"""Base OAuth flow views. Clients should use the individual site modules.
Example usage:
app = Flask()
app.add_url_rule('/start',
view_func=twitter.Start.as_view('start', '/callback'),
methods=['POST'])
app.add_url_rule('/callback',
view_func=twitter.Callback.as_view('callback', '/after'))
"""
import logging
import urllib.parse
import flask
from flask import request
from flask.views import View
from .webutil import util
[docs]class BaseView(View):
"""Base view class. Provides the to() factory method.
Attributes (some may be overridden by subclasses):
DEFAULT_SCOPE: string, default OAuth scope(s) to request
SCOPE_SEPARATOR: string, used to separate multiple scopes
LABEL: string, human-readable label, eg 'Blogger'
NAME: string module name; usually same as `__name__.split('.')[-1]`
to_path: the base redirect URL path for the OAuth callback
scope: OAuth scopes string, comma-separated
"""
DEFAULT_SCOPE = ''
SCOPE_SEPARATOR = ','
LABEL = None
NAME = None
to_path = None
scope = None
def __init__(self, to_path, scopes=None):
super().__init__()
assert to_path
self.to_path = to_path
self.scope = self.make_scope_str(scopes)
[docs] @classmethod
def make_scope_str(cls, extra):
"""Returns an OAuth scopes query parameter value.
Combines DEFAULT_SCOPE and extra.
Args:
extra: string, sequence of strings, or None
"""
if not extra:
return cls.DEFAULT_SCOPE
if not isinstance(extra, str):
extra = cls.SCOPE_SEPARATOR.join(extra)
return cls.SCOPE_SEPARATOR.join(util.trim_nulls((cls.DEFAULT_SCOPE, extra)))
[docs] def to_url(self, state=None):
"""Returns a fully qualified callback URL based on to_path.
Includes scheme, host, and optional state.
"""
url = urllib.parse.urljoin(request.host_url, self.to_path)
if state:
# unquote first or state will be double-quoted
state = urllib.parse.unquote_plus(state)
url = util.add_query_params(url, [('state', state)])
return url
[docs] def request_url_with_state(self):
"""Returns the current request URL, with the state query param if provided.
"""
state = request.values.get('state')
if state:
return util.add_query_params(request.base_url, [('state', state)])
else:
return request.base_url
[docs]class Start(BaseView):
"""Base class for starting an OAuth flow.
Users should use the to() class method when using this view in a WSGI
application. See the file docstring for details.
If the 'state' query parameter is provided in the request data, it will be
returned to the client in the OAuth callback view. If the 'scope' query
parameter is provided, it will be added to the existing OAuth scopes.
Alternatively, clients may call redirect_url() and HTTP 302 redirect to it
manually, which will start the same OAuth flow.
"""
[docs] def dispatch_request(self):
scopes = set(request.values.getlist('scope'))
if self.scope:
scopes.add(self.scope)
self.scope = self.SCOPE_SEPARATOR.join(util.trim_nulls(scopes))
# str() is since WSGI middleware chokes on unicode redirect URLs :/ eg:
# InvalidResponseError: header values must be str, got 'unicode' (u'...') for 'Location'
# https://console.cloud.google.com/errors/CPafw-Gq18CrnwE
url = str(self.redirect_url(state=request.values.get('state')))
logging.info('Starting OAuth flow: redirecting to %s', url)
return flask.redirect(url)
[docs] def redirect_url(self, state=None):
"""Returns the local URL for the OAuth service to redirect back to.
oauth-dropin subclasses must implement this.
Args:
state: string, user-provided value to be returned as a query parameter in
the return redirect
"""
raise NotImplementedError()
[docs]class Callback(BaseView):
"""Base OAuth callback view.
Users can use the to() class method when using this view in a WSGI
application to make it redirect to a given URL path on completion. See the
file docstring for details.
Alternatively, you can subclass it and implement finish(), which will be
called in the OAuth callback request directly, after the user has been
authenticated.
The auth entity and optional state parameter provided to Start will be
passed to finish() or as query parameters to the redirect URL.
"""
[docs] def finish(self, auth_entity, state=None):
"""Called when the OAuth flow is complete. Clients may override.
Args:
auth_entity: a site-specific subclass of models.BaseAuth, or None if the
user declined the site's OAuth authorization request.
state: the string passed to Start.redirect_url()
Returns: :class:`werkzeug.wrappers.Response`
"""
if auth_entity is None:
params = [('declined', True)]
else:
params = [('auth_entity', auth_entity.key.urlsafe().decode()),
('state', state)]
try:
token = auth_entity.access_token()
if isinstance(token, str):
params.append(('access_token', token))
elif token:
params += [('access_token_key', token[0]),
('access_token_secret', token[1])]
except NotImplementedError:
logging.info('access_token() not implemented')
try:
token = auth_entity.refresh_token
params.append(('refresh_token', token))
except AttributeError:
logging.info('refresh_token not included')
url = util.add_query_params(self.to_path, params)
logging.info('Finishing OAuth flow: redirecting to %s', url)
return flask.redirect(url)
