Revert "Validate multipart downloads using object ETags"

Author: hssyoo

.changes/next-release/bugfix-download-32668.json

@@ -14,10 +14,8 @@
 import logging
 import threading
 
-from botocore.exceptions import ClientError
-
 from s3transfer.compat import seekable
-from s3transfer.exceptions import RetriesExceededError, S3DownloadFailedError
+from s3transfer.exceptions import RetriesExceededError
 from s3transfer.futures import IN_MEMORY_DOWNLOAD_TAG
 from s3transfer.tasks import SubmissionTask, Task
 from s3transfer.utils import (
@@ -348,18 +346,14 @@ def _submit(
         :param bandwidth_limiter: The bandwidth limiter to use when
             downloading streams
         """
-        response = client.head_object(
-            Bucket=transfer_future.meta.call_args.bucket,
-            Key=transfer_future.meta.call_args.key,
-            **transfer_future.meta.call_args.extra_args,
-        )
-        # Provide an etag to ensure a stored object is not modified
-        # during a multipart download.
-        transfer_future.meta.provide_object_etag(response.get('ETag'))
-
         if transfer_future.meta.size is None:
             # If a size was not provided figure out the size for the
             # user.
+            response = client.head_object(
+                Bucket=transfer_future.meta.call_args.bucket,
+                Key=transfer_future.meta.call_args.key,
+                **transfer_future.meta.call_args.extra_args,
+            )
             transfer_future.meta.provide_transfer_size(
                 response['ContentLength']
             )
@@ -485,12 +479,9 @@ def _submit_ranged_download_request(
                 part_size, i, num_parts
             )
 
-            # Inject extra parameters to be passed in as extra args
-            extra_args = {
-                'Range': range_parameter,
-            }
-            if transfer_future.meta.etag is not None:
-                extra_args['IfMatch'] = transfer_future.meta.etag
+            # Inject the Range parameter to the parameters to be passed in
+            # as extra args
+            extra_args = {'Range': range_parameter}
             extra_args.update(call_args.extra_args)
             finalize_download_invoker.increment()
             # Submit the ranged downloads
@@ -602,15 +593,6 @@ def _main(
                     else:
                         return
                 return
-            except ClientError as e:
-                error_code = e.response.get('Error', {}).get('Code')
-                if error_code == "PreconditionFailed":
-                    raise S3DownloadFailedError(
-                        f'Contents of stored object "{key}" in bucket '
-                        f'"{bucket}" did not match expected ETag.'
-                    )
-                else:
-                    raise
             except S3_RETRYABLE_DOWNLOAD_ERRORS as e:
                 logger.debug(
                     "Retrying exception caught (%s), "

s3transfer/download.py

@@ -23,10 +23,6 @@ class S3UploadFailedError(Exception):
     pass
 
 
-class S3DownloadFailedError(Exception):
-    pass
-
-
 class InvalidSubscriberMethodError(Exception):
     pass
 

s3transfer/exceptions.py

@@ -134,7 +134,6 @@ def __init__(self, call_args=None, transfer_id=None):
         self._transfer_id = transfer_id
         self._size = None
         self._user_context = {}
-        self._etag = None
 
     @property
     def call_args(self):
@@ -156,11 +155,6 @@ def user_context(self):
         """A dictionary that requesters can store data in"""
         return self._user_context
 
-    @property
-    def etag(self):
-        """The etag of the stored object for validating multipart downloads"""
-        return self._etag
-
     def provide_transfer_size(self, size):
         """A method to provide the size of a transfer request
 
@@ -170,15 +164,6 @@ def provide_transfer_size(self, size):
         """
         self._size = size
 
-    def provide_object_etag(self, etag):
-        """A method to provide the etag of a transfer request
-
-        By providing this value, the TransferManager will validate
-        multipart downloads by supplying an IfMatch parameter with
-        the etag as the value to GetObject requests.
-        """
-        self._etag = etag
-
 
 class TransferCoordinator:
     """A helper class for managing TransferFuture"""

s3transfer/futures.py

@@ -21,7 +21,7 @@
 from botocore.exceptions import ClientError
 
 from s3transfer.compat import SOCKET_ERROR
-from s3transfer.exceptions import RetriesExceededError, S3DownloadFailedError
+from s3transfer.exceptions import RetriesExceededError
 from s3transfer.manager import TransferConfig, TransferManager
 from tests import (
     BaseGeneralInterfaceTest,
@@ -48,7 +48,6 @@ def setUp(self):
         # Initialize some default arguments
         self.bucket = 'mybucket'
         self.key = 'mykey'
-        self.etag = 'myetag'
         self.extra_args = {}
         self.subscribers = []
 
@@ -85,10 +84,7 @@ def create_stubbed_responses(self):
         return [
             {
                 'method': 'head_object',
-                'service_response': {
-                    'ContentLength': len(self.content),
-                    'ETag': self.etag,
-                },
+                'service_response': {'ContentLength': len(self.content)},
             },
             {
                 'method': 'get_object',
@@ -295,7 +291,6 @@ def test_retry_rewinds_callbacks(self):
         self.assertEqual(-3, progress_byte_amts[1])
 
     def test_can_provide_file_size(self):
-        self.add_head_object_response()
         self.add_successful_get_object_responses()
 
         call_kwargs = self.create_call_kwargs()
@@ -304,6 +299,8 @@ def test_can_provide_file_size(self):
         future = self.manager.download(**call_kwargs)
         future.result()
 
+        # The HeadObject should have not happened and should have been able
+        # to successfully download the file.
         self.stubber.assert_no_pending_responses()
         with open(self.filename, 'rb') as f:
             self.assertEqual(self.content, f.read())
@@ -472,10 +469,7 @@ def create_stubbed_responses(self):
         return [
             {
                 'method': 'head_object',
-                'service_response': {
-                    'ContentLength': len(self.content),
-                    'ETag': self.etag,
-                },
+                'service_response': {'ContentLength': len(self.content)},
             },
             {
                 'method': 'get_object',
@@ -508,7 +502,7 @@ def test_download(self):
         expected_ranges = ['bytes=0-3', 'bytes=4-7', 'bytes=8-']
         self.add_head_object_response(expected_params)
         self.add_successful_get_object_responses(
-            {**expected_params, 'IfMatch': self.etag}, expected_ranges
+            expected_params, expected_ranges
         )
 
         future = self.manager.download(
@@ -529,76 +523,6 @@ def test_download_with_checksum_enabled(self):
         }
         expected_ranges = ['bytes=0-3', 'bytes=4-7', 'bytes=8-']
         self.add_head_object_response(expected_params)
-        self.add_successful_get_object_responses(
-            {**expected_params, 'IfMatch': self.etag}, expected_ranges
-        )
-
-        future = self.manager.download(
-            self.bucket, self.key, self.filename, self.extra_args
-        )
-        future.result()
-
-        # Ensure that the contents are correct
-        with open(self.filename, 'rb') as f:
-            self.assertEqual(self.content, f.read())
-
-    def test_download_raises_if_etag_validation_fails(self):
-        expected_params = {
-            'Bucket': self.bucket,
-            'Key': self.key,
-        }
-        expected_ranges = ['bytes=0-3', 'bytes=4-7']
-        self.add_head_object_response(expected_params)
-
-        # Add successful GetObject responses for the first 2 requests.
-        for i, stubbed_response in enumerate(
-            self.create_stubbed_responses()[1:3]
-        ):
-            stubbed_response['expected_params'] = copy.deepcopy(
-                {**expected_params, 'IfMatch': self.etag}
-            )
-            stubbed_response['expected_params']['Range'] = expected_ranges[i]
-            self.stubber.add_response(**stubbed_response)
-
-        # Simulate ETag validation failure by adding a
-        # client error for the last GetObject request.
-        self.stubber.add_client_error(
-            method='get_object',
-            service_error_code='PreconditionFailed',
-            service_message=(
-                'At least one of the pre-conditions you specified did not hold'
-            ),
-            http_status_code=412,
-        )
-
-        future = self.manager.download(
-            self.bucket, self.key, self.filename, self.extra_args
-        )
-        with self.assertRaises(S3DownloadFailedError) as e:
-            future.result()
-        self.assertIn('did not match expected ETag', str(e.exception))
-
-        # Ensure no data is written to disk.
-        self.assertFalse(os.path.exists(self.filename))
-
-    def test_download_without_etag(self):
-        expected_params = {
-            'Bucket': self.bucket,
-            'Key': self.key,
-        }
-        expected_ranges = ['bytes=0-3', 'bytes=4-7', 'bytes=8-']
-
-        # Stub HeadObject response with no ETag
-        head_object_response = {
-            'method': 'head_object',
-            'service_response': {
-                'ContentLength': len(self.content),
-            },
-            'expected_params': expected_params,
-        }
-        self.stubber.add_response(**head_object_response)
-
-        # This asserts that IfMatch isn't in the GetObject requests.
         self.add_successful_get_object_responses(
             expected_params, expected_ranges
         )

tests/functional/test_download.py

@@ -395,8 +395,7 @@ def setUp(self):
 
         self.bucket = 'mybucket'
         self.key = 'mykey'
-        self.etag = 'myetag'
-        self.extra_args = {'IfMatch': self.etag}
+        self.extra_args = {}
         self.subscribers = []
 
         # Create a stream to read from
@@ -453,11 +452,7 @@ def assert_tag_for_get_object(self, tag_value):
 
     def add_head_object_response(self):
         self.stubber.add_response(
-            'head_object',
-            {
-                'ContentLength': len(self.content),
-                'ETag': self.etag,
-            },
+            'head_object', {'ContentLength': len(self.content)}
         )
 
     def add_get_responses(self):