1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/fs/ext4/hash.c 4 * 5 * Copyright (C) 2002 by Theodore Ts'o 6 */ 7 8 #include <linux/fs.h> 9 #include <linux/unicode.h> 10 #include <linux/compiler.h> 11 #include <linux/bitops.h> 12 #include "ext4.h" 13 14 #define DELTA 0x9E3779B9 15 16 static void TEA_transform(__u32 buf[4], __u32 const in[]) 17 { 18 __u32 sum = 0; 19 __u32 b0 = buf[0], b1 = buf[1]; 20 __u32 a = in[0], b = in[1], c = in[2], d = in[3]; 21 int n = 16; 22 23 do { 24 sum += DELTA; 25 b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b); 26 b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d); 27 } while (--n); 28 29 buf[0] += b0; 30 buf[1] += b1; 31 } 32 33 /* F, G and H are basic MD4 functions: selection, majority, parity */ 34 #define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z)))) 35 #define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z))) 36 #define H(x, y, z) ((x) ^ (y) ^ (z)) 37 38 /* 39 * The generic round function. The application is so specific that 40 * we don't bother protecting all the arguments with parens, as is generally 41 * good macro practice, in favor of extra legibility. 42 * Rotation is separate from addition to prevent recomputation 43 */ 44 #define ROUND(f, a, b, c, d, x, s) \ 45 (a += f(b, c, d) + x, a = rol32(a, s)) 46 #define K1 0 47 #define K2 013240474631UL 48 #define K3 015666365641UL 49 50 /* 51 * Basic cut-down MD4 transform. Returns only 32 bits of result. 52 */ 53 static __u32 half_md4_transform(__u32 buf[4], __u32 const in[8]) 54 { 55 __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3]; 56 57 /* Round 1 */ 58 ROUND(F, a, b, c, d, in[0] + K1, 3); 59 ROUND(F, d, a, b, c, in[1] + K1, 7); 60 ROUND(F, c, d, a, b, in[2] + K1, 11); 61 ROUND(F, b, c, d, a, in[3] + K1, 19); 62 ROUND(F, a, b, c, d, in[4] + K1, 3); 63 ROUND(F, d, a, b, c, in[5] + K1, 7); 64 ROUND(F, c, d, a, b, in[6] + K1, 11); 65 ROUND(F, b, c, d, a, in[7] + K1, 19); 66 67 /* Round 2 */ 68 ROUND(G, a, b, c, d, in[1] + K2, 3); 69 ROUND(G, d, a, b, c, in[3] + K2, 5); 70 ROUND(G, c, d, a, b, in[5] + K2, 9); 71 ROUND(G, b, c, d, a, in[7] + K2, 13); 72 ROUND(G, a, b, c, d, in[0] + K2, 3); 73 ROUND(G, d, a, b, c, in[2] + K2, 5); 74 ROUND(G, c, d, a, b, in[4] + K2, 9); 75 ROUND(G, b, c, d, a, in[6] + K2, 13); 76 77 /* Round 3 */ 78 ROUND(H, a, b, c, d, in[3] + K3, 3); 79 ROUND(H, d, a, b, c, in[7] + K3, 9); 80 ROUND(H, c, d, a, b, in[2] + K3, 11); 81 ROUND(H, b, c, d, a, in[6] + K3, 15); 82 ROUND(H, a, b, c, d, in[1] + K3, 3); 83 ROUND(H, d, a, b, c, in[5] + K3, 9); 84 ROUND(H, c, d, a, b, in[0] + K3, 11); 85 ROUND(H, b, c, d, a, in[4] + K3, 15); 86 87 buf[0] += a; 88 buf[1] += b; 89 buf[2] += c; 90 buf[3] += d; 91 92 return buf[1]; /* "most hashed" word */ 93 } 94 #undef ROUND 95 #undef K1 96 #undef K2 97 #undef K3 98 #undef F 99 #undef G 100 #undef H 101 102 /* The old legacy hash */ 103 static __u32 dx_hack_hash_unsigned(const char *name, int len) 104 { 105 __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9; 106 const unsigned char *ucp = (const unsigned char *) name; 107 108 while (len--) { 109 hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373)); 110 111 if (hash & 0x80000000) 112 hash -= 0x7fffffff; 113 hash1 = hash0; 114 hash0 = hash; 115 } 116 return hash0 << 1; 117 } 118 119 static __u32 dx_hack_hash_signed(const char *name, int len) 120 { 121 __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9; 122 const signed char *scp = (const signed char *) name; 123 124 while (len--) { 125 hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373)); 126 127 if (hash & 0x80000000) 128 hash -= 0x7fffffff; 129 hash1 = hash0; 130 hash0 = hash; 131 } 132 return hash0 << 1; 133 } 134 135 static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num) 136 { 137 __u32 pad, val; 138 int i; 139 const signed char *scp = (const signed char *) msg; 140 141 pad = (__u32)len | ((__u32)len << 8); 142 pad |= pad << 16; 143 144 val = pad; 145 if (len > num*4) 146 len = num * 4; 147 for (i = 0; i < len; i++) { 148 val = ((int) scp[i]) + (val << 8); 149 if ((i % 4) == 3) { 150 *buf++ = val; 151 val = pad; 152 num--; 153 } 154 } 155 if (--num >= 0) 156 *buf++ = val; 157 while (--num >= 0) 158 *buf++ = pad; 159 } 160 161 static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num) 162 { 163 __u32 pad, val; 164 int i; 165 const unsigned char *ucp = (const unsigned char *) msg; 166 167 pad = (__u32)len | ((__u32)len << 8); 168 pad |= pad << 16; 169 170 val = pad; 171 if (len > num*4) 172 len = num * 4; 173 for (i = 0; i < len; i++) { 174 val = ((int) ucp[i]) + (val << 8); 175 if ((i % 4) == 3) { 176 *buf++ = val; 177 val = pad; 178 num--; 179 } 180 } 181 if (--num >= 0) 182 *buf++ = val; 183 while (--num >= 0) 184 *buf++ = pad; 185 } 186 187 /* 188 * Returns the hash of a filename. If len is 0 and name is NULL, then 189 * this function can be used to test whether or not a hash version is 190 * supported. 191 * 192 * The seed is an 4 longword (32 bits) "secret" which can be used to 193 * uniquify a hash. If the seed is all zero's, then some default seed 194 * may be used. 195 * 196 * A particular hash version specifies whether or not the seed is 197 * represented, and whether or not the returned hash is 32 bits or 64 198 * bits. 32 bit hashes will return 0 for the minor hash. 199 */ 200 static int __ext4fs_dirhash(const char *name, int len, 201 struct dx_hash_info *hinfo) 202 { 203 __u32 hash; 204 __u32 minor_hash = 0; 205 const char *p; 206 int i; 207 __u32 in[8], buf[4]; 208 void (*str2hashbuf)(const char *, int, __u32 *, int) = 209 str2hashbuf_signed; 210 211 /* Initialize the default seed for the hash checksum functions */ 212 buf[0] = 0x67452301; 213 buf[1] = 0xefcdab89; 214 buf[2] = 0x98badcfe; 215 buf[3] = 0x10325476; 216 217 /* Check to see if the seed is all zero's */ 218 if (hinfo->seed) { 219 for (i = 0; i < 4; i++) { 220 if (hinfo->seed[i]) { 221 memcpy(buf, hinfo->seed, sizeof(buf)); 222 break; 223 } 224 } 225 } 226 227 switch (hinfo->hash_version) { 228 case DX_HASH_LEGACY_UNSIGNED: 229 hash = dx_hack_hash_unsigned(name, len); 230 break; 231 case DX_HASH_LEGACY: 232 hash = dx_hack_hash_signed(name, len); 233 break; 234 case DX_HASH_HALF_MD4_UNSIGNED: 235 str2hashbuf = str2hashbuf_unsigned; 236 /* fall through */ 237 case DX_HASH_HALF_MD4: 238 p = name; 239 while (len > 0) { 240 (*str2hashbuf)(p, len, in, 8); 241 half_md4_transform(buf, in); 242 len -= 32; 243 p += 32; 244 } 245 minor_hash = buf[2]; 246 hash = buf[1]; 247 break; 248 case DX_HASH_TEA_UNSIGNED: 249 str2hashbuf = str2hashbuf_unsigned; 250 /* fall through */ 251 case DX_HASH_TEA: 252 p = name; 253 while (len > 0) { 254 (*str2hashbuf)(p, len, in, 4); 255 TEA_transform(buf, in); 256 len -= 16; 257 p += 16; 258 } 259 hash = buf[0]; 260 minor_hash = buf[1]; 261 break; 262 default: 263 hinfo->hash = 0; 264 return -1; 265 } 266 hash = hash & ~1; 267 if (hash == (EXT4_HTREE_EOF_32BIT << 1)) 268 hash = (EXT4_HTREE_EOF_32BIT - 1) << 1; 269 hinfo->hash = hash; 270 hinfo->minor_hash = minor_hash; 271 return 0; 272 } 273 274 int ext4fs_dirhash(const struct inode *dir, const char *name, int len, 275 struct dx_hash_info *hinfo) 276 { 277 #ifdef CONFIG_UNICODE 278 const struct unicode_map *um = EXT4_SB(dir->i_sb)->s_encoding; 279 int r, dlen; 280 unsigned char *buff; 281 struct qstr qstr = {.name = name, .len = len }; 282 283 if (len && IS_CASEFOLDED(dir) && um) { 284 buff = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL); 285 if (!buff) 286 return -ENOMEM; 287 288 dlen = utf8_casefold(um, &qstr, buff, PATH_MAX); 289 if (dlen < 0) { 290 kfree(buff); 291 goto opaque_seq; 292 } 293 294 r = __ext4fs_dirhash(buff, dlen, hinfo); 295 296 kfree(buff); 297 return r; 298 } 299 opaque_seq: 300 #endif 301 return __ext4fs_dirhash(name, len, hinfo); 302 } 303