events: fix parsing events with empty parameters

Empty parameter value is encoded as b'parameter\0\0', so we can't simply
read the data until b'\0\0', because it isn't necessary event end.
Instead, read event parts separately, according to specification.

qubesadmin/events/__init__.py

@@ -147,25 +147,32 @@ class EventsDispatcher(object):
             some_event_received = False
             while not reader.at_eof():
                 try:
-                    event_data = yield from reader.readuntil(b'\0\0')
+                    event_header = yield from reader.readuntil(b'\0')
-                    if event_data == b'1\0\0':
+                    if event_header != b'1\0':
-                        # event with non-VM subject contains \0\0 inside of
+                        raise qubesadmin.exc.QubesDaemonCommunicationError(
-                        # event, need to receive rest of the data
+                            'Non-event received on events connection: '
-                        event_data += yield from reader.readuntil(b'\0\0')
+                            + repr(event_header))
+                    subject = (yield from reader.readuntil(b'\0'))[:-1].decode(
+                        'utf-8')
+                    event = (yield from reader.readuntil(b'\0'))[:-1].decode(
+                        'utf-8')
+                    kwargs = {}
+                    while True:
+                        key = (yield from reader.readuntil(b'\0'))[:-1].decode(
+                            'utf-8')
+                        if not key:
+                            break
+                        value = (yield from reader.readuntil(b'\0'))[:-1].\
+                            decode('utf-8')
+                        kwargs[key] = value
                 except asyncio.IncompleteReadError as err:
                     if err.partial == b'':
                         break
                     else:
                         raise
 
-                if not event_data.startswith(b'1\0'):
+                if not subject:
-                    raise qubesadmin.exc.QubesDaemonCommunicationError(
+                    subject = None
-                        'Non-event received on events connection: '
-                        + repr(event_data))
-                event_data = event_data.decode('utf-8')
-                _, subject, event, *kwargs = event_data.split('\0')
-                # convert list to dict, remove last empty entry
-                kwargs = dict(zip(kwargs[:-2:2], kwargs[1:-2:2]))
                 self.handle(subject, event, **kwargs)
 
                 some_event_received = True

qubesadmin/tests/events.py

@@ -107,7 +107,7 @@ class TC_00_Events(qubesadmin.tests.QubesTestCase):
         events = [
             b'1\0\0some-event\0arg1\0value1\0\0',
             b'1\0some-vm\0some-event\0arg1\0value1\0\0',
-            b'1\0some-vm\0some-event\0\0',
+            b'1\0some-vm\0some-event\0arg_without_value\0\0arg2\0value\0\0',
             b'1\0some-vm\0other-event\0\0',
         ]
         asyncio.ensure_future(self.send_events(stream, events))
@@ -117,7 +117,9 @@ class TC_00_Events(qubesadmin.tests.QubesTestCase):
             unittest.mock.call(None, 'some-event', arg1='value1'),
             unittest.mock.call(
                 self.app.domains['some-vm'], 'some-event', arg1='value1'),
-            unittest.mock.call(self.app.domains['some-vm'], 'some-event'),
+            unittest.mock.call(
+                self.app.domains['some-vm'], 'some-event',
+                arg_without_value='', arg2='value'),
         ])
         cleanup_func.assert_called_once_with()
         loop.close()