parse XML configuration files

[jokeyrhyme]

based on reading https://dbus.freedesktop.org/doc/dbus-daemon.1.html#configuration_file

Fixes #78 and #79 and #148

Related to #23 and #146

• hardcode <limit> parts per Hardcoded security limits #148
• emit warnings for <policy> parts that we don't implement per Implement essential policy #79
• emit warnings for <policy> parts that even dbus-broker doesn't implement: feat: initial work on supporting dbus-daemon XML configuration files #146 (comment)
• <type>
• <user>
• <fork>
• <keep_umask>
• <syslog>
• <pidfile>
• <allow_anonymous>
• <listen>
• <auth>
• <servicedir>
• <include>
• <includedir>
• <standard_session_servicedirs />
• all XDG_...-related entries for <standard_session_servicedirs />
• <standard_system_servicedirs />
• all entries for <standard_system_servicedirs />
• <policy>
• <allow> and all supported attributes
• <deny> and all supported attributes
• version real .conf files and tests against them: parse XML configuration files #159 (comment)
• read and test against real files from the system if they exist (Linux only?): parse XML configuration files #159 (comment)
• <(allow|deny) send_member=... : Implement essential policy #79 (comment)
• --config
• --system and --session

TODOs for follow-up PRs:

• <selinux>
• <associate>
• <apparmor>
• protect against circular <include> / <includedirs>
• <include if_selinux_enabled=...>
• <include selinux_root_relative=...>
• <listen> better than String values (e.g. parse and validate into more useful type)
• <auth> better than String, is there an enum of specific values we support
• validate/warn when using < standard_session_servicedirs /> in a system config
• validate/warn when using <standard_system_servicedirs /> in a session config
• validate DOCTYPE
• validate root element is <busconfig>
• implement Ord / PartialOrd trait for Policy to facilitate use during evaluation
• provide default XML configuration files

[zeenix]

Mostly have nitpicks but overall it looks pretty good already. Let's try and get it merged soon.

[jokeyrhyme]

As mentioned over on Matrix, I propose that we tackle AppArmor/SELinux support in a follow-up PR

Aside from that, I believe we've got a mostly-complete implementation of the XML configuration format, although we don't handle all the same error cases as in #23 or #146

[zeenix]

As mentioned over on Matrix, I propose that we tackle AppArmor/SELinux support in a follow-up PR

Sure thing.

Aside from that, I believe we've got a mostly-complete implementation of the XML configuration format

Awesome! I'll have a look soon.

although we don't handle all the same error cases as in #23 or #146

That's ok, we can handle them later. If you could list them here, that would be great though, just to ensure that we don't end up leaving something very important/critical.

Also do we add tests to parse system and session configuration from /usr/share/dbus-1/system.conf and /usr/share/dbus-1/session.conf? I think we should and make it linux-specific.

[jokeyrhyme]

Also do we add tests to parse system and session configuration from /usr/share/dbus-1/system.conf and /usr/share/dbus-1/session.conf? I think we should and make it linux-specific.

Do you mean I should copy the default configuration files from dbus-broker in as tests? Or should busd try to read these files by default if run with --session or --system ?

[zeenix]

Also do we add tests to parse system and session configuration from /usr/share/dbus-1/system.conf and /usr/share/dbus-1/session.conf? I think we should and make it linux-specific.

Do you mean I should copy the default configuration files from dbus-broker in as tests? Or should busd try to read these files by default if run with --session or --system ?

So busd should most definitely read them from those paths and later when we've some build configuration (#77), we can make the paths configurable at build time too. I was saying we should have tests that also try to load from those paths on Linux but we can also copy them into the repo to keep the tests self-contained (then the tests don't need to be linux-only).

[jokeyrhyme]

I've updated the TODO checklist in the PR description

[jokeyrhyme]

test config_read_file_with_includes_ok ... FAILED

Weird, this passed on my machine, I'll have to take a look

[zeenix]

As I wrote on the matrix channel:

• This PR now breaks busd on launch. We need to add handling of tmpdir already (could be done in a separate PR first that this PR can be rebased on after that's merged).
• It probably makes sense at this point to just merge most commits in this branch.