Web applications written in languages such as PHP and JSP are notoriously vulnerable to accidentally omitted authorization checks and other security bugs. Existing techniques that find missing security checks in library and system code assume that (1) security checks can be recognized syntactically and (2) the same pattern of checks applies universally to all programs. These assumptions do not hold for Web applications. Each Web application uses different variables and logic to check the user’s permissions. Even within the application, security logic varies based on the user’s role, e.g., regular users versus administrators. This paper describes ROLECAST, the first system capable of statically identifying security logic that mediates securitysensitive events (such as database writes) in Web applications,

I am excited by the challenge of making software significantly more reliable, scalable, and secure than it is today and thus helping achieve advances in areas such as science, education, health, and energy. I have focused on the problem of software bugs, which cause errors that cost billions of dollars annually and sometimes result in injury or death. These bugs are pervasive in modern software, which is only becoming more complex as developers add features, integrate components, and write concurrent software. State-of-the-art testing, static analysis, and modern language features eliminate some but not all bugs. In particular, thorough in-house testing cannot test all possible environments, configurations, and thread interleavings. Deployed software thus contains bugs that are hard to reproduce, find, and fix. Deployed systems need support for improving reliability in order to achieve highly robust software. My interests lie in solving these problems with programming languages and runtime systems. I focus on building analyses and systems that help developers and users make software more reliable and effective. I am particularly interested in approaches that are lightweight and flexible enough to run alongside deployed systems and that provide rigorous guarantees about accuracy and performance. My dissertation work introduces broadly applicable techniques that help developers find and fix bugs in deployed systems and help users by automatically tolerating the effects of errors. Two significant contributions are (1) efficient techniques that add context sensitivity to a broad set of analyses for reliability and security (first section below), and (2) an automatic approach for minimizing the effects of programmers’