Shuai Hao, Yubao Zhang, and Haining Wang, University of Delaware; Angelos Stavrou, George Mason University
The success of Content Delivery Networks (CDNs) relies on the mapping system that leverages dynamically generated DNS records to distribute client’s request to a proximal server for achieving optimal content delivery. However, the mapping system is vulnerable to malicious hijacks, as (1) it is very difficult to provide pre-computed DNSSEC signatures for dynamically generated records and (2) even considering DNSSEC enabled, DNSSEC itself is vulnerable to replay attacks. By leveraging crafted but legitimate mapping between 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 DoS protection, while remaining undetectable by existing security practices. In this paper, we investigate the security implications of dynamic mapping that remain understudied in security and CDN community. 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.
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