fixes #12070 -- made SSH private key loading more consistent with other key loading (#12286)

CHANGELOG.rst

@@ -10,8 +10,15 @@ Changelog
 
 * Support for Python 3.7 is deprecated and will be removed in the next
   ``cryptography`` release.
-* Added support for PKCS7 decryption & encryption using AES-256 as content algorithm, 
-  in addition to AES-128. 
+* Added support for PKCS7 decryption & encryption using AES-256 as content algorithm,
+  in addition to AES-128.
+* **BACKWARDS INCOMPATIBLE:** Made SSH private key loading more consistent with
+  other private key loading:
+  :func:`~cryptography.hazmat.primitives.serialization.load_ssh_private_key`
+  now raises a ``TypeError`` if the key is unencrypted but a password is
+  provided (previously no exception was raised), and raises a ``TypeError`` if
+  the key is encrypted but no password is provided (previously a ``ValueError``
+  was raised).
 
 .. _v44-0-0:
 

src/cryptography/hazmat/primitives/serialization/ssh.py

@@ -196,7 +196,9 @@ def _init_cipher(
 ) -> Cipher[modes.CBC | modes.CTR | modes.GCM]:
     """Generate key + iv and return cipher."""
     if not password:
-        raise ValueError("Key is password-protected.")
+        raise TypeError(
+            "Key is password-protected, but password was not provided."
+        )
 
     ciph = _SSH_CIPHERS[ciphername]
     seed = _bcrypt_kdf(
@@ -745,6 +747,10 @@ def load_ssh_private_key(
             # should be no output from finalize
             _check_empty(dec.finalize())
     else:
+        if password:
+            raise TypeError(
+                "Password was given but private key is not encrypted."
+            )
         # load secret data
         edata, data = _get_sshstr(data)
         _check_empty(data)

tests/hazmat/primitives/test_ssh.py

@@ -375,7 +375,7 @@ class TestOpenSSHSerialization:
             )
             assert pub1 == pub2
 
-            with pytest.raises(ValueError):
+            with pytest.raises(TypeError):
                 decoded_key = load_ssh_private_key(encdata, None, backend)
             with pytest.raises(ValueError):
                 decoded_key = load_ssh_private_key(encdata, b"wrong", backend)
@@ -611,6 +611,15 @@ class TestOpenSSHSerialization:
         with pytest.raises(ValueError):
             load_ssh_private_key(data, None, backend)
 
+    def test_ssh_errors_unencrypted_with_password(self):
+        data = load_vectors_from_file(
+            os.path.join("asymmetric", "OpenSSH", "rsa-nopsw.key"),
+            lambda f: f.read(),
+            mode="rb",
+        )
+        with pytest.raises(TypeError):
+            load_ssh_private_key(data, password=b"password")
+
     @pytest.mark.supported(
         only_if=lambda backend: backend.elliptic_curve_supported(
             ec.SECP192R1()