Information
MS-CHAPv2 should be used for RADIUS authentication if RADIUS Servers are configured
Rationale:
RADIUS is a centralized Authentication, Authorization and Accounting (AAA) protocol providing services to authenticate users on routers, switches and other systems.
By default, JUNOS devices which are configured to use RADIUS for External AAA use the Password Authentication Protocol (PAP) for Authenticating users. PAP is an old standard, dating back to Dial-up Internet connections where interception was not considered viable; so PAP sends the user's password in plain-text (unencrypted) over the network to the RADIUS server, exposing the password to interception and misuse.
All current JUNOS devices support the use of the stronger MS-CHAPv2 (Microsoft Challenge Handshake Authentication Protocol, Version 2) standard for user Authentication, which is widely supported.
With CHAP, the password is never sent over the network. Instead a 'challenge' is encrypted by the RADIUS Server and sent to the JUNOS device, which decrypts the challenge using the configured Secret. The JUNOS device combines the the decrypted Challenge with the password provided by the user into a Hash, which is returned to the RADIUS Server which performs the same Hash of the Challenge and the users password to determine whether to permit or deny the request.
Use of MS-CHAPv2 on JUNOS Devices also allows for users to change their password if the password has expired.
Where RADIUS Servers are configured for External AAA, it is recommended that MS-CHAPv2 be used instead of, the default, PAP standard for user Authentication.
Impact:
Ensure that External AAA Servers are tested prior to deploying in a live environment.
It is generally recommended to configure a single 'Rescue' or 'Emergency' account locally under the [edit system login] hierarchy to provide access in the event of a AAA failure or mis-configuration prior to deploying External AAA.
Solution
Configure RADIUS to use MS-CHAPv2 Authentication using the following commands under the [edit system] hierarchy;
[edit system]
user@host#set radius-options password-protocol mschap-v2
Default Value:
No External AAA is configured by default.