Download Manager: downloading files from secure location (classic ASP)

--DownloadManager.asp
<% Option Explicit %>
<% Response.Buffer=True %>
<%
'Constants
Const FOLDER_PATH="c:\Secure" 'full path to the secure folder
Const adTypeBinary = 1
Const adTypeText = 2
Const chunkSize = 2048

'global variables:
Dim strFileName 'name of the file to be downloaded
Dim blnForceDownload 'force the download or allow the file to be opened in the browser?

'read file from querystring:
strFileName=Request("file")

'force download?
blnForceDownload = (Request("force")="true")

'execute the function if we got anything:
If Len(strFileName)>0 Then
	Call DownloadFile (strFileName, blnForceDownload)
	Response.END
End If

Sub DownloadFile(strFileName, blnForceDownload)
	'local variables:
	Dim fso, objFile, strFilePath
	Dim fileSize, blnBinary, strContentType
	Dim objStream, strAllFile, iSz
	Dim i
	
	'----------------------
	'first step: verify the file exists
	'----------------------
	
	'build file path:
	strFilePath=FOLDER_PATH
	' add backslash if needed:
	If Right(strFilePath, 1)<>"\" Then strFilePath=strFilePath&"\"
	strFilePath=strFilePath&strFileName
	
	'initialize file system object:
	Set fso=Server.CreateObject("Scripting.FileSystemObject")
	
	'check that the file exists:
	If Not(fso.FileExists(strFilePath)) Then
		Set fso=Nothing
		Err.Raise 20000, "Download Manager", "Fatal Error: file does not exist: "&strFilePath
		Response.END
	End If
	
	'----------------------
	'second step: get file size.
	'----------------------
	Set objFile=fso.GetFile(strFilePath)
	fileSize=objFile.Size
	Set objFile=Nothing
	
	'----------------------
	'third step: check whether file is binary or not and get content type of the file. (according to its extension)
	'----------------------
	blnBinary=GetContentType(strFileName, strContentType)
	strAllFile=""
	
	'----------------------
	'forth step: read the file contents.
	'----------------------
	'force download? if so, add proper header:
	If blnForceDownload Then
	    	Response.AddHeader "Content-Disposition", "attachment; filename="&strFileName
	End If
	If blnBinary Then
		Set objStream=Server.CreateObject("ADODB.Stream")
		
		'Added to breakup chunk
		Response.Buffer = False 
		
		'this might be long...
	    	Server.ScriptTimeout = 30000
		

		
		'----------------------
		objStream.Open
		objStream.Type = 1 'adTypeBinary
		objStream.LoadFromFile strFilePath
		
		'Added to breakup chunk
		iSz = objStream.Size
		Response.AddHeader "Content-Length", iSz
		Response.Charset = "UTF-8"
		Response.ContentType = strContentType
		For i = 1 To iSz \ chunkSize
			If Not Response.IsClientConnected Then Exit For
			Response.BinaryWrite objStream.Read(chunkSize)
		Next 
		If iSz Mod chunkSize > 0 Then 
			If Response.IsClientConnected Then 
				Response.BinaryWrite objStream.Read(iSz Mod chunkSize)
			End If 
		End If
  		objStream.Close
		Set objStream = Nothing		
		'--------------------------------------
		'Commented out Original Code
		'strAllFile=objStream.Read(fileSize)
		'objStream.Close
		'Set objStream = Nothing
		'--------------------------------------
	Else  
		Set objFile=fso.OpenTextFile(strFilePath,1) 'forReading
		If Not(objFile.AtEndOfStream) Then
			strAllFile=objFile.ReadAll
		End If
		objFile.Close
		Set objFile=Nothing
		Response.Write(strAllFile)
	End If
	
	'clean up:
	Set fso=Nothing
	Response.Flush
	Response.END
End Sub

Function GetContentType(ByVal strName, ByRef ContentType)
	'return whether binary or not, put type into second parameter
	Dim strExtension
	strExtension="."&GetExtension(strName)
	Select Case strExtension
		Case ".asf"
			ContentType = "video/x-ms-asf"
			GetContentType=True
		Case ".avi"
			ContentType = "video/avi"
			GetContentType=True
		Case ".doc"
			ContentType = "application/msword"
			GetContentType=True
		Case ".zip"
			ContentType = "application/zip"
			GetContentType=True
		Case ".xls"
			ContentType = "application/vnd.ms-excel"
			GetContentType=True
		Case ".gif"
			ContentType = "image/gif"
			GetContentType=True
		Case ".jpg", ".jpeg"
			ContentType = "image/jpeg"
			GetContentType=True
		Case ".wav"
			ContentType = "audio/wav"
			GetContentType=True
		Case ".mp3"
			ContentType = "audio/mpeg3"
			GetContentType=True
		Case ".wma" 
			ContentType = "audio/wma"
			GetContentType=True
		Case ".mpg", ".mpeg"
			ContentType = "video/mpeg"
			GetContentType=True
		Case ".pdf"
			ContentType = "application/pdf"
			GetContentType=True
		Case ".rtf"
			ContentType = "application/rtf"
			GetContentType=True
		Case ".htm", ".html"
			ContentType = "text/html"
			GetContentType=False
		Case ".asp"
			ContentType = "text/asp"
			GetContentType=False
		Case ".txt"
			ContentType = "text/plain"
			GetContentType=False
		Case Else
			'Handle All Other Files
			ContentType = "application/octet-stream"
			GetContentType=True
	End Select
End Function

Function GetExtension(strName)
	Dim arrTmp
	arrTmp=Split(strName, ".")
	GetExtension=arrTmp(UBound(arrTmp))
End Function
%>

--DownloadExample.asp
<html>
<head>
<title>Download File Example</title>
</head>
<body>
<a href="DownloadManager.asp?file=testfile.txt&force=false">Download file without forcing Save As box</a><br />
<a href="DownloadManager.asp?file=testfile.txt&force=true">Download file (forcing Save As box)</a>
</body>
</html>

<% Option Explicit %>
<% Response.Buffer=True %>

<%

Call DownloadFile ("test.pdf",true)
 
Const FOLDER_PATH="D:\esther\files\" 'full path to the secure folder
Dim strFileName 'name of the file to be downloaded
strFileName=Request("file")



Sub DownloadFile(strFileName, blnForceDownload)
	Dim fso, objFile, strFilePath
	Dim fileSize, blnBinary, strContentType
	Dim objStream, strAllFile
	
	'----------------------
	'first step: verify the file exists
	'----------------------
	
	'build file path:
	strFilePath=FOLDER_PATH
	' add backslash if needed:
	If Right(strFilePath, 1)<>"\" Then strFilePath=strFilePath&"\"
	strFilePath=strFilePath&strFileName
	
	'initialize file system object:
	Set fso=Server.CreateObject("Scripting.FileSystemObject")
	
	'check that the file exists:
	If Not(fso.FileExists(strFilePath)) Then
		Set fso=Nothing
		Err.Raise 20000, "Download Manager", "Fatal Error: file does not exist: "&strFilePath
		Response.END
	End If
	
	'----------------------
	'second step: get file size.
	'----------------------
	Set objFile=fso.GetFile(strFilePath)
	fileSize=objFile.Size
	Set objFile=Nothing
	
	'----------------------
	'third step: check whether file is binary or not and get content type of the file. (according to its extension)
	'----------------------
	blnBinary=GetContentType(strFileName, strContentType)
	strAllFile=""
	
	'----------------------
	'forth step: read the file contents.
	'----------------------
	If blnBinary Then
		Set objStream=Server.CreateObject("ADODB.Stream")
		objStream.Open
		objStream.Type = 1 'adTypeBinary
		objStream.LoadFromFile strFilePath
		strAllFile=objStream.Read(fileSize)
		objStream.Close
		Set objStream = Nothing
	Else  
		Set objFile=fso.OpenTextFile(strFilePath,1) 'forReading
		If Not(objFile.AtEndOfStream) Then
			strAllFile=objFile.ReadAll
		End If
		objFile.Close
		Set objFile=Nothing
	End If
	
	'----------------------
	'final step: apply content type and send file contents to the browser
	'----------------------
	If blnForceDownload="true" Then
		Response.AddHeader "Content-Disposition", "attachment; filename="&strFileName
	End If
	Response.AddHeader "Content-Length", fileSize
	Response.Charset = "UTF-8"
	Response.ContentType = strContentType
	If blnBinary Then
		Response.BinaryWrite(strAllFile)
	Else  
		Response.Write(strAllFile)
	End If
	
	'clean up:
	Set fso=Nothing
	Response.Flush
	Response.END
End Sub

Function GetContentType(ByVal strName, ByRef ContentType)
	'return whether binary or not, put type into second parameter
	Dim strExtension
	strExtension="."&GetExtension(strName)
	Select Case strExtension
		Case ".asf"
			ContentType = "video/x-ms-asf"
			GetContentType=True
		Case ".avi"
			ContentType = "video/avi"
			GetContentType=True
		Case ".doc"
			ContentType = "application/msword"
			GetContentType=True
		Case ".zip"
			ContentType = "application/zip"
			GetContentType=True
		Case ".xls"
			ContentType = "application/vnd.ms-excel"
			GetContentType=True
		Case ".gif"
			ContentType = "image/gif"
			GetContentType=True
		Case ".jpg", ".jpeg"
			ContentType = "image/jpeg"
			GetContentType=True
		Case ".wav"
			ContentType = "audio/wav"
			GetContentType=True
		Case ".mp3"
			ContentType = "audio/mpeg3"
			GetContentType=True
		Case ".mpg", ".mpeg"
			ContentType = "video/mpeg"
			GetContentType=True
		Case ".rtf"
			ContentType = "application/rtf"
			GetContentType=True
		Case ".htm", ".html"
			ContentType = "text/html"
			GetContentType=False
		Case ".asp"
			ContentType = "text/asp"
			GetContentType=False
		Case ".txt"
			ContentType = "text/plain"
			GetContentType=False
		Case Else
			'Handle All Other Files
			ContentType = "application/octet-stream"
			GetContentType=True
	End Select
End Function

Function GetExtension(strName)
	Dim arrTmp
	arrTmp=Split(strName, ".")
	GetExtension=arrTmp(UBound(arrTmp))
End Function
%> 

DownloadFile ("test.pdf","true")

Case ".pdf"
			ContentType = "application/pdf"
			GetContentType=True