From b2adbf1f48a23612eed85359765693ba8e228cc6 Mon Sep 17 00:00:00 2001
From: Aden Khan <aakhan@sep.com>
Date: Wed, 3 Jul 2019 11:35:56 -0400
Subject: [PATCH] Adding the functionality and test so that the
 If-Modified-Since header is honored in GET Object

Signed-off-by: Aden Khan <aakhan@sep.com>
---
 moto/s3/responses.py     |  7 ++++++-
 tests/test_s3/test_s3.py | 22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/moto/s3/responses.py b/moto/s3/responses.py
index e03666666..40449dbf9 100644
--- a/moto/s3/responses.py
+++ b/moto/s3/responses.py
@@ -657,7 +657,7 @@ class ResponseObject(_TemplateEnvironmentMixin):
             body = b''
 
         if method == 'GET':
-            return self._key_response_get(bucket_name, query, key_name, headers)
+            return self._key_response_get(bucket_name, query, key_name, headers=request.headers)
         elif method == 'PUT':
             return self._key_response_put(request, body, bucket_name, query, key_name, headers)
         elif method == 'HEAD':
@@ -684,10 +684,15 @@ class ResponseObject(_TemplateEnvironmentMixin):
                 parts=parts
             )
         version_id = query.get('versionId', [None])[0]
+        if_modified_since = headers.get('If-Modified-Since', None)
         key = self.backend.get_key(
             bucket_name, key_name, version_id=version_id)
         if key is None:
             raise MissingKey(key_name)
+        if if_modified_since:
+            if_modified_since = str_to_rfc_1123_datetime(if_modified_since)
+        if if_modified_since and key.last_modified < if_modified_since:
+            return 304, response_headers, 'Not Modified'
         if 'acl' in query:
             template = self.response_template(S3_OBJECT_ACL_RESPONSE)
             return 200, response_headers, template.render(obj=key)
diff --git a/tests/test_s3/test_s3.py b/tests/test_s3/test_s3.py
index f26964ab7..697c47865 100644
--- a/tests/test_s3/test_s3.py
+++ b/tests/test_s3/test_s3.py
@@ -1596,6 +1596,28 @@ def test_boto3_delete_versioned_bucket():
 
     client.delete_bucket(Bucket='blah')
 
+@mock_s3
+def test_boto3_get_object_if_modified_since():
+    s3 = boto3.client('s3', region_name='us-east-1')
+    bucket_name = "blah"
+    s3.create_bucket(Bucket=bucket_name)
+
+    key = 'hello.txt'
+
+    s3.put_object(
+        Bucket=bucket_name,
+        Key=key,
+        Body='test'
+    )
+
+    with assert_raises(botocore.exceptions.ClientError) as err:
+        s3.get_object(
+            Bucket=bucket_name,
+            Key=key,
+            IfModifiedSince=datetime.datetime.utcnow() + datetime.timedelta(hours=1)
+        )
+    e = err.exception
+    e.response['Error'].should.equal({'Code': '304', 'Message': 'Not Modified'})
 
 @mock_s3
 def test_boto3_head_object_if_modified_since():