16.7. Nagios in a MAC Jail

This section demonstrates the steps that are needed to implement the Nagios network monitoring system in a MAC environment. This is meant as an example which still requires the administrator to test that the implemented policy meets the security requirements of the network before using in a production environment.

This example requires multilabel to be set on each file system. It also assumes that net-mgmt/nagios-plugins, net-mgmt/nagios, and www/apache22 are all installed, configured, and working correctly before attempting the integration into the MAC framework.

16.7.1. Create an Insecure User Class

Begin the procedure by adding the following user class to /etc/login.conf:

:manpath=/usr/share/man /usr/local/man:\

Then, add the following line to the default user class section:


Save the edits and issue the following command to rebuild the database:

# cap_mkdb /etc/login.conf

16.7.2. Configure Users

Set the root user to the default class using:

# pw usermod root -L default

All user accounts that are not root will now require a login class. The login class is required, otherwise users will be refused access to common commands. The following sh script should do the trick:

# for x in `awk -F: '($3 >= 1001) && ($3 != 65534) { print $1 }' \
	/etc/passwd`; do pw usermod $x -L default; done;

Next, drop the nagios and www accounts into the insecure class:

# pw usermod nagios -L insecure
# pw usermod www -L insecure

16.7.3. Create the Contexts File

A contexts file should now be created as /etc/policy.contexts:

# This is the default BIBA policy for this system.

# System:
/var/run(/.*)?			biba/equal

/dev/(/.*)?			biba/equal

/var				biba/equal
/var/spool(/.*)?		biba/equal

/var/log(/.*)?			biba/equal

/tmp(/.*)?			biba/equal
/var/tmp(/.*)?			biba/equal

/var/spool/mqueue		biba/equal
/var/spool/clientmqueue		biba/equal

# For Nagios:
/usr/local/etc/nagios(/.*)?	biba/10

/var/spool/nagios(/.*)?		biba/10

# For apache
/usr/local/etc/apache(/.*)?	biba/10

This policy enforces security by setting restrictions on the flow of information. In this specific configuration, users, including root, should never be allowed to access Nagios. Configuration files and processes that are a part of Nagios will be completely self contained or jailed.

This file will be read after running setfsmac on every file system. This example sets the policy on the root file system:

# setfsmac -ef /etc/policy.contexts /

Next, add these edits to the main section of /etc/mac.conf:

default_labels file ?biba
default_labels ifnet ?biba
default_labels process ?biba
default_labels socket ?biba

16.7.4. Loader Configuration

To finish the configuration, add the following lines to /boot/loader.conf:


And the following line to the network card configuration stored in /etc/rc.conf. If the primary network configuration is done via DHCP, this may need to be configured manually after every system boot:

maclabel biba/equal

16.7.5. Testing the Configuration

First, ensure that the web server and Nagios will not be started on system initialization and reboot. Ensure that root cannot access any of the files in the Nagios configuration directory. If root can list the contents of /var/spool/nagios, something is wrong. Instead, a permission denied error should be returned.

If all seems well, Nagios, Apache, and Sendmail can now be started:

# cd /etc/mail && make stop && \
setpmac biba/equal make start && setpmac biba/10\(10-10\) apachectl start && \
setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestart

Double check to ensure that everything is working properly. If not, check the log files for error messages. If needed, use sysctl(8) to disable the mac_biba(4) security policy module and try starting everything again as usual.


The root user can still change the security enforcement and edit its configuration files. The following command will permit the degradation of the security policy to a lower grade for a newly spawned shell:

# setpmac biba/10 csh

To block this from happening, force the user into a range using login.conf(5). If setpmac(8) attempts to run a command outside of the compartment's range, an error will be returned and the command will not be executed. In this case, set root to biba/high(high-high).

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