NDSS

When Match Fields Do Not Need to Match: Buffered Packets Hijacking in SDN

Jiahao Cao (Tsinghua University; George Mason University), Renjie Xie (Tsinghua University), Kun Sun (George Mason University), Qi Li (Tsinghua University), Guofei Gu (Texas A&M University), Mingwei Xu (Tsinghua University)

Software-Defined Networking (SDN) greatly meets the need in industry for programmable, agile, and dynamic networks by deploying diversified SDN applications on a centralized controller. However, SDN application ecosystem inevitably introduces new security threats since compromised or malicious applications can significantly disrupt network operations. A number of effective security enhancement systems have been developed to defend against potential attacks from SDN applications, including data provenance systems to protect applications from being poisoned by malicious applications, rule conflict detection systems to prevent data packets from bypassing network security policies, and application isolation systems to prevent applications from corrupting controllers. In this paper, we identify a new design flaw on flow rule installation in SDN, and this vulnerability can be exploited by malicious applications to launch effective attacks bypassing existing defense systems. We discover that SDN systems do not check the inconsistency between the buffer ID and match fields when an application attempts to install flow rules, so that a malicious application can manipulate the buffer ID to hijack buffered packets even though the installed flow rule from the application does not match the packet with that buffer ID. We name this new vulnerability as *buffered packet hijacking*, which can be exploited to launch attacks that disrupt all three SDN layers, namely, application layer, data plane layer, and control layer. First, by modifying buffered packets and resending them to controllers, a malicious application can poison other applications. Second, by manipulating forwarding behaviors of buffered packets, a malicious application can not only disrupt TCP connections of flows but also make flows bypass network security policies. Third, by copying massive buffered packets to controllers, a malicious application can saturate the bandwidth of the SDN control channel and computing resources. We demonstrate the feasibility and effectiveness of these attacks with both theoretical analysis and experiments in a real SDN testbed. Finally, we develop a lightweight defense system that can be readily deployed in existing SDN controllers as a patch.