support x448 public/private serialization both raw and pkcs8 (#4653)

* support x448 public/private serialization both raw and pkcs8

* add tests for all other asym key types to prevent Raw

* more tests

* better tests

* fix a test

* funny story, I'm actually illiterate.

* pep8

* require PrivateFormat.Raw or PublicFormat.Raw with Encoding.Raw

* missing docs

* parametrize

* docs fixes

* remove dupe line

* assert something

2 files changed, 106 insertions, 9 deletions

diff --git a/docs/hazmat/primitives/asymmetric/serialization.rst b/docs/hazmat/primitives/asymmetric/serialization.rst
index 7b3fb1d6..04bc705a 100644
--- a/docs/hazmat/primitives/asymmetric/serialization.rst
+++ b/docs/hazmat/primitives/asymmetric/serialization.rst
@@ -473,6 +473,13 @@ Serialization Formats
             ...
             -----END PRIVATE KEY-----
 
+    .. attribute:: Raw
+
+        .. versionadded:: 2.5
+
+        A raw format used by :doc:`/hazmat/primitives/asymmetric/x448`. It is a
+        binary format and is invalid for other key types.
+
 .. class:: PublicFormat
 
     .. versionadded:: 0.8
@@ -516,6 +523,13 @@ Serialization Formats
         The public key format used by OpenSSH (e.g. as found in
         ``~/.ssh/id_rsa.pub`` or ``~/.ssh/authorized_keys``).
 
+    .. attribute:: Raw
+
+        .. versionadded:: 2.5
+
+        A raw format used by :doc:`/hazmat/primitives/asymmetric/x448`. It is a
+        binary format and is invalid for other key types.
+
 .. class:: ParameterFormat
 
     .. versionadded:: 2.0
@@ -538,14 +552,16 @@ Serialization Encodings
     :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKeyWithSerialization`
     ,
     :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePrivateKeyWithSerialization`
-    , :class:`~cryptography.hazmat.primitives.asymmetric.dh.DHPrivateKeyWithSerialization`
+    , :class:`~cryptography.hazmat.primitives.asymmetric.dh.DHPrivateKeyWithSerialization`,
+    :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPrivateKeyWithSerialization`,
     and
-    :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPrivateKeyWithSerialization`
+    :class:`~cryptography.hazmat.primitives.asymmetric.x448.X448PrivateKey`
     as well as ``public_bytes`` on
-    :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKeyWithSerialization`,
-    :class:`~cryptography.hazmat.primitives.asymmetric.dh.DHPublicKeyWithSerialization`
+    :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey`,
+    :class:`~cryptography.hazmat.primitives.asymmetric.dh.DHPublicKey`,
+    :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey`,
     and
-    :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKeyWithSerialization`.
+    :class:`~cryptography.hazmat.primitives.asymmetric.x448.X448PublicKey`.
 
     .. attribute:: PEM
 
@@ -565,6 +581,13 @@ Serialization Encodings
 
         The format used by OpenSSH public keys. This is a text format.
 
+    .. attribute:: Raw
+
+        .. versionadded:: 2.5
+
+        A raw format used by :doc:`/hazmat/primitives/asymmetric/x448`. It is a
+        binary format and is invalid for other key types.
+
 
 Serialization Encryption Types
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/docs/hazmat/primitives/asymmetric/x448.rst b/docs/hazmat/primitives/asymmetric/x448.rst
index 057b7b50..9b00c6af 100644
--- a/docs/hazmat/primitives/asymmetric/x448.rst
+++ b/docs/hazmat/primitives/asymmetric/x448.rst
@@ -66,6 +66,24 @@ Key interfaces
 
         :returns: :class:`X448PrivateKey`
 
+    .. classmethod:: from_private_bytes(data)
+
+        :param bytes data: 56 byte private key.
+
+        :returns: :class:`X448PrivateKey`
+
+        .. doctest::
+
+            >>> from cryptography.hazmat.primitives import serialization
+            >>> from cryptography.hazmat.primitives.asymmetric import x448
+            >>> private_key = x448.X448PrivateKey.generate()
+            >>> private_bytes = private_key.private_bytes(
+            ...     encoding=serialization.Encoding.Raw,
+            ...     format=serialization.PrivateFormat.Raw,
+            ...     encryption_algorithm=serialization.NoEncryption()
+            ... )
+            >>> loaded_private_key = x448.X448PrivateKey.from_private_bytes(private_bytes)
+
     .. method:: public_key()
 
         :returns: :class:`X448PublicKey`
@@ -77,6 +95,36 @@ Key interfaces
 
         :returns bytes: A shared key.
 
+    .. method:: private_bytes(encoding, format, encryption_algorithm)
+
+        Allows serialization of the key to bytes. Encoding (
+        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.PEM`,
+        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.DER`, or
+        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.Raw`) and
+        format (
+        :attr:`~cryptography.hazmat.primitives.serialization.PrivateFormat.PKCS8`
+        or
+        :attr:`~cryptography.hazmat.primitives.serialization.PrivateFormat.Raw`
+        ) are chosen to define the exact serialization.
+
+        :param encoding: A value from the
+            :class:`~cryptography.hazmat.primitives.serialization.Encoding` enum.
+
+        :param format: A value from the
+            :class:`~cryptography.hazmat.primitives.serialization.PrivateFormat`
+            enum. If the ``encoding`` is
+            :attr:`~cryptography.hazmat.primitives.serialization.Encoding.Raw`
+            then ``format`` must be
+            :attr:`~cryptography.hazmat.primitives.serialization.PrivateFormat.Raw`
+            , otherwise it must be
+            :attr:`~cryptography.hazmat.primitives.serialization.PrivateFormat.PKCS8`.
+
+        :param encryption_algorithm: An instance of an object conforming to the
+            :class:`~cryptography.hazmat.primitives.serialization.KeySerializationEncryption`
+            interface.
+
+        :return bytes: Serialized key.
+
 .. class:: X448PublicKey
 
     .. versionadded:: 2.5
@@ -89,15 +137,41 @@ Key interfaces
 
         .. doctest::
 
+            >>> from cryptography.hazmat.primitives import serialization
             >>> from cryptography.hazmat.primitives.asymmetric import x448
             >>> private_key = x448.X448PrivateKey.generate()
             >>> public_key = private_key.public_key()
-            >>> public_bytes = public_key.public_bytes()
+            >>> public_bytes = public_key.public_bytes(
+            ...     encoding=serialization.Encoding.Raw,
+            ...     format=serialization.PublicFormat.Raw
+            ... )
             >>> loaded_public_key = x448.X448PublicKey.from_public_bytes(public_bytes)
 
-    .. method:: public_bytes()
-
-        :returns bytes: The raw bytes of the public key.
+    .. method:: public_bytes(encoding, format)
+
+        Allows serialization of the key to bytes. Encoding (
+        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.PEM`,
+        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.DER`, or
+        :attr:`~cryptography.hazmat.primitives.serialization.Encoding.Raw`) and
+        format (
+        :attr:`~cryptography.hazmat.primitives.serialization.PublicFormat.SubjectPublicKeyInfo`
+        or
+        :attr:`~cryptography.hazmat.primitives.serialization.PublicFormat.Raw`
+        ) are chosen to define the exact serialization.
+
+        :param encoding: A value from the
+            :class:`~cryptography.hazmat.primitives.serialization.Encoding` enum.
+
+        :param format: A value from the
+            :class:`~cryptography.hazmat.primitives.serialization.PublicFormat`
+            enum. If the ``encoding`` is
+            :attr:`~cryptography.hazmat.primitives.serialization.Encoding.Raw`
+            then ``format`` must be
+            :attr:`~cryptography.hazmat.primitives.serialization.PublicFormat.Raw`
+            , otherwise it must be
+            :attr:`~cryptography.hazmat.primitives.serialization.PublicFormat.SubjectPublicKeyInfo`.
+
+        :returns bytes: The public key bytes.
 
 
 .. _`Diffie-Hellman key exchange`: https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange