x448 and x25519 should enforce key lengths in backend (#4703)

* x448 and x25519 should enforce key lengths in from_private_bytes

they should also check if the algorithm is supported like the public
bytes class methods do

* oops

* move the checks

1 files changed, 11 insertions, 1 deletions

diff --git a/tests/hazmat/primitives/test_x448.py b/tests/hazmat/primitives/test_x448.py
index 51be0e10..817de76f 100644
--- a/tests/hazmat/primitives/test_x448.py
+++ b/tests/hazmat/primitives/test_x448.py
@@ -28,7 +28,10 @@ from ...utils import (
 @pytest.mark.requires_backend_interface(interface=DHBackend)
 def test_x448_unsupported(backend):
     with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM):
-        X448PublicKey.from_public_bytes(b"0" * 32)
+        X448PublicKey.from_public_bytes(b"0" * 56)
+
+    with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM):
+        X448PrivateKey.from_private_bytes(b"0" * 56)
 
     with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM):
         X448PrivateKey.generate()
@@ -176,6 +179,13 @@ class TestX448Exchange(object):
         with pytest.raises(ValueError):
             X448PublicKey.from_public_bytes(b"a" * 57)
 
+    def test_invalid_length_from_private_bytes(self, backend):
+        with pytest.raises(ValueError):
+            X448PrivateKey.from_private_bytes(b"a" * 55)
+
+        with pytest.raises(ValueError):
+            X448PrivateKey.from_private_bytes(b"a" * 57)
+
     def test_invalid_private_bytes(self, backend):
         key = X448PrivateKey.generate()
         with pytest.raises(ValueError):