如何讓Web API 避免DDOS 攻擊

資訊安全一直都是資訊人重視的一環，網路最常受到一種攻擊DDOS，
一直不斷連線，讓IIS 一直保持連線暴量，其他人就無法正常連線，
針對這種攻繫，已經有人設定好套件囉~  

安裝相關套件

設定web API的連線數設定

到App_Start的webApiConfig 設定連線數

WebApiConfig.cs

public static class WebApiConfig    {        public static void Register(HttpConfiguration config)        {            config.Routes.MapHttpRoute(                name: "DefaultApi",                routeTemplate: "api/{controller}/{action}/{id}",                defaults: new { id = RouteParameter.Optional }            );         //設定連線數:每分鐘最多只連5次，每小時最多20次，一天限300次(可自行修改)            ThrottlePolicy policy = new ThrottlePolicy(perMinute: 5, perHour: 20, perDay: 300)            {                IpThrottling = true,            };            config.MessageHandlers.Add(new ThrottlingHandler(                 policy,                 policyRepository: new PolicyCacheRepository(),                 repository: new CacheRepository(),                 logger: null             ));        }    }

Controller\SendMailcontroller.cs (建立新的web api)

public class SendMailcontroller : ApiController    {        // GET api/<controller>        public IEnumerable<string> Get()        {            return new string[] { "value1", "value2" };        } }

開啟post man 測試超過連線數

每分鐘超過5次

這樣是不是很方便~  不再擔心被ddos攻擊我們的Web API

如何用c# 幫你自動爬文

最近案子的需求需要有爬文的功能，所以就順便留了記錄，也可以提供案例分享給大家，首先介紹一樣好物 HtmlAgilityPack ，它是用xpath 讀取網路dom的元件，換句話說，只要設定好xpath，就能easy 取得網頁的任何資訊，以下就是簡易示範的步驟。下戴相關套件和取得xpath tool

是免費軟體，值得推一下… 很方便的工具

Xpath Help 是安裝Google Chrome 的擴充套件，方便自動取得xpath 路徑

點選右上角xpath help後， 出現下面的黑框，在左邊的

設定xml檔

<?xml version="1.0" encoding="utf-8" ?> <etmall>   <ProductName>//*[@id="productDetail"]/div[2]/section/section/div[1]/h3</ProductName> <ProductImg>//*[@id="prodSlider"]/div[2]/a/img</ProductImg> </etmall>

示範:抓取這兩個xpath 路徑，做成xml檔，方便日後更新xpath

程式架構說明

Public class HtmlAgilityPackService    {        private XmlDocument _xmldoc = new XmlDocument();        private string _path = Directory.GetCurrentDirectory();        private HtmlAgilityPack.HtmlDocument _doc = new HtmlAgilityPack.HtmlDocument();        private WebBrowser _web = new WebBrowser();                public  HtmlAgilityPackService(string URL)        {             //讀取XML檔，指定目錄位置            _xmldoc.Load(_path + "\\PathStructure.xml");            _web.ScriptErrorsSuppressed = true;            _web.Navigate(URL);            waitTillLoad(_web);//取得HTML值            _doc.Load(new StringReader(_web.Document.Body.OuterHtml));        }       //讀取html ，值到讀取狀態complete        private void waitTillLoad(WebBrowser webBrControl)        {            WebBrowserReadyState loadStatus;            int waittime = 10;            int counter = 0;            while (true)            {                loadStatus = webBrControl.ReadyState;                Application.DoEvents();                if ((counter > waittime) || (loadStatus == WebBrowserReadyState.Uninitialized) || (loadStatus == WebBrowserReadyState.Loading) || (loadStatus == WebBrowserReadyState.Interactive))                {                    break;                }                counter++;            }            counter = 0;            while (true)            {                loadStatus = webBrControl.ReadyState;                Application.DoEvents();                if ((loadStatus == WebBrowserReadyState.Complete|| loadStatus==WebBrowserReadyState.Interactive) && webBrControl.IsBusy != true)                {                    break;                }                counter++;            }        }         //取得產品名稱        public string GetName()        {            try            {                XmlNode productName = _xmldoc.DocumentElement.SelectSingleNode("/etmall/ProductName");                HtmlNodeCollection name = _doc.DocumentNode.SelectNodes(productName.InnerText);                if (name.Count > 0)                    return name[0].InnerText;                else                    return "error";            }            catch (Exception)            {                return "error";            }        } //取得產品圖片        public string GetImage()        {            try            {                XmlNode xmlImage = _xmldoc.DocumentElement.SelectSingleNode("/etmall/ProductImg"); //取得XML檔案的XPATH設定值                HtmlNodeCollection image = _d doc.DocumentNode.SelectNodes(xmlImage.InnerText);                if (image.Count > 0)                {                    HtmlAttribute imageAttribute = image[0].Attributes["src"];                    return imageAttribute.Value; //傳回IMAGE的來源位址                }                else {                    return "error";                }            }            catch (Exception)            {                return "error";            }    } }

爬文的範例:

HtmlAgilityPackService htmlAiliPackService = new HtmlAgilityPackService(textBox1.Text); string productName = htmlAiliPackService.GetName(); string productImage = htmlAiliPackService.GetImage();

以上說明完畢~ 透過XPATH 取得DOM節點，變得更方便囉!