/* 
* * 防盜鏈IHttpHandler * * * 增加了對文件關鍵字的選擇(即僅對文件名存在某些關鍵字或不存在某些關鍵字進行過濾) * 設置web.config中<appSettings>節以下值 * string eWebapp_NoLink 如果文件名符合該正確表態式將進行過濾(不設置對所有進行過濾) * string eWebapp_AllowLink 如果文件名符合該正確表態式將不進行過濾(優先權高於AllowLink,不設置則服從AllowLink) * bool eWebapp_ AllowOnlyFile 如果爲False,(默認true)則不允許用戶直接對該文件進行訪問建議爲true * * * :)以下設置均可省略,設置只是爲了增加靈活性與體驗 * eWebapp_NoLink_Message 錯誤信息提示:默認爲Link From:域名 * eWebapp_Error_Width 錯誤信息提示圖片寬 * eWebapp_Error_Height 錯誤信息提示圖片高 * * * * 垃圾豬 2005-9-11 創建 * http://ewebapp.net 
*/
using System;using System.Web;using System.Drawing;using System.Drawing.Imaging;using System.IO;using System.Configuration;using System.Text.RegularExpressions;namespace eWebapp{
/// <summary> 
/// 防盜鏈IHttpHandler /// 參考http://www.softat.org/archiver/tid-52114.html /// 垃圾豬 2005-9-12 修正 
/// </summary> public class NoLink : IHttpHandler { private string eWebapp_NoLink = string.Empty; private string eWebapp_AllowLink = string.Empty; private bool eWebapp_AllowOnlyFile = true; private string eWebapp_NoLink_Message = string.Empty; private bool error = false; public NoLink() { // // TODO: 在此處添加構造函數邏輯 // } public void ProcessRequest(HttpContext context) { eWebapp_NoLink_Message = ConfigurationSettings.AppSettings["eWebapp_NoLink_Message"]; string myDomain = string.Empty; error = errorLink(context, out myDomain); if (Empty(eWebapp_NoLink_Message)) { eWebapp_NoLink_Message = "Link from :" + myDomain; } if (error) { //Jpg(context.Response,eWebapp_NoLink_Message); Jpg(context.Response, eWebapp_NoLink_Message); } else { Real(context.Response, context.Request); } } public bool IsReusable { get { return true; } } /// <summary> /// 輸出錯誤信息 /// </summary> /// <param name="Response"></param> /// <param name="_word"></param> private void Jpg(HttpResponse Response, string _word) { int myErrorWidth = _word.Length * 15; int myErrorHeight = 16; try { int _myErrorWidth = Convert.ToInt32(ConfigurationSettings.AppSettings["eWebapp_Error_Width"]); if (_myErrorWidth > 0) { myErrorWidth = _myErrorWidth; } } catch { } try { int _myErrorHeight = Convert.ToInt32(ConfigurationSettings.AppSettings["eWebapp_Error_Height"]); if (_myErrorHeight > 0) { myErrorHeight = _myErrorHeight; } } catch { } Bitmap Img = null; Graphics g = null; MemoryStream ms = null; Img = new Bitmap(myErrorWidth, myErrorHeight); g = Graphics.FromImage(Img); g.Clear(Color.White); Font f = new Font("Arial", 9); SolidBrush s = new SolidBrush(Color.Red); g.DrawString(_word, f, s, 3, 3); ms = new MemoryStream(); Img.Save(ms, ImageFormat.Jpeg); Response.ClearContent(); Response.ContentType = "image/Gif"; Response.BinaryWrite(ms.ToArray()); g.Dispose(); Img.Dispose(); Response.End(); } /// <summary> /// 輸出真實文件 /// </summary> /// <param name="response"></param> /// <param name="context"></param> private void Real(HttpResponse response, HttpRequest request) { FileInfo file = new System.IO.FileInfo(request.PhysicalPath); response.Clear(); response.AddHeader("Content-Disposition", "filename=" + file.Name); response.AddHeader("Content-Length", file.Length.ToString()); string fileExtension = file.Extension.ToLower(); //這裏選擇輸出的文件格式 //可以參考http://ewebapp.cnblogs.com/articles/234756.html增加對更多文件格式的支持. switch (fileExtension) { case "mp3": response.ContentType = "audio/mpeg3"; break; case "mpeg": response.ContentType = "video/mpeg"; break; case "jpg": response.ContentType = "image/jpeg"; break; case "bmp": response.ContentType = "image/bmp"; break; case "gif": response.ContentType = "image/gif"; break; case "doc": response.ContentType = "application/msword"; break; case "css": response.ContentType = "text/css"; break; default: response.ContentType = "application/octet-stream"; break; } response.WriteFile(file.FullName); response.End(); } /// <summary> /// 確認字符串是否爲空 /// </summary> /// <param name="_value"></param> /// <returns></returns> private bool Empty(string _value) { if (_value == null | _value == string.Empty | _value == "") { return true; } else { return false; } } /// <summary> /// 檢查是否是非法鏈接 /// </summary> /// <param name="context"></param> /// <param name="_myDomain"></param> /// <returns></returns> private bool errorLink(HttpContext context, out string _myDomain) { HttpResponse response = context.Response; string myDomain = context.Request.ServerVariables["SERVER_NAME"]; _myDomain = myDomain; string myDomainIp = context.Request.UserHostAddress; eWebapp_NoLink = ConfigurationSettings.AppSettings["eWebapp_NoLink"]; eWebapp_AllowLink = ConfigurationSettings.AppSettings["eWebapp_AllowLink"]; try { eWebapp_AllowOnlyFile = Convert.ToBoolean(ConfigurationSettings.AppSettings["eWebapp_AllowOnlyFile"]); } catch { eWebapp_AllowOnlyFile = true; } if (context.Request.UrlReferrer != null) { //判定referDomain是否存在網站的IP或域名 string referDomain = context.Request.UrlReferrer.AbsoluteUri.Replace(context.Request.UrlReferrer.AbsolutePath, ""); string myPath = context.Request.RawUrl; if (referDomain.IndexOf(myDomainIp) >= 0 | referDomain.IndexOf(myDomain) >= 0) { return false; } else { //這裏使用正則表達對規則進行匹配 try { Regex myRegex; //檢查允許匹配 if (!Empty(eWebapp_AllowLink)) { myRegex = new Regex(eWebapp_AllowLink); if (myRegex.IsMatch(myPath)) { return false; } } //檢查禁止匹配 if (!Empty(eWebapp_NoLink)) { myRegex = new Regex(eWebapp_NoLink); if (myRegex.IsMatch(myPath)) { return true; } else { return false; } } return true; } catch { //如果匹配出錯，鏈接錯誤 return true; } } } else { //是否允許直接訪問文件 if (eWebapp_AllowOnlyFile) { return false; } else { return true; } } } }}