1. July 2002
Threat Model
Tim Moore
Tim Moore, Microsoft

2. Looked at 802.11 1999 and then RSN to fix 1999 issues Not complete
July 2002
Focused on ESS
Looked at and then RSN to fix 1999 issues
Not complete
Tim Moore, Microsoft

3. 802.1X key management Station AP 802.11 MAC July 2002
Tim Moore, Microsoft

4. Threats Spoofing Tampering Repudiation Information Disclosure
July 2002
Threats
Spoofing
Tampering
Repudiation
Information Disclosure
Denial of Service
Elevation of Privilege
Tim Moore, Microsoft

5. Integrity and Privacy from RSN
July 2002
Data message
Spoofing
Information Disclosure
Tampering
WEP!
Integrity and Privacy from RSN
MAC address spoof detection requires Pairwise keys
Station bridging unicast traffic will be decrypted as a Group key
Should this be allowed? As it allows spoofing of MAC addresses
Tim Moore, Microsoft

6. July 2002
TKIP/AES
If the IV is repeated with a particular key then it is easy to recover the key
4-way handshake and 48bit IV
Tim Moore, Microsoft

7. Michael Counter measures make a DoS
July 2002
Michael
Counter measures make a DoS
Snoop packet
Destroy packet CRC
Flip a bit
Flip bits in ICV to correct
Send packet
RSN uses 1X to information AP in secure way
Rate limit keying to limit affect on other stations until their keys are attacked.
Tim Moore, Microsoft

8. Acks are generated very low in stack – below encryption/integrity
July 2002
Ack message
Need RA, more bit and Duration from frame to be acked
If more is 0 then do not need duration
Acks for data messages can cause data loss
Destroy message and then send ack
Timing is difficult to respond to a message with a valid ack especially for more=1 but could be done by random acks being sent for more=0
Acks are generated very low in stack – below encryption/integrity
So protecting is hard
Can detect acks received at wrong time
Should have MIB to log this occurring
Tim Moore, Microsoft

9. (Re-)Association request
July 2002
(Re-)Association request
Causes station to join DS
implementations send level 2 message to setup bridges
Pass data on/off DS
Change capabilities to AP
RSN IE
Listen interval – DoS causes AP to lose data and disassociate station
With RSN station should not join DS until 4-way handshake completes
Data isn’t sent on/off DS because keys are not configured but also need to hold up level 2 bridge message
Association allocates resources on AP
APs need to limit resources used and recover resources if 4-way handshake doesn’t complete
Tim Moore, Microsoft

10. July 2002
Note Draft 2.2 pre-auth has a problem in that 4-way handshake completes in pre-auth, anyone sending an association opened DS
Fixed in 298r3
Tim Moore, Microsoft

11. RSN – 802.11 auth is open (i.e. no security)
July 2002
Authentication
Open – no auth
Shared – dictionary attack
RSN – auth is open (i.e. no security)
Currently do open to return state machine to 1999 version but should we remove state 2 in RSN?
Tim Moore, Microsoft

12. (Re-)Association response
July 2002
(Re-)Association response
Change station state
Stations check they are in correct state
Flood AP with association requests for different mac addresses – resource DoS
If received when expecting then goes to correct state and real response is ignored
If received after then ignored
Limit resource usage, recover resources quickly if 802.1X key management doesn’t complete
Tim Moore, Microsoft

13. Probe request Wastes bandwidth Gets info from AP July 2002
Tim Moore, Microsoft

14. Beacon/Probe response
July 2002
Beacon/Probe response
Change capabilities of AP
Privacy bit
RSN information element
A rogue AP with different capabilities but same SSID
Discloses information about ciphers etc that helps attacker
Station select most secure capabilities of APs in range
DoS by more secure AP
RSN duplicate capabilities into 4-way handshake which is protected
RSN requires Privacy bit to be set
DoS attack by modifying 4-way handshake
RSN requires a configuration option to disallow non-RSN associations.
Tim Moore, Microsoft

15. Disassociation/De-authentication
July 2002
Disassociation/De-authentication
Deletes/changes state on AP
Remove stations from AP and DS
Nothing in RSN
Sign Disassociation/De-authenticate messages
Do not change MAC state
Re-authenticate 802.1X and let 1X delete MAC state
Tim Moore, Microsoft

16. Log packets sent on request of a PS-Poll that didn’t get received
July 2002
PS-Poll
Used by station to get AP to send packets to station
Causes packets to be dropped at the AP - Dos
Log packets sent on request of a PS-Poll that didn’t get received
Could be joined with ack spoofing to ack the data
Tim Moore, Microsoft

17. RTS/CTS Contention free/ack ATIM
July 2002
RTS/CTS
Not looked at because normally threshold large
Contention free/ack
ATIM
Tim Moore, Microsoft

18. Others Radio flood Interfere with packet CRC
July 2002
Others
Radio flood
Can we detect this as radio noise and add MIB variables to log it?
Interfere with packet CRC
Detect packet errors – packets with bad CRCs or in particular with radio noise corrupting CRC
Tim Moore, Microsoft

19. 802.1X Flood EAPOL-Start messages Flood EAP Request/Identity
July 2002
802.1X
Flood EAPOL-Start messages
DoS Authenticator
Flood EAP Request/Identity
Dos Supplicant
EAP_SUCCESS
Supplicant believes auth complete
RSN uses Secure bit for key management complete
RSN encrypts 1X with Pairwise key
EAP_FAILURE
DoS
Tim Moore, Microsoft

20. EAP Request/Identity contains identity information
July 2002
EAP_Logoff
Encrypt 1X
EAP Request/Identity contains identity information
Change identity for DoS
Read identity
EAP scheme such as EAP_PEAP or EAP_TTLS
Outer identity only needs NAI domain
Tim Moore, Microsoft

21. EAP_Start, logoff and Notification can be tampered with
July 2002
EAP_Start, logoff and Notification can be tampered with
RSN encrypts 1X after 4-way handshake
PEAP or TTLS will protect inner EAP
Tim Moore, Microsoft

22. July 2002
PSK
Bad pre-shared keys
Tim Moore, Microsoft

23. 4-way handshake Send message 1 with wrong ANonce
July 2002
4-way handshake
Send message 1 with wrong ANonce
Implementation mustn’t change session change until message 3
Changing dest MAC address – DoS
Tim Moore, Microsoft

24. Issues Association Disassociation/De-authenticate
July 2002
Issues
Association
Sign association message
Use 4-way handshake as network secure
This is in draft 2.2
Disassociation/De-authenticate
Sign disassociate
Can’t sign de-authenticate because there are cases when you can’t
Disassociation/De-authenticate force 802.1X reauth
If valid disassociate/de-authenticate then 802.1X fails and removes state
If spoofed disassociate/de-authenticate then 802.1X succeeds and state is not removed
Note: Could be used to force 802.1X reauths using resources
Tim Moore, Microsoft