***********
NSCA README
***********


Purpose
-------
The purpose of this addon is to allow you to send service check
results to a central monitoring server running Nagios in a secure
manner.


Contents
--------

There are two pieces to this addon:

  1) nsca       - This program runs as a daemon on the central server
                  that runs Nagios.  It listens for host and service
	          check results from remote machines (sent using the
		  send_nsca program described below).  Upon receiving
                  data from a remote client, the daemon will make a
                  *very* basic attempt at validating the data it has
                  received from the client.  This is done by decrypting
                  the data with the password stored in the nsca.cfg 
                  file.  If the decrypted data looks okay (i.e. it was
                  originally encrypted by the send_ncsa program using
                  the same password), the daemon will make entries in
                  the Nagios external command file telling Nagios
                  to process the host or service check result.  

		  Notes: The nsca daemon must have sufficient rights
                  to open the Nagios command file for writing.  Also,
		  Nagios will only process passive service check
                  results that it finds in the external command file
                  if the service has been defined in the host config
                  file (i.e. hosts.cfg) and it is being monitored.


  2) send_nsca  - This is the client program that is used to send
		  service check information from a remote machine to
                  the nsca daemon on the central machine that runs
                  Nagios.   Service check information is read from
                  the standard input in tab-delimited format as
		  follows:

			<host_name>[tab]<svc_description>[tab]<return_code>[tab]<plugin_output>[newline]

	          where:

			<host_name>=short name of host that the
                                    service is associated with
			<svc_description>=description of the service
			<return_code>=numeric return code
			<plugin_output>=output from service check

		  Host check information is submitted in a similiar
 		  fashion - just leave out the service description:

			<host_name>[tab]<return_code>[tab]<plugin_output>[newline]


Compiling
---------

The code is very basic and may not work on your particular
system without some tweaking.  I just haven't put a lot of effort
into this addon.  Most users should be able to compile
the daemon and client piece with the following commands...

./configure
make all

The binaries will be located in the src/ directory after you
run 'make all' and will have to be installed manually.



Installing
----------

The send_nsca program and associate config file (nsca.cfg) should
be placed on remote machines that you want to have communicate 
with the nsca daemon.  This means that you may have to compile the
send_nsca program on the remote machine, if its not the same
OS/architecture as that of the central server.

The nsca daemon and the configuration file (nsca.cfg) should
be placed somewhere on the central server running Nagios.

NOTES:  Make sure that you specify and use the same password in
        both the nsca.cfg and send_nsca.cfg files!  If you use a
        different password to encrypt the data than you do to
	decrypt it, the nsca daemon will reject the data you send
        it.



Security
--------

There are some security implications with allowing remote clients
to provide service check results to Nagios.  Because of this, you
have the option of encrypting the packets that the NSCA client sends
to the NSCA daemon.  Read the SECURITY file for more information on
the security risks of running NSCA, along with an explanation of what
kind of protection the encryption provides you.



Running Under INETD or XINETD
-----------------------------

If you plan on running nsca under inetd or xinetd and making use
of TCP wrappers, you need to do the following things:



1) Add a line to your /etc/services file as follows (modify the port
   number as you see fit)

	nsca            5667/tcp	# NSCA



2) Add entries for the NSCA daemon to either your inetd or xinetd
   configuration files.  Which one your use will depend on which
   superserver is installed on your system.  Both methods are described
   below.  NOTE: If you run nsca under inetd or xinetd, the server_port
   and allowed_hosts variables in the nrpe configuration file are
   ignored.


   ***** INETD *****
   If your system uses the inetd superserver WITH tcpwrappers, add an
   entry to /etc/inetd.conf as follows:

	nsca    stream  tcp     nowait  <user> /usr/sbin/tcpd <nscabin> -c <nscacfg> --inetd

   If your system uses the inetd superserver WITHOUT tcpwrappers, add an
   entry to /etc/inetd.conf as follows:

	nsca 	stream 	tcp 	nowait 	<user> <nscabin> -c <nscacfg> --inetd


   - Replace <user> with the name of the user that nsca server should run as.
	Example: nagios
   - Replace <nscabin> with the path to the nsca binary on your system.
	Example: /usr/local/nagios/nsca
   - Replace <nscacfg> with the path to the nsca config file on your system.
	Example: /usr/local/nagios/nsca.cfg


   ***** XINETD *****
   If your system uses xinetd instead of inetd, you'll probably
   want to create a file called 'nsca' in your /etc/xinetd.d
   directory that contains the following entries (a sample config
   file called nsca.xinetd should be created in the root folder of
   the distribution after you run the configure script):


	# default: on
	# description: NSCA
	service nsca
	{
        	flags           = REUSE
	        socket_type     = stream        
        	wait            = no
	        user            = <user>
		group		= <group>
        	server          = <nscabin>
	        server_args     = -c <nscacfg> --inetd
        	log_on_failure  += USERID
	        disable         = no
		only_from       = <ipaddress1> <ipaddress2> ...
	}


   - Replace <user> with the name of the user that the nsca server should run as.
   - Replace <group> with the name of the group that the nsca server should run as.
   - Replace <nscabin> with the path to the nsca binary on your system.
   - Replace <nscacfg> with the path to the nsca config file on your system.
   - Replace the <ipaddress> fields with the IP addresses of hosts which
     are allowed to connect to the NSCA daemon.  This only works if xinetd was
     compiled with support for tcpwrappers.



3) Restart inetd or xinetd will the following command (pick the
   one that is appropriate for your system:

	/etc/rc.d/init.d/inet restart

	/etc/rc.d/init.d/xinetd restart



4) Add entries to your /etc/hosts.allow and /etc/hosts.deny
   file to enable TCP wrapper protection for the nsca service.
   This is optional, although highly recommended.




Questions?
----------

If you have questions about this addon, or problems getting things
working, send me email.

	-- Ethan Galstad (nagios@nagios.org)




