Toward Secure Services from Untrusted Developers

We present a secure service prototype built from untrusted,contributed code.The service manages private data for a variety of different users, anduser programs frequently require access to other users' private data.However, aside from covert timing channels, no part of the service cancorrupt private data or leak it between users or outside the systemwithout permission from the data's owners.Instead, owners may choose to reveal their data in a controlled manner.This application model is demonstrated by Muenster, a job searchwebsite that protects both the integrity and secrecy of each user's data.In spite of running untrusted code, Muenster and other services canprevent overt leaks because the untrusted modules are constrained bythe operating system to follow pre-specified security policies, whichare nevertheless flexible enough for programmers to do useful work.We build Muenster atop Asbestos, a recently described operating systembased on a form of decentralized information flowcontrol

System call interface for Asbestos labels

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 53-55).Acetone is a secure operating system kernel that uses a shared address space and supports Asbestos labels. Acetone uses Asbestos labels to enable a wide variety of security policies including ones that prevent untrusted applications from being able to disclose private data. All threads run in the same address space, but have different memory access privileges. Acetone uses standard memory protection mechanisms to ensure that all memory accesses are consistent with label rules. The performance results show that these checks have a relatively low cost.by Clifford A. Frey.M.Eng

Making information flow explicit in HiStar

HiStar is a new operating system designed to minimize the amount of code that must be trusted. HiStar provides strict information flow control, which allows users to specify precise data security policies without unduly limiting the structure of applications. HiStar's security features make it possible to implement a Unix-like environment with acceptable performance almost entirely in an untrusted user-level library. The system has no notion of superuser and no fully trusted code other than the kernel. HiStar's features permit several novel applications, including privacy-preserving, untrusted virus scanners and a dynamic Web server with only a few thousand lines of trusted code.National Science Foundation (U.S.) (Cybertrust Award CNS-0716806)National Science Foundation (U.S.) (Cybertrust/DARPA Grant CNS-0430425

Privaros: A Framework for Privacy-Compliant Delivery Drones

We present Privaros, a framework to enforce privacy policies on drones. Privaros is designed for commercial delivery drones, such as the ones that will likely be used by Amazon Prime Air. Such drones visit a number of host airspaces, each of which may have different privacy requirements. Privaros provides an information flow control framework to enforce the policies of these hosts on the guest delivery drones. The mechanisms in Privaros are built on top of ROS, a middleware popular in many drone platforms. This paper presents the design and implementation of these mechanisms, describes how policies are specified, and shows that Privaros's policy specification can be integrated with India's Digital Sky portal. Our evaluation shows that a drone running Privaros can robustly enforce various privacy policies specified by hosts, and that its core mechanisms only marginally increase communication latency and power consumption

Attacker Control and Impact for Confidentiality and Integrity

Language-based information flow methods offer a principled way to enforce strong security properties, but enforcing noninterference is too inflexible for realistic applications. Security-typed languages have therefore introduced declassification mechanisms for relaxing confidentiality policies, and endorsement mechanisms for relaxing integrity policies. However, a continuing challenge has been to define what security is guaranteed when such mechanisms are used. This paper presents a new semantic framework for expressing security policies for declassification and endorsement in a language-based setting. The key insight is that security can be characterized in terms of the influence that declassification and endorsement allow to the attacker. The new framework introduces two notions of security to describe the influence of the attacker. Attacker control defines what the attacker is able to learn from observable effects of this code; attacker impact captures the attacker's influence on trusted locations. This approach yields novel security conditions for checked endorsements and robust integrity. The framework is flexible enough to recover and to improve on the previously introduced notions of robustness and qualified robustness. Further, the new security conditions can be soundly enforced by a security type system. The applicability and enforcement of the new policies is illustrated through various examples, including data sanitization and authentication

Confidentiality and Integrity with Untrusted Hosts: Technical Report

Several security-typed languages have recently been proposed to enforce security properties such as confidentiality or integrity by type checking. We propose a new security-typed language, SPL@, that addresses two important limitations of previous approaches. First, existing languages assume that the underlying execution platform is trusted; this assumption does not scale to distributed computation in which a variety of differently trusted hosts are available to execute programs. Our new approach, secure program partitioning, translates programs written assuming complete trust in a single executing host into programs that execute using a collection of variously trusted hosts to perform computation. As the trust configuration of a distributed system evolves, this translation can be performed as necessary for security. Second, many common program transformations do not work in existing security-typed languages; although they produce equivalent programs, these programs are rejected because of apparent information flows. SPL@ uses a novel mechanism based on ordered linear continuations to permit a richer class of program transformations, including secure program partitioning. This report is the technical companion to [ZM00]. It contains expanded discussion and extensive proofs of both the soundness and noninterference theorems mentioned in Section 3.3 of that work

Comprehensive and Practical Policy Compliance in Data Retrieval Systems

Data retrieval systems such as online search engines and online social networks process many data items coming from different sources, each subject to its own data use policy. Ensuring compliance with these policies in a large and fast-evolving system presents a significant technical challenge since bugs, misconfigurations, or operator errors can cause (accidental) policy violations. To prevent such violations, researchers and practitioners develop policy compliance systems. Existing policy compliance systems, however, are either not comprehensive or not practical. To be comprehensive, a compliance system must be able to enforce users' policies regarding their personal privacy preferences, the service provider's own policies regarding data use such as auditing and personalization, and regulatory policies such as data retention and censorship. To be practical, a compliance system needs to meet stringent requirements: (1) runtime overhead must be low; (2) existing applications must run with few modifications; and (3) bugs, misconfigurations, or actions by unprivileged operators must not cause policy violations. In this thesis, we present the design and implementation of two comprehensive and practical compliance systems: Thoth and Shai. Thoth relies on pure runtime monitoring: it tracks data flows by intercepting processes' I/O, and then it checks the associated policies to allow only policy-compliant flows at runtime. Shai, on the other hand, combines offline analysis and light-weight runtime monitoring: it pushes as many policy checks as possible to an offline (flow) analysis by predicting the policies that data-handling processes will be subject to at runtime, and then it compiles those policies into a set of fine-grained I/O capabilities that can be enforced directly by the underlying operating system

Tags: Augmenting Microkernel Messages with Lightweight Metadata

In this work, we propose Tags, an e cient mechanism that augments microkernel interprocess messages with lightweight metadata to enable the development of new, systemwide functionality without requiring the modi cation of application source code. Therefore, the technology is well suited for systems with a large legacy code base and for third-party applications such as phone and tablet applications. As examples, we detailed use cases in areas consisting of mandatory security and runtime veri cation of process interactions. In the area of mandatory security, we use tagging to assess the feasibility of implementing a mandatory integrity propagation model in the microkernel. The process interaction veri cation use case shows the utility of tagging to track and verify interaction history among system components. To demonstrate that tagging is technically feasible and practical, we implemented it in a commercial microkernel and executed multiple sets of standard benchmarks on two di erent computing architectures. The results clearly demonstrate that tagging has only negligible overhead and strong potential for many applications

Information flow control for secure web sites

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (leaves 117-125).Sometimes Web sites fail in the worst ways. They can reveal private data that can never be retracted [60, 72, 78, 79]. Or they can succumb to vandalism, and subsequently show corrupt data to users [27]. Blame can fall on the off-the-shelf software that runs the site (e.g., the operating system, the application libraries, the Web server, etc.), but more frequently (as in the above references), the custom application code is the guilty party. Unfortunately, the custom code behind many Web sites is difficult to secure and audit, due to large and rapidly-changing trusted computing bases (TCBs). A promising approach to reducing TCBs for Web sites is decentralized information flow control (DIFC) [21, 69, 113]. DIFC allows the split of a Web application into two types of components: those inside the TCB (trusted), and those without (untrusted). The untrusted components are large, change frequently, and do most of the computation. Even if buggy, they cannot move data contrary to security policy. Trusted components are much smaller, and configure the Web site's security policies. They need only change when the policy changes, and not when new features are introduced. Bugs in the trusted code can lead to compromise, but the trusted code is smaller and therefore easier to audit. The drawback of DIFC, up to now, is that the approach requires a major shift in how programmers develop applications and thus remains inaccessible to programmers using today's proven programming abstractions. This thesis proposes a new DIFC system, Flume, that brings DIFC controls to the operating systems and programming languages in wide use today. Its key contributions are: (1) a simplified DIFC model with provable security guarantees; (2) a new primitive called endpoints that bridges the gap between the Flume DIFC model and standard operating systems interfaces; (3) an implementation at user-level on Linux; and (4) success in securing a popular preexisting Web application (MoinMoin Wiki).by Maxwell Norman Krohn.Ph.D

Information Flow for Secure Distributed Applications

PhD thesisPrivate and confidential information is increasingly stored online and increasingly being exposed due to human errors as well as malicious attacks. Information leaks threaten confidentiality, lead to lawsuits, damage enterprise reputations, and cost billion of dollars. While distributed computing architectures provide data and service integration, they also create information flow control problems due to the interaction complexity among service providers. A main problem is the lack of an appropriate programming model to capture expected information flow behaviors in these large distributed software infrastructures. This research tackles this problem by proposing a programming methodology and enforcement platform for application developers to protect and share their sensitive data. We introduce Aeolus, a new platform intended to make it easier to build distributed applications that avoid the unauthorized release of information. The Aeolus security model is based on information flow control but differs from previous work in ways that we believe make it easier to use and understand. In addition, Aeolus provides a number of new mechanisms (anonymous closures, compound tags, boxes, and shared volatile state) to ease the job of writing applications. This thesis provides examples to show how Aeolus features support secure distributed applications. It describes the system design issues and solutions in designing a prototype implementation and presents performance results that show our platform has low overhead