Securing Junos: User Accounts, Login Classes, and Authentication

In this blog post, we will delve into the world of Junos security, focusing on user accounts, login classes, and authentication. This is a crucial topic for those studying for the JNCIS-ENT certification, as it forms a significant part of the exam.

User Accounts

In Junos, user accounts are used to control access to the device. Each user account has a unique username and password, and is assigned a specific login class that determines the user's permissions.

To create a user account, use the set system login user command followed by the username. For example:

set system login user admin

This command creates a user account with the username 'admin'. To set a password for the user, use the authentication keyword followed by the plain-text-password keyword:

set system login user admin authentication plain-text-password

After entering this command, you will be prompted to enter and confirm the password.

Login Classes

Login classes in Junos are used to define the permissions for user accounts. There are several predefined login classes, including 'super-user', 'operator', 'read-only', and 'unauthorized'.

To assign a login class to a user, use the class keyword followed by the name of the login class. For example:

set system login user admin class super-user

This command assigns the 'super-user' login class to the 'admin' user. The 'super-user' login class has all permissions, allowing the user to view and modify the configuration, and to perform operational mode commands.

Authentication

Authentication in Junos is the process of verifying the identity of a user. Junos supports several authentication methods, including password authentication, public key authentication, and RADIUS authentication.

Password authentication is the simplest method. When a user attempts to log in, they are prompted to enter their password. If the entered password matches the password stored in the user account, the user is authenticated.

Public key authentication is a more secure method. In this method, a pair of cryptographic keys is used: a private key that is kept secret by the user, and a public key that is stored in the user account on the Junos device. When a user attempts to log in, the device uses the public key to encrypt a challenge, which the user must decrypt using their private key to prove their identity.

RADIUS authentication is a method that uses a RADIUS server to authenticate users. When a user attempts to log in, the Junos device sends an authentication request to the RADIUS server, which checks the user's credentials against its database.

To configure RADIUS authentication, use the set system authentication-order command followed by 'radius':

set system authentication-order radius

This command sets RADIUS as the first method in the authentication order. If RADIUS authentication fails, the device will fall back to the next method in the order.

In conclusion, understanding user accounts, login classes, and authentication is essential for securing a Junos device. By properly configuring these features, you can control who has access to your device and what they can do, helping to protect your network from unauthorized access and malicious activity.