Merge pull request #6402 from radarhere/gif_decompression_bomb

Added GIF decompression bomb check

Author: radarhere

Tests/images/decompression_bomb_extents.gif

@@ -61,6 +61,11 @@ def test_exception_gif(self):
             with Image.open("Tests/images/decompression_bomb.gif"):
                 pass
 
+    def test_exception_gif_extents(self):
+        with Image.open("Tests/images/decompression_bomb_extents.gif") as im:
+            with pytest.raises(Image.DecompressionBombError):
+                im.seek(1)
+
     def test_exception_bmp(self):
         with pytest.raises(Image.DecompressionBombError):
             with Image.open("Tests/images/bmp/b/reallybig.bmp"):

Tests/test_decompression_bomb.py

@@ -265,6 +265,7 @@ def _seek(self, frame, update_image=True):
                 x1, y1 = x0 + i16(s, 4), y0 + i16(s, 6)
                 if (x1 > self.size[0] or y1 > self.size[1]) and update_image:
                     self._size = max(x1, self.size[0]), max(y1, self.size[1])
+                    Image._decompression_bomb_check(self._size)
                 frame_dispose_extent = x0, y0, x1, y1
                 flags = s[8]