Re: [PATCH BlueZ] gdbus: Properly set owner of filter data at start of client creation

[Sonny Sasaka <sonnysasaka@gmail.com>]

Hi Luiz,

On Sun, Sep 15, 2019 at 10:14 AM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> Hi Sonny,
>
> On Sat, Sep 14, 2019 at 5:57 PM Sonny Sasaka <sonnysasaka@gmail.com> wrote:
> >
> > Currently at the start of client creation (g_dbus_client_new), the
> > |owner| in |filter_data| is not set until the |name| is resolved. This
> > creates a time window where the filter doesn't work properly, i.e. it
> > filters in more than it should. To solve this issue, this patch does the
> > following:
> > 1. At the start of client creation, set the |owner| in |filter_data|
> > based on the current resolved |name| if any, or set it explicitly to
> > unknown (empty string) as opposed to NULL otherwise. The unknown |owner|
> > lets the filter reject any message, unlike NULL |owner| which accepts
> > any message.
> > 2. Step 1 above reveals another bug: message_filter fails to accept
> > messages which have |sender| set directly to D-Bus service name rather
> > than D-Bus address. Therefore this patch relaxes the filter requirement
> > in message_filter to accept a message if its |sender| is equal directly
> > to our filter's |name|.
> > 3. After the initial service name resolution (after GetNameOwner)
> > returns, immediately update our name cache with the result, otherwise
> > the filters' |owner| would be stuck to unknown (empty string) until
> > "NameOwnerChanged" signal arrives.
> >
> > ---
> >  gdbus/watch.c | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/gdbus/watch.c b/gdbus/watch.c
> > index 447e48671..2ae0fd5a7 100644
> > --- a/gdbus/watch.c
> > +++ b/gdbus/watch.c
> > @@ -78,6 +78,8 @@ struct filter_data {
> >         gboolean registered;
> >  };
> >
> > +static const char *check_name_cache(const char *name);
> > +
> >  static struct filter_data *filter_data_find_match(DBusConnection *connection,
> >                                                         const char *name,
> >                                                         const char *owner,
> > @@ -265,7 +267,10 @@ proceed:
> >
> >         data->connection = dbus_connection_ref(connection);
> >         data->name = g_strdup(name);
> > -       data->owner = g_strdup(owner);
> > +       if (name)
> > +               data->owner = g_strdup(check_name_cache(name) ? : "");
>
> I follow this it would ignore the owner address and use the cache name
> or set "" to be resolved shouldn't that use the owner instead? If the
> called don't have it resolved then it should optionally set the owner
> resolution.
if |name| is set, |owner| must be NULL (refer to if block before
proceed: label above).

>
> > +       else
> > +               data->owner = g_strdup(owner);
> >         data->path = g_strdup(path);
> >         data->interface = g_strdup(interface);
> >         data->member = g_strdup(member);
> > @@ -534,8 +539,12 @@ static DBusHandlerResult
> > message_filter(DBusConnection *connection,
> >                 if (!sender && data->owner)
> >                         continue;
> >
> > -               if (data->owner && g_str_equal(sender, data->owner) == FALSE)
> > +               if (data->owner &&
> > +                               g_str_equal(sender, data->owner) == FALSE &&
> > +                               data->name &&
> > +                               g_str_equal(sender, data->name) == FALSE) {
>
> iirc messages never use the friendly name only the bus connection as
> sender so I wonder if this really does make any difference, are there
> any example of this not working? Perhaps it would be worth creating a
> test case in unit/test-gdbus.c to capture this case.
There is a case where the sender is D-Bus daemon itself. For example
NameOwnerChanged signal is sent via a message which has
sender="org.freedesktop.dbus" instead of a D-Bus address. I am not
aware of any other case other than messages sent by D-Bus daemon.
>
> >                         continue;
> > +               }
> >
> >                 if (data->path && g_str_equal(path, data->path) == FALSE)
> >                         continue;
> > @@ -627,6 +636,7 @@ static void service_reply(DBusPendingCall *call,
> > void *user_data)
> >                                                 DBUS_TYPE_INVALID) == FALSE)
> >                 goto fail;
> >
> > +       update_name_cache(data->name, data->owner);
> >         update_service(data);
> >
> >         goto done;
> > --
> > 2.21.0
>
>
>
> --
> Luiz Augusto von Dentz