Description: The ‘ssh-keyscan’ command is a command-line tool used to collect the SSH public keys of a remote host. This command is particularly useful for obtaining the keys of a server before establishing an SSH connection, allowing system administrators and users to verify the server’s identity and avoid ‘man-in-the-middle’ attacks. ‘ssh-keyscan’ can be used to obtain keys from various types of algorithms, such as RSA, DSA, ECDSA, and Ed25519, making it a versatile tool in SSH key management. Additionally, it allows for the collection of keys from multiple hosts at once, facilitating the management of environments with several servers. The command’s output can be redirected to a file, enabling its use in automation scripts and in the configuration of ‘known_hosts’ files. In summary, ‘ssh-keyscan’ is an essential utility for security in SSH connections, helping to establish a trust foundation between the client and the server.
History: The ‘ssh-keyscan’ command is part of the SSH toolkit that was developed in the mid-1990s when the SSH protocol was created by Tatu Ylönen in 1995. As the use of SSH expanded, additional tools became necessary to facilitate key management and security in connections. ‘ssh-keyscan’ was introduced as a solution to allow users and administrators to easily and quickly obtain the public keys of servers, contributing to the overall security of the protocol.
Uses: The ‘ssh-keyscan’ command is primarily used to collect the SSH public keys from one or more servers before establishing a connection. This is especially useful in environments where multiple servers are managed, as it allows administrators to efficiently add keys to their ‘known_hosts’ files. It is also used in automation scripts to configure environments, ensuring that the keys of servers are known and trusted before making SSH connections.
Examples: A practical example of using ‘ssh-keyscan’ would be running the command ‘ssh-keyscan example.com >> ~/.ssh/known_hosts’ to add the public key of the server ‘example.com’ to the user’s ‘known_hosts’ file. This ensures that, in future SSH connections to that server, the client can verify the server’s identity and avoid potential attacks. Another example would be using ‘ssh-keyscan -t rsa,dsa example.com’ to specify that only RSA and DSA type keys from the server are desired.
