dirhash.c revision e0ed7404719a9ddd2ba427a80db5365c8bad18c0
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 33static 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 */ 70static 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 */ 119static 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 141static 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 */ 189errcode_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