docs: Improve AWS supplier samples

docs/user-guide.rst

@@ -552,36 +552,45 @@ whether the credential retrieval is retryable.
 Any call to the supplier from the Identity Pool credential will send a :class:`google.auth.external_account.SupplierContext`
 object, which contains the requested audience and subject type. Additionally, the credential will
 send the :class:`google.auth.transport.requests.Request` passed in the credential refresh call which
-can be used to make HTTP requests.::
+can be used to make HTTP requests. Using a custom supplier allows workload or workforce identity federation to be used
+with other AWS credential sources such as EKS or ECS in addition to the EC2 metadata endpoint which is already natively supported by ADC.::
 
+    import boto3
     from google.auth import aws
     from google.auth import exceptions
+    from google.cloud import storage
 
     class CustomAwsSecurityCredentialsSupplier(aws.AwsSecurityCredentialsSupplier):
 
+        def __init__(self, region):
+            self._region = region
+
         def get_aws_security_credentials(self, context, request):
-            audience = context.audience
+            aws_credentials = boto3.Session(region_name=self._region).get_credentials().get_frozen_credentials()
+
             try:
-                # Return valid AWS security credentials. These credentials are not cached by
-                # the google credential, so caching should be implemented in the supplier.
-                return aws.AwsSecurityCredentials(ACCESS_KEY_ID, SECRET_ACCESS_KEY, SESSION_TOKEN)
+                return aws.AwsSecurityCredentials(aws_credentials.access_key, aws_credentials.secret_key, aws_credentials.token)
             except Exception as e:
-                # If credentials retrieval fails, raise a refresh error, setting retryable to true if the client should
-                # attempt to retrieve the subject token again.
                 raise exceptions.RefreshError(e, retryable=True)
 
         def get_aws_region(self, context, request):
-            # Return active AWS region.
+            return self._region
 
-    supplier = CustomAwsSecurityCredentialsSupplier()
+    aws_region = "AWS_REGION" # Set the current AWS region (i.e. us-east-2)
+    supplier = CustomAwsSecurityCredentialsSupplier(aws_region)
 
+    # Create credentials using the custom supplier.
     credentials = aws.Credentials(
         AUDIENCE, # Set GCP Audience.
         "urn:ietf:params:aws:token-type:aws4_request", # Set AWS subject token type.
         aws_security_credentials_supplier=supplier, # Set supplier.
-        scopes=SCOPES # Set desired scopes.
+        scopes=['https://www.googleapis.com/auth/cloud-platform'] # Set scopes.
     )
 
+    # Create service client and use the credentials you just created.
+    # The GCP project id must also be set.
+    storage_client = storage.Client(credentials=credentials, project=GCP_PROJECT_ID)
+
 Where the `audience`_ is: ``///iam.googleapis.com/projects/PROJECT_NUMBER/locations/global/workloadIdentityPools/POOL_ID/providers/PROVIDER_ID``
 Where the following variables need to be substituted:
 

samples/cloud-client/snippets/authenticate_with_aws_supplier.py

@@ -0,0 +1,65 @@
+# Copyright 2024 Google Inc.
+#
+# 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_aws_supplier]
+
+from google.cloud import storage
+
+from google.auth import aws
+from google.auth import exceptions
+import boto3
+
+
+class CustomAwsSecurityCredentialsSupplier(aws.AwsSecurityCredentialsSupplier):
+
+    def __init__(self, region):
+        self._region = region
+
+    def get_aws_security_credentials(self, context, request):
+        aws_credentials = boto3.Session(region_name=self._region).get_credentials().get_frozen_credentials()
+
+        try:
+            return aws.AwsSecurityCredentials(aws_credentials.access_key, aws_credentials.secret_key, aws_credentials.token)
+        except Exception as e:
+            raise exceptions.RefreshError(e, retryable=True)
+
+    def get_aws_region(self, context, request):
+        return self._region
+
+
+def authenticate_with_aws_supplier(project_id="your-google-cloud-project-id", aws_region="your_aws_region", audience="your_federation_audience"):
+    """
+    List storage buckets by authenticating with a custom AWS supplier.
+
+    // TODO(Developer) Before running this sample,:
+    //  1. Replace the project, region, and audience variables.
+    //  2. Make sure you have the necessary permission to list storage buckets: "storage.buckets.list"
+    """
+
+    credentials = aws.Credentials(
+        audience,
+        "urn:ietf:params:aws:token-type:aws4_request",
+        aws_security_credentials_supplier=CustomAwsSecurityCredentialsSupplier(aws_region),
+        scopes=['https://www.googleapis.com/auth/cloud-platform']
+    )
+
+    # 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_aws_supplier]