1 /*
2 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 /*
26 * (C) Copyright IBM Corp. 2013
27 */
28
29 package com.sun.crypto.provider;
30
31 import java.util.Arrays;
32 import java.security.*;
33 import static com.sun.crypto.provider.AESConstants.AES_BLOCK_SIZE;
34
35 /**
36 * This class represents the GHASH function defined in NIST 800-38D
37 * under section 6.4. It needs to be constructed w/ a hash subkey, i.e.
38 * block H. Given input of 128-bit blocks, it will process and output
39 * a 128-bit block.
40 *
41 * <p>This function is used in the implementation of GCM mode.
42 *
43 * @since 1.8
44 */
45 final class GHASH {
46
47 private static final byte P128 = (byte) 0xe1; //reduction polynomial
48
49 private static boolean getBit(byte[] b, int pos) {
50 int p = pos / 8;
51 pos %= 8;
52 int i = (b[p] >>> (7 - pos)) & 1;
53 return i != 0;
54 }
55
56 private static void shift(byte[] b) {
57 byte temp, temp2;
58 temp2 = 0;
59 for (int i = 0; i < b.length; i++) {
60 temp = (byte) ((b[i] & 0x01) << 7);
61 b[i] = (byte) ((b[i] & 0xff) >>> 1);
62 b[i] = (byte) (b[i] | temp2);
63 temp2 = temp;
64 }
65 }
66
67 // Given block X and Y, returns the muliplication of X * Y
68 private static byte[] blockMult(byte[] x, byte[] y) {
69 if (x.length != AES_BLOCK_SIZE || y.length != AES_BLOCK_SIZE) {
70 throw new RuntimeException("illegal input sizes");
71 }
72 byte[] z = new byte[AES_BLOCK_SIZE];
73 byte[] v = y.clone();
74 // calculate Z1-Z127 and V1-V127
75 for (int i = 0; i < 127; i++) {
76 // Zi+1 = Zi if bit i of x is 0
77 if (getBit(x, i)) {
78 for (int n = 0; n < z.length; n++) {
79 z[n] ^= v[n];
80 }
81 }
82 boolean lastBitOfV = getBit(v, 127);
83 shift(v);
84 if (lastBitOfV) v[0] ^= P128;
85 }
86 // calculate Z128
87 if (getBit(x, 127)) {
88 for (int n = 0; n < z.length; n++) {
89 z[n] ^= v[n];
90 }
91 }
92 return z;
93 }
94
95 // hash subkey H; should not change after the object has been constructed
96 private final byte[] subkeyH;
97
98 // buffer for storing hash
99 private byte[] state;
100
101 // variables for save/restore calls
102 private byte[] stateSave = null;
103
104 /**
105 * Initializes the cipher in the specified mode with the given key
106 * and iv.
107 *
108 * @param subkeyH the hash subkey
109 *
110 * @exception ProviderException if the given key is inappropriate for
111 * initializing this digest
112 */
113 GHASH(byte[] subkeyH) throws ProviderException {
114 if ((subkeyH == null) || subkeyH.length != AES_BLOCK_SIZE) {
115 throw new ProviderException("Internal error");
116 }
117 this.subkeyH = subkeyH;
118 this.state = new byte[AES_BLOCK_SIZE];
119 }
120
121 /**
122 * Resets the GHASH object to its original state, i.e. blank w/
123 * the same subkey H. Used after digest() is called and to re-use
124 * this object for different data w/ the same H.
125 */
126 void reset() {
127 Arrays.fill(state, (byte) 0);
128 }
129
130 /**
131 * Save the current snapshot of this GHASH object.
132 */
133 void save() {
134 stateSave = state.clone();
135 }
136
137 /**
138 * Restores this object using the saved snapshot.
139 */
140 void restore() {
141 state = stateSave;
142 }
143
144 private void processBlock(byte[] data, int ofs) {
145 if (data.length - ofs < AES_BLOCK_SIZE) {
146 throw new RuntimeException("need complete block");
147 }
148 for (int n = 0; n < state.length; n++) {
149 state[n] ^= data[ofs + n];
150 }
151 state = blockMult(state, subkeyH);
152 }
153
154 void update(byte[] in) {
155 update(in, 0, in.length);
156 }
157
158 void update(byte[] in, int inOfs, int inLen) {
159 if (inLen - inOfs > in.length) {
160 throw new RuntimeException("input length out of bound");
161 }
162 if (inLen % AES_BLOCK_SIZE != 0) {
163 throw new RuntimeException("input length unsupported");
164 }
165
166 for (int i = inOfs; i < (inOfs + inLen); i += AES_BLOCK_SIZE) {
167 processBlock(in, i);
168 }
169 }
170
171 byte[] digest() {
172 try {
173 return state.clone();
174 } finally {
175 reset();
176 }
177 }
178 }