Don't crash when asked to verify a badly encoded domain or selector.

dkim/tests/test_dkim.py

@@ -42,7 +42,7 @@ class TestFold(unittest.TestCase):
         # The function is terribly broken, not passing even this simple
         # test.
         self.assertEqual(
-            b"foo"*24 + b"\r\n foo", dkim.fold(b"foo" * 25))
+            b"foo" * 24 + b"\r\n foo", dkim.fold(b"foo" * 25))
 
 
 class TestSignAndVerify(unittest.TestCase):
@@ -68,6 +68,12 @@ class TestSignAndVerify(unittest.TestCase):
         res = dkim.verify(sig + self.message + b"foo", dnsfunc=self.dnsfunc)
         self.assertFalse(res)
 
+    def test_badly_encoded_domain_fails(self):
+        # Domains should be ASCII. Bad ASCII causes verification to fail.
+        sig = dkim.sign(self.message, b"test", b"example.com\xe9", self.key)
+        res = dkim.verify(sig + self.message, dnsfunc=self.dnsfunc)
+        self.assertFalse(res)
+
 
 def test_suite():
     from unittest import TestLoader