Invalid certificates in modern browsers: A socio-technical analysis

Abstract

The authentication of a web server is a crucial procedure in the security of web browsing. It relies on certificate validation, a process that may require the participation of the user. Thus, the security of certificate validation is socio-technical as it depends on traditional security technology as well as on social elements such as cultural values, trust and human-computer interaction.This manuscript analyzes extensively the socio-technical security of certificate validation as carried out through today's most popular browsers. First, we model processes, protocols and ceremonies that browsers run with servers and users as UML activity diagrams. We consider both classic and private browsing modes and focus on the certificate validation. We then translate each UML activity diagram to a CSP# model. The model is expanded with the LTL formalization of five socio-technical properties pivoted on user involvement with certificate validation. We automatically check whether the CSP# models are socio-technically secure against Man-in-the-Middle attacks using the PAT model checker. The findings turn out to be far from straightforward. From them, we state best-practice recommendations to browser vendors. 3 validation. The mix of new browsers, modes, and properties increases the 16 scenarios analyzed in the previous paper to this manuscript's 60 scenarios. A disclaimer is in order that the proposed list of properties is not meant to be complete; however, our browser models are fairly well detailed, for example by allowing for the reception of a newly issued certificate to replace the older, expired one.The intellectual value that this manuscript gains is at least twofold: (i) it makes three best-practice recommendations to browsers upon the basis of the additional findings on the new set of browsers and modes; (ii) it finds two bugs in Safari, respectively one in Safari for OS X and one in Safari for iOS, which (we reported to Apple getting a reply that a fix would be available in the upcoming versions of the browser, and) are now filed with the vulnerability identifier CVE-2015-5859 [6,56]. It is also worth noting that, after our conference paper observed that Opera Mini fails to prompt the user in case of invalid certificate [12], a new version of the browser fixed this issue.Socio-technical analysis. Ellison coined the concept of a ceremony extending "the concept of network protocol by including human beings as nodes in the network" [25]; therefore, a ceremony is a technical system extended with its human users and the possible interactions between the system and its users . A ceremony extends the notion of protocol to include interactions, messages, and behaviours of the social components. Similarly, the term socio-technical system refers to the system including its social components [29]. Therefore, analyzing a ceremony means to conduct a socio-technical analysis focusing on socio-technical properties. It is somewhat understood that a socio-technical property pertains to how user choices affect a traditional property o...

Modelling human threats in security ceremonies1

“…Giustolisi et al take a UML and model checking approach to analyse TLS certificate validation as carried out by modern browsers. They focus on security properties that also depend on user interaction, but users do not deviate from the possible choices that each browser supports [26]. Martina et al [6] and more recently Martimiano and Martina [27] reinforce the need to shift away from the classical Dolev-Yao attacker model to capture human-centred threats.…”

Six Characters in Search of a Security Problem: Pirandellian Masks for Security Ceremonies

“…Bella et al argue that security measures should become invisible or beautiful/dictatorial to stimulate the user to participate more willingly [Bella 2020]. They bring to attention that a security analysis should account for other socio-technical facets of the task that the user is trying to accomplish as well, for example when surfing the Internet [Giustolisi et al 2018]. With all this in mind, we adhered to Bella and Coles-Kemp's approach for specifying and verifying security ceremonies, comprised of five layers, which can be folded or unfolded to focus on specific details one would like to assert [Bella and Coles-Kemp 2012].…”

Out to explore the cybersecurity planet

“…Example technical systems are protocols , such as the HTTP protocol, and notably protocols that also incorporate security measures, namely security protocols , such as the HTTPS security protocol. Correspondingly, example socio-technical systems are ceremonies , such as the HTTP ceremony, and notably ceremonies that also incorporate security measures, namely security ceremonies (Ellison, 2007), such as the HTTPS security ceremony (Giustolisi et al , 2018).…”