1/* vi: set sw=4 ts=4: */ 2/* 3 * dirhash.c -- Calculate the hash of a directory entry 4 * 5 * Copyright (c) 2001 Daniel Phillips 6 * 7 * Copyright (c) 2002 Theodore Ts'o. 8 * 9 * %Begin-Header% 10 * This file may be redistributed under the terms of the GNU Public 11 * License. 12 * %End-Header% 13 */ 14 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{ 122 __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9; 123 while (len--) { 124 __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373)); 125 126 if (hash & 0x80000000) hash -= 0x7fffffff; 127 hash1 = hash0; 128 hash0 = hash; 129 } 130 return (hash0 << 1); 131} 132 133static void str2hashbuf(const char *msg, int len, __u32 *buf, int num) 134{ 135 __u32 pad, val; 136 int i; 137 138 pad = (__u32)len | ((__u32)len << 8); 139 pad |= pad << 16; 140 141 val = pad; 142 if (len > num*4) 143 len = num * 4; 144 for (i=0; i < len; i++) { 145 if ((i % 4) == 0) 146 val = pad; 147 val = msg[i] + (val << 8); 148 if ((i % 4) == 3) { 149 *buf++ = val; 150 val = pad; 151 num--; 152 } 153 } 154 if (--num >= 0) 155 *buf++ = val; 156 while (--num >= 0) 157 *buf++ = pad; 158} 159 160/* 161 * Returns the hash of a filename. If len is 0 and name is NULL, then 162 * this function can be used to test whether or not a hash version is 163 * supported. 164 * 165 * The seed is an 4 longword (32 bits) "secret" which can be used to 166 * uniquify a hash. If the seed is all zero's, then some default seed 167 * may be used. 168 * 169 * A particular hash version specifies whether or not the seed is 170 * represented, and whether or not the returned hash is 32 bits or 64 171 * bits. 32 bit hashes will return 0 for the minor hash. 172 */ 173errcode_t ext2fs_dirhash(int version, const char *name, int len, 174 const __u32 *seed, 175 ext2_dirhash_t *ret_hash, 176 ext2_dirhash_t *ret_minor_hash) 177{ 178 __u32 hash; 179 __u32 minor_hash = 0; 180 const char *p; 181 int i; 182 __u32 in[8], buf[4]; 183 184 /* Initialize the default seed for the hash checksum functions */ 185 buf[0] = 0x67452301; 186 buf[1] = 0xefcdab89; 187 buf[2] = 0x98badcfe; 188 buf[3] = 0x10325476; 189 190 /* Check to see if the seed is all zero's */ 191 if (seed) { 192 for (i=0; i < 4; i++) { 193 if (seed[i]) 194 break; 195 } 196 if (i < 4) 197 memcpy(buf, seed, sizeof(buf)); 198 } 199 200 switch (version) { 201 case EXT2_HASH_LEGACY: 202 hash = dx_hack_hash(name, len); 203 break; 204 case EXT2_HASH_HALF_MD4: 205 p = name; 206 while (len > 0) { 207 str2hashbuf(p, len, in, 8); 208 halfMD4Transform(buf, in); 209 len -= 32; 210 p += 32; 211 } 212 minor_hash = buf[2]; 213 hash = buf[1]; 214 break; 215 case EXT2_HASH_TEA: 216 p = name; 217 while (len > 0) { 218 str2hashbuf(p, len, in, 4); 219 TEA_transform(buf, in); 220 len -= 16; 221 p += 16; 222 } 223 hash = buf[0]; 224 minor_hash = buf[1]; 225 break; 226 default: 227 *ret_hash = 0; 228 return EXT2_ET_DIRHASH_UNSUPP; 229 } 230 *ret_hash = hash & ~1; 231 if (ret_minor_hash) 232 *ret_minor_hash = minor_hash; 233 return 0; 234} 235