Setting up external Radius server for RUTOS authentication

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Summary

In this example, we will set up a Teltonika Networks router to use a Radius server for SSH and/or WebUI authentication. We will use the freeradius package to set up a local Radius server on an Ubuntu virtual machine. Then we will create a new user. Lastly, we will test the configuration.

This is the idea of how a Radius server is used for RUTOS authentication:

Topology used in this example

Prerequisites

Router with the ability to install the PAM package and running firmware version 7.6 or later
Ubuntu machine with the ability to host a local FreeRadius server

Note: in this example Ubuntu version 22.04.3 LTS was used

Preparing Ubuntu machine

Installing the FreeRadius server

Firstly, update the package source lists and upgrade the packages to their latest version:

sudo apt update
sudo apt upgrade

Next, install the FreeRadius package:

sudo apt install freeradius

Defining a client

Client - a router that will use FreeRadius to authenticate WebUI and/or SSH users. In order to add/edit clients, we need to access the clients.conf file. Use your favorite text editor to edit it:

sudo nano /etc/freeradius/3.0/clients.conf

For this example, we will add the following lines in order to accept any IP address as a client:

client 0.0.0.0/0 {
    secret = demoscrt
    shortname = 0.0.0.0/0
}

Note: a specific public IP of the client can be used instead of 0.0.0.0/0

Defining user login credentials

Before we create the user's login credentials, let's create an MD5 hash and use it instead of a clear text password. We will generate a hash value of demo123 using the following command:

echo -n demo123| md5sum | awk '{print $1}'

We will now define credentials for user demo. Use your favorite text editor to edit the file users:

sudo nano /etc/freeradius/3.0/users

Add the name of the user, MD5 hash value of its password, and a reply message:

demo     MD5-Password:= "62cc2d8b4bf2d8728120d052163a77df"
       Reply-Message := "Hello, %{User-Name}"

Once these changes are made, start the FreeRadius service:

sudo /etc/init.d/freeradius start

Preparing router

Setting a static IP for the FreeRadius server

Firstly, we will set a static IP for the Ubuntu machine running FreeRadius server. To do that you can use two methods.

First method

Connect to the WebUI
Navigate to Status → Network → LAN
In the DHCP Leases section you should see Ubuntu machine's IP address
Press near the instance to create a static IP lease

Second method

Connect to the WebUI
Navigate to Network → DHCP → Static Leases
Add the Ubuntu machine's MAC, IP, and provide a description

Press

Creating a new RUTOS user

Now we will need to create a new user for SSH and/or WebUI access. To do that follow these steps:

Go to System → Administration → User Settings → System Users section
In the Add new user section fill in the user's login credentials.

You can specify your own custom role or choose one from the default roles. In this example, the admin role was chosen.

Remember: use the same username as in FreeRadius users file. The password can be different, compared to the one in FreeRadius users file.

PAM package installation

Now we will need to install a PAM package, to do that follow these steps:

Go to System → Package Manager → Packages
Install the PAM package

Radius server configuration

Now we will set the FreeRadius server's information on the router

For SSH authentication

Firstly, we will need to enable SSH access for the created user. To do that, follow these steps:

Go to System → Administration → User Settings → System Users section
Press near the newly created user
Enable the SSH access
Press

To enable PAM authentication for SSH, follow these steps:

Go to System → Administration → Access Control → PAM section
Press near the SSH instance
Enable the instance
Set module to RADIUS
Set type to Required
Set server to Ubuntu machine's IP
Set secret to the one defined in the FreeRadius clients.conf file
Leave Port and Timeout to their default values

Press

For WebUI authentication

To enable PAM authentication for WebUI, follow these steps:

Go to System → Administration → Access Control → PAM section
Press near the WebUI instance
Enable the instance
Set module to RADIUS
Set type to Required
In the Select users add the newly created user or enable PAM authentication for all users
Set server to Ubuntu machine's IP
Set secret to the one defined in the FreeRadius clients.conf file
Leave Port and Timeout to their default values

Press

Testing configuration

Now that we have the setup configured, we can test if the server properly authenticates the user. To see authentication requests on the FreeRadius server side, follow these steps:

Stop the FreeRadius service using this command:

sudo /etc/init.d/freeradius stop

Start the FreeRadius server in debug mode using this command:

sudo freeradius -X

Try connecting to the router's WebUI and/or SSH service

If the authentication is successful the server logs will contain these lines:

Auth-Type PAP {
 pap: Login attempt with password
 pap: Comparing with "known-good" MD5-Password
 pap: User authenticated successfully
     [pap] = ok
   } # Auth-Type PAP = ok

If the authentication is unsuccessful the server logs will contain these lines:

Auth-Type PAP {
 pap: Login attempt with password
 pap: Comparing with "known-good" MD5-Password
 pap: ERROR: MD5 digest does not match "known good" digest
 pap: Passwords don't match
     [pap] = reject
   } # Auth-Type PAP = reject