code: func (h *AuthHandlers) IsHostAuthority(cert ssh.PublicKey, address string) bool {
  	if _, err := h.authorityForCert(services.HostCA, cert); err != nil {
  		h.Entry.Debugf("Unable to find SSH host CA: %v.", err)
  		return false
  	}
  	return true
  }
docs: // IsHostAuthority is called when checking the host certificate a server
  // presents. It make sure that the key used to sign the host certificate was a
  // Teleport CA.