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}