The prevalence of security flaws in multiparty online services (e.g., Single-sign-on, third-party payment, etc.) calls for rigorous engineering supported by formal program verification. However, the adoption of program verification faces several hurdles in the real world: how to formally specify logic properties given that protocol specifications are often informal and vague, how to precisely model the attacker and the runtime platform, how to deal with the unbounded set of all potential transactions. We introduce Certification of Symbolic Transaction (CST), an approach to significantly lower these hurdles. CST tries to verify a protocol-independent safety property jointly defined over all parties, thus avoids the burden of individually specifying every party's property for every protocol, CST invokes static verification at runtime, i.e., It symbolically verifies every transaction on-the-fly, and thus (1) avoids the burden of modeling the attacker and the runtime platform, (2) reduces the proof obligation from considering all possible transactions to considering only the one at hand. We have applied CST on five commercially deployed applications, and show that, with only tens (or 100+) of lines of code changes per party, the original implementations are enhanced to achieve the objective of CST. Our security analysis shows that 12 out of 14 logic flaws reported in the literature will be prevented by CST. We also stress-tested CST by building a gambling system integrating four different services, for which there is no existing protocol to follow. Because transactions are symbolic and cacheable, CST has near-zero amortized runtime overhead. We make the source code of these implementations public, which are ready to be deployed for real-world uses.

OAuth has become a highly influential protocol due to its swift and wide adoption in the industry. The initial objective of the protocol was specific: it serves the authorization needs for websites. What motivates our work is the realization that the protocol has been significantly re-purposed and re-targeted over the years: (1) all major identity providers, e.g., Facebook, Google and Microsoft, have re-purposed OAuth for user authentication; (2) developers have re-targeted OAuth to the mobile platforms, in addition to the traditional web platform. Therefore, we believe that it is necessary and timely to conduct an in-depth study to demystify OAuth for mobile application developers. Our work consists of two pillars: (1) an in-house study of the OAuth protocol documentation that aims to identify what might be ambiguous or unspecified for mobile developers; (2) a field-study of over 600 popular mobile applications that highlights how well developers fulfill the authentication and authorization goals in practice. The result is really worrisome: among the 149 applications that use OAuth, 89 of them (59.7%) were incorrectly implemented and thus vulnerable. In the paper, we pinpoint the key portions in each OAuth protocol flow that are security critical, but are confusing or unspecified for mobile application developers. We then show several representative cases to concretely explain how real implementations fell into these pitfalls. Our findings have been communicated to vendors of the vulnerable applications. Most vendors positively confirmed the issues, and some have applied fixes. We summarize lessons learned from the study, hoping to provoke further thoughts about clear guidelines for OAuth usage in mobile applications.

Accurately determining locations of nodes in mobile wireless network is crucial for a myriad of applications. Unfortunately, most localization techniques are vulnerable to jamming attacks where the adversary attempts to disrupt communication between legitimate nodes in the network. In this paper, we propose an approach to localize a wireless node by using jamming attack as the advantage of the network. Our localization technique is divided into two steps. First, we discover the location of the jammer using power adaptation techniques. Then, we use these properties to extrapolate the locations of jammed nodes. We design a localization protocol using this technique, and demonstrate the feasibility of our mechanism by conducting indoor experiments based on IEEE 802.15.4 wireless nodes. Our result shows that for some situations our mechanism can be used to locate mobile nodes under jamming attack.

Many browser-based attacks can be prevented by using separate browsers for separate web sites. However, most users access the web with only one browser. We explain the security benefits that using multiple browsers provides in terms of two concepts: entry-point restriction and state isolation. We combine these concepts into a general app isolation mechanism that can provide the same security benefits in a single browser. While not appropriate for all types of web sites, many sites with high-value user data can opt in to app isolation to gain defenses against a wide variety of browser-based attacks. We implement app isolation in the Chromium browser and verify its security properties using finite-state model checking. We also measure the performance overhead of app isolation and conduct a large-scale study to evaluate its adoption complexity for various types of sites, demonstrating how the app isolation mechanisms are suitable for protecting a number of high-value Web applications, such as online banking.

History sniffing attacks allow web sites to learn about users' visits to other sites. The major browsers have recently adopted a defense against the current strategies for history sniffing. In a user study with 307 participants, we demonstrate that history sniffing remains feasible via interactive techniques which are not covered by the defense. While these techniques are slower and cannot hope to learn as much about users' browsing history, we see no practical way to defend against them.