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Diffstat (limited to 'google/auth/crypt/es256.py')
-rw-r--r-- | google/auth/crypt/es256.py | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/google/auth/crypt/es256.py b/google/auth/crypt/es256.py new file mode 100644 index 0000000..42823a7 --- /dev/null +++ b/google/auth/crypt/es256.py @@ -0,0 +1,160 @@ +# 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. +""" + +from cryptography import utils +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 +from cryptography.hazmat.primitives.asymmetric.utils import decode_dss_signature +from cryptography.hazmat.primitives.asymmetric.utils import encode_dss_signature +import cryptography.x509 + +from google.auth import _helpers +from google.auth.crypt import base + + +_CERTIFICATE_MARKER = b"-----BEGIN CERTIFICATE-----" +_BACKEND = backends.default_backend() +_PADDING = padding.PKCS1v15() + + +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 + + @_helpers.copy_docstring(base.Verifier) + def verify(self, message, signature): + # First convert (r||s) raw signature to ASN1 encoded signature. + sig_bytes = _helpers.to_bytes(signature) + if len(sig_bytes) != 64: + return False + r = ( + int.from_bytes(sig_bytes[:32], byteorder="big") + if _helpers.is_python_3() + else utils.int_from_bytes(sig_bytes[:32], byteorder="big") + ) + s = ( + int.from_bytes(sig_bytes[32:], byteorder="big") + if _helpers.is_python_3() + else utils.int_from_bytes(sig_bytes[32:], byteorder="big") + ) + asn1_sig = encode_dss_signature(r, s) + + message = _helpers.to_bytes(message) + try: + self._pubkey.verify(asn1_sig, message, ec.ECDSA(hashes.SHA256())) + return True + except (ValueError, cryptography.exceptions.InvalidSignature): + return False + + @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) + + +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 + + @_helpers.copy_docstring(base.Signer) + def sign(self, message): + message = _helpers.to_bytes(message) + asn1_signature = self._key.sign(message, ec.ECDSA(hashes.SHA256())) + + # Convert ASN1 encoded signature to (r||s) raw signature. + (r, s) = decode_dss_signature(asn1_signature) + return ( + (r.to_bytes(32, byteorder="big") + s.to_bytes(32, byteorder="big")) + if _helpers.is_python_3() + else (utils.int_to_bytes(r, 32) + utils.int_to_bytes(s, 32)) + ) + + @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) |