001/*
002 * $Id: StandardDecryption.java 4784 2011-03-15 08:33:00Z blowagie $
003 *
004 * This file is part of the iText (R) project.
005 * Copyright (c) 1998-2011 1T3XT BVBA
006 * Authors: Bruno Lowagie, Paulo Soares, et al.
007 *
008 * This program is free software; you can redistribute it and/or modify
009 * it under the terms of the GNU Affero General Public License version 3
010 * as published by the Free Software Foundation with the addition of the
011 * following permission added to Section 15 as permitted in Section 7(a):
012 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY 1T3XT,
013 * 1T3XT DISCLAIMS THE WARRANTY OF NON INFRINGEMENT OF THIRD PARTY RIGHTS.
014 *
015 * This program is distributed in the hope that it will be useful, but
016 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
017 * or FITNESS FOR A PARTICULAR PURPOSE.
018 * See the GNU Affero General Public License for more details.
019 * You should have received a copy of the GNU Affero General Public License
020 * along with this program; if not, see http://www.gnu.org/licenses or write to
021 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
022 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
023 * http://itextpdf.com/terms-of-use/
024 *
025 * The interactive user interfaces in modified source and object code versions
026 * of this program must display Appropriate Legal Notices, as required under
027 * Section 5 of the GNU Affero General Public License.
028 *
029 * In accordance with Section 7(b) of the GNU Affero General Public License,
030 * a covered work must retain the producer line in every PDF that is created
031 * or manipulated using iText.
032 *
033 * You can be released from the requirements of the license by purchasing
034 * a commercial license. Buying such a license is mandatory as soon as you
035 * develop commercial activities involving the iText software without
036 * disclosing the source code of your own applications.
037 * These activities include: offering paid services to customers as an ASP,
038 * serving PDFs on the fly in a web application, shipping iText with a closed
039 * source product.
040 *
041 * For more information, please contact iText Software Corp. at this
042 * address: sales@itextpdf.com
043 */
044package com.itextpdf.text.pdf;
045
046import com.itextpdf.text.pdf.crypto.AESCipher;
047import com.itextpdf.text.pdf.crypto.ARCFOUREncryption;
048
049public class StandardDecryption {
050    protected ARCFOUREncryption arcfour;
051    protected AESCipher cipher;
052    private byte[] key;
053    private static final int AES_128 = 4;
054    private static final int AES_256 = 5;
055    private boolean aes;
056    private boolean initiated;
057    private byte[] iv = new byte[16];
058    private int ivptr;
059
060    /** Creates a new instance of StandardDecryption */
061    public StandardDecryption(byte key[], int off, int len, int revision) {
062        aes = (revision == AES_128 || revision == AES_256);
063        if (aes) {
064            this.key = new byte[len];
065            System.arraycopy(key, off, this.key, 0, len);
066        }
067        else {
068            arcfour = new ARCFOUREncryption();
069            arcfour.prepareARCFOURKey(key, off, len);
070        }
071    }
072    
073    public byte[] update(byte[] b, int off, int len) {
074        if (aes) {
075            if (initiated)
076                return cipher.update(b, off, len);
077            else {
078                int left = Math.min(iv.length - ivptr, len);
079                System.arraycopy(b, off, iv, ivptr, left);
080                off += left;
081                len -= left;
082                ivptr += left;
083                if (ivptr == iv.length) {
084                    cipher = new AESCipher(false, key, iv);
085                    initiated = true;
086                    if (len > 0)
087                        return cipher.update(b, off, len);
088                }
089                return null;
090            }
091        }
092        else {
093            byte[] b2 = new byte[len];
094            arcfour.encryptARCFOUR(b, off, len, b2, 0);
095            return b2;
096        }
097    }
098    
099    public byte[] finish() {
100        if (aes) {
101            return cipher.doFinal();
102        }
103        else
104            return null;
105    }
106}