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# Copyright 2015 Vladimir Rutsky <vladimir@rutsky.org>
#
# 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.
"""CORS configuration container class definition.
"""
import collections
import warnings
from typing import Mapping, Union, Any
from aiohttp import hdrs, web
from .urldispatcher_router_adapter import ResourcesUrlDispatcherRouterAdapter
from .abc import AbstractRouterAdapter
from .resource_options import ResourceOptions
from .preflight_handler import _PreflightHandler
__all__ = (
"CorsConfig",
)
# Positive response to Access-Control-Allow-Credentials
_TRUE = "true"
# CORS simple response headers:
# <http://www.w3.org/TR/cors/#simple-response-header>
_SIMPLE_RESPONSE_HEADERS = frozenset([
hdrs.CACHE_CONTROL,
hdrs.CONTENT_LANGUAGE,
hdrs.CONTENT_TYPE,
hdrs.EXPIRES,
hdrs.LAST_MODIFIED,
hdrs.PRAGMA
])
def _parse_config_options(
config: Mapping[str, Union[ResourceOptions, Mapping[str, Any]]]=None):
"""Parse CORS configuration (default or per-route)
:param config:
Mapping from Origin to Resource configuration (allowed headers etc)
defined either as mapping or `ResourceOptions` instance.
Raises `ValueError` if configuration is not correct.
"""
if config is None:
return {}
if not isinstance(config, collections.abc.Mapping):
raise ValueError(
"Config must be mapping, got '{}'".format(config))
parsed = {}
options_keys = {
"allow_credentials", "expose_headers", "allow_headers", "max_age"
}
for origin, options in config.items():
# TODO: check that all origins are properly formatted.
# This is not a security issue, since origin is compared as strings.
if not isinstance(origin, str):
raise ValueError(
"Origin must be string, got '{}'".format(origin))
if isinstance(options, ResourceOptions):
resource_options = options
else:
if not isinstance(options, collections.abc.Mapping):
raise ValueError(
"Origin options must be either "
"aiohttp_cors.ResourceOptions instance or mapping, "
"got '{}'".format(options))
unexpected_args = frozenset(options.keys()) - options_keys
if unexpected_args:
raise ValueError(
"Unexpected keywords in resource options: {}".format(
# pylint: disable=bad-builtin
",".join(map(str, unexpected_args))))
resource_options = ResourceOptions(**options)
parsed[origin] = resource_options
return parsed
_ConfigType = Mapping[str, Union[ResourceOptions, Mapping[str, Any]]]
class _CorsConfigImpl(_PreflightHandler):
def __init__(self,
app: web.Application,
router_adapter: AbstractRouterAdapter):
self._app = app
self._router_adapter = router_adapter
# Register hook for all responses. This hook handles CORS-related
# headers on non-preflight requests.
self._app.on_response_prepare.append(self._on_response_prepare)
def add(self,
routing_entity,
config: _ConfigType=None):
"""Enable CORS for specific route or resource.
If route is passed CORS is enabled for route's resource.
:param routing_entity:
Route or Resource for which CORS should be enabled.
:param config:
CORS options for the route.
:return: `routing_entity`.
"""
parsed_config = _parse_config_options(config)
self._router_adapter.add_preflight_handler(
routing_entity, self._preflight_handler)
self._router_adapter.set_config_for_routing_entity(
routing_entity, parsed_config)
return routing_entity
async def _on_response_prepare(self,
request: web.Request,
response: web.StreamResponse):
"""Non-preflight CORS request response processor.
If request is done on CORS-enabled route, process request parameters
and set appropriate CORS response headers.
"""
if (not self._router_adapter.is_cors_enabled_on_request(request) or
self._router_adapter.is_preflight_request(request)):
# Either not CORS enabled route, or preflight request which is
# handled in its own handler.
return
# Processing response of non-preflight CORS-enabled request.
config = self._router_adapter.get_non_preflight_request_config(request)
# Handle according to part 6.1 of the CORS specification.
origin = request.headers.get(hdrs.ORIGIN)
if origin is None:
# Terminate CORS according to CORS 6.1.1.
return
options = config.get(origin, config.get("*"))
if options is None:
# Terminate CORS according to CORS 6.1.2.
return
assert hdrs.ACCESS_CONTROL_ALLOW_ORIGIN not in response.headers
assert hdrs.ACCESS_CONTROL_ALLOW_CREDENTIALS not in response.headers
assert hdrs.ACCESS_CONTROL_EXPOSE_HEADERS not in response.headers
# Process according to CORS 6.1.4.
# Set exposed headers (server headers exposed to client) before
# setting any other headers.
if options.expose_headers == "*":
# Expose all headers that are set in response.
exposed_headers = \
frozenset(response.headers.keys()) - _SIMPLE_RESPONSE_HEADERS
response.headers[hdrs.ACCESS_CONTROL_EXPOSE_HEADERS] = \
",".join(exposed_headers)
elif options.expose_headers:
# Expose predefined list of headers.
response.headers[hdrs.ACCESS_CONTROL_EXPOSE_HEADERS] = \
",".join(options.expose_headers)
# Process according to CORS 6.1.3.
# Set allowed origin.
response.headers[hdrs.ACCESS_CONTROL_ALLOW_ORIGIN] = origin
if options.allow_credentials:
# Set allowed credentials.
response.headers[hdrs.ACCESS_CONTROL_ALLOW_CREDENTIALS] = _TRUE
async def _get_config(self, request, origin, request_method):
config = \
await self._router_adapter.get_preflight_request_config(
request, origin, request_method)
return config
class CorsConfig:
"""CORS configuration instance.
The instance holds default CORS parameters and per-route options specified
in `add()` method.
Each `aiohttp.web.Application` can have exactly one instance of this class.
"""
def __init__(self, app: web.Application, *,
defaults: _ConfigType=None,
router_adapter: AbstractRouterAdapter=None):
"""Construct CORS configuration.
:param app:
Application for which CORS configuration is built.
:param defaults:
Default CORS settings for origins.
:param router_adapter:
Router adapter. Required if application uses non-default router.
"""
self.defaults = _parse_config_options(defaults)
self._cors_impl = None
self._resources_router_adapter = None
self._resources_cors_impl = None
self._old_routes_cors_impl = None
if router_adapter is None:
router_adapter = \
ResourcesUrlDispatcherRouterAdapter(app.router, self.defaults)
self._cors_impl = _CorsConfigImpl(app, router_adapter)
def add(self,
routing_entity,
config: _ConfigType = None,
webview: bool=False):
"""Enable CORS for specific route or resource.
If route is passed CORS is enabled for route's resource.
:param routing_entity:
Route or Resource for which CORS should be enabled.
:param config:
CORS options for the route.
:return: `routing_entity`.
"""
if webview:
warnings.warn('webview argument is deprecated, '
'views are handled authomatically without '
'extra settings',
DeprecationWarning,
stacklevel=2)
return self._cors_impl.add(routing_entity, config)
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