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.. -*- mode: rst -*-
.. _appendix-guides-authentication:
==============
Authentication
==============
Scenarios
=========
1. Cluster nodes that are frequently rebuilt
Default settings work well; machines do not float, and a per-client
password is not required.
2. :ref:`appendix-guides-nat_howto`
* Build client records in advance with ``bcfg2-admin``, setting a uuid
for each new client.
* Set the address attribute for each to the address of the NAT.
* Optionally, set a per-client password for each, and set into secure
mode.
.. note::
This will require the use of the uuid and password from each
client, and will require that they come through the NAT address.
Building bcfg2.conf automatically
=================================
This is a :ref:`Cheetah template
<server-plugins-generators-cfg-cheetah>` that automatically constructs
per-client bcfg2.conf from the per-client metadata::
[communication]
protocol = xmlrpc/ssl
#if $self.metadata.uuid != None
user = $self.metadata.uuid
#end if
#if $self.metadata.password != None
password = $self.metadata.password
#else
password = my-password-foobat
#end if
[components]
bcfg2 = https://localhost:6789
In this setup, this will cause any clients that have uuids established
to be set to use them in ``bcfg2.conf``. It will also cause any clients
with passwords set to use them instead of the global password.
How Authentication Works
========================
#. First, the client is associated with a client record. If the client
specifies a uuid, it uses this instead of the results of a dns or
address lookup.
#. Next, the ip address is verified against the client record. If the
address doesn't match, then the client must be set to
floating='true'
#. Finally, the password is verified. If the client is set to secure
mode, the only its per-client password is accepted. If it is not set
to secure mode, then either the global password or per-client password
will be accepted
Failure during any of these stages results in authentication
failure. Note that clients set into secure mode that do not have
per-client passwords set will not be able to connect.
SSL Cert-based client authentication
====================================
SSL-based client authentication is supported. This requires several
things:
#. Certificate Authority (to sign all keys)
#. Server key and cert signed by the CA
#. Client key and cert signed by the CA
A variety of CAs can be used, but these keys can be simply generated
using the following set of steps:
#. Setup a CA
http://www.flatmtn.com/article/setting-openssl-create-certificates
#. Create keys for each client and server, signing them with the CA
signing cert
http://www.flatmtn.com/article/setting-ssl-certificates-apache
.. note::
The client CN must be the FQDN of the client (as returned by a
reverse DNS lookup of the ip address. Otherwise, you will end up
with an error message on the client that looks like::
Server failure: Protocol Error: 401 Unauthorized
Failed to download probes from bcfg2
Server Failure
You will also see an error message on the server that looks
something like::
cmssrv01 bcfg2-server[9785]: Got request for cmssrv115 from incorrect address 131.225.206.122
cmssrv01 bcfg2-server[9785]: Resolved to cmssrv115.fnal.gov
#. Distribute the keys and certs to the appropriate locations
#. Copy the ca cert to clients, so that the server can be authenticated
Clients authenticating themselves with a certificate will be
authenticated that way first; clients can be setup to either
authenticate solely with certs, use certs with a fallback to password,
or password only. Also a bootstrap mode will be added shortly; this
will allow a client to authenticate with a password its first time,
requiring a certificate all subsequent times. This behavior can be
controlled through the use of the auth attribute in
``Metadata/clients.xml``::
<Clients>
<Client name='testclient' auth='cert'/>
</Clients>
Allowed values are:
+-------------------+------------------------------------------+
| Auth Type | Meaning |
+===================+==========================================+
| ``cert`` | Certificates must be used |
+-------------------+------------------------------------------+
| ``cert+password`` | Certificate or password may be used. If |
| | a certificate is used, the password must |
| | also be used. |
+-------------------+------------------------------------------+
| ``bootstrap`` | Password can be used for one client run, |
| | after that only certificate is allowed |
+-------------------+------------------------------------------+
``cert+password`` is the default. This can be changed by setting the
``authentication`` parameter in the ``[communication]`` section of
``bcfg2.conf``. For instance, to set ``bootstrap`` mode as the global
default, you would add the following to ``bcfg2.conf``::
[communication]
authentication = bootstrap
``bootstrap`` mode is currently incompatible with the
:ref:`server-plugins-grouping-metadata-clients-database`.
|
