forked from s434650/CatOrNot
132 lines
4.1 KiB
Python
132 lines
4.1 KiB
Python
# Copyright 2016 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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"""Base classes for cryptographic signers and verifiers."""
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import abc
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import io
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import json
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import six
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_JSON_FILE_PRIVATE_KEY = 'private_key'
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_JSON_FILE_PRIVATE_KEY_ID = 'private_key_id'
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@six.add_metaclass(abc.ABCMeta)
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class Verifier(object):
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"""Abstract base class for crytographic signature verifiers."""
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@abc.abstractmethod
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def verify(self, message, signature):
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"""Verifies a message against a cryptographic signature.
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Args:
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message (Union[str, bytes]): The message to verify.
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signature (Union[str, bytes]): The cryptography signature to check.
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Returns:
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bool: True if message was signed by the private key associated
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with the public key that this object was constructed with.
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"""
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# pylint: disable=missing-raises-doc,redundant-returns-doc
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# (pylint doesn't recognize that this is abstract)
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raise NotImplementedError('Verify must be implemented')
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@six.add_metaclass(abc.ABCMeta)
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class Signer(object):
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"""Abstract base class for cryptographic signers."""
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@abc.abstractproperty
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def key_id(self):
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"""Optional[str]: The key ID used to identify this private key."""
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raise NotImplementedError('Key id must be implemented')
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@abc.abstractmethod
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def sign(self, message):
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"""Signs a message.
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Args:
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message (Union[str, bytes]): The message to be signed.
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Returns:
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bytes: The signature of the message.
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"""
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# pylint: disable=missing-raises-doc,redundant-returns-doc
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# (pylint doesn't recognize that this is abstract)
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raise NotImplementedError('Sign must be implemented')
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@six.add_metaclass(abc.ABCMeta)
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class FromServiceAccountMixin(object):
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"""Mix-in to enable factory constructors for a Signer."""
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@abc.abstractmethod
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def from_string(cls, key, key_id=None):
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"""Construct an Signer instance from a private key string.
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Args:
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key (str): Private key as a string.
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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.Signer: The constructed signer.
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Raises:
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ValueError: If the key cannot be parsed.
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"""
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raise NotImplementedError('from_string must be implemented')
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@classmethod
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def from_service_account_info(cls, info):
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"""Creates a Signer instance instance from a dictionary containing
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service account info in Google format.
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Args:
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info (Mapping[str, str]): The service account info in Google
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format.
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Returns:
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google.auth.crypt.Signer: The constructed signer.
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Raises:
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ValueError: If the info is not in the expected format.
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"""
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if _JSON_FILE_PRIVATE_KEY not in info:
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raise ValueError(
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'The private_key field was not found in the service account '
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'info.')
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return cls.from_string(
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info[_JSON_FILE_PRIVATE_KEY],
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info.get(_JSON_FILE_PRIVATE_KEY_ID))
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@classmethod
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def from_service_account_file(cls, filename):
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"""Creates a Signer instance from a service account .json file
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in Google format.
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Args:
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filename (str): The path to the service account .json file.
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Returns:
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google.auth.crypt.Signer: The constructed signer.
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"""
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with io.open(filename, 'r', encoding='utf-8') as json_file:
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data = json.load(json_file)
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return cls.from_service_account_info(data)
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