added decompression bomb check to crop

PIL/Image.py

@@ -1042,6 +1042,20 @@ class Image(object):
         if box is None:
             return self.copy()
 
+        return self._new(self._crop(self.im, box))
+
+    def _crop(self, im, box):
+        """
+        Returns a rectangular region from the core image object im.
+
+        This is equivalent to calling im.crop((x0, y0, x1, y1)), but
+        includes additional sanity checks.
+
+        :param im: a core image object
+        :param box: The crop rectangle, as a (left, upper, right, lower)-tuple.
+        :returns: A core image object.
+        """
+
         x0, y0, x1, y1 = map(int, map(round, box))
 
         if x0 == 0 and y0 == 0 and (x1, y1) == self.size:
@@ -1052,8 +1066,10 @@ class Image(object):
         if y1 < y0:
             y1 = y0
 
-        return self._new(self.im.crop((x0, y0, x1, y1)))
+        _decompression_bomb_check((x1, y1))
 
+        return im.crop((x0, y0, x1, y1))
+         
     def draft(self, mode, size):
         """
         Configures the image file loader so it returns a version of the

Tests/test_decompression_bomb.py

@@ -1,4 +1,4 @@
-from helper import unittest, PillowTestCase
+from helper import unittest, PillowTestCase, hopper
 
 from PIL import Image
 
@@ -35,9 +35,24 @@ class TestDecompressionBomb(PillowTestCase):
         self.assertEqual(Image.MAX_IMAGE_PIXELS, 10)
 
         # Act / Assert
-        self.assert_warning(
-            Image.DecompressionBombWarning,
-            lambda: Image.open(TEST_FILE))
+        self.assert_warning(Image.DecompressionBombWarning,
+                            lambda: Image.open(TEST_FILE))
+
+class TestDecompressionCrop(PillowTestCase):
+
+    def setUp(self):
+        self.src = hopper()
+        Image.MAX_IMAGE_PIXELS = self.src.height * self.src.width
+
+    def tearDown(self):
+        Image.MAX_IMAGE_PIXELS = ORIGINAL_LIMIT
+
+    def testEnlargeCrop(self):
+        # Crops can extend the extents, therefore we should have the
+        # same decompression bomb warnings on them.
+        box = (0, 0, self.src.width * 2, self.src.height * 2)
+        self.assert_warning(Image.DecompressionBombWarning,
+                            lambda: self.src.crop(box))    
 
 if __name__ == '__main__':
     unittest.main()