/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */

package org.apache.asyncweb.client.auth;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;

import org.apache.asyncweb.client.util.EncodingUtil;
import org.apache.commons.codec.binary.Base64;

/**
 * Provides an implementation of the NTLM authentication protocol.
 * <p>
 * This class provides methods for generating authentication
 * challenge responses for the NTLM authentication protocol.  The NTLM
 * protocol is a proprietary Microsoft protocol and as such no RFC
 * exists for it.  This class is based upon the reverse engineering
 * efforts of a wide range of people.</p>
 *
 * <p>Please note that an implementation of JCE must be correctly installed and configured when
 * using NTLM support.</p>
 *
 * <p>This class should not be used externally to HttpClient as it's API is specifically
 * designed to work with HttpClient's use case, in particular it's connection management.</p>
 *
 * @author <a href="mailto:adrian@ephox.com">Adrian Sutton</a>
 * @author <a href="mailto:jsdever@apache.org">Jeff Dever</a>
 * @author <a href="mailto:mbowler@GargoyleSoftware.com">Mike Bowler</a>
 */
final class NTLM {
    /** Character encoding */
    public static final String DEFAULT_CHARSET = "ASCII";

    /** The current response */
    private byte[] currentResponse;

    /** The current position */
    private int currentPosition = 0;

    /** The character set to use for encoding the credentials */
    private String credentialCharset = DEFAULT_CHARSET;

    /**
     * Returns the response for the given message.
     *
     * @param message the message that was received from the server.
     * @param username the username to authenticate with.
     * @param password the password to authenticate with.
     * @param host The host.
     * @param domain the NT domain to authenticate in.
     * @return The response.
     * @throws AuthenticationException If the messages cannot be retrieved.
     */
    public final String getResponseFor(String message,
            String username, String password, String host, String domain)
            throws AuthenticationException {

        final String response;
        if (message == null || message.trim().equals("")) {
            response = getType1Message(host, domain);
        } else {
            response = getType3Message(username, password, host, domain,
                    parseType2Message(message));
        }
        return response;
    }

    /**
     * Return the cipher for the specified key.
     * @param key The key.
     * @return Cipher The cipher.
     * @throws AuthenticationException If the cipher cannot be retrieved.
     */
    private Cipher getCipher(byte[] key) throws AuthenticationException {
        try {
            final Cipher ecipher = Cipher.getInstance("DES/ECB/NoPadding");
            key = setupKey(key);
            ecipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "DES"));
            return ecipher;
        } catch (NoSuchAlgorithmException e) {
            throw new AuthenticationException("DES encryption is not available.", e);
        } catch (InvalidKeyException e) {
            throw new AuthenticationException("Invalid key for DES encryption.", e);
        } catch (NoSuchPaddingException e) {
            throw new AuthenticationException(
                "NoPadding option for DES is not available.", e);
        }
    }

    /**
     * Adds parity bits to the key.
     * @param key56 The key
     * @return The modified key.
     */
    private byte[] setupKey(byte[] key56) {
        byte[] key = new byte[8];
        key[0] = (byte) ((key56[0] >> 1) & 0xff);
        key[1] = (byte) ((((key56[0] & 0x01) << 6)
            | (((key56[1] & 0xff) >> 2) & 0xff)) & 0xff);
        key[2] = (byte) ((((key56[1] & 0x03) << 5)
            | (((key56[2] & 0xff) >> 3) & 0xff)) & 0xff);
        key[3] = (byte) ((((key56[2] & 0x07) << 4)
            | (((key56[3] & 0xff) >> 4) & 0xff)) & 0xff);
        key[4] = (byte) ((((key56[3] & 0x0f) << 3)
            | (((key56[4] & 0xff) >> 5) & 0xff)) & 0xff);
        key[5] = (byte) ((((key56[4] & 0x1f) << 2)
            | (((key56[5] & 0xff) >> 6) & 0xff)) & 0xff);
        key[6] = (byte) ((((key56[5] & 0x3f) << 1)
            | (((key56[6] & 0xff) >> 7) & 0xff)) & 0xff);
        key[7] = (byte) (key56[6] & 0x7f);

        for (int i = 0; i < key.length; i++) {
            key[i] = (byte) (key[i] << 1);
        }
        return key;
    }

    /**
     * Encrypt the data.
     * @param key The key.
     * @param bytes The data
     * @return byte[] The encrypted data
     * @throws AuthenticationException If {@link javax.crypto.Cipher#doFinal(byte[])} fails
     */
    private byte[] encrypt(byte[] key, byte[] bytes)
        throws AuthenticationException {
        Cipher ecipher = getCipher(key);
        try {
            byte[] enc = ecipher.doFinal(bytes);
            return enc;
        } catch (IllegalBlockSizeException e) {
            throw new AuthenticationException("Invalid block size for DES encryption.", e);
        } catch (BadPaddingException e) {
            throw new AuthenticationException("Data not padded correctly for DES encryption.", e);
        }
    }

    /**
     * Prepares the object to create a response of the given length.
     * @param length the length of the response to prepare.
     */
    private void prepareResponse(int length) {
        currentResponse = new byte[length];
        currentPosition = 0;
    }

    /**
     * Adds the given byte to the response.
     * @param b the byte to add.
     */
    private void addByte(byte b) {
        currentResponse[currentPosition] = b;
        currentPosition++;
    }

    /**
     * Adds the given bytes to the response.
     * @param bytes the bytes to add.
     */
    private void addBytes(byte[] bytes) {
        for (int i = 0; i < bytes.length; i++) {
            currentResponse[currentPosition] = bytes[i];
            currentPosition++;
        }
    }

    /**
     * Returns the response that has been generated after shrinking the array if
     * required and base64 encodes the response.
     * @return The response as above.
     */
    private String getResponse() {
        byte[] resp;
        if (currentResponse.length > currentPosition) {
            byte[] tmp = new byte[currentPosition];
            for (int i = 0; i < currentPosition; i++) {
                tmp[i] = currentResponse[i];
            }
            resp = tmp;
        } else {
            resp = currentResponse;
        }
        return EncodingUtil.getAsciiString(Base64.encodeBase64(resp));
    }

    /**
     * Creates the first message (type 1 message) in the NTLM authentication sequence.
     * This message includes the user name, domain and host for the authentication session.
     *
     * @param host the computer name of the host requesting authentication.
     * @param domain The domain to authenticate with.
     * @return String the message to add to the HTTP request header.
     */
    public String getType1Message(String host, String domain) {
        host = host.toUpperCase();
        domain = domain.toUpperCase();
        byte[] hostBytes = EncodingUtil.getBytes(host, DEFAULT_CHARSET);
        byte[] domainBytes = EncodingUtil.getBytes(domain, DEFAULT_CHARSET);

        int finalLength = 32 + hostBytes.length + domainBytes.length;
        prepareResponse(finalLength);

        // The initial id string.
        byte[] protocol = EncodingUtil.getBytes("NTLMSSP", DEFAULT_CHARSET);
        addBytes(protocol);
        addByte((byte) 0);

        // Type
        addByte((byte) 1);
        addByte((byte) 0);
        addByte((byte) 0);
        addByte((byte) 0);

        // Flags
        addByte((byte) 6);
        addByte((byte) 82);
        addByte((byte) 0);
        addByte((byte) 0);

        // Domain length (first time).
        int iDomLen = domainBytes.length;
        byte[] domLen = convertShort(iDomLen);
        addByte(domLen[0]);
        addByte(domLen[1]);

        // Domain length (second time).
        addByte(domLen[0]);
        addByte(domLen[1]);

        // Domain offset.
        byte[] domOff = convertShort(hostBytes.length + 32);
        addByte(domOff[0]);
        addByte(domOff[1]);
        addByte((byte) 0);
        addByte((byte) 0);

        // Host length (first time).
        byte[] hostLen = convertShort(hostBytes.length);
        addByte(hostLen[0]);
        addByte(hostLen[1]);

        // Host length (second time).
        addByte(hostLen[0]);
        addByte(hostLen[1]);

        // Host offset (always 32).
        byte[] hostOff = convertShort(32);
        addByte(hostOff[0]);
        addByte(hostOff[1]);
        addByte((byte) 0);
        addByte((byte) 0);

        // Host String.
        addBytes(hostBytes);

        // Domain String.
        addBytes(domainBytes);

        return getResponse();
    }

    /**
     * Extracts the server nonce out of the given message type 2.
     *
     * @param message the String containing the base64 encoded message.
     * @return an array of 8 bytes that the server sent to be used when
     * hashing the password.
     */
    public byte[] parseType2Message(String message) {
        // Decode the message first.
        byte[] msg = Base64.decodeBase64(EncodingUtil.getBytes(message, DEFAULT_CHARSET));
        byte[] nonce = new byte[8];
        // The nonce is the 8 bytes starting from the byte in position 24.
        for (int i = 0; i < 8; i++) {
            nonce[i] = msg[i + 24];
        }
        return nonce;
    }

    /**
     * Creates the type 3 message using the given server nonce.  The type 3 message includes all the
     * information for authentication, host, domain, username and the result of encrypting the
     * nonce sent by the server using the user's password as the key.
     *
     * @param user The user name.  This should not include the domain name.
     * @param password The password.
     * @param host The host that is originating the authentication request.
     * @param domain The domain to authenticate within.
     * @param nonce the 8 byte array the server sent.
     * @return The type 3 message.
     * @throws AuthenticationException If {@encrypt(byte[],byte[])} fails.
     */
    public String getType3Message(String user, String password,
            String host, String domain, byte[] nonce)
    throws AuthenticationException {

        int ntRespLen = 0;
        int lmRespLen = 24;
        domain = domain.toUpperCase();
        host = host.toUpperCase();
        user = user.toUpperCase();
        byte[] domainBytes = EncodingUtil.getBytes(domain, DEFAULT_CHARSET);
        byte[] hostBytes = EncodingUtil.getBytes(host, DEFAULT_CHARSET);
        byte[] userBytes = EncodingUtil.getBytes(user, credentialCharset);
        int domainLen = domainBytes.length;
        int hostLen = hostBytes.length;
        int userLen = userBytes.length;
        int finalLength = 64 + ntRespLen + lmRespLen + domainLen
            + userLen + hostLen;
        prepareResponse(finalLength);
        byte[] ntlmssp = EncodingUtil.getBytes("NTLMSSP", DEFAULT_CHARSET);
        addBytes(ntlmssp);
        addByte((byte) 0);
        addByte((byte) 3);
        addByte((byte) 0);
        addByte((byte) 0);
        addByte((byte) 0);

        // LM Resp Length (twice)
        addBytes(convertShort(24));
        addBytes(convertShort(24));

        // LM Resp Offset
        addBytes(convertShort(finalLength - 24));
        addByte((byte) 0);
        addByte((byte) 0);

        // NT Resp Length (twice)
        addBytes(convertShort(0));
        addBytes(convertShort(0));

        // NT Resp Offset
        addBytes(convertShort(finalLength));
        addByte((byte) 0);
        addByte((byte) 0);

        // Domain length (twice)
        addBytes(convertShort(domainLen));
        addBytes(convertShort(domainLen));

        // Domain offset.
        addBytes(convertShort(64));
        addByte((byte) 0);
        addByte((byte) 0);

        // User Length (twice)
        addBytes(convertShort(userLen));
        addBytes(convertShort(userLen));

        // User offset
        addBytes(convertShort(64 + domainLen));
        addByte((byte) 0);
        addByte((byte) 0);

        // Host length (twice)
        addBytes(convertShort(hostLen));
        addBytes(convertShort(hostLen));

        // Host offset
        addBytes(convertShort(64 + domainLen + userLen));

        for (int i = 0; i < 6; i++) {
            addByte((byte) 0);
        }

        // Message length
        addBytes(convertShort(finalLength));
        addByte((byte) 0);
        addByte((byte) 0);

        // Flags
        addByte((byte) 6);
        addByte((byte) 82);
        addByte((byte) 0);
        addByte((byte) 0);

        addBytes(domainBytes);
        addBytes(userBytes);
        addBytes(hostBytes);
        addBytes(hashPassword(password, nonce));
        return getResponse();
    }

    /**
     * Creates the LANManager and NT response for the given password using the
     * given nonce.
     * @param password the password to create a hash for.
     * @param nonce the nonce sent by the server.
     * @return The response.
     * @throws AuthenticationException If {@link #encrypt(byte[],byte[])} fails.
     */
    private byte[] hashPassword(String password, byte[] nonce)
        throws AuthenticationException {
        byte[] passw = EncodingUtil.getBytes(password.toUpperCase(), credentialCharset);
        byte[] lmPw1 = new byte[7];
        byte[] lmPw2 = new byte[7];

        int len = passw.length;
        if (len > 7) {
            len = 7;
        }

        int idx;
        for (idx = 0; idx < len; idx++) {
            lmPw1[idx] = passw[idx];
        }
        for (; idx < 7; idx++) {
            lmPw1[idx] = (byte) 0;
        }

        len = passw.length;
        if (len > 14) {
            len = 14;
        }
        for (idx = 7; idx < len; idx++) {
            lmPw2[idx - 7] = passw[idx];
        }
        for (; idx < 14; idx++) {
            lmPw2[idx - 7] = (byte) 0;
        }

        // Create LanManager hashed Password
        byte[] magic = {
            (byte) 0x4B, (byte) 0x47, (byte) 0x53, (byte) 0x21,
            (byte) 0x40, (byte) 0x23, (byte) 0x24, (byte) 0x25
        };

        byte[] lmHpw1;
        lmHpw1 = encrypt(lmPw1, magic);

        byte[] lmHpw2 = encrypt(lmPw2, magic);

        byte[] lmHpw = new byte[21];
        for (int i = 0; i < lmHpw1.length; i++) {
            lmHpw[i] = lmHpw1[i];
        }
        for (int i = 0; i < lmHpw2.length; i++) {
            lmHpw[i + 8] = lmHpw2[i];
        }
        for (int i = 0; i < 5; i++) {
            lmHpw[i + 16] = (byte) 0;
        }

        // Create the responses.
        byte[] lmResp = new byte[24];
        calcResp(lmHpw, nonce, lmResp);

        return lmResp;
    }

    /**
     * Takes a 21 byte array and treats it as 3 56-bit DES keys.  The 8 byte
     * plaintext is encrypted with each key and the resulting 24 bytes are
     * stored in the results array.
     *
     * @param keys The keys.
     * @param plaintext The plain text to encrypt.
     * @param results Where the results are stored.
     * @throws AuthenticationException If {@link #encrypt(byte[],byte[])} fails.
     */
    private void calcResp(byte[] keys, byte[] plaintext, byte[] results)
        throws AuthenticationException {
        byte[] keys1 = new byte[7];
        byte[] keys2 = new byte[7];
        byte[] keys3 = new byte[7];
        for (int i = 0; i < 7; i++) {
            keys1[i] = keys[i];
        }

        for (int i = 0; i < 7; i++) {
            keys2[i] = keys[i + 7];
        }

        for (int i = 0; i < 7; i++) {
            keys3[i] = keys[i + 14];
        }
        byte[] results1 = encrypt(keys1, plaintext);

        byte[] results2 = encrypt(keys2, plaintext);

        byte[] results3 = encrypt(keys3, plaintext);

        for (int i = 0; i < 8; i++) {
            results[i] = results1[i];
        }
        for (int i = 0; i < 8; i++) {
            results[i + 8] = results2[i];
        }
        for (int i = 0; i < 8; i++) {
            results[i + 16] = results3[i];
        }
    }

    /**
     * Converts a given number to a two byte array in little endian order.
     * @param num the number to convert.
     * @return The byte representation of <i>num</i> in little endian order.
     */
    private byte[] convertShort(int num) {
        byte[] val = new byte[2];
        String hex = Integer.toString(num, 16);
        while (hex.length() < 4) {
            hex = "0" + hex;
        }
        String low = hex.substring(2, 4);
        String high = hex.substring(0, 2);

        val[0] = (byte) Integer.parseInt(low, 16);
        val[1] = (byte) Integer.parseInt(high, 16);
        return val;
    }

    /**
     * @return Returns the credentialCharset.
     */
    public String getCredentialCharset() {
        return credentialCharset;
    }

    /**
     * @param credentialCharset The credentialCharset to set.
     */
    public void setCredentialCharset(String credentialCharset) {
        this.credentialCharset = credentialCharset;
    }

}