End-Users Get Maneuvered: Empirical Analysis of Redirection Hijacking in Content Delivery Networks

The success of Content Delivery Networks (CDNs) relies on the mapping system that leverages dynamically generated DNS records to distribute client requests to a proximal server for achieving optimal content delivery. However, the mapping system is vulnerable to malicious hijacks, as (1) it is difficult to provide precomputed DNSSEC signatures for dynamically generated records, and (2) even considering when DNSSEC is enabled, DNSSEC itself is vulnerable to replay attacks. By leveraging crafted but legitimate mapping between the end-user and edge server, adversaries can hijack CDN's request redirection and nullify the benefits offered by CDNs, such as proximal access, load balancing, and Denial-of-Service (DoS) protection, while remaining undetectable by existing security practices including DNSSEC. In this paper, we investigate the security implications of dynamic mapping that remain understudied in security and CDN communities. We perform a characterization of CDN's service delivery and assess this fundamental vulnerability in DNS-based CDNs in the wild. We demonstrate that DNSSEC is ineffective to address this problem, even with the newly adopted ECDSA that is capable of achieving live signing. We then discuss practical countermeasures against such manipulation.