Oscar Nierstrasz

Arash Ale Ebrahim, Mohammadreza Hazhirpasand, Oscar Nierstrasz et al.

We propose a tool, called FuzzingDriver, to generate dictionary tokens for coverage-based greybox fuzzers (CGF) from the codebase of any target program. FuzzingDriver does not add any overhead to the fuzzing job as it is run beforehand. We compared FuzzingDriver to Google dictionaries by fuzzing six open-source targets, and we found that FuzzingDriver consistently achieves higher code coverage in all tests. We also executed eight benchmarks on FuzzBench to demonstrate how utilizing FuzzingDriver's dictionaries can outperform six widely-used CGF fuzzers. In future work, investigating the impact of FuzzingDriver's dictionaries on improving bug coverage might prove important. Video demonstration: https://www.youtube.com/watch?v=Y8j_KvfRrI8

Arianna Blasi, Nataliia Stulova, Alessandra Gorla et al.

Code comments are the primary means to document implementation and facilitate program comprehension. Thus, their quality should be a primary concern to improve program maintenance. While much effort has been dedicated to detecting bad smells, such as clones in code, little work has focused on comments. In this paper we present our solution to detect clones in comments that developers should fix. RepliComment can automatically analyze Java projects and report instances of copy-and-paste errors in comments, and can point developers to which comments should be fixed. Moreover, it can report when clones are signs of poorly written comments. Developers should fix these instances too in order to improve the quality of the code documentation. Our evaluation of 10 well-known open source Java projects identified over 11K instances of comment clones, and over 1,300 of them are potentially critical. We improve on our own previous work, which could only find 36 issues in the same dataset. Our manual inspection of 412 issues reported by RepliComment reveals that it achieves a precision of 79% in reporting critical comment clones. The manual inspection of 200 additional comment clones that RepliComment filters out as being legitimate, could not evince any false negative.

Mohammadreza Hazhirpasand, Mohammad Ghafari, Oscar Nierstrasz

[Background] Previous research has shown that developers commonly misuse cryptography APIs. [Aim] We have conducted an exploratory study to find out how crypto APIs are used in open-source Java projects, what types of misuses exist, and why developers make such mistakes. [Method] We used a static analysis tool to analyze hundreds of open-source Java projects that rely on Java Cryptography Architecture, and manually inspected half of the analysis results to assess the tool results. We also contacted the maintainers of these projects by creating an issue on the GitHub repository of each project, and discussed the misuses with developers. [Results] We learned that 85% of Cryptography APIs are misused, however, not every misuse has severe consequences. Developer feedback showed that security caveats in the documentation of crypto APIs are rare, developers may overlook misuses that originate in third-party code, and the context where a Crypto API is used should be taken into account. [Conclusion] We conclude that using Crypto APIs is still problematic for developers but blindly blaming them for such misuses may lead to erroneous conclusions.

Mohammadreza Hazhirpasand, Mohammad Ghafari, Stefan Krüger et al.

Previous research has shown that crypto APIs are hard for developers to understand and difficult for them to use. They consequently rely on unvalidated boilerplate code from online resources where security vulnerabilities are common. We analyzed 2,324 open-source Java projects that rely on Java Cryptography Architecture (JCA) to understand how crypto APIs are used in practice, and what factors account for the performance of developers in using these APIs. We found that, in general, the experience of developers in using JCA does not correlate with their performance. In particular, none of the factors such as the number or frequency of committed lines of code, the number of JCA APIs developers use, or the number of projects they are involved in correlate with developer performance in this domain. We call for qualitative studies to shed light on the reasons underlying the success of developers who are expert in using cryptography. Also, detailed investigation at API level is necessary to further clarify a developer obstacles in this domain.

Haidar Osman, Mohammad Ghafari, Oscar Nierstrasz

Bug prediction is the process of training a machine learning model on software metrics and fault information to predict bugs in software entities. While feature selection is an important step in building a robust prediction model, there is insufficient evidence about its impact on predicting the number of bugs in software systems. We study the impact of both correlation-based feature selection (CFS) filter methods and wrapper feature selection methods on five widely-used prediction models and demonstrate how these models perform with or without feature selection to predict the number of bugs in five different open source Java software systems. Our results show that wrappers outperform the CFS filter; they improve prediction accuracy by up to 33% while eliminating more than half of the features. We also observe that though the same feature selection method chooses different feature subsets in different projects, this subset always contains a mix of source code and change metrics.

Pascal Gadient, Oscar Nierstrasz, Mohammad Ghafari

HTTP headers are commonly used to establish web communications, and some of them are relevant for security. However, we have only little information about the usage and support of security-relevant headers in mobile applications. We explored the adoption of such headers in mobile app communication by querying 9,714 distinct URLs that were used in 3,376 apps and collected each server's response information. We discovered that support for secure HTTP header fields is absent in all major HTTP clients, and it is barely provided with any server response. Based on these results, we discuss opportunities for improvement particularly to reduce the likelihood of data leaks and arbitrary code execution. We advocate more comprehensive use of existing HTTP headers and timely development of relevant web browser security features in HTTP client libraries.

Pascal Gadient, Pascal Gerig, Oscar Nierstrasz et al.

IT professionals have no simple tool to create phishing websites and raise the awareness of users. We developed a prototype that can dynamically mimic websites by using enriched screenshots, which requires no additional programming experience and is simple to set up. The generated websites are functional and remain up-to-date. We found that 98% of the hyperlinks in mimicked websites are functional with our tool, compared to 43% with the best competitor, and only two participants suspected phishing attempts at the time they were performing tasks with our prototype. This work intends to raise awareness for phishing attempts especially with local websites by providing an easy to use prototype to set up such phishing sites.

Mohammadreza Hazhirpasand, Oscar Nierstrasz, Mohammad Ghafari

Recent studies have shown that developers have difficulties in using cryptographic APIs, which often led to security flaws. We are interested to tackle this matter by looking into what types of problems exist in various crypto libraries. We manually studied 500 posts on Stack Overflow associated with 20 popular crypto libraries. We realized there are 10 themes in the discussions. Interestingly, there were only two questions related to attacks against cryptography. There were 63 discussions in which developers had interoperability issues when working with more than a crypto library. The majority of posts (i.e. 112) were about encryption/decryption problems and 111 were about installation/compilation issues of crypto libraries. Overall, we realize that the crypto libraries are frequently involved in more than five themes of discussions. We believe the current initial findings can help team leaders and experienced developers to correctly guide the team members in the domain of cryptography. Moreover, future research should investigate the similarity of problems at the API level among popular crypto libraries.

Pooja Rani, Suada Abukar, Nataliia Stulova et al.

Assessing code comment quality is known to be a difficult problem. A number of coding style guidelines have been created with the aim to encourage writing of informative, readable, and consistent comments. However, it is not clear from the research to date which specific aspects of comments the guidelines cover (e.g., syntax, content, structure). Furthermore, the extent to which developers follow these guidelines while writing code comments is unknown. We analyze various style guidelines in Java and Python and uncover that the majority of them address more the content aspect of the comments rather than syntax or formatting, but when considering the different types of information developers embed in comments and the concerns they raise on various online platforms about the commenting practices, existing comment conventions are not yet specified clearly enough, nor do they adequately cover important concerns. We also analyze commenting practices of developers in diverse projects to see the extent to which they follow the guidelines. Our results highlight the mismatch between developer commenting practices and style guidelines, and provide several focal points for the design and improvement of comment quality checking tools.

Pooja Rani, Mathias Birrer, Sebastiano Panichella et al.

Code comments are important for program comprehension, development, and maintenance tasks. Given the varying standards for code comments, and their unstructured or semi-structured nature, developers get easily confused (especially novice developers) about which convention(s) to follow, or what tools to use while writing code documentation. Thus, they post related questions on external online sources to seek better commenting practices. In this paper, we analyze code comment discussions on online sources such as Stack Overflow (SO) and Quora to shed some light on the questions developers ask about commenting practices. We apply Latent Dirichlet Allocation (LDA) to identify emerging topics concerning code comments. Then we manually analyze a statistically significant sample set of posts to derive a taxonomy that provides an overview of the developer questions about commenting practices. Our results highlight that on SO nearly 40% of the questions mention how to write or process comments in documentation tools and environments, and nearly 20% of the questions are about potential limitations and possibilities of documentation tools to add automatically and consistently more information in comments. On the other hand, on Quora, developer questions focus more on background information (35% of the questions) or asking opinions (16% of the questions) about code comments. We found that (i) not all aspects of comments are covered in coding style guidelines, e.g., how to add a specific type of information, (ii) developers need support in learning the syntax and format conventions to add various types of information in comments, and (iii) developers are interested in various automated strategies for comments such as detection of bad comments, or verify comment style automatically, but lack tool support to do that.

Mohammadreza Hazhirpasand, Oscar Nierstrasz, Mohammadhossein Shabani et al.

Prior research has shown that cryptography is hard to use for developers. We aim to understand what cryptography issues developers face in practice. We clustered 91954 cryptography-related questions on the Stack Overflow website, and manually analyzed a significant sample (i.e., 383) of the questions to comprehend the crypto challenges developers commonly face in this domain. We found that either developers have a distinct lack of knowledge in understanding the fundamental concepts, \eg OpenSSL, public-key cryptography or password hashing, or the usability of crypto libraries undermined developer performance to correctly realize a crypto scenario. This is alarming and indicates the need for dedicated research to improve the design of crypto APIs.

Pooja Rani, Sebastiano Panichella, Manuel Leuenberger et al.

Previous studies have characterized code comments in various programming languages to support better program comprehension activities and maintenance tasks. However, very few studies have focused on understanding developer practices to write comments. None of them has compared such developer practices to the standard comment guidelines to study the extent to which developers follow the guidelines. This paper reports the first empirical study investigating commenting practices in Pharo Smalltalk. First, we analyze class comment evolution over seven Pharo versions. Then, we investigate the information types embedded in class comments. Finally, we study the adherence of developer commenting practices to the official class comment template over Pharo versions. The results of this study show that there is a rapid increase in class comments in the initial three Pharo versions, while in subsequent versions developers added comments to both new and old classes, thus maintaining a similar code to comment ratio. We furthermore found three times as many information types in class comments as those suggested by the template. However, the information types suggested by the template tend to be present more often than other types of information. Additionally, we find that a substantial proportion of comments follow the writing style of the template in writing these information types, but they are written and formatted in a non-uniform way.This suggests the need to standardize the commenting guidelines for formatting the text, and to provide headers for the different information types to ensure a consistent style and to identify the information easily. Given the importance of high-quality code comments, we draw numerous implications for developers and researchers to improve the support for comment quality assessment tools.

Mohammadreza Hazhirpasand, Mohammad Ghafari, Oscar Nierstrasz

We studied the web permission API dialog box in popular mobile and desktop browsers, and found that it typically lacks measures to protect users from unwittingly granting web permission when clicking too fast. We developed a game that exploits this issue, and tricks users into granting webcam permission. We conducted three experiments, each with 40 different participants, on both desktop and mobile browsers. The results indicate that in the absence of a prevention mechanism, we achieve a considerably high success rate in tricking 95% and 72% of participants on mobile and desktop browsers, respectively. Interestingly, we also tricked 47% of participants on a desktop browser where a prevention mechanism exists.

Nitish Patkar, Mohammad Ghafari, Oscar Nierstrasz et al.

Factors such as app stores or platform choices heavily affect functional and non-functional mobile app requirements. We surveyed 45 companies and interviewed ten experts to explore how factors that impact mobile app requirements are understood by requirements engineers in the mobile app industry. We observed a lack of knowledge in several areas. For instance, we observed that all practitioners were aware of data privacy concerns, however, they did not know that certain third-party libraries, usage aggregators, or advertising libraries also occasionally leak sensitive user data. Similarly, certain functional requirements may not be implementable in the absence of a third-party library that is either banned from an app store for policy violations or lacks features, for instance, missing desired features in ARKit library for iOS made practitioners turn to Android. We conclude that requirements engineers should have adequate technical experience with mobile app development as well as sufficient knowledge in areas such as privacy, security and law, in order to make informed decisions during requirements elicitation.

Mohammadreza Hazhirpasand, Mohammad Ghafari, Oscar Nierstrasz

Research has shown that cryptographic APIs are hard to use. Consequently, developers resort to using code examples available in online information sources that are often not secure. We have developed a web platform, named CryptoExplorer, stocked with numerous real-world secure and insecure examples that developers can explore to learn how to use cryptographic APIs properly. This platform currently provides 3,263 secure uses, and 5,897 insecure uses of Java Cryptography Architecture mined from 2,324 Java projects on GitHub. A preliminary study shows that CryptoExplorer provides developers with secure crypto API use examples instantly, developers can save time compared to searching on the internet for such examples, and they learn to avoid using certain algorithms in APIs by studying misused API examples. We have a pipeline to regularly mine more projects, and, on request, we offer our dataset to researchers.

Leonel Merino, Ekaterina Kozlova, Oscar Nierstrasz et al.

Although many tools have been presented in the research literature of software visualization, there is little evidence of their adoption. To choose a suitable visualization tool, practitioners need to analyze various characteristics of tools such as their supported software concerns and level of maturity. Indeed, some tools can be prototypes for which the lifespan is expected to be short, whereas others can be fairly mature products that are maintained for a longer time. Although such characteristics are often described in papers, we conjecture that practitioners willing to adopt software visualizations require additional support to discover suitable visualization tools. In this paper, we elaborate on our efforts to provide such support. To this end, we systematically analyzed research papers in the literature of software visualization and curated a catalog of 70 available tools that employ various visualization techniques to support the analysis of multiple software concerns. We further encapsulate these characteristics in an ontology. VISON, our software visualization ontology, captures these semantics as concepts and relationships. We report on early results of usage scenarios that demonstrate how the ontology can support (i) developers to find suitable tools for particular development concerns, and (ii) researchers who propose new software visualization tools to identify a baseline tool for a controlled experiment.

Mohammad Ghafari, Markus Eggiman, Oscar Nierstrasz

The pivotal role of testing in high-quality software production has driven a significant effort in evaluating and assessing testing practices. We explore the state of testing in a large industrial project over an extended period. We study the interplay between bugs in the project and its test cases, and interview developers and stakeholders to uncover reasons underpinning our observations. We realized that testing is not well adopted, and that testability (ie, ease of testing) is low. We found that developers tended to abandon writing tests when they assessed the effort to be high. Frequent changes in requirements and pressure to add new features also hindered developers from writing tests. Regardless of the debates on test first or later, we hypothesize that the underlying reasons for poor test quality are rooted in a lack of attention to testing early in the development of a software component, leading to poor testability of the component. However, testability is usually overlooked in research that studies the impact of testing practices, and should be explicitly taken into account.