1/*	$OpenBSD: hash.c,v 1.5 2024/02/27 11:28:30 claudio Exp $ */
2/*
3 * Copyright (c) 2019 Kristaps Dzonsons <kristaps@bsd.lv>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17#include <sys/types.h>
18
19#include <assert.h>
20#include <endian.h>
21#include <stdint.h>
22#include <stdlib.h>
23
24#include <openssl/md4.h>
25
26#include "extern.h"
27
28/*
29 * A fast 32-bit hash.
30 * Described in Tridgell's "Efficient Algorithms for Sorting and
31 * Synchronization" thesis and the "Rolling checksum" document.
32 */
33uint32_t
34hash_fast(const void *buf, size_t len)
35{
36	size_t			 i = 0;
37	uint32_t		 a = 0, /* part of a(k, l) */
38				 b = 0; /* b(k, l) */
39	const signed char	*dat = buf;
40
41	if (len > 4)
42		for ( ; i < len - 4; i += 4) {
43			b += 4 * (a + dat[i]) +
44			    3 * dat[i + 1] +
45			    2 * dat[i + 2] +
46			    dat[i + 3];
47			a += dat[i + 0] +
48			    dat[i + 1] +
49			    dat[i + 2] +
50			    dat[i + 3];
51		}
52
53	for ( ; i < len; i++) {
54		a += dat[i];
55		b += a;
56	}
57
58	/* s(k, l) = (eps % M) + 2^16 b(k, l) % M */
59
60	return (a & 0xffff) + (b << 16);
61}
62
63/*
64 * Slow MD4-based hash with trailing seed.
65 */
66void
67hash_slow(const void *buf, size_t len,
68	unsigned char *md, const struct sess *sess)
69{
70	MD4_CTX		 ctx;
71	int32_t		 seed = htole32(sess->seed);
72
73	MD4_Init(&ctx);
74	MD4_Update(&ctx, buf, len);
75	MD4_Update(&ctx, (unsigned char *)&seed, sizeof(int32_t));
76	MD4_Final(md, &ctx);
77}
78
79/*
80 * Hash an entire file.
81 * This is similar to hash_slow() except the seed is hashed at the end
82 * of the sequence, not the beginning.
83 */
84void
85hash_file_start(MD4_CTX *ctx, const struct sess *sess)
86{
87	int32_t		 seed = htole32(sess->seed);
88
89	MD4_Init(ctx);
90	MD4_Update(ctx, (unsigned char *)&seed, sizeof(int32_t));
91}
92
93void
94hash_file_buf(MD4_CTX *ctx, const void *buf, size_t len)
95{
96	MD4_Update(ctx, buf, len);
97}
98void
99hash_file_final(MD4_CTX *ctx, unsigned char *md)
100{
101	MD4_Final(md, ctx);
102}
103