According to official documentation as of K8s 1.3, there is no native support for ldap authentication but using keystone can be a way to bridge to an LDAP or AD.

Found this link showing a sample walk through (with Samba):

http://cloudgeekz.com/1128/how-to-setup-active-directory-or-ldap-authentication-for-kubernetes.html

This implies the API server does the authn for the client... a more flexible solution using keystone tokens might soon be implemented here: https://github.com/kubernetes/kubernetes/pull/25391

Kismatic is one of the projects that provides a Lightweight Directory Access Protocol (LDAP) authentication webhook for Kubernetes. For Kismatic Enterprise Toolkit (KET) source code check out this link.