Anti-leech ihttphandler

/*
*
* Anti-leech ihttphandler
*
*
* Added the selection of file keywords (I .e., filtering only some keywords or some keywords in the file name)
* Set the following values in the <etettings> section of Web. config:
* String ewebapp_nolink: if the file name complies with the correct statement, the file will be filtered (not set to filter all files)
* String ewebapp_allowlink: if the file name complies with the correct statement, no filtering will be performed (the priority is higher than allowlink, And the allowlink is obeyed if the parameter is not set)
* If bool ewebapp _ allowonlyfile is false (true by default), it is recommended that you do not allow direct access to this file.
*
*
* :) The following settings can be omitted only to increase flexibility and experience.
* Ewebapp_nolink_message error message: link from: domain name by default
* The error message "ewebapp_error_width" indicates the image width.
* The error message "ewebapp_error_height" indicates the Image Height.
*
*
*
* Create a pig-9-11
* 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>
/// Anti-leech ihttphandler
// Reference http://www.softat.org/archiver/tid-52114.html
/// Fixed the error-9-12
/// </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: add the constructor logic here
//
}

Public void processrequest (httpcontext context)
{
Ewebapp_nolink_message = configurationsettings. receivettings ["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>
/// Output error message
/// </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. receivettings ["ewebapp_error_width"]);
If (_ myerrorwidth> 0)
{
Myerrorwidth = _ myerrorwidth;
}

}
Catch
{

}
Try
{
Int _ myerrorheight = convert. toint32 (configurationsettings. receivettings ["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>
/// Output real files
/// </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 ();

// Select the output file format
// For more file formats, see http://ewebapp.cnblogs.com/articles/234756.html.

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>
/// Check whether the string is null
/// </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>
/// Check whether the link is illegal
/// </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. receivettings ["ewebapp_nolink"];
Ewebapp_allowlink = configurationsettings. receivettings ["ewebapp_allowlink"];

Try
{
Ewebapp_allowonlyfile = convert. toboolean (configurationsettings. deleettings ["ewebapp_allowonlyfile"]);
}
Catch
{
Ewebapp_allowonlyfile = true;
}

If (context. Request. urlreferrer! = NULL)
{

// Determine whether the referdomain has a website IP address or domain name
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
{
// Use regular expression to match the rule
Try
{
RegEx myregex;

// Check whether matching is allowed
If (! Empty (ewebapp_allowlink ))
{

Myregex = new RegEx (ewebapp_allowlink );

If (myregex. ismatch (mypath ))
{
Return false;
}

}

// Check whether matching is prohibited
If (! Empty (ewebapp_nolink ))
{

Myregex = new RegEx (ewebapp_nolink );
If (myregex. ismatch (mypath ))
{
Return true;
}
Else
{
Return false;
}

}

Return true;

}< br> catch
{< br> // If a matching error occurs, the link is incorrect.
return true;
}< BR >}< br> else
{< br> // whether direct file access is allowed
If (ewebapp_allowonlyfile)
{< br> return false;
}< br> else
{< br> return true;
}< BR >}< br> posting