/*
 * $Id: PdfEncryption.java,v 1.53 2005/08/05 23:13:44 psoares33 Exp $
 * $Name:  $
 *
 * Copyright 2001, 2002 Paulo Soares
 *
 * The contents of this file are subject to the Mozilla Public License Version 1.1
 * (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the License.
 *
 * The Original Code is 'iText, a free JAVA-PDF library'.
 *
 * The Initial Developer of the Original Code is Bruno Lowagie. Portions created by
 * the Initial Developer are Copyright (C) 1999, 2000, 2001, 2002 by Bruno Lowagie.
 * All Rights Reserved.
 * Co-Developer of the code is Paulo Soares. Portions created by the Co-Developer
 * are Copyright (C) 2000, 2001, 2002 by Paulo Soares. All Rights Reserved.
 *
 * Contributor(s): all the names of the contributors are added in the source code
 * where applicable.
 *
 * Alternatively, the contents of this file may be used under the terms of the
 * LGPL license (the "GNU LIBRARY GENERAL PUBLIC LICENSE"), in which case the
 * provisions of LGPL are applicable instead of those above.  If you wish to
 * allow use of your version of this file only under the terms of the LGPL
 * License and not to allow others to use your version of this file under
 * the MPL, indicate your decision by deleting the provisions above and
 * replace them with the notice and other provisions required by the LGPL.
 * If you do not delete the provisions above, a recipient may use your version
 * of this file under either the MPL or the GNU LIBRARY GENERAL PUBLIC LICENSE.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the MPL as stated above or under the terms of the GNU
 * Library General Public License as published by the Free Software Foundation;
 * either version 2 of the License, or any later version.
 *
 * This library 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 Library general Public License for more
 * details.
 *
 * If you didn't download this code from the following link, you should check if
 * you aren't using an obsolete version:
 * http://www.lowagie.com/iText/
 */

package com.lowagie.text.pdf;

import java.security.MessageDigest;
import com.lowagie.text.ExceptionConverter;

/**
 *
 * @author  Paulo Soares (psoares@consiste.pt)
 * @author Kazuya Ujihara
 */
public class PdfEncryption {
    
    static final byte pad[] = {
        (byte)0x28, (byte)0xBF, (byte)0x4E, (byte)0x5E, (byte)0x4E, (byte)0x75,
        (byte)0x8A, (byte)0x41, (byte)0x64, (byte)0x00, (byte)0x4E, (byte)0x56,
        (byte)0xFF, (byte)0xFA, (byte)0x01, (byte)0x08, (byte)0x2E, (byte)0x2E,
        (byte)0x00, (byte)0xB6, (byte)0xD0, (byte)0x68, (byte)0x3E, (byte)0x80,
        (byte)0x2F, (byte)0x0C, (byte)0xA9, (byte)0xFE, (byte)0x64, (byte)0x53,
        (byte)0x69, (byte)0x7A};
        
    byte state[] = new byte[256];
    int x;
    int y;
    /** The encryption key for a particular object/generation */
    byte key[];
    /** The encryption key length for a particular object/generation */
    int keySize;
    /** The global encryption key */
    byte mkey[];
    /** Work area to prepare the object/generation bytes */
    byte extra[] = new byte[5];
    /** The message digest algorithm MD5 */
    MessageDigest md5;
    /** The encryption key for the owner */
    byte ownerKey[] = new byte[32];
    /** The encryption key for the user */
    byte userKey[] = new byte[32];
    int permissions;
    byte documentID[];
    static long seq = System.currentTimeMillis();

    public PdfEncryption() {
        try {
            md5 = MessageDigest.getInstance("MD5");
        }
        catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

    public PdfEncryption(PdfEncryption enc) {
        this();
        mkey = (byte[])enc.mkey.clone();
        ownerKey = (byte[])enc.ownerKey.clone();
        userKey = (byte[])enc.userKey.clone();
        permissions = enc.permissions;
        if (enc.documentID != null)
            documentID = (byte[])enc.documentID.clone();
    }
    
    /**
     */
    private byte[] padPassword(byte userPassword[]) {
        byte userPad[] = new byte[32];
        if (userPassword == null) {
            System.arraycopy(pad, 0, userPad, 0, 32);
        }
        else {
            System.arraycopy(userPassword, 0, userPad, 0, Math.min(userPassword.length, 32));
            if (userPassword.length < 32)
                System.arraycopy(pad, 0, userPad, userPassword.length, 32 - userPassword.length);
        }

        return userPad;
    }

    /**
     */
    private byte[] computeOwnerKey(byte userPad[], byte ownerPad[], boolean strength128Bits) {
        byte ownerKey[] = new byte[32];

        byte digest[] = md5.digest(ownerPad);
        if (strength128Bits) {
            byte mkey[] = new byte[16];
            for (int k = 0; k < 50; ++k)
                digest = md5.digest(digest);
            System.arraycopy(userPad, 0, ownerKey, 0, 32);
            for (int i = 0; i < 20; ++i) {
                for (int j = 0; j < mkey.length ; ++j)
                    mkey[j] = (byte)(digest[j] ^ i);
                prepareRC4Key(mkey);
                encryptRC4(ownerKey);
            }
        }
        else {
            prepareRC4Key(digest, 0, 5);
            encryptRC4(userPad, ownerKey);
        }

        return ownerKey;
    }

    /**
     *
     * ownerKey, documentID must be setuped
     */
    private void setupGlobalEncryptionKey(byte[] documentID, byte userPad[], byte ownerKey[], int permissions, boolean strength128Bits) {
        this.documentID = documentID;
        this.ownerKey = ownerKey;
        this.permissions = permissions;
        mkey = new byte[strength128Bits ? 16 : 5];

        //fixed by ujihara in order to follow PDF refrence
        md5.reset();
        md5.update(userPad);
        md5.update(ownerKey);

        byte ext[] = new byte[4];
        ext[0] = (byte)permissions;
        ext[1] = (byte)(permissions >> 8);
        ext[2] = (byte)(permissions >> 16);
        ext[3] = (byte)(permissions >> 24);
        md5.update(ext, 0, 4);
        if (documentID != null) md5.update(documentID);

        byte digest[] = md5.digest();

        if (mkey.length == 16) {
            for (int k = 0; k < 50; ++k)
                digest = md5.digest(digest);
        }

        System.arraycopy(digest, 0, mkey, 0, mkey.length);
    }

    /**
     *
     * mkey must be setuped
     */
    private void setupUserKey() {
        if (mkey.length == 16) {
            md5.update(pad);
            byte digest[] = md5.digest(documentID);
            System.arraycopy(digest, 0, userKey, 0, 16);
            for (int k = 16; k < 32; ++k)
                userKey[k] = 0;
            for (int i = 0; i < 20; ++i) {
                for (int j = 0; j < mkey.length; ++j)
                    digest[j] = (byte)(mkey[j] ^ i);
                prepareRC4Key(digest, 0, mkey.length);
                encryptRC4(userKey, 0, 16);
            }
        }
        else {
            prepareRC4Key(mkey);
            encryptRC4(pad, userKey);
        }
    }

    public void setupAllKeys(byte userPassword[], byte ownerPassword[], int permissions, boolean strength128Bits) {
        if (ownerPassword == null || ownerPassword.length == 0)
            ownerPassword = md5.digest(createDocumentId());
        permissions |= strength128Bits ? 0xfffff0c0 : 0xffffffc0;
        permissions &= 0xfffffffc;
        //PDF refrence 3.5.2 Standard Security Handler, Algorithum 3.3-1
        //If there is no owner password, use the user password instead.
        byte userPad[] = padPassword(userPassword);
        byte ownerPad[] = padPassword(ownerPassword);

        this.ownerKey = computeOwnerKey(userPad, ownerPad, strength128Bits);
        documentID = createDocumentId();
        setupByUserPad(this.documentID, userPad, this.ownerKey, permissions, strength128Bits);
    }

    public static byte[] createDocumentId() {
        MessageDigest md5;
        try {
            md5 = MessageDigest.getInstance("MD5");
        }
        catch (Exception e) {
             throw new ExceptionConverter(e);
       }
        long time = System.currentTimeMillis();
        long mem = Runtime.getRuntime().freeMemory();
        String s = time + "+" + mem + "+" + (seq++);
        return md5.digest(s.getBytes());
    }

    /**
     */
    public void setupByUserPassword(byte[] documentID, byte userPassword[], byte ownerKey[], int permissions, boolean strength128Bits) {
        setupByUserPad(documentID, padPassword(userPassword), ownerKey, permissions, strength128Bits);
    }

    /**
     */
    private void setupByUserPad(byte[] documentID, byte userPad[], byte ownerKey[], int permissions, boolean strength128Bits) {
        setupGlobalEncryptionKey(documentID, userPad, ownerKey, permissions, strength128Bits);
        setupUserKey();
    }

    /**
     */
    public void setupByOwnerPassword(byte[] documentID, byte ownerPassword[], byte userKey[], byte ownerKey[], int permissions, boolean strength128Bits) {
        setupByOwnerPad(documentID, padPassword(ownerPassword), userKey, ownerKey, permissions, strength128Bits);
    }

    private void setupByOwnerPad(byte[] documentID, byte ownerPad[], byte userKey[], byte ownerKey[], int permissions, boolean strength128Bits) {
        byte userPad[] = computeOwnerKey(ownerKey, ownerPad, strength128Bits);	//userPad will be set in this.ownerKey
        setupGlobalEncryptionKey(documentID, userPad, ownerKey, permissions, strength128Bits); //step 3
        setupUserKey();
    }

    public void prepareKey() {
        prepareRC4Key(key, 0, keySize);
    }

    public void setHashKey(int number, int generation) {
        md5.reset();	//added by ujihara
        extra[0] = (byte)number;
        extra[1] = (byte)(number >> 8);
        extra[2] = (byte)(number >> 16);
        extra[3] = (byte)generation;
        extra[4] = (byte)(generation >> 8);
        md5.update(mkey);
        key = md5.digest(extra);
        keySize = mkey.length + 5;
        if (keySize > 16)
            keySize = 16;
    }

    public static PdfObject createInfoId(byte id[]) {
        ByteBuffer buf = new ByteBuffer(90);
        buf.append('[').append('<');
        for (int k = 0; k < 16; ++k)
            buf.appendHex(id[k]);
        buf.append('>').append('<');
        id = createDocumentId();
        for (int k = 0; k < 16; ++k)
            buf.appendHex(id[k]);
        buf.append('>').append(']');
        return new PdfLiteral(buf.toByteArray());
    }

    public PdfDictionary getEncryptionDictionary() {
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.FILTER, PdfName.STANDARD);
        dic.put(PdfName.O, new PdfLiteral(PdfContentByte.escapeString(ownerKey)));
        dic.put(PdfName.U, new PdfLiteral(PdfContentByte.escapeString(userKey)));
        dic.put(PdfName.P, new PdfNumber(permissions));
        if (mkey.length > 5) {
            dic.put(PdfName.V, new PdfNumber(2));
            dic.put(PdfName.R, new PdfNumber(3));
            dic.put(PdfName.LENGTH, new PdfNumber(128));
        }
        else {
            dic.put(PdfName.V, new PdfNumber(1));
            dic.put(PdfName.R, new PdfNumber(2));
        }
        return dic;
    }

    public void prepareRC4Key(byte key[]) {
        prepareRC4Key(key, 0, key.length);
    }

    public void prepareRC4Key(byte key[], int off, int len) {
        int index1 = 0;
        int index2 = 0;
        for (int k = 0; k < 256; ++k)
            state[k] = (byte)k;
        x = 0;
        y = 0;
        byte tmp;
        for (int k = 0; k < 256; ++k) {
            index2 = (key[index1 + off] + state[k] + index2) & 255;
            tmp = state[k];
            state[k] = state[index2];
            state[index2] = tmp;
            index1 = (index1 + 1) % len;
        }
    }

    public void encryptRC4(byte dataIn[], int off, int len, byte dataOut[]) {
        int length = len + off;
        byte tmp;
        for (int k = off; k < length; ++k) {
            x = (x + 1) & 255;
            y = (state[x] + y) & 255;
            tmp = state[x];
            state[x] = state[y];
            state[y] = tmp;
            dataOut[k] = (byte)(dataIn[k] ^ state[(state[x] + state[y]) & 255]);
        }
    }

    public void encryptRC4(byte data[], int off, int len) {
        encryptRC4(data, off, len, data);
    }

    public void encryptRC4(byte dataIn[], byte dataOut[]) {
        encryptRC4(dataIn, 0, dataIn.length, dataOut);
    }

    public void encryptRC4(byte data[]) {
        encryptRC4(data, 0, data.length, data);
    }
    
    public PdfObject getFileID() {
        return createInfoId(documentID);
    }

}
