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 34static 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 */ 71static 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 */ 120static 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 142static 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 ((i % 4) == 0) 158 val = pad; 159 if (unsigned_flag) 160 c = (int) ucp[i]; 161 else 162 c = (int) scp[i]; 163 164 val = c + (val << 8); 165 if ((i % 4) == 3) { 166 *buf++ = val; 167 val = pad; 168 num--; 169 } 170 } 171 if (--num >= 0) 172 *buf++ = val; 173 while (--num >= 0) 174 *buf++ = pad; 175} 176 177/* 178 * Returns the hash of a filename. If len is 0 and name is NULL, then 179 * this function can be used to test whether or not a hash version is 180 * supported. 181 * 182 * The seed is an 4 longword (32 bits) "secret" which can be used to 183 * uniquify a hash. If the seed is all zero's, then some default seed 184 * may be used. 185 * 186 * A particular hash version specifies whether or not the seed is 187 * represented, and whether or not the returned hash is 32 bits or 64 188 * bits. 32 bit hashes will return 0 for the minor hash. 189 */ 190errcode_t ext2fs_dirhash(int version, const char *name, int len, 191 const __u32 *seed, 192 ext2_dirhash_t *ret_hash, 193 ext2_dirhash_t *ret_minor_hash) 194{ 195 __u32 hash; 196 __u32 minor_hash = 0; 197 const char *p; 198 int i; 199 __u32 in[8], buf[4]; 200 int unsigned_flag = 0; 201 202 /* Initialize the default seed for the hash checksum functions */ 203 buf[0] = 0x67452301; 204 buf[1] = 0xefcdab89; 205 buf[2] = 0x98badcfe; 206 buf[3] = 0x10325476; 207 208 /* Check to see if the seed is all zero's */ 209 if (seed) { 210 for (i=0; i < 4; i++) { 211 if (seed[i]) 212 break; 213 } 214 if (i < 4) 215 memcpy(buf, seed, sizeof(buf)); 216 } 217 218 switch (version) { 219 case EXT2_HASH_LEGACY_UNSIGNED: 220 unsigned_flag++; 221 /* fallthrough */ 222 case EXT2_HASH_LEGACY: 223 hash = dx_hack_hash(name, len, unsigned_flag); 224 break; 225 case EXT2_HASH_HALF_MD4_UNSIGNED: 226 unsigned_flag++; 227 /* fallthrough */ 228 case EXT2_HASH_HALF_MD4: 229 p = name; 230 while (len > 0) { 231 str2hashbuf(p, len, in, 8, unsigned_flag); 232 halfMD4Transform(buf, in); 233 len -= 32; 234 p += 32; 235 } 236 minor_hash = buf[2]; 237 hash = buf[1]; 238 break; 239 case EXT2_HASH_TEA_UNSIGNED: 240 unsigned_flag++; 241 /* fallthrough */ 242 case EXT2_HASH_TEA: 243 p = name; 244 while (len > 0) { 245 str2hashbuf(p, len, in, 4, unsigned_flag); 246 TEA_transform(buf, in); 247 len -= 16; 248 p += 16; 249 } 250 hash = buf[0]; 251 minor_hash = buf[1]; 252 break; 253 default: 254 *ret_hash = 0; 255 return EXT2_ET_DIRHASH_UNSUPP; 256 } 257 *ret_hash = hash & ~1; 258 if (ret_minor_hash) 259 *ret_minor_hash = minor_hash; 260 return 0; 261} 262