Detecting DOM based XSS vulnerabilities using debug API of the modern web-browser

Рассматривается решение задачи поиска уязвимостей класса DOM-based XSS через последовательную комбинацию методов динамического анализа и fuzz-тести-рования. Для создания поддерживаемого динамического анализатора JavaScript-кода используется современный веб-обозреватель Firefox без модификации его исходного кода. Приводится обзор существующих методов поиска уязвимостей класса DOM-based XSS

A Practical Blended Analysis for Dynamic Features in JavaScript

The JavaScript Blended Analysis Framework is designed to perform a general-purpose, practical combined static/dynamic analysis of JavaScript programs, while handling dynamic features such as run-time generated code and variadic func- tions. The idea of blended analysis is to focus static anal- ysis on a dynamic calling structure collected at runtime in a lightweight manner, and to rene the static analysis us- ing additional dynamic information. We perform blended points-to analysis of JavaScript with our framework and compare results with those computed by a pure static points- to analysis. Using JavaScript codes from actual webpages as benchmarks, we show that optimized blended analysis for JavaScript obtains good coverage (86.6% on average per website) of the pure static analysis solution and nds ad- ditional points-to pairs (7.0% on average per website) con- tributed by dynamically generated/loaded code

Generalizing Permissive-Upgrade in Dynamic Information Flow Analysis

Preventing implicit information flows by dynamic program analysis requires coarse approximations that result in false positives, because a dynamic monitor sees only the executed trace of the program. One widely deployed method is the no-sensitive-upgrade check, which terminates a program whenever a variable's taint is upgraded (made more sensitive) due to a control dependence on tainted data. Although sound, this method is restrictive, e.g., it terminates the program even if the upgraded variable is never used subsequently. To counter this, Austin and Flanagan introduced the permissive-upgrade check, which allows a variable upgrade due to control dependence, but marks the variable "partially-leaked". The program is stopped later if it tries to use the partially-leaked variable. Permissive-upgrade handles the dead-variable assignment problem and remains sound. However, Austin and Flanagan develop permissive-upgrade only for a two-point (low-high) security lattice and indicate a generalization to pointwise products of such lattices. In this paper, we develop a non-trivial and non-obvious generalization of permissive-upgrade to arbitrary lattices. The key difficulty lies in finding a suitable notion of partial leaks that is both sound and permissive and in developing a suitable definition of memory equivalence that allows an inductive proof of soundness

Automatic Root Cause Quantification for Missing Edges in JavaScript Call Graphs (Extended Version)

Building sound and precise static call graphs for real-world JavaScript applications poses an enormous challenge, due to many hard-to-analyze language features. Further, the relative importance of these features may vary depending on the call graph algorithm being used and the class of applications being analyzed. In this paper, we present a technique to automatically quantify the relative importance of different root causes of call graph unsoundness for a set of target applications. The technique works by identifying the dynamic function data flows relevant to each call edge missed by the static analysis, correctly handling cases with multiple root causes and inter-dependent calls. We apply our approach to perform a detailed study of the recall of a state-of-the-art call graph construction technique on a set of framework-based web applications. The study yielded a number of useful insights. We found that while dynamic property accesses were the most common root cause of missed edges across the benchmarks, other root causes varied in importance depending on the benchmark, potentially useful information for an analysis designer. Further, with our approach, we could quickly identify and fix a recall issue in the call graph builder we studied, and also quickly assess whether a recent analysis technique for Node.js-based applications would be helpful for browser-based code. All of our code and data is publicly available, and many components of our technique can be re-used to facilitate future studies.Comment: Extended version of ECOOP'22 paper (with appendix

Information Flow Control in WebKit's JavaScript Bytecode

Websites today routinely combine JavaScript from multiple sources, both trusted and untrusted. Hence, JavaScript security is of paramount importance. A specific interesting problem is information flow control (IFC) for JavaScript. In this paper, we develop, formalize and implement a dynamic IFC mechanism for the JavaScript engine of a production Web browser (specifically, Safari's WebKit engine). Our IFC mechanism works at the level of JavaScript bytecode and hence leverages years of industrial effort on optimizing both the source to bytecode compiler and the bytecode interpreter. We track both explicit and implicit flows and observe only moderate overhead. Working with bytecode results in new challenges including the extensive use of unstructured control flow in bytecode (which complicates lowering of program context taints), unstructured exceptions (which complicate the matter further) and the need to make IFC analysis permissive. We explain how we address these challenges, formally model the JavaScript bytecode semantics and our instrumentation, prove the standard property of termination-insensitive non-interference, and present experimental results on an optimized prototype

A Hybrid Approach for Proving Noninterference of Java Programs

Several tools and approaches for proving noninterference properties for Java and other languages exist. Some of them have a high degree of automation or are even fully automatic, but overapproximate the actual information flow, and hence, may produce false positives. Other tools, such as those based on theorem proving, are precise, but may need interaction, and hence, analysis is time-consuming. In this paper, we propose a hybrid approach that aims at obtaining the best of both approaches: We want to use fully automatic analysis as much as possible and only at places in a program where, due to overapproximation, the automatic approaches fail, we resort to more precise, but interactive analysis, where the latter involves only the verification of specific functional properties in certain parts of the program, rather than checking more intricate noninterference properties for the whole program. To illustrate the hybrid approach, in a case study we use the hybrid approach–along with the fully automatic tool Joana for checking noninterference properties for Java programs and the theorem prover KeY for the verification of Java programs–and the CVJ framework proposed by Küsters, Truderung, and Graf to establish cryptographic privacy properties for a non-trivial Java program, namely an e-voting system. The CVJ framework allows one to establish cryptographic indistinguishability properties for Java programs by checking (standard) noninterference properties for such programs

Detecting Redundant CSS Rules in HTML5 Applications: A Tree-Rewriting Approach

HTML5 applications normally have a large set of CSS (Cascading Style Sheets) rules for data display. Each CSS rule consists of a node selector (given in an XPath-like query language) and a declaration block (assigning values to selected nodes' display attributes). As web applications evolve, maintaining CSS files can easily become problematic. Some CSS rules will be replaced by new ones, but these obsolete (hence redundant) CSS rules often remain in the applications. Not only does this "bloat" the applications, but it also significantly increases web browsers' processing time. Most works on detecting redundant CSS rules in HTML5 applications do not consider the dynamic behaviors of HTML5 (specified in JavaScript); in fact, the only proposed method that takes these into account is dynamic analysis (a.k.a. testing), which cannot soundly prove redundancy of CSS rules. In this paper, we introduce an abstraction of HTML5 applications based on monotonic tree-rewriting and study its "redundancy problem". We establish the precise complexity of the problem and various subproblems of practical importance (ranging from P to EXP). In particular, our algorithm relies on an efficient reduction to an analysis of symbolic pushdown systems (for which highly optimised solvers are available), which yields a fast method for checking redundancy in practice. We implemented our algorithm and demonstrated its efficacy in detecting redundant CSS rules in HTML5 applications.Comment: 50 page