2FA Ubuntu Desktop

In this small blog post I want to show how to enable 2FA in Ubuntu Desktop.

Prerequisites

Ubuntu Desktop installed on a VM or physical hardware
Access to a user with sudo rights

Setup

Log in with a user that has sudo rights.
Open the terminal and install the following package:
```
sudo apt install libpam-google-authenticator
```
After the installation we need to add the following line of code into this config file /etc/pam.d/common-auth:
```
sudo nano /etc/pam.d/common-auth
```
Add the following line of code at the end of the config file:
```
auth    required                        pam_google_authenticator.so echo_verification_code
```
Save and close the nano text editor with Ctrl+O and Ctrl+X
Setting up 2FA for the current user. For that put the following command into the terminal and hit enter:
```
google-authenticator
```

Now you get to answer a few questions:

Do you want authentication tokens to be time-based (y/n) y

Now the program has generated a QR-Code that you need to scan with a 2FA App that you need to download for your smartphone:

F-Droid:

Aegis Authenticator - 2FA App

Google Play:

After downloading an app, please scan the qr-code with one of these apps.

Now you need to verify the correct setup of the app by typing the 6-digit 2FA code from your app into the terminal of your Ubuntu Desktop machine. Please write down your emergency scratch codes for this account. With these codes you can gain access without the 2FA Codes from your Smartphone app (emergency).

Enter code from app (-1 to skip): 527250
Code confirmed
Your emergency scratch codes are:
  23231488
  76147310
  44302760
  67489244
  72861528

Save the config in your home directory:

Do you want me to update your "/home/suitdeer/.google_authenticator" file? (y/n) y

Disallow same authentication token for multiple uses:

Do you want to disallow multiple uses of the same authentication
token? This restricts you to one login about every 30s, but it increases
your chances to notice or even prevent man-in-the-middle attacks (y/n) y

Disable grace period (my opinion):

By default, a new token is generated every 30 seconds by the mobile app.
In order to compensate for possible time-skew between the client and the server,
we allow an extra token before and after the current time. This allows for a
time skew of up to 30 seconds between authentication server and client. If you
experience problems with poor time synchronization, you can increase the window
from its default size of 3 permitted codes (one previous code, the current
code, the next code) to 17 permitted codes (the 8 previous codes, the current
code, and the 8 next codes). This will permit for a time skew of up to 4 minutes
between client and server.
Do you want to do so? (y/n) n

Enable rate limiting:

If the computer that you are logging into isn't hardened against brute-force
login attempts, you can enable rate-limiting for the authentication module.
By default, this limits attackers to no more than 3 login attempts every 30s.
Do you want to enable rate-limiting? (y/n) y

Prerequisites

Setup

Enable 2FA for other users on this machine

Add a comment