Jun 09, 2018 Most Linux and Unix distribution create ssh keys for you during the installation of the OpenSSH server package. But it may be useful to be able re-generate new server keys from time to time. For example, when you duplicate VM (KVM or container) which contains an installed ssh package and you need to use different keys from cloned KVM VM guest/machine. Passwordless SSH involves both generating SSH key pair without a passphrase on the client side and authenticating against the server using client public key instead of the password for the user on the server side. Passwordless SSH Setup on Ubuntu. To demonstrate passwordless SSH authentication, we will run a small testbed on Digital Ocean. Add SSH Keys in Ubuntu 16.04. The following steps showed the step by step installation guideline. Set up your default identity. From the terminal, enter ssh-keygen at the command line. The command prompts you for a file to save the key in: ssh-keygen It will create two files; one public key file and one private key file. Both file will have your given name. Step 1: Generate a SSH Key Pair. If you’re using another Linux computer to connect to the server, then generaing SSH key pair and exporting it to the server should be a bit easier than a non Linux host To generate a SSH key pair, run the commands below from the Linux client machine. Oct 06, 2017  This article shows how to configure a SSH connection for authentication by using the public-key method. To do this, a key pair is created at the client, the public part of the key is transferred to the server, and afterwards the server is set up for key authentication. The user can log on to the server without a login password, only the password is required to protect the private key. Apr 28, 2018  With Bash on Ubuntu on Windows, you can use a Windows Subsystem for Linux on Windows 10. With that, you can run many Linux commands, for example, ssh.This post shows you how to create an SSH key, which should be used on both, the Linux subsystem and Windows. Sep 23, 2019  Operating System: Ubuntu 16.04 LTS (64-bit) Add SSH Keys in Ubuntu 16.04. The following steps showed the step by step installation guideline. Set up your default identity. From the terminal, enter ssh-keygen at the command line. The command prompts you for a file to save the key in: ssh.

• Generate Ssh Key Github
• Ubuntu Generate Ssh Key Pair

This article shows how to configure a SSH connection for authentication by using the public-key method. To do this, a key pair is created at the client, the public part of the key is transferred to the server, and afterwards the server is set up for key authentication. The user can log on to the server without a login password, only the password is required to protect the private key.The operating systems used in this article are on the one hand a Ubuntu 12.10 at the client side and a Ubuntu 12.04 at the server side.This guide was also validated working with Ubuntu 16.04 as client and server.

• 1On the client
• 2On the server
• 3Notes for other distributions

On the client

The first configuration steps take place at the client side.

Home folder rights

By default, Ubuntu sets the user home directory permissions to 755. Nevertheless, for security reasons, check whether the permissions are set to 755 on your system and change them if necessary: Use openssl to generate dkim key.

:~$ sudo chmod 755 /home/<USER>

Generate keypair

In the first step, a key pair with ssh-keygen is created at the client. If you use Ubuntu 18.04 on the server, the package openssh-server will be installed in the version 7.6.^[1] Since this version, RSA bit lengths smaller than 1024 bits are no longer accepted.^[2] In this example, a bit length of 4096 bits is selected for the RSA keys:

Please note: It is recommended to protect the key with a passphrase for security reasons. This means that the key is not available in plain text, but is AES-CBC encrypted:

If the private key is stolen by an attacker, he has to find out the password of the key in order to access the server with the key. If the key is available in plain text, an attacker can use this stolen key to directly access the server.

Transfer the public key to the server

To transfer the public key to the server, the first step is to use the SSH connection via password authentication yet. The ssh-copy-id tool copies the corresponding identity file to the server:

Generate Ssh Key Github

The above-mentioned procedure has created the following entry in the /home/tktest/.ssh/authorized_keyson the server:

Test the key authentication

/bitcoin-public-and-private-key-generator.html. Now that the public key is transferred to the server, the connection can be tested from the client. In this case, it is important that the server does not ask for the user password, but of course the passphrase of the protected key is required!

The following dialog box appears for GUI-based systems:

After entering the password that protected the key when it was created, you are authenticated on the system:

On the server

This paragraph shows some additional configuration steps on the server side to harden the public-key authentication.

sshd configuration

In Ubuntu, it is generally sufficient to carry out the above-mentioned procedure for public-key authentication. In some situations it makes sense to deactivate password authentication completely.

Please note: After changing the following setting, it is no longer possible to log in with a password via ssh: PasswordAuthentication no.

From the client, the connection is tested again:

In the above example, the dialog for entering the key password has been aborted. Since the log-on via password was deactivated, it was not possible to log-on to the system.

Forbid password authentication for just one user

Another way in which password authentication is not completely deactivated is to disable password authentication for specific users. This allows a user who does not have sudo privileges to log on to the server, for example. To gain root privileges, at least one additional password must be found for a user with sudo privileges. Plus, there's a way to completely exclude users from ssh:

This example:

• Prohibits SSH access for the user test
• Deactivates password authentication for the user tktest
• Password authentication is retained for all other users

Notes for other distributions

For other Linux distributions, the required steps may differ slightly. We would be happy to supplement our experiences with other distributions, which you are welcome to share with us via the feedback function.

Red Hat

One reader told us that the procedure described Red Hat does not work 1:1 in Red Hat. In the home directory of the user, the write permission was set for the group. After a chmod 755 it worked to connect via ssh to the server without asking for a password.

References

1. ↑Package: openssh-server (1:7.6p1-4) (packages.ubuntu.com)
2. ↑OpenSSH 7.6 Release Notes (openssh.com)

Ubuntu Generate Ssh Key Pair