542 lines
18 KiB
Python
542 lines
18 KiB
Python
# Copyright (C) 2010 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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"""Utilities for Google App Engine
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Utilities for making it easier to use OAuth 2.0 on Google App Engine.
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"""
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__author__ = 'jcgregorio@google.com (Joe Gregorio)'
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import base64
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import httplib2
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import logging
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import pickle
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import time
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try: # pragma: no cover
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import simplejson
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except ImportError: # pragma: no cover
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try:
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# Try to import from django, should work on App Engine
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from django.utils import simplejson
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except ImportError:
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# Should work for Python2.6 and higher.
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import json as simplejson
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import clientsecrets
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from client import AccessTokenRefreshError
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from client import AssertionCredentials
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from client import Credentials
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from client import Flow
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from client import OAuth2WebServerFlow
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from client import Storage
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from google.appengine.api import memcache
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from google.appengine.api import users
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from google.appengine.api.app_identity import app_identity
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from google.appengine.ext import db
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from google.appengine.ext import webapp
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from google.appengine.ext.webapp.util import login_required
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from google.appengine.ext.webapp.util import run_wsgi_app
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OAUTH2CLIENT_NAMESPACE = 'oauth2client#ns'
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class InvalidClientSecretsError(Exception):
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"""The client_secrets.json file is malformed or missing required fields."""
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pass
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class AppAssertionCredentials(AssertionCredentials):
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"""Credentials object for App Engine Assertion Grants
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This object will allow an App Engine application to identify itself to Google
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and other OAuth 2.0 servers that can verify assertions. It can be used for
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the purpose of accessing data stored under an account assigned to the App
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Engine application itself. The algorithm used for generating the assertion is
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the Signed JSON Web Token (JWT) algorithm. Additional details can be found at
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the following link:
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http://self-issued.info/docs/draft-jones-json-web-token.html
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This credential does not require a flow to instantiate because it represents
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a two legged flow, and therefore has all of the required information to
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generate and refresh its own access tokens.
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"""
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def __init__(self, scope,
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audience='https://accounts.google.com/o/oauth2/token',
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assertion_type='http://oauth.net/grant_type/jwt/1.0/bearer',
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token_uri='https://accounts.google.com/o/oauth2/token', **kwargs):
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"""Constructor for AppAssertionCredentials
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Args:
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scope: string, scope of the credentials being requested.
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audience: string, The audience, or verifier of the assertion. For
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convenience defaults to Google's audience.
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assertion_type: string, Type name that will identify the format of the
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assertion string. For convience, defaults to the JSON Web Token (JWT)
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assertion type string.
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token_uri: string, URI for token endpoint. For convenience
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defaults to Google's endpoints but any OAuth 2.0 provider can be used.
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"""
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self.scope = scope
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self.audience = audience
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self.app_name = app_identity.get_service_account_name()
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super(AppAssertionCredentials, self).__init__(
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assertion_type,
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None,
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token_uri)
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@classmethod
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def from_json(cls, json):
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data = simplejson.loads(json)
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retval = AccessTokenCredentials(
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data['scope'],
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data['audience'],
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data['assertion_type'],
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data['token_uri'])
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return retval
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def _generate_assertion(self):
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header = {
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'typ': 'JWT',
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'alg': 'RS256',
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}
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now = int(time.time())
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claims = {
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'aud': self.audience,
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'scope': self.scope,
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'iat': now,
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'exp': now + 3600,
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'iss': self.app_name,
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}
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jwt_components = [base64.b64encode(simplejson.dumps(seg))
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for seg in [header, claims]]
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base_str = ".".join(jwt_components)
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key_name, signature = app_identity.sign_blob(base_str)
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jwt_components.append(base64.b64encode(signature))
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return ".".join(jwt_components)
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class FlowProperty(db.Property):
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"""App Engine datastore Property for Flow.
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Utility property that allows easy storage and retreival of an
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oauth2client.Flow"""
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# Tell what the user type is.
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data_type = Flow
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# For writing to datastore.
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def get_value_for_datastore(self, model_instance):
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flow = super(FlowProperty,
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self).get_value_for_datastore(model_instance)
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return db.Blob(pickle.dumps(flow))
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# For reading from datastore.
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def make_value_from_datastore(self, value):
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if value is None:
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return None
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return pickle.loads(value)
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def validate(self, value):
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if value is not None and not isinstance(value, Flow):
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raise db.BadValueError('Property %s must be convertible '
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'to a FlowThreeLegged instance (%s)' %
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(self.name, value))
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return super(FlowProperty, self).validate(value)
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def empty(self, value):
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return not value
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class CredentialsProperty(db.Property):
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"""App Engine datastore Property for Credentials.
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Utility property that allows easy storage and retrieval of
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oath2client.Credentials
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"""
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# Tell what the user type is.
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data_type = Credentials
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# For writing to datastore.
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def get_value_for_datastore(self, model_instance):
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logging.info("get: Got type " + str(type(model_instance)))
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cred = super(CredentialsProperty,
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self).get_value_for_datastore(model_instance)
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if cred is None:
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cred = ''
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else:
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cred = cred.to_json()
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return db.Blob(cred)
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# For reading from datastore.
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def make_value_from_datastore(self, value):
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logging.info("make: Got type " + str(type(value)))
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if value is None:
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return None
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if len(value) == 0:
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return None
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try:
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credentials = Credentials.new_from_json(value)
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except ValueError:
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credentials = None
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return credentials
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def validate(self, value):
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value = super(CredentialsProperty, self).validate(value)
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logging.info("validate: Got type " + str(type(value)))
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if value is not None and not isinstance(value, Credentials):
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raise db.BadValueError('Property %s must be convertible '
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'to a Credentials instance (%s)' %
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(self.name, value))
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#if value is not None and not isinstance(value, Credentials):
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# return None
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return value
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class StorageByKeyName(Storage):
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"""Store and retrieve a single credential to and from
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the App Engine datastore.
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This Storage helper presumes the Credentials
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have been stored as a CredenialsProperty
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on a datastore model class, and that entities
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are stored by key_name.
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"""
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def __init__(self, model, key_name, property_name, cache=None):
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"""Constructor for Storage.
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Args:
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model: db.Model, model class
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key_name: string, key name for the entity that has the credentials
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property_name: string, name of the property that is a CredentialsProperty
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cache: memcache, a write-through cache to put in front of the datastore
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"""
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self._model = model
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self._key_name = key_name
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self._property_name = property_name
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self._cache = cache
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def locked_get(self):
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"""Retrieve Credential from datastore.
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Returns:
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oauth2client.Credentials
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"""
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if self._cache:
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json = self._cache.get(self._key_name)
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if json:
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return Credentials.new_from_json(json)
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entity = self._model.get_or_insert(self._key_name)
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credential = getattr(entity, self._property_name)
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if credential and hasattr(credential, 'set_store'):
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credential.set_store(self)
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if self._cache:
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self._cache.set(self._key_name, credentials.to_json())
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return credential
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def locked_put(self, credentials):
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"""Write a Credentials to the datastore.
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Args:
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credentials: Credentials, the credentials to store.
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"""
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entity = self._model.get_or_insert(self._key_name)
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setattr(entity, self._property_name, credentials)
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entity.put()
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if self._cache:
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self._cache.set(self._key_name, credentials.to_json())
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class CredentialsModel(db.Model):
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"""Storage for OAuth 2.0 Credentials
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Storage of the model is keyed by the user.user_id().
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"""
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credentials = CredentialsProperty()
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class OAuth2Decorator(object):
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"""Utility for making OAuth 2.0 easier.
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Instantiate and then use with oauth_required or oauth_aware
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as decorators on webapp.RequestHandler methods.
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Example:
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decorator = OAuth2Decorator(
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client_id='837...ent.com',
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client_secret='Qh...wwI',
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scope='https://www.googleapis.com/auth/buzz')
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class MainHandler(webapp.RequestHandler):
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@decorator.oauth_required
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def get(self):
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http = decorator.http()
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# http is authorized with the user's Credentials and can be used
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# in API calls
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"""
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def __init__(self, client_id, client_secret, scope,
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auth_uri='https://accounts.google.com/o/oauth2/auth',
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token_uri='https://accounts.google.com/o/oauth2/token',
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message=None):
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"""Constructor for OAuth2Decorator
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Args:
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client_id: string, client identifier.
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client_secret: string client secret.
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scope: string or list of strings, scope(s) of the credentials being
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requested.
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auth_uri: string, URI for authorization endpoint. For convenience
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defaults to Google's endpoints but any OAuth 2.0 provider can be used.
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token_uri: string, URI for token endpoint. For convenience
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defaults to Google's endpoints but any OAuth 2.0 provider can be used.
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message: Message to display if there are problems with the OAuth 2.0
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configuration. The message may contain HTML and will be presented on the
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web interface for any method that uses the decorator.
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"""
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self.flow = OAuth2WebServerFlow(client_id, client_secret, scope, None,
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auth_uri, token_uri)
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self.credentials = None
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self._request_handler = None
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self._message = message
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self._in_error = False
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def _display_error_message(self, request_handler):
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request_handler.response.out.write('<html><body>')
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request_handler.response.out.write(self._message)
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request_handler.response.out.write('</body></html>')
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def oauth_required(self, method):
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"""Decorator that starts the OAuth 2.0 dance.
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Starts the OAuth dance for the logged in user if they haven't already
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granted access for this application.
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Args:
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method: callable, to be decorated method of a webapp.RequestHandler
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instance.
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"""
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def check_oauth(request_handler, *args):
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if self._in_error:
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self._display_error_message(request_handler)
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return
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user = users.get_current_user()
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# Don't use @login_decorator as this could be used in a POST request.
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if not user:
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request_handler.redirect(users.create_login_url(
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request_handler.request.uri))
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return
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# Store the request URI in 'state' so we can use it later
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self.flow.params['state'] = request_handler.request.url
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self._request_handler = request_handler
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self.credentials = StorageByKeyName(
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CredentialsModel, user.user_id(), 'credentials').get()
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if not self.has_credentials():
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return request_handler.redirect(self.authorize_url())
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try:
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method(request_handler, *args)
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except AccessTokenRefreshError:
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return request_handler.redirect(self.authorize_url())
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return check_oauth
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def oauth_aware(self, method):
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"""Decorator that sets up for OAuth 2.0 dance, but doesn't do it.
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Does all the setup for the OAuth dance, but doesn't initiate it.
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This decorator is useful if you want to create a page that knows
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whether or not the user has granted access to this application.
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From within a method decorated with @oauth_aware the has_credentials()
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and authorize_url() methods can be called.
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Args:
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method: callable, to be decorated method of a webapp.RequestHandler
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instance.
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"""
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def setup_oauth(request_handler, *args):
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if self._in_error:
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self._display_error_message(request_handler)
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return
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user = users.get_current_user()
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# Don't use @login_decorator as this could be used in a POST request.
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if not user:
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request_handler.redirect(users.create_login_url(
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request_handler.request.uri))
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return
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self.flow.params['state'] = request_handler.request.url
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self._request_handler = request_handler
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self.credentials = StorageByKeyName(
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CredentialsModel, user.user_id(), 'credentials').get()
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method(request_handler, *args)
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return setup_oauth
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def has_credentials(self):
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"""True if for the logged in user there are valid access Credentials.
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Must only be called from with a webapp.RequestHandler subclassed method
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that had been decorated with either @oauth_required or @oauth_aware.
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"""
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return self.credentials is not None and not self.credentials.invalid
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def authorize_url(self):
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"""Returns the URL to start the OAuth dance.
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Must only be called from with a webapp.RequestHandler subclassed method
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that had been decorated with either @oauth_required or @oauth_aware.
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"""
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callback = self._request_handler.request.relative_url('/oauth2callback')
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url = self.flow.step1_get_authorize_url(callback)
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user = users.get_current_user()
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memcache.set(user.user_id(), pickle.dumps(self.flow),
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namespace=OAUTH2CLIENT_NAMESPACE)
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return url
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def http(self):
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"""Returns an authorized http instance.
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Must only be called from within an @oauth_required decorated method, or
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from within an @oauth_aware decorated method where has_credentials()
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returns True.
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"""
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return self.credentials.authorize(httplib2.Http())
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class OAuth2DecoratorFromClientSecrets(OAuth2Decorator):
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"""An OAuth2Decorator that builds from a clientsecrets file.
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Uses a clientsecrets file as the source for all the information when
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constructing an OAuth2Decorator.
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Example:
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decorator = OAuth2DecoratorFromClientSecrets(
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os.path.join(os.path.dirname(__file__), 'client_secrets.json')
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scope='https://www.googleapis.com/auth/buzz')
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class MainHandler(webapp.RequestHandler):
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@decorator.oauth_required
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def get(self):
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http = decorator.http()
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# http is authorized with the user's Credentials and can be used
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# in API calls
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"""
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def __init__(self, filename, scope, message=None):
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"""Constructor
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Args:
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filename: string, File name of client secrets.
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scope: string, Space separated list of scopes.
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message: string, A friendly string to display to the user if the
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clientsecrets file is missing or invalid. The message may contain HTML and
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will be presented on the web interface for any method that uses the
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decorator.
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"""
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try:
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client_type, client_info = clientsecrets.loadfile(filename)
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if client_type not in [clientsecrets.TYPE_WEB, clientsecrets.TYPE_INSTALLED]:
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raise InvalidClientSecretsError('OAuth2Decorator doesn\'t support this OAuth 2.0 flow.')
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super(OAuth2DecoratorFromClientSecrets,
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self).__init__(
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client_info['client_id'],
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client_info['client_secret'],
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scope,
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client_info['auth_uri'],
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client_info['token_uri'],
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message)
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except clientsecrets.InvalidClientSecretsError:
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self._in_error = True
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if message is not None:
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self._message = message
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else:
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self._message = "Please configure your application for OAuth 2.0"
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def oauth2decorator_from_clientsecrets(filename, scope, message=None):
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"""Creates an OAuth2Decorator populated from a clientsecrets file.
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Args:
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filename: string, File name of client secrets.
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scope: string, Space separated list of scopes.
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message: string, A friendly string to display to the user if the
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clientsecrets file is missing or invalid. The message may contain HTML and
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will be presented on the web interface for any method that uses the
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decorator.
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Returns: An OAuth2Decorator
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"""
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return OAuth2DecoratorFromClientSecrets(filename, scope, message)
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class OAuth2Handler(webapp.RequestHandler):
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"""Handler for the redirect_uri of the OAuth 2.0 dance."""
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@login_required
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def get(self):
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error = self.request.get('error')
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if error:
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errormsg = self.request.get('error_description', error)
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self.response.out.write(
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'The authorization request failed: %s' % errormsg)
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else:
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user = users.get_current_user()
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flow = pickle.loads(memcache.get(user.user_id(),
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namespace=OAUTH2CLIENT_NAMESPACE))
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# This code should be ammended with application specific error
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# handling. The following cases should be considered:
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# 1. What if the flow doesn't exist in memcache? Or is corrupt?
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# 2. What if the step2_exchange fails?
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if flow:
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credentials = flow.step2_exchange(self.request.params)
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StorageByKeyName(
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CredentialsModel, user.user_id(), 'credentials').put(credentials)
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self.redirect(self.request.get('state'))
|
|
else:
|
|
# TODO Add error handling here.
|
|
pass
|
|
|
|
|
|
application = webapp.WSGIApplication([('/oauth2callback', OAuth2Handler)])
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|
|
|
|
|
def main():
|
|
run_wsgi_app(application)
|