• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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 
TEA_transform(__u32 buf[4],__u32 const in[])34 static 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  */
halfMD4Transform(__u32 buf[4],__u32 const in[])71 static 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 */
dx_hack_hash(const char * name,int len,int unsigned_flag)120 static 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 
str2hashbuf(const char * msg,int len,__u32 * buf,int num,int unsigned_flag)142 static 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  */
ext2fs_dirhash(int version,const char * name,int len,const __u32 * seed,ext2_dirhash_t * ret_hash,ext2_dirhash_t * ret_minor_hash)190 errcode_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