Start with a default install. Add a configuration file to allow dbus monitoring as described here: https://wiki.ubuntu.com/DebuggingDBus Have dbus reload its configuration either by 'sudo reload dbus' or 'service messagebus reload'. After this the new setting should be in effect but it's not. To verify, do this: dbus-monitor --system (as root) Then as non-root use d-feet go to call e.g. NetworkManager /org/freedesktop/NetworkManager org.freedesktop.NetworkManager state(). This call should show up in the monitor dump but it does not. Only calls made by root processes show up. To get monitoring working you need to reboot.
I think the issue here is that the access control rules are cached per connection to the bus, so once NetworkManager has connected, its access control rules will be the same from then on. In principle dbus-daemon should recompute the access control rules that apply to existing connections when it is reloaded. I should note here (again) that the "see everything" configuration is actively dangerous, and may cause the intended access control rules for services to be bypassed: unfortunately the security policy language does not have a way to say "let root eavesdrop" without also saying "let everything send arbitrary messages to root processes like NetworkManager and systemd" (Bug #46787). I would be happy to review patches that added a way for privileged processes to eavesdrop on the bus without opening security flaws. Unfortunately, that mechanism does not currently exist.
(In reply to Simon McVittie from comment #1) > I would be happy to review patches that added a way for privileged processes > to eavesdrop on the bus without opening security flaws. Unfortunately, that > mechanism does not currently exist. Now it does! Bug #46787. This bug could still affect non-eavesdropping situations though.
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