Configure OpenSSH to use TCP-Wrappers/inetd super server

Securing and Optimizing Linux: RedHat Edition -A Hands on Guide
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# 15.5. Configure OpenSSH to use TCP-Wrappers/inetd super server

Tcp-Wrappers should be enabled to start and stop our OpenSSH server. Upon execution, inetd reads its configuration information from a configuration file which, by default, is `/etc/inetd.conf`. There must be an entry for each field of the configuration file, with entries for each field separated by a tab or a space.

1. Edit the `inetd.conf` file vi `/etc/inetd.conf` and add the line:

                 ssh	stream	tcp	nowait	root	/usr/sbin/tcpd	sshd -i

   > : The -i parameter is important since it's specifies that sshd is being run from inetd. Also, update your `inetd.conf` file by sending a SIGHUP signal killall`-HUP inetd` after adding the above line to the file.

   To update your `inetd.conf file`, use the following command:

                 [root@deep] /#killall -HUP inetd

2. Edit the `hosts.allow` file, vi `/etc/hosts.allow` and add the line:

                 sshd: 192.168.1.4 win.openna.com

   Which mean client IP `192.168.1.4` with host name `win.openna.com` is allowed to ssh in to the server.

These daemon strings for tcp-wrappers are in use by sshd:

sshdfwd-X11

  if you want to allow/deny X11-forwarding

sshdfwd-<port-number>

  for tcp-forwarding

sshdfwd-<port-name>

  port-name defined in `/etc/services`. Used in tcp-forwarding

> : If you do decide to switch to using ssh, make sure you install and use it on all your servers. Having ten secure servers and one insecure is a waste of time.

For more details, there are several man pages you can read:

ssh(1)

  OpenSSH secure shell client remote login program

ssh [slogin](1)

  OpenSSH secure shell client remote login program

ssh-add(1)

  adds identities for the authentication agent

ssh-agent(1)

  authentication agent

ssh-keygen(1)

  authentication key generation

sshd(8)

  secure shell daemon

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