1/*
2 *  linux/fs/ext4/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 <linux/fs.h>
13#include <linux/cryptohash.h>
14#include "ext4.h"
15
16#define DELTA 0x9E3779B9
17
18static void TEA_transform(__u32 buf[4], __u32 const in[])
19{
20	__u32	sum = 0;
21	__u32	b0 = buf[0], b1 = buf[1];
22	__u32	a = in[0], b = in[1], c = in[2], d = in[3];
23	int	n = 16;
24
25	do {
26		sum += DELTA;
27		b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
28		b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
29	} while (--n);
30
31	buf[0] += b0;
32	buf[1] += b1;
33}
34
35
36/* The old legacy hash */
37static __u32 dx_hack_hash_unsigned(const char *name, int len)
38{
39	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
40	const unsigned char *ucp = (const unsigned char *) name;
41
42	while (len--) {
43		hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));
44
45		if (hash & 0x80000000)
46			hash -= 0x7fffffff;
47		hash1 = hash0;
48		hash0 = hash;
49	}
50	return hash0 << 1;
51}
52
53static __u32 dx_hack_hash_signed(const char *name, int len)
54{
55	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
56	const signed char *scp = (const signed char *) name;
57
58	while (len--) {
59		hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));
60
61		if (hash & 0x80000000)
62			hash -= 0x7fffffff;
63		hash1 = hash0;
64		hash0 = hash;
65	}
66	return hash0 << 1;
67}
68
69static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
70{
71	__u32	pad, val;
72	int	i;
73	const signed char *scp = (const signed char *) msg;
74
75	pad = (__u32)len | ((__u32)len << 8);
76	pad |= pad << 16;
77
78	val = pad;
79	if (len > num*4)
80		len = num * 4;
81	for (i = 0; i < len; i++) {
82		if ((i % 4) == 0)
83			val = pad;
84		val = ((int) scp[i]) + (val << 8);
85		if ((i % 4) == 3) {
86			*buf++ = val;
87			val = pad;
88			num--;
89		}
90	}
91	if (--num >= 0)
92		*buf++ = val;
93	while (--num >= 0)
94		*buf++ = pad;
95}
96
97static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
98{
99	__u32	pad, val;
100	int	i;
101	const unsigned char *ucp = (const unsigned char *) msg;
102
103	pad = (__u32)len | ((__u32)len << 8);
104	pad |= pad << 16;
105
106	val = pad;
107	if (len > num*4)
108		len = num * 4;
109	for (i = 0; i < len; i++) {
110		if ((i % 4) == 0)
111			val = pad;
112		val = ((int) ucp[i]) + (val << 8);
113		if ((i % 4) == 3) {
114			*buf++ = val;
115			val = pad;
116			num--;
117		}
118	}
119	if (--num >= 0)
120		*buf++ = val;
121	while (--num >= 0)
122		*buf++ = pad;
123}
124
125/*
126 * Returns the hash of a filename.  If len is 0 and name is NULL, then
127 * this function can be used to test whether or not a hash version is
128 * supported.
129 *
130 * The seed is an 4 longword (32 bits) "secret" which can be used to
131 * uniquify a hash.  If the seed is all zero's, then some default seed
132 * may be used.
133 *
134 * A particular hash version specifies whether or not the seed is
135 * represented, and whether or not the returned hash is 32 bits or 64
136 * bits.  32 bit hashes will return 0 for the minor hash.
137 */
138int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
139{
140	__u32	hash;
141	__u32	minor_hash = 0;
142	const char	*p;
143	int		i;
144	__u32		in[8], buf[4];
145	void		(*str2hashbuf)(const char *, int, __u32 *, int) =
146				str2hashbuf_signed;
147
148	/* Initialize the default seed for the hash checksum functions */
149	buf[0] = 0x67452301;
150	buf[1] = 0xefcdab89;
151	buf[2] = 0x98badcfe;
152	buf[3] = 0x10325476;
153
154	/* Check to see if the seed is all zero's */
155	if (hinfo->seed) {
156		for (i = 0; i < 4; i++) {
157			if (hinfo->seed[i]) {
158				memcpy(buf, hinfo->seed, sizeof(buf));
159				break;
160			}
161		}
162	}
163
164	switch (hinfo->hash_version) {
165	case DX_HASH_LEGACY_UNSIGNED:
166		hash = dx_hack_hash_unsigned(name, len);
167		break;
168	case DX_HASH_LEGACY:
169		hash = dx_hack_hash_signed(name, len);
170		break;
171	case DX_HASH_HALF_MD4_UNSIGNED:
172		str2hashbuf = str2hashbuf_unsigned;
173	case DX_HASH_HALF_MD4:
174		p = name;
175		while (len > 0) {
176			(*str2hashbuf)(p, len, in, 8);
177			half_md4_transform(buf, in);
178			len -= 32;
179			p += 32;
180		}
181		minor_hash = buf[2];
182		hash = buf[1];
183		break;
184	case DX_HASH_TEA_UNSIGNED:
185		str2hashbuf = str2hashbuf_unsigned;
186	case DX_HASH_TEA:
187		p = name;
188		while (len > 0) {
189			(*str2hashbuf)(p, len, in, 4);
190			TEA_transform(buf, in);
191			len -= 16;
192			p += 16;
193		}
194		hash = buf[0];
195		minor_hash = buf[1];
196		break;
197	default:
198		hinfo->hash = 0;
199		return -1;
200	}
201	hash = hash & ~1;
202	if (hash == (EXT4_HTREE_EOF_32BIT << 1))
203		hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;
204	hinfo->hash = hash;
205	hinfo->minor_hash = minor_hash;
206	return 0;
207}
208