networkd: allow networkd to set the timezone in timedated

systemd-networkd runs as user "systemd-network" and thus is not privileged to
set the timezone acquired from DHCP:

  systemd-networkd[4167]: test_eth42: Could not set timezone: Interactive authentication required.

Similarly to commit e8c0de912, add a polkit rule to grant
org.freedesktop.timedate1.set-timezone to the "systemd-network" system user.
Move the polkit rules from src/hostname/ to src/network/ to avoid too many
small distributed policy snippets (there might be more in the future), as it's
easier to specify the privileges for a particular subject in this case.

Add NetworkdClientTest.test_dhcp_timezone() test case to verify this (for
all people except those in Pacific/Honolulu, there the test doesn't prove
anything -- sorry ☺ ).

1 files changed, 8 insertions, 0 deletions

diff --git a/src/network/systemd-networkd.rules b/src/network/systemd-networkd.rules
new file mode 100644
index 0000000000..2e4bc42bfb
--- /dev/null
+++ b/src/network/systemd-networkd.rules
@@ -0,0 +1,8 @@
+// Allow systemd-networkd to set timezone and transient hostname
+polkit.addRule(function(action, subject) {
+    if ((action.id == "org.freedesktop.hostname1.set-hostname" ||
+         action.id == "org.freedesktop.timedate1.set-timezone") &&
+        subject.user == "systemd-network") {
+        return polkit.Result.YES;
+    }
+});