FreeRADIUS InkBridge

WiMAX Module

The wimax module implements the WiMAX attributes as defined in NWG_R1_V1.2.1-Stage-3.pdf

It should be listed in the recv Access-Request and recv Accounting-Request sections.

The module will change the horrible binary version of Calling-Station-Id to the normal format, as specified in RFC 3580, Section 3.21.

recv Access-Request

In the recv Access-Request section. the `wimax module fixes up various non-standard WiMAX issues.

The WiMAX specification says that the Calling-Station-Id is 6 octets of the MAC. This definition conflicts with RFC 3580, and all common RADIUS practices. Uncommenting the wimax module here allows the module to change the Calling-Station-Id attribute to the normal format as specified in RFC 3580 Section 3.21.

send Access-Accept

In order to calculate the various WiMAX keys, the module should be listed in the send Access-Accept section. If EAP authentication has been used, AND the EAP method derives MSK and EMSK, then the various WiMAX keys can be calculated.

send Access-Accept {

Miscellaneous

Some useful things to remember:

Attribute Description

WiMAX-MSK

EAP MSK, but is 64 octets.

MIP-RK-1

HMAC-SHA256(ESMK, "miprk@wimaxforum.org" | 0x00020001)

MIP-RK-2

HMAC-SHA256(ESMK, MIP-RK-1 | "miprk@wimaxforum.org" | 0x00020002)

MIP-RK

Same as MIP-RK-1 | MIP-RK-2

MIP-SPI

First 4 octets of HMAC-SHA256(MIP-RK, "SPI CMIP PMIP")

You have got to track all MIP-SPI’s on your system!

Attribute Description

SPI-CMIP4

MIP-SPI

SPI-PMIP4

MIP-SPI + 1

SPI-CMIP6

MIP-SPI + 2
MN-NAI

Mobile node NAI.

You have to create it, and put it into the request or reply as something like:

WiMAX-MN-NAI = User-Name}

You will also have to have the appropriate IP address (v4 or v6) in order to calculate the keys below.

Lifetimes are derived from Session-Timeout. It needs to be set to some useful number.

The hash function below H() is HMAC-SHA1.
MN-HA-CMIP4

MN-HA-CMIP4 = H(MIP-RK, "CMIP4 MN HA" | HA-IPv4 | MN-NAI)

Where HA-IPv4 is WiMAX-hHA-IP-MIP4 or maybe WiMAX-vHA-IP-MIP4

  • Which goes into WiMAX-MN-hHA-MIP4-Key

  • or maybe WiMAX-RRQ-MN-HA-Key

  • or maybe even WiMAX-vHA-MIP4-Key

The corresponding SPI is SPI-CMIP4, which is MIP-SPI,

  • Which goes into WiMAX-MN-hHA-MIP4-SPI

  • or maybe WiMAX-RRQ-MN-HA-SPI

  • or even WiMAX-MN-vHA-MIP4-SPI

    MN-HA-PMIP4 = H(MIP-RK, "PMIP4 MN HA" | HA-IPv4 | MN-NAI)
MN-HA-CMIP6 = H(MIP-RK, "CMIP6 MN HA" | HA-IPv6 | MN-NAI)

Both with similar comments to above for MN-HA-CMIP4.

In order to tell which one to use (CMIP4, PMIP4, or CMIP6), you have to set WiMAX-IP-Technology in the reply to one of the appropriate values.

FA-RK = H(MIP-RK, "FA-RK")
MN-FA = H(FA-RK, "MN FA" | FA-IP | MN-NAI)

Where does the FA-IP come from? No idea…​

The next two keys (HA-RK and FA-HA) are not generated for every authentication request, but only on demand.

HA-RK = 160-bit random number assigned by the AAA server to a specific HA.

FA-HA = H(HA-RK, "FA-HA" | HA-IPv4 | FA-CoAv4 | SPI)

where HA-IPv4 is as above.

and FA-CoAv4 address of the FA as seen by the HA and SPI is the relevant SPI for the HA-RK.

DHCP-RK = 160-bit random number assigned by the AAA server to a specific DHCP server. vDHCP-RK is the same thing.

Configuration Settings

delete_mppe_keys

Some WiMAX equipment requires that the MS-MPPE-*-Key attributes are sent in the Access-Accept, in addition to the WiMAX-MSK attribute.

Other WiMAX equipment request that the MS-MPPE-*-Key attributes are NOT sent in the Access-Accept.

By default, the EAP modules sends MS-MPPE-*-Key attributes.

The default virtual server (raddb/sites-available/default) contains examples of adding the WiMAX-MSK.

This configuration option makes the WiMAX module delete the MS-MPPE-*-Key attributes.

If the keys are deleted (by setting this to yes), then the WiMAX-MSK attribute is automatically added to the reply.

The default is to leave them in place.

Default Configuration

#	recv Access-Request {
#		...
#		wimax
#		...
#	}
#		...
#		# define the WiMAX NAI
#		request.WiMAX-MN-NAI = User-Name
#		# Update the reply with "template" values. The wimax module
#		# will see this, and replace the template values with the
#		#correct ones taken from the cryptographic calculations,
#		reply += {
#			Vendor-Specific.WiMAX = {
#				FA-RK-Key = 0x00
#				MSK = reply.EAP-MSK
#			}
#		}
#		#  You may want to delete the `MS-MPPE-*-Keys` from the
#		#  reply, as some WiMAX clients behave badly when those
#		#  attributes are included. See the configuration entry
#		#  `delete_mppe_keys` for more information.
#		#
#		wimax
#		...
#	}
wimax {
	delete_mppe_keys = no
}