Source code for google.auth.crypt.es256

# Copyright 2017 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""ECDSA (ES256) verifier and signer that use the ``cryptography`` library.
"""

import cryptography.exceptions
from cryptography.hazmat import backends
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.hazmat.primitives.asymmetric import padding
import cryptography.x509
import pkg_resources

from google.auth import _helpers
from google.auth.crypt import base

_IMPORT_ERROR_MSG = (
    "cryptography>=1.4.0 is required to use cryptography-based ECDSA " "algorithms"
)

try:  # pragma: NO COVER
    release = pkg_resources.get_distribution("cryptography").parsed_version
    if release < pkg_resources.parse_version("1.4.0"):
        raise ImportError(_IMPORT_ERROR_MSG)
except pkg_resources.DistributionNotFound:  # pragma: NO COVER
    raise ImportError(_IMPORT_ERROR_MSG)


_CERTIFICATE_MARKER = b"-----BEGIN CERTIFICATE-----"
_BACKEND = backends.default_backend()
_PADDING = padding.PKCS1v15()


[docs]class ES256Verifier(base.Verifier): """Verifies ECDSA cryptographic signatures using public keys. Args: public_key ( cryptography.hazmat.primitives.asymmetric.ec.ECDSAPublicKey): The public key used to verify signatures. """ def __init__(self, public_key): self._pubkey = public_key
[docs] @_helpers.copy_docstring(base.Verifier) def verify(self, message, signature): message = _helpers.to_bytes(message) try: self._pubkey.verify(signature, message, ec.ECDSA(hashes.SHA256())) return True except (ValueError, cryptography.exceptions.InvalidSignature): return False
[docs] @classmethod def from_string(cls, public_key): """Construct an 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. Raises: ValueError: If the public key can't be parsed. """ public_key_data = _helpers.to_bytes(public_key) if _CERTIFICATE_MARKER in public_key_data: cert = cryptography.x509.load_pem_x509_certificate( public_key_data, _BACKEND ) pubkey = cert.public_key() else: pubkey = serialization.load_pem_public_key(public_key_data, _BACKEND) return cls(pubkey)
[docs]class ES256Signer(base.Signer, base.FromServiceAccountMixin): """Signs messages with an ECDSA private key. Args: private_key ( cryptography.hazmat.primitives.asymmetric.ec.ECDSAPrivateKey): 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. """ def __init__(self, private_key, key_id=None): self._key = private_key self._key_id = key_id @property @_helpers.copy_docstring(base.Signer) def key_id(self): return self._key_id
[docs] @_helpers.copy_docstring(base.Signer) def sign(self, message): message = _helpers.to_bytes(message) return self._key.sign(message, ec.ECDSA(hashes.SHA256()))
[docs] @classmethod def from_string(cls, key, key_id=None): """Construct a RSASigner from a private key in PEM format. Args: key (Union[bytes, str]): Private key in PEM format. key_id (str): An optional key id used to identify the private key. Returns: google.auth.crypt._cryptography_rsa.RSASigner: The constructed signer. Raises: ValueError: If ``key`` is not ``bytes`` or ``str`` (unicode). UnicodeDecodeError: If ``key`` is ``bytes`` but cannot be decoded into a UTF-8 ``str``. ValueError: If ``cryptography`` "Could not deserialize key data." """ key = _helpers.to_bytes(key) private_key = serialization.load_pem_private_key( key, password=None, backend=_BACKEND ) return cls(private_key, key_id=key_id)