/*
   Copyright (C) 2002 MySQL AB

      This program is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation; either version 2 of the License, or
      (at your option) any later version.

      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.

      You should have received a copy of the GNU General Public License
      along with this program; if not, write to the Free Software
      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */
package com.mysql.jdbc;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;


/**
 * Methods for doing secure authentication with MySQL-4.1
 * and newer.
 *
 * @author Mark Matthews
 *
 * @version $Id: Security.java,v 1.1.4.4 2003/09/11 19:34:01 mmatthew Exp $
 */
class Security {
    private static final int SHA1_HASH_SIZE = 20;
    private static final char PVERSION41_CHAR = '*';

    /**
     * Prevent construction.
     */
    private Security() {
        super();
    }

    /*
      Convert password in salted form to binary string password and hash-salt
      For old password this involes one more hashing

      SYNOPSIS
            get_hash_and_password()
            salt         IN  Salt to convert from
            pversion     IN  Password version to use
            hash         OUT Store zero ended hash here
            bin_password OUT Store binary password here (no zero at the end)

      RETURN
            0 for pre 4.1 passwords
       !0 password version char for newer passwords
    */

    /**
     * DOCUMENT ME!
     *
     * @param salt DOCUMENT ME!
     * @param usingNewPasswords DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     *
     * @throws NoSuchAlgorithmException if the message digest 'SHA-1' is not
     * available.
     */
    static byte[] getBinaryPassword(int[] salt, boolean usingNewPasswords)
        throws NoSuchAlgorithmException {
        int val = 0;

        byte[] binaryPassword = new byte[SHA1_HASH_SIZE]; /* Binary password loop pointer */

        if (usingNewPasswords) /* New password version assumed */ {
            int pos = 0;

            for (int i = 0; i < 4; i++) /* Iterate over these elements*/ {
                val = salt[i];

                for (int t = 3; t >= 0; t--) {
                    binaryPassword[pos++] = (byte) (val & 255);
                    val >>= 8; /* Scroll 8 bits to get next part*/
                }
            }

            return binaryPassword;
        } else {
            int offset = 0;

            for (int i = 0; i < 2; i++) /* Iterate over these elements*/ {
                val = salt[i];

                for (int t = 3; t >= 0; t--) {
                    binaryPassword[t + offset] = (byte) (val % 256);
                    val >>= 8; /* Scroll 8 bits to get next part*/
                }

                offset += 4;
            }

            MessageDigest md = MessageDigest.getInstance("SHA-1");

            md.update(binaryPassword, 0, 8);

            return md.digest();
        }
    }

    /**
     * Creates key from old password to decode scramble
     * Used in 4.1 authentication with passwords stored
     * pre-4.1 hashing.
     *
     * @param passwd the password to create the key from
     *
     * @return 20 byte generated key
     *
     * @throws NoSuchAlgorithmException if the message digest 'SHA-1'
     *          is not available.
     */
    static byte[] createKeyFromOldPassword(String passwd)
        throws NoSuchAlgorithmException {
        /* At first hash password to the string stored in password */
        passwd = makeScrambledPassword(passwd);

        /* Now convert it to the salt form */
        int[] salt = getSaltFromPassword(passwd);

        /* Finally get hash and bin password from salt */
        return getBinaryPassword(salt, false);
    }

    /**
     * Creates password to be stored in user database
     * from raw string.
     *
     * Handles Pre-MySQL 4.1 passwords.
     *
     * @param password plaintext password
     *
     * @return scrambled password
     *
     * @throws NoSuchAlgorithmException if the message digest 'SHA-1' is not
     *          available.
     */
    static String makeScrambledPassword(String password)
        throws NoSuchAlgorithmException {
        long[] passwordHash = Util.newHash(password);
        StringBuffer scramble = new StringBuffer();

        scramble.append(longToHex(passwordHash[0]));
        scramble.append(longToHex(passwordHash[1]));

        return scramble.toString();
    }

    /**
     * Encrypt/Decrypt function used for password encryption in authentication
     *
     * Simple XOR is used here but it is OK as we crypt random strings
     *
     * @param from     IN     Data for encryption
     * @param to       OUT    Encrypt data to the buffer (may be the same)
     * @param password IN     Password used for encryption (same length)
     * @param length   IN     Length of data to encrypt
     */
    static void passwordCrypt(byte[] from, byte[] to, byte[] password,
        int length) {
        int pos = 0;

        while ((pos < from.length) && (pos < length)) {
            to[pos] = (byte) (from[pos] ^ password[pos]);
            pos++;
        }
    }

    /**
     * Stage one password hashing, used in MySQL 4.1 password handling
     *
     * @param password plaintext password
     *
     * @return stage one hash of password
     *
     * @throws NoSuchAlgorithmException if the message digest 'SHA-1' is not
     *          available.
     */
    static byte[] passwordHashStage1(String password)
        throws NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance("SHA-1");
        StringBuffer cleansedPassword = new StringBuffer();

        int passwordLength = password.length();

        for (int i = 0; i < passwordLength; i++) {
            char c = password.charAt(i);

            if ((c == ' ') || (c == '\t')) {
                continue; /* skip space in password */
            }

            cleansedPassword.append(c);
        }

        return md.digest(cleansedPassword.toString().getBytes());
    }

    /**
     * Stage two password hashing used in MySQL 4.1
     * password handling
     *
     * @param hash from passwordHashStage1
     * @param salt salt used for stage two hashing
     *
     * @return result of stage two password hash
     *
     * @throws NoSuchAlgorithmException if the message digest 'SHA-1' is not
     * available.
     */
    static byte[] passwordHashStage2(byte[] hashedPassword, byte[] salt)
        throws NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance("SHA-1");

        // hash 4 bytes of salt
        md.update(salt, 0, 4);

        md.update(hashedPassword, 0, SHA1_HASH_SIZE);

        return md.digest();
    }

    private static int[] getSaltFromPassword(String password) {
        int[] result = new int[6];

        if ((password == null) || (password.length() == 0)) {
            return result;
        }

        if (password.charAt(0) == PVERSION41_CHAR) {
            // new password
            String saltInHex = password.substring(1, 5);

            int val = 0;

            for (int i = 0; i < 4; i++) {
                val = (val << 4) + charVal(saltInHex.charAt(i));
            }

            return result;
        } else {
            int resultPos = 0;
            int pos = 0;
            int length = password.length();

            while (pos < length) {
                int val = 0;

                for (int i = 0; i < 8; i++) {
                    val = (val << 4) + charVal(password.charAt(pos++));
                }

                result[resultPos++] = val;
            }

            return result;
        }
    }

    /**
     * Returns hex value for given char
     */
    private static int charVal(char c) {
        return (int) (((c >= '0') && (c <= '9')) ? (c - '0')
                                                 : (((c >= 'A') && (c <= 'Z'))
        ? (c - 'A' + 10) : (c - 'a' + 10)));
    }

    private static String longToHex(long val) {
        String longHex = Long.toHexString(val);

        int length = longHex.length();

        if (length < 8) {
            int padding = 8 - length;
            StringBuffer buf = new StringBuffer();

            for (int i = 0; i < padding; i++) {
                buf.append("0");
            }

            buf.append(longHex);

            return buf.toString();
        } else {
            return longHex.substring(0, 8);
        }
    }

	//	SERVER:  public_seed=create_random_string()
		//			 send(public_seed)
		//
		//	CLIENT:  recv(public_seed)
		//			 hash_stage1=sha1("password")
		//			 hash_stage2=sha1(hash_stage1)
		//			 reply=xor(hash_stage1, sha1(public_seed,hash_stage2)
		//
		//			 // this three steps are done in scramble()
		//
		//			 send(reply)
		//
		//
		//	SERVER:  recv(reply)
		//			 hash_stage1=xor(reply, sha1(public_seed,hash_stage2))
		//			 candidate_hash2=sha1(hash_stage1)
		//			 check(candidate_hash2==hash_stage2)
		
	static byte[] scramble411(String password, String seed) throws NoSuchAlgorithmException {
		MessageDigest md = MessageDigest.getInstance("SHA-1");
		
		byte[] passwordHashStage1 = md.digest(password.getBytes());
		md.reset();
		byte[] passwordHashStage2 = md.digest(passwordHashStage1);
		md.reset();
		byte[] seedAsBytes = seed.getBytes(); // for debugging
		md.update(seedAsBytes);
		md.update(passwordHashStage2);
		
		byte[] toBeXord = md.digest();
		
		int numToXor = toBeXord.length;
		
		for (int i = 0; i < numToXor; i++) {
			toBeXord[i] = (byte)(toBeXord[i] ^ passwordHashStage1[i]);
		}
		
		return toBeXord;
		
	}
}