Access Control Concepts

Network Access Control Technologies

RADIUS-PAP and RADIUS-CHAP, while not very secure, are more secure than simple PAP and CHAP. For example, a PEP and a RADIUS server have a shared secret, which authenticates their messages to each other. The PEP also encrypts PAP passwords with this secret, lending a limited degree of security to PAP.

In addition to PAP and CHAP, the RADIUS protocol works with EAP. The EAP AVP contains an entire EAP packet, allowing a PEP to shuttle EAP messages between the supplicant and the RADIUS server within RADIUS packets.

802.1X relies on RADIUS and EAP.

Wireless Authentication

Authentication protocols and access control methods are more or less stan- dardized; they function similarly whether implemented on an Ethernet port, a PPP connection, or a wireless (802.11) association. This does not mean, however, that the connection type is irrelevant to the design. Characteristics of a wireless network—particularly its open, shared medium—create vulnerabilities that you must factor into your design. This section equips you with the necessary knowledge about wireless technologies and protocols.

802.11

IEEE 802.11 is the Physical and Data-Link Layer standard for wireless connec- tions. While most specifications in this standard are irrelevant to access control, you should understand how an 802.11 endpoint connects to a wireless AP.

1.The endpoint sends an 802.11 authentication request. (This request is sometimes referred to as the association request.)

2.The AP sends an 802.11 authentication success response.

N o t e

The AP always allows 802.11 authentication to succeed because it should

 

 

enforce open authentication. When 802.11 was first adopted, it defined

 

 

another option: shared-key authentication, which required wireless users

 

 

to enter the correct password (actually, an encryption key). However, this

 

 

authentication method included several major flaws and has since been

 

 

denigrated.

 

 

 

3.

The endpoint sends an 802.11 association request.

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