1 | /*
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2 | * dirhash.c -- Calculate the hash of a directory entry
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3 | *
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4 | * Copyright (c) 2001 Daniel Phillips
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5 | *
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6 | * Copyright (c) 2002 Theodore Ts'o.
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7 | *
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8 | * %Begin-Header%
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9 | * This file may be redistributed under the terms of the GNU Public
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10 | * License.
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11 | * %End-Header%
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12 | */
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13 |
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14 | #include <stdio.h>
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15 | #include <string.h>
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16 |
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17 | #include "ext2_fs.h"
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18 | #include "ext2fs.h"
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19 |
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20 | /*
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21 | * Keyed 32-bit hash function using TEA in a Davis-Meyer function
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22 | * H0 = Key
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23 | * Hi = E Mi(Hi-1) + Hi-1
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24 | *
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25 | * (see Applied Cryptography, 2nd edition, p448).
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26 | *
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27 | * Jeremy Fitzhardinge <jeremy@zip.com.au> 1998
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28 | *
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29 | * This code is made available under the terms of the GPL
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30 | */
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31 | #define DELTA 0x9E3779B9
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32 |
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33 | static void TEA_transform(__u32 buf[4], __u32 const in[])
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34 | {
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35 | __u32 sum = 0;
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36 | __u32 b0 = buf[0], b1 = buf[1];
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37 | __u32 a = in[0], b = in[1], c = in[2], d = in[3];
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38 | int n = 16;
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39 |
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40 | do {
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41 | sum += DELTA;
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42 | b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
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43 | b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
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44 | } while(--n);
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45 |
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46 | buf[0] += b0;
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47 | buf[1] += b1;
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48 | }
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49 |
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50 | /* F, G and H are basic MD4 functions: selection, majority, parity */
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51 | #define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
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52 | #define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
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53 | #define H(x, y, z) ((x) ^ (y) ^ (z))
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54 |
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55 | /*
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56 | * The generic round function. The application is so specific that
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57 | * we don't bother protecting all the arguments with parens, as is generally
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58 | * good macro practice, in favor of extra legibility.
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59 | * Rotation is separate from addition to prevent recomputation
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60 | */
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61 | #define ROUND(f, a, b, c, d, x, s) \
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62 | (a += f(b, c, d) + x, a = (a << s) | (a >> (32-s)))
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63 | #define K1 0
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64 | #define K2 013240474631UL
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65 | #define K3 015666365641UL
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66 |
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67 | /*
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68 | * Basic cut-down MD4 transform. Returns only 32 bits of result.
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69 | */
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70 | static void halfMD4Transform (__u32 buf[4], __u32 const in[])
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71 | {
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72 | __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];
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73 |
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74 | /* Round 1 */
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75 | ROUND(F, a, b, c, d, in[0] + K1, 3);
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76 | ROUND(F, d, a, b, c, in[1] + K1, 7);
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77 | ROUND(F, c, d, a, b, in[2] + K1, 11);
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78 | ROUND(F, b, c, d, a, in[3] + K1, 19);
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79 | ROUND(F, a, b, c, d, in[4] + K1, 3);
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80 | ROUND(F, d, a, b, c, in[5] + K1, 7);
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81 | ROUND(F, c, d, a, b, in[6] + K1, 11);
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82 | ROUND(F, b, c, d, a, in[7] + K1, 19);
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83 |
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84 | /* Round 2 */
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85 | ROUND(G, a, b, c, d, in[1] + K2, 3);
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86 | ROUND(G, d, a, b, c, in[3] + K2, 5);
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87 | ROUND(G, c, d, a, b, in[5] + K2, 9);
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88 | ROUND(G, b, c, d, a, in[7] + K2, 13);
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89 | ROUND(G, a, b, c, d, in[0] + K2, 3);
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90 | ROUND(G, d, a, b, c, in[2] + K2, 5);
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91 | ROUND(G, c, d, a, b, in[4] + K2, 9);
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92 | ROUND(G, b, c, d, a, in[6] + K2, 13);
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93 |
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94 | /* Round 3 */
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95 | ROUND(H, a, b, c, d, in[3] + K3, 3);
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96 | ROUND(H, d, a, b, c, in[7] + K3, 9);
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97 | ROUND(H, c, d, a, b, in[2] + K3, 11);
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98 | ROUND(H, b, c, d, a, in[6] + K3, 15);
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99 | ROUND(H, a, b, c, d, in[1] + K3, 3);
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100 | ROUND(H, d, a, b, c, in[5] + K3, 9);
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101 | ROUND(H, c, d, a, b, in[0] + K3, 11);
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102 | ROUND(H, b, c, d, a, in[4] + K3, 15);
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103 |
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104 | buf[0] += a;
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105 | buf[1] += b;
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106 | buf[2] += c;
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107 | buf[3] += d;
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108 | }
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109 |
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110 | #undef ROUND
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111 | #undef F
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112 | #undef G
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113 | #undef H
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114 | #undef K1
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115 | #undef K2
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116 | #undef K3
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117 |
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118 | /* The old legacy hash */
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119 | static ext2_dirhash_t dx_hack_hash (const char *name, int len)
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120 | {
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121 | __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
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122 | while (len--) {
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123 | __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373));
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124 |
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125 | if (hash & 0x80000000) hash -= 0x7fffffff;
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126 | hash1 = hash0;
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127 | hash0 = hash;
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128 | }
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129 | return (hash0 << 1);
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130 | }
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131 |
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132 | static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
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133 | {
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134 | __u32 pad, val;
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135 | int i;
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136 |
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137 | pad = (__u32)len | ((__u32)len << 8);
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138 | pad |= pad << 16;
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139 |
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140 | val = pad;
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141 | if (len > num*4)
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142 | len = num * 4;
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143 | for (i=0; i < len; i++) {
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144 | if ((i % 4) == 0)
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145 | val = pad;
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146 | val = msg[i] + (val << 8);
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147 | if ((i % 4) == 3) {
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148 | *buf++ = val;
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149 | val = pad;
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150 | num--;
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151 | }
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152 | }
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153 | if (--num >= 0)
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154 | *buf++ = val;
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155 | while (--num >= 0)
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156 | *buf++ = pad;
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157 | }
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158 |
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159 | /*
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160 | * Returns the hash of a filename. If len is 0 and name is NULL, then
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161 | * this function can be used to test whether or not a hash version is
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162 | * supported.
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163 | *
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164 | * The seed is an 4 longword (32 bits) "secret" which can be used to
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165 | * uniquify a hash. If the seed is all zero's, then some default seed
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166 | * may be used.
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167 | *
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168 | * A particular hash version specifies whether or not the seed is
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169 | * represented, and whether or not the returned hash is 32 bits or 64
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170 | * bits. 32 bit hashes will return 0 for the minor hash.
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171 | */
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172 | errcode_t ext2fs_dirhash(int version, const char *name, int len,
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173 | const __u32 *seed,
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174 | ext2_dirhash_t *ret_hash,
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175 | ext2_dirhash_t *ret_minor_hash)
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176 | {
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177 | __u32 hash;
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178 | __u32 minor_hash = 0;
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179 | const char *p;
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180 | int i;
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181 | __u32 in[8], buf[4];
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182 |
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183 | /* Initialize the default seed for the hash checksum functions */
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184 | buf[0] = 0x67452301;
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185 | buf[1] = 0xefcdab89;
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186 | buf[2] = 0x98badcfe;
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187 | buf[3] = 0x10325476;
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188 |
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189 | /* Check to see if the seed is all zero's */
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190 | if (seed) {
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191 | for (i=0; i < 4; i++) {
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192 | if (seed[i])
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193 | break;
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194 | }
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195 | if (i < 4)
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196 | memcpy(buf, seed, sizeof(buf));
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197 | }
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198 |
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199 | switch (version) {
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200 | case EXT2_HASH_LEGACY:
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201 | hash = dx_hack_hash(name, len);
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202 | break;
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203 | case EXT2_HASH_HALF_MD4:
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204 | p = name;
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205 | while (len > 0) {
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206 | str2hashbuf(p, len, in, 8);
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207 | halfMD4Transform(buf, in);
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208 | len -= 32;
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209 | p += 32;
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210 | }
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211 | minor_hash = buf[2];
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212 | hash = buf[1];
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213 | break;
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214 | case EXT2_HASH_TEA:
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215 | p = name;
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216 | while (len > 0) {
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217 | str2hashbuf(p, len, in, 4);
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218 | TEA_transform(buf, in);
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219 | len -= 16;
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220 | p += 16;
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221 | }
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222 | hash = buf[0];
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223 | minor_hash = buf[1];
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224 | break;
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225 | default:
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226 | *ret_hash = 0;
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227 | return EXT2_ET_DIRHASH_UNSUPP;
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228 | }
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229 | *ret_hash = hash & ~1;
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230 | if (ret_minor_hash)
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231 | *ret_minor_hash = minor_hash;
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232 | return 0;
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233 | }
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