Well, it seems to be getting a “trend” for me, to integrate stuff into our Active Directory. Now that I know why, and how easy that is, I expect to add more stuff. The good thing about the integration is, that you only need to maintain a single source for authorization.

The bad thing about that is, that stuff becomes dependent on the Active Directory (we do have four domain controllers, so that should be fine).

Now, here’s the ssl-(only) apache2 configuration file for my vhost:

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<VirtualHost *:80>
  ## mod_core
  DocumentRoot "/usr/share/nagios"

  ServerName nagios.barfoo.org
  ServerAlias nagios3.barfoo.org
  ServerAdmin nagiosadmin@barfoo.org

  ## mod_rewrite
  RewriteEngine On
  RewriteRule ^/(.*)         https://nagios.barfoo.org/$1 [L,R]

</VirtualHost>

<VirtualHost *:443>

  ## mod_core
  DocumentRoot "/usr/share/nagios"

  ServerName nagios.barfoo.org
  ServerAdmin nagiosadmin@barfoo.org

  ScriptAlias /nagios/cgi-bin /usr/lib/nagios/cgi
  Alias /nagios /usr/share/nagios
  Alias /pnp /usr/share/nagios/html/pnp4nagios

  <DirectoryMatch "/usr/(share/nagios|lib/nagios/cgi)">
    AllowOverride None
    Order deny,allow
    Deny from all
    Allow from 10.0.0.
    Options None

    # Authorization
    AuthType Basic
    AuthName "Nagios Barfoo"

    # The authentification provider is mod_ldap
    AuthBasicProvider ldap

    # mod_ldap is our *only* authentification provider for this!
    AuthzLDAPAuthoritative on

    # Redirect the userfile requests to /dev/null
    AuthUserFile /dev/null

    # AD requires an authentication DN to access any records
    AuthLDAPBindDN "BARFOO\ldap_nagios"
    AuthLDAPBindPassword "somethingrandom"

    # The URL to search in
    AuthLDAPURL "ldap://dc0.barfoo.org dc1.barfoo.org dc2.barfoo.org dc3.barfoo.org/OU=Users,dc=barfoo,dc=org?sAMAccountName?sub?(objectClass=*)"

    # Search the group membership in the specified group, otherwise it's gonna
    # get searched at the binding DN's location
    AuthLDAPGroupAttributeIsDN on
    Require ldap-group CN=gr_nagios,OU=Groups,DC=barfoo,DC=org
  </DirectoryMatch>

  ## mod_log
  ErrorLog /var/log/apache2/nagios.barfoo.org.error_log
  TransferLog /var/log/apache2/nagios.barfoo.org.access_log
  CustomLog /var/log/apache2/nagios.barfoo.org.ssl_request_log   ssl_combined

  ## mod_ssl
  SSLEngine on
  SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL
  SSLCertificateFile /etc/apache2/ssl.crt/nagios.barfoo.org.crt
  SSLCertificateKeyFile /etc/apache2/ssl.key/nagios.barfoo.org.key

  <Files ~ ".(cgi|shtml|phtml|php3|php?)$">
    SSLOptions +StdEnvVars
  </Files>

  SetEnvIf User-Agent ".*MSIE.*"
    nokeepalive ssl-unclean-shutdown
    downgrade-1.0 force-response-1.0

</VirtualHost>

As you can see, AuthLDAPUrl holds the four LDAP servers separated by spaces (that’s what the Apache2 documentation says about that), and that actually works.

The only additional thing I had to change from the nagios part is in /etc/nagios/cgi.cfg to allow everyone to issue system commands. Also, if you ever stumble upon extraneous chars in the check_nrpe output, update to a newer NRPE version, that fixed it for me (that is on the receiver side - as in the box running the NRPE agent).