1 /*
2 * linux/fs/ext4/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 <linux/fs.h>
13 #include <linux/jbd2.h>
14 #include <linux/cryptohash.h>
15 #include "ext4.h"
16
17 #define DELTA 0x9E3779B9
18
TEA_transform(__u32 buf[4],__u32 const in[])19 static void TEA_transform(__u32 buf[4], __u32 const in[])
20 {
21 __u32 sum = 0;
22 __u32 b0 = buf[0], b1 = buf[1];
23 __u32 a = in[0], b = in[1], c = in[2], d = in[3];
24 int n = 16;
25
26 do {
27 sum += DELTA;
28 b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
29 b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
30 } while (--n);
31
32 buf[0] += b0;
33 buf[1] += b1;
34 }
35
36
37 /* The old legacy hash */
dx_hack_hash_unsigned(const char * name,int len)38 static __u32 dx_hack_hash_unsigned(const char *name, int len)
39 {
40 __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
41 const unsigned char *ucp = (const unsigned char *) name;
42
43 while (len--) {
44 hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));
45
46 if (hash & 0x80000000)
47 hash -= 0x7fffffff;
48 hash1 = hash0;
49 hash0 = hash;
50 }
51 return hash0 << 1;
52 }
53
dx_hack_hash_signed(const char * name,int len)54 static __u32 dx_hack_hash_signed(const char *name, int len)
55 {
56 __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
57 const signed char *scp = (const signed char *) name;
58
59 while (len--) {
60 hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));
61
62 if (hash & 0x80000000)
63 hash -= 0x7fffffff;
64 hash1 = hash0;
65 hash0 = hash;
66 }
67 return hash0 << 1;
68 }
69
str2hashbuf_signed(const char * msg,int len,__u32 * buf,int num)70 static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
71 {
72 __u32 pad, val;
73 int i;
74 const signed char *scp = (const signed char *) msg;
75
76 pad = (__u32)len | ((__u32)len << 8);
77 pad |= pad << 16;
78
79 val = pad;
80 if (len > num*4)
81 len = num * 4;
82 for (i = 0; i < len; i++) {
83 if ((i % 4) == 0)
84 val = pad;
85 val = ((int) scp[i]) + (val << 8);
86 if ((i % 4) == 3) {
87 *buf++ = val;
88 val = pad;
89 num--;
90 }
91 }
92 if (--num >= 0)
93 *buf++ = val;
94 while (--num >= 0)
95 *buf++ = pad;
96 }
97
str2hashbuf_unsigned(const char * msg,int len,__u32 * buf,int num)98 static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
99 {
100 __u32 pad, val;
101 int i;
102 const unsigned char *ucp = (const unsigned char *) msg;
103
104 pad = (__u32)len | ((__u32)len << 8);
105 pad |= pad << 16;
106
107 val = pad;
108 if (len > num*4)
109 len = num * 4;
110 for (i = 0; i < len; i++) {
111 if ((i % 4) == 0)
112 val = pad;
113 val = ((int) ucp[i]) + (val << 8);
114 if ((i % 4) == 3) {
115 *buf++ = val;
116 val = pad;
117 num--;
118 }
119 }
120 if (--num >= 0)
121 *buf++ = val;
122 while (--num >= 0)
123 *buf++ = pad;
124 }
125
126 /*
127 * Returns the hash of a filename. If len is 0 and name is NULL, then
128 * this function can be used to test whether or not a hash version is
129 * supported.
130 *
131 * The seed is an 4 longword (32 bits) "secret" which can be used to
132 * uniquify a hash. If the seed is all zero's, then some default seed
133 * may be used.
134 *
135 * A particular hash version specifies whether or not the seed is
136 * represented, and whether or not the returned hash is 32 bits or 64
137 * bits. 32 bit hashes will return 0 for the minor hash.
138 */
ext4fs_dirhash(const char * name,int len,struct dx_hash_info * hinfo)139 int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
140 {
141 __u32 hash;
142 __u32 minor_hash = 0;
143 const char *p;
144 int i;
145 __u32 in[8], buf[4];
146 void (*str2hashbuf)(const char *, int, __u32 *, int) =
147 str2hashbuf_signed;
148
149 /* Initialize the default seed for the hash checksum functions */
150 buf[0] = 0x67452301;
151 buf[1] = 0xefcdab89;
152 buf[2] = 0x98badcfe;
153 buf[3] = 0x10325476;
154
155 /* Check to see if the seed is all zero's */
156 if (hinfo->seed) {
157 for (i = 0; i < 4; i++) {
158 if (hinfo->seed[i])
159 break;
160 }
161 if (i < 4)
162 memcpy(buf, hinfo->seed, sizeof(buf));
163 }
164
165 switch (hinfo->hash_version) {
166 case DX_HASH_LEGACY_UNSIGNED:
167 hash = dx_hack_hash_unsigned(name, len);
168 break;
169 case DX_HASH_LEGACY:
170 hash = dx_hack_hash_signed(name, len);
171 break;
172 case DX_HASH_HALF_MD4_UNSIGNED:
173 str2hashbuf = str2hashbuf_unsigned;
174 case DX_HASH_HALF_MD4:
175 p = name;
176 while (len > 0) {
177 (*str2hashbuf)(p, len, in, 8);
178 half_md4_transform(buf, in);
179 len -= 32;
180 p += 32;
181 }
182 minor_hash = buf[2];
183 hash = buf[1];
184 break;
185 case DX_HASH_TEA_UNSIGNED:
186 str2hashbuf = str2hashbuf_unsigned;
187 case DX_HASH_TEA:
188 p = name;
189 while (len > 0) {
190 (*str2hashbuf)(p, len, in, 4);
191 TEA_transform(buf, in);
192 len -= 16;
193 p += 16;
194 }
195 hash = buf[0];
196 minor_hash = buf[1];
197 break;
198 default:
199 hinfo->hash = 0;
200 return -1;
201 }
202 hash = hash & ~1;
203 if (hash == (EXT4_HTREE_EOF_32BIT << 1))
204 hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;
205 hinfo->hash = hash;
206 hinfo->minor_hash = minor_hash;
207 return 0;
208 }
209