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Diffstat (limited to 'e2fsprogs/ext2fs/dirhash.c')
| -rw-r--r-- | e2fsprogs/ext2fs/dirhash.c | 233 |
1 files changed, 233 insertions, 0 deletions
diff --git a/e2fsprogs/ext2fs/dirhash.c b/e2fsprogs/ext2fs/dirhash.c new file mode 100644 index 0000000..4d18593 --- /dev/null +++ b/e2fsprogs/ext2fs/dirhash.c @@ -0,0 +1,233 @@ +/* + * dirhash.c -- Calculate the hash of a directory entry + * + * Copyright (c) 2001 Daniel Phillips + * + * Copyright (c) 2002 Theodore Ts'o. + * + * %Begin-Header% + * This file may be redistributed under the terms of the GNU Public + * License. + * %End-Header% + */ + +#include <stdio.h> +#include <string.h> + +#include "ext2_fs.h" +#include "ext2fs.h" + +/* + * Keyed 32-bit hash function using TEA in a Davis-Meyer function + * H0 = Key + * Hi = E Mi(Hi-1) + Hi-1 + * + * (see Applied Cryptography, 2nd edition, p448). + * + * Jeremy Fitzhardinge <jeremy@zip.com.au> 1998 + * + * This code is made available under the terms of the GPL + */ +#define DELTA 0x9E3779B9 + +static void TEA_transform(__u32 buf[4], __u32 const in[]) +{ + __u32 sum = 0; + __u32 b0 = buf[0], b1 = buf[1]; + __u32 a = in[0], b = in[1], c = in[2], d = in[3]; + int n = 16; + + do { + sum += DELTA; + b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b); + b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d); + } while(--n); + + buf[0] += b0; + buf[1] += b1; +} + +/* F, G and H are basic MD4 functions: selection, majority, parity */ +#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z)))) +#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z))) +#define H(x, y, z) ((x) ^ (y) ^ (z)) + +/* + * The generic round function. The application is so specific that + * we don't bother protecting all the arguments with parens, as is generally + * good macro practice, in favor of extra legibility. + * Rotation is separate from addition to prevent recomputation + */ +#define ROUND(f, a, b, c, d, x, s) \ + (a += f(b, c, d) + x, a = (a << s) | (a >> (32-s))) +#define K1 0 +#define K2 013240474631UL +#define K3 015666365641UL + +/* + * Basic cut-down MD4 transform. Returns only 32 bits of result. + */ +static void halfMD4Transform (__u32 buf[4], __u32 const in[]) +{ + __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3]; + + /* Round 1 */ + ROUND(F, a, b, c, d, in[0] + K1, 3); + ROUND(F, d, a, b, c, in[1] + K1, 7); + ROUND(F, c, d, a, b, in[2] + K1, 11); + ROUND(F, b, c, d, a, in[3] + K1, 19); + ROUND(F, a, b, c, d, in[4] + K1, 3); + ROUND(F, d, a, b, c, in[5] + K1, 7); + ROUND(F, c, d, a, b, in[6] + K1, 11); + ROUND(F, b, c, d, a, in[7] + K1, 19); + + /* Round 2 */ + ROUND(G, a, b, c, d, in[1] + K2, 3); + ROUND(G, d, a, b, c, in[3] + K2, 5); + ROUND(G, c, d, a, b, in[5] + K2, 9); + ROUND(G, b, c, d, a, in[7] + K2, 13); + ROUND(G, a, b, c, d, in[0] + K2, 3); + ROUND(G, d, a, b, c, in[2] + K2, 5); + ROUND(G, c, d, a, b, in[4] + K2, 9); + ROUND(G, b, c, d, a, in[6] + K2, 13); + + /* Round 3 */ + ROUND(H, a, b, c, d, in[3] + K3, 3); + ROUND(H, d, a, b, c, in[7] + K3, 9); + ROUND(H, c, d, a, b, in[2] + K3, 11); + ROUND(H, b, c, d, a, in[6] + K3, 15); + ROUND(H, a, b, c, d, in[1] + K3, 3); + ROUND(H, d, a, b, c, in[5] + K3, 9); + ROUND(H, c, d, a, b, in[0] + K3, 11); + ROUND(H, b, c, d, a, in[4] + K3, 15); + + buf[0] += a; + buf[1] += b; + buf[2] += c; + buf[3] += d; +} + +#undef ROUND +#undef F +#undef G +#undef H +#undef K1 +#undef K2 +#undef K3 + +/* The old legacy hash */ +static ext2_dirhash_t dx_hack_hash (const char *name, int len) +{ + __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9; + while (len--) { + __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373)); + + if (hash & 0x80000000) hash -= 0x7fffffff; + hash1 = hash0; + hash0 = hash; + } + return (hash0 << 1); +} + +static void str2hashbuf(const char *msg, int len, __u32 *buf, int num) +{ + __u32 pad, val; + int i; + + pad = (__u32)len | ((__u32)len << 8); + pad |= pad << 16; + + val = pad; + if (len > num*4) + len = num * 4; + for (i=0; i < len; i++) { + if ((i % 4) == 0) + val = pad; + val = msg[i] + (val << 8); + if ((i % 4) == 3) { + *buf++ = val; + val = pad; + num--; + } + } + if (--num >= 0) + *buf++ = val; + while (--num >= 0) + *buf++ = pad; +} + +/* + * Returns the hash of a filename. If len is 0 and name is NULL, then + * this function can be used to test whether or not a hash version is + * supported. + * + * The seed is an 4 longword (32 bits) "secret" which can be used to + * uniquify a hash. If the seed is all zero's, then some default seed + * may be used. + * + * A particular hash version specifies whether or not the seed is + * represented, and whether or not the returned hash is 32 bits or 64 + * bits. 32 bit hashes will return 0 for the minor hash. + */ +errcode_t ext2fs_dirhash(int version, const char *name, int len, + const __u32 *seed, + ext2_dirhash_t *ret_hash, + ext2_dirhash_t *ret_minor_hash) +{ + __u32 hash; + __u32 minor_hash = 0; + const char *p; + int i; + __u32 in[8], buf[4]; + + /* Initialize the default seed for the hash checksum functions */ + buf[0] = 0x67452301; + buf[1] = 0xefcdab89; + buf[2] = 0x98badcfe; + buf[3] = 0x10325476; + + /* Check to see if the seed is all zero's */ + if (seed) { + for (i=0; i < 4; i++) { + if (seed[i]) + break; + } + if (i < 4) + memcpy(buf, seed, sizeof(buf)); + } + + switch (version) { + case EXT2_HASH_LEGACY: + hash = dx_hack_hash(name, len); + break; + case EXT2_HASH_HALF_MD4: + p = name; + while (len > 0) { + str2hashbuf(p, len, in, 8); + halfMD4Transform(buf, in); + len -= 32; + p += 32; + } + minor_hash = buf[2]; + hash = buf[1]; + break; + case EXT2_HASH_TEA: + p = name; + while (len > 0) { + str2hashbuf(p, len, in, 4); + TEA_transform(buf, in); + len -= 16; + p += 16; + } + hash = buf[0]; + minor_hash = buf[1]; + break; + default: + *ret_hash = 0; + return EXT2_ET_DIRHASH_UNSUPP; + } + *ret_hash = hash & ~1; + if (ret_minor_hash) + *ret_minor_hash = minor_hash; + return 0; +} |