screenshot: Extend ScreenshotArea parameter validation

We currently only ensure that width and height are positive, so it
is still possible to pass in values that don't make any sense at all
(which may even result in a crash when exceeding limits imposed by
X11).
There is nothing to screenshot outside the actual screen area, so
restrict the parameters to that.

https://bugzilla.gnome.org/show_bug.cgi?id=699752

diff --git a/js/ui/screenshot.js b/js/ui/screenshot.js
index 10435c5b8a8a44bf2c0b30d168344bacb45c8b00..73ca773a910ef311dc5a14f28ef4318679595735 100644 (file)
--- a/js/ui/screenshot.js
+++ b/js/ui/screenshot.js
@@ -79,7 +79,9 @@ const ScreenshotService = new Lang.Class({
 
     ScreenshotAreaAsync : function (params, invocation) {
         let [x, y, width, height, flash, filename, callback] = params;
-        if (height <= 0 || width <= 0) {
+        if (x < 0 || y < 0 ||
+            width <= 0 || height <= 0 ||
+            x + width > global.screen_width || y + height > global.screen_height) {
             invocation.return_error_literal(Gio.IOErrorEnum, Gio.IOErrorEnum.CANCELLED,
                         "Invalid params");
             return;