librsync  2.3.4
checksum.c
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" /* IWYU pragma: keep */
25#include <stdint.h>
26#include "checksum.h"
27#include "blake2.h"
28#include "librsync_export.h"
29
30LIBRSYNC_EXPORT const int RS_MD4_SUM_LENGTH = 16;
31LIBRSYNC_EXPORT const int RS_BLAKE2_SUM_LENGTH = 32;
32
33/** A simple 32bit checksum that can be incrementally updated. */
34rs_weak_sum_t rs_calc_weak_sum(weaksum_kind_t kind, void const *buf, size_t len)
35{
36 if (kind == RS_ROLLSUM) {
37 Rollsum sum;
38 RollsumInit(&sum);
39 RollsumUpdate(&sum, buf, len);
40 return RollsumDigest(&sum);
41 } else {
42 rabinkarp_t sum;
43 rabinkarp_init(&sum);
44 rabinkarp_update(&sum, buf, len);
45 return rabinkarp_digest(&sum);
46 }
47}
48
49/** Calculate and store into SUM a strong checksum.
50 *
51 * In plain rsync, the checksum is perturbed by a seed value. This is used when
52 * retrying a failed transmission: we've discovered that the hashes collided at
53 * some point, so we're going to try again with different hashes to see if we
54 * can get it right. (Check tridge's thesis for details and to see if that's
55 * correct.)
56 *
57 * Since we can't retry I'm not sure if it's very useful for librsync, except
58 * perhaps as protection against hash collision attacks. */
59void rs_calc_strong_sum(strongsum_kind_t kind, void const *buf, size_t len,
60 rs_strong_sum_t *sum)
61{
62 if (kind == RS_MD4) {
63 rs_mdfour((unsigned char *)sum, buf, len);
64 } else {
65 blake2b_state ctx;
66 blake2b_init(&ctx, RS_MAX_STRONG_SUM_LENGTH);
67 blake2b_update(&ctx, (const uint8_t *)buf, len);
68 blake2b_final(&ctx, (uint8_t *)sum, RS_MAX_STRONG_SUM_LENGTH);
69 }
70}
Abstract wrappers around different weaksum and strongsum implementations.
rs_weak_sum_t rs_calc_weak_sum(weaksum_kind_t kind, void const *buf, size_t len)
Calculate a weaksum.
Definition: checksum.c:34
strongsum_kind_t
Strongsum implementations.
Definition: checksum.h:41
weaksum_kind_t
Weaksum implementations.
Definition: checksum.h:35
void rs_calc_strong_sum(strongsum_kind_t kind, void const *buf, size_t len, rs_strong_sum_t *sum)
Calculate a strongsum.
Definition: checksum.c:59
The Rollsum state type.
Definition: rollsum.h:36
The rabinkarp_t state type.
Definition: rabinkarp.h:56
The rs_mdfour state type.
Definition: mdfour.h:46