@Override
    public SaslClient createClient(Configuration conf, InetAddress serverAddr,
      String serverPrincipal, Token<? extends TokenIdentifier> token, boolean fallbackAllowed,
      Map<String, String> saslProps) throws IOException {
      return Sasl.createSaslClient(new String[] { MECHANISM }, null, null,
        SaslUtil.SASL_DEFAULT_REALM, saslProps, new InMemoryClientProviderCallbackHandler(token));
    }
Client provider that finds custom Token in the user's UGI and authenticates with the server via
DIGEST-MD5 using that password.
hbase-server/src/test/java/org/apache/hadoop/hbase/security/provider/CustomSaslAuthenticationProviderTestBase.java