bridge: Fix crash on invalid cockpit.conf

If there is a syntax error in cockpit.conf, the bridge previously
crashed with e.g. a `configparser.MissingSectionHeaderError`.

Intercept that, log a warning instead, and ignore the config file
instead.

https://bugzilla.redhat.com/show_bug.cgi?id=2324979

pkg/base1/test-dbus.js

@@ -524,6 +524,20 @@ Empty=
     assert.rejects(proxy.GetString("SomeSection", "UnknownKey"),
                    /key.*UnknownKey.*not exist/,
                    "unknown key raises an error");
+
+    // empty config
+    await cockpit.file(configDir + "/cockpit/cockpit.conf").replace("");
+    await proxy.Reload();
+    assert.rejects(proxy.GetString("SomeSection", "SomeA"),
+                   /key.*SomeSection.*not exist/,
+                   "query in empty config raises an error");
+
+    // broken config (missing section header)
+    await cockpit.file(configDir + "/cockpit/cockpit.conf").replace("SomeA = two");
+    await proxy.Reload();
+    assert.rejects(proxy.GetString("SomeSection", "SomeA"),
+                   /key.*SomeSection.*not exist/,
+                   "query in broken config raises an error");
 });
 
 QUnit.test("nonexisting address", async assert => {

src/cockpit/config.py

@@ -78,7 +78,12 @@ def reload(self):
         cockpit_conf = lookup_config('cockpit.conf')
         logger.debug("cockpit.Config: loading %s", cockpit_conf)
         # this may not exist, but it's ok to not have a config file and thus leave self.config empty
-        self.config.read(cockpit_conf)
+        try:
+            self.config.read(cockpit_conf)
+        except configparser.Error as exc:
+            logger.warning("cockpit.conf is invalid: %s", exc)
+            self.config.clear()
+            return
 
 
 class Environment(bus.Object, interface='cockpit.Environment'):

test/verify/check-connection

@@ -1209,6 +1209,21 @@ UnixPath=/run/cockpit/session
         self.login_and_go(None)
         b.wait_visible("#nav-system li:contains(Hackices)")
         self.assertFalse(b.is_present("#nav-system li:contains(Services)"))
+        b.logout()
+
+        # still starts with a broken config (no section headers)
+        m.write("/etc/test-xdg/cockpit/cockpit.conf", "LoginTitle=NoNoNO\n")
+        m.execute("systemctl stop cockpit")
+        self.login_and_go(None)
+        b.wait_visible("#nav-system li:contains(Hackices)")
+        self.assertFalse(b.is_present("#nav-system li:contains(Services)"))
+        b.logout()
+        # message from cockpit-ws
+        self.allow_journal_messages(".*cockpit.conf: key=val line not in any section.*")
+        # message from bridge
+        self.allow_journal_messages(".*cockpit.conf is invalid: File contains no section headers.*")
+        self.allow_journal_messages(".*cockpit.conf.*line: 1")
+        self.allow_journal_messages(".*LoginTitle=NoNoNO.*")
 
     @testlib.nondestructive
     @testlib.skipBeiboot("no cockpit-bridge binary on host in beiboot mode")