Viktoria Felmetsger

Saner: Composing Static and Dynamic Analysis to Validate Sanitization in Web Applications

Web applications are ubiquitous, perform mission- critical tasks, and handle sensitive user data. Unfortunately, web applications are often implemented by developers with limited security skills, and, as a result, they contain vulnerabilities. Most of these vulnerabilities stem from the lack of input validation. That is, web applications use malicious input as part of a sensitive operation, without having properly checked or sanitized the input values prior to their use. Past research on vulnerability analysis has mostly focused on identifying cases in which a web application directly uses external input in critical operations. However, little research has been performed to analyze the correctness of the sanitization process. Thus, whenever a web application applies some sanitization routine to potentially malicious input, the vulnerability analysis assumes that the result is innocuous. Unfortunately, this might not be the case, as the sanitization process itself could be incorrect or incomplete. In this paper, we present a novel approach to the analysis of the sanitization process. More precisely, we combine static and dynamic analysis techniques to identify faulty sanitization procedures that can be bypassed by an attacker. We implemented our approach in a tool, called Saner, and we applied it to a number of real-world applications. Our results demonstrate that we were able to identify several novel vulnerabilities that stem from erroneous sanitization procedures.

Swaddler: an approach for the anomaly-based detection of state violations in web applications

In recent years, web applications have become tremendously popular, and nowadays they are routinely used in security-critical environments, such as medical, financial, and military systems. As the use of web applications for critical services has increased, the number and sophistication of attacks against these applications have grown as well. Most approaches to the detection of web-based attacks analyze the interaction of a web application with its clients and back-end servers. Even though these approaches can effectively detect and block a number of attacks, there are attacks that cannot be detected only by looking at the external behavior of a web application. In this paper, we present Swaddler, a novel approach to the anomaly-based detection of attacks against web applications. Swaddler analyzes the internal state of a web application and learns the relationships between the applications critical execution points and the applications internal state. By doing this, Swaddler is able to identify attacks that attempt to bring an application in an inconsistent, anomalous state, such as violations of the intended workflow of a web application. We developed a prototype of our approach for the PHP language and we evaluated it with respect to several real-world applications.

Multi-module vulnerability analysis of web-based applications

In recent years, web applications have become tremendously popular, and nowadays they are routinely used in security-critical environments, such as medical, financial, and military systems. As the use of web applications for critical services has increased, the number and sophistication of attacks against these applications have grown as well. Current approaches to securing web applications focus either on detecting and blocking web-based attacks using application-level firewalls, or on using vulnerability analysis techniques to identify security problems before deployment. The vulnerability analysis of web applications is made difficult by a number of factors, such as the use of scripting languages, the structuring of the application logic into separate pages and code modules, and the interaction with back-end databases. So far, approaches to web application vulnerability analysis have focused on single application modules to identify insecure uses of information provided as input to the application. Unfortunately, these approaches are limited in scope, and, therefore, they cannot detect multi-step attacks that exploit the interaction among multiple modules of an application. We have developed a novel vulnerability analysis approach that characterizes both the extended state and the intended workflow of a web application. By doing this, our analysis approach is able to take into account inter-module relationships as well as the interaction of an applications modules with back-end databases. As a result, our vulnerability analysis technique is able to identify sophisticated multi-step attacks against the applications workflow that were not addressed by previous approaches. We implemented our technique in a prototype tool, called MiMoSA, and tested it on several applications, identifying both known and new vulnerabilities.

SNOOZE: toward a stateful network protocol fuzZEr

Fuzzing is a well-known black-box approach to the security testing of applications. Fuzzing has many advantages in terms of simplicity and effectiveness over more complex, expensive testing approaches. Unfortunately, current fuzzing tools suffer from a number of limitations, and, in particular, they provide little support for the fuzzing of stateful protocols. In this paper, we present SNOOZE, a tool for building flexible, security-oriented, network protocol fuzzers. SNOOZE implements a stateful fuzzing approach that can be used to effectively identify security flaws in network protocol implementations. SNOOZE allows a tester to describe the stateful operation of a protocol and the messages that need to be generated in each state. In addition, SNOOZE provides attack-specific fuzzing primitives that allow a tester to focus on specific vulnerability classes. We used an initial prototype of the SNOOZE tool to test programs that implement the SIP protocol, with promising results. SNOOZE supported the creation of sophisticated fuzzing scenarios that were able to expose real-world bugs in the programs analyzed.

Static Detection of Vulnerabilities in x86 Executables

Several approaches have been proposed to perform vulnerability analysis of applications written in high-level languages. However, little has been done to automatically identify security-relevant flaws in binary code. In this paper, we present a novel approach to the identification of vulnerabilities in x86 executables in ELF binary format. Our approach is based on static analysis and symbolic execution techniques. We implemented our approach in a proof-of-concept tool and used it to detect taint-style vulnerabilities in binary code. The results of our evaluation show that our approach is both practical and effective

An Experience in Testing the Security of Real-World Electronic Voting Systems

Voting is the process through which a democratic society determines its government. Therefore, voting systems are as important as other well-known critical systems, such as air traffic control systems or nuclear plant monitors. Unfortunately, voting systems have a history of failures that seems to indicate that their quality is not up to the task. Because of the alarming frequency and impact of the malfunctions of voting systems, in recent years a number of vulnerability analysis exercises have been carried out against voting systems to determine if they can be compromised in order to control the results of an election. We have participated in two such large-scale projects, sponsored by the Secretaries of State of California and Ohio, whose goals were to perform the security testing of the electronic voting systems used in their respective states. As the result of the testing process, we identified major vulnerabilities in all of the systems analyzed. We then took advantage of a combination of these vulnerabilities to generate a series of attacks that would spread across the voting systems and would “steal” votes by combining voting record tampering with social engineering approaches. As a response to the two large-scale security evaluations, the Secretaries of State of California and Ohio recommended changes to improve the security of the voting process. In this paper, we describe the methodology that we used in testing the two real-world electronic voting systems we evaluated, the findings of our analysis, our attacks, and the lessons we learned.

Vulnerability Analysis of Web-based Applications

In the last few years, the popularity of web-based applications has grown tremendously. A number of factors have led an increasing number of organizations and individuals to rely on web-based applications to provide access to a variety of services. Today, web-based applications are routinely used in security-critical environments, such as medical, financial, and military systems.

Exploiting OS-level mechanisms to implement mobile code security

Mobile code systems provide an infrastructure that supports autonomous mobile components, called mobile agents. The infrastructure implements services for the transfer, execution, and protection of mobile agents. Security services are usually provided by implementing new security mechanisms that are explicitly tailored to mobile components. Unfortunately, developing sound, reliable security mechanisms is a non-trivial task, and a history of vulnerable and/or incomplete implementations of these mechanisms led to the idea that mobile code systems are inherently insecure, too complex, and very difficult to deploy. To overcome these problems, we developed a mobile code system that relies as much as possible on the security mechanisms already provided by the underlying operating system. By doing this, it is possible to develop, with reduced effort, security services that rely on well-known, well-understood, and well-tested security mechanisms. Also, by describing the security of the mobile code system in terms of the OS security mechanisms, system administrators can better evaluate the security implications of deploying the system. This paper describes the design and implementation of our system and compares its performance to several existing mobile code systems.