Configuring SBC for RADIUS Authentication

Overview

The SBC Core is configurable using CLI and EMA interfaces, and the access to these interfaces are authenticated using the user credentials. User credentials can be verified using local or external authentication. For local authentication, the user credentials are validated against a locally stored user database. For external authentication, the user credentials are sent to a remote Remote Authentication Dial In User Service (RADIUS) server and authenticated. The username and encrypted password are sent to the remote RADIUS server in an ACCESS_REQUEST packet. The user is allowed/denied access to the SBC based on the response from the RADIUS server. 

SBC users are currently segregated into the following groups which define the privileges of each user. Access to data/commands is allowed/prevented based on the group of the user who is trying to acquire the access.

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

To configure RADIUS authentication for SBC Core, you must first enable external authentication and then configure the remote RADIUS server.

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 an SMI Network Management Private Enterprise Code of the vendor Ribbon as specified in RFC 2865.

• Vendor ID for Ribbon 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 the SBC received an invalid group name from the RADIUS server.

Configure Multiple RADIUS Servers

The SBC supports configuring 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.

Enable Remote Authentication

To enable remote authentication:

1. Log into the SBC CLI.

2. Change to Configuration mode:

   > configure private

3. Execute the following command:

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

Configure a RADIUS Server

To configure a remote RADIUS Server:

1. Log into the SBC CLI.

2. Change to 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>

The supports all alphabetical, numeric, and special characters for setting the radiusSharedSecret key.

The following characters in the key must be escaped while setting a radiusSharedSecret for configuring a RADIUS server:

• # (hash) anywhere in the key
• \ (backslash) anywhere in the key
• “ (double quotes) at the beginning or end of the key

For example,

• Un-escaped key: ThisIsARadiusKeyWithDoubleQuote”andBackSlash\Hash#andAdoubleQuoteAtTheEnd”
• Escaped string: ThisIsARadiusKeyWithDoubleQuote”andBackSlash\\Hash\#andAdoubleQuoteAtTheEnd\”