YubiKey for SSH, Login, 2FA, GPG and Git Signing. Generate an initial challenge file for each YubiKey (you bought at least 2, right?). Each YubiKey with an authentication gpg sub-key will produce a different public SSH key: we will need to seed our server with all the SSH public keys. Aug 19, 2019 An SSH Key enables a secure passwordless method of logging into a remote server. Learn how to generate SSH keys on CentOS 7. Oct 11, 2019  I don't know how you maintain your lists of ssh key mappings to users, nor how you add ssh keys to your /.ssh/authorizedkeys files, so I can't provide general advice. Mac client setup. People with Touchbar Macs should use TouchID to authenticate logins, as they'll have their laptop and their fingers with them anyways. Sekey lets us support this.

Mar 08, 2017 To do this, open the crosh shell by pressing Ctrl+Alt+T anywhere in Chrome OS. The shell will open in a browser tab. Next, use the appropriate ssh command to connect to an SSH server and establish a tunnel. You’ll do this by running the ssh command and then by typing every option on its own line, like so. Linux command: ssh-keygen - Generate SSH Keys ssh-keygen — authentication key generation, management and conversion $ ssh-keygen -t rsa -C 'your@email.address'. The Secure Shell app is different because it does not require a proxy or relay server to function. Secure Shell can make a direct connection to a standard sshd server on any port of the destination machine. Other web terminals require a proxy server in the middle. In some cases you are even required to hand the proxy your credentials in plain text.

Introduction

Secure Shell (SSH) is an encrypted protocol used by Linux users to connect to their remote servers.

Generally, there are two ways for clients to access their servers – using password based authentication or public key based authentication.

Using SSH keys for authentication is highly recommended, as a safer alternative to passwords.

This tutorial will guide you through the steps on how to generate and set up SSH keys on CentOS 7. We also cover connecting to a remote server using the keys and disabling password authentication.

1. Check for Existing Keys

Prior to any installation, it is wise to check whether there are any existing keys on the client machines.

Open the terminal and list all public keys stored with the following command:

The output informs you about any generated keys currently on the system. If there aren’t any, the message tells you it cannot access /.ssh/id_*.pub , as there is no such file or directory.

2. Verify SSH is Installed

To check if thw package is installed, run the command:

If you already have SSH, the output tells you which version it is running. Currently, the latest version is OpenSSH 8.0/8.0p1.

Note: Refer to our guide If you need to install and enable SSH on your CentOS system.

Steps to Creating SSH keys on CentOS

Step 1: Create SSH Key Pair

1. Start by logging into the source machine (local server) and creating a 2048-bit RSA key pair using the command:

If you want to tighten up security measures, you can create a 4096-bit key by adding the -b 4096 flag:

2. After entering the command, you should see the following prompt:

3. To save the file in the suggested directory, press Enter. Alternatively, you can specify another location.

Note: If you already have a key pair in the proposed location, it is advisable to pick another directory. Otherwise it will overwrite existing SSH keys.

4. Next, the prompt will continue with:

Although creating a passphrase isn’t mandatory, it is highly advisable.

5. Finally, the output will end by specifying the following information:

Now you need to add the public key to the remote CentOS server.

You can copy the public SSH key on the remote server using several different methods:

  1. using the ssh-copy-id script
  2. using Secure Copy (scp)
  3. manually copying the key

The fastest and easiest method is by utilizing ssh-copy-id. If the option is available, we recommend using it. Otherwise, try any of the other two noted.

1. Start by typing the following command, specifying the SSH user account, and the IP address of the remote host:

If it is the first time your local computer is accessing this specific remote server you will receive the following output:

2. Confirm the connection – type yes and hit Enter.

3. Once it locates the id_rsa.pub key created on the local machine, it will ask you to provide the password for the remote account. Type in the password and hit Enter.

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4. Once the connection has been established, it adds the public key on the remote server. This is done by copying the ~/.ssh/id_rsa.pub file to the remote server’s ~/.ssh directory. You can locate it under the name authorized_keys.

5. Lastly, the output tells you the number of keys added, along with clear instructions on what to do next:

1. First, set up an SSH connection with the remote user:

2. Next, create the ~/.ssh directory as well as the authorized_keys file:

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3. Use the chmod command to change the file permission:

chmod 700 makes the file executable, while chmod 600 allows the user to read and write the file.

4. Now, open a new terminal session, on the local computer.

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5. Copy the content from id_rsa.pub (the SSH public key) to the previously created authorized_keys file on the remote CentOS server by typing the command:

32 bit hex key generator. With this, the public key has been safely stored on the remote account.

1. To manually add the public SSH key to the remote machine, you first need to open the content from the ~/.ssh/id_rsa.pub file:

2. As in the image below, the key starts with ssh-rsa and ends with the username of the local computer and hostname of the remote machine:


3. Copy the content of the file, as you will need later.

4. Then, in the terminal window, connect to the remote server on which you wish to copy the public key. Use the following command to establish the connection:

5. Create a ~/.ssh directory and authorized_keys file on the CentOS server with the following command:

6. Change their file permission by typing:

7. Next, open the authorized_keys file with an editor of your preference. For example, to open it with Nano, type:

8. Add the public key, previously copied in step 2 of this section, in a new line in (under the existing content).

9. Save the changes and close the file.

10. Finally, log into the server to verify that everything is set up correctly.

Once you have completed the previous steps (creating an RSA Key Pair and copying the Public Key to the CentOS server), you will be able to connect to the remote host without typing the password for the remote account.

All you need to do is type in the following command:

If you didn’t specify a passphrase while creating the SSH key pair, you will automatically log in the remote server.

Otherwise, type in the passphrase you supplied in the initial steps and press Enter.

Once the shell confirms the key match, it will open a new session for direct communication with the server.

Although you managed to access the CentOS server without having to provide a password, it still has a password-based authentication system running on the machine. This makes it a potential target for brute force attacks.

You should disable password authentication entirely by following the outlined steps.

Note: Consider performing the following steps through a non-root account with sudo privileges, as an additional safety layer.

1. Using the SSH keys, log into the remote CentOS server which has administrative privileges:

Using SSH, one can connect to a remote host and gain a shell access on it in a secure manner as all traffic is encrypted.A neat feature of open SSH is to authenticate a user using a public/private key pair to log into the remote host. Ubuntu generate ssh key for another user. Secure your SSH server with Public/Private key authentification2 minute readis the most widely used SSH server on Linux.

2. Next, open the SSH daemon configuration file using a text editor of your choice:

3. Look for the following line in the file:

4. Edit the configuration by changing the yes value to no. Thus, the directive should be as following:

5. Save the file and exit the text editor.
6. To enable the changes, restart the sshdservice using the command:

7. Verify the SSH connection to the server is still functioning correctly. Open a new terminal window and type in the command:

In this article, you learned how to generate SSH key pairs and set up an SSH key-based authentication. We also covered copying keys to your remote CentOS server, and disabling SSH password authentication.

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Next, You Should Read:

For this exercise the client system is a Chromebook, and the server system is an Ubuntu VM running on Google Compute Engine.

The SSH client of choice on Chrome OS devices is Secure Shell. Per its own documentation, it is possible to use public key-based authentication with the Secure Shell client. However, Secure Shell cannot generate its own keys. My goal here is to be able to SSH into a Google Compute Engine VM running Ubuntu Linux, so I generated the keypair on the target Linux VM using the browser-based SSH client offered by https://console.cloud.google.com/, and then imported them into Secure Shell on my Chromebook. This is appealing because it avoids the need to configure passwords for SSH altogether.

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Security note: Generating the keypair on the target machine into which possession of that keypair authorizes access is reasonable. If an attacker already has a foothold in that system, you already lose. However, once that keypair is imported into Secure Shell on one’s client device, it can be convenient to use that key for access to other systems. Consider how much you trust the VM image where ssh-keygen executes before deciding whether to use the same keypair to authorize access to any other systems. Also consider the note about HTML5 filesystems being a relatively young technology in the above link to the Secure Shell documentation about SSH keys. A topic for another day is how to integrate with a physical hardware token like a Yubikey, so that the private SSH key is never exposed to any client device software.

This creates files gce-instance-ssh and gce-instance-ssh.pub. Both of these files need to be copied onto the Chromebook for importing into Secure Shell. I decided to do this using cat gce-instance-ssh and cat gce-instance-ssh.pub and then copy-pasting the contents of each. The destination was a Chrome extension that can create and edit plain text files. Secure Shell requires that both gce-instance-ssh and gce-instance-ssh.pub be available to import a keypair. I shift-clicked when selecting the files for the Import (to the right of the Identity: field in the Secure Shell connection dialog) dialog box. When selecting only the private key file, there seems to be little or no UI feedback that anything has happened at all.

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If successful, the drop-down next to Identity: will have a new entry, whose name appears to be the basename of the imported key files. In this case, gce-instance-ssh.