Allow lower case checksum algorithms

This is was made to keep parity with the pure Python transfer
manager which accepts lowercase algorithm values.

Author: kyleknap

awscli/s3transfer/crt.py

@@ -236,11 +236,11 @@ def _validate_checksum_algorithm_supported(self, extra_args):
         checksum_algorithm = extra_args.get('ChecksumAlgorithm')
         if checksum_algorithm is None:
             return
-        if checksum_algorithm not in awscrt.s3.S3ChecksumAlgorithm.__members__:
+        supported_algorithms = list(awscrt.s3.S3ChecksumAlgorithm.__members__)
+        if checksum_algorithm.upper() not in supported_algorithms:
             raise ValueError(
                 f'ChecksumAlgorithm: {checksum_algorithm} not supported. '
-                f'Supported algorithms are: '
-                f'{list(awscrt.s3.S3ChecksumAlgorithm.__members__)}'
+                f'Supported algorithms are: {supported_algorithms}'
             )
 
     def _cancel_transfers(self):
@@ -637,7 +637,7 @@ def _get_make_request_args_put_object(
 
         checksum_algorithm = call_args.extra_args.pop(
             'ChecksumAlgorithm', 'CRC32'
-        )
+        ).upper()
         checksum_config = awscrt.s3.S3ChecksumConfig(
             algorithm=awscrt.s3.S3ChecksumAlgorithm[checksum_algorithm],
             location=awscrt.s3.S3ChecksumLocation.TRAILER,

tests/functional/s3transfer/test_crt.py

@@ -307,6 +307,42 @@ def test_upload_override_checksum_algorithm(self):
         )
         self._assert_subscribers_called(future)
 
+    def test_upload_override_checksum_algorithm_accepts_lowercase(self):
+        future = self.transfer_manager.upload(
+            self.filename,
+            self.bucket,
+            self.key,
+            {'ChecksumAlgorithm': 'crc32c'},
+            [self.record_subscriber],
+        )
+        future.result()
+
+        callargs_kwargs = self.s3_crt_client.make_request.call_args[1]
+        self.assertEqual(
+            callargs_kwargs,
+            {
+                'request': mock.ANY,
+                'type': awscrt.s3.S3RequestType.PUT_OBJECT,
+                'send_filepath': self.filename,
+                'on_progress': mock.ANY,
+                'on_done': mock.ANY,
+                'checksum_config': self._get_expected_upload_checksum_config(
+                    algorithm=awscrt.s3.S3ChecksumAlgorithm.CRC32C
+                ),
+            },
+        )
+        self._assert_expected_crt_http_request(
+            callargs_kwargs["request"],
+            expected_http_method='PUT',
+            expected_content_length=len(self.expected_content),
+            expected_missing_headers=[
+                'Content-MD5',
+                'x-amz-sdk-checksum-algorithm',
+                'X-Amz-Trailer',
+            ],
+        )
+        self._assert_subscribers_called(future)
+
     def test_upload_throws_error_for_unsupported_checksum(self):
         with self.assertRaisesRegex(
             ValueError, 'ChecksumAlgorithm: UNSUPPORTED not supported'