D-Bus implementation on Linux is an example of an SELinux-aware application, acting as a user space object manager. Applications can register themselves on a bus and can send messages between applications through D-Bus. These messages can be controlled through the SELinux policy as well.
Before looking at the SELinux access controls related to message flows, it is important to focus on a D-Bus service and see how its authentication is done (and how messages are relayed in D-Bus) as this is reflected in the SELinux integration.
Go to /etc/dbus-1/system.d/ (which hosts the configuration files for D-Bus services) and take a look at a configuration file. For instance, the service configuration file for dnsmasq looks like the following:
<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN" "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>
<policy user="root">
<allow own="uk...