用Asp隐藏文件路径，实现防盗链

仁武君

　　如果我们知道一个静态文件的实际路径如：<a href="http://www.xx.com/download/51windows.pdf" target="_blank" >http://www.xx.com/download/51windows.pdf</A>，如果服务器没有作特别的限制设置，我们就可以毫不费力的把它下载下来！当网站提供51windows.pdf下载时，怎么样才能让下载者无法得到他的实际路径呢！本文就来介绍如何使用Asp来隐藏文件的实际下载路径。<BR><BR>　　我们在管理网站文件时，可以把扩展名一样的文件放在同一个目录下，起一个比较特别名字，例如放pdf文件目录为the_pdf_file_s，把下面代码另存为down.asp，他的网上路径为http://www.xx.com/down.asp，我们就可以用http://www.xx.com/down.asp?FileName=51windows.pdf来下载这个文件了，而且下载者无法看到这个文件实际下载路径的！在down.asp中我们还可以设置下载文件是否需要登陆，判断下载的来源页是否为外部网站，从而可以做到防止文件被盗链。<BR><BR>示例代码：<BR>
<DIV class=code_head>引用内容：</DIV>
<DIV class=code_main>&lt;%<BR>From_url = Cstr(Request.ServerVariables("HTTP_REFERER"))<BR>Serv_url = Cstr(Request.ServerVariables("SERVER_NAME"))<BR>if mid(From_url,8,len(Serv_url)) &lt;&gt; Serv_url then<BR> response.write "非法链接！" '防止盗链<BR> response.end<BR>end if<BR><BR>if Request.Cookies("Logined")="" then<BR> response.redirect "/login.asp" '需要登陆！<BR>end if<BR>Function GetFileName(longname)'/folder1/folder2/file.asp=&gt;file.asp<BR> while instr(longname,"/")<BR>  longname = right(longname,len(longname)-1)<BR> wend<BR> GetFileName = longname<BR>End Function<BR>Dim Stream<BR>Dim Contents<BR>Dim FileName<BR>Dim TrueFileName<BR>Dim FileExt<BR>Const adTypeBinary = 1<BR>FileName = Request.QueryString("FileName")<BR>if FileName = "" Then<BR>    Response.Write "无效文件名！"<BR>    Response.End<BR>End if<BR>FileExt = Mid(FileName, InStrRev(FileName, ".") + 1)<BR>Select Case UCase(FileExt)<BR>    Case "ASP", "ASA", "ASPX", "ASAX", "MDB"<BR>        Response.Write "非法操作！"<BR>        Response.End<BR>End Select<BR>Response.Clear<BR>if lcase(right(FileName,3))="gif" or lcase(right(FileName,3))="jpg" or lcase(right(FileName,3))="png" then<BR> Response.ContentType = "image/*" '对图像文件不出现下载对话框<BR>else<BR> Response.ContentType = "application/ms-download"<BR>end if<BR>Response.AddHeader "content-disposition", "attachment; filename=" &amp; GetFileName(Request.QueryString("FileName"))<BR>Set Stream = server.CreateObject("ADODB.Stream")<BR>Stream.Type = adTypeBinary<BR>Stream.Open<BR>if lcase(right(FileName,3))="pdf" then '设置pdf类型文件目录<BR> TrueFileName = "/the_pdf_file_s/"&amp;FileName<BR>end if <BR>if lcase(right(FileName,3))="doc" then '设置DOC类型文件目录<BR> TrueFileName = "/my_D_O_C_file/"&amp;FileName<BR>end if<BR>if lcase(right(FileName,3))="gif" or lcase(right(FileName,3))="jpg" or lcase(right(FileName,3))="png" then<BR> TrueFileName = "/all_images_/"&amp;FileName '设置图像文件目录<BR>end if<BR>Stream.LoadFromFile Server.MapPath(TrueFileName)<BR>While Not Stream.EOS<BR>    Response.BinaryWrite Stream.Read(1024 * 64)<BR>Wend<BR>Stream.Close<BR>Set Stream = Nothing<BR>Response.Flush<BR>Response.End<BR>%&gt;<BR></DIV>