EC public/private key loader functions try deprecated as fallback

2 files changed, 29 insertions, 2 deletions

diff --git a/cryptography/hazmat/primitives/asymmetric/ec.py b/cryptography/hazmat/primitives/asymmetric/ec.py
index 3893cc2f..6dcf39cf 100644
--- a/cryptography/hazmat/primitives/asymmetric/ec.py
+++ b/cryptography/hazmat/primitives/asymmetric/ec.py
@@ -238,7 +238,10 @@ class EllipticCurvePublicNumbers(object):
         self._curve = curve
 
     def public_key(self, backend):
-        return backend.load_elliptic_curve_public_numbers(self)
+        try:
+            return backend.load_elliptic_curve_public_numbers(self)
+        except AttributeError:
+            return backend.elliptic_curve_public_key_from_numbers(self)
 
     @property
     def curve(self):
@@ -268,7 +271,10 @@ class EllipticCurvePrivateNumbers(object):
         self._public_numbers = public_numbers
 
     def private_key(self, backend):
-        return backend.load_elliptic_curve_private_numbers(self)
+        try:
+            return backend.load_elliptic_curve_private_numbers(self)
+        except AttributeError:
+            return backend.elliptic_curve_private_key_from_numbers(self)
 
     @property
     def private_value(self):
diff --git a/tests/hazmat/primitives/test_ec.py b/tests/hazmat/primitives/test_ec.py
index 65461f70..35505820 100644
--- a/tests/hazmat/primitives/test_ec.py
+++ b/tests/hazmat/primitives/test_ec.py
@@ -20,6 +20,7 @@ import os
 import pytest
 
 from cryptography import exceptions, utils
+from cryptography.hazmat.backends.interfaces import EllipticCurveBackend
 from cryptography.hazmat.primitives import hashes, interfaces
 from cryptography.hazmat.primitives.asymmetric import ec
 
@@ -70,6 +71,15 @@ class DummySignatureAlgorithm(object):
     pass
 
 
+@utils.register_interface(EllipticCurveBackend)
+class DeprecatedDummyECBackend(object):
+    def elliptic_curve_private_key_from_numbers(self, numbers):
+        return b"private_key"
+
+    def elliptic_curve_public_key_from_numbers(self, numbers):
+        return b"public_key"
+
+
 @pytest.mark.elliptic
 def test_skip_curve_unsupported(backend):
     with pytest.raises(pytest.skip.Exception):
@@ -282,3 +292,14 @@ class TestECDSAVectors(object):
                 verifier.verify()
         else:
             verifier.verify()
+
+    def test_deprecated_public_private_key_load(self):
+        b = DeprecatedDummyECBackend()
+        pub_numbers = ec.EllipticCurvePublicNumbers(
+            2,
+            3,
+            ec.SECT283K1()
+        )
+        numbers = ec.EllipticCurvePrivateNumbers(1, pub_numbers)
+        assert numbers.private_key(b) == b"private_key"
+        assert pub_numbers.public_key(b) == b"public_key"