160 lines
5.5 KiB
Python
160 lines
5.5 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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"""Google ID Token helpers.
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Provides support for verifying `OpenID Connect ID Tokens`_, especially ones
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generated by Google infrastructure.
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To parse and verify an ID Token issued by Google's OAuth 2.0 authorization
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server use :func:`verify_oauth2_token`. To verify an ID Token issued by
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Firebase, use :func:`verify_firebase_token`.
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A general purpose ID Token verifier is available as :func:`verify_token`.
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Example::
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from google.oauth2 import id_token
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from google.auth.transport import requests
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request = requests.Request()
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id_info = id_token.verify_oauth2_token(
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token, request, 'my-client-id.example.com')
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if id_info['iss'] != 'https://accounts.google.com':
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raise ValueError('Wrong issuer.')
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userid = id_info['sub']
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By default, this will re-fetch certificates for each verification. Because
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Google's public keys are only changed infrequently (on the order of once per
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day), you may wish to take advantage of caching to reduce latency and the
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potential for network errors. This can be accomplished using an external
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library like `CacheControl`_ to create a cache-aware
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:class:`google.auth.transport.Request`::
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import cachecontrol
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import google.auth.transport.requests
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import requests
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session = requests.session()
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cached_session = cachecontrol.CacheControl(session)
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request = google.auth.transport.requests.Request(session=cached_session)
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.. _OpenID Connect ID Token:
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http://openid.net/specs/openid-connect-core-1_0.html#IDToken
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.. _CacheControl: https://cachecontrol.readthedocs.io
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"""
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import json
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from six.moves import http_client
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from google.auth import exceptions
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from google.auth import jwt
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# The URL that provides public certificates for verifying ID tokens issued
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# by Google's OAuth 2.0 authorization server.
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_GOOGLE_OAUTH2_CERTS_URL = 'https://www.googleapis.com/oauth2/v1/certs'
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# The URL that provides public certificates for verifying ID tokens issued
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# by Firebase and the Google APIs infrastructure
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_GOOGLE_APIS_CERTS_URL = (
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'https://www.googleapis.com/robot/v1/metadata/x509'
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'/securetoken@system.gserviceaccount.com')
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def _fetch_certs(request, certs_url):
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"""Fetches certificates.
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Google-style cerificate endpoints return JSON in the format of
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``{'key id': 'x509 certificate'}``.
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Args:
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request (google.auth.transport.Request): The object used to make
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HTTP requests.
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certs_url (str): The certificate endpoint URL.
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Returns:
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Mapping[str, str]: A mapping of public key ID to x.509 certificate
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data.
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"""
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response = request(certs_url, method='GET')
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if response.status != http_client.OK:
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raise exceptions.TransportError(
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'Could not fetch certificates at {}'.format(certs_url))
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return json.loads(response.data.decode('utf-8'))
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def verify_token(id_token, request, audience=None,
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certs_url=_GOOGLE_OAUTH2_CERTS_URL):
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"""Verifies an ID token and returns the decoded token.
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Args:
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id_token (Union[str, bytes]): The encoded token.
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request (google.auth.transport.Request): The object used to make
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HTTP requests.
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audience (str): The audience that this token is intended for. If None
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then the audience is not verified.
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certs_url (str): The URL that specifies the certificates to use to
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verify the token. This URL should return JSON in the format of
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``{'key id': 'x509 certificate'}``.
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Returns:
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Mapping[str, Any]: The decoded token.
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"""
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certs = _fetch_certs(request, certs_url)
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return jwt.decode(id_token, certs=certs, audience=audience)
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def verify_oauth2_token(id_token, request, audience=None):
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"""Verifies an ID Token issued by Google's OAuth 2.0 authorization server.
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Args:
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id_token (Union[str, bytes]): The encoded token.
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request (google.auth.transport.Request): The object used to make
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HTTP requests.
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audience (str): The audience that this token is intended for. This is
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typically your application's OAuth 2.0 client ID. If None then the
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audience is not verified.
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Returns:
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Mapping[str, Any]: The decoded token.
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"""
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return verify_token(
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id_token, request, audience=audience,
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certs_url=_GOOGLE_OAUTH2_CERTS_URL)
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def verify_firebase_token(id_token, request, audience=None):
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"""Verifies an ID Token issued by Firebase Authentication.
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Args:
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id_token (Union[str, bytes]): The encoded token.
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request (google.auth.transport.Request): The object used to make
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HTTP requests.
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audience (str): The audience that this token is intended for. This is
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typically your Firebase application ID. If None then the audience
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is not verified.
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Returns:
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Mapping[str, Any]: The decoded token.
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"""
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return verify_token(
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id_token, request, audience=audience, certs_url=_GOOGLE_APIS_CERTS_URL)
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