1/*
2 * dirhash.c -- Calculate the hash of a directory entry
3 *
4 * Copyright (c) 2001  Daniel Phillips
5 *
6 * Copyright (c) 2002 Theodore Ts'o.
7 *
8 * %Begin-Header%
9 * This file may be redistributed under the terms of the GNU Library
10 * General Public License, version 2.
11 * %End-Header%
12 */
13
14#include "config.h"
15#include <stdio.h>
16#include <string.h>
17
18#include "ext2_fs.h"
19#include "ext2fs.h"
20
21/*
22 * Keyed 32-bit hash function using TEA in a Davis-Meyer function
23 *   H0 = Key
24 *   Hi = E Mi(Hi-1) + Hi-1
25 *
26 * (see Applied Cryptography, 2nd edition, p448).
27 *
28 * Jeremy Fitzhardinge <jeremy@zip.com.au> 1998
29 *
30 * This code is made available under the terms of the GPL
31 */
32#define DELTA 0x9E3779B9
33
34static void TEA_transform(__u32 buf[4], __u32 const in[])
35{
36	__u32	sum = 0;
37	__u32	b0 = buf[0], b1 = buf[1];
38	__u32	a = in[0], b = in[1], c = in[2], d = in[3];
39	int	n = 16;
40
41	do {
42		sum += DELTA;
43		b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
44		b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
45	} while(--n);
46
47	buf[0] += b0;
48	buf[1] += b1;
49}
50
51/* F, G and H are basic MD4 functions: selection, majority, parity */
52#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
53#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
54#define H(x, y, z) ((x) ^ (y) ^ (z))
55
56/*
57 * The generic round function.  The application is so specific that
58 * we don't bother protecting all the arguments with parens, as is generally
59 * good macro practice, in favor of extra legibility.
60 * Rotation is separate from addition to prevent recomputation
61 */
62#define ROUND(f, a, b, c, d, x, s)	\
63	(a += f(b, c, d) + x, a = (a << s) | (a >> (32-s)))
64#define K1 0
65#define K2 013240474631UL
66#define K3 015666365641UL
67
68/*
69 * Basic cut-down MD4 transform.  Returns only 32 bits of result.
70 */
71static void halfMD4Transform (__u32 buf[4], __u32 const in[])
72{
73	__u32	a = buf[0], b = buf[1], c = buf[2], d = buf[3];
74
75	/* Round 1 */
76	ROUND(F, a, b, c, d, in[0] + K1,  3);
77	ROUND(F, d, a, b, c, in[1] + K1,  7);
78	ROUND(F, c, d, a, b, in[2] + K1, 11);
79	ROUND(F, b, c, d, a, in[3] + K1, 19);
80	ROUND(F, a, b, c, d, in[4] + K1,  3);
81	ROUND(F, d, a, b, c, in[5] + K1,  7);
82	ROUND(F, c, d, a, b, in[6] + K1, 11);
83	ROUND(F, b, c, d, a, in[7] + K1, 19);
84
85	/* Round 2 */
86	ROUND(G, a, b, c, d, in[1] + K2,  3);
87	ROUND(G, d, a, b, c, in[3] + K2,  5);
88	ROUND(G, c, d, a, b, in[5] + K2,  9);
89	ROUND(G, b, c, d, a, in[7] + K2, 13);
90	ROUND(G, a, b, c, d, in[0] + K2,  3);
91	ROUND(G, d, a, b, c, in[2] + K2,  5);
92	ROUND(G, c, d, a, b, in[4] + K2,  9);
93	ROUND(G, b, c, d, a, in[6] + K2, 13);
94
95	/* Round 3 */
96	ROUND(H, a, b, c, d, in[3] + K3,  3);
97	ROUND(H, d, a, b, c, in[7] + K3,  9);
98	ROUND(H, c, d, a, b, in[2] + K3, 11);
99	ROUND(H, b, c, d, a, in[6] + K3, 15);
100	ROUND(H, a, b, c, d, in[1] + K3,  3);
101	ROUND(H, d, a, b, c, in[5] + K3,  9);
102	ROUND(H, c, d, a, b, in[0] + K3, 11);
103	ROUND(H, b, c, d, a, in[4] + K3, 15);
104
105	buf[0] += a;
106	buf[1] += b;
107	buf[2] += c;
108	buf[3] += d;
109}
110
111#undef ROUND
112#undef F
113#undef G
114#undef H
115#undef K1
116#undef K2
117#undef K3
118
119/* The old legacy hash */
120static ext2_dirhash_t dx_hack_hash (const char *name, int len,
121				    int unsigned_flag)
122{
123	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
124	const unsigned char *ucp = (const unsigned char *) name;
125	const signed char *scp = (const signed char *) name;
126	int c;
127
128	while (len--) {
129		if (unsigned_flag)
130			c = (int) *ucp++;
131		else
132			c = (int) *scp++;
133		hash = hash1 + (hash0 ^ (c * 7152373));
134
135		if (hash & 0x80000000) hash -= 0x7fffffff;
136		hash1 = hash0;
137		hash0 = hash;
138	}
139	return (hash0 << 1);
140}
141
142static void str2hashbuf(const char *msg, int len, __u32 *buf, int num,
143			int unsigned_flag)
144{
145	__u32	pad, val;
146	int	i, c;
147	const unsigned char *ucp = (const unsigned char *) msg;
148	const signed char *scp = (const signed char *) msg;
149
150	pad = (__u32)len | ((__u32)len << 8);
151	pad |= pad << 16;
152
153	val = pad;
154	if (len > num*4)
155		len = num * 4;
156	for (i=0; i < len; i++) {
157		if ((i % 4) == 0)
158			val = pad;
159		if (unsigned_flag)
160			c = (int) ucp[i];
161		else
162			c = (int) scp[i];
163
164		val = c + (val << 8);
165		if ((i % 4) == 3) {
166			*buf++ = val;
167			val = pad;
168			num--;
169		}
170	}
171	if (--num >= 0)
172		*buf++ = val;
173	while (--num >= 0)
174		*buf++ = pad;
175}
176
177/*
178 * Returns the hash of a filename.  If len is 0 and name is NULL, then
179 * this function can be used to test whether or not a hash version is
180 * supported.
181 *
182 * The seed is an 4 longword (32 bits) "secret" which can be used to
183 * uniquify a hash.  If the seed is all zero's, then some default seed
184 * may be used.
185 *
186 * A particular hash version specifies whether or not the seed is
187 * represented, and whether or not the returned hash is 32 bits or 64
188 * bits.  32 bit hashes will return 0 for the minor hash.
189 */
190errcode_t ext2fs_dirhash(int version, const char *name, int len,
191			 const __u32 *seed,
192			 ext2_dirhash_t *ret_hash,
193			 ext2_dirhash_t *ret_minor_hash)
194{
195	__u32	hash;
196	__u32	minor_hash = 0;
197	const char	*p;
198	int		i;
199	__u32 		in[8], buf[4];
200	int		unsigned_flag = 0;
201
202	/* Initialize the default seed for the hash checksum functions */
203	buf[0] = 0x67452301;
204	buf[1] = 0xefcdab89;
205	buf[2] = 0x98badcfe;
206	buf[3] = 0x10325476;
207
208	/* Check to see if the seed is all zero's */
209	if (seed) {
210		for (i=0; i < 4; i++) {
211			if (seed[i])
212				break;
213		}
214		if (i < 4)
215			memcpy(buf, seed, sizeof(buf));
216	}
217
218	switch (version) {
219	case EXT2_HASH_LEGACY_UNSIGNED:
220		unsigned_flag++;
221		/* fallthrough */
222	case EXT2_HASH_LEGACY:
223		hash = dx_hack_hash(name, len, unsigned_flag);
224		break;
225	case EXT2_HASH_HALF_MD4_UNSIGNED:
226		unsigned_flag++;
227		/* fallthrough */
228	case EXT2_HASH_HALF_MD4:
229		p = name;
230		while (len > 0) {
231			str2hashbuf(p, len, in, 8, unsigned_flag);
232			halfMD4Transform(buf, in);
233			len -= 32;
234			p += 32;
235		}
236		minor_hash = buf[2];
237		hash = buf[1];
238		break;
239	case EXT2_HASH_TEA_UNSIGNED:
240		unsigned_flag++;
241		/* fallthrough */
242	case EXT2_HASH_TEA:
243		p = name;
244		while (len > 0) {
245			str2hashbuf(p, len, in, 4, unsigned_flag);
246			TEA_transform(buf, in);
247			len -= 16;
248			p += 16;
249		}
250		hash = buf[0];
251		minor_hash = buf[1];
252		break;
253	default:
254		*ret_hash = 0;
255		return EXT2_ET_DIRHASH_UNSUPP;
256	}
257	*ret_hash = hash & ~1;
258	if (ret_minor_hash)
259		*ret_minor_hash = minor_hash;
260	return 0;
261}
262