/*
*
* 防盗链ihttphandler
*
*
* 增加了对文件关键字的选择(即仅对文件名存在某些关键字或不存在某些关键字进行过滤)
* 设置web.config中<appsettings>节以下值
* string ewebapp_nolink 如果文件名符合该正确表态式将进行过滤(不设置对所有进行过滤)
* string ewebapp_allowlink 如果文件名符合该正确表态式将不进行过滤(优先权高于allowlink,不设置则服从allowlink)
* bool ewebapp_ allowonlyfile 如果为false,(默认true)则不允许用户直接对该文件进行访问建议为true
*
*
* :)以下设置均可省略,设置只是为了增加灵活性与体验
* ewebapp_nolink_message 错误信息提示:默认为link from:域名
* ewebapp_error_width 错误信息提示图片宽
* ewebapp_error_height 错误信息提示图片高
*
*
*
* 垃圾猪 2005-9-11 创建
* 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>
/// 防盗链ihttphandler
/// 参考http://www.softat.org/archiver/tid-52114.html
/// 垃圾猪 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: 在此处添加构造函数逻辑
//
}
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>
/// 输出错误信息
/// </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>
/// 输出真实文件
/// </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();
//这里选择输出的文件格式
//可以参考http://ewebapp.cnblogs.com/articles/234756.html增加对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>
/// 确认字符串是否为空
/// </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>
/// 检查是否是非法链接
/// </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是否存在网站的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
{
//这里使用正则表达对规则进行匹配
try
{
regex myregex;
//检查允许匹配
if (!empty(ewebapp_allowlink))
{
myregex = new regex(ewebapp_allowlink);
if (myregex.ismatch(mypath))
{
return false;
}
}
//检查禁止匹配
if (!empty(ewebapp_nolink))
{
myregex = new regex(ewebapp_nolink);
if (myregex.ismatch(mypath))
{
return true;
}
else
{
return false;
}
}
return true;
}
catch
{
//如果匹配出错，链接错误
return true;
}
}
}
else
{
//是否允许直接访问文件
if (ewebapp_allowonlyfile)
{
return false;
}
else
{
return true;
}
}
}
}
}
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