1. RADIUS Client Kickstart
September 2002
RADIUS Client Kickstart
Robert Moskowitz, ICSALabs
John Vollbrecht, Interlink Networks
Robert Moskowitz, ICSALabs

2. Houston, we have a problem
September 2002
Houston, we have a problem
IEEE 802.1X RADIUS Usage Guidelines
“IEEE Std 802.1X-2001 enables authenticated access to IEEE 802 media, including Ethernet, Token Ring, and IEEE wireless LANs. Although RADIUS support is optional within IEEE Std 802.1X-2001, it is expected that most IEEE Std 802.1X-2001 Authenticators will function as RADIUS clients.”
RFC 2865 Sec 3
“A RADIUS server MUST use the source IP address of the RADIUS UDP packet to decide which shared secret to use, so that RADIUS requests can be proxied.”
Robert Moskowitz, ICSALabs

3. September 2002
Stated Simply
When an AP that supports 802.1x authentication is connected to the net it must be configured with:
the IP address or DNS name of its RADIUS server.
It must also have a shared secret with the RADIUS Server which is typically hand configured.
Finally, the AP must be registered with the DNS server, or assigned a permanent IP address.
This name or address must also configured in the RADIUS Server.
Robert Moskowitz, ICSALabs

4. What is wrong with this picture?
September 2002
What is wrong with this picture?
Setting up the RADIUS Client shared secret
“The secret (password shared between the client and the RADIUS server) SHOULD be at least as large and unguessable as a well-chosen password. It is preferred that the secret be at least 16 octets. This is to ensure a sufficiently large range for the secret to provide protection against exhaustive search attacks. The secret MUST NOT be empty (length 0) since this would allow packets to be trivially forged.”
This is done manually on the RADIUS Client and Server
Robert Moskowitz, ICSALabs

5. More Wrongness The IP address of the AP MUST be fixed
September 2002
More Wrongness
The IP address of the AP MUST be fixed
No DHCP, or use MAC controlled DHCP
Same IP address always assigned to a given MAC
Or AP’s DNS name available
DYNDNS required?
No mechanism to easily rekey MANY RADIUS Clients
Only the single AP with built-in RADIUS will NOT be challenged
Robert Moskowitz, ICSALabs

6. September 2002
How to fix this
Kickstart a Master Secret between the AP and RADIUS Server using a ‘guarded (e.g. SKIP)’ Diffie-Hellman exchange. RFC 2786 is the model
Diffie-Hellman USM Key -- SNMPv3 Key ‘ignition’
Secret is bound to AP’s name, i.e. BSSID
AP Boot Registration
Master Secret used to establish a Boot secret bound to the AP’s IP address
This is the RADIUS Client Shared Secret
This can also ‘plumb’ the f RADIUS keys
Robert Moskowitz, ICSALabs

7. September 2002
How to fix this
Master Secret Change using Diffie-Hellman for Perfect Forward Secrecy
See RFC Key Changes
A Key Change forces a Boot Registration
Robert Moskowitz, ICSALabs

8. Benefits No User configuration on APs
September 2002
Benefits
No User configuration on APs
No user interface on APs
Manageability of RADIUS Client secrets
Support for DHCP address assignment for APs
Robert Moskowitz, ICSALabs

9. General Approach Proposal
September 2002
General Approach Proposal
Kickstart design using Diffie-Hellman over SNMPv2
Controlled by MIBs (e.g. only possible in factory state)
AP Boot Registration using keywrapping over RADIUS without RADIUS authentication
Secret Change using Diffie-Hellman with old Diffie-Hellman (like SKIP PFS) over SNMPv2
Robert Moskowitz, ICSALabs

10. Where will work get done
September 2002
Where will work get done
IETF
Individual(s) submission -- No RADIUS workgroup
Looking for community of interest
Referenced by 802.1x Annex D
Robert Moskowitz, ICSALabs