[PINENTRY PATCH] gnome3: Fall back to curses if screensaver is locked.

[Neal H. Walfield]

Thanks for working on this.  I've applied it with a small change,
which we discussed offline.

For the record, this doesn't detect if xscreensaver or something
similar is running and fall back to the curses interface, it only
works for GNOME screensaver.  But, it is reasonable to expect that
anyone who uses pinentry-gnome3 will be running GNOME screensaver and
not xscreensaver.

:) Neal

At Sun,  6 Nov 2016 02:17:04 -0500,
Daniel Kahn Gillmor wrote:
> 
> * gnome3/pinentry-gnome3.c (pe_gnome_screen_locked): New Function.
> Returns true only if we can talk to a GNOME screensaver over D-Bus and
> it assures us that it is locked.
> (main): If GNOME screensaver is locked, fall back to curses.
> 
> --
> 
> We assume that if pinentry is triggered while the screensaver is
> locked, then it is likely being done by some sort of remote connection
> (e.g. ssh), and isn't being done directly from the graphical console.
> In that case, prompting at the graphical console won't be able to get
> the attention of the user, so we should fall back to curses if
> possible.
> 
> GnuPG-bug-id: 2818
> ---
>  gnome3/pinentry-gnome3.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 69 insertions(+)
> 
> diff --git a/gnome3/pinentry-gnome3.c b/gnome3/pinentry-gnome3.c
> index ba6ab46..fd345a5 100644
> --- a/gnome3/pinentry-gnome3.c
> +++ b/gnome3/pinentry-gnome3.c
> @@ -390,6 +390,69 @@ pe_gcr_timeout_done (gpointer user_data)
>  
>  pinentry_cmd_handler_t pinentry_cmd_handler = gnome3_cmd_handler;
>  
> +/* Test whether there is a GNOME screensaver running that happens to
> + * be locked.  Note that if there is no GNOME screensaver running at
> + * all the answer is still FALSE */
> +static gboolean
> +pe_gnome_screen_locked (void)
> +{
> +  GDBusConnection *dbus;
> +  GError *error;
> +  GVariant *reply, *reply_bool;
> +  gboolean ret;
> +
> +  dbus = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, &error);
> +
> +  if (!dbus)
> +    {
> +      fprintf (stderr, "failed to connect to user session D-Bus (%d): %s",
> +               error ? error->code : -1,
> +               error ? error->message : "<no GError>");
> +      if (error)
> +        g_error_free (error);
> +      return FALSE;
> +    }
> +
> +  /* this is intended to be the equivalent of:
> +   * dbus-send --print-reply=literal --session          \
> +   *           --dest=org.gnome.ScreenSaver             \
> +   *           /org/gnome/ScreenSaver                   \
> +   *           org.gnome.ScreenSaver.GetActive
> +   */
> +  reply = g_dbus_connection_call_sync (dbus,
> +                                       "org.gnome.ScreenSaver",
> +                                       "/org/gnome/ScreenSaver",
> +                                       "org.gnome.ScreenSaver",
> +                                       "GetActive",
> +                                       NULL,
> +                                       ((const GVariantType *) "(b)"),
> +                                       G_DBUS_CALL_FLAGS_NO_AUTO_START,
> +                                       0,
> +                                       NULL,
> +                                       &error);
> +  g_object_unref(dbus);
> +  if (!reply)
> +    {
> +      fprintf (stderr, "failed to get reply (%d): %s",
> +               error ? error->code : -1,
> +               error ? error->message : "<no GError>");
> +      if (error)
> +        g_error_free (error);
> +      return FALSE;
> +    }
> +  reply_bool = g_variant_get_child_value (reply, 0);
> +  if (!reply_bool)
> +    {
> +      fprintf (stderr, "failed to get boolean from reply\n");
> +      ret = FALSE;
> +    }
> +  else
> +    ret = g_variant_get_boolean (reply_bool);
> +
> +  g_variant_unref (reply_bool);
> +  g_variant_unref (reply);
> +  return ret;
> +}
>  
>  /* Test whether we can create a system prompt or not.  This briefly
>   * does create a system prompt, which blocks other tools from making
> @@ -443,6 +506,12 @@ main (int argc, char *argv[])
>                 " falling back to curses\n");
>        pinentry_cmd_handler = curses_cmd_handler;
>      }
> +  else if (pe_gnome_screen_locked ())
> +    {
> +      fprintf (stderr, "GNOME screensaver is locked,"
> +               " falling back to curses\n");
> +      pinentry_cmd_handler = curses_cmd_handler;
> +    }
>  #endif
>  
>    pinentry_parse_opts (argc, argv);
> -- 
> 2.10.2
> 
> 
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