Software released in binary form frequently uses third-party packages without respecting their licensing terms. For instance, many consumer devices have firmware containing the Linux kernel, without the suppliers following the requirements of the GNU General Public License. Such license violations are often accidental, e.g., when vendors receive binary code from their suppliers with no indication of its provenance. To help find such violations, we have developed the Binary Analysis Tool (BAT), a system for code clone detection in binaries. Given a binary, such as a firmware image, it attempts to detect cloning of code from repositories of packages in source and binary form. We evaluate and compare the effectiveness of three of BAT's clone detection techniques: scanning for string literals, detecting similarity through data compression, and detecting similarity by computing binary deltas.

Existing package and system configuration management tools suffer from an imperative model, where system administration actions such as package upgrades or changes to system configuration files are stateful: they destructively update the state of the system. This leads to many problems, such as the inability to roll back changes easily, to deploy multiple versions of a package side-by-side, to reproduce a configuration deterministically on another machine, or to reliably upgrade a system. In this paper we show that we can overcome these problems by moving to a purely functional system configuration model. This means that all static parts of a system (such as software packages, configuration files and system startup scripts) are built by pure functions and are immutable, stored in a way analogous to a heap in a purely functional language. We have implemented this model in NixOS, a non-trivial Linux distribution that uses the Nix package manager to build the entire system configuration from a modular, purely functional specification.

The deployment of software components frequently fails because dependencies on other components are not declared explicitly or are declared imprecisely. This results in an incomplete reproduction of the environment necessary for proper operation, or in interference between incompatible variants. In this paper we show that these deployment hazards are similar to pointer hazards in memory models of programming languages and can be countered by imposing a memory management discipline on software deployment. Based on this analysis we have developed a generic, platform and language independent, discipline for deployment that allows precise dependency verification; exact identification of component variants; computation of complete closures containing all components on which a component depends; maximal sharing of components between such closures; and concurrent installation of revisions and variants of components.We have implemented the approach in the Nix deployment system, and used it for the deployment of a large number of existing Linux packages. We compare its effectiveness to other deployment systems.

Abstract-Graphical user interfaces are difficult to test: automated tests are hard to create and maintain, while manual tests are time-consuming, expensive and hard to integrate in a continuous testing process. In this paper, we show that it is possible to crowdsource GUI tests, that is, to outsource them to individuals drawn from a very large pool of workers on the Internet. This is made possible by instantiating virtual machines running the system under test and letting testers access the VMs through their web browsers, enabling semi-automated continuous testing of GUIs and usability experiments with large numbers of participants at low cost. Several large experiments on the Amazon Mechanical Turk demonstrate that our approach is technically feasible and sufficiently reliable.

Software written in one language often needs to construct sentences in another language, such as SQL queries, XML output, or shell command invocations. This is almost always done using unhygienic string manipulation, the concatenation of constants and client-supplied strings. A client can then supply specially crafted input that causes the constructed sentence to be interpreted in an unintended way, leading to an injection attack. We describe a more natural style of programming that yields code that is impervious to injections by construction. Our approach embeds the grammars of the guest languages (e.g., SQL) into that of the host language (e.g., Java) and automatically generates code that maps the embedded language to constructs in the host language that reconstruct the embedded sentences, adding escaping functions where appropriate. This approach is generic, meaning that it can be applied with relative ease to any combination of host and guest languages.