feat: add cryptography as required dependency

google/auth/crypt/__init__.py

@@ -38,35 +38,14 @@
 """
 
 from google.auth.crypt import base
+from google.auth.crypt import es
+from google.auth.crypt import es256
 from google.auth.crypt import rsa
 
-# google.auth.crypt.es depends on the crytpography module which may not be
-# successfully imported depending on the system.
-try:
-    from google.auth.crypt import es
-    from google.auth.crypt import es256
-except ImportError:  # pragma: NO COVER
-    es = None  # type: ignore
-    es256 = None  # type: ignore
-
-if es is not None and es256 is not None:  # pragma: NO COVER
-    __all__ = [
-        "EsSigner",
-        "EsVerifier",
-        "ES256Signer",
-        "ES256Verifier",
-        "RSASigner",
-        "RSAVerifier",
-        "Signer",
-        "Verifier",
-    ]
-
-    EsSigner = es.EsSigner
-    EsVerifier = es.EsVerifier
-    ES256Signer = es256.ES256Signer
-    ES256Verifier = es256.ES256Verifier
-else:  # pragma: NO COVER
-    __all__ = ["RSASigner", "RSAVerifier", "Signer", "Verifier"]
+EsSigner = es.EsSigner
+EsVerifier = es.EsVerifier
+ES256Signer = es256.ES256Signer
+ES256Verifier = es256.ES256Verifier
 
 
 # Aliases to maintain the v1.0.0 interface, as the crypt module was split
@@ -103,3 +82,15 @@ class to use for verification. This can be used to select different
         if verifier.verify(message, signature):
             return True
     return False
+
+
+__all__ = [
+    "EsSigner",
+    "EsVerifier",
+    "ES256Signer",
+    "ES256Verifier",
+    "RSASigner",
+    "RSAVerifier",
+    "Signer",
+    "Verifier",
+]

google/auth/crypt/_python_rsa.py

@@ -40,13 +40,9 @@
 _PKCS8_MARKER = ("-----BEGIN PRIVATE KEY-----", "-----END PRIVATE KEY-----")
 _PKCS8_SPEC = PrivateKeyInfo()
 
-warnings.warn(
-    (
-        "The 'rsa' library is deprecated and will be removed in a future release. "
-        "Please migrate to 'cryptography'."
-    ),
-    category=DeprecationWarning,
-    stacklevel=2,
+_warning_msg = (
+    "The 'rsa' library is deprecated and will be removed in a future release. "
+    "Please migrate to 'cryptography'."
 )
 
 
@@ -84,6 +80,11 @@ class RSAVerifier(base.Verifier):
     """
 
     def __init__(self, public_key):
+        warnings.warn(
+            _warning_msg,
+            category=DeprecationWarning,
+            stacklevel=2,
+        )
         self._pubkey = public_key
 
     @_helpers.copy_docstring(base.Verifier)
@@ -142,6 +143,11 @@ class RSASigner(base.Signer, base.FromServiceAccountMixin):
     """
 
     def __init__(self, private_key, key_id=None):
+        warnings.warn(
+            _warning_msg,
+            category=DeprecationWarning,
+            stacklevel=2,
+        )
         self._key = private_key
         self._key_id = key_id
 

google/auth/crypt/es.py

@@ -102,15 +102,15 @@ def verify(self, message: bytes, signature: bytes) -> bool:
 
     @classmethod
     def from_string(cls, public_key: Union[str, bytes]) -> "EsVerifier":
-        """Construct an Verifier instance from a public key or public
+        """Construct a Verifier instance from a public key or public
         certificate string.
 
         Args:
             public_key (Union[str, bytes]): The public key in PEM format or the
                 x509 public key certificate.
 
         Returns:
-            Verifier: The constructed verifier.
+            google.auth.crypt.Verifier: The constructed verifier.
 
         Raises:
             ValueError: If the public key can't be parsed.

google/auth/crypt/rsa.py

@@ -12,19 +12,116 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""RSA cryptography signer and verifier."""
+"""
+RSA cryptography signer and verifier.
 
+This file provides a shared wrapper, that defers to _python_rsa or _cryptography_rsa
+for implmentations using different third party libraries
+"""
 
-try:
-    # Prefer cryptograph-based RSA implementation.
-    from google.auth.crypt import _cryptography_rsa
+from cryptography.hazmat.primitives.asymmetric.rsa import RSAPrivateKey
+from cryptography.hazmat.primitives.asymmetric.rsa import RSAPublicKey
 
-    RSASigner = _cryptography_rsa.RSASigner
-    RSAVerifier = _cryptography_rsa.RSAVerifier
-except ImportError:  # pragma: NO COVER
-    # Fallback to pure-python RSA implementation if cryptography is
-    # unavailable.
-    from google.auth.crypt import _python_rsa
+from google.auth import _helpers
+from google.auth.crypt import _cryptography_rsa
+from google.auth.crypt import _python_rsa
+from google.auth.crypt import base
 
-    RSASigner = _python_rsa.RSASigner  # type: ignore
-    RSAVerifier = _python_rsa.RSAVerifier  # type: ignore
+RSA_KEY_MODULE_PREFIX = "rsa.key"
+
+
+class RSAVerifier(base.Verifier):
+    """Verifies RSA cryptographic signatures using public keys.
+
+    Args:
+        public_key (Union["rsa.key.PublicKey", cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey]):
+            The public key used to verify signatures.
+    Raises:
+        ValueError: if an unrecognized public key is provided
+    """
+
+    def __init__(self, public_key):
+        module_str = public_key.__class__.__module__
+        if isinstance(public_key, RSAPublicKey):
+            impl_lib = _cryptography_rsa
+        elif module_str.startswith(RSA_KEY_MODULE_PREFIX):
+            impl_lib = _python_rsa
+        else:
+            raise ValueError(f"unrecognized public key type: {type(public_key)}")
+        self._impl = impl_lib.RSAVerifier(public_key)
+
+    @_helpers.copy_docstring(base.Verifier)
+    def verify(self, message, signature):
+        return self._impl.verify(message, signature)
+
+    @classmethod
+    def from_string(cls, public_key):
+        """Construct a Verifier instance from a public key or public
+        certificate string.
+
+        Args:
+            public_key (Union[str, bytes]): The public key in PEM format or the
+                x509 public key certificate.
+
+        Returns:
+            google.auth.crypt.Verifier: The constructed verifier.
+
+        Raises:
+            ValueError: If the public_key can't be parsed.
+        """
+        instance = cls.__new__(cls)
+        instance._impl = _cryptography_rsa.RSAVerifier.from_string(public_key)
+        return instance
+
+
+class RSASigner(base.Signer, base.FromServiceAccountMixin):
+    """Signs messages with an RSA private key.
+
+    Args:
+        private_key (Union["rsa.key.PrivateKey", cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey]):
+            The private key to sign with.
+        key_id (str): Optional key ID used to identify this private key. This
+            can be useful to associate the private key with its associated
+            public key or certificate.
+
+    Raises:
+        ValueError: if an unrecognized public key is provided
+    """
+
+    def __init__(self, private_key, key_id=None):
+        module_str = private_key.__class__.__module__
+        if isinstance(private_key, RSAPrivateKey):
+            impl_lib = _cryptography_rsa
+        elif module_str.startswith(RSA_KEY_MODULE_PREFIX):
+            impl_lib = _python_rsa
+        else:
+            raise ValueError(f"unrecognized private key type: {type(private_key)}")
+        self._impl = impl_lib.RSASigner(private_key, key_id=key_id)
+
+    @property  # type: ignore
+    @_helpers.copy_docstring(base.Signer)
+    def key_id(self):
+        return self._impl.key_id
+
+    @_helpers.copy_docstring(base.Signer)
+    def sign(self, message):
+        return self._impl.sign(message)
+
+    @classmethod
+    def from_string(cls, key, key_id=None):
+        """Construct a Signer instance from a private key in PEM format.
+
+        Args:
+            key (str): Private key in PEM format.
+            key_id (str): An optional key id used to identify the private key.
+
+        Returns:
+            google.auth.crypt.Signer: The constructed signer.
+
+        Raises:
+            ValueError: If the key cannot be parsed as PKCS#1 or PKCS#8 in
+                PEM format.
+        """
+        instance = cls.__new__(cls)
+        instance._impl = _cryptography_rsa.RSASigner.from_string(key, key_id=key_id)
+        return instance

setup.py

@@ -18,30 +18,30 @@
 from setuptools import find_namespace_packages
 from setuptools import setup
 
+cryptography_base_require = [
+    "cryptography >= 38.0.3",
+]
 
 DEPENDENCIES = (
     "pyasn1-modules>=0.2.1",
-    # rsa==4.5 is the last version to support 2.7
-    # https://github.com/sybrenstuvel/python-rsa/issues/152#issuecomment-643470233
+    cryptography_base_require,
+    # TODO: remove rsa from dependencies in next release (replaced with cryptography)i
+    # https://github.com/googleapis/google-auth-library-python/issues/1810
     "rsa>=3.1.4,<5",
 )
 
-cryptography_base_require = [
-    "cryptography >= 38.0.3",
-]
-
 requests_extra_require = ["requests >= 2.20.0, < 3.0.0"]
 
 aiohttp_extra_require = ["aiohttp >= 3.6.2, < 4.0.0", *requests_extra_require]
 
-pyjwt_extra_require = ["pyjwt>=2.0", *cryptography_base_require]
+pyjwt_extra_require = ["pyjwt>=2.0"]
 
 reauth_extra_require = ["pyu2f>=0.1.5"]
 
-# TODO(https://github.com/googleapis/google-auth-library-python/issues/1738): Add bounds for cryptography and pyopenssl dependencies.
-enterprise_cert_extra_require = ["cryptography", "pyopenssl"]
+# TODO(https://github.com/googleapis/google-auth-library-python/issues/1738): Add bounds for pyopenssl dependency.
+enterprise_cert_extra_require = ["pyopenssl"]
 
-pyopenssl_extra_require = ["pyopenssl>=20.0.0", cryptography_base_require]
+pyopenssl_extra_require = ["pyopenssl>=20.0.0"]
 
 # TODO(https://github.com/googleapis/google-auth-library-python/issues/1739): Add bounds for urllib3 and packaging dependencies.
 urllib3_extra_require = ["urllib3", "packaging"]
@@ -76,6 +76,7 @@
 ]
 
 extras = {
+    # Note: cryptography was made into a required dependency. Extra is kept for backwards compatibility
     "cryptography": cryptography_base_require,
     "aiohttp": aiohttp_extra_require,
     "enterprise_cert": enterprise_cert_extra_require,

tests/crypt/test__python_rsa.py

@@ -195,8 +195,9 @@ def test_from_service_account_file(self):
 
 class TestModule(object):
     def test_import_warning(self):
-        import importlib
         from google.auth.crypt import _python_rsa
 
         with pytest.warns(DeprecationWarning, match="The 'rsa' library is deprecated"):
-            importlib.reload(_python_rsa)
+            _python_rsa.RSAVerifier(None)
+        with pytest.warns(DeprecationWarning, match="The 'rsa' library is deprecated"):
+            _python_rsa.RSASigner(None)