Two-factor authentication w/ privacyIDEA and YubiKey Rev 1

privacyIDEA is a modular authentication server that can be used to enhance the security of your existing applications like local login, VPN, remote access, SSH connections, access to web sites or web portals with two-factor authentication.

privacyIDEA websiteopen in new window GitHubopen in new window
Yubico websiteopen in new window affiliate links

Setup and configuration has been tested on the following operating systems:

ko-fiopen in new window


Configuration files

Install community edition

We will use privacyIDEA and their FreeRADIUS plugin together with YubiKey 5 NFCopen in new window (from Yubico) to enforce two-factor authentication and apply an role-based access control approach (RBAC). We will simplify the user accounting by fetching the users from the local /etc/passwd file and use it as the privacyIDEA resolver (instead of e.g. LDAP, SQL. You can read more about resolvers hereopen in new window). To get an hands-on experience we will use the privacyIDEA authentication server to access the Greenbone Vulnerability Manager's user interface.


This is the first revision for privacyIDEA. We will write more about the different modular options e.g. LDAP as resolver in future releases. If there's any particular configuration you would like us to cover feel free to create a new Feature requestopen in new window.

To get started download the signed key.

server@ubuntu:~$ wget

Next import the signed key.

server@ubuntu:~$ sudo gpg --import --import-options show-only --with-fingerprint NetKnights-Release.asc
pub rsa4096 2017-05-16  NetKnights GmbH <>
Key fingerprint = 0940 4ABB EDB3 586D EDE4  AD22 00F7 0D62 AE25 0082

Continue by adding the key to our system.

server@ubuntu:~$ sudo apt-key add NetKnights-Release.asc

Now we need to add the repository for the specific release (in this case Ubuntu 20.04).

server@ubuntu:~$ sudo add-apt-repository
server@ubuntu:~$ sudo apt-get update


If you prefer to use the nginx version you can install apt-get privacyidea-nginx

Once we updated the package manager we can install PrivacyIDEA.

server@ubuntu:~$ sudo apt-get update
server@ubuntu:~$ sudo apt-get install privacyidea-apache2
             _                    _______  _______
   ___  ____(_)  _____ _______ __/  _/ _ \/ __/ _ |
  / _ \/ __/ / |/ / _ `/ __/ // // // // / _// __ |
 / .__/_/ /_/|___/\_,_/\__/\_, /___/____/___/_/ |_|
/_/                       /___/

Running online

Let's create the administration account.

server@ubuntu:~$ sudo pi-manage admin add admin -e admin@localhost
Admin admin was registered successfully.

Once you've added the administrator account and followed the firewall settings you should be able to reach the web interface from and login as the admin user with your password.

PrivacyIDEA login

privacyIDEA FreeRADIUS plugin

Now we will install the privacyIDEA freeRADIUS plugin, which we will be using to enable RADIUS for Greenbone Vulnerability Manager.

server@ubuntu:~$ sudo apt-get install privacyidea-radius

In the clients.conf we will add our client(s), which in this case is our Greenbone Vulnerability Manager. Define the IP address of the Greenbone Vulnerability Manager and set the secret (do not use the default secret).

server@ubuntu:~$ sudo -i
root@ubuntu:~$ sudo nano /etc/freeradius/3.0/clients.conf
#client {
#       ipaddr          =
#       secret          = testing123
client GVM {
        ipaddr =
        secret = testing123


In the sites-enabled folder you will find the default authentication settings for privacyIDEA. Leave the default perl-privacyidea type.

root@ubuntu:~$ cd /etc/freeradius/3.0/sites-enabled/
root@ubuntu:~$ cat privacyidea
server {
    authorize {
        if (ok || updated) {
            update control {
                Auth-Type := Perl
    listen {
        type = auth
        ipaddr = *
        port = 0
    authenticate {
        Auth-Type Perl {


The authentication type which is an enabled mod is located in the mods-enabled directory and you will see the module file. Leave the default settings.

root@ubuntu:~$ cd /etc/freeradius/3.0/mods-enabled/
root@ubuntu:~$ cat mods-perl-privacyidea
perl perl-privacyidea {
    filename = /usr/share/privacyidea/freeradius/

Configure privacyIDEA

As we configured the local freeRADIUS plugin and added Greenbone Vulnerability Manager as a client we will now configure the privacyIDEA authentication server. The freeRADIUS plugin doesn't have to be installed on the same server as privacyIDEA. You can define this in the rlm_perl.ini file. In this tutorial we will leave the default localhost as our domain.

root@ubuntu:~$ exit
server@ubuntu:~$ sudo nano /etc/privacyidea/rlm_perl.ini
URL = https://localhost/validate/check
#REALM = someRealm
#RESCONF = someResolver
SSL_CHECK = false
#DEBUG = true


Configure YubiKey for privacyIDEA


privacyIDEA requires YubiKey 5 NFCopen in new window.

Start YubiKey Personalization Tool. Go to Settings. In the Logging Settings select Flexible format and add {serial}, {secretKeyTxt} variables in the form field.

yubikey settings

Next click the OATH-HOTP tab. Select which slot you wish to write your configuration to. Uncheck OATH Token Identifier and create the secret key by pressing the Generate button. Complete the build by clicking the Write Configuration button and save the CSV file.

yubikey hotp

Enroll token w/ YubiKey

Before we enroll the token with YubiKey we will create a resolver and realm and select the first user. Login to privacyIDEA at e.g. In the top menu click Config. Next click the Users tab and select New passwdresolver. Once you've given the resolver a name click the Save Resolver button.

privacyidea resolver

Next we will create the realm. Click the tab Realms. Give the realm a name and check the passwdresolver we just created. Click Create Realm.

privacyidea realm

Now lets select the first user. In the top menu click Users. Select the realm we just created in the left dropdown menu. This will show the list of all users from the /etc/passwd file. You can select any user from the list. We will go with the user mail for this example.

privacyidea users

Once you've decided which user you will connect to the YubiKey you can now assign your first token to a user. In the top menu click Token and select Import Tokens in the left menu. Select authentication method OATH CSV and realm. Click the Select file and import button and upload the file that you created earlier from the YubiKey configuration.

privacyidea assign token

Go back to All tokens in the left menu and you will see your newly enrolled token. Click the serial number for further details.

privacyidea token

Here you will see the specific settings and details for the newly enrolled token. Now we will assign this token to the user. In the Assign User section select the Realm, fill in the Username you selected from the resolver list and finally set a PIN (in this example we used mail as the PIN). Click the Assign User button.

privacyidea assign token

Next lets test if the token works. Above the Assign User section, in the form field next to the test token button, type your selected PIN and click your YubiKey 5 NFCopen in new window button and hit the Test token button.

privacyidea test token

You can also test if privacyIDEA grants access to the freeRADIUS client directly from the command-line. Fill in your User-Name, insert your PIN within the User-Password variable and hit your YubiKey button to output the token. Make sure to also define your secret.

server@ubuntu:~$ echo "User-Name=mail, User-Password=mail123456" | radclient -x -s localhost auth testing123
Sent Access-Request Id 61 from to length 44
        User-Name = "mail123456"
        User-Password = "mail123456"
        Cleartext-Password = "mail123456"
Received Access-Accept Id 61 from to length 48
        Reply-Message = "privacyIDEA access granted"
Packet summary:
        Accepted      : 1
        Rejected      : 0
        Lost          : 0
        Passed filter : 1
        Failed filter : 0


Now go to the Config menu and select the System tab. In the System Config add in the Override Authorization Clients field to enable the validation check against the local subnet (e.g. Click the Save System Config button.

privacyidea override authentication

Enable 2FA for Greenbone Vulnerability Manager

Login to your Greenbone Security Assistant at e.g. Once you've logged in select Administration and RADIUS in the top menu. Click the Edit Radius Authentication button. Check the Enabled box, add the RADIUS host IP address e.g. and your secret key. Click the Save button.

greenbone security assistant radius

Next lets add the user to the Greebone Security Assistant (GSA). Select Administration and Users in the top menu. Click the New User button. Check RADIUS Authentication Only, select preferred user role and/or group. Add the privacyIDEA IP address in the Host Access field (e.g. and check Deny all and allow. If you want to lock access for the local subnet to GSA you can check Deny all and allow in the Interface Access and enter Once done click the Save button.

greenbone security assistant user

Logout as administrator from the Greenbone Security Assistant. Add the Username of your newly created user. In the Password field type the PIN and hit the YubiKey button (do not click the Sign In button) and you should successfully be authenticated.

greenbone security assistant login

Firewall settings

The firewall being used is UFW (Uncomplicated Firewall). It is set by default to deny incoming traffic, allow outgoing traffic and allow port 22 (OpenSSH). Read more about UFW hereopen in new window.

UFW Settings
server@ubuntu:~$ sudo ufw default deny incoming
server@ubuntu:~$ sudo ufw default allow outgoing
server@ubuntu:~$ sudo ufw allow 22
server@ubuntu:~$ sudo ufw enable
Command may disrupt existing ssh connections. Proceed with operation (y|n)? y
Firewall is active and enabled on system startup
server@ubuntu:~$ sudo ufw allow 443 comment "privacyIDEA"


pi-manage adminAdd or edit existing admin account


If you encounter any issue or having questions regarding privacyIDEA I recommend using their very helpful community forumopen in new window.

Enterprise solutions non-sponsored

NetKnights privacyIDEA Enterprise Edition

privacyIDEA is a modular solution for two factor authentication especially with OTP tokens. It is multi-tenency- and multi-instance-capable. Due to the modular structure privacyIDEA can be quickly and easily adapted and enhanced. E.g. adding new token types is as simple as writing a new lean python module. You do not need to modify your network for privacyIDEA, it does not write to existing databases or user stores. It only needs read access to your user stores like LDAP, Active Directory, SQL, SCIM-service or flat files. Existing workflows can be enhanced without the need to modify them. Using its simple REST like API it can be automated and smoothly be integrated.

NetKnightsopen in new window

YubiEnterprise affiliate links

Yubico offers enterprise solutions and can easily procure and distribute YubiKey authentication solutions for employees at scale.

Yubicoopen in new window