IEEE 802.11W and Cisco MFP I

IEEE 802.11 is a suite of standards which govern WiFi protocols. In the original draft of IEEE 802.11, only WEP security mechanism was mentioned. WEP was inherently flawed with many problems like bad key management, no good integrity and replay check, weak encryption, small IV space and so on. The 11i amendment was a major security ammendmant to the standard which used WPA-2 AES mechanisms for robust security. But 802.11i was applicable to data packets only and management and control packets were still clear text.

With the inception of 802.11h, 802.11k, 802.11e etc. lot of sensitive information like fast handoffs, network resource management, block acks etc flows over management frames esp. action management frames. The denial of service attacks like De-Authentication and Dis-Association attacks are also based on management frames, which even more increased the need of providing some security to management frames. The IEEE 802.11w is a standard for providing security to management frames.

The IEEE 802.11w TG has several challenges to overcome, however. To protect the confidentiality of management traffic, IEEE 802.11w assumes that the client and the access point have exchanged dynamic key content. This precludes the protection of any management frames prior to the delivery of key content, thus exposing network name (SSID) information and other capability information needed for clients to connect to the network. Maintaining backward compatibility for non-IEEE 802.11w-compliant wireless devices will also be challenging for organisations, limiting the protection afforded by 802.11w until all hardware has been upgraded to support the required functionality.

Cisco has come up with its proprietary pre-standard solution called Management Frame Protection (MFP) which is supported in WLC-4.1 and higher. This video tutorial first describes the need for new standard and then briefs about the way new information element is added in the packets. The part 2 of this video tutorial will concentrate on the exact implementation of the standard along with introduction to Cisco-MFP protocol.

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Proper functioning of Enterprise and operator-deployed 802.11 APs and STAs requires that the management frames are transmitted with certain security properties. For instance, guarantees of source authentication, which ensures that the receiver can detect forgery attacks; confidentiality, which prevents eavesdropping attacks; and integrity protection, which prevents against in-flight modification of messages, are very important. Without these assurances, multiple attacks can be launched against the IEEE 802.11 WLANs, for instance:

• Forged Disconnects: An attacker can disconnect authorized users from the WLANs by sending forged disassociate messages.
• MAC State Machine Corruption: Management frames enable transitions of the internal state machines in the 802.11 WLAN APs and STAs. Incorrect sequence or forged management messages can cause WLAN devices to lock up or enter inconsistent state.
• Unauthorized Service Corruption: Attackers can forge messages to prevent authorized users from gaining access to a network service; for instance, a certain QoS for its voice application.

Related links

• Cisco MFP Configuration on Cisco-WLC

Amit Vartak, 27 is working in wired and wireless security fields since last 3-4 years. His current area of interest includes IEEE 802.11 (Wi-Fi) suite of protocols, vulnerabilities in these protocols and countermeasure for those vulnerabilities. Working on cutting edge tools and technology always keeps him busy. He has contributed from concept level to final prototyping for the presentations in Defcon 2007 (The Emperor Has No Cloak - WEP Cloaking Exposed) and Toorcon 2007 (Caffe latte attack). He holds 2 patents with USPTO (current status: Patent Pending) and a few papers in IEEE journals on wireless protocol vulnerabilities. Prior to this, he was working on MEMS (Micro Electro Mechanical Systems) and has published a few papers in SPIE and ICMAT. (Yeah… kindda orthogonal fields… but technology really doesn’t limit the talent :) He did his masters in Electrical Engineering from one of the premier institutes in India, Indian Institute of Technology, Bombay (IIT-Bombay) and his under graduation, from University of Mumbai in Electronics and Telecommunication Engineering. He is currently working with AirTight Networks Inc. as a team lead in technology group since last 3 years.You can get in touch with him at amitcv[at]gmail[dot]com