Securing Internet Applications from Routing Attacks

Attacks on Internet routing are typically viewed through the lens of availability and confidentiality, assuming an adversary that either discards traffic or performs eavesdropping. Yet, a strategic adversary can use routing attacks to compromise the security of critical Internet applications like Tor, certificate authorities, and the bitcoin network. In this paper, we survey such application-specific routing attacks and argue that both application-layer and network-layer defenses are essential and urgently needed. While application-layer defenses are easier to deploy in the short term, we hope that our work serves to provide much needed momentum for the deployment of network-layer defenses

Key-Based Cookie-Less Session Management Framework for Application Layer Security

The goal of this study is to extend the guarantees provided by the secure transmission protocols such as Secure Sockets Layer (SSL) or Transport Layer Security (TLS) and apply them to the application layer. This paper proposes a comprehensive scheme that allows the unification of multiple security mechanisms, thereby removing the burden of authentication, mutual authentication, continuous authentication, and session management from the application development life-cycle. The proposed scheme will allow creation of high-level security mechanisms such as access control and group authentication on top of the extended security provisions. This scheme effectively eliminates the need for session cookies, session tokens and any similar technique currently in use. Hence reducing the attack surface and nullifying a vast group of attack vectors

CDNs' Dark Side: Identifying Security Problems in CDN-to-Origin Connections

Content Delivery Networks (CDNs) play a vital role in today's Internet ecosystem. To reduce the latency of loading a website's content, CDNs deploy edge servers in different geographic locations. CDN providers also offer important security features including protection against DoS attacks, Web Application Firewalls (WAF), and recently, issuing and managing certificates for their customers. Many popular websites use CDNs to benefit from both the security and performance advantages. For HTTPS websites, TLS security choices may differ in the connections between end-users and a CDN (front-end or user-to-CDN), and between the CDN and the origin server (back-end or CDN-to-Origin). Modern browsers can stop/warn users if weak or insecure TLS/HTTPS options are used in the front-end connections. However, such problems in the back-end connections are not visible to browsers or end-users, and lead to serious security issues. In this thesis, we primarily analyze TLS/HTTPS security issues in the back-end communication; such issues include inadequate certificate validation and support for vulnerable TLS configurations. We develop a test framework and investigate the back-end connection of 14 leading CDNs (including Cloudflare, Microsoft Azure, Amazon, and Fastly), where we could create an account. Surprisingly, for all the 14 CDNs, we found that the back-end TLS connections are vulnerable to security issues prevented/warned by modern browsers; examples include failing to validate the origin server's certificate, and using insecure cipher suites such as RC4, MD5, SHA-1, and even allowing plain HTTP connections to the origin. We also identified 168,795 websites in the Alexa top million that are potentially vulnerable to Man-in-the-Middle (MitM) a attacks in their back-end connections regardless of the origin/CDN configurations chosen by the origin owner

Security Implications of Insecure DNS Usage in the Internet

The Domain Name System (DNS) provides domain-to-address lookup-services used by almost all internet applications. Because of this ubiquitous use of the DNS, attacks against the DNS have become more and more critical. However, in the past, studies of DNS security have been mostly conducted against individual protocols and applications. In this thesis, we perform the first comprehensive evaluation of DNS-based attacks against a wide range of internet applications, ranging from time-synchronisation via NTP over internet resource management to security mechanisms. We show how to attack those applications by exploiting various weaknesses in the DNS. These attacks are based on both, already known weaknesses which are adapted to new attacks, as well as previously unknown attack vectors which have been found during the course of this thesis. We evaluate our attacks and provide the first taxonomy of DNS applications, to show how adversaries can systematically develop attacks exploiting the DNS. We analyze the attack surface created by our attacks in the internet and find that a significant number of applications and systems can be attacked. We work together with the developers of the vulnerable applications to develop patches and general countermeasures which can be applied by various parties to block our attacks. We also provide conceptual insights into the root causes allowing our attacks to help with the development of new applications and standards. The findings of this thesis are published in in 4 full-paper publications and 2 posters at international academic conferences. Additionally, we disclose our finding to developers which has lead to the registration of 8 Common Vulnerabilities and Exposures identifiers (CVE IDs) and patches in 10 software implementations. To raise awareness, we also presented our findings at several community meetings and via invited articles

Understanding the trust relationships of the web PKI

TLS and the applications it secures (e.g., email, online banking, social media) rely on the web PKI to provide authentication. Without strong authentication guarantees, a capable attacker can impersonate trusted network entities and undermine both data integrity and confidentiality. At its core, the web PKI succeeds as a global authentication system because of the scalability afforded by trust. Instead of requiring every network entity to directly authenticate every other network entity, network entities trust certification authorities (CAs) to perform authentication on their behalf. Prior work has extensively studied the TLS protocol and CA authentication of network entities (i.e., certificate issuance), but few have examined even the most foundational aspect of trust management and understood which CAs are trusted by which TLS user agents, and why. One major reason for this disparity is the opacity of trust management in two regards: difficult data access and poor specifications. It is relatively easy to acquire and test popular TLS client/server software and issued certificates. On the other hand, tracking trust policies/deployments and evaluating CA operations is less straightforward, but just as important for securing the web PKI. This dissertation is one of the first attempts to overcome trust management opacity. By observing new measurement perspectives and developing novel fingerprinting techniques, we discover the CAs that operate trust anchors, the default trust anchors that popular TLS user agents rely on, and a general class of injected trust anchors: TLS interceptors. This research not only facilitates new ecosystem visibility, it also provides an empirical grounding for trust management specification and evaluation. Furthermore, our findings point to many instances of questionable, and sometimes broken, security practices such as improperly identified CAs, inadvertent and overly permissive trust, and trivially exploitable injected trust. We argue that most of these issues stem from inadequate transparency, and that explicit mechanisms for linking trust anchors and root stores to their origins would help remedy these problems

Bamboozling Certificate Authorities with BGP

The Public Key Infrastructure (PKI) protects users from malicious man-in-the-middle attacks by having trusted Certificate Authorities (CAs) vouch for the domain names of servers on the Internet through digitally signed certificates. Ironically, the mechanism CAs use to issue certificates is itself vulnerable to man-in-the-middle attacks by network-level adversaries. Autonomous Systems (ASes) can exploit vulnerabilities in the Border Gateway Protocol (BGP) to hijack traffic destined to a victim's domain. In this paper, we rigorously analyze attacks that an adversary can use to obtain a bogus certificate. We perform the first real-world demonstration of BGP attacks to obtain bogus certificates from top CAs in an ethical manner. To assess the vulnerability of the PKI, we collect a dataset of 1.8 million certificates and find that an adversary would be capable of gaining a bogus certificate for the vast majority of domains. Finally, we propose and evaluate two countermeasures to secure the PKI: 1) CAs verifying domains from multiple vantage points to make it harder to launch a successful attack, and 2) a BGP monitoring system for CAs to detect suspicious BGP routes and delay certificate issuance to give network operators time to react to BGP attacks