fix: overrides empty checksum type and algorithm with 'null' for ListParts

Fixes #1288

If the checksum algorithm/type is not specified during multipart upload initialization, it is considered `null`, and the `ListParts` result should also set it to `null`.

backend/posix/posix.go

@@ -2200,6 +2200,12 @@ func (p *Posix) ListParts(ctx context.Context, input *s3.ListPartsInput) (s3resp
 	if err != nil && !errors.Is(err, meta.ErrNoSuchKey) {
 		return lpr, fmt.Errorf("get mp checksum: %w", err)
 	}
+	if checksum.Algorithm == "" {
+		checksum.Algorithm = types.ChecksumAlgorithm("null")
+	}
+	if checksum.Type == "" {
+		checksum.Type = types.ChecksumType("null")
+	}
 
 	parts := make([]s3response.Part, 0, len(ents))
 	for i, e := range ents {

tests/integration/group-tests.go

@@ -386,6 +386,7 @@ func TestListParts(s *S3Conf) {
 	//TODO: remove the condition after implementing checksums in azure
 	if !s.azureTests {
 		ListParts_with_checksums(s)
+		ListParts_null_checksums(s)
 	}
 	ListParts_success(s)
 }
@@ -1111,6 +1112,7 @@ func GetIntTests() IntTests {
 		"ListParts_default_max_parts":                                             ListParts_default_max_parts,
 		"ListParts_truncated":                                                     ListParts_truncated,
 		"ListParts_with_checksums":                                                ListParts_with_checksums,
+		"ListParts_null_checksums":                                                ListParts_null_checksums,
 		"ListParts_success":                                                       ListParts_success,
 		"ListMultipartUploads_non_existing_bucket":                                ListMultipartUploads_non_existing_bucket,
 		"ListMultipartUploads_empty_result":                                       ListMultipartUploads_empty_result,

tests/integration/tests.go

@@ -9650,6 +9650,42 @@ func ListParts_with_checksums(s *S3Conf) error {
 	})
 }
 
+func ListParts_null_checksums(s *S3Conf) error {
+	testName := "ListParts_null_checksums"
+	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {
+		obj := "my-obj"
+		mp, err := createMp(s3client, bucket, obj)
+		if err != nil {
+			return err
+		}
+
+		_, _, err = uploadParts(s3client, 20*1024*1024, 3, bucket, obj, *mp.UploadId)
+		if err != nil {
+			return err
+		}
+
+		ctx, cancel := context.WithTimeout(context.Background(), shortTimeout)
+		res, err := s3client.ListParts(ctx, &s3.ListPartsInput{
+			Bucket:   &bucket,
+			Key:      &obj,
+			UploadId: mp.UploadId,
+		})
+		cancel()
+		if err != nil {
+			return err
+		}
+
+		if res.ChecksumType != types.ChecksumType("null") {
+			return fmt.Errorf("expected the checksum type to be null, instead got %v", res.ChecksumType)
+		}
+		if res.ChecksumAlgorithm != types.ChecksumAlgorithm("null") {
+			return fmt.Errorf("expected the checksum algorithm to be null, instead got %v", res.ChecksumAlgorithm)
+		}
+
+		return nil
+	})
+}
+
 func ListParts_success(s *S3Conf) error {
 	testName := "ListParts_success"
 	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {