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