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802.1x What it is, How it’s broken, and How to fix it.

802.1x What it is, How it’s broken, and How to fix it. Bruce Potter The Shmoo Group gdead@shmoo.com. Why Wireless?. No cable plant Lower cost (initially… TCO may be higher) Rapid deployment Enhanced mobility Ad hoc relationships Many different requirements. Why Not Wireless.

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802.1x What it is, How it’s broken, and How to fix it.

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  1. 802.1xWhat it is, How it’s broken, and How to fix it. Bruce Potter The Shmoo Group gdead@shmoo.com

  2. Why Wireless? • No cable plant • Lower cost (initially… TCO may be higher) • Rapid deployment • Enhanced mobility • Ad hoc relationships • Many different requirements

  3. Why Not Wireless • No physical security • Low throughput • Unregulated, noisy bands

  4. 802.11, 802.11b, etc. • IEEE standard – based on well known Ethernet standards • 802.11 – FHSS or DSSS, WEP, 2.4 GHz, Infrastructure (BSS) or Ad-Hoc (iBSS) • Limited to 2Mb/s due to FCC limits on dwell times per frequency hop • 802.11b – DSSS only, WEP, 2.4 GHz, Infrastructure or Ad-Hoc • Up to 11Mb/s • Also known as Wi-Fi • 802.11a and 802.11g

  5. An Association • Associations are a basic part of 802.11 • Client Requests authentication • AP responds with auth type (Open/WEP) • Authentication is performed • If successful, then Association is requested and granted • SSID is sent in the clear, so not advertising SSID is NOT a valid security mechanism

  6. General Principles • Deal with the basics • Integrity • Protecting your packets from modification by other parties • Confidentiality • Keeping eavesdroppers within range from gaining useful information • Keeping unauthorized users off the network • Free Internet! • Risks to both internal and external network • Availability • Low level DoS is hard to prevent • Like any other environment, there are no silver bullets

  7. Current Security Practices • WEP –Wired Equivalent Privacy • Link Level • Very Broken • Firewalls/MAC Filtering • Reactionary – IDS/Active Portal • Higher level protocols

  8. WEP In a Nutshell • 40 bits of security == 64 bits of marketing spam. • 104 bits of security == 128 bits of marketing spam

  9. Thoughts on WEP • Key management beyond a handful of people is impossible • Too much trust • Difficult administration • Key lifetime can get very short in an enterprise • No authentication for management frames • No per packet auth • False Advertising!!!

  10. What is Lacking? • Scalability • Many clients • Large networks • Protection for all parties • Eliminate invalid trust assumptions

  11. 802.1x • Port based authentication for all IEEE 802 networks (layer 2 authentication) • Originally for Campus networks • Extended for wireless • Allows for unified AAA services • Provides means for key transport

  12. Pre-Authentication State

  13. Post-Authentication State

  14. EAP • Extensible Authentication Protocol • Originally designed for PPP • Shoehorned into 802.1x • Switch/Access point is a pass through for EAP traffic. New authentication mechanisms do not require infrastructure upgrades • LEAP – Cisco’s Lightweight EAP • Password based and (relatively) widely available • De facto mechanism between AS and AServ is RADIUS

  15. EAP Methods • EAP-TLS: Uses certs! If implemented properly, solves many problems • TTLS – Tunneled TLS. Allows encapsulation of other auth mechanisms. • “machine” auth’d by TLS, person by the tunneled protocol • PEAP – IETF Draft • Like TTLS but with another EAP method encapsulated • TLS/TTLS and others require certs • We all have a PKI setup, right? and use it properly and regularly?

  16. What’s Right • Protection of the infrastructure • Authentication mechanism can • change as needed • address flaws in existing wireless security • Lightweight • No encapsulation, no per packet overhead… simply periodic authentication transactions

  17. What’s Right • In controlled environment, risks can be mitigated by higher level protocols • VPN/SSL/SSH • NOTE: exchange of WEP key material is not part of 802.1x specification • Remember: designed for wired campus networks

  18. What’s Right • Association happens BEFORE 802.1x transaction. • Good: If 802.1x session is protected by default WEP key then the attacker must first compromise the WEP key to make use of 802.1x vulns • Bad: Key management anyone? Just how does the default key get there?

  19. What’s Wrong • www.missl.cs.umd.edu/wireless/1x.pdf • First Open source supplicant • First holes in 802.1x • One way authentication • Less of a concern in LAN environment • Traffic Interception • Session Highjacking

  20. What’s Wrong – Technical • One way Authentication • Gateway authenticates the client • Client has no explicit means to authenticate the Gateway • Rouge gateways put client at risk • Remember – the loudest access point wins • Still no Authentication of management frames (assoc/deassoc/beacons/etc…)

  21. What’s Wrong - Technical • MITM • Send “Authentication Successful” to client • Client associates with malicious AP • Hijacking • Send deassociation message to client… AP is in the dark • Change MAC to client and have live connection

  22. What’s Wrong – Technical • RADIUS uses shared secret with the Authenticator • Same issue as WEP, but on a more reasonable scale • Authentication after association presents roaming problems • Authentication takes a non-trivial amount of time… can disrupt data in transit • Failure of RADIUS server == failure of network • Many AP implementations don’t allow multiple RADIUS servers • Most RADIUS server failover is non-transparent

  23. What’s Wrong – touchy feely • They forgot about the client (trust assumptions) • Everyone is ask risk • Everyone is a threat • Lack of physical security requires encrypted channel to secure 802.1x • Wired “port” is not the same as wireless “port” • Protocol designed to not require hardware replacement • Leads to less than stellar solution, esp WRT authentication of management frames.

  24. What’s Wrong – touchy feely • Extensibility leads to complexity • Complexity leads to mistakes in implementation • Read the MS Guide on create EAP methods as an example. • Multivendor support is difficult • Using a shoehorn to force protocols to work together leads to problems

  25. Why Did it Go Wrong? • 802.1x – Designed for Campus networks • EAP – Designed for PPP • NEITHER designed with wireless threat model in mind • Lesson: Don’t apply old protocols to new problems without understanding the risk.

  26. Where Are We Today? • Several 802.1x implementations available • Windows XP (not PocketPC 2002) • Open1x.org • EAP implementations • Windows IAS • FreeRADIUS – MD5 and TLS • Cisco • Other RADIUS servers

  27. Where Are We Today? • 802.1x capable Access Points • Cisco • Lucent • RG1000/RG1100 can be hacked with AP500 firmware to become 1x capable • Some drawbacks • OS authenticator from open1x.org • others

  28. What’s Next • Integration of existing solutions to “raise the bar” • Limited 802.1x implementations • 802.11i (Task Group I – Security) • On track… the right track • Mutual auth, per packet auth • 802.1x a part of

  29. What’s Next • WEP has the right idea • End to End Solutions ala SSL, SSH, IPSec • Not likely

  30. Temporal Key Integrity Protocol • Fast Packet Keying • Packet MAC • Dynamic Rekeying • Key distribution via 802.1x • 3Q product deployment • Still RC4 based to be backward compatible • AES with 802.1x keying in the distant future

  31. Questions http://www.shmoo.com/1x/

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