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Add support for external IdP OIDC token retrieval for Google Cloud Op…
…erators. (apache#39873) * Add support for external IdP OIDC token retrieval using OAuth2.0 Crient Credentials Grant for Google Cloud Operators. This feature enables OIDC token retrieval from any generic Identity Provider (IdP) that uses the OAuth 2.0 Credentials Grant Flow. Additionally, it lays the groundwork for integrating other custom OIDC token retrieval methods. related: apache#35899 Co-authored-by: Gonçalo Azevedo <[email protected]> --------- Co-authored-by: Gonçalo Azevedo <[email protected]>
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airflow/providers/google/cloud/utils/external_token_supplier.py
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| # Licensed to the Apache Software Foundation (ASF) under one | ||
| # or more contributor license agreements. See the NOTICE file | ||
| # distributed with this work for additional information | ||
| # regarding copyright ownership. The ASF licenses this file | ||
| # to you 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. | ||
| from __future__ import annotations | ||
|
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| import abc | ||
| import time | ||
| from functools import wraps | ||
| from typing import TYPE_CHECKING, Any | ||
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| import requests | ||
| from google.auth.exceptions import RefreshError | ||
| from google.auth.identity_pool import SubjectTokenSupplier | ||
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| if TYPE_CHECKING: | ||
| from google.auth.external_account import SupplierContext | ||
| from google.auth.transport import Request | ||
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| from airflow.utils.log.logging_mixin import LoggingMixin | ||
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| def cache_token_decorator(get_subject_token_method): | ||
| """Cache calls to ``SubjectTokenSupplier`` instances' ``get_token_supplier`` methods. | ||
| Different instances of a same SubjectTokenSupplier class with the same attributes | ||
| share the OIDC token cache. | ||
| :param get_subject_token_method: A method that returns both a token and an integer specifying | ||
| the time in seconds until the token expires | ||
| See also: | ||
| https://googleapis.dev/python/google-auth/latest/reference/google.auth.identity_pool.html#google.auth.identity_pool.SubjectTokenSupplier.get_subject_token | ||
| """ | ||
| cache = {} | ||
|
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| @wraps(get_subject_token_method) | ||
| def wrapper(supplier_instance: CacheTokenSupplier, *args, **kwargs) -> str: | ||
| """Obeys the interface set by ``SubjectTokenSupplier`` for ``get_subject_token`` methods. | ||
| :param supplier_instance: the SubjectTokenSupplier instance whose get_subject_token method is being decorated | ||
| :return: The token string | ||
| """ | ||
| nonlocal cache | ||
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| cache_key = supplier_instance.get_subject_key() | ||
| token: dict[str, str | float] = {} | ||
|
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| if cache_key not in cache or cache[cache_key]["expiration_time"] < time.monotonic(): | ||
| supplier_instance.log.info("OIDC token missing or expired") | ||
| try: | ||
| access_token, expires_in = get_subject_token_method(supplier_instance, *args, **kwargs) | ||
| if not isinstance(expires_in, int) or not isinstance(access_token, str): | ||
| raise RefreshError # assume error if strange values are provided | ||
|
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| except RefreshError: | ||
| supplier_instance.log.error("Failed retrieving new OIDC Token from IdP") | ||
| raise | ||
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| expiration_time = time.monotonic() + float(expires_in) | ||
| token["access_token"] = access_token | ||
| token["expiration_time"] = expiration_time | ||
| cache[cache_key] = token | ||
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| supplier_instance.log.info("New OIDC token retrieved, expires in %s seconds.", expires_in) | ||
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| return cache[cache_key]["access_token"] | ||
|
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| return wrapper | ||
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| class CacheTokenSupplier(LoggingMixin, SubjectTokenSupplier): | ||
| """ | ||
| A superclass for all Subject Token Supplier classes that wish to implement a caching mechanism. | ||
| Child classes must implement the ``get_subject_key`` method to generate a string that serves as the cache key, | ||
| ensuring that tokens are shared appropriately among instances. | ||
| Methods: | ||
| get_subject_key: Abstract method to be implemented by child classes. It should return a string that serves as the cache key. | ||
| """ | ||
|
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| def __init__(self): | ||
| super().__init__() | ||
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| @abc.abstractmethod | ||
| def get_subject_key(self) -> str: | ||
| raise NotImplementedError("") | ||
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| class ClientCredentialsGrantFlowTokenSupplier(CacheTokenSupplier): | ||
| """ | ||
| Class that retrieves an OIDC token from an external IdP using OAuth2.0 Client Credentials Grant flow. | ||
| This class implements the ``SubjectTokenSupplier`` interface class used by ``google.auth.identity_pool.Credentials`` | ||
| :params oidc_issuer_url: URL of the IdP that performs OAuth2.0 Client Credentials Grant flow and returns an OIDC token. | ||
| :params client_id: Client ID of the application requesting the token | ||
| :params client_secret: Client secret of the application requesting the token | ||
| :params extra_params_kwargs: Extra parameters to be passed in the payload of the POST request to the `oidc_issuer_url` | ||
| See also: | ||
| https://googleapis.dev/python/google-auth/latest/reference/google.auth.identity_pool.html#google.auth.identity_pool.SubjectTokenSupplier | ||
| """ | ||
|
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| def __init__( | ||
| self, | ||
| oidc_issuer_url: str, | ||
| client_id: str, | ||
| client_secret: str, | ||
| **extra_params_kwargs: Any, | ||
| ) -> None: | ||
| super().__init__() | ||
| self.oidc_issuer_url = oidc_issuer_url | ||
| self.client_id = client_id | ||
| self.client_secret = client_secret | ||
| self.extra_params_kwargs = extra_params_kwargs | ||
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| @cache_token_decorator | ||
| def get_subject_token(self, context: SupplierContext, request: Request) -> tuple[str, int]: | ||
| """Perform Client Credentials Grant flow with IdP and retrieves an OIDC token and expiration time.""" | ||
| self.log.info("Requesting new OIDC token from external IdP.") | ||
| try: | ||
| response = requests.post( | ||
| self.oidc_issuer_url, | ||
| data={ | ||
| "grant_type": "client_credentials", | ||
| "client_id": self.client_id, | ||
| "client_secret": self.client_secret, | ||
| **self.extra_params_kwargs, | ||
| }, | ||
| ) | ||
| response.raise_for_status() | ||
| except requests.HTTPError as e: | ||
| raise RefreshError(str(e)) | ||
| except requests.ConnectionError as e: | ||
| raise RefreshError(str(e)) | ||
|
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| try: | ||
| response_dict = response.json() | ||
| except requests.JSONDecodeError: | ||
| raise RefreshError(f"Didn't get a json response from {self.oidc_issuer_url}") | ||
|
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| # These fields are required | ||
| if {"access_token", "expires_in"} - set(response_dict.keys()): | ||
| # TODO more information about the error can be provided in the exception by inspecting the response | ||
| raise RefreshError(f"No access token returned from {self.oidc_issuer_url}") | ||
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| return response_dict["access_token"], response_dict["expires_in"] | ||
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| def get_subject_key(self) -> str: | ||
| """ | ||
| Create a cache key using the OIDC issuer URL, client ID, client secret and additional parameters. | ||
| Instances with the same credentials will share tokens. | ||
| """ | ||
| cache_key = ( | ||
| self.oidc_issuer_url | ||
| + self.client_id | ||
| + self.client_secret | ||
| + ",".join(sorted(self.extra_params_kwargs)) | ||
| ) | ||
| return cache_key |
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