Securing Wireless LAN using Cisco-based technology

1. Securing Wireless LAN using Cisco-based technology Campus Crew Study Group Paul Matijevic Ed McCulloch Peter Mozdzierz Greg Schrader June 2007

2. Outline • Scenario • Solution • Solution Rationale • Concerns

3. Scenario • Deploy a wireless LAN infrastructure • Provide coverage for the following areas of a manufacturing environment: • Office • Shop floor • Security goals: • protect data confidentiality and integrity • authenticate and authorize each user • provide scalability and central manageability

4. Solution • Hardware purchased: • 8 Cisco 1200 Access Points (enterprise grade) • Assigned different channels to minimize interference • Assigning use of only channels 1, 6, and 11 minimizes interference by maximizing distance between carrier frequencies • Cisco 802.11 b/g computer hardware • PCI adapters and PCMCIA cards

5. Solution • 14 overlapping (staggered) channels (11 in the U.S.) • Center frequencies are separated by 5 MHz 2007 MITP 413 Wireless Technology - Michael L. Honig

6. Solution • Security considerations: • Encryption Algorithm mechanism • Message Integrity mechanism • Authentication Framework mechanism • Authentication Algorithm mechanism

7. Wi-Fi Protected Access (WPA) • Flaws in WEP (Wired Equivalent Privacy) known since January 2001 - flaws include weak encryption (keys no longer than 40 bits), static encryption keys, lack of key distribution method. • In April 2003, the Wi-Fi Alliance introduced an interoperable security protocol known as WiFi Protected Access (WPA), based on draft 3 of the IEEE 802.11i amendment. • WPA was designed to be a replacement for WEP networks without requiring hardware replacements, using a subset IEEE 802.11i amendment. • WPA provides stronger data encryption (weak in WEP) and user authentication (largely missing in WEP).

8. WPA Security Enhancements • WPA includes Temporal Key Integrity Protocol (TKIP) and 802.1x mechanisms. • The combination of these two mechanisms provides dynamic key encryption and mutual authentication • TKIP adds the following strengths to WEP: • 48-bit initialization vectors, use one-way hash function instead of XOR • Per-packet key construction and distribution: WPA automatically generates a new unique encryption key periodically for each client. In fact, WPA uses a unique key for each 802.11 frame. This avoids the same key staying in use for weeks or months as they do with WEP • Message integrity code: guard against forgery attacks.

9. Solution

10. Message Integrity Solution • Using TKIP-MIC (message integrity check) • MIC ensures data frames have not been tampered with and authenticity of source addresses • Also prevents WEP reuse • 8 byte field placed between data portion of 802.11 frame and 4 byte ICV (integrity Check Value) protecting both payload and header

11. WPA2 • In July 2004, the IEEE approved the full IEEE 802.11i specification, which was quickly followed by a new interoperability testing certification from the WiFi Alliance known as WPA2. • Strong encryption and authentication for infrastructure and ad-hoc networks (WPA1 is limited to infrastructure networks) • Support for the CCMP (Counter Mode with Cipher Block Chaining Message Authentication Code Protocol) encryption mechanism based on the AES as an alternative to the TKIP protocol • AES is the equivalent of the RC4 algorithm used by WPA. • CCMP is the equivalent of TKIP in WPA. Changing even one bit in a message produces a totally different result. CCMP utilizes 128-bit keys, with a 48-bit initialization vector (IV) for replay detection

12. WPA2 • TKIP was designed as an interim solution for wireless security, with the goal of providing sufficient security for 5 years while organizations transitioned to the full IEEE 802.11i security mechanism. • As of March 2006, the WPA2 certification became mandatory for all new equipment certified by the Wi-Fi Alliance, ensuring that any reasonably modern hardware will support both WPA1 and WPA2.

13. Authentication Solution • Facilitates authentication messages sent between AP’s and clients • 802.1x authentication used • Protocol resides at layer 2 - supports EAP (extensible authentication protocol) • Provides centralized policy control with timeout triggers • AP’s blocked until authentication process complete • RADIUS (Remote Access Dial-In User Service) server used • Low deployment complexity

14. Authentication Solution

15. Authentication Solution • Authentication Algorithm • Validates each users network access credentials • RADIUS server stores strong passwords • 25 alphanumeric characters • Non-dictionary phrases • Passwords encrypted and stored in users wireless profiles • Cisco’s LEAP (lightweight extensible authentication protocol) used • Allows for clients to re-authenticate frequently

16. Solution

17. Solution • Additional security • MAC address authentication • Valid addresses authenticated against list in RADIUS server • AP’s also possess a copy of users, passwords and valid MAC addresses • MAC and IP address spoofing is very difficult with 802.11X implementations

18. Concerns • LEAP allows clients to acquire a new WEP key that does not expire - could be hacked • Considered minimal risk in this case • Employees installing their own WLAN devices • AP’s configured to collect rogue SSID info • DoS attacks could occur against AP’s • Alarms configured to observe flooding behavior • Logs track details of usage and are reviewed regularly • Telnet disabled in favor of SSH

19. Concerns • Wireless IDS is not installed • WIDS understands data level patterns / signatures (like wired IDS) and also RF signatures of attacks • Current hardware does not include IDS • At the time of purchase, software IDS was not an option • Newer versions of Cisco AP’s include IDS capability • AP’s are upgradeable (as of 2005) • Firmware upgrade would install software wireless IDS

20. Questions? Other than Ron…

21. Other EAP • EAP-MD5 • LEAP (Lightweight EAP) • CISCO authentication that provides mutual authentication and dynamic WEP key generation • EAP-TLS (Transport Layer Security) • offers full authentication consistent with PKI public/private keys, PKI and digital certificates • Needs client certificate in order to authenticate client • Users login from different computers in coffee shops • Users are more familiar with the idea of passwords. Certificates may require some training.

22. Other EAPs • EAP-PEAP and EAP-TTLS • Uses Transport Level Security (TLS) to create an encrypted channel between an authenticating PEAP client, such as a wireless computer, and a PEAP authenticator • Establish a strongly encrypted "outer" TLS tunnel in stage one and then exchange authentication credentials (inner EAP) through an "inner" method in stage two. • Plus, as a result of authentication, session keys are distributed to enable data privacy between client and access point. 

23. Solution

24. Solution Rationale • WEP encryption and static-WEP key vulnerabilities are patched with 802.11X protocols • Authentication vulnerabilities minimized by use of strong, non-dictionary passwords • Cisco TKIP protocol preferred over WPA (Wi-Fi Protected Access) • TKIP session key rotation is dynamic • Changes every 4 hours and 40 minutes