Apply ImageFont.MAX_STRING_LENGTH to ImageFont.getmask()

Tests/test_imagefont.py

@@ -1058,6 +1058,8 @@ def test_too_many_characters(font):
         imagefont.getlength("A" * 1_000_001)
     with pytest.raises(ValueError):
         imagefont.getbbox("A" * 1_000_001)
+    with pytest.raises(ValueError):
+        imagefont.getmask("A" * 1_000_001)
 
 
 @pytest.mark.parametrize(

docs/releasenotes/10.2.0.rst

@@ -70,6 +70,18 @@ Restricted environment keys for ImageMath.eval
 arbitrary code. To prevent this, keys matching the names of builtins and keys
 containing double underscores will now raise a :py:exc:`ValueError`.
 
+Applied ImageFont.MAX_STRING_LENGTH to ImageFont.getmask
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+To protect against potential DOS attacks when using arbitrary strings as text
+input, Pillow will now raise a :py:exc:`ValueError` if the number of characters
+passed into :py:meth:`PIL.ImageFont.ImageFont.getmask` is over a certain limit,
+:py:data:`PIL.ImageFont.MAX_STRING_LENGTH`.
+
+This threshold can be changed by setting
+:py:data:`PIL.ImageFont.MAX_STRING_LENGTH`. It can be disabled by setting
+``ImageFont.MAX_STRING_LENGTH = None``.
+
 Other Changes
 =============
 

src/PIL/ImageFont.py

@@ -149,6 +149,7 @@ def getmask(self, text, mode="", *args, **kwargs):
         :return: An internal PIL storage memory instance as defined by the
                  :py:mod:`PIL.Image.core` interface module.
         """
+        _string_length_check(text)
         return self.font.getmask(text, mode)
 
     def getbbox(self, text, *args, **kwargs):