1/*
2 * Copyright (c) 2013, 2015, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2015 Red Hat, Inc.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.  Oracle designates this
9 * particular file as subject to the "Classpath" exception as provided
10 * by Oracle in the LICENSE file that accompanied this code.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
23 * or visit www.oracle.com if you need additional information or have any
24 * questions.
25 */
26/*
27 * (C) Copyright IBM Corp. 2013
28 */
29
30package com.sun.crypto.provider;
31
32import java.security.ProviderException;
33
34import jdk.internal.HotSpotIntrinsicCandidate;
35
36/**
37 * This class represents the GHASH function defined in NIST 800-38D
38 * under section 6.4. It needs to be constructed w/ a hash subkey, i.e.
39 * block H. Given input of 128-bit blocks, it will process and output
40 * a 128-bit block.
41 *
42 * <p>This function is used in the implementation of GCM mode.
43 *
44 * @since 1.8
45 */
46final class GHASH {
47
48    private static long getLong(byte[] buffer, int offset) {
49        long result = 0;
50        int end = offset + 8;
51        for (int i = offset; i < end; ++i) {
52            result = (result << 8) + (buffer[i] & 0xFF);
53        }
54        return result;
55    }
56
57    private static void putLong(byte[] buffer, int offset, long value) {
58        int end = offset + 8;
59        for (int i = end - 1; i >= offset; --i) {
60            buffer[i] = (byte) value;
61            value >>= 8;
62        }
63    }
64
65    private static final int AES_BLOCK_SIZE = 16;
66
67    // Multiplies state[0], state[1] by subkeyH[0], subkeyH[1].
68    private static void blockMult(long[] st, long[] subH) {
69        long Z0 = 0;
70        long Z1 = 0;
71        long V0 = subH[0];
72        long V1 = subH[1];
73        long X;
74
75        // Separate loops for processing state[0] and state[1].
76        X = st[0];
77        for (int i = 0; i < 64; i++) {
78            // Zi+1 = Zi if bit i of x is 0
79            long mask = X >> 63;
80            Z0 ^= V0 & mask;
81            Z1 ^= V1 & mask;
82
83            // Save mask for conditional reduction below.
84            mask = (V1 << 63) >> 63;
85
86            // V = rightshift(V)
87            long carry = V0 & 1;
88            V0 = V0 >>> 1;
89            V1 = (V1 >>> 1) | (carry << 63);
90
91            // Conditional reduction modulo P128.
92            V0 ^= 0xe100000000000000L & mask;
93            X <<= 1;
94        }
95
96        X = st[1];
97        for (int i = 64; i < 127; i++) {
98            // Zi+1 = Zi if bit i of x is 0
99            long mask = X >> 63;
100            Z0 ^= V0 & mask;
101            Z1 ^= V1 & mask;
102
103            // Save mask for conditional reduction below.
104            mask = (V1 << 63) >> 63;
105
106            // V = rightshift(V)
107            long carry = V0 & 1;
108            V0 = V0 >>> 1;
109            V1 = (V1 >>> 1) | (carry << 63);
110
111            // Conditional reduction.
112            V0 ^= 0xe100000000000000L & mask;
113            X <<= 1;
114        }
115
116        // calculate Z128
117        long mask = X >> 63;
118        Z0 ^= V0 & mask;
119        Z1 ^= V1 & mask;
120
121        // Save result.
122        st[0] = Z0;
123        st[1] = Z1;
124
125    }
126
127    /* subkeyH and state are stored in long[] for GHASH intrinsic use */
128
129    // hash subkey H; should not change after the object has been constructed
130    private final long[] subkeyH;
131
132    // buffer for storing hash
133    private final long[] state;
134
135    // variables for save/restore calls
136    private long stateSave0, stateSave1;
137
138    /**
139     * Initializes the cipher in the specified mode with the given key
140     * and iv.
141     *
142     * @param subkeyH the hash subkey
143     *
144     * @exception ProviderException if the given key is inappropriate for
145     * initializing this digest
146     */
147    GHASH(byte[] subkeyH) throws ProviderException {
148        if ((subkeyH == null) || subkeyH.length != AES_BLOCK_SIZE) {
149            throw new ProviderException("Internal error");
150        }
151        state = new long[2];
152        this.subkeyH = new long[2];
153        this.subkeyH[0] = getLong(subkeyH, 0);
154        this.subkeyH[1] = getLong(subkeyH, 8);
155    }
156
157    /**
158     * Resets the GHASH object to its original state, i.e. blank w/
159     * the same subkey H. Used after digest() is called and to re-use
160     * this object for different data w/ the same H.
161     */
162    void reset() {
163        state[0] = 0;
164        state[1] = 0;
165    }
166
167    /**
168     * Save the current snapshot of this GHASH object.
169     */
170    void save() {
171        stateSave0 = state[0];
172        stateSave1 = state[1];
173    }
174
175    /**
176     * Restores this object using the saved snapshot.
177     */
178    void restore() {
179        state[0] = stateSave0;
180        state[1] = stateSave1;
181    }
182
183    private static void processBlock(byte[] data, int ofs, long[] st, long[] subH) {
184        st[0] ^= getLong(data, ofs);
185        st[1] ^= getLong(data, ofs + 8);
186        blockMult(st, subH);
187    }
188
189    void update(byte[] in) {
190        update(in, 0, in.length);
191    }
192
193    void update(byte[] in, int inOfs, int inLen) {
194        if (inLen == 0) {
195            return;
196        }
197        ghashRangeCheck(in, inOfs, inLen, state, subkeyH);
198        processBlocks(in, inOfs, inLen/AES_BLOCK_SIZE, state, subkeyH);
199    }
200
201    private static void ghashRangeCheck(byte[] in, int inOfs, int inLen, long[] st, long[] subH) {
202        if (inLen < 0) {
203            throw new RuntimeException("invalid input length: " + inLen);
204        }
205        if (inOfs < 0) {
206            throw new RuntimeException("invalid offset: " + inOfs);
207        }
208        if (inLen > in.length - inOfs) {
209            throw new RuntimeException("input length out of bound: " +
210                                       inLen + " > " + (in.length - inOfs));
211        }
212        if (inLen % AES_BLOCK_SIZE != 0) {
213            throw new RuntimeException("input length/block size mismatch: " +
214                                       inLen);
215        }
216
217        // These two checks are for C2 checking
218        if (st.length != 2) {
219            throw new RuntimeException("internal state has invalid length: " +
220                                       st.length);
221        }
222        if (subH.length != 2) {
223            throw new RuntimeException("internal subkeyH has invalid length: " +
224                                       subH.length);
225        }
226    }
227    /*
228     * This is an intrinsified method.  The method's argument list must match
229     * the hotspot signature.  This method and methods called by it, cannot
230     * throw exceptions or allocate arrays as it will breaking intrinsics
231     */
232    @HotSpotIntrinsicCandidate
233    private static void processBlocks(byte[] data, int inOfs, int blocks, long[] st, long[] subH) {
234        int offset = inOfs;
235        while (blocks > 0) {
236            processBlock(data, offset, st, subH);
237            blocks--;
238            offset += AES_BLOCK_SIZE;
239        }
240    }
241
242    byte[] digest() {
243        byte[] result = new byte[AES_BLOCK_SIZE];
244        putLong(result, 0, state[0]);
245        putLong(result, 8, state[1]);
246        reset();
247        return result;
248    }
249}
250