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Recent device hardware trends enable a new approach to the design of network server operating systems. In a traditional operating system, the kernel mediates access to device hardware by server applications, to enforce process isolation as well as network and disk security.We have designed and implemented a new operating system, Arrakis, that splits the traditional role of the kernel in two. Applications have direct access to virtualized I/O devices, allowing most I/O operations to skip the kernel entirely, while the kernel is re-engineered to provide network and disk protection without kernel mediation of every operation.We describe the hardware and software changes needed to take advantage of this new abstraction, and we illustrate its power by showing improvements of 2-5 in latency and 9 in throughput for a popular persistent NoSQL store relative to a well-tuned Linux implementation. We present Barrelfish/DC, an extension to the Barrelfish OS which decouples physical cores from a native OS kernel, and furthermore the kernel itself from the rest of the OS and application state. In Barrelfish/DC, native kernel code on any core can be quickly replaced, kernel state moved between cores, and cores added and removed from the system transparently to applications and OS processes, which continue to execute.
Barrelfish/DC is a multikernel with two novel ideas: the use of boot drivers to abstract cores as regular devices, and a partitioned capability system for memory management which externalizes core-local kernel state. We show by performance measurements of real applications and device drivers that the approach is practical enough to be used for a number of purposes, such as online kernel upgrades, and temporarily delivering hard real-time performance by executing a process under a specialized, single-application kernel. Modern operating systems run multiple interpreters in the kernel, which enable user-space applications to add new functionality or specialize system policies. The correctness of such interpreters is critical to the overall system security: bugs in interpreters could allow adversaries to compromise user-space applications and even the kernel. Jitk is a new infrastructure for building in-kernel interpreters that guarantee functional correctness as they compile user-space policies down to native instructions for execution in the kernel.
To demonstrate Jitk, we implement two interpreters in the Linux kernel, BPF and INET-DIAG, which are used for network and system call filtering and socket monitoring, respectively. To help application developers write correct filters, we introduce a high-level rule language, along with a proof that Jitk correctly translates high-level rules all the way to native machine code, and demonstrate that this language can be integrated into OpenSSH with tens of lines of code. We built a prototype of Jitk on top of the CompCert verified compiler and integrated it into the Linux kernel. Experimental results show that Jitk is practical, fast, and trustworthy. The conventional wisdom is that aggressive networking requirements, such as high packet rates for small messages and microsecond-scale tail latency, are best addressed outside the kernel, in a user-level networking stack. We present IX, a dataplane operating system that provides high I/O performance, while maintaining the key advantage of strong protection offered by existing kernels. IX uses hardware virtualization to separate management and scheduling functions of the kernel (control plane) from network processing (dataplane).
The dataplane architecture builds upon a native, zero-copy API and optimizes for both bandwidth and latency by dedicating hardware threads and networking queues to dataplane instances, processing bounded batches of packets to completion, and by eliminating coherence traffic and multi-core synchronization. We demonstrate that IX outperforms Linux and state-of-the-art, user-space network stacks significantly in both throughput and end-to-end latency.
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Moreover, IX improves the throughput of a widely deployed, key-value store by up to 3.6 and reduces tail latency by more than 2. We explore the potential of making programmability a central feature of the SSD interface. Our prototype system, called Willow, allows programmers to augment and extend the semantics of an SSD with application-specific features without compromising file system protections. The SSD Apps running on Willow give applications lowlatency, high-bandwidth access to the SSD’s contents while reducing the load that IO processing places on the host processor. The programming model for SSD Apps provides great flexibility, supports the concurrent execution of multiple SSD Apps in Willow, and supports the execution of trusted code in Willow. We demonstrate the effectiveness and flexibility of Willow by implementing six SSD Apps and measuring their performance.
We find that defining SSD semantics in software is easy and beneficial, and thatWillow makes it feasible for a wide range of IO-intensive applications to benefit from a customized SSD interface. We introduce IceFS, a novel file system that separates physical structures of the file system.
A new abstraction, the cube, is provided to enable the grouping of files and directories inside a physically isolated container. We show three major benefits of cubes within IceFS: localized reaction to faults, fast recovery, and concurrent filesystem updates. Evinrude manual tilt. We demonstrate these benefits within a VMware-based virtualized environment and within the Hadoop distributed file system.
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Results show that our prototype can significantly improve availability and performance, sometimes by an order of magnitude. Modern applications face new challenges in managing today’s highly distributed and heterogeneous environment. For example, they must stitch together code that crosses smartphones, tablets, personal devices, and cloud services, connected by variable wide-area networks, such as WiFi and 4G. This paper describes Sapphire, a distributed programming platform that simplifies the programming of today’s mobile/cloud applications. Sapphire’s key design feature is its distributed runtime system, which supports a flexible and extensible deployment layer for solving complex distributed systems tasks, such as fault-tolerance, code-offloading, and caching. Rather than writing distributed systems code, programmers choose deployment managers that extend Sapphire’s kernel to meet their applications’ deployment requirements.
In this way, each application runs on an underlying platform that is customized for its own distribution needs. Support for fine-grained data management has all but disappeared from modern operating systems such as Android and iOS. Instead, we must rely on each individual application to manage our data properly – e.g., to delete our emails, documents, and photos in full upon request; to not collect more data than required for its function; and to back up our data to reliable backends. Yet, research studies and media articles constantly remind us of the poor data management practices applied by our applications. We have developed Pebbles, a fine-grained data management system that enables management at a powerful new level of abstraction: application-level data objects, such as emails, documents, notes, notebooks, bank accounts, etc. The key contribution is Pebbles’s ability to discover such high-level objects in arbitrary applications without requiring any input from or modifications to these applications.
Intuitively, it seems impossible for an OS-level service to understand object structures in unmodified applications, however we observe that the high-level storage abstractions embedded in modern OSes – relational databases and object-relational mappers – bear significant structural information that makes object recognition possible and accurate. Modern web applications are conglomerations of JavaScript written by multiple authors: application developers routinely incorporate code from third-party libraries, and mashup applications synthesize data and code hosted at different sites. In current browsers, a web application’s developer and user must trust third-party code in libraries not to leak the user’s sensitive information from within applications. Even worse, in the status quo, the only way to implement some mashups is for the user to give her login credentials for one site to the operator of another site.
Fundamentally, today’s browser security model trades privacy for flexibility because it lacks a sufficient mechanism for confining untrusted code. We present COWL, a robust JavaScript confinement system for modern web browsers. COWL introduces label-based mandatory access control to browsing contexts in a way that is fully backwardcompatible with legacy web content. We use a series of case-study applications to motivate COWL’s design and demonstrate how COWL allows both the inclusion of untrusted scripts in applications and the building of mashups that combine sensitive information from multiple mutually distrusting origins, all while protecting users’ privacy. Measurements of two COWL implementations, one in Firefox and one in Chromium, demonstrate a virtually imperceptible increase in page-load latency.
Systems code is often written in low-level languages like C/C, which offer many benefits but also delegate memory management to programmers. This invites memory safety bugs that attackers can exploit to divert control flow and compromise the system. Deployed defense mechanisms (e.g., ASLR, DEP) are incomplete, and stronger defense mechanisms (e.g., CFI) often have high overhead and limited guarantees 19, 15, 9. We introduce code-pointer integrity (CPI), a new design point that guarantees the integrity of all code pointers in a program (e.g., function pointers, saved return addresses) and thereby prevents all control-flow hijack attacks, including return-oriented programming. We also introduce code-pointer separation (CPS), a relaxation of CPI with better performance properties. CPI and CPS offer substantially better security-to-overhead ratios than the state of the art, they are practical (we protect a complete FreeBSD system and over 100 packages like apache and postgresql), effective (prevent all attacks in the RIPE benchmark), and efficient: on SPEC CPU2006, CPS averages 1.2% overhead for C and 1.9% for C/C, while CPI’s overhead is 2.9% for C and 8.4% for C/C. A prototype implementation of CPI and CPS can be obtained from.
An Ironclad App lets a user securely transmit her data to a remote machine with the guarantee that every instruction executed on that machine adheres to a formal abstract specification of the app’s behavior. This does more than eliminate implementation vulnerabilities such as buffer overflows, parsing errors, or data leaks; it tells the user exactly how the app will behave at all times. We provide these guarantees via complete, low-level software verification. We then use cryptography and secure hardware to enable secure channels from the verified software to remote users. To achieve such complete verification, we developed a set of new and modified tools, a collection of techniques and engineering disciplines, and a methodology focused on rapid development of verified systems software. We describe our methodology, formal results, and lessons we learned from building a full stack of verified software. That software includes a verified kernel; verified drivers; verified system and crypto libraries including SHA, HMAC, and RSA; and four Ironclad Apps.
The Principle of Least Privilege suggests that software should be executed with no more authority than it requires to accomplish its task. Current security tools make it difficult to apply this principle: they either require significant modifications to applications or do not facilitate reasoning about combining untrustworthy components. We propose SHILL, a secure shell scripting language. SHILL scripts enable compositional reasoning about security through contracts that limit the effects of script execution, including the effects of programs invoked by the script. SHILL contracts are declarative security policies that act as documentation for consumers of SHILL scripts, and are enforced through a combination of language design and sandboxing.
We have implemented a prototype of SHILL for FreeBSD and used it for several case studies including a grading script and a script to download, compile, and install software. Our experience indicates that SHILL is a practical and useful system security tool, and can provide fine-grained security guarantees.