Configuring SBC for RADIUS Authentication

Overview

The

Since 3.1 release, 

• Administrator
• Operator
• FieldService
• Guest
• SecurityAuditor
• Calea

Since the RADIUS protocol does not provide a means to assign users to a group, the implementation currently hard codes every RADIUS authenticated user to the Administrator group.

The

• Obtain Correct Privileges via RADIUS Transaction – When a user is authenticated using RADIUS, the correct privilege is obtained via RADIUS transaction itself using a Vendor Specific Attribute (VSA).
  
  
• Configure Multiple RADIUS Servers – Up to three RADIUS servers are now configurable per
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  .

To configure RADIUS authentication for

Obtain Correct Privileges via RADIUS Transaction

When a user is authenticated via RADIUS, the user is assigned to a group provided by the RADIUS server as part of the ACCESS_ACCEPT packet.

For SBC RADIUS authentication, RADIUS server is configured to return the group name using a VSA in ACCESS_ACCEPT packet. The VSA should be in the following format.

0               1               2               3       
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Type      |  Length       |            Vendor-Id
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     Vendor-Id (cont)           | Vendor type   | Vendor length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    Attribute-Specific...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

The Vendor-Id is a SMI Network Management Private Enterprise Code of the vendor Sonus as specified in RFC 2865.

• Vendor ID for Sonus is "2879".
• Vendor type can be "1" considering this is the first instance of using VSAs. Type "1" can be the identifier for a group name from server.
• Vendor length is the length of the group name itself. This is followed by a string consisting of a case-sensitive group name.

If the RADIUS server does not provide a group or provides a group name which is not present in the SBC in the ACCESS_ACCEPT response, the user is denied access, and a log is written to the SECURITY event log stipulating that SBC received an invalid group name from the RADIUS server.

Configure Multiple RADIUS Servers

The SBC is enhanced in this release to configure up to three RADIUS servers per SBC with the addition of radiusServer and retryCriteria parameters to radiusAuthentication configuration object.

When more than one RADIUS server is configured and RADIUS authentication is attempted, the server configured with the least priority value is tried first. If fallback is configured, the inverse priority order is followed to pick the next server for authentication. SBC allows a configurable number of retries and time-outs before retry.

Once the SBC sends an ACCESS_REQUEST, it waits until a configured amount of time (retryTimer) before resending the ACCESS_REQUEST. After a configurable number of failed attempts (retryCount), the RADIUS server is marked as unavailable, or out of service (OOS) for a configured amount of time (oosDuration), and the SBC moves to the next configured RADIUS server based on the configured priority. Once all RADIUS servers are attempted and deemed unreachable (or no responses are received), the SBC falls back to Local Authentication (if Local Authentication is enabled).

SBC includes statistics to check the status of a RADIUS server, as well as the time when an unavailable server automatically becomes available again. See "radiusAuthentication" statistic details at Show Table OAM or Show Status OAM pages.

Enabling Remote Authentication

To enable remote authentication:

1. Login to SBC CLI.
   
   

2. Change to the Configuration mode:

   > configure private

    

3. Execute the following command:

   % set system admin <system name> localAuthenticationEnabled false externalAuthenticationEnabled true

Configuring RADIUS Server

To configure the remote RADIUS Server:

1. Log on to SBC CLI.

2. Change to the Configuration mode:

   > configure private

    

3. Execute the following command:

   % set oam radiusAuthentication 
   	radiusServer <server name>
   		mgmtInterfaceGroup <string>
   		priority <#>
   		radiusNasIp <x.x.x.x>
   		radiusServerIp <x.x.x.x>
   		radiusServerPort <#>
   		radiusSharedSecret <8-128>
   		state <disabled | enabled>
   	retryCriteria
   		oosDuration <# minutes>
   		retryCount <#>
   		retryTimer <# milliseconds>