# Copyright 2014 Google Inc. All rights reserved. # # 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. """Utilities for Google App Engine Utilities for making it easier to use OAuth 2.0 on Google App Engine. """ import cgi import json import logging import os import pickle import threading from google.appengine.api import app_identity from google.appengine.api import memcache from google.appengine.api import users from google.appengine.ext import db from google.appengine.ext.webapp.util import login_required import webapp2 as webapp import oauth2client from oauth2client import _helpers from oauth2client import client from oauth2client import clientsecrets from oauth2client import transport from oauth2client.contrib import xsrfutil # This is a temporary fix for a Google internal issue. try: from oauth2client.contrib import _appengine_ndb except ImportError: # pragma: NO COVER _appengine_ndb = None logger = logging.getLogger(__name__) OAUTH2CLIENT_NAMESPACE = 'oauth2client#ns' XSRF_MEMCACHE_ID = 'xsrf_secret_key' if _appengine_ndb is None: # pragma: NO COVER CredentialsNDBModel = None CredentialsNDBProperty = None FlowNDBProperty = None _NDB_KEY = None _NDB_MODEL = None SiteXsrfSecretKeyNDB = None else: CredentialsNDBModel = _appengine_ndb.CredentialsNDBModel CredentialsNDBProperty = _appengine_ndb.CredentialsNDBProperty FlowNDBProperty = _appengine_ndb.FlowNDBProperty _NDB_KEY = _appengine_ndb.NDB_KEY _NDB_MODEL = _appengine_ndb.NDB_MODEL SiteXsrfSecretKeyNDB = _appengine_ndb.SiteXsrfSecretKeyNDB def _safe_html(s): """Escape text to make it safe to display. Args: s: string, The text to escape. Returns: The escaped text as a string. """ return cgi.escape(s, quote=1).replace("'", ''') class SiteXsrfSecretKey(db.Model): """Storage for the sites XSRF secret key. There will only be one instance stored of this model, the one used for the site. """ secret = db.StringProperty() def _generate_new_xsrf_secret_key(): """Returns a random XSRF secret key.""" return os.urandom(16).encode("hex") def xsrf_secret_key(): """Return the secret key for use for XSRF protection. If the Site entity does not have a secret key, this method will also create one and persist it. Returns: The secret key. """ secret = memcache.get(XSRF_MEMCACHE_ID, namespace=OAUTH2CLIENT_NAMESPACE) if not secret: # Load the one and only instance of SiteXsrfSecretKey. model = SiteXsrfSecretKey.get_or_insert(key_name='site') if not model.secret: model.secret = _generate_new_xsrf_secret_key() model.put() secret = model.secret memcache.add(XSRF_MEMCACHE_ID, secret, namespace=OAUTH2CLIENT_NAMESPACE) return str(secret) class AppAssertionCredentials(client.AssertionCredentials): """Credentials object for App Engine Assertion Grants This object will allow an App Engine application to identify itself to Google and other OAuth 2.0 servers that can verify assertions. It can be used for the purpose of accessing data stored under an account assigned to the App Engine application itself. This credential does not require a flow to instantiate because it represents a two legged flow, and therefore has all of the required information to generate and refresh its own access tokens. """ @_helpers.positional(2) def __init__(self, scope, **kwargs): """Constructor for AppAssertionCredentials Args: scope: string or iterable of strings, scope(s) of the credentials being requested. **kwargs: optional keyword args, including: service_account_id: service account id of the application. If None or unspecified, the default service account for the app is used. """ self.scope = _helpers.scopes_to_string(scope) self._kwargs = kwargs self.service_account_id = kwargs.get('service_account_id', None) self._service_account_email = None # Assertion type is no longer used, but still in the # parent class signature. super(AppAssertionCredentials, self).__init__(None) @classmethod def from_json(cls, json_data): data = json.loads(json_data) return AppAssertionCredentials(data['scope']) def _refresh(self, http): """Refreshes the access token. Since the underlying App Engine app_identity implementation does its own caching we can skip all the storage hoops and just to a refresh using the API. Args: http: unused HTTP object Raises: AccessTokenRefreshError: When the refresh fails. """ try: scopes = self.scope.split() (token, _) = app_identity.get_access_token( scopes, service_account_id=self.service_account_id) except app_identity.Error as e: raise client.AccessTokenRefreshError(str(e)) self.access_token = token @property def serialization_data(self): raise NotImplementedError('Cannot serialize credentials ' 'for Google App Engine.') def create_scoped_required(self): return not self.scope def create_scoped(self, scopes): return AppAssertionCredentials(scopes, **self._kwargs) def sign_blob(self, blob): """Cryptographically sign a blob (of bytes). Implements abstract method :meth:`oauth2client.client.AssertionCredentials.sign_blob`. Args: blob: bytes, Message to be signed. Returns: tuple, A pair of the private key ID used to sign the blob and the signed contents. """ return app_identity.sign_blob(blob) @property def service_account_email(self): """Get the email for the current service account. Returns: string, The email associated with the Google App Engine service account. """ if self._service_account_email is None: self._service_account_email = ( app_identity.get_service_account_name()) return self._service_account_email class FlowProperty(db.Property): """App Engine datastore Property for Flow. Utility property that allows easy storage and retrieval of an oauth2client.Flow """ # Tell what the user type is. data_type = client.Flow # For writing to datastore. def get_value_for_datastore(self, model_instance): flow = super(FlowProperty, self).get_value_for_datastore( model_instance) return db.Blob(pickle.dumps(flow)) # For reading from datastore. def make_value_from_datastore(self, value): if value is None: return None return pickle.loads(value) def validate(self, value): if value is not None and not isinstance(value, client.Flow): raise db.BadValueError( 'Property {0} must be convertible ' 'to a FlowThreeLegged instance ({1})'.format(self.name, value)) return super(FlowProperty, self).validate(value) def empty(self, value): return not value class CredentialsProperty(db.Property): """App Engine datastore Property for Credentials. Utility property that allows easy storage and retrieval of oauth2client.Credentials """ # Tell what the user type is. data_type = client.Credentials # For writing to datastore. def get_value_for_datastore(self, model_instance): logger.info("get: Got type " + str(type(model_instance))) cred = super(CredentialsProperty, self).get_value_for_datastore( model_instance) if cred is None: cred = '' else: cred = cred.to_json() return db.Blob(cred) # For reading from datastore. def make_value_from_datastore(self, value): logger.info("make: Got type " + str(type(value))) if value is None: return None if len(value) == 0: return None try: credentials = client.Credentials.new_from_json(value) except ValueError: credentials = None return credentials def validate(self, value): value = super(CredentialsProperty, self).validate(value) logger.info("validate: Got type " + str(type(value))) if value is not None and not isinstance(value, client.Credentials): raise db.BadValueError( 'Property {0} must be convertible ' 'to a Credentials instance ({1})'.format(self.name, value)) return value class StorageByKeyName(client.Storage): """Store and retrieve a credential to and from the App Engine datastore. This Storage helper presumes the Credentials have been stored as a CredentialsProperty or CredentialsNDBProperty on a datastore model class, and that entities are stored by key_name. """ @_helpers.positional(4) def __init__(self, model, key_name, property_name, cache=None, user=None): """Constructor for Storage. Args: model: db.Model or ndb.Model, model class key_name: string, key name for the entity that has the credentials property_name: string, name of the property that is a CredentialsProperty or CredentialsNDBProperty. cache: memcache, a write-through cache to put in front of the datastore. If the model you are using is an NDB model, using a cache will be redundant since the model uses an instance cache and memcache for you. user: users.User object, optional. Can be used to grab user ID as a key_name if no key name is specified. """ super(StorageByKeyName, self).__init__() if key_name is None: if user is None: raise ValueError('StorageByKeyName called with no ' 'key name or user.') key_name = user.user_id() self._model = model self._key_name = key_name self._property_name = property_name self._cache = cache def _is_ndb(self): """Determine whether the model of the instance is an NDB model. Returns: Boolean indicating whether or not the model is an NDB or DB model. """ # issubclass will fail if one of the arguments is not a class, only # need worry about new-style classes since ndb and db models are # new-style if isinstance(self._model, type): if _NDB_MODEL is not None and issubclass(self._model, _NDB_MODEL): return True elif issubclass(self._model, db.Model): return False raise TypeError( 'Model class not an NDB or DB model: {0}.'.format(self._model)) def _get_entity(self): """Retrieve entity from datastore. Uses a different model method for db or ndb models. Returns: Instance of the model corresponding to the current storage object and stored using the key name of the storage object. """ if self._is_ndb(): return self._model.get_by_id(self._key_name) else: return self._model.get_by_key_name(self._key_name) def _delete_entity(self): """Delete entity from datastore. Attempts to delete using the key_name stored on the object, whether or not the given key is in the datastore. """ if self._is_ndb(): _NDB_KEY(self._model, self._key_name).delete() else: entity_key = db.Key.from_path(self._model.kind(), self._key_name) db.delete(entity_key) @db.non_transactional(allow_existing=True) def locked_get(self): """Retrieve Credential from datastore. Returns: oauth2client.Credentials """ credentials = None if self._cache: json = self._cache.get(self._key_name) if json: credentials = client.Credentials.new_from_json(json) if credentials is None: entity = self._get_entity() if entity is not None: credentials = getattr(entity, self._property_name) if self._cache: self._cache.set(self._key_name, credentials.to_json()) if credentials and hasattr(credentials, 'set_store'): credentials.set_store(self) return credentials @db.non_transactional(allow_existing=True) def locked_put(self, credentials): """Write a Credentials to the datastore. Args: credentials: Credentials, the credentials to store. """ entity = self._model.get_or_insert(self._key_name) setattr(entity, self._property_name, credentials) entity.put() if self._cache: self._cache.set(self._key_name, credentials.to_json()) @db.non_transactional(allow_existing=True) def locked_delete(self): """Delete Credential from datastore.""" if self._cache: self._cache.delete(self._key_name) self._delete_entity() class CredentialsModel(db.Model): """Storage for OAuth 2.0 Credentials Storage of the model is keyed by the user.user_id(). """ credentials = CredentialsProperty() def _build_state_value(request_handler, user): """Composes the value for the 'state' parameter. Packs the current request URI and an XSRF token into an opaque string that can be passed to the authentication server via the 'state' parameter. Args: request_handler: webapp.RequestHandler, The request. user: google.appengine.api.users.User, The current user. Returns: The state value as a string. """ uri = request_handler.request.url token = xsrfutil.generate_token(xsrf_secret_key(), user.user_id(), action_id=str(uri)) return uri + ':' + token def _parse_state_value(state, user): """Parse the value of the 'state' parameter. Parses the value and validates the XSRF token in the state parameter. Args: state: string, The value of the state parameter. user: google.appengine.api.users.User, The current user. Returns: The redirect URI, or None if XSRF token is not valid. """ uri, token = state.rsplit(':', 1) if xsrfutil.validate_token(xsrf_secret_key(), token, user.user_id(), action_id=uri): return uri else: return None class OAuth2Decorator(object): """Utility for making OAuth 2.0 easier. Instantiate and then use with oauth_required or oauth_aware as decorators on webapp.RequestHandler methods. :: decorator = OAuth2Decorator( client_id='837...ent.com', client_secret='Qh...wwI', scope='https://www.googleapis.com/auth/plus') class MainHandler(webapp.RequestHandler): @decorator.oauth_required def get(self): http = decorator.http() # http is authorized with the user's Credentials and can be # used in API calls """ def set_credentials(self, credentials): self._tls.credentials = credentials def get_credentials(self): """A thread local Credentials object. Returns: A client.Credentials object, or None if credentials hasn't been set in this thread yet, which may happen when calling has_credentials inside oauth_aware. """ return getattr(self._tls, 'credentials', None) credentials = property(get_credentials, set_credentials) def set_flow(self, flow): self._tls.flow = flow def get_flow(self): """A thread local Flow object. Returns: A credentials.Flow object, or None if the flow hasn't been set in this thread yet, which happens in _create_flow() since Flows are created lazily. """ return getattr(self._tls, 'flow', None) flow = property(get_flow, set_flow) @_helpers.positional(4) def __init__(self, client_id, client_secret, scope, auth_uri=oauth2client.GOOGLE_AUTH_URI, token_uri=oauth2client.GOOGLE_TOKEN_URI, revoke_uri=oauth2client.GOOGLE_REVOKE_URI, user_agent=None, message=None, callback_path='/oauth2callback', token_response_param=None, _storage_class=StorageByKeyName, _credentials_class=CredentialsModel, _credentials_property_name='credentials', **kwargs): """Constructor for OAuth2Decorator Args: client_id: string, client identifier. client_secret: string client secret. scope: string or iterable of strings, scope(s) of the credentials being requested. auth_uri: string, URI for authorization endpoint. For convenience defaults to Google's endpoints but any OAuth 2.0 provider can be used. token_uri: string, URI for token endpoint. For convenience defaults to Google's endpoints but any OAuth 2.0 provider can be used. revoke_uri: string, URI for revoke endpoint. For convenience defaults to Google's endpoints but any OAuth 2.0 provider can be used. user_agent: string, User agent of your application, default to None. message: Message to display if there are problems with the OAuth 2.0 configuration. The message may contain HTML and will be presented on the web interface for any method that uses the decorator. callback_path: string, The absolute path to use as the callback URI. Note that this must match up with the URI given when registering the application in the APIs Console. token_response_param: string. If provided, the full JSON response to the access token request will be encoded and included in this query parameter in the callback URI. This is useful with providers (e.g. wordpress.com) that include extra fields that the client may want. _storage_class: "Protected" keyword argument not typically provided to this constructor. A storage class to aid in storing a Credentials object for a user in the datastore. Defaults to StorageByKeyName. _credentials_class: "Protected" keyword argument not typically provided to this constructor. A db or ndb Model class to hold credentials. Defaults to CredentialsModel. _credentials_property_name: "Protected" keyword argument not typically provided to this constructor. A string indicating the name of the field on the _credentials_class where a Credentials object will be stored. Defaults to 'credentials'. **kwargs: dict, Keyword arguments are passed along as kwargs to the OAuth2WebServerFlow constructor. """ self._tls = threading.local() self.flow = None self.credentials = None self._client_id = client_id self._client_secret = client_secret self._scope = _helpers.scopes_to_string(scope) self._auth_uri = auth_uri self._token_uri = token_uri self._revoke_uri = revoke_uri self._user_agent = user_agent self._kwargs = kwargs self._message = message self._in_error = False self._callback_path = callback_path self._token_response_param = token_response_param self._storage_class = _storage_class self._credentials_class = _credentials_class self._credentials_property_name = _credentials_property_name def _display_error_message(self, request_handler): request_handler.response.out.write('') request_handler.response.out.write(_safe_html(self._message)) request_handler.response.out.write('') def oauth_required(self, method): """Decorator that starts the OAuth 2.0 dance. Starts the OAuth dance for the logged in user if they haven't already granted access for this application. Args: method: callable, to be decorated method of a webapp.RequestHandler instance. """ def check_oauth(request_handler, *args, **kwargs): if self._in_error: self._display_error_message(request_handler) return user = users.get_current_user() # Don't use @login_decorator as this could be used in a # POST request. if not user: request_handler.redirect(users.create_login_url( request_handler.request.uri)) return self._create_flow(request_handler) # Store the request URI in 'state' so we can use it later self.flow.params['state'] = _build_state_value( request_handler, user) self.credentials = self._storage_class( self._credentials_class, None, self._credentials_property_name, user=user).get() if not self.has_credentials(): return request_handler.redirect(self.authorize_url()) try: resp = method(request_handler, *args, **kwargs) except client.AccessTokenRefreshError: return request_handler.redirect(self.authorize_url()) finally: self.credentials = None return resp return check_oauth def _create_flow(self, request_handler): """Create the Flow object. The Flow is calculated lazily since we don't know where this app is running until it receives a request, at which point redirect_uri can be calculated and then the Flow object can be constructed. Args: request_handler: webapp.RequestHandler, the request handler. """ if self.flow is None: redirect_uri = request_handler.request.relative_url( self._callback_path) # Usually /oauth2callback self.flow = client.OAuth2WebServerFlow( self._client_id, self._client_secret, self._scope, redirect_uri=redirect_uri, user_agent=self._user_agent, auth_uri=self._auth_uri, token_uri=self._token_uri, revoke_uri=self._revoke_uri, **self._kwargs) def oauth_aware(self, method): """Decorator that sets up for OAuth 2.0 dance, but doesn't do it. Does all the setup for the OAuth dance, but doesn't initiate it. This decorator is useful if you want to create a page that knows whether or not the user has granted access to this application. From within a method decorated with @oauth_aware the has_credentials() and authorize_url() methods can be called. Args: method: callable, to be decorated method of a webapp.RequestHandler instance. """ def setup_oauth(request_handler, *args, **kwargs): if self._in_error: self._display_error_message(request_handler) return user = users.get_current_user() # Don't use @login_decorator as this could be used in a # POST request. if not user: request_handler.redirect(users.create_login_url( request_handler.request.uri)) return self._create_flow(request_handler) self.flow.params['state'] = _build_state_value(request_handler, user) self.credentials = self._storage_class( self._credentials_class, None, self._credentials_property_name, user=user).get() try: resp = method(request_handler, *args, **kwargs) finally: self.credentials = None return resp return setup_oauth def has_credentials(self): """True if for the logged in user there are valid access Credentials. Must only be called from with a webapp.RequestHandler subclassed method that had been decorated with either @oauth_required or @oauth_aware. """ return self.credentials is not None and not self.credentials.invalid def authorize_url(self): """Returns the URL to start the OAuth dance. Must only be called from with a webapp.RequestHandler subclassed method that had been decorated with either @oauth_required or @oauth_aware. """ url = self.flow.step1_get_authorize_url() return str(url) def http(self, *args, **kwargs): """Returns an authorized http instance. Must only be called from within an @oauth_required decorated method, or from within an @oauth_aware decorated method where has_credentials() returns True. Args: *args: Positional arguments passed to httplib2.Http constructor. **kwargs: Positional arguments passed to httplib2.Http constructor. """ return self.credentials.authorize( transport.get_http_object(*args, **kwargs)) @property def callback_path(self): """The absolute path where the callback will occur. Note this is the absolute path, not the absolute URI, that will be calculated by the decorator at runtime. See callback_handler() for how this should be used. Returns: The callback path as a string. """ return self._callback_path def callback_handler(self): """RequestHandler for the OAuth 2.0 redirect callback. Usage:: app = webapp.WSGIApplication([ ('/index', MyIndexHandler), ..., (decorator.callback_path, decorator.callback_handler()) ]) Returns: A webapp.RequestHandler that handles the redirect back from the server during the OAuth 2.0 dance. """ decorator = self class OAuth2Handler(webapp.RequestHandler): """Handler for the redirect_uri of the OAuth 2.0 dance.""" @login_required def get(self): error = self.request.get('error') if error: errormsg = self.request.get('error_description', error) self.response.out.write( 'The authorization request failed: {0}'.format( _safe_html(errormsg))) else: user = users.get_current_user() decorator._create_flow(self) credentials = decorator.flow.step2_exchange( self.request.params) decorator._storage_class( decorator._credentials_class, None, decorator._credentials_property_name, user=user).put(credentials) redirect_uri = _parse_state_value( str(self.request.get('state')), user) if redirect_uri is None: self.response.out.write( 'The authorization request failed') return if (decorator._token_response_param and credentials.token_response): resp_json = json.dumps(credentials.token_response) redirect_uri = _helpers._add_query_parameter( redirect_uri, decorator._token_response_param, resp_json) self.redirect(redirect_uri) return OAuth2Handler def callback_application(self): """WSGI application for handling the OAuth 2.0 redirect callback. If you need finer grained control use `callback_handler` which returns just the webapp.RequestHandler. Returns: A webapp.WSGIApplication that handles the redirect back from the server during the OAuth 2.0 dance. """ return webapp.WSGIApplication([ (self.callback_path, self.callback_handler()) ]) class OAuth2DecoratorFromClientSecrets(OAuth2Decorator): """An OAuth2Decorator that builds from a clientsecrets file. Uses a clientsecrets file as the source for all the information when constructing an OAuth2Decorator. :: decorator = OAuth2DecoratorFromClientSecrets( os.path.join(os.path.dirname(__file__), 'client_secrets.json') scope='https://www.googleapis.com/auth/plus') class MainHandler(webapp.RequestHandler): @decorator.oauth_required def get(self): http = decorator.http() # http is authorized with the user's Credentials and can be # used in API calls """ @_helpers.positional(3) def __init__(self, filename, scope, message=None, cache=None, **kwargs): """Constructor Args: filename: string, File name of client secrets. scope: string or iterable of strings, scope(s) of the credentials being requested. message: string, A friendly string to display to the user if the clientsecrets file is missing or invalid. The message may contain HTML and will be presented on the web interface for any method that uses the decorator. cache: An optional cache service client that implements get() and set() methods. See clientsecrets.loadfile() for details. **kwargs: dict, Keyword arguments are passed along as kwargs to the OAuth2WebServerFlow constructor. """ client_type, client_info = clientsecrets.loadfile(filename, cache=cache) if client_type not in (clientsecrets.TYPE_WEB, clientsecrets.TYPE_INSTALLED): raise clientsecrets.InvalidClientSecretsError( "OAuth2Decorator doesn't support this OAuth 2.0 flow.") constructor_kwargs = dict(kwargs) constructor_kwargs.update({ 'auth_uri': client_info['auth_uri'], 'token_uri': client_info['token_uri'], 'message': message, }) revoke_uri = client_info.get('revoke_uri') if revoke_uri is not None: constructor_kwargs['revoke_uri'] = revoke_uri super(OAuth2DecoratorFromClientSecrets, self).__init__( client_info['client_id'], client_info['client_secret'], scope, **constructor_kwargs) if message is not None: self._message = message else: self._message = 'Please configure your application for OAuth 2.0.' @_helpers.positional(2) def oauth2decorator_from_clientsecrets(filename, scope, message=None, cache=None): """Creates an OAuth2Decorator populated from a clientsecrets file. Args: filename: string, File name of client secrets. scope: string or list of strings, scope(s) of the credentials being requested. message: string, A friendly string to display to the user if the clientsecrets file is missing or invalid. The message may contain HTML and will be presented on the web interface for any method that uses the decorator. cache: An optional cache service client that implements get() and set() methods. See clientsecrets.loadfile() for details. Returns: An OAuth2Decorator """ return OAuth2DecoratorFromClientSecrets(filename, scope, message=message, cache=cache)