![]() If the client system is running Linux or macOS, this is achieved using the ssh-keygen utility: # ssh-keygen Code language: plaintext ( plaintext ) The first step in setting up SSH key-based authentication is to generate the key pairs on the client system. # systemctl enable rvice Code language: plaintext ( plaintext ) SSH Key-based Authentication from Linux and macOS Clients If the SSH server is not already installed and running on the system, it can be added using the following commands: # apt install openssh-server The remainder of this chapter will outline these steps in greater detail for Linux, macOS, and Windows-based client operating systems. Disable password-based authentication on the server.There are four steps to setting up key-based SSH authentication, which can be summarized as follows: As an added layer of protection, therefore, the private key may also be encrypted and protected by a password which must be entered each time a connection is established to the server. It is important to protect the private key, since ownership of the key will allow anyone to log into the remote system. In the case of SSH key-based authentication, the private key is held by the host on which the SSH client is located, while the corresponding public key resides on the system on which the SSH server is running. In a public key encryption system, the public key is used to encrypt data that can only be decrypted by the owner of the private key. The concept of public key encryption was devised in 1975 by Whitfield Diffie and Martin Hellman and is based on the concept of using a pair of keys, one private and one public. SSH key-based authentication makes use of asymmetric public key encryption to add an extra layer of security to remote system access. Buy the full book now in eBook ($24.99) format. You are reading a sample chapter from Ubuntu 22.04 Essentials. This weakness can be addressed by implementing SSH key-based authentication. ![]() If a malicious party is able to identify the password for an account (either through guesswork, subterfuge, or a brute force attack), the system becomes vulnerable. The inherent weakness in a basic SSH implementation is that it depends entirely on the strength of the passwords assigned to the accounts on the system. ![]() All of the communications between client and server, including the password entered to gain access, are encrypted to prevent outside parties from intercepting the data. A user might, for example, use an SSH client running on a Linux, Windows, or macOS system to connect to the SSH server running on an Ubuntu system to gain access to a shell command-line prompt or to perform file transfers. As will be covered in “Ubuntu Remote Desktop Access with Vino”, SSH can also be used to provide a secure tunnel through which remote access to the GNOME desktop can be achieved over a network connection.Ī basic SSH configuration consists of a client (used on the computer establishing the connection) and a server (running on the system to which the connection is to be established). SSH is designed to allow secure remote access to systems for the purposes of gaining shell access and transferring files and data. ![]() This chapter will outline the steps to increase the security of an Ubuntu system by implementing key-based SSH authentication. This level of security is far from adequate and should be upgraded to SSH key-based authentication as soon as possible. When installed, SSH provides password-protected and encrypted access to the system for the root account and any other users added during the installation phase. When an Ubuntu system is first installed, it is not configured by default to allow remote command-line access via Secure Shell (SSH) connections.
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