EROS is a capability-based operating system for commodity processors which uses a single level storage model. The single level store's persistence is transparent to applications. The performance consequences of support for transparent persistence and capability-based architectures are generally believed to be negative. Surprisingly, the basic operations of EROS (such as IPC) are generally comparable in cost to similar operations in conventional systems. This is demonstrated with a set of microbenchmark measurements of semantically similar operations in Linux. The EROS system achieves its performance by coupling well-chosen abstract objects with caching techniques for those objects. The objects (processes, nodes, and pages) are well-supported by conventional hardware, reducing the overhead of capabilities. Software-managed caching techniques for these objects reduce the cost of persistence. The resulting performance suggests that composing protected subsystems may be less costly than c...

Most systems contain software with yet-to-be-discovered security vulnerabilities. When a vulnerability is disclosed, administrators face the grim reality that they have been running software which was open to attack. Sites that value availability may be forced to continue running this vulnerable software until the accompanying patch has been tested. Our goal is to improve security by detecting intrusions that occurred before the vulnerability was disclosed and by detecting and responding to intrusions that are attempted after the vulnerability is disclosed. We detect when a vulnerability is triggered by executing vulnerability-specific predicates as the system runs or replays. This paper describes the design, implementation and evaluation of a system that supports the construction and execution of these vulnerability-specific predicates. Our system, called Intro-Virt, uses virtual-machine introspection to monitor the execution of application and operating system software. Intro-Virt executes predicates over past execution periods by combining virtual-machine introspection with virtual-machine replay. IntroVirt eases the construction of powerful predicates by allowing predicates to run existing target code in the context of the target system, and it uses checkpoints so that predicates can execute target code without perturbing the state of the target system. IntroVirt allows predicates to refresh themselves automatically so they work in the presence of preemptions. We show that vulnerabilityspecific predicates can be written easily for a wide variety of real vulnerabilities, can detect and respond to intrusions over both the past and present time intervals, and add little overhead for most vulnerabilities.

National Security Agency Although public awareness of the need for security in computing systems is growing rapidly, current efforts to provide security are unlikely to succeed. Current security efforts suffer from the flawed assumption that adequate security can be provided in applications with the existing security mechanisms of mainstream operating systems. In reality, the need for secure operating systems is growing in today’s computing environment due to substantial increases in connectivity and data sharing. The goal of this paper is to motivate a renewed interest in secure operating systems so that future security efforts may build on a solid foundation. This paper identifies several secure operating system features which are lacking in mainstream operating systems, argues that these features are necessary to adequately protect general application-space security mechanisms, and provides concrete examples of how current security solutions are critically dependent on these features.

Users regularly exchange apparently innocuous data files using email and ftp. While the users view these data as passive, there are situations when they are interpreted as code by some system application. In that case the data become “active”. Some examples of such data are Java, JavaScript and Microsoft Word attachments, each of which are executed within the security context of the user, allowing potentially arbitrary machine access. The structure of current operating systems and user applications makes solving this problem challenging. We propose a new protection mechanism to address active content, which applies fine-grained access controls at the level of individual data objects. All data objects arriving from remote sources are tagged with a non-removable identifier. This identifier dictates its permissions and privileges rather than the file owner’s user ID. Since users possess many objects, the system provides far more precise access control policies to be enforced, and at a far finer granularity than previous designs. 1

Users frequently have to choose between functionality and security. When running popular Web browsers or email clients, they frequently find themselves turning off features such as JavaScript, only to switch them back on in order to view a certain site or read a particular message. Users of Unix (or similar) systems can construct a sandbox where such programs execute in a restricted environment. Creating such a sandbox is not trivial; one has to determine what files or services to place within the sandbox to facilitate the execution of the application. In this paper we describe a portable system that tracks the file requests made by applications creating an access log. The same system can then use the access log as a template to regulate file access requests made by sandboxed applications. We present an example of how this system was used to place Netscape Navigator in a sandbox. 1.

Trust management credentials directly authorize actions, rather than divide the authorization task into authentication and access control. Unlike traditional credentials, which bind keys to principals, trust management credentials bind keys to the authorization to perform certain tasks.

Dean and Hu proposed a probabilistic countermeasure to the classic access(2)/open(2) TOCTTOU race condition in privileged Unix programs [4]. In this paper, we describe an attack that succeeds with very high probability against their countermeasure. We then consider a stronger randomized variant of their defense and show that it, too, is broken. We conclude that access(2) must never be used in privileged Unix programs. The tools we develop can be used to attack other filesystem races, underscoring the importance of avoiding such races in secure software. 1

(email: fjaegert,jochen,vvp,yoonho,nayeemg @ watson.ibm.com) We present a security architecture that system administrators, users, and application developers can use to

The value of data used in computation is increasing more rapidly than the security of the computation environment. Users are submitting private personal and financial information to untrusted programs, even though the programs cannot guarantee the privacy of that information. This problem is even more pronounced for programs that are provided through the Internet, such as servlets and applets.

We defeat two proposed Unix file-system race condition defense mechanisms. First, we attack the probabilistic defense mechanism of Tsafrir, et al., published at USENIX FAST 2008[26]. We then show that the same attack breaks the kernel-based dynamic race detector of Tsyrklevich and Yee, published at USENIX Security 2003[28]. We then argue that all kernel-based dynamic race detectors must have a model of the programs they protect or provide imperfect protection. The techniques we develop for performing these attacks work on multiple Unix operating systems, on uni- and multi-processors, and are useful for exploiting most Unix file-system races. We conclude that programmers should use provably-secure methods for avoiding race conditions when accessing the file-system. 1.