2 * dirhash.c -- Calculate the hash of a directory entry
4 * Copyright (c) 2001 Daniel Phillips
6 * Copyright (c) 2002 Theodore Ts'o.
9 * This file may be redistributed under the terms of the GNU Public
21 * Keyed 32-bit hash function using TEA in a Davis-Meyer function
23 * Hi = E Mi(Hi-1) + Hi-1
25 * (see Applied Cryptography, 2nd edition, p448).
27 * Jeremy Fitzhardinge <jeremy@zip.com.au> 1998
29 * This code is made available under the terms of the GPL
31 #define DELTA 0x9E3779B9
33 static void TEA_transform(__u32 buf[4], __u32 const in[])
36 __u32 b0 = buf[0], b1 = buf[1];
37 __u32 a = in[0], b = in[1], c = in[2], d = in[3];
42 b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
43 b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
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))
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
61 #define ROUND(f, a, b, c, d, x, s) \
62 (a += f(b, c, d) + x, a = (a << s) | (a >> (32-s)))
64 #define K2 013240474631UL
65 #define K3 015666365641UL
68 * Basic cut-down MD4 transform. Returns only 32 bits of result.
70 static void halfMD4Transform (__u32 buf[4], __u32 const in[])
72 __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];
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);
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);
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);
118 /* The old legacy hash */
119 static ext2_dirhash_t dx_hack_hash (const char *name, int len)
121 __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
123 __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373));
125 if (hash & 0x80000000) hash -= 0x7fffffff;
132 static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
137 pad = (__u32)len | ((__u32)len << 8);
143 for (i=0; i < len; i++) {
146 val = msg[i] + (val << 8);
160 * Returns the hash of a filename. If len is 0 and name is NULL, then
161 * this function can be used to test whether or not a hash version is
164 * The seed is an 4 longword (32 bits) "secret" which can be used to
165 * uniquify a hash. If the seed is all zero's, then some default seed
168 * A particular hash version specifies whether or not the seed is
169 * represented, and whether or not the returned hash is 32 bits or 64
170 * bits. 32 bit hashes will return 0 for the minor hash.
172 errcode_t ext2fs_dirhash(int version, const char *name, int len,
174 ext2_dirhash_t *ret_hash,
175 ext2_dirhash_t *ret_minor_hash)
178 __u32 minor_hash = 0;
183 /* Initialize the default seed for the hash checksum functions */
189 /* Check to see if the seed is all zero's */
191 for (i=0; i < 4; i++) {
196 memcpy(buf, seed, sizeof(buf));
200 case EXT2_HASH_LEGACY:
201 hash = dx_hack_hash(name, len);
203 case EXT2_HASH_HALF_MD4:
206 str2hashbuf(p, len, in, 8);
207 halfMD4Transform(buf, in);
217 str2hashbuf(p, len, in, 4);
218 TEA_transform(buf, in);
227 return EXT2_ET_DIRHASH_UNSUPP;
229 *ret_hash = hash & ~1;
231 *ret_minor_hash = minor_hash;