Linux Cookbook, 2nd Edition

Chapter 12. Secure Remote Access with OpenSSH

OpenSSH is the tool of choice for secure remote administration. It encrypts authentication and all traffic during a session, and guarantees the integrity of the data transfer. If something happens to alter your packets, SSH will tell you. In this chapter you will learn how to set up SSH access to remote hosts, manage your SSH encryption keys, configure logins to multiple remote hosts, customize your Bash prompt to show when it is an SSH session, and more good things.

OpenSSH supports a large number of strong encryption algorithms. All of them are unencumbered by patents because the OpenSSH team has gone to great lengths to ensure that no patented or otherwise encumbered code is inside OpenSSH. Recipe 12.16 shows how to print lists of all supported algorithms.

OpenSSH is a suite of remote transfer utilities:

• sshd, the OpenSSH server daemon.

• ssh, short for secure shell, though it doesn’t really include a shell, but provides a secure channel to the command shell on the remote system.

• scp, secure copy, for encrypted file transfer.

• sftp, Secure File Transfer Protocol, provides file access.

• ssh-copy-id, a nice little program for installing your public key to a remote SSH server’s authorized_keys file.

• ssh-keyscan, finds and collects public host keys on a network, saving you the trouble of hunting them down manually.

• ssh-keygen, generates and manages authentication keys.

• ssh-add, adds your identities to the authentication ...