3 Cipher counter mode, optimized for 16-byte blocks.
5 Copyright (C) 2005-2018 Niels Möller
6 Copyright (C) 2018 Red Hat, Inc.
8 This file is part of GNU Nettle.
10 GNU Nettle is free software: you can redistribute it and/or
11 modify it under the terms of either:
13 * the GNU Lesser General Public License as published by the Free
14 Software Foundation; either version 3 of the License, or (at your
15 option) any later version.
19 * the GNU General Public License as published by the Free
20 Software Foundation; either version 2 of the License, or (at your
21 option) any later version.
23 or both in parallel, as here.
25 GNU Nettle is distributed in the hope that it will be useful,
26 but WITHOUT ANY WARRANTY; without even the implied warranty of
27 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
28 General Public License for more details.
30 You should have received copies of the GNU General Public License and
31 the GNU Lesser General Public License along with this program. If
32 not, see http://www.gnu.org/licenses/.
43 #include "ctr-internal.h"
45 #include "nettle-internal.h"
47 #define MIN(a,b) (((a) < (b)) ? (a) : (b))
50 _ctr_crypt16(const void *ctx, nettle_cipher_func *f,
51 nettle_fill16_func *fill, uint8_t *ctr,
52 size_t length, uint8_t *dst,
55 if (dst != src && !((uintptr_t) dst % sizeof(uint64_t)))
57 size_t blocks = length / 16u;
59 fill (ctr, blocks, (union nettle_block16 *) dst);
62 f(ctx, done, dst, dst);
63 memxor (dst, src, done);
67 { /* Left-over partial block */
68 union nettle_block16 block;
72 /* Use fill, to update ctr value in the same way in all cases. */
73 fill (ctr, 1, &block);
74 f (ctx, 16, block.b, block.b);
75 memxor3 (dst, src, block.b, length);
80 /* Construct an aligned buffer of consecutive counter values, of
81 size at most CTR_BUFFER_LIMIT. */
82 TMP_DECL(buffer, union nettle_block16, CTR_BUFFER_LIMIT / 16);
83 size_t blocks = (length + 15) / 16u;
85 TMP_ALLOC(buffer, MIN(blocks, CTR_BUFFER_LIMIT / 16));
87 for (i = 0; blocks >= CTR_BUFFER_LIMIT / 16;
88 i += CTR_BUFFER_LIMIT, blocks -= CTR_BUFFER_LIMIT / 16)
90 fill (ctr, CTR_BUFFER_LIMIT / 16, buffer);
91 f(ctx, CTR_BUFFER_LIMIT, buffer->b, buffer->b);
92 if (length - i < CTR_BUFFER_LIMIT)
94 memxor3 (dst + i, src + i, buffer->b, CTR_BUFFER_LIMIT);
99 assert (length - i < CTR_BUFFER_LIMIT);
100 fill (ctr, blocks, buffer);
101 f(ctx, blocks * 16, buffer->b, buffer->b);
103 memxor3 (dst + i, src + i, buffer->b, length - i);