Serialization x25519 (#4688)

* modify x25519 serialization to match x448

supports raw and pkcs8 encoding on private_bytes
supports raw and subjectpublickeyinfo on public_bytes

deprecates zero argument call to public_bytes

* add docs

* this is public now

* don't need that

* review feedback

1 files changed, 6 insertions, 0 deletions

diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index ecebe7b8..9eca5f8a 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -511,6 +511,9 @@ class Backend(object):
         elif key_type == getattr(self._lib, "EVP_PKEY_X448", None):
             # EVP_PKEY_X448 is not present in OpenSSL < 1.1.1
             return _X448PrivateKey(self, evp_pkey)
+        elif key_type == getattr(self._lib, "EVP_PKEY_X25519", None):
+            # EVP_PKEY_X25519 is not present in OpenSSL < 1.1.0
+            return _X25519PrivateKey(self, evp_pkey)
         else:
             raise UnsupportedAlgorithm("Unsupported key type.")
 
@@ -545,6 +548,9 @@ class Backend(object):
         elif key_type == getattr(self._lib, "EVP_PKEY_X448", None):
             # EVP_PKEY_X448 is not present in OpenSSL < 1.1.1
             return _X448PublicKey(self, evp_pkey)
+        elif key_type == getattr(self._lib, "EVP_PKEY_X25519", None):
+            # EVP_PKEY_X25519 is not present in OpenSSL < 1.1.0
+            return _X25519PublicKey(self, evp_pkey)
         else:
             raise UnsupportedAlgorithm("Unsupported key type.")