备忘asp.net core使用中间件实现IP白名单访问

1、**添加中间件MiddleWare**

 public class MyMiddleware
    {
        private readonly RequestDelegate _next;
        private readonly ILogger<MyMiddleware> _logger;
        private readonly string _safelist;
        public MyMiddleware(RequestDelegate next, ILogger<MyMiddleware> logger, string safelist)
        {
            _safelist = safelist;
            _next = next;
            _logger = logger;
        }
        public async Task Invoke(HttpContext context)
        {
            var remoteIp = context.Connection.RemoteIpAddress;
            FileStream fs = new FileStream("ip.txt", FileMode.OpenOrCreate);
            //获得字节数组
            byte[] data = System.Text.Encoding.Default.GetBytes(DateTime.Now + "ip" + ":" + remoteIp);
            //开始写入
            fs.Write(data, 0, data.Length);
            //清空缓冲区、关闭流
            fs.Flush();
            fs.Close();
            _logger.LogDebug("Request from Remote IP address: {RemoteIp}", remoteIp);
            string[] ip = _safelist.Split(';');
            var bytes = remoteIp.GetAddressBytes(); var badIp = true;
            for (int i = 0; i < ip.Length; i++)

            {
                var testIp = IPAddress.Parse(ip[i]);
                if (testIp.GetAddressBytes().SequenceEqual(bytes))
                { badIp = false; break; }
            }
            if (badIp)
            {
                _logger.LogWarning($"Forbidden Request from Remote IP address: {remoteIp}");
                context.Response.StatusCode = StatusCodes.Status403Forbidden;
                await context.Response.WriteAsync($"Forbidden Request from Remote IP address: {remoteIp}");

                return;
            }
            await _next.Invoke(context);
        }
    }

2.**在statr up中使用中间件(可以将IP地址放在appsetting.json中多个ip使用";"分隔)** 

 app.UseMiddleware(Configuration["WhiteIPList"]);