Improving application security with data flow assertions

Resin is a new language runtime that helps prevent security vulnerabilities, by allowing programmers to specify application-level data flow assertions. Resin provides policy objects, which programmers use to specify assertion code and metadata; data tracking, which allows programmers to associate assertions with application data, and to keep track of assertions as the data flow through the application; and filter objects, which programmers use to define data flow boundaries at which assertions are checked. Resin's runtime checks data flow assertions by propagating policy objects along with data, as that data moves through the application, and then invoking filter objects when data crosses a data flow boundary, such as when writing data to the network or a file. Using Resin, Web application programmers can prevent a range of problems, from SQL injection and cross-site scripting, to inadvertent password disclosure and missing access control checks. Adding a Resin assertion to an application requires few changes to the existing application code, and an assertion can reuse existing code and data structures. For instance, 23 lines of code detect and prevent three previously-unknown missing access control vulnerabilities in phpBB, a popular Web forum application. Other assertions comprising tens of lines of code prevent a range of vulnerabilities in Python and PHP applications. A prototype of Resin incurs a 33% CPU overhead running the HotCRP conference management application.Nokia Researc

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

Improving web site security with data flow management

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 91-98).This dissertation describes two systems, RESIN and BFLow, whose goal is to help Web developers build more secure Web sites. RESIN and BFLOW use data flow management to help reduce the security risks of using buggy or malicious code. RESIN provides programmers with language-level mechanisms to track and manage the flow of data within the server. These mechanisms make it easy for programmers to catch server-side data flow bugs that result in security vulnerabilities, and prevent these bugs from being exploited. BFLow is a system that adds information flow control, a restrictive form of data flow management, both to the Web browser and to the interface between a browser and a server. BFLOW makes it possible for a Web site to combine confidential data with untrusted JavaScript in its Web pages, without risking leaks of that data. This work makes a number of contributions. RESIN introduces the idea of a data flow assertion and demonstrates how to build them using three language-level mechanisms, policy objects, data tracking, and filter objects. We built prototype implementations of RESIN in both the PHP and Python runtimes. We adapt seven real off-the-shelf applications and implement 11 different security policies in RESIN which thwart at least 27 real security vulnerabilities. BFLow introduces an information flow control model that fits the JavaScript communication mechanisms, and a system that maps that model to JavaScript's existing isolation system.(cont.) Together, these techniques allow untrusted JavaScript to read, compute with, and display confidential data without the risk of leaking that data, yet requires only minor changes to existing software. We built a prototype of the BFLow system and three different applications including a social networking application, a novel shared-data Web platform, and BFlogger, a third-party JavaScript platform similar to that of Blogger.com. We ported several untrusted JavaScript extensions from Blogger.com to BFlogger, and show that the extensions cannot leak data as they can in Blogger.com.by Alexander Siumann Yip.Ph.D

Small TCBs of policy-controlled operating systems

IT Systeme mit qualitativ hohen Sicherheitsanforderungen verwenden zur Beschreibung, Analyse und Implementierung ihrer Sicherheitseigenschaften zunehmend problemspezifische Sicherheitspolitiken, welche ein wesentlicher Bestandteil der Trusted Computing Base (TCB) eines IT Systems sind. Aus diesem Grund sind die Korrektheit und Unumgehbarkeit der Implementierung einer TCB entscheidend, um die geforderten Sicherheitseigenschaften eines Systems herzustellen, zu wahren und zu garantieren. Viele der heutigen Betriebssysteme zeigen, welche Herausforderung die Realisierung von Sicherheitspolitiken darstellt; seit mehr als 40 Jahren unterstützen sie wahlfreie identitätsbasierte Zugriffssteuerungspolitiken nur rudimentär. Dies führt dazu, dass große Teile der Sicherheitspolitiken von Anwendersoftware durch die Anwendungen selbst implementiert werden. Infolge dessen sind die TCBs heutiger Betriebssysteme groß, heterogen und verteilt, so dass die exakte Bestimmung ihres Funktionsumfangs sehr aufwendig ist. Im Ergebnis sind die wesentlichen Eigenschaften von TCBs - Korrektheit, Robustheit und Unumgehbarkeit - nur schwer erreichbar. Dies hat zur Entwicklung von Politik gesteuerten Betriebssystemen geführt, die alle Sicherheitspolitiken eines Betriebssystems und seiner Anwendungen zentral zusammenfassen, indem sie Kernabstraktionen für Sicherheitspolitiken und Politiklaufzeitumgebungen anbieten. Aktuelle Politik gesteuerte Betriebssysteme basieren auf monolithischen Architekturen, was dazu führt, dass ihre Komponenten zur Durchsetzung ihrer Politiken im Betriebssystemkern verteilt sind. Weiterhin verfolgen sie das Ziel, ein möglichst breites Spektrum an Sicherheitspolitiken zu unterstützen. Dies hat zur Folge, dass ihre Laufzeitkomponenten für Politikentscheidung und -durchsetzung universal sind. Im Ergebnis sind ihre TCB-Implementierungen groß und komplex, so dass der TCB- Funktionsumfang nur schwer identifiziert werden kann und wesentliche Eigenschaften von TCBs nur mit erhöhtem Aufwand erreichbar sind. Diese Dissertation verfolgt einen Ansatz, der die TCBs Politik gesteuerter Betriebssysteme systematisch entwickelt. Die Idee ist, das Laufzeitsystem für Sicherheitspolitiken so maßzuschneidern, dass nur die Politiken unterstützt werden, die tatsächlich in einer TCB vorhanden sind. Dabei wird der Funktionsumfang einer TCB durch kausale Abhängigkeiten zwischen Sicherheitspolitiken und TCB-Funktionen bestimmt. Das Ergebnis sind kausale TCBs, die nur diejenigen Funktionen enthalten, die zum Durchsetzen und zum Schutz der vorhandenen Sicherheitspolitiken notwendig sind. Die präzise Identifikation von TCB-Funktionen erlaubt, die Implementierung der TCB-Funktionen von nicht-vertrauenswürdigen Systemkomponenten zu isolieren. Dadurch legen kausale TCBs die Grundlage für TCB-Implementierungen, deren Größe und Komplexität eine Analyse und Verifikation bezüglich ihrer Korrektheit und Unumgehbarkeit ermöglichen. Kausale TCBs haben ein breites Anwendungsspektrum - von eingebetteten Systemen über Politik gesteuerte Betriebssysteme bis hin zu Datenbankmanagementsystemen in großen Informationssystemen.Policy-controlled operating systems provide a policy decision and enforcement environment to protect and enforce their security policies. The trusted computing base (TCB) of these systems are large and complex, and their functional perimeter can hardly be precisely identified. As a result, a TCB's correctness and tamper-proofness are hard to ensure in its implementation. This dissertation develops a TCB engineering method for policy-controlled operating systems that tailors the policy decision and enforcement environment to support only those policies that are actually present in a TCB. A TCB's functional perimeter is identified by exploiting causal dependencies between policies and TCB functions, which results in causal TCBs that contain exactly those functions that are necessary to establish, enforce, and protect their policies. The precise identification of a TCB's functional perimeter allows for implementing a TCB in a safe environment that indeed can be isolated from untrusted system components. Thereby, causal TCB engineering sets the course for implementations whose size and complexity pave the way for analyzing and verifying a TCB's correctness and tamper-proofness.Auch im Buchhandel erhältlich: Small TCBs of policy-controlled operating systems / Anja Pölck Ilmenau : Univ.-Verl. Ilmenau, 2014. - xiii, 249 S. ISBN 978-3-86360-090-7 Preis: 24,40