allow x25519/x448 public keys in certificatebuilder (#6562)

also document that we can return these key types in a certificate,
although they can't be self-signed of course

docs/x509/reference.rst

@@ -310,8 +310,10 @@ X.509 Certificate Object
             :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey`,
             :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPublicKey`,
             :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey`,
-            :class:`~cryptography.hazmat.primitives.asymmetric.ed25519.Ed25519PublicKey` or
-            :class:`~cryptography.hazmat.primitives.asymmetric.ed448.Ed448PublicKey`
+            :class:`~cryptography.hazmat.primitives.asymmetric.ed25519.Ed25519PublicKey`,
+            :class:`~cryptography.hazmat.primitives.asymmetric.ed448.Ed448PublicKey`,
+            :class:`~cryptography.hazmat.primitives.asymmetric.x25519.X25519PublicKey` or
+            :class:`~cryptography.hazmat.primitives.asymmetric.x448.X448PublicKey`
 
         .. doctest::
 
@@ -702,8 +704,10 @@ X.509 Certificate Builder
             :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey`,
             :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPublicKey`,
             :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey`,
-            :class:`~cryptography.hazmat.primitives.asymmetric.ed25519.Ed25519PublicKey` or
-            :class:`~cryptography.hazmat.primitives.asymmetric.ed448.Ed448PublicKey`.
+            :class:`~cryptography.hazmat.primitives.asymmetric.ed25519.Ed25519PublicKey`,
+            :class:`~cryptography.hazmat.primitives.asymmetric.ed448.Ed448PublicKey`,
+            :class:`~cryptography.hazmat.primitives.asymmetric.x25519.X25519PublicKey` or
+            :class:`~cryptography.hazmat.primitives.asymmetric.x448.X448PublicKey`.
 
     .. method:: serial_number(serial_number)
 

src/cryptography/hazmat/primitives/asymmetric/types.py

@@ -10,6 +10,8 @@
     ed25519,
     ed448,
     rsa,
+    x25519,
+    x448,
 )
 
 
@@ -27,3 +29,12 @@
     dsa.DSAPrivateKey,
     ec.EllipticCurvePrivateKey,
 ]
+CERTIFICATE_PUBLIC_KEY_TYPES = typing.Union[
+    dsa.DSAPublicKey,
+    rsa.RSAPublicKey,
+    ec.EllipticCurvePublicKey,
+    ed25519.Ed25519PublicKey,
+    ed448.Ed448PublicKey,
+    x25519.X25519PublicKey,
+    x448.X448PublicKey,
+]

src/cryptography/x509/base.py

@@ -17,8 +17,11 @@
     ed25519,
     ed448,
     rsa,
+    x25519,
+    x448,
 )
 from cryptography.hazmat.primitives.asymmetric.types import (
+    CERTIFICATE_PUBLIC_KEY_TYPES,
     PRIVATE_KEY_TYPES as PRIVATE_KEY_TYPES,
     PUBLIC_KEY_TYPES as PUBLIC_KEY_TYPES,
 )
@@ -101,7 +104,7 @@ def version(self) -> Version:
         """
 
     @abc.abstractmethod
-    def public_key(self) -> PUBLIC_KEY_TYPES:
+    def public_key(self) -> CERTIFICATE_PUBLIC_KEY_TYPES:
         """
         Returns the public key
         """
@@ -578,7 +581,7 @@ def __init__(
         self,
         issuer_name: typing.Optional[Name] = None,
         subject_name: typing.Optional[Name] = None,
-        public_key: typing.Optional[PUBLIC_KEY_TYPES] = None,
+        public_key: typing.Optional[CERTIFICATE_PUBLIC_KEY_TYPES] = None,
         serial_number: typing.Optional[int] = None,
         not_valid_before: typing.Optional[datetime.datetime] = None,
         not_valid_after: typing.Optional[datetime.datetime] = None,
@@ -631,7 +634,7 @@ def subject_name(self, name: Name) -> "CertificateBuilder":
 
     def public_key(
         self,
-        key: PUBLIC_KEY_TYPES,
+        key: CERTIFICATE_PUBLIC_KEY_TYPES,
     ) -> "CertificateBuilder":
         """
         Sets the requestor's public key (as found in the signing request).
@@ -644,12 +647,15 @@ def public_key(
                 ec.EllipticCurvePublicKey,
                 ed25519.Ed25519PublicKey,
                 ed448.Ed448PublicKey,
+                x25519.X25519PublicKey,
+                x448.X448PublicKey,
             ),
         ):
             raise TypeError(
                 "Expecting one of DSAPublicKey, RSAPublicKey,"
-                " EllipticCurvePublicKey, Ed25519PublicKey or"
-                " Ed448PublicKey."
+                " EllipticCurvePublicKey, Ed25519PublicKey,"
+                " Ed448PublicKey, X25519PublicKey, or "
+                "X448PublicKey."
             )
         if self._public_key is not None:
             raise ValueError("The public key may only be set once.")

tests/x509/test_x509.py

@@ -27,6 +27,8 @@
     ed448,
     padding,
     rsa,
+    x25519,
+    x448,
 )
 from cryptography.hazmat.primitives.asymmetric.utils import (
     decode_dss_signature,
@@ -2968,6 +2970,56 @@ def test_build_cert_with_public_ed448_rsa_sig(self, backend):
         assert isinstance(cert.signature_hash_algorithm, hashes.SHA256)
         assert isinstance(cert.public_key(), ed448.Ed448PublicKey)
 
+    @pytest.mark.supported(
+        only_if=lambda backend: (
+            backend.x25519_supported() and backend.x448_supported()
+        ),
+        skip_message="Requires OpenSSL with x25519 & x448 support",
+    )
+    @pytest.mark.parametrize(
+        ("priv_key_cls", "pub_key_cls"),
+        [
+            (x25519.X25519PrivateKey, x25519.X25519PublicKey),
+            (x448.X448PrivateKey, x448.X448PublicKey),
+        ],
+    )
+    def test_build_cert_with_public_x25519_x448_rsa_sig(
+        self, priv_key_cls, pub_key_cls, backend
+    ):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = priv_key_cls.generate()
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        builder = (
+            x509.CertificateBuilder()
+            .serial_number(777)
+            .issuer_name(
+                x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, "US")])
+            )
+            .subject_name(
+                x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, "US")])
+            )
+            .public_key(subject_private_key.public_key())
+            .not_valid_before(not_valid_before)
+            .not_valid_after(not_valid_after)
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA256(), backend)
+        assert cert.signature_hash_algorithm is not None
+        issuer_private_key.public_key().verify(
+            cert.signature,
+            cert.tbs_certificate_bytes,
+            padding.PKCS1v15(),
+            cert.signature_hash_algorithm,
+        )
+        assert cert.signature_algorithm_oid == (
+            SignatureAlgorithmOID.RSA_WITH_SHA256
+        )
+        assert isinstance(cert.signature_hash_algorithm, hashes.SHA256)
+        assert isinstance(cert.public_key(), pub_key_cls)
+
     def test_build_cert_with_rsa_key_too_small(self, backend):
         issuer_private_key = RSA_KEY_512.private_key(backend)
         subject_private_key = RSA_KEY_512.private_key(backend)