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| # Copyright 2020 The TensorFlow Authors. 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. | |
| # ============================================================================== | |
| """Experimental framework for authentication in TensorBoard.""" | |
| import abc | |
| class AuthProvider(metaclass=abc.ABCMeta): | |
| """Authentication provider for a specific kind of credential.""" | |
| def authenticate(self, environ): | |
| """Produce an opaque auth token from a WSGI request environment. | |
| Args: | |
| environ: A WSGI environment `dict`; see PEP 3333. | |
| Returns: | |
| A Python object representing an auth token. The representation | |
| and semantics depend on the particular `AuthProvider` | |
| implementation. | |
| Raises: | |
| Exception: Any error, usually `tensorboard.errors.PublicError` | |
| subclasses (like `PermissionDenied`) but also possibly a | |
| custom error type that should propagate to a WSGI middleware | |
| for effecting a redirect-driven auth flow. | |
| """ | |
| pass | |
| class AuthContext: | |
| """Authentication context within the scope of a single request. | |
| Auth providers are keyed within an `AuthContext` by arbitrary | |
| unique keys. It may often make sense for the key used for an | |
| auth provider to simply be that provider's type object. | |
| """ | |
| def __init__(self, providers, environ): | |
| """Create an auth context. | |
| Args: | |
| providers: A mapping from provider keys (opaque values) to | |
| `AuthProvider` implementations. | |
| environ: A WSGI environment (see PEP 3333). | |
| """ | |
| self._environ = environ | |
| self._providers = providers | |
| self._cache = {} | |
| def empty(cls): | |
| """Create an auth context with no registered providers. | |
| Returns: | |
| A new `AuthContext` value for which any call to `get` will | |
| fail with a `KeyError`. | |
| """ | |
| # Use an empty dict for the environ. This is not a valid WSGI | |
| # environment, but it doesn't matter because it's never used. | |
| return cls({}, {}) | |
| def get(self, provider_key): | |
| """Get an auth token from the auth provider with the given key. | |
| If successful, the result will be cached on this auth context. | |
| If unsuccessful, nothing will be cached, so a future call will | |
| invoke the underlying `AuthProvider.authenticate` method again. | |
| This method is not thread-safe. If multiple threads share an | |
| auth context for a single request, then they must synchronize | |
| externally when calling this method. | |
| Returns: | |
| The result of `provider.authenticate(...)` for the auth | |
| provider specified by `provider_key`. | |
| Raises: | |
| KeyError: If the given `provider_key` does not correspond to | |
| any registered `AuthProvider`. | |
| Exception: As raised by the underlying `AuthProvider`. | |
| """ | |
| provider = self._providers[provider_key] | |
| sentinel = object() | |
| value = self._cache.get(provider_key, sentinel) | |
| if value is not sentinel: | |
| return value | |
| value = provider.authenticate(self._environ) | |
| self._cache[provider_key] = value | |
| return value | |