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	/*
	* Copyright (c) 2013, 2017, 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.util.Arrays;
	import java.io.*;
	import java.security.*;
	import javax.crypto.*;
	import static com.sun.crypto.provider.AESConstants.AES_BLOCK_SIZE;

	/**
	* This class represents ciphers in GaloisCounter (GCM) mode.
	*
	* <p>This mode currently should only be used w/ AES cipher.
	* Although no checking is done, caller should only pass AES
	* Cipher to the constructor.
	*
	* <p>NOTE: Unlike other modes, when used for decryption, this class
	* will buffer all processed outputs internally and won't return them
	* until the tag has been successfully verified.
	*
	* @since 1.8
	*/
	final class GaloisCounterMode extends FeedbackCipher {

	static int DEFAULT_TAG_LEN = AES_BLOCK_SIZE;
	static int DEFAULT_IV_LEN = 12; // in bytes

	// In NIST SP 800-38D, GCM input size is limited to be no longer
	// than (2^36 - 32) bytes. Otherwise, the counter will wrap
	// around and lead to a leak of plaintext.
	// However, given the current GCM spec requirement that recovered
	// text can only be returned after successful tag verification,
	// we are bound by limiting the data size to the size limit of
	// java byte array, e.g. Integer.MAX_VALUE, since all data
	// can only be returned by the doFinal(...) call.
	private static final int MAX_BUF_SIZE = Integer.MAX_VALUE;

	// buffer for AAD data; if null, meaning update has been called
	private ByteArrayOutputStream aadBuffer = new ByteArrayOutputStream();
	private int sizeOfAAD = 0;

	// buffer for storing input in decryption, not used for encryption
	private ByteArrayOutputStream ibuffer = null;

	// in bytes; need to convert to bits (default value 128) when needed
	private int tagLenBytes = DEFAULT_TAG_LEN;

	// these following 2 fields can only be initialized after init() is
	// called, e.g. after cipher key k is set, and STAY UNCHANGED
	private byte[] subkeyH = null;
	private byte[] preCounterBlock = null;

	private GCTR gctrPAndC = null;
	private GHASH ghashAllToS = null;

	// length of total data, i.e. len(C)
	private int processed = 0;

	// additional variables for save/restore calls
	private byte[] aadBufferSave = null;
	private int sizeOfAADSave = 0;
	private byte[] ibufferSave = null;
	private int processedSave = 0;

	// value must be 16-byte long; used by GCTR and GHASH as well
	static void increment32(byte[] value) {
	if (value.length != AES_BLOCK_SIZE) {
	// should never happen
	throw new ProviderException("Illegal counter block length");
	}
	// start from last byte and only go over 4 bytes, i.e. total 32 bits
	int n = value.length - 1;
	while ((n >= value.length - 4) && (++value[n] == 0)) {
	n--;
	}
	}

	private static byte[] getLengthBlock(int ivLenInBytes) {
	long ivLen = ((long)ivLenInBytes) << 3;
	byte[] out = new byte[AES_BLOCK_SIZE];
	out[8] = (byte)(ivLen >>> 56);
	out[9] = (byte)(ivLen >>> 48);
	out[10] = (byte)(ivLen >>> 40);
	out[11] = (byte)(ivLen >>> 32);
	out[12] = (byte)(ivLen >>> 24);
	out[13] = (byte)(ivLen >>> 16);
	out[14] = (byte)(ivLen >>> 8);
	out[15] = (byte)ivLen;
	return out;
	}

	private static byte[] getLengthBlock(int aLenInBytes, int cLenInBytes) {
	long aLen = ((long)aLenInBytes) << 3;
	long cLen = ((long)cLenInBytes) << 3;
	byte[] out = new byte[AES_BLOCK_SIZE];
	out[0] = (byte)(aLen >>> 56);
	out[1] = (byte)(aLen >>> 48);
	out[2] = (byte)(aLen >>> 40);
	out[3] = (byte)(aLen >>> 32);
	out[4] = (byte)(aLen >>> 24);
	out[5] = (byte)(aLen >>> 16);
	out[6] = (byte)(aLen >>> 8);
	out[7] = (byte)aLen;
	out[8] = (byte)(cLen >>> 56);
	out[9] = (byte)(cLen >>> 48);
	out[10] = (byte)(cLen >>> 40);
	out[11] = (byte)(cLen >>> 32);
	out[12] = (byte)(cLen >>> 24);
	out[13] = (byte)(cLen >>> 16);
	out[14] = (byte)(cLen >>> 8);
	out[15] = (byte)cLen;
	return out;
	}

	private static byte[] expandToOneBlock(byte[] in, int inOfs, int len) {
	if (len > AES_BLOCK_SIZE) {
	throw new ProviderException("input " + len + " too long");
	}
	if (len == AES_BLOCK_SIZE && inOfs == 0) {
	return in;
	} else {
	byte[] paddedIn = new byte[AES_BLOCK_SIZE];
	System.arraycopy(in, inOfs, paddedIn, 0, len);
	return paddedIn;
	}
	}

	private static byte[] getJ0(byte[] iv, byte[] subkeyH) {
	byte[] j0;
	if (iv.length == 12) { // 96 bits
	j0 = expandToOneBlock(iv, 0, iv.length);
	j0[AES_BLOCK_SIZE - 1] = 1;
	} else {
	GHASH g = new GHASH(subkeyH);
	int lastLen = iv.length % AES_BLOCK_SIZE;
	if (lastLen != 0) {
	g.update(iv, 0, iv.length - lastLen);
	byte[] padded =
	expandToOneBlock(iv, iv.length - lastLen, lastLen);
	g.update(padded);
	} else {
	g.update(iv);
	}
	byte[] lengthBlock = getLengthBlock(iv.length);
	g.update(lengthBlock);
	j0 = g.digest();
	}
	return j0;
	}

	private static void checkDataLength(int processed, int len) {
	if (processed > MAX_BUF_SIZE - len) {
	throw new ProviderException("SunJCE provider only supports " +
	"input size up to " + MAX_BUF_SIZE + " bytes");
	}
	}

	GaloisCounterMode(SymmetricCipher embeddedCipher) {
	super(embeddedCipher);
	aadBuffer = new ByteArrayOutputStream();
	}

	/**
	* Gets the name of the feedback mechanism
	*
	* @return the name of the feedback mechanism
	*/
	String getFeedback() {
	return "GCM";
	}

	/**
	* Resets the cipher object to its original state.
	* This is used when doFinal is called in the Cipher class, so that the
	* cipher can be reused (with its original key and iv).
	*/
	void reset() {
	if (aadBuffer == null) {
	aadBuffer = new ByteArrayOutputStream();
	} else {
	aadBuffer.reset();
	}
	if (gctrPAndC != null) gctrPAndC.reset();
	if (ghashAllToS != null) ghashAllToS.reset();
	processed = 0;
	sizeOfAAD = 0;
	if (ibuffer != null) {
	ibuffer.reset();
	}
	}

	/**
	* Save the current content of this cipher.
	*/
	void save() {
	processedSave = processed;
	sizeOfAADSave = sizeOfAAD;
	aadBufferSave =
	((aadBuffer == null \|\| aadBuffer.size() == 0)?
	null : aadBuffer.toByteArray());
	if (gctrPAndC != null) gctrPAndC.save();
	if (ghashAllToS != null) ghashAllToS.save();
	if (ibuffer != null) {
	ibufferSave = ibuffer.toByteArray();
	}
	}

	/**
	* Restores the content of this cipher to the previous saved one.
	*/
	void restore() {
	processed = processedSave;
	sizeOfAAD = sizeOfAADSave;
	if (aadBuffer != null) {
	aadBuffer.reset();
	if (aadBufferSave != null) {
	aadBuffer.write(aadBufferSave, 0, aadBufferSave.length);
	}
	}
	if (gctrPAndC != null) gctrPAndC.restore();
	if (ghashAllToS != null) ghashAllToS.restore();
	if (ibuffer != null) {
	ibuffer.reset();
	ibuffer.write(ibufferSave, 0, ibufferSave.length);
	}
	}

	/**
	* 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
	* @param tagLenBytes the length of tag in bytes
	*
	* @exception InvalidKeyException if the given key is inappropriate for
	* initializing this cipher
	*/
	@Override
	void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
	throws InvalidKeyException, InvalidAlgorithmParameterException {
	init(decrypting, algorithm, key, iv, DEFAULT_TAG_LEN);
	}

	/**
	* 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
	* @param tagLenBytes the length of tag in bytes
	*
	* @exception InvalidKeyException if the given key is inappropriate for
	* initializing this cipher
	*/
	void init(boolean decrypting, String algorithm, byte[] keyValue,
	byte[] ivValue, int tagLenBytes)
	throws InvalidKeyException, InvalidAlgorithmParameterException {
	if (keyValue == null) {
	throw new InvalidKeyException("Internal error");
	}
	if (ivValue == null) {
	throw new InvalidAlgorithmParameterException("Internal error");
	}
	if (ivValue.length == 0) {
	throw new InvalidAlgorithmParameterException("IV is empty");
	}

	// always encrypt mode for embedded cipher
	this.embeddedCipher.init(false, algorithm, keyValue);
	this.subkeyH = new byte[AES_BLOCK_SIZE];
	this.embeddedCipher.encryptBlock(new byte[AES_BLOCK_SIZE], 0,
	this.subkeyH, 0);

	this.iv = ivValue.clone();
	preCounterBlock = getJ0(iv, subkeyH);
	byte[] j0Plus1 = preCounterBlock.clone();
	increment32(j0Plus1);
	gctrPAndC = new GCTR(embeddedCipher, j0Plus1);
	ghashAllToS = new GHASH(subkeyH);

	this.tagLenBytes = tagLenBytes;
	if (aadBuffer == null) {
	aadBuffer = new ByteArrayOutputStream();
	} else {
	aadBuffer.reset();
	}
	processed = 0;
	sizeOfAAD = 0;
	if (decrypting) {
	ibuffer = new ByteArrayOutputStream();
	}
	}

	/**
	* Continues a multi-part update of the Additional Authentication
	* Data (AAD), using a subset of the provided buffer. If this
	* cipher is operating in either GCM or CCM mode, all AAD must be
	* supplied before beginning operations on the ciphertext (via the
	* {@code update} and {@code doFinal} methods).
	* <p>
	* NOTE: Given most modes do not accept AAD, default impl for this
	* method throws IllegalStateException.
	*
	* @param src the buffer containing the AAD
	* @param offset the offset in {@code src} where the AAD input starts
	* @param len the number of AAD bytes
	*
	* @throws IllegalStateException if this cipher is in a wrong state
	* (e.g., has not been initialized), does not accept AAD, or if
	* operating in either GCM or CCM mode and one of the {@code update}
	* methods has already been called for the active
	* encryption/decryption operation
	* @throws UnsupportedOperationException if this method
	* has not been overridden by an implementation
	*
	* @since 1.8
	*/
	void updateAAD(byte[] src, int offset, int len) {
	if (aadBuffer != null) {
	aadBuffer.write(src, offset, len);
	} else {
	// update has already been called
	throw new IllegalStateException
	("Update has been called; no more AAD data");
	}
	}

	// Feed the AAD data to GHASH, pad if necessary
	void processAAD() {
	if (aadBuffer != null) {
	if (aadBuffer.size() > 0) {
	byte[] aad = aadBuffer.toByteArray();
	sizeOfAAD = aad.length;

	int lastLen = aad.length % AES_BLOCK_SIZE;
	if (lastLen != 0) {
	ghashAllToS.update(aad, 0, aad.length - lastLen);
	byte[] padded = expandToOneBlock(aad, aad.length - lastLen,
	lastLen);
	ghashAllToS.update(padded);
	} else {
	ghashAllToS.update(aad);
	}
	}
	aadBuffer = null;
	}
	}

	// Utility to process the last block; used by encryptFinal and decryptFinal
	void doLastBlock(byte[] in, int inOfs, int len, byte[] out, int outOfs,
	boolean isEncrypt) throws IllegalBlockSizeException {
	// process data in 'in'
	gctrPAndC.doFinal(in, inOfs, len, out, outOfs);
	processed += len;

	byte[] ct;
	int ctOfs;
	if (isEncrypt) {
	ct = out;
	ctOfs = outOfs;
	} else {
	ct = in;
	ctOfs = inOfs;
	}
	int lastLen = len % AES_BLOCK_SIZE;
	if (lastLen != 0) {
	ghashAllToS.update(ct, ctOfs, len - lastLen);
	byte[] padded =
	expandToOneBlock(ct, (ctOfs + len - lastLen), lastLen);
	ghashAllToS.update(padded);
	} else {
	ghashAllToS.update(ct, ctOfs, len);
	}
	}


	/**
	* Performs encryption operation.
	*
	* <p>The input plain text <code>in</code>, starting at <code>inOff</code>
	* and ending at <code>(inOff + len - 1)</code>, is encrypted. The result
	* is stored in <code>out</code>, starting at <code>outOfs</code>.
	*
	* @param in the buffer with the input data to be encrypted
	* @param inOfs the offset in <code>in</code>
	* @param len the length of the input data
	* @param out the buffer for the result
	* @param outOfs the offset in <code>out</code>
	* @exception ProviderException if <code>len</code> is not
	* a multiple of the block size
	* @return the number of bytes placed into the <code>out</code> buffer
	*/
	int encrypt(byte[] in, int inOfs, int len, byte[] out, int outOfs) {
	if ((len % blockSize) != 0) {
	throw new ProviderException("Internal error in input buffering");
	}

	checkDataLength(processed, len);

	processAAD();
	if (len > 0) {
	gctrPAndC.update(in, inOfs, len, out, outOfs);
	processed += len;
	ghashAllToS.update(out, outOfs, len);
	}
	return len;
	}

	/**
	* Performs encryption operation for the last time.
	*
	* @param in the input buffer with the data to be encrypted
	* @param inOfs the offset in <code>in</code>
	* @param len the length of the input data
	* @param out the buffer for the encryption result
	* @param outOfs the offset in <code>out</code>
	* @return the number of bytes placed into the <code>out</code> buffer
	*/
	int encryptFinal(byte[] in, int inOfs, int len, byte[] out, int outOfs)
	throws IllegalBlockSizeException, ShortBufferException {
	if (len > MAX_BUF_SIZE - tagLenBytes) {
	throw new ShortBufferException
	("Can't fit both data and tag into one buffer");
	}
	if (out.length - outOfs < (len + tagLenBytes)) {
	throw new ShortBufferException("Output buffer too small");
	}

	checkDataLength(processed, len);

	processAAD();
	if (len > 0) {
	doLastBlock(in, inOfs, len, out, outOfs, true);
	}

	byte[] lengthBlock =
	getLengthBlock(sizeOfAAD, processed);
	ghashAllToS.update(lengthBlock);
	byte[] s = ghashAllToS.digest();
	byte[] sOut = new byte[s.length];
	GCTR gctrForSToTag = new GCTR(embeddedCipher, this.preCounterBlock);
	gctrForSToTag.doFinal(s, 0, s.length, sOut, 0);

	System.arraycopy(sOut, 0, out, (outOfs + len), tagLenBytes);
	return (len + tagLenBytes);
	}

	/**
	* Performs decryption operation.
	*
	* <p>The input cipher text <code>in</code>, starting at
	* <code>inOfs</code> and ending at <code>(inOfs + len - 1)</code>,
	* is decrypted. The result is stored in <code>out</code>, starting at
	* <code>outOfs</code>.
	*
	* @param in the buffer with the input data to be decrypted
	* @param inOfs the offset in <code>in</code>
	* @param len the length of the input data
	* @param out the buffer for the result
	* @param outOfs the offset in <code>out</code>
	* @exception ProviderException if <code>len</code> is not
	* a multiple of the block size
	* @return the number of bytes placed into the <code>out</code> buffer
	*/
	int decrypt(byte[] in, int inOfs, int len, byte[] out, int outOfs) {
	if ((len % blockSize) != 0) {
	throw new ProviderException("Internal error in input buffering");
	}

	checkDataLength(ibuffer.size(), len);

	processAAD();

	if (len > 0) {
	// store internally until decryptFinal is called because
	// spec mentioned that only return recovered data after tag
	// is successfully verified
	ibuffer.write(in, inOfs, len);
	}
	return 0;
	}

	/**
	* Performs decryption operation for the last time.
	*
	* <p>NOTE: For cipher feedback modes which does not perform
	* special handling for the last few blocks, this is essentially
	* the same as <code>encrypt(...)</code>. Given most modes do
	* not do special handling, the default impl for this method is
	* to simply call <code>decrypt(...)</code>.
	*
	* @param in the input buffer with the data to be decrypted
	* @param inOfs the offset in <code>cipher</code>
	* @param len the length of the input data
	* @param out the buffer for the decryption result
	* @param outOfs the offset in <code>plain</code>
	* @return the number of bytes placed into the <code>out</code> buffer
	*/
	int decryptFinal(byte[] in, int inOfs, int len,
	byte[] out, int outOfs)
	throws IllegalBlockSizeException, AEADBadTagException,
	ShortBufferException {
	if (len < tagLenBytes) {
	throw new AEADBadTagException("Input too short - need tag");
	}
	// do this check here can also catch the potential integer overflow
	// scenario for the subsequent output buffer capacity check.
	checkDataLength(ibuffer.size(), (len - tagLenBytes));

	if (out.length - outOfs < ((ibuffer.size() + len) - tagLenBytes)) {
	throw new ShortBufferException("Output buffer too small");
	}

	processAAD();

	// get the trailing tag bytes from 'in'
	byte[] tag = new byte[tagLenBytes];
	System.arraycopy(in, inOfs + len - tagLenBytes, tag, 0, tagLenBytes);
	len -= tagLenBytes;

	if (len != 0) {
	ibuffer.write(in, inOfs, len);
	}

	// refresh 'in' to all buffered-up bytes
	in = ibuffer.toByteArray();
	inOfs = 0;
	len = in.length;
	ibuffer.reset();

	if (len > 0) {
	doLastBlock(in, inOfs, len, out, outOfs, false);
	}

	byte[] lengthBlock =
	getLengthBlock(sizeOfAAD, processed);
	ghashAllToS.update(lengthBlock);

	byte[] s = ghashAllToS.digest();
	byte[] sOut = new byte[s.length];
	GCTR gctrForSToTag = new GCTR(embeddedCipher, this.preCounterBlock);
	gctrForSToTag.doFinal(s, 0, s.length, sOut, 0);

	// check entire authentication tag for time-consistency
	int mismatch = 0;
	for (int i = 0; i < tagLenBytes; i++) {
	mismatch \|= tag[i] ^ sOut[i];
	}

	if (mismatch != 0) {
	throw new AEADBadTagException("Tag mismatch!");
	}

	return len;
	}

	// return tag length in bytes
	int getTagLen() {
	return this.tagLenBytes;
	}

	int getBufferedLength() {
	if (ibuffer == null) {
	return 0;
	} else {
	return ibuffer.size();
	}
	}
	}

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