1/*
2 *  linux/fs/ext3/hash.c
3 *
4 * Copyright (C) 2002 by Theodore Ts'o
5 *
6 * This file is released under the GPL v2.
7 *
8 * This file may be redistributed under the terms of the GNU Public
9 * License.
10 */
11
12#include "ext3.h"
13#include <linux/cryptohash.h>
14
15#define DELTA 0x9E3779B9
16
17static void TEA_transform(__u32 buf[4], __u32 const in[])
18{
19	__u32	sum = 0;
20	__u32	b0 = buf[0], b1 = buf[1];
21	__u32	a = in[0], b = in[1], c = in[2], d = in[3];
22	int	n = 16;
23
24	do {
25		sum += DELTA;
26		b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
27		b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
28	} while(--n);
29
30	buf[0] += b0;
31	buf[1] += b1;
32}
33
34
35/* The old legacy hash */
36static __u32 dx_hack_hash_unsigned(const char *name, int len)
37{
38	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
39	const unsigned char *ucp = (const unsigned char *) name;
40
41	while (len--) {
42		hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));
43
44		if (hash & 0x80000000)
45			hash -= 0x7fffffff;
46		hash1 = hash0;
47		hash0 = hash;
48	}
49	return hash0 << 1;
50}
51
52static __u32 dx_hack_hash_signed(const char *name, int len)
53{
54	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
55	const signed char *scp = (const signed char *) name;
56
57	while (len--) {
58		hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));
59
60		if (hash & 0x80000000)
61			hash -= 0x7fffffff;
62		hash1 = hash0;
63		hash0 = hash;
64	}
65	return hash0 << 1;
66}
67
68static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
69{
70	__u32	pad, val;
71	int	i;
72	const signed char *scp = (const signed char *) msg;
73
74	pad = (__u32)len | ((__u32)len << 8);
75	pad |= pad << 16;
76
77	val = pad;
78	if (len > num*4)
79		len = num * 4;
80	for (i = 0; i < len; i++) {
81		if ((i % 4) == 0)
82			val = pad;
83		val = ((int) scp[i]) + (val << 8);
84		if ((i % 4) == 3) {
85			*buf++ = val;
86			val = pad;
87			num--;
88		}
89	}
90	if (--num >= 0)
91		*buf++ = val;
92	while (--num >= 0)
93		*buf++ = pad;
94}
95
96static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
97{
98	__u32	pad, val;
99	int	i;
100	const unsigned char *ucp = (const unsigned char *) msg;
101
102	pad = (__u32)len | ((__u32)len << 8);
103	pad |= pad << 16;
104
105	val = pad;
106	if (len > num*4)
107		len = num * 4;
108	for (i=0; i < len; i++) {
109		if ((i % 4) == 0)
110			val = pad;
111		val = ((int) ucp[i]) + (val << 8);
112		if ((i % 4) == 3) {
113			*buf++ = val;
114			val = pad;
115			num--;
116		}
117	}
118	if (--num >= 0)
119		*buf++ = val;
120	while (--num >= 0)
121		*buf++ = pad;
122}
123
124/*
125 * Returns the hash of a filename.  If len is 0 and name is NULL, then
126 * this function can be used to test whether or not a hash version is
127 * supported.
128 *
129 * The seed is an 4 longword (32 bits) "secret" which can be used to
130 * uniquify a hash.  If the seed is all zero's, then some default seed
131 * may be used.
132 *
133 * A particular hash version specifies whether or not the seed is
134 * represented, and whether or not the returned hash is 32 bits or 64
135 * bits.  32 bit hashes will return 0 for the minor hash.
136 */
137int ext3fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
138{
139	__u32	hash;
140	__u32	minor_hash = 0;
141	const char	*p;
142	int		i;
143	__u32		in[8], buf[4];
144	void		(*str2hashbuf)(const char *, int, __u32 *, int) =
145				str2hashbuf_signed;
146
147	/* Initialize the default seed for the hash checksum functions */
148	buf[0] = 0x67452301;
149	buf[1] = 0xefcdab89;
150	buf[2] = 0x98badcfe;
151	buf[3] = 0x10325476;
152
153	/* Check to see if the seed is all zero's */
154	if (hinfo->seed) {
155		for (i=0; i < 4; i++) {
156			if (hinfo->seed[i])
157				break;
158		}
159		if (i < 4)
160			memcpy(buf, hinfo->seed, sizeof(buf));
161	}
162
163	switch (hinfo->hash_version) {
164	case DX_HASH_LEGACY_UNSIGNED:
165		hash = dx_hack_hash_unsigned(name, len);
166		break;
167	case DX_HASH_LEGACY:
168		hash = dx_hack_hash_signed(name, len);
169		break;
170	case DX_HASH_HALF_MD4_UNSIGNED:
171		str2hashbuf = str2hashbuf_unsigned;
172	case DX_HASH_HALF_MD4:
173		p = name;
174		while (len > 0) {
175			(*str2hashbuf)(p, len, in, 8);
176			half_md4_transform(buf, in);
177			len -= 32;
178			p += 32;
179		}
180		minor_hash = buf[2];
181		hash = buf[1];
182		break;
183	case DX_HASH_TEA_UNSIGNED:
184		str2hashbuf = str2hashbuf_unsigned;
185	case DX_HASH_TEA:
186		p = name;
187		while (len > 0) {
188			(*str2hashbuf)(p, len, in, 4);
189			TEA_transform(buf, in);
190			len -= 16;
191			p += 16;
192		}
193		hash = buf[0];
194		minor_hash = buf[1];
195		break;
196	default:
197		hinfo->hash = 0;
198		return -1;
199	}
200	hash = hash & ~1;
201	if (hash == (EXT3_HTREE_EOF_32BIT << 1))
202		hash = (EXT3_HTREE_EOF_32BIT - 1) << 1;
203	hinfo->hash = hash;
204	hinfo->minor_hash = minor_hash;
205	return 0;
206}
207