TLS on Android – Evolution over the last decade

Mobile Geräte und mobile Plattformen sind omnipräsent. Android hat sich zum bedeutendsten mobilen Betriebssystem entwickelt und bietet Milliarden Benutzer:innen eine Plattform mit Millionen von Apps. Diese bieten zunehmend Lösungen für alltägliche Probleme und sind aus dem Alltag nicht mehr wegzudenken. Mobile Apps arbeiten dazu mehr und mehr mit persönlichen sensiblen Daten, sodass ihr Datenverkehr ein attraktives Angriffsziel für Man-in-the-Middle-attacks (MitMAs) ist. Schutz gegen solche Angriffe bieten Protokolle wie Transport Layer Security (TLS) und Hypertext Transfer Protocol Secure (HTTPS), deren fehlerhafter Einsatz jedoch zu ebenso gravierenden Unsicherheiten führen kann. Zahlreiche Ereignisse und frühere Forschungsergebnisse haben diesbezüglich Schwachstellen in Android Apps gezeigt. Diese Arbeit präsentiert eine Reihe von Forschungsbeiträgen, die sich mit der Sicherheit von Android befassen. Der Hauptfokus liegt dabei auf der Netzwerksicherheit von Android Apps. Hierbei untersucht diese Arbeit verschiedene Möglichkeiten zur Verbesserung der Netzwerksicherheit und deren Erfolg, wobei sie die Situation in Android auch mit der generellen Evolution von Netzwerksicherheit in Kontext setzt. Darüber hinaus schließt diese Arbeit mit einer Erhebung der aktuellen Situation und zeigt Möglichkeiten zur weiteren Verbesserung auf.Smart devices and mobile platforms are omnipresent. Android OS has evolved to become the most dominating mobile operating system on the market with billions of devices and a platform with millions of apps. Apps increasingly offer solutions to everyday problems and have become an indispensable part of people’s daily life. Due to this, mobile apps carry and handle more and more personal and privacy-sensitive data which also involves communication with backend or third party services. Due to this, their network traffic is an attractive target for Man-in-the-Middle-attacks (MitMAs). Protection against such attacks is provided by protocols such as Transport Layer Security (TLS) and Hypertext Transfer Protocol Secure (HTTPS). Incorrect use of these, however, can impose similar vulnerabilities lead to equally serious security issues. Numerous incidents and research efforts have featured such vulnerabilities in Android apps in this regard. This thesis presents a line of research addressing security on Android with a main focus on the network security of Android apps. This work covers various approaches for improving network security on Android and investigates their efficacy as well as it puts findings in context with the general evolution of network security in a larger perspective. Finally, this work concludes with a survey of the current state of network security in Android apps and envisions directions for further improvement

To Pin or Not to Pin-Helping App Developers Bullet Proof Their TLS Connections To Pin or Not to Pin Helping App Developers Bullet Proof Their TLS Connections

Abstract For increased security during TLS certificate validation, a common recommendation is to use a variation of pinning. Especially non-browser software developers are encouraged to limit the number of trusted certificates to a minimum, since the default CA-based approach is known to be vulnerable to serious security threats. The decision for or against pinning is always a tradeoff between increasing security and keeping maintenance efforts at an acceptable level. In this paper, we present an extensive study on the applicability of pinning for non-browser software by analyzing 639,283 Android apps. Conservatively, we propose pinning as an appropriate strategy for 11,547 (1.8%) apps or for 45,247 TLS connections (4.25%) in our sample set. With a more optimistic classification of borderline cases, we propose pinning for consideration for 58,817 (9.1%) apps or for 140,020 (3.8% 1 ) TLS connections. This weakens the assumption that pinning is a widely usable strategy for TLS security in non-browser software. However, in a nominalactual comparison, we find that only 45 apps actually implement pinning. We collected developer feedback from 45 respondents and learned that only a quarter of them grasp the concept of pinning, but still find pinning too complex to use. Based on their feedback, we built an easy-to-use web-application that supports developers in the decision process and guides them through the correct deployment of a pinning-protected TLS implementation

Comparison of selected network communication methods on the Android platform

This paper is devoted to comparing three communication methods between mobile applications and servers. The analysis encompassed the results of six tests conducted using HTTP and HTTPS protocols, and server-socket technology. All sending times of data with various sizes between the client application and the server, and the impact of this operation on the processor load and battery use, were evaluated. The experiments consisted of sending and receiving a form, sending and receiving a large photo, and ensuring continuous communication to assess device use. To perform the analyses, an Android application was created to support the researched technology, while the server side was composed of programs written in Java, running on a Tomcat server. The conducted research made it possible to establish the best solution, which is server-socket technology

To Pin or Not to Pin—Helping App Developers Bullet Proof Their TLS Connections

by Utkal Ranjan Mudali and Ragavan Kanagara

To Pin or Not to Pin—Helping App Developers Bullet Proof Their TLS Connections

For increased security during TLS certificate validation, a common recommendation is to use a variation of pinning. Especially non-browser software developers are encouraged to limit the number of trusted certificates to a minimum, since the default CA-based approach is known to be vulnerable to serious security threats. The decision for or against pinning is always a tradeoff between increasing security and keeping maintenance efforts at an acceptable level. In this paper, we present an extensive study on the applicability of pinning for non-browser software by analyzing 639,283 Android apps. Conservatively, we propose pinning as an appropriate strategy for 11,547 (1.8%) apps or for 45,247 TLS connections (4.25%) in our sample set. With a more optimistic classification of borderline cases, we propose pinning for consideration for 58,817 (9.1%) apps or for 140,020 (3.8%1) TLS connections. This weakens the assumption that pinning is a widely usable strategy for TLS security in non-browser software. However, in a nominalactual comparison, we find that only 45 apps actually implement pinning. We collected developer feedback from 45 respondents and learned that only a quarter of them grasp the concept of pinning, but still find pinning too complex to use. Based on their feedback, we built an easy-to-use web-application that supports developers in the decision process and guides them through the correct deployment of a pinning-protected TLS implementation

Automated analysis of security protocol implementations

Security protocols, or cryptographic protocols, are crucial to the functioning of today’s technology-dependant society. They are a fundamental innovation, without which much of our online activity, mobile communication and even transport signalling would not be possible. The reason for their importance is simple, communication over shared or publicly accessible networks is vulnerable to interception, manipulation, and impersonation. It is the role of security protocols to prevent this, allowing for safe and secure communication. Our reliance on these protocols for such critical tasks, means it is essential to engineer them with great care, just like we do with bridges or a safety-critical aircraft engine control system, for example. As with all types of engineering, there are two key elements to this process – design and implementation. In this thesis we produce techniques to analyse the latter. In particular, we develop automated tooling which helps to identify incorrect or vulnerable behaviour in the implementations of security protocols. The techniques we present follow a theme of trying to infer as much as we can about the protocol logic implemented in a system, with as little access to it’s inner workings as possible. In general, we do this through observations of protocol messages on the network, executing the system, but treating it as a black-box. Within this particular framework, we design two new techniques – one which identifies a specific vulnerability in TLS/SSL, and another, more general approach, which systematically extracts a protocol behaviour model from protocols like the WiFi security handshakes. We then argue that it his framework limits the potential of model extraction, and proceed to develop a solution to this problem by utilising grey-box insights. Our proposed approach, which we test on a variety of security protocols, represents a paradigm shift in the well established model learning field. Throughout this thesis, as well as presenting general results from testing the efficacy of our tools, we also present a number of vulnerabilities we discover in the process. This ranges from major banking apps vulnerable to Man-In-The-Middle attacks, to CVE assigned ciphersuite downgrades in popular WiFi routers