Use static whitelist

botocore/client.py

@@ -30,6 +30,7 @@
 from botocore.utils import S3RegionRedirector
 from botocore.utils import fix_s3_host
 from botocore.utils import switch_to_virtual_host_style
+from botocore.utils import S3_ACCELERATE_WHITELIST
 from botocore.args import ClientArgsCreator
 from botocore.compat import urlsplit
 # Keep this imported.  There's pre-existing code that uses
@@ -180,7 +181,7 @@ def _get_s3_addressing_handler(self, endpoint_url, s3_config,
         return fix_s3_host
 
     def _is_s3_accelerate(self, endpoint_url, s3_config):
-        # Accelerate has been explicitly configured
+        # Accelerate has been explicitly configured.
         if s3_config is not None and s3_config.get('use_accelerate_endpoint'):
             return True
 
@@ -194,24 +195,21 @@ def _is_s3_accelerate(self, endpoint_url, s3_config):
         if not netloc.endswith('amazonaws.com'):
             return False
 
-        # The first part of the url should always be s3-accelerate
+        # The first part of the url should always be s3-accelerate.
         parts = netloc.split('.')
         if parts[0] != 's3-accelerate':
             return False
 
-        # There should not be more than two components between 's3-accelerate'
-        # and 'amazonaws.com'
+        # Url parts between 's3-accelerate' and 'amazonaws.com' which
+        # represent different url features.
         feature_parts = parts[1:-2]
-        if len(feature_parts) > 2:
-            return False
 
-        # There should be no duplicates
+        # There should be no duplicate url parts.
         if len(feature_parts) != len(set(feature_parts)):
             return False
 
-        # Remaining parts must be in the whitelist.
-        whitelist = ['dualstack']
-        return all(p in whitelist for p in feature_parts)
+        # Remaining parts must all be in the whitelist.
+        return all(p in S3_ACCELERATE_WHITELIST for p in feature_parts)
 
     def _get_client_args(self, service_model, region_name, is_secure,
                          endpoint_url, verify, credentials,

botocore/utils.py

@@ -46,6 +46,7 @@
     'fips-us-gov-west-1',
 ]
 RETRYABLE_HTTP_ERRORS = (requests.Timeout, requests.ConnectionError)
+S3_ACCELERATE_WHITELIST = ['dualstack']
 
 
 class _RetriesExceededError(Exception):
@@ -774,10 +775,12 @@ def switch_host_s3_accelerate(request, operation_name, **kwargs):
     # before it gets changed to virtual. So we are not concerned with ensuring
     # that the bucket name is translated to the virtual style here and we
     # can hard code the Accelerate endpoint.
-    whitelist = ['dualstack', 'amazonaws', 'com']
     parts = urlsplit(request.url).netloc.split('.')
-    parts = [p for p in parts if p in whitelist]
-    endpoint = 'https://s3-accelerate.' + '.'.join(parts)
+    parts = [p for p in parts if p in S3_ACCELERATE_WHITELIST]
+    endpoint = 'https://s3-accelerate.'
+    if len(parts) > 0:
+        endpoint += '.'.join(parts) + '.'
+    endpoint += 'amazonaws.com'
 
     if operation_name in ['ListBuckets', 'CreateBucket', 'DeleteBucket']:
         return