RSA OAEP label support for OpenSSL 1.0.2+ (#3897)

* RSA OAEP label support for OpenSSL 1.0.2+

* changelog

* move around tests, address review feedback, use backend supported method

* unsupported padding catches this now

1 files changed, 129 insertions, 2 deletions

diff --git a/tests/hazmat/primitives/test_rsa.py b/tests/hazmat/primitives/test_rsa.py
index 627248fd..fc956ecb 100644
--- a/tests/hazmat/primitives/test_rsa.py
+++ b/tests/hazmat/primitives/test_rsa.py
@@ -38,8 +38,8 @@ from ...doubles import (
     DummyAsymmetricPadding, DummyHashAlgorithm, DummyKeySerializationEncryption
 )
 from ...utils import (
-    load_pkcs1_vectors, load_rsa_nist_vectors, load_vectors_from_file,
-    raises_unsupported_algorithm
+    load_nist_vectors, load_pkcs1_vectors, load_rsa_nist_vectors,
+    load_vectors_from_file, raises_unsupported_algorithm
 )
 
 
@@ -218,6 +218,133 @@ class TestRSA(object):
         assert public_num.n == public_num2.n
         assert public_num.e == public_num2.e
 
+    @pytest.mark.parametrize(
+        "vector",
+        load_vectors_from_file(
+            os.path.join("asymmetric", "RSA", "oaep-label.txt"),
+            load_nist_vectors)
+    )
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.rsa_padding_supported(
+            padding.OAEP(
+                mgf=padding.MGF1(algorithm=hashes.SHA256()),
+                algorithm=hashes.SHA256(),
+                label=b"label"
+            )
+        ),
+        skip_message="Does not support RSA OAEP labels"
+    )
+    def test_oaep_label_decrypt(self, vector, backend):
+        private_key = serialization.load_der_private_key(
+            binascii.unhexlify(vector["key"]), None, backend
+        )
+        assert vector["oaepdigest"] == b"SHA512"
+        decrypted = private_key.decrypt(
+            binascii.unhexlify(vector["input"]),
+            padding.OAEP(
+                mgf=padding.MGF1(algorithm=hashes.SHA512()),
+                algorithm=hashes.SHA512(),
+                label=binascii.unhexlify(vector["oaeplabel"])
+            )
+        )
+        assert vector["output"][1:-1] == decrypted
+
+    @pytest.mark.parametrize(
+        ("msg", "label"),
+        [
+            (b"amazing encrypted msg", b"some label"),
+            (b"amazing encrypted msg", b""),
+        ]
+    )
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.rsa_padding_supported(
+            padding.OAEP(
+                mgf=padding.MGF1(algorithm=hashes.SHA256()),
+                algorithm=hashes.SHA256(),
+                label=b"label"
+            )
+        ),
+        skip_message="Does not support RSA OAEP labels"
+    )
+    def test_oaep_label_roundtrip(self, msg, label, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        ct = private_key.public_key().encrypt(
+            msg,
+            padding.OAEP(
+                mgf=padding.MGF1(algorithm=hashes.SHA256()),
+                algorithm=hashes.SHA256(),
+                label=label
+            )
+        )
+        pt = private_key.decrypt(
+            ct,
+            padding.OAEP(
+                mgf=padding.MGF1(algorithm=hashes.SHA256()),
+                algorithm=hashes.SHA256(),
+                label=label
+            )
+        )
+        assert pt == msg
+
+    @pytest.mark.parametrize(
+        ("enclabel", "declabel"),
+        [
+            (b"label1", b"label2"),
+            (b"label3", b""),
+            (b"", b"label4"),
+        ]
+    )
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.rsa_padding_supported(
+            padding.OAEP(
+                mgf=padding.MGF1(algorithm=hashes.SHA256()),
+                algorithm=hashes.SHA256(),
+                label=b"label"
+            )
+        ),
+        skip_message="Does not support RSA OAEP labels"
+    )
+    def test_oaep_wrong_label(self, enclabel, declabel, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        msg = b"test"
+        ct = private_key.public_key().encrypt(
+            msg, padding.OAEP(
+                mgf=padding.MGF1(algorithm=hashes.SHA256()),
+                algorithm=hashes.SHA256(),
+                label=enclabel
+            )
+        )
+        with pytest.raises(ValueError):
+            private_key.decrypt(
+                ct, padding.OAEP(
+                    mgf=padding.MGF1(algorithm=hashes.SHA256()),
+                    algorithm=hashes.SHA256(),
+                    label=declabel
+                )
+            )
+
+    @pytest.mark.supported(
+        only_if=lambda backend: not backend.rsa_padding_supported(
+            padding.OAEP(
+                mgf=padding.MGF1(algorithm=hashes.SHA256()),
+                algorithm=hashes.SHA256(),
+                label=b"label"
+            )
+        ),
+        skip_message="Requires backend without RSA OAEP label support"
+    )
+    def test_unsupported_oaep_label_decrypt(self, backend):
+        private_key = RSA_KEY_512.private_key(backend)
+        with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_PADDING):
+            private_key.decrypt(
+                b"0" * 64,
+                padding.OAEP(
+                    mgf=padding.MGF1(algorithm=hashes.SHA1()),
+                    algorithm=hashes.SHA1(),
+                    label=b"label"
+                )
+            )
+
 
 def test_rsa_generate_invalid_backend():
     pretend_backend = object()