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 (unsigned_flag)
158 c = (int) ucp[i];
159 else
160 c = (int) scp[i];
161
162 val = c + (val << 8);
163 if ((i % 4) == 3) {
164 *buf++ = val;
165 val = pad;
166 num--;
167 }
168 }
169 if (--num >= 0)
170 *buf++ = val;
171 while (--num >= 0)
172 *buf++ = pad;
173 }
174
175 /*
176 * Returns the hash of a filename. If len is 0 and name is NULL, then
177 * this function can be used to test whether or not a hash version is
178 * supported.
179 *
180 * The seed is an 4 longword (32 bits) "secret" which can be used to
181 * uniquify a hash. If the seed is all zero's, then some default seed
182 * may be used.
183 *
184 * A particular hash version specifies whether or not the seed is
185 * represented, and whether or not the returned hash is 32 bits or 64
186 * bits. 32 bit hashes will return 0 for the minor hash.
187 */
ext2fs_dirhash(int version,const char * name,int len,const __u32 * seed,ext2_dirhash_t * ret_hash,ext2_dirhash_t * ret_minor_hash)188 errcode_t ext2fs_dirhash(int version, const char *name, int len,
189 const __u32 *seed,
190 ext2_dirhash_t *ret_hash,
191 ext2_dirhash_t *ret_minor_hash)
192 {
193 __u32 hash;
194 __u32 minor_hash = 0;
195 const char *p;
196 int i;
197 __u32 in[8], buf[4];
198 int unsigned_flag = 0;
199
200 /* Initialize the default seed for the hash checksum functions */
201 buf[0] = 0x67452301;
202 buf[1] = 0xefcdab89;
203 buf[2] = 0x98badcfe;
204 buf[3] = 0x10325476;
205
206 /* Check to see if the seed is all zero's */
207 if (seed) {
208 for (i=0; i < 4; i++) {
209 if (seed[i])
210 break;
211 }
212 if (i < 4)
213 memcpy(buf, seed, sizeof(buf));
214 }
215
216 switch (version) {
217 case EXT2_HASH_LEGACY_UNSIGNED:
218 unsigned_flag++;
219 /* fallthrough */
220 case EXT2_HASH_LEGACY:
221 hash = dx_hack_hash(name, len, unsigned_flag);
222 break;
223 case EXT2_HASH_HALF_MD4_UNSIGNED:
224 unsigned_flag++;
225 /* fallthrough */
226 case EXT2_HASH_HALF_MD4:
227 p = name;
228 while (len > 0) {
229 str2hashbuf(p, len, in, 8, unsigned_flag);
230 halfMD4Transform(buf, in);
231 len -= 32;
232 p += 32;
233 }
234 minor_hash = buf[2];
235 hash = buf[1];
236 break;
237 case EXT2_HASH_TEA_UNSIGNED:
238 unsigned_flag++;
239 /* fallthrough */
240 case EXT2_HASH_TEA:
241 p = name;
242 while (len > 0) {
243 str2hashbuf(p, len, in, 4, unsigned_flag);
244 TEA_transform(buf, in);
245 len -= 16;
246 p += 16;
247 }
248 hash = buf[0];
249 minor_hash = buf[1];
250 break;
251 default:
252 *ret_hash = 0;
253 return EXT2_ET_DIRHASH_UNSUPP;
254 }
255 *ret_hash = hash & ~1;
256 if (ret_minor_hash)
257 *ret_minor_hash = minor_hash;
258 return 0;
259 }
260