2 * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
32 internal class RecordDecryptGCM : RecordDecrypt {
40 internal RecordDecryptGCM(IBlockCipher bc, byte[] iv)
43 this.iv = new byte[12];
44 Array.Copy(iv, 0, this.iv, 0, 4);
52 internal override bool CheckLength(int len)
54 return len >= 24 && len <= (16384 + 24);
57 internal override bool Decrypt(int recordType, int version,
58 byte[] data, ref int off, ref int len)
62 IO.Enc64be(seq, tmp, 0);
63 IO.WriteHeader(recordType, version, len, tmp, 8);
64 IO.Enc64be(13 << 3, tmp, 13);
65 IO.Enc64be((ulong)len << 3, tmp, 21);
66 for (int i = 0; i < 16; i ++) {
69 GHASH.Run(tag, h, tmp, 0, 13);
70 GHASH.Run(tag, h, data, off, len);
71 GHASH.Run(tag, h, tmp, 13, 16);
74 Array.Copy(data, off - 8, iv, 4, 8);
75 bc.CTRRun(iv, 2, data, off, len);
76 bc.CTRRun(iv, 1, data, off + len, 16);
79 for (int i = 0; i < 16; i ++) {
80 z |= tag[i] ^ data[off + len + i];