222 lines
7.8 KiB
Python
222 lines
7.8 KiB
Python
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# Copyright 2017 Google Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""ECDSA verifier and signer that use the ``cryptography`` library.
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"""
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from dataclasses import dataclass
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from typing import Any, Dict, Optional, Union
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import cryptography.exceptions
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from cryptography.hazmat import backends
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from cryptography.hazmat.primitives import hashes
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from cryptography.hazmat.primitives import serialization
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from cryptography.hazmat.primitives.asymmetric import ec
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from cryptography.hazmat.primitives.asymmetric import padding
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from cryptography.hazmat.primitives.asymmetric.utils import decode_dss_signature
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from cryptography.hazmat.primitives.asymmetric.utils import encode_dss_signature
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import cryptography.x509
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from google.auth import _helpers
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from google.auth.crypt import base
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_CERTIFICATE_MARKER = b"-----BEGIN CERTIFICATE-----"
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_BACKEND = backends.default_backend()
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_PADDING = padding.PKCS1v15()
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@dataclass
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class _ESAttributes:
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"""A class that models ECDSA attributes.
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Attributes:
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rs_size (int): Size for ASN.1 r and s size.
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sha_algo (hashes.HashAlgorithm): Hash algorithm.
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algorithm (str): Algorithm name.
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"""
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rs_size: int
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sha_algo: hashes.HashAlgorithm
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algorithm: str
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@classmethod
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def from_key(
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cls, key: Union[ec.EllipticCurvePublicKey, ec.EllipticCurvePrivateKey]
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):
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return cls.from_curve(key.curve)
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@classmethod
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def from_curve(cls, curve: ec.EllipticCurve):
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# ECDSA raw signature has (r||s) format where r,s are two
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# integers of size 32 bytes for P-256 curve and 48 bytes
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# for P-384 curve. For P-256 curve, we use SHA256 hash algo,
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# and for P-384 curve we use SHA384 algo.
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if isinstance(curve, ec.SECP384R1):
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return cls(48, hashes.SHA384(), "ES384")
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else:
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# default to ES256
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return cls(32, hashes.SHA256(), "ES256")
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class EsVerifier(base.Verifier):
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"""Verifies ECDSA cryptographic signatures using public keys.
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Args:
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public_key (
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cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey):
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The public key used to verify signatures.
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"""
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def __init__(self, public_key: ec.EllipticCurvePublicKey) -> None:
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self._pubkey = public_key
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self._attributes = _ESAttributes.from_key(public_key)
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@_helpers.copy_docstring(base.Verifier)
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def verify(self, message: bytes, signature: bytes) -> bool:
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# First convert (r||s) raw signature to ASN1 encoded signature.
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sig_bytes = _helpers.to_bytes(signature)
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if len(sig_bytes) != self._attributes.rs_size * 2:
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return False
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r = int.from_bytes(sig_bytes[: self._attributes.rs_size], byteorder="big")
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s = int.from_bytes(sig_bytes[self._attributes.rs_size :], byteorder="big")
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asn1_sig = encode_dss_signature(r, s)
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message = _helpers.to_bytes(message)
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try:
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self._pubkey.verify(asn1_sig, message, ec.ECDSA(self._attributes.sha_algo))
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return True
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except (ValueError, cryptography.exceptions.InvalidSignature):
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return False
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@classmethod
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def from_string(cls, public_key: Union[str, bytes]) -> "EsVerifier":
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"""Construct an Verifier instance from a public key or public
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certificate string.
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Args:
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public_key (Union[str, bytes]): The public key in PEM format or the
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x509 public key certificate.
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Returns:
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Verifier: The constructed verifier.
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Raises:
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ValueError: If the public key can't be parsed.
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"""
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public_key_data = _helpers.to_bytes(public_key)
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if _CERTIFICATE_MARKER in public_key_data:
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cert = cryptography.x509.load_pem_x509_certificate(
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public_key_data, _BACKEND
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)
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pubkey = cert.public_key() # type: Any
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else:
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pubkey = serialization.load_pem_public_key(public_key_data, _BACKEND)
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if not isinstance(pubkey, ec.EllipticCurvePublicKey):
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raise TypeError("Expected public key of type EllipticCurvePublicKey")
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return cls(pubkey)
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class EsSigner(base.Signer, base.FromServiceAccountMixin):
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"""Signs messages with an ECDSA private key.
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Args:
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private_key (
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cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePrivateKey):
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The private key to sign with.
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key_id (str): Optional key ID used to identify this private key. This
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can be useful to associate the private key with its associated
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public key or certificate.
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"""
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def __init__(
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self, private_key: ec.EllipticCurvePrivateKey, key_id: Optional[str] = None
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) -> None:
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self._key = private_key
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self._key_id = key_id
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self._attributes = _ESAttributes.from_key(private_key)
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@property
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def algorithm(self) -> str:
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"""Name of the algorithm used to sign messages.
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Returns:
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str: The algorithm name.
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"""
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return self._attributes.algorithm
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@property # type: ignore
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@_helpers.copy_docstring(base.Signer)
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def key_id(self) -> Optional[str]:
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return self._key_id
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@_helpers.copy_docstring(base.Signer)
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def sign(self, message: bytes) -> bytes:
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message = _helpers.to_bytes(message)
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asn1_signature = self._key.sign(message, ec.ECDSA(self._attributes.sha_algo))
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# Convert ASN1 encoded signature to (r||s) raw signature.
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(r, s) = decode_dss_signature(asn1_signature)
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return r.to_bytes(self._attributes.rs_size, byteorder="big") + s.to_bytes(
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self._attributes.rs_size, byteorder="big"
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)
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@classmethod
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def from_string(
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cls, key: Union[bytes, str], key_id: Optional[str] = None
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) -> "EsSigner":
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"""Construct a RSASigner from a private key in PEM format.
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Args:
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key (Union[bytes, str]): Private key in PEM format.
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key_id (str): An optional key id used to identify the private key.
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Returns:
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google.auth.crypt._cryptography_rsa.RSASigner: The
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constructed signer.
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Raises:
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ValueError: If ``key`` is not ``bytes`` or ``str`` (unicode).
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UnicodeDecodeError: If ``key`` is ``bytes`` but cannot be decoded
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into a UTF-8 ``str``.
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ValueError: If ``cryptography`` "Could not deserialize key data."
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"""
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key_bytes = _helpers.to_bytes(key)
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private_key = serialization.load_pem_private_key(
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key_bytes, password=None, backend=_BACKEND
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)
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if not isinstance(private_key, ec.EllipticCurvePrivateKey):
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raise TypeError("Expected private key of type EllipticCurvePrivateKey")
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return cls(private_key, key_id=key_id)
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def __getstate__(self) -> Dict[str, Any]:
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"""Pickle helper that serializes the _key attribute."""
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state = self.__dict__.copy()
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state["_key"] = self._key.private_bytes(
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encoding=serialization.Encoding.PEM,
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format=serialization.PrivateFormat.PKCS8,
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encryption_algorithm=serialization.NoEncryption(),
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)
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return state
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def __setstate__(self, state: Dict[str, Any]) -> None:
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"""Pickle helper that deserializes the _key attribute."""
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state["_key"] = serialization.load_pem_private_key(state["_key"], None)
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self.__dict__.update(state)
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