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1# Copyright 2015 gRPC authors.
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#     http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14
15import collections
16import logging
17import threading
18
19import grpc
20from grpc import _common
21from grpc._cython import cygrpc
22
23_LOGGER = logging.getLogger(__name__)
24
25
26class _AuthMetadataContext(
27        collections.namedtuple('AuthMetadataContext', (
28            'service_url',
29            'method_name',
30        )), grpc.AuthMetadataContext):
31    pass
32
33
34class _CallbackState(object):
35
36    def __init__(self):
37        self.lock = threading.Lock()
38        self.called = False
39        self.exception = None
40
41
42class _AuthMetadataPluginCallback(grpc.AuthMetadataPluginCallback):
43
44    def __init__(self, state, callback):
45        self._state = state
46        self._callback = callback
47
48    def __call__(self, metadata, error):
49        with self._state.lock:
50            if self._state.exception is None:
51                if self._state.called:
52                    raise RuntimeError(
53                        'AuthMetadataPluginCallback invoked more than once!')
54                else:
55                    self._state.called = True
56            else:
57                raise RuntimeError(
58                    'AuthMetadataPluginCallback raised exception "{}"!'.format(
59                        self._state.exception))
60        if error is None:
61            self._callback(metadata, cygrpc.StatusCode.ok, None)
62        else:
63            self._callback(None, cygrpc.StatusCode.internal,
64                           _common.encode(str(error)))
65
66
67class _Plugin(object):
68
69    def __init__(self, metadata_plugin):
70        self._metadata_plugin = metadata_plugin
71
72    def __call__(self, service_url, method_name, callback):
73        context = _AuthMetadataContext(_common.decode(service_url),
74                                       _common.decode(method_name))
75        callback_state = _CallbackState()
76        try:
77            self._metadata_plugin(
78                context, _AuthMetadataPluginCallback(callback_state, callback))
79        except Exception as exception:  # pylint: disable=broad-except
80            _LOGGER.exception(
81                'AuthMetadataPluginCallback "%s" raised exception!',
82                self._metadata_plugin)
83            with callback_state.lock:
84                callback_state.exception = exception
85                if callback_state.called:
86                    return
87            callback(None, cygrpc.StatusCode.internal,
88                     _common.encode(str(exception)))
89
90
91def metadata_plugin_call_credentials(metadata_plugin, name):
92    if name is None:
93        try:
94            effective_name = metadata_plugin.__name__
95        except AttributeError:
96            effective_name = metadata_plugin.__class__.__name__
97    else:
98        effective_name = name
99    return grpc.CallCredentials(
100        cygrpc.MetadataPluginCallCredentials(_Plugin(metadata_plugin),
101                                             _common.encode(effective_name)))
102