Bruno Crispo

Seyed Ali Mirheidari, Sajjad Arshad, Kaan Onarlioglu et al.

Web cache deception (WCD) is an attack proposed in 2017, where an attacker tricks a caching proxy into erroneously storing private information transmitted over the Internet and subsequently gains unauthorized access to that cached data. Due to the widespread use of web caches and, in particular, the use of massive networks of caching proxies deployed by content distribution network (CDN) providers as a critical component of the Internet, WCD puts a substantial population of Internet users at risk. We present the first large-scale study that quantifies the prevalence of WCD in 340 high-profile sites among the Alexa Top 5K. Our analysis reveals WCD vulnerabilities that leak private user data as well as secret authentication and authorization tokens that can be leveraged by an attacker to mount damaging web application attacks. Furthermore, we explore WCD in a scientific framework as an instance of the path confusion class of attacks, and demonstrate that variations on the path confusion technique used make it possible to exploit sites that are otherwise not impacted by the original attack. Our findings show that many popular sites remain vulnerable two years after the public disclosure of WCD. Our empirical experiments with popular CDN providers underline the fact that web caches are not plug & play technologies. In order to mitigate WCD, site operators must adopt a holistic view of their web infrastructure and carefully configure cache settings appropriate for their applications.

Mahmoud Ammar, Mahdi Washha, Gowri Sankar Ramachandran et al.

The Internet of Things (IoT) is increasingly intertwined with critical industrial processes, yet contemporary IoT devices offer limited security features, creating a large new attack surface. Remote attestation is a well-known technique to detect cyber threats by remotely verifying the internal state of a networked embedded device through a trusted entity. Multi-device attestation has received little attention although current single-device approaches show limited scalability in IoT applications. Though recent work has yielded some proposals for scalable attestation, several aspects remain unexplored, and thus more research is required. This paper presents slimIoT, a scalable lightweight attestation protocol that is suitable for all IoT devices. slimIoT depends on an efficient broadcast authentication scheme along with symmetric key cryptography. It is resilient against a strong adversary with physical access to the IoT device. Our protocol is informative in the sense that it identifies the precise status of every device in the network. We implement and evaluate slimIoT considering many factors. On the one hand, our evaluation results show a low overhead in terms of memory footprint and runtime. On the other hand, simulations demonstrate that slimIoT is scalable, robust and highly efficient to be used in static and dynamic networks consisting of thousands of heterogenous IoT devices.

Mahmoud Ammar, Mahdi Washha, Bruno Crispo

The growing pervasiveness of Internet of Things (IoT) expands the attack surface by connecting more and more attractive attack targets, i.e. embedded devices, to the Internet. One key component in securing these devices is software integrity checking, which typically attained with Remote Attestation (RA). RA is realized as an interactive protocol, whereby a trusted party, verifier, verifies the software integrity of a potentially compromised remote device, prover. In the vast majority of IoT applications, smart devices operate in swarms, thus triggering the need for efficient swarm attestation schemes. In this paper, we present WISE, the first intelligent swarm attestation protocol that aims to minimize the communication overhead while preserving an adequate level of security. WISE depends on a resource-efficient smart broadcast authentication scheme where devices are organized in fine-grained multi-clusters, and whenever needed, the most likely compromised devices are attested. The candidate devices are selected intelligently taking into account the attestation history and the diverse characteristics (and constraints) of each device in the swarm. We show that WISE is very suitable for resource-constrained embedded devices, highly efficient and scalable in heterogenous IoT networks, and offers an adjustable level of security.

Sajjad Arshad, Seyed Ali Mirheidari, Tobias Lauinger et al.

Relative Path Overwrite (RPO) is a recent technique to inject style directives into sites even when no style sink or markup injection vulnerability is present. It exploits differences in how browsers and web servers interpret relative paths (i.e., path confusion) to make a HTML page reference itself as a stylesheet; a simple text injection vulnerability along with browsers' leniency in parsing CSS resources results in an attacker's ability to inject style directives that will be interpreted by the browser. Even though style injection may appear less serious a threat than script injection, it has been shown that it enables a range of attacks, including secret exfiltration. In this paper, we present the first large-scale study of the Web to measure the prevalence and significance of style injection using RPO. Our work shows that around 9% of the sites in the Alexa Top 10,000 contain at least one vulnerable page, out of which more than one third can be exploited. We analyze in detail various impediments to successful exploitation, and make recommendations for remediation. In contrast to script injection, relatively simple countermeasures exist to mitigate style injection. However, there appears to be little awareness of this attack vector as evidenced by a range of popular Content Management Systems (CMSes) that we found to be exploitable.

Muhammad Rizwan Asghar, Mihaela Ion, Giovanni Russello et al.

Data outsourcing is a growing business model offering services to individuals and enterprises for processing and storing a huge amount of data. It is not only economical but also promises higher availability, scalability, and more effective quality of service than in-house solutions. Despite all its benefits, data outsourcing raises serious security concerns for preserving data confidentiality. There are solutions for preserving confidentiality of data while supporting search on the data stored in outsourced environments. However, such solutions do not support access policies to regulate access to a particular subset of the stored data. For complex user management, large enterprises employ Role-Based Access Controls (RBAC) models for making access decisions based on the role in which a user is active in. However, RBAC models cannot be deployed in outsourced environments as they rely on trusted infrastructure in order to regulate access to the data. The deployment of RBAC models may reveal private information about sensitive data they aim to protect. In this paper, we aim at filling this gap by proposing \textbf{$\mathit{ESPOON_{ERBAC}}$} for enforcing RBAC policies in outsourced environments. $\mathit{ESPOON_{ERBAC}}$ enforces RBAC policies in an encrypted manner where a curious service provider may learn a very limited information about RBAC policies. We have implemented $\mathit{ESPOON_{ERBAC}}$ and provided its performance evaluation showing a limited overhead, thus confirming viability of our approach.

Muhammad Rizwan Asghar, Mihaela Ion, Giovanni Russello et al.

The enforcement of security policies in outsourced environments is still an open challenge for policy-based systems. On the one hand, taking the appropriate security decision requires access to the policies. However, if such access is allowed in an untrusted environment then confidential information might be leaked by the policies. Current solutions are based on cryptographic operations that embed security policies with the security mechanism. Therefore, the enforcement of such policies is performed by allowing the authorised parties to access the appropriate keys. We believe that such solutions are far too rigid because they strictly intertwine authorisation policies with the enforcing mechanism. In this paper, we want to address the issue of enforcing security policies in an untrusted environment while protecting the policy confidentiality. Our solution ESPOON is aiming at providing a clear separation between security policies and the enforcement mechanism. However, the enforcement mechanism should learn as less as possible about both the policies and the requester attributes.