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	/*
	* Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code 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 General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package com.sun.crypto.provider;

	import java.security.InvalidKeyException;
	import java.security.ProviderException;
	import java.util.Objects;

	/**
	* This class represents ciphers in cipher block chaining (CBC) mode.
	*
	* <p>This mode is implemented independently of a particular cipher.
	* Ciphers to which this mode should apply (e.g., DES) must be
	* <i>plugged-in</i> using the constructor.
	*
	* <p>NOTE: This class does not deal with buffering or padding.
	*
	* @author Gigi Ankeny
	*/

	class CipherBlockChaining extends FeedbackCipher {

	/*
	* random bytes that are initialized with iv
	*/
	protected byte[] r;

	/*
	* output buffer
	*/
	private byte[] k;

	// variables for save/restore calls
	private byte[] rSave = null;

	CipherBlockChaining(SymmetricCipher embeddedCipher) {
	super(embeddedCipher);
	k = new byte[blockSize];
	r = new byte[blockSize];
	}

	/**
	* Gets the name of this feedback mode.
	*
	* @return the string <code>CBC</code>
	*/
	String getFeedback() {
	return "CBC";
	}

	/**
	* Initializes the cipher in the specified mode with the given key
	* and iv.
	*
	* @param decrypting flag indicating encryption or decryption
	* @param algorithm the algorithm name
	* @param key the key
	* @param iv the iv
	*
	* @exception InvalidKeyException if the given key is inappropriate for
	* initializing this cipher
	*/
	void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
	throws InvalidKeyException {
	if ((key == null) \|\| (iv == null) \|\| (iv.length != blockSize)) {
	throw new InvalidKeyException("Internal error");
	}
	this.iv = iv;
	reset();
	embeddedCipher.init(decrypting, algorithm, key);
	}

	/**
	* Resets the iv to its original value.
	* This is used when doFinal is called in the Cipher class, so that the
	* cipher can be reused (with its original iv).
	*/
	void reset() {
	System.arraycopy(iv, 0, r, 0, blockSize);
	}

	/**
	* Save the current content of this cipher.
	*/
	void save() {
	if (rSave == null) {
	rSave = new byte[blockSize];
	}
	System.arraycopy(r, 0, rSave, 0, blockSize);
	}

	/**
	* Restores the content of this cipher to the previous saved one.
	*/
	void restore() {
	System.arraycopy(rSave, 0, r, 0, blockSize);
	}

	/**
	* Performs encryption operation.
	*
	* <p>The input plain text <code>plain</code>, starting at
	* <code>plainOffset</code> and ending at
	* <code>(plainOffset + plainLen - 1)</code>, is encrypted.
	* The result is stored in <code>cipher</code>, starting at
	* <code>cipherOffset</code>.
	*
	* @param plain the buffer with the input data to be encrypted
	* @param plainOffset the offset in <code>plain</code>
	* @param plainLen the length of the input data
	* @param cipher the buffer for the result
	* @param cipherOffset the offset in <code>cipher</code>
	* @exception ProviderException if <code>len</code> is not
	* a multiple of the block size
	* @return the length of the encrypted data
	*/
	int encrypt(byte[] plain, int plainOffset, int plainLen,
	byte[] cipher, int cipherOffset) {
	if (plainLen <= 0) {
	return plainLen;
	}
	RangeUtil.blockSizeCheck(plainLen, blockSize);
	RangeUtil.nullAndBoundsCheck(plain, plainOffset, plainLen);
	RangeUtil.nullAndBoundsCheck(cipher, cipherOffset, plainLen);
	return implEncrypt(plain, plainOffset, plainLen,
	cipher, cipherOffset);
	}

	private int implEncrypt(byte[] plain, int plainOffset, int plainLen,
	byte[] cipher, int cipherOffset)
	{
	int endIndex = plainOffset + plainLen;

	for (; plainOffset < endIndex;
	plainOffset += blockSize, cipherOffset += blockSize) {
	for (int i = 0; i < blockSize; i++) {
	k[i] = (byte)(plain[i + plainOffset] ^ r[i]);
	}
	embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset);
	System.arraycopy(cipher, cipherOffset, r, 0, blockSize);
	}
	return plainLen;
	}

	/**
	* Performs decryption operation.
	*
	* <p>The input cipher text <code>cipher</code>, starting at
	* <code>cipherOffset</code> and ending at
	* <code>(cipherOffset + cipherLen - 1)</code>, is decrypted.
	* The result is stored in <code>plain</code>, starting at
	* <code>plainOffset</code>.
	*
	* <p>It is also the application's responsibility to make sure that
	* <code>init</code> has been called before this method is called.
	* (This check is omitted here, to avoid double checking.)
	*
	* @param cipher the buffer with the input data to be decrypted
	* @param cipherOffset the offset in <code>cipherOffset</code>
	* @param cipherLen the length of the input data
	* @param plain the buffer for the result
	* @param plainOffset the offset in <code>plain</code>
	* @exception ProviderException if <code>len</code> is not
	* a multiple of the block size
	* @return the length of the decrypted data
	*/
	int decrypt(byte[] cipher, int cipherOffset, int cipherLen,
	byte[] plain, int plainOffset) {
	if (cipherLen <= 0) {
	return cipherLen;
	}
	RangeUtil.blockSizeCheck(cipherLen, blockSize);
	RangeUtil.nullAndBoundsCheck(cipher, cipherOffset, cipherLen);
	RangeUtil.nullAndBoundsCheck(plain, plainOffset, cipherLen);
	return implDecrypt(cipher, cipherOffset, cipherLen, plain, plainOffset);
	}

	private int implDecrypt(byte[] cipher, int cipherOffset, int cipherLen,
	byte[] plain, int plainOffset)
	{
	int endIndex = cipherOffset + cipherLen;

	for (; cipherOffset < endIndex;
	cipherOffset += blockSize, plainOffset += blockSize) {
	embeddedCipher.decryptBlock(cipher, cipherOffset, k, 0);
	for (int i = 0; i < blockSize; i++) {
	plain[i + plainOffset] = (byte)(k[i] ^ r[i]);
	}
	System.arraycopy(cipher, cipherOffset, r, 0, blockSize);
	}
	return cipherLen;
	}
	}

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