From 00be464c05d736b8f69905bd0974591ffa9867e3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gr=C3=A9goire=20Charvet=20=E9=BB=91=E7=93=9C?=
 <greg@geekingfrog.com>
Date: Wed, 7 Jul 2021 08:59:16 +0100
Subject: [PATCH] Fix #3996 (#4051)

* Fix #3996

* Don't delete any message when duplicate handles
---
 moto/sqs/responses.py      | 23 +++++++++++++++++++----
 tests/test_sqs/test_sqs.py | 28 ++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/moto/sqs/responses.py b/moto/sqs/responses.py
index 591c8a2e6..8c68df147 100644
--- a/moto/sqs/responses.py
+++ b/moto/sqs/responses.py
@@ -17,6 +17,7 @@ from .exceptions import (
     InvalidAttributeName,
     MessageNotInflight,
     ReceiptHandleIsInvalid,
+    BatchEntryIdsNotDistinct,
 )
 from .models import sqs_backends
 from .utils import parse_message_attributes, extract_input_message_attributes
@@ -330,7 +331,8 @@ class SQSResponse(BaseResponse):
         """
         queue_name = self._get_queue_name()
 
-        message_ids = []
+        receipts = []
+
         for index in range(1, 11):
             # Loop through looking for messages
             receipt_key = "DeleteMessageBatchRequestEntry.{0}.ReceiptHandle".format(
@@ -341,12 +343,25 @@ class SQSResponse(BaseResponse):
                 # Found all messages
                 break
 
-            self.sqs_backend.delete_message(queue_name, receipt_handle[0])
-
             message_user_id_key = "DeleteMessageBatchRequestEntry.{0}.Id".format(index)
             message_user_id = self.querystring.get(message_user_id_key)[0]
-            message_ids.append(message_user_id)
+            receipts.append(
+                {"receipt_handle": receipt_handle[0], "msg_user_id": message_user_id}
+            )
 
+        receipt_seen = set()
+        for receipt_and_id in receipts:
+            receipt = receipt_and_id["receipt_handle"]
+            if receipt in receipt_seen:
+                raise BatchEntryIdsNotDistinct(receipt_and_id["msg_user_id"])
+            receipt_seen.add(receipt)
+
+        for receipt_and_id in receipts:
+            self.sqs_backend.delete_message(
+                queue_name, receipt_and_id["receipt_handle"]
+            )
+
+        message_ids = [r["msg_user_id"] for r in receipts]
         template = self.response_template(DELETE_MESSAGE_BATCH_RESPONSE)
         return template.render(message_ids=message_ids)
 
diff --git a/tests/test_sqs/test_sqs.py b/tests/test_sqs/test_sqs.py
index 41de7e7c3..f92bfa6bb 100644
--- a/tests/test_sqs/test_sqs.py
+++ b/tests/test_sqs/test_sqs.py
@@ -1714,6 +1714,34 @@ def test_send_message_batch():
     )
 
 
+@mock_sqs
+def test_delete_message_batch_with_duplicates():
+    client = boto3.client("sqs", region_name="us-east-1")
+    response = client.create_queue(QueueName="test-queue")
+    queue_url = response["QueueUrl"]
+    client.send_message(QueueUrl=queue_url, MessageBody="coucou")
+
+    messages = client.receive_message(
+        QueueUrl=queue_url, WaitTimeSeconds=0, VisibilityTimeout=0
+    )["Messages"]
+    assert messages, "at least one msg"
+    entries = [
+        {"Id": msg["MessageId"], "ReceiptHandle": msg["ReceiptHandle"]}
+        for msg in [messages[0], messages[0]]
+    ]
+
+    with pytest.raises(ClientError) as e:
+        client.delete_message_batch(QueueUrl=queue_url, Entries=entries)
+    ex = e.value
+    assert ex.response["Error"]["Code"] == "BatchEntryIdsNotDistinct"
+
+    # no messages are deleted
+    messages = client.receive_message(QueueUrl=queue_url, WaitTimeSeconds=0).get(
+        "Messages", []
+    )
+    assert messages, "message still in the queue"
+
+
 @mock_sqs
 def test_message_attributes_in_receive_message():
     sqs = boto3.resource("sqs", region_name="us-east-1")