks), a new system-level approach for rapidly deploying serverless functions. Through our approach, we demonstrate orders of magnitude improvements in function start times and cacheability, which improves common re-execution paths while also unlocking previously-unsupported large-scale bursty workloads.Published versio

Not-a-Bot (NAB): Improving Service Availability in the Face of Botnet Attacks

A large fraction of email spam, distributed denial-of-service (DDoS) attacks, and click-fraud on web advertisements are caused by traffic sent from compromised machines that form botnets. This paper posits that by identifying human-generated traffic as such, one can service it with improved reliability or higher priority, mitigating the effects of botnet attacks. The key challenge is to identify human-generated traffic in the absence of strong unique identities. We develop NAB (``Not-A-Bot''), a system to approximately identify and certify human-generated activity. NAB uses a small trusted software component called an attester, which runs on the client machine with an untrusted OS and applications. The attester tags each request with an attestation if the request is made within a small amount of time of legitimate keyboard or mouse activity. The remote entity serving the request sends the request and attestation to a verifier, which checks the attestation and implements an application-specific policy for attested requests. Our implementation of the attester is within the Xen hypervisor. By analyzing traces of keyboard and mouse activity from 328 users at Intel, together with adversarial traces of spam, DDoS, and click-fraud activity, we estimate that NAB reduces the amount of spam that currently passes through a tuned spam filter by more than 92%, while not flagging any legitimate email as spam. NAB delivers similar benefits to legitimate requests under DDoS and click-fraud attacks

Execution transactions for defending against software failures: use and evaluation

We examine the problem of containing buffer overflow attacks in a safe and efficient manner. Briefly, we automatically augment source code to dynamically catch stack and heap-based buffer overflow and underflow attacks, and recover from them by allowing the program to continue execution. Our hypothesis is that we can treat each code function as a transaction that can be aborted when an attack is detected, without affecting the application's ability to correctly execute. Our approach allows us to enable selectively or disable components of this defensive mechanism in response to external events, allowing for a direct tradeoff between security and performance. We combine our defensive mechanism with a honeypot-like configuration to detect previously unknown attacks, automatically adapt an application's defensive posture at a negligible performance cost, and help determine worm signatures. Our scheme provides low impact on application performance, the ability to respond to attacks without human intervention, the capacity to handle previously unknown vulnerabilities, and the preservation of service availability. We implement a stand-alone tool, DYBOC, which we use to instrument a number of vulnerable applications. Our performance benchmarks indicate a slow-down of 20% for Apache in full-protection mode, and 1.2% with selective protection. We provide preliminary evidence toward the validity of our transactional hypothesis via two experiments: first, by applying our scheme to 17 vulnerable applications, successfully fixing 14 of them; second, by examining the behavior of Apache when each of 154 potentially vulnerable routines are made to fail, resulting in correct behavior in 139 cases (90%), with similar results for sshd (89%) and Bind (88%)

Sub-Operating Systems: A New Approach to Application Security

In the current highly interconnected computing environments, users regularly use insecure software. Many popular applications, such as Netscape Navigator and Microsoft Word, are targeted by hostile applets or malicious documents, and might therefore compromise the integrity of the system. Current operating systems are unable to protect their users from these kinds of attacks, since the hostile software is running with the user\u27s privileges and permissions. We introduce the notion of the SubOS, a process-specific protection mechanism. Under SubOS, any application that might deal with incoming, possibly malicious objects, behaves like an operating system. It views those objects the same way an operating system views users - it assigns sub-user id\u27s - and restricts their accesses to the system resources