pdfencryption.java

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/*
 * $Id: PdfEncryption.java 3538 2008-07-08 13:08:04Z blowagie $
 *
 * Copyright 2001-2006 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 com.lowagie.text.pdf.crypto.ARCFOUREncryption;

import java.io.IOException;
import java.io.OutputStream;
import java.io.ByteArrayOutputStream;
import java.security.MessageDigest;
import java.security.cert.Certificate;

import com.lowagie.text.ExceptionConverter;

/**
 * 
 * @author Paulo Soares ([e-mail])
 * @author Kazuya Ujihara
 */
public class PdfEncryption {

	public static final int STANDARD_ENCRYPTION_40 = 2;

	public static final int STANDARD_ENCRYPTION_128 = 3;

	public static final int AES_128 = 4;

	private 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 };

	private static final byte[] salt = { (byte) 0x73, (byte) 0x41, (byte) 0x6c,
			(byte) 0x54 };

	private static final byte[] metadataPad = { (byte) 255, (byte) 255,
			(byte) 255, (byte) 255 };

	/** 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];

	/** The public key security handler for certificate encryption */
	protected PdfPublicKeySecurityHandler publicKeyHandler = null;

	int permissions;

	byte documentID[];

	static long seq = System.currentTimeMillis();

	private int revision;

	private ARCFOUREncryption arcfour = new ARCFOUREncryption();

	/** The generic key length. It may be 40 or 128. */
	private int keyLength;

	private boolean encryptMetadata;
	
	/**
	 * Indicates if the encryption is only necessary for embedded files.
	 * @since 2.1.3
	 */
	private boolean embeddedFilesOnly;

	private int cryptoMode;

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

	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();
		revision = enc.revision;
		keyLength = enc.keyLength;
		encryptMetadata = enc.encryptMetadata;
		embeddedFilesOnly = enc.embeddedFilesOnly;
		publicKeyHandler = enc.publicKeyHandler;
	}

	public void setCryptoMode(int mode, int kl) {
		cryptoMode = mode;
		encryptMetadata = (mode & PdfWriter.DO_NOT_ENCRYPT_METADATA) == 0;
		embeddedFilesOnly = (mode & PdfWriter.EMBEDDED_FILES_ONLY) != 0;
		mode &= PdfWriter.ENCRYPTION_MASK;
		switch (mode) {
		case PdfWriter.STANDARD_ENCRYPTION_40:
			encryptMetadata = true;
			embeddedFilesOnly = false;
			keyLength = 40;
			revision = STANDARD_ENCRYPTION_40;
			break;
		case PdfWriter.STANDARD_ENCRYPTION_128:
			embeddedFilesOnly = false;
			if (kl > 0)
				keyLength = kl;
			else
				keyLength = 128;
			revision = STANDARD_ENCRYPTION_128;
			break;
		case PdfWriter.ENCRYPTION_AES_128:
			keyLength = 128;
			revision = AES_128;
			break;
		default:
			throw new IllegalArgumentException("No valid encryption mode");
		}
	}

	public int getCryptoMode() {
		return cryptoMode;
	}

	public boolean isMetadataEncrypted() {
		return encryptMetadata;
	}

	/**
	 * Indicates if only the embedded files have to be encrypted.
	 * @return	if true only the embedded files will be encrypted
	 * @since	2.1.3
	 */
	public boolean isEmbeddedFilesOnly() {
		return embeddedFilesOnly;
	}

	/**
	 */
	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[]) {
		byte ownerKey[] = new byte[32];

		byte digest[] = md5.digest(ownerPad);
		if (revision == STANDARD_ENCRYPTION_128 || revision == AES_128) {
			byte mkey[] = new byte[keyLength / 8];
			// only use for the input as many bit as the key consists of
			for (int k = 0; k < 50; ++k)
				System.arraycopy(md5.digest(digest), 0, digest, 0, mkey.length);
			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);
				arcfour.prepareARCFOURKey(mkey);
				arcfour.encryptARCFOUR(ownerKey);
			}
		} else {
			arcfour.prepareARCFOURKey(digest, 0, 5);
			arcfour.encryptARCFOUR(userPad, ownerKey);
		}

		return ownerKey;
	}

	/**
	 * 
	 * ownerKey, documentID must be setup
	 */
	private void setupGlobalEncryptionKey(byte[] documentID, byte userPad[],
			byte ownerKey[], int permissions) {
		this.documentID = documentID;
		this.ownerKey = ownerKey;
		this.permissions = permissions;
		// use variable keylength
		mkey = new byte[keyLength / 8];

		// fixed by ujihara in order to follow PDF reference
		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);
		if (!encryptMetadata)
			md5.update(metadataPad);

		byte digest[] = new byte[mkey.length];
		System.arraycopy(md5.digest(), 0, digest, 0, mkey.length);

		// only use the really needed bits as input for the hash
		if (revision == STANDARD_ENCRYPTION_128 || revision == AES_128) {
			for (int k = 0; k < 50; ++k)
				System.arraycopy(md5.digest(digest), 0, digest, 0, mkey.length);
		}

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

	/**
	 * 
	 * mkey must be setup
	 */
	// use the revision to choose the setup method
	private void setupUserKey() {
		if (revision == STANDARD_ENCRYPTION_128 || revision == AES_128) {
			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) {