fs/ext4/hash.c

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