if !globalIAMSys.Initialized() {
		writeSTSErrorResponse(ctx, w, ErrSTSIAMNotInitialized, errIAMNotInitialized)
		return
	}

	authn := newGlobalAuthNPluginFn()
	if authn == nil {
		writeSTSErrorResponse(ctx, w, ErrSTSNotInitialized, errors.New("STS API 'AssumeRoleWithCustomToken' is disabled"))
		return
	}

	action := r.Form.Get(stsAction)