docs: migrate samples from googleapis/google-auth-library-python

auth/cloud-client-temp/authenticate_explicit_with_adc.py

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+# Copyright 2022 Google LLC
+#
+# 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.
+
+# [START auth_cloud_explicit_adc]
+
+
+import google.auth
+from google.cloud import storage
+import google.oauth2.credentials
+
+
+def authenticate_explicit_with_adc() -> None:
+    """
+    List storage buckets by authenticating with ADC.
+
+    // TODO(Developer):
+    //  1. Before running this sample,
+    //  set up ADC as described in https://cloud.google.com/docs/authentication/external/set-up-adc
+    //  2. Replace the project variable.
+    //  3. Make sure you have the necessary permission to list storage buckets: "storage.buckets.list"
+    """
+
+    # Construct the Google credentials object which obtains the default configuration from your
+    # working environment.
+    # google.auth.default() will give you ComputeEngineCredentials
+    # if you are on a GCE (or other metadata server supported environments).
+    credentials, project_id = google.auth.default()
+    # If you are authenticating to a Cloud API, you can let the library include the default scope,
+    # https://www.googleapis.com/auth/cloud-platform, because IAM is used to provide fine-grained
+    # permissions for Cloud.
+    # If you need to provide a scope, specify it as follows:
+    # credentials = google.auth.default(scopes=scope)
+    # For more information on scopes to use,
+    # see: https://developers.google.com/identity/protocols/oauth2/scopes
+
+    # Construct the Storage client.
+    storage_client = storage.Client(credentials=credentials, project=project_id)
+    buckets = storage_client.list_buckets()
+    print("Buckets:")
+    for bucket in buckets:
+        print(bucket.name)
+    print("Listed all storage buckets.")
+
+# [END auth_cloud_explicit_adc]

auth/cloud-client-temp/authenticate_implicit_with_adc.py

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+# Copyright 2022 Google LLC
+#
+# 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.
+
+# [START auth_cloud_implicit_adc]
+
+from google.cloud import storage
+
+
+def authenticate_implicit_with_adc(project_id: str = "your-google-cloud-project-id") -> None:
+    """
+    When interacting with Google Cloud Client libraries, the library can auto-detect the
+    credentials to use.
+
+    // TODO(Developer):
+    //  1. Before running this sample,
+    //  set up ADC as described in https://cloud.google.com/docs/authentication/external/set-up-adc
+    //  2. Replace the project variable.
+    //  3. Make sure that the user account or service account that you are using
+    //  has the required permissions. For this sample, you must have "storage.buckets.list".
+    Args:
+        project_id: The project id of your Google Cloud project.
+    """
+
+    # This snippet demonstrates how to list buckets.
+    # *NOTE*: Replace the client created below with the client required for your application.
+    # Note that the credentials are not specified when constructing the client.
+    # Hence, the client library will look for credentials using ADC.
+    storage_client = storage.Client(project=project_id)
+    buckets = storage_client.list_buckets()
+    print("Buckets:")
+    for bucket in buckets:
+        print(bucket.name)
+    print("Listed all storage buckets.")
+
+# [END auth_cloud_implicit_adc]

auth/cloud-client-temp/custom_aws_supplier.py

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+# Copyright 2025 Google LLC
+# 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.
+
+import json
+import os
+import sys
+
+import boto3
+from dotenv import load_dotenv
+from google.auth.aws import AwsSecurityCredentials, AwsSecurityCredentialsSupplier
+from google.auth.aws import Credentials as AwsCredentials
+from google.auth.exceptions import GoogleAuthError
+from google.auth.transport.requests import AuthorizedSession
+
+load_dotenv()
+
+
+class CustomAwsSupplier(AwsSecurityCredentialsSupplier):
+    """Custom AWS Security Credentials Supplier."""
+
+    def __init__(self) -> None:
+        """Initializes the Boto3 session, prioritizing environment variables for region."""
+        # Explicitly read the region from the environment first. This ensures that
+        # a value from a .env file is picked up reliably for local testing.
+        region = os.getenv("AWS_REGION") or os.getenv("AWS_DEFAULT_REGION")
+
+        # If region is None, Boto3's discovery chain will be used when needed.
+        self.session = boto3.Session(region_name=region)
+        self._cached_region = None
+        print(f"[INFO] CustomAwsSupplier initialized. Region from env: {region}")
+
+    def get_aws_region(self, context: object, request: object) -> str:
+        """Returns the AWS region using Boto3's default provider chain."""
+        if self._cached_region:
+            return self._cached_region
+
+        # Accessing region_name will use the value from the constructor if provided,
+        # otherwise it triggers Boto3's lazy-loading discovery (e.g., metadata service).
+        self._cached_region = self.session.region_name
+
+        if not self._cached_region:
+            print("[ERROR] Boto3 was unable to resolve an AWS region.", file=sys.stderr)
+            raise GoogleAuthError("Boto3 was unable to resolve an AWS region.")
+
+        print(f"[INFO] Boto3 resolved AWS Region: {self._cached_region}")
+        return self._cached_region
+
+    def get_aws_security_credentials(self, context: object, request: object = None) -> AwsSecurityCredentials:
+        """Retrieves AWS security credentials using Boto3's default provider chain."""
+        aws_credentials = self.session.get_credentials()
+        if not aws_credentials:
+            print("[ERROR] Unable to resolve AWS credentials.", file=sys.stderr)
+            raise GoogleAuthError("Unable to resolve AWS credentials from the provider chain.")
+
+        # Instead of printing the whole key, mask everything but the last 4 characters
+        masked_access_key = f"{'*' * 16}{aws_credentials.access_key[-4:]}"
+        print(f"[INFO] Resolved AWS Access Key ID: {masked_access_key}")
+
+        return AwsSecurityCredentials(
+            access_key_id=aws_credentials.access_key,
+            secret_access_key=aws_credentials.secret_key,
+            session_token=aws_credentials.token,
+        )
+
+
+def main() -> None:
+    """Main function to demonstrate the custom AWS supplier."""
+    print("--- Starting Script ---")
+
+    gcp_audience = os.getenv("GCP_WORKLOAD_AUDIENCE")
+    sa_impersonation_url = os.getenv("GCP_SERVICE_ACCOUNT_IMPERSONATION_URL")
+    gcs_bucket_name = os.getenv("GCS_BUCKET_NAME")
+
+    print(f"GCP_WORKLOAD_AUDIENCE: {gcp_audience}")
+    print(f"GCS_BUCKET_NAME: {gcs_bucket_name}")
+
+    if not all([gcp_audience, sa_impersonation_url, gcs_bucket_name]):
+        print("[ERROR] Missing required environment variables.", file=sys.stderr)
+        raise GoogleAuthError("Missing required environment variables.")
+
+    custom_supplier = CustomAwsSupplier()
+
+    credentials = AwsCredentials(
+        audience=gcp_audience,
+        subject_token_type="urn:ietf:params:aws:token-type:aws4_request",
+        service_account_impersonation_url=sa_impersonation_url,
+        aws_security_credentials_supplier=custom_supplier,
+        scopes=['https://www.googleapis.com/auth/devstorage.read_write'],
+    )
+
+    bucket_url = f"https://storage.googleapis.com/storage/v1/b/{gcs_bucket_name}"
+    print(f"Request URL: {bucket_url}")
+
+    authed_session = AuthorizedSession(credentials)
+    try:
+        print("Attempting to make authenticated request to Google Cloud Storage...")
+        res = authed_session.get(bucket_url)
+        res.raise_for_status()
+        print("\n--- SUCCESS! ---")
+        print("Successfully authenticated and retrieved bucket data:")
+        print(json.dumps(res.json(), indent=2))
+    except Exception as e:
+        print("--- FAILED --- ", file=sys.stderr)
+        print(e, file=sys.stderr)
+        exit(1)
+
+
+if __name__ == "__main__":
+    main()