Principal invokeAuthenticator(Properties securityProps, MemberIdentifier member,
      Properties credentials) throws AuthenticationFailedException {
    String authMethod = securityProps.getProperty(SECURITY_PEER_AUTHENTICATOR);
    org.apache.geode.security.Authenticator auth = null;
    try {
      auth = CallbackInstantiator.getObjectOfType(authMethod,
          org.apache.geode.security.Authenticator.class);

      // this.securityProps contains security-ldap-basedn but security-ldap-baseDomainName is
      // expected
      auth.init(this.securityProps, logWriter, securityLogWriter);
      return auth.authenticate(credentials, (InternalDistributedMember) member);

    } catch (GemFireSecurityException gse) {
      throw gse;

    } catch (Exception ex) {
      throw new AuthenticationFailedException(
          "Failed to acquire Authenticator object", ex);

    } finally {
      if (auth != null) {
        auth.close();
      }
    }
  }
Method is package protected to be used in testing.
geode-core/src/main/java/org/apache/geode/distributed/internal/membership/adapter/auth/GMSAuthenticator.java