SiteMinder responses can be used to return RADIUS attributes to the NAS device if the user is authenticated. Attributes configure the characteristics of the session once the user is authenticated and define the user profile of the authenticated user. The user profile can be used by the NAS device. For example, using attributes in a response, you can define time limits for the RADIUS user session.
Using responses, you can provide the NAS device with user profile information that assigns privileges to the user. For example, you could allow one user unlimited access to a resource, yet limit another user’s access to the same resource. Used in this way, responses give you the ability to authorize users even though RADIUS is primarily only a mechanism for authentication.
Note: If the NAS specifies authentication only, by default, SiteMinder does not return RADIUS attributes. To return RADIUS attributes when the NAS specifies authentication only, follow the instructions in Configure SiteMinder to Always Return RADIUS Attributes.
RADIUS responses are paired with rules that authenticate. If a rule authenticates a user successfully, the RADIUS response is triggered. If the rule does not authenticate the user, the response is not triggered.
If a response is triggered, the Policy Server sends the attributes contained in the response to the NAS device. This information is used to customize the user’s session, as shown in the following diagram:
You can use the following attributes in responses:
These attributes return information associated with a user in an LDAP, WinNT, or ODBC user directory. User attributes are retrieved from the user directory and can used to modify the behavior of the RADIUS device.
These attributes return profile information associated with an LDAP directory object related to the user. For example, the DN attribute could return information about LDAP objects such as the user’s group or organizational unit (OU).
These attributes return values from a custom library that was developed using the SiteMinder Authorization API. An active response is generated when SiteMinder invokes a function in the custom library.
These attributes return values defined by the following Agent type attributes:
Generic RADIUS attributes, as defined by the RADIUS Protocol specification, Request for Comment (RFC) 2138. The identifiers for these attributes include 1-25 and 27-63. Some of these attributes may be used multiple times in the same response.
Any RADIUS Agent type can return a response that includes generic RADIUS attributes.
Attributes defined in the Dictionary file of the NAS device. These attributes define values that are not defined by generic RADIUS attributes and are specific to the type of NAS device in use. The unique identifiers for these attributes extend beyond the range reserved for generic RADIUS attributes, starting with 64. For example, Lucent provides an extended RADIUS attribute called Ascend-Disconnect-Cause, which uses the identifier 195.
Only Agent types that match the vendor type of the extended RADIUS attribute can use the attribute. For example, a Shiva Agent type can use the extended RADIUS attributes defined for Shiva, but a Cisco Agent type cannot use Shiva extended attributes in a response. The extended attributes that are used in a response must match the attributes defined in the Dictionary file of the RADIUS client.
By default, SiteMinder provides pre-defined RADIUS extended attributes for some Agent Types that use these attributes, such as Ascend (Lucent). You can also define additional RADIUS extended attributes for any of the RADIUS Agent types, if necessary.
Attributes defined in the Dictionary file of the NAS device, which use 26 as an identifier. Vendor-specific attributes enable you to define attributes for values that are not provided by the generic RADIUS attributes. Some vendors use vendor-specific attributes in place of or in addition to RADIUS extended attributes. For example, Cisco does not use RADIUS Extended attributes; however, this NAS device supports several vendor-specific attributes, such as Cisco AV–pair and Account-Info.
You can use vendor-specific attributes to pass information to other protocols. For example, you can define a vendor specific attribute for the Cisco AV–pair attribute to pass TACACS+ information to a TACACS+ server.
Vendor-specific attributes can only be defined in responses that match the vendor type of the RADIUS client.
By default, SiteMinder provides pre-defined vendor-specific attributes for some Agent Types that use these attributes, such as the Network Associates' Sniffer Agent type. You can also define additional RADIUS extended attributes to any of the RADIUS Agent types, if necessary.
Note: For more information about RADIUS attributes, see Request for Comment (RFC) RADIUS Protocol 2138.
Some NAS devices always expect RADIUS responses in the Access-Accept, even if the NAS specifies authentication only. If the NAS specifies authentication only, by default, SiteMinder does not return RADIUS attributes.
To always return RADIUS attributes to a NAS device, create a new registry value with the following parameters:
Note: The install program does not create a registry entry for AlwaysReturnRadiusAttrs. Until you create and set the entry, SiteMinder uses the default value of 0.
After you set AlwaysReturnRadiusAttrs to a value greater than zero, the following message will appear in the Authentication Server’s debug log:
Radius Attributes will be returned regardless of RA_SERVICE_TYPE_AUTHENTICATE_ONLY
Before you can use an attribute in a response, the attribute must be made available to the Agent type returning the response. Attributes are made available to Agent types by defining the attributes in Agent types. Although many Agent types are pre-configured with vendor-specific and RADIUS extended attributes, you can add additional extended RADIUS, generic RADIUS, and vendor-specific attributes to Agent types, as needed.
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