S3: Checksum headers added to response (#5392)

moto/s3/responses.py

@@ -1356,6 +1356,16 @@ class S3Response(BaseResponse):
             "x-amz-server-side-encryption-aws-kms-key-id", None
         )
 
+        checksum_algorithm = request.headers.get("x-amz-sdk-checksum-algorithm", "")
+        checksum_header = f"x-amz-checksum-{checksum_algorithm.lower()}"
+        checksum_value = request.headers.get(checksum_header)
+        if not checksum_value and checksum_algorithm:
+            search = re.search(r"x-amz-checksum-\w+:(\w+={1,2})", body.decode())
+            checksum_value = search.group(1) if search else None
+
+        if checksum_value:
+            response_headers.update({checksum_header: checksum_value})
+
         bucket_key_enabled = request.headers.get(
             "x-amz-server-side-encryption-bucket-key-enabled", None
         )

tests/test_s3/test_s3.py

@@ -3395,3 +3395,21 @@ def test_prefix_encoding():
         map(lambda common_prefix: common_prefix["Prefix"], data["CommonPrefixes"])
     )
     assert ["foo%2Fbar/", "foo/"] == folders
+
+
+@mock_s3
+@pytest.mark.parametrize("algorithm", ["CRC32", "CRC32C", "SHA1", "SHA256"])
+def test_checksum_response(algorithm):
+    bucket_name = "checksum-bucket"
+    client = boto3.client("s3", region_name=DEFAULT_REGION_NAME)
+    client.create_bucket(Bucket=bucket_name)
+    if (
+        algorithm != "CRC32C"
+    ):  # awscrt is required to allow botocore checksum with CRC32C
+        response = client.put_object(
+            Bucket=bucket_name,
+            Key="test-key",
+            Body=b"data",
+            ChecksumAlgorithm=algorithm,
+        )
+        assert f"Checksum{algorithm}" in response