Biblio

Virtual switches are a crucial component of SDN-based cloud systems, enabling the interconnection of virtual machines in a flexible and "software-defined" manner. This paper raises the alarm on the security implications of virtual switches. In particular, we show that virtual switches not only increase the attack surface of the cloud, but virtual switch vulnerabilities can also lead to attacks of much higher impact compared to traditional switches. We present a systematic security analysis and identify four design decisions which introduce vulnerabilities. Our findings motivate us to revisit existing threat models for SDN-based cloud setups, and introduce a new attacker model for SDN-based cloud systems using virtual switches. We demonstrate the practical relevance of our analysis using a case study with Open vSwitch and OpenStack. Employing a fuzzing methodology, we find several exploitable vulnerabilities in Open vSwitch. Using just one vulnerability we were able to create a worm that can compromise hundreds of servers in a matter of minutes. Our findings are applicable beyond virtual switches: NFV and high-performance fast path implementations face similar issues. This paper also studies various mitigation techniques and discusses how to redesign virtual switches for their integration.

Enterprises continue to migrate their services to the cloud on a massive scale, but the increasing attack surface has become a natural target for malevolent actors. We show policy injection, a novel algorithmic complexity attack that enables a tenant to add specially tailored ACLs into the data center fabric to mount a denial-of-service attack through exploiting the built-in security mechanisms of the cloud management systems (CMS). Our insight is that certain ACLs, when fed with special covert packets by an attacker, may be very difficult to evaluate, leading to an exhaustion of cloud resources. We show how a tenant can inject seemingly harmless ACLs into the cloud data plane to abuse an algorithmic deficiency in the most popular cloud hypervisor switch, Open vSwitch, and reduce its effective peak performance by 80–90%, and, in certain cases, denying network access altogether.

Visible Light Communication (VLC) allows to reuse a lighting infrastructure for communication while its main purpose of illumination can be carried out at the same time. Light sources based on Light Emitting Diodes (LEDs) are attractive as they are inexpensive, ubiquitous, and allow rapid modulation. This paper describes how to integrate smartphones into such a communication system that supports networking for a wide range of devices, such as toys with single LEDs as transmitter and receivers as well as interconnected LED light bulbs. The main challenge is how to employ the smartphone without any (hardware) modification as a receiver, using the integrated camera as a (slow) light sampling device. This paper presents a simple software-based solution, exploiting the rolling shutter effect and slow motion video capturing capabilities of latest smartphones to enable continuous reception and real-time integration into an existing VLC system. Evaluation results demonstrate a working prototype and report communication distances up to 3m and a maximum data throughput of more than 1200b/s, improving upon previous work.

Software-Defined Networks (SDNs) promise to overcome the often complex and error-prone operation of tradi- tional computer networks, by enabling programmabil- ity, automation and verifiability. Yet, SDNs also in- troduce new challenges, for example due to the asyn- chronous communication channel between the logically centralized control platform and the switches in the data plane. In particular, the asynchronous commu- nication of network update commands (e.g., OpenFlow FlowMod messages) may lead to transient inconsisten- cies, such as loops or bypassed waypoints (e.g., fire- walls). One approach to ensure transient consistency even in asynchronous environments is to employ smart scheduling algorithms: algorithms which update subsets of switches in each communication round only, where each subset in itself guarantees consistency. In this demo, we show how to change routing policies in a transiently consistent manner. We demonstrate two al- gorithms, namely, Wayup [5] and Peacock [4], which partition the network updates sent from SDN controller towards OpenFlow software switches into multiple rounds as per respective algorithms. Later, the barrier mes- sages are utilized to ensure reliable network updates.