Asp.net core .NETCore如何验证facebook提供的访问令牌？

我有以下代码

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{

    app.UseStaticFiles();

    app.UseIdentity();

    app.UseFacebookAuthentication(new FacebookOptions
    {
        AppId = Configuration["facebook:appid"],
        AppSecret = Configuration["facebook:appsecret"],
    });

    app.UseMvc(routes =>
    {
        routes.MapRoute(
            name: "default",
            template: "{controller=Home}/{action=Index}/{id?}");
    });
}

每次向服务器发送请求时，假定此访问令牌已重新验证。.NETCore是否调用facebook进行验证，或者签名中是否使用了appsecret和appid来验证令牌