de.intarsys.pdf.crypt.StandardSecurityHandlerR4 Maven / Gradle / Ivy

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/*
 * Copyright (c) 2007, intarsys consulting GmbH
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * - Neither the name of intarsys nor the names of its contributors may be used
 *   to endorse or promote products derived from this software without specific
 *   prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package de.intarsys.pdf.crypt;

import java.security.MessageDigest;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import de.intarsys.pdf.cos.COSName;

/**
 * The {@link ISecurityHandler} implementing /R 4 of the PDF spec.
 * 
 */
public class StandardSecurityHandlerR4 extends StandardSecurityHandler {
	public static final String KEY_ALGORITHM = "RC4"; //$NON-NLS-1$

	public static final String CIPHER_ALGORITHM = "RC4"; //$NON-NLS-1$

	public static final String DIGEST_ALGORITHM = "MD5"; //$NON-NLS-1$

	public static final COSName DK_AuthEvent = COSName.constant("AuthEvent"); //$NON-NLS-1$

	/** A byte sequence to be include in the hash under certain circumstances. */
	private static byte[] HIGH_BYTES = new byte[] { (byte) 0xFF, (byte) 0xFF,
			(byte) 0xFF, (byte) 0xFF };

	public StandardSecurityHandlerR4() {
		super();
	}

	@Override
	public boolean authenticateOwner(byte[] owner) throws COSSecurityException {
		try {
			byte[] preparedOwner = prepareBytes(owner);
			MessageDigest md = MessageDigest.getInstance(DIGEST_ALGORITHM);
			md.update(preparedOwner);
			byte[] key = md.digest();
			for (int i = 0; i < 50; i++) {
				md.update(key);
				key = md.digest();
			}
			// this is not sufficiently specified in the PDF spec
			// int length = getEncryption().getLength() / 8;
			int length = 16;
			byte[] encryptionKey = new byte[length];
			System.arraycopy(key, 0, encryptionKey, 0, length);
			//
			Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
			if (cipher == null) {
				throw new COSSecurityException("RC4 cipher not found"); //$NON-NLS-1$
			}
			SecretKey skeySpec;
			byte[] encrypted = getO();
			byte[] tempEncKey = new byte[encryptionKey.length];
			for (int i = 19; i >= 0; i--) {
				for (int index = 0; index < encryptionKey.length; index++) {
					tempEncKey[index] = (byte) (encryptionKey[index] ^ i);
				}
				skeySpec = new SecretKeySpec(tempEncKey, KEY_ALGORITHM);
				cipher.init(Cipher.DECRYPT_MODE, skeySpec);
				encrypted = cipher.doFinal(encrypted);
			}
			if (authenticateUser(encrypted)) {
				setActiveAccessPermissions(AccessPermissionsFull.get());
				return true;
			}
			return false;
		} catch (Exception e) {
			throw new COSSecurityException(e);
		}
	}

	@Override
	public boolean authenticateUser(byte[] user) throws COSSecurityException {
		byte[] entryU = getU();
		byte[] tempU = createUserPassword(user);
		if (entryU.length != tempU.length) {
			return false;
		}
		int length = 16;
		for (int i = 0; i < length; i++) {
			if (entryU[i] != tempU[i]) {
				return false;
			}
		}
		// if user is correctly authenticated, this key can be used for
		// decryption
		setCryptKey(createCryptKey(user));
		setActiveAccessPermissions(createAccessPermissions());
		return true;
	}

	@Override
	protected IAccessPermissions createAccessPermissions() {
		return new AccessPermissionsR3(getPermissionFlags());
	}

	@Override
	protected byte[] createCryptKey(byte[] password)
			throws COSSecurityException {
		try {
			MessageDigest md = MessageDigest.getInstance(DIGEST_ALGORITHM);
			byte[] prepared = prepareBytes(password);
			md.update(prepared);
			md.update(getO());
			md.update(getPBytes());
			byte[] fd = getPermanentFileID();
			if (fd != null) {
				md.update(fd);
			}
			if (!isEncryptMetadata()) {
				md.update(HIGH_BYTES);
			}
			byte[] key = md.digest();
			// this is not sufficiently specified in the PDF spec
			// int length = getEncryption().getLength() / 8;
			int length = 16;
			for (int i = 0; i < 50; i++) {
				md.update(key, 0, length);
				key = md.digest();
			}
			byte[] result = new byte[length];
			System.arraycopy(key, 0, result, 0, length);
			return result;
		} catch (Exception e) {
			throw new COSSecurityException(e);
		}
	}

	@Override
	protected byte[] createOwnerPassword(byte[] owner, byte[] user)
			throws COSSecurityException {
		try {
			byte[] preparedOwner;
			if (owner == null) {
				preparedOwner = prepareBytes(user);
			} else {
				preparedOwner = prepareBytes(owner);
			}
			MessageDigest md = MessageDigest.getInstance(DIGEST_ALGORITHM);
			md.update(preparedOwner);
			byte[] key = md.digest();
			// this is not sufficiently specified in the PDF spec
			// int length = getEncryption().getLength() / 8;
			int length = 16;
			for (int i = 0; i < 50; i++) {
				md.update(key, 0, length);
				key = md.digest();
			}
			byte[] encryptionKey = new byte[length];
			System.arraycopy(key, 0, encryptionKey, 0, length);
			//
			SecretKey skeySpec = new SecretKeySpec(encryptionKey, KEY_ALGORITHM);
			byte[] preparedUser = prepareBytes(user);
			Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
			cipher.init(Cipher.DECRYPT_MODE, skeySpec);
			byte[] encrypted = cipher.doFinal(preparedUser);

			byte[] tempKey = new byte[encryptionKey.length];
			for (int i = 1; i <= 19; i++) {
				for (int index = 0; index < encryptionKey.length; index++) {
					tempKey[index] = (byte) (encryptionKey[index] ^ i);
				}
				skeySpec = new SecretKeySpec(tempKey, KEY_ALGORITHM);
				cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
				encrypted = cipher.doFinal(encrypted);
			}
			return encrypted;
		} catch (Exception e) {
			throw new COSSecurityException(e);
		}
	}

	@Override
	protected byte[] createUserPassword(byte[] user)
			throws COSSecurityException {
		try {
			byte[] encryptionKey = createCryptKey(user);
			MessageDigest md = MessageDigest.getInstance(DIGEST_ALGORITHM);
			md.update(PADDING);
			byte[] fd = getPermanentFileID();
			if (fd != null) {
				md.update(fd);
			}
			byte[] hash = md.digest();
			SecretKey skeySpec = new SecretKeySpec(encryptionKey, KEY_ALGORITHM);
			Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
			cipher.init(Cipher.DECRYPT_MODE, skeySpec);
			byte[] encrypted = cipher.doFinal(hash);
			byte[] tempEncKey = new byte[encryptionKey.length];
			for (int i = 1; i <= 19; i++) {
				for (int index = 0; index < encryptionKey.length; index++) {
					tempEncKey[index] = (byte) (encryptionKey[index] ^ i);
				}
				skeySpec = new SecretKeySpec(tempEncKey, KEY_ALGORITHM);
				cipher.init(Cipher.DECRYPT_MODE, skeySpec);
				encrypted = cipher.doFinal(encrypted);
			}
			byte[] result = new byte[32];
			System.arraycopy(encrypted, 0, result, 0, 16);
			System.arraycopy(USER_R3_PADDING, 0, result, 16, 16);
			return result;
		} catch (Exception e) {
			throw new COSSecurityException(e);
		}
	}

	@Override
	public int getRevision() {
		return 4;
	}
}