James Parker

Elizaveta Pertseva, Valentin Robert, Clark Barrett et al.

Efforts to verify Zero-Knowledge Proof circuit encodings have highlighted the challenge of proving the correctness of quantifier-free statements that make use of both bitvector and finite field operations. Existing verification workflows are either manual or rely on SMT solvers, which scale poorly on some classes of problems for reasons that include difficulties with conversion operators and challenges reasoning about inequalities. To address these limitations, we present a novel Lean tactic BitModEq that leverages range lemmas and case analysis to produce verified translations from finite fields to bitvectors. Our approach, combined with bit-blasting, outperforms state-of-the-art SMT solvers, solving 19% more ZKP arithmetization benchmarks.

Marc B. Rosen, James Parker, Alex J. Malozemoff

We introduce Balboa, a link obfuscation framework for censorship circumvention. Balboa provides a general framework for tunneling data through existing applications. Balboa sits between an application and the operating system, intercepting outgoing network traffic and rewriting it to embed data. To avoid introducing any distinguishable divergence from the expected application behavior, Balboa only rewrites traffic that matches an externally specified \emph{traffic model} pre-shared between the communicating parties. The traffic model captures some subset of the network traffic (e.g., some subset of music an audio streaming server streams). The sender uses this model to replace outgoing data with a pointer to the associated location in the model and embed data in the freed up space. The receiver then extracts the data, replacing the pointer with the original data from the model before passing the data on to the application. When using TLS, this approach means that application behavior with Balboa is \emph{equivalent}, modulo small (protocol-dependent) timing differences, to if the application was running without Balboa. Balboa differs from prior approaches in that it (1) provides a framework for tunneling data through arbitrary (TLS-protected) protocols/applications, and (2) runs the unaltered application binaries on standard inputs, as opposed to most prior tunneling approaches which run the application on non-standard -- and thus potentially distinguishable -- inputs. We present two instantiations of Balboa -- one for audio streaming and one for web browsing -- and demonstrate the difficulty of identifying Balboa by a machine learning classifier.

James Parker, Michael Hicks, Andrew Ruef et al.

Typical security contests focus on breaking or mitigating the impact of buggy systems. We present the Build-it, Break-it, Fix-it (BIBIFI) contest, which aims to assess the ability to securely build software, not just break it. In BIBIFI, teams build specified software with the goal of maximizing correctness, performance, and security. The latter is tested when teams attempt to break other teams' submissions. Winners are chosen from among the best builders and the best breakers. BIBIFI was designed to be open-ended; teams can use any language, tool, process, etc. that they like. As such, contest outcomes shed light on factors that correlate with successfully building secure software and breaking insecure software. We ran three contests involving a total of 156 teams and three different programming problems. Quantitative analysis from these contests found that the most efficient build-it submissions used C/C++, but submissions coded in a statically-type safe language were 11 times less likely to have a security flaw than C/C++ submissions. Break-it teams that were also successful build-it teams were significantly better at finding security bugs.

James Parker, Niki Vazou, Michael Hicks

This paper presents LWeb, a framework for enforcing label-based, information flow policies in database-using web applications. In a nutshell, LWeb marries the LIO Haskell IFC enforcement library with the Yesod web programming framework. The implementation has two parts. First, we extract the core of LIO into a monad transformer (LMonad) and then apply it to Yesod's core monad. Second, we extend Yesod's table definition DSL and query functionality to permit defining and enforcing label-based policies on tables and enforcing them during query processing. LWeb's policy language is expressive, permitting dynamic per-table and per-row policies. We formalize the essence of LWeb in the $λ_{LWeb}$ calculus and mechanize the proof of noninterference in Liquid Haskell. This mechanization constitutes the first metatheoretic proof carried out in Liquid Haskell. We also used LWeb to build a substantial web site hosting the Build it, Break it, Fix it security-oriented programming contest. The site involves 40 data tables and sophisticated policies. Compared to manually checking security policies, LWeb imposes a modest runtime overhead of between 2% to 21%. It reduces the trusted code base from the whole application to just 1% of the application code, and 21% of the code overall (when counting LWeb too).

Andrew Ruef, Michael Hicks, James Parker et al.

Typical security contests focus on breaking or mitigating the impact of buggy systems. We present the Build-it Break-it Fix-it BIBIFI contest which aims to assess the ability to securely build software not just break it. In BIBIFI teams build specified software with the goal of maximizing correctness performance and security. The latter is tested when teams attempt to break other teams submissions. Winners are chosen from among the best builders and the best breakers. BIBIFI was designed to be open-ended - teams can use any language tool process etc. that they like. As such contest outcomes shed light on factors that correlate with successfully building secure software and breaking insecure software. During we ran three contests involving a total of teams and two different programming problems. Quantitative analysis from these contests found that the most efficient build-it submissions used CC but submissions coded in a statically-typed language were less likely to have a security flaw build-it teams with diverse programming-language knowledge also produced more secure code. Shorter programs correlated with better scores. Break-it teams that were also build-it teams were significantly better at finding security bugs.