server: validate labels size to avoid dos

Signed-off-by: Antonio Murdaca <runcom@redhat.com>

server/container_create.go

@@ -720,6 +720,10 @@ func (s *Server) createSandboxContainer(ctx context.Context, containerID string,
 
 	labels := containerConfig.GetLabels()
 
+	if err := validateLabels(labels); err != nil {
+		return nil, err
+	}
+
 	metadata := containerConfig.GetMetadata()
 
 	kubeAnnotations := containerConfig.GetAnnotations()

server/sandbox_run.go

@@ -224,6 +224,10 @@ func (s *Server) RunPodSandbox(ctx context.Context, req *pb.RunPodSandboxRequest
 	// add labels
 	labels := req.GetConfig().GetLabels()
 
+	if err := validateLabels(labels); err != nil {
+		return nil, err
+	}
+
 	// Add special container name label for the infra container
 	labelsJSON := []byte{}
 	if labels != nil {

server/utils.go

@@ -18,6 +18,8 @@ const (
 	// According to http://man7.org/linux/man-pages/man5/resolv.conf.5.html:
 	// "The search list is currently limited to six domains with a total of 256 characters."
 	maxDNSSearches = 6
+
+	maxLabelSize = 4096
 )
 
 func copyFile(src, dest string) error {
@@ -196,3 +198,15 @@ func recordError(operation string, err error) {
 		metrics.CRIOOperationsErrors.WithLabelValues(operation).Inc()
 	}
 }
+
+func validateLabels(labels map[string]string) error {
+	for k, v := range labels {
+		if (len(k) + len(v)) > maxLabelSize {
+			if len(k) > 10 {
+				k = k[:10]
+			}
+			return fmt.Errorf("label key and value greater than maximum size (%d bytes), key: %s", maxLabelSize, k)
+		}
+	}
+	return nil
+}