1 /*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*-
2 *
3 * librsync -- the library for network deltas
4 *
5 * Copyright (C) 1999, 2000, 2001 by Martin Pool <mbp@sourcefrog.net>
6 * Copyright (C) 1996 by Andrew Tridgell
7 * Copyright (C) 1996 by Paul Mackerras
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU Lesser General Public License as published by
11 * the Free Software Foundation; either version 2.1 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
22 */
23
24 #include "config.h"
25 #include "checksum.h"
26 #include "blake2.h"
27
28 LIBRSYNC_EXPORT const int RS_MD4_SUM_LENGTH = 16;
29 LIBRSYNC_EXPORT const int RS_BLAKE2_SUM_LENGTH = 32;
30
31 /** A simple 32bit checksum that can be incrementally updated. */
rs_calc_weak_sum(weaksum_kind_t kind,void const * buf,size_t len)32 rs_weak_sum_t rs_calc_weak_sum(weaksum_kind_t kind, void const *buf, size_t len)
33 {
34 if (kind == RS_ROLLSUM) {
35 Rollsum sum;
36 RollsumInit(&sum);
37 RollsumUpdate(&sum, buf, len);
38 return RollsumDigest(&sum);
39 } else {
40 rabinkarp_t sum;
41 rabinkarp_init(&sum);
42 rabinkarp_update(&sum, buf, len);
43 return rabinkarp_digest(&sum);
44 }
45 }
46
47 /** Calculate and store into SUM a strong checksum.
48 *
49 * In plain rsync, the checksum is perturbed by a seed value. This is used when
50 * retrying a failed transmission: we've discovered that the hashes collided at
51 * some point, so we're going to try again with different hashes to see if we
52 * can get it right. (Check tridge's thesis for details and to see if that's
53 * correct.)
54 *
55 * Since we can't retry I'm not sure if it's very useful for librsync, except
56 * perhaps as protection against hash collision attacks. */
rs_calc_strong_sum(strongsum_kind_t kind,void const * buf,size_t len,rs_strong_sum_t * sum)57 void rs_calc_strong_sum(strongsum_kind_t kind, void const *buf, size_t len,
58 rs_strong_sum_t *sum)
59 {
60 if (kind == RS_MD4) {
61 rs_mdfour((unsigned char *)sum, buf, len);
62 } else {
63 blake2b_state ctx;
64 blake2b_init(&ctx, RS_MAX_STRONG_SUM_LENGTH);
65 blake2b_update(&ctx, (const uint8_t *)buf, len);
66 blake2b_final(&ctx, (uint8_t *)sum, RS_MAX_STRONG_SUM_LENGTH);
67 }
68 }
69