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/*
* Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2015 Red Hat, Inc.
* 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.
*/
/*
* (C) Copyright IBM Corp. 2013
*/
package com.sun.crypto.provider;
import java.security.ProviderException;
/**
* This class represents the GHASH function defined in NIST 800-38D
* under section 6.4. It needs to be constructed w/ a hash subkey, i.e.
* block H. Given input of 128-bit blocks, it will process and output
* a 128-bit block.
*
* <p>This function is used in the implementation of GCM mode.
*
* @since 1.8
*/
final class GHASH {
private static long getLong(byte[] buffer, int offset) {
long result = 0;
int end = offset + 8;
for (int i = offset; i < end; ++i) {
result = (result << 8) + (buffer[i] & 0xFF);
}
return result;
}
private static void putLong(byte[] buffer, int offset, long value) {
int end = offset + 8;
for (int i = end - 1; i >= offset; --i) {
buffer[i] = (byte) value;
value >>= 8;
}
}
private static final int AES_BLOCK_SIZE = 16;
// Multiplies state0, state1 by V0, V1.
private void blockMult(long V0, long V1) {
long Z0 = 0;
long Z1 = 0;
long X;
// Separate loops for processing state0 and state1.
X = state0;
for (int i = 0; i < 64; i++) {
// Zi+1 = Zi if bit i of x is 0
long mask = X >> 63;
Z0 ^= V0 & mask;
Z1 ^= V1 & mask;
// Save mask for conditional reduction below.
mask = (V1 << 63) >> 63;
// V = rightshift(V)
long carry = V0 & 1;
V0 = V0 >>> 1;
V1 = (V1 >>> 1) | (carry << 63);
// Conditional reduction modulo P128.
V0 ^= 0xe100000000000000L & mask;
X <<= 1;
}
X = state1;
for (int i = 64; i < 127; i++) {
// Zi+1 = Zi if bit i of x is 0
long mask = X >> 63;
Z0 ^= V0 & mask;
Z1 ^= V1 & mask;
// Save mask for conditional reduction below.
mask = (V1 << 63) >> 63;
// V = rightshift(V)
long carry = V0 & 1;
V0 = V0 >>> 1;
V1 = (V1 >>> 1) | (carry << 63);
// Conditional reduction.
V0 ^= 0xe100000000000000L & mask;
X <<= 1;
}
// calculate Z128
long mask = X >> 63;
Z0 ^= V0 & mask;
Z1 ^= V1 & mask;
// Save result.
state0 = Z0;
state1 = Z1;
}
// hash subkey H; should not change after the object has been constructed
private final long subkeyH0, subkeyH1;
// buffer for storing hash
private long state0, state1;
// variables for save/restore calls
private long stateSave0, stateSave1;
/**
* Initializes the cipher in the specified mode with the given key
* and iv.
*
* @param subkeyH the hash subkey
*
* @exception ProviderException if the given key is inappropriate for
* initializing this digest
*/
GHASH(byte[] subkeyH) throws ProviderException {
if ((subkeyH == null) || subkeyH.length != AES_BLOCK_SIZE) {
throw new ProviderException("Internal error");
}
this.subkeyH0 = getLong(subkeyH, 0);
this.subkeyH1 = getLong(subkeyH, 8);
}
/**
* Resets the GHASH object to its original state, i.e. blank w/
* the same subkey H. Used after digest() is called and to re-use
* this object for different data w/ the same H.
*/
void reset() {
state0 = 0;
state1 = 0;
}
/**
* Save the current snapshot of this GHASH object.
*/
void save() {
stateSave0 = state0;
stateSave1 = state1;
}
/**
* Restores this object using the saved snapshot.
*/
void restore() {
state0 = stateSave0;
state1 = stateSave1;
}
private void processBlock(byte[] data, int ofs) {
if (data.length - ofs < AES_BLOCK_SIZE) {
throw new RuntimeException("need complete block");
}
state0 ^= getLong(data, ofs);
state1 ^= getLong(data, ofs + 8);
blockMult(subkeyH0, subkeyH1);
}
void update(byte[] in) {
update(in, 0, in.length);
}
void update(byte[] in, int inOfs, int inLen) {
if (inLen - inOfs > in.length) {
throw new RuntimeException("input length out of bound");
}
if (inLen % AES_BLOCK_SIZE != 0) {
throw new RuntimeException("input length unsupported");
}
for (int i = inOfs; i < (inOfs + inLen); i += AES_BLOCK_SIZE) {
processBlock(in, i);
}
}
byte[] digest() {
byte[] result = new byte[AES_BLOCK_SIZE];
putLong(result, 0, state0);
putLong(result, 8, state1);
reset();
return result;
}
}
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