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Secure Wireless Communication: Validating Disassociate and Deauthenticate Messages

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Learn how to protect your network by validating and securing disassociate and deauthenticate messages in 802.11 state machine. Timely advice from Microsoft's Tim Moore.

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Secure Wireless Communication: Validating Disassociate and Deauthenticate Messages

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  1. Validating Disassociate and Deauthenticate messages Tim Moore Tim Moore, Microsoft

  2. 802.11 state machine Tim Moore, Microsoft

  3. Issues • Anyone can send a disassociate or deauthenticate and disconnect a STA • STA or AP can delete state (remove keys) asynchronously • Unauthenticated disassociate and deauth are needed when keys are not available • A STA which has keys should not accept unauthenticated disassociate or deauth messages Tim Moore, Microsoft

  4. New 802.11 state machine Tim Moore, Microsoft

  5. Authenticating disassociate/deauth • Two options • Integrity check of disassociate and deauthenticate messages • Only when keys are available • Don’t authenticate disassociate and deauth • Use another method such as AKMP • Either case 802.11 state machine needs to check if keys available before accepting disassociate or deauthenticate messages Tim Moore, Microsoft

  6. Integrity check • New format for messages, either • Optional when keys are not available • Add IE to messages containing an integrity check • Use TKIP/WRAP/CCMP and encryption/integrity check the messages Tim Moore, Microsoft

  7. AKMP • Start 4-way handshake on receiving disassociate or deauthenticate messages • Change Supplicant and Authenticator state machines to run 4-way handshake on receiving disassociate or deauthenticate • Authenticator • Move DeauthenticateRequest from DISCONNECTED state to PTKSTART state • Supplicant • Add new state DISCONNECT. Sends EAPOL-Key Request. Timeout on completing 4-way handshake. Timeout goes to DISCONNECTED state Tim Moore, Microsoft

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