Linux Networking Cookbook

7.3. Setting Up Host Keys for Simplest Authentication

Problem

You want to know how to set up OpenSSH to log in to a remote host, using the simplest method that it supports.

Solution

Using host-key authentication is the simplest way to set up remote SSH access. You need:

• OpenSSH installed on the machine you want to log into remotely

• The SSH daemon to be running on the remote server, and port 22 not blocked

• SSH client software on the remote client

• A Linux login account on the remote server

• To distribute the public host key to the clients

Your OpenSSH installer should have already created the host keys. If it didn't, see the next recipe.

First, protect your private host key from accidental overwrites:

	# chmod 400 /etc/ssh/ssh_host_rsa_key

Next, the public host key must be distributed to the clients. One way is to log in from the client, and let OpenSSH transfer the key:

	foober@gouda:~$ ssh reggiano
	The authenticity of host 'reggiano (192.168.1.10)' can't be established.
	RSA key fingerprint is 26:f6:5b:24:49:e6:71:6f:12:76:1c:2b:a5:ee:fe:fe
	Are you sure you want to continue connecting (yes/no)?
	Warning: Permanently added 'reggiano 192.168.1.10' (RSA) to the list of known hosts.
	foober@reggiano's password:
	Linux reggiano 2.6.15 #1 Sun June 10 11:03:21 PDT 2007 i686 GNU/Linux
	Debian GNU/Linux
	Last login: S Sun June 10 03:11:49 PDT 2007 from :0.0
	foober@reggiano:~$

Now, Foober can work on Reggiano just as if he were physically sitting at the machine, and all traffic—including the initial login—is ...