Scrypt Implementation (#3117)

* Scrypt implementation.

* Docs stuff.

* Make example just an example and not a doctest.

* Add changelog entry.

* Docs cleanup.

* Add more tests.

* Add multibackend tests.

* PEP8.

* Add docs about Scrypt parameters.

* Docs cleanup.

* Add AlreadyFinalized.

1 files changed, 15 insertions, 1 deletions

diff --git a/tests/hazmat/backends/test_multibackend.py b/tests/hazmat/backends/test_multibackend.py
index bf54d5ce..1cd87336 100644
--- a/tests/hazmat/backends/test_multibackend.py
+++ b/tests/hazmat/backends/test_multibackend.py
@@ -13,7 +13,7 @@ from cryptography.exceptions import (
 from cryptography.hazmat.backends.interfaces import (
     CMACBackend, CipherBackend, DERSerializationBackend, DSABackend,
     EllipticCurveBackend, HMACBackend, HashBackend, PBKDF2HMACBackend,
-    PEMSerializationBackend, RSABackend, X509Backend
+    PEMSerializationBackend, RSABackend, ScryptBackend, X509Backend
 )
 from cryptography.hazmat.backends.multibackend import MultiBackend
 from cryptography.hazmat.primitives import cmac, hashes, hmac
@@ -231,6 +231,12 @@ class DummyX509Backend(object):
         pass
 
 
+@utils.register_interface(ScryptBackend)
+class DummyScryptBackend(object):
+    def derive_scrypt(self, key_material, salt, length, n, r, p):
+        pass
+
+
 class TestMultiBackend(object):
     def test_raises_error_with_empty_list(self):
         with pytest.raises(ValueError):
@@ -558,3 +564,11 @@ class TestMultiBackend(object):
             )
         with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_X509):
             backend.create_x509_revoked_certificate(object())
+
+    def test_scrypt(self):
+        backend = MultiBackend([DummyScryptBackend()])
+        backend.derive_scrypt(b"key", b"salt", 1, 1, 1, 1)
+
+        backend = MultiBackend([DummyBackend])
+        with pytest.raises(UnsupportedAlgorithm):
+            backend.derive_scrypt(b"key", b"salt", 1, 1, 1, 1)