How to enable two-factor authentication for SSH in Fedora Linux

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Any machine that permits SSH login would profit from the addition of two-factor authentication.

Picture: Jack Wallen

Whether or not you utilize Fedora Linux for a desktop or server, you need to think about enabling two-factor authentication for Safe Shell (SSH) login. Why? As a result of SSH is the first technique of remotely logging right into a server, and the very last thing you need is to depart that service open for assaults.

One method to higher lock that down is by enabling two-factor authentication for SSH. I need to stroll you thru the steps of doing simply that, so you possibly can get pleasure from extra safety together with your Fedora desktops and servers.

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What you want

To make this work, you want the next:

  • An occasion of Fedora up and operating.
  • A consumer account with sudo entry.
  • A 3rd-party authenticator app (similar to Authy) in your cell machine.

Let’s make this work.

A phrase of warning

Earlier than you get into this, I extremely suggest this arrange is completed when you may have bodily entry to the Fedora machine in query. Ought to one thing go awry, you need to have the ability to log into the machine instantly, so you possibly can troubleshoot the difficulty.

Set up

Step one is to put in the Google Authenticator. Open a terminal window and difficulty the next command:

sudo dnf set up google-authenticator nano -y

As soon as that set up completes, run the instrument with the command:

google-authenticator

You may be requested the next questions (reply sure to every):

Would you like authentication tokens to be time-based (y/n) y
Would you like me to replace your "/residence/consumer/.google_authenticator" file (y/n)? y

The app will then show a QR code, which you’ll need to scan into Authy (in your cell machine). Additionally, you will be supplied with an inventory of secret codes, which you’ll need to repeat and save in a secret, safe location. When you efficiently scan the QR code and save the restoration codes, you will be requested three extra questions (once more, reply sure to every).

Configure SSH

Earlier than you do that, just be sure you can SSH into the Fedora machine. Out of the field, the SSH daemon won’t be operating, so begin and allow it with the next instructions:

sudo systemctl begin sshd
sudo systemctl allow sshd

As soon as SSH is operating and enabled, ensure to repeat your SSH key to this machine (for SSH key authentication), from any/all machine(s) you propose on utilizing to realize distant entry. This may be executed by operating the next command from every machine that may want entry:

ssh-copy-id [email protected]_IP

The place USER is the username on the Fedora machine and FEDORA_IP is the IP tackle of your Fedora machine.

As soon as you’ll be able to SSH into the Fedora machine utilizing SSH key authentication, it is time to configure SSH to make use of two-factor authentication. From the terminal window (on the Fedora machine), difficulty the command:

sudo nano /and so on/pam.d/sshd

Remark out the primary line (by including a # symbole firstly). That line will now appear like:

#auth substack password-auth

On the backside of the file, add the next line:

auth ample pam_google_authenticator.so

Save and shut that file.

Subsequent, we have to configure the SSH daemon. Situation the command:

sudo nano /and so on/ssh/sshd_config

First, change the ChallengeResponseAuthentication from no to sure like so:

ChallengeResponseAuthentication sure

Subsequent, change PasswordAuthentication to no like so:

PasswordAuthentication no

Lastly, add the next to the underside of that file:

AuthenticationMethods publickey,password publickey,keyboard-interactive

Save and shut the file.

Restart the SSH daemon with the command:

sudo systemctl restart sshd

Logging in

You might be able to log in. From one in every of your consumer machines, open a terminal window and difficulty the command:

ssh [email protected]_IP

The place USER is the username on the Fedora machine and FEDORA_IP is the IP tackle of the Fedora machine. You ought to be prompted for a Verification code (Determine A), which you’ll retrieve out of your cell authentication app.

Figure AFigure A

Determine A: Our SSH immediate for the verification code.

When you enter the code, you need to obtain entry to the machine (since you arrange SSH key authentication).

Congratulations, you now have two-factor authentication arrange in your Fedora machine. Anytime somebody makes an attempt to log into that server or desktop utilizing SSH they will not be given entry and not using a two-factor authentication code generated by your cell authentication app.

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