=**************************************
    = Name: Resume download and mask file lo
    =     cation script
    = Description:This CGI script can be use
    =     d to hide the actual location of files o
    =     n your website by masking. All files can
    =     be downloaded through this script so you
    =     can keep track of who is downloading wha
    =     t or simply restricting access. This scr
    =     ipt also fully supports resumed download
    =     s (GetRight, Download Accelerator etc). 
    =     Please vote if you find this script usef
    =     ul.
    = By: TiCaL
    =
    = Inputs:The only parameter this Perl sc
    =     ript accepts is 'file'. Eg. download.pl?
    =     file=somethin.zip
    =
    =This code is copyrighted and has    = limited warranties.Please see http://w
    =     ww.Planet-Source-Code.com/vb/scripts/Sho
    =     wCode.asp?txtCodeId=532&lngWId;=6    =for details.    =**************************************
    
    #!/usr/bin/perl
    # Change the line above to suit your system
    # Disable buffered output
    $|++;
    # Attachment fix for Internet Explorer 5.5
    $browser = $ENV{'HTTP_USER_AGENT'};
    $isIE55 = ($browser =~ m/MSIE 5.5/g);
    $disp = "attachment;";
    if($isIE55 != 0)
    {
    	$disp = "";
    }
    # Get the filename parameter
    use CGI;
    $query = new CGI;
    $filename = $query->param('file');
    # Check if file parameter exists
    if(!($filename))
    {
    	# Redirect user to an error page
    	print "Location: 404.html\n\n";
    	# Exit script
    	exit 0;
    }
    # this is the directory where you hide your files
    $hidden_location = "myhiddenfolderpath";
    # remove all backreferences from filename
    # this is to stop hackers passing ../../../ type paths with the filename
    $filename =~ s/.*[\:\/\\](.*)/$1/;
    # check if file exists and if not show 404
    if(!(-e "$hidden_location/$filename"))
    {
    	# Redirect user to an error page
    	print "Location: 404.html\n\n";
    	# Exit script
    	exit 0;
    }
    # get the HTTP_RANGE enviroment variable is the client wishes to resume file download
    my $http_range = $ENV{HTTP_RANGE};
    my $range_start = 0;
    my $filesize = 0;
    # get the size of the file in bytes
    $filesize = -s "$hidden_location/$filename";
    # create default Content-Length and Content-Range header lines
    my $cl = "Content-Length: $filesize\nContent-Range: bytes 0-".($filesize-1)."/$filesize\n";
    # if the HTTP_RANGE variable exists
    if ($http_range) 
    {
    	# we extract try to extract the file offset --> $1
    	if ($http_range =~ m/^bytes=(\d*)-(\d*)$/) 
    	{
    		# if we don't find anything we default to offset 0
    		$range_start = $1 || 0;
    		$range_end= $2 || $filesize;
    		# if the requested range is larger than the file itself we have a bad request
    		if ($range_end > $filesize) 
    		{
    			# so we set our variables to defaults
    			$range_start = 0;
    			$cl = "Content-Length: $filesize\nContent-Range: bytes 0-".($filesize-1)."/$filesize\n";
    		}
    		# we have succesfully extracted the byte range requested so we recreate the header with proper info
    		$cl = "Content-Range: bytes $range_start-".($filesize-1)."/$filesize\n";
    		$cl .= "Content-Length: ".($filesize-$range_start)."\n";		
    	} 
    	else 
    	{
    		# if we are here it means that the HTTP_RANGE variable was malformed so we default our variables
    		$range_start = 0;
    		$cl = "Content-Length: $filesize\nContent-Range: bytes 0-".($filesize-1)."/$filesize\n";
    	}	
    }
    # Now we print the header
    # First tell client that we can resume downloads
    print "Accept-ranges: bytes\n";
    # Then print our Content-Length and Content-Range 
    print "$cl"; 
    # Now we force the browser to pop-up the save as dialogue
    print "Content-Disposition:$disp filename=$filename\n"; 
    print "Content-Type:application/x-download\n\n"; 
    # variable which will contain the partial file data when someone resumes
    my $filebuf;
    # Lets open the file so we can send it to the client
    open(DLFILE, "<$hidden_location/$filename") || die "Unable to open $filename because $!.\n";
    # Change to binary mode if operating system is Windows
    binmode(DLFILE) if $^O eq 'MSWin32';
    # If we are starting from 0 (not resuming) copy the file contents into fileholder array
    if($range_start == 0)
    {
    	@fileholder = <DLFILE>; 
    }
    else
    {
    	# We need to read the file data starting from requested offset
    	seek(DLFILE, $range_start, 0);
    	read(DLFILE, $filebuf, $filesize-$range_start); 
    }
    # Close the file
    close (DLFILE); 
    # Now we send the file to the client
    if($range_start == 0)
    {
    	# If we are not resuming
    	print @fileholder;
    }
    else
    {
    	# If we are resuming
    	print $filebuf;
    }
    # Exit script
    exit 0;