make signature and verification contexts error better re: prehashed (#3658)

* make signature and verification contexts error better re: prehashed

* code review feedback

1 files changed, 29 insertions, 0 deletions

diff --git a/tests/hazmat/primitives/test_rsa.py b/tests/hazmat/primitives/test_rsa.py
index cbb9be6f..7ce2746c 100644
--- a/tests/hazmat/primitives/test_rsa.py
+++ b/tests/hazmat/primitives/test_rsa.py
@@ -531,6 +531,35 @@ class TestRSASignature(object):
         with pytest.raises(ValueError):
             private_key.sign(digest, pss, prehashed_alg)
 
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.rsa_padding_supported(
+            padding.PKCS1v15()
+        ),
+        skip_message="Does not support PKCS1v1.5."
+    )
+    def test_prehashed_unsupported_in_signer_ctx(self, backend):
+        private_key = RSA_KEY_512.private_key(backend)
+        with pytest.raises(TypeError):
+            private_key.signer(
+                padding.PKCS1v15(),
+                asym_utils.Prehashed(hashes.SHA1())
+            )
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.rsa_padding_supported(
+            padding.PKCS1v15()
+        ),
+        skip_message="Does not support PKCS1v1.5."
+    )
+    def test_prehashed_unsupported_in_verifier_ctx(self, backend):
+        public_key = RSA_KEY_512.private_key(backend).public_key()
+        with pytest.raises(TypeError):
+            public_key.verifier(
+                b"0" * 64,
+                padding.PKCS1v15(),
+                asym_utils.Prehashed(hashes.SHA1())
+            )
+
 
 @pytest.mark.requires_backend_interface(interface=RSABackend)
 class TestRSAVerification(object):