annotate pkcs_1_pss_encode.c @ 164:cd1143579f00 libtomcrypt LTC_DB_0.44

mpi.c isn't needed if we're using libtommath seperately
author Matt Johnston <matt@ucc.asn.au>
date Sun, 02 Jan 2005 17:19:46 +0000
parents 5d99163f7e32
children
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 *
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9 * Tom St Denis, [email protected], http://libtomcrypt.org
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10 */
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11 #include "mycrypt.h"
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12
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13 /* PKCS #1 PSS Signature Padding -- Tom St Denis */
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14
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15 #ifdef PKCS_1
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16
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17 int pkcs_1_pss_encode(const unsigned char *msghash, unsigned long msghashlen,
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18 unsigned long saltlen, prng_state *prng,
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19 int prng_idx, int hash_idx,
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20 unsigned long modulus_bitlen,
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21 unsigned char *out, unsigned long *outlen)
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22 {
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23 unsigned char *DB, *mask, *salt, *hash;
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24 unsigned long x, y, hLen, modulus_len;
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25 int err;
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26 hash_state md;
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27
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28 _ARGCHK(msghash != NULL);
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29 _ARGCHK(out != NULL);
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30 _ARGCHK(outlen != NULL);
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31
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32 /* ensure hash and PRNG are valid */
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33 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
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34 return err;
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35 }
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36 if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
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37 return err;
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38 }
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39
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40 hLen = hash_descriptor[hash_idx].hashsize;
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41 modulus_len = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0);
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42
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43 /* allocate ram for DB/mask/salt/hash of size modulus_len */
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44 DB = XMALLOC(modulus_len);
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45 mask = XMALLOC(modulus_len);
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46 salt = XMALLOC(modulus_len);
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47 hash = XMALLOC(modulus_len);
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48 if (DB == NULL || mask == NULL || salt == NULL || hash == NULL) {
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49 if (DB != NULL) {
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50 XFREE(DB);
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51 }
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52 if (mask != NULL) {
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53 XFREE(mask);
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54 }
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55 if (salt != NULL) {
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56 XFREE(salt);
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57 }
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58 if (hash != NULL) {
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59 XFREE(hash);
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60 }
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61 return CRYPT_MEM;
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62 }
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63
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64
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65 /* check sizes */
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66 if ((saltlen > modulus_len) || (modulus_len < hLen + saltlen + 2)) {
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67 err = CRYPT_INVALID_ARG;
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68 goto __ERR;
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69 }
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70
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71 /* generate random salt */
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72 if (saltlen > 0) {
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73 if (prng_descriptor[prng_idx].read(salt, saltlen, prng) != saltlen) {
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74 err = CRYPT_ERROR_READPRNG;
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75 goto __ERR;
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76 }
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77 }
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78
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79 /* M = (eight) 0x00 || msghash || salt, hash = H(M) */
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80 if ((err = hash_descriptor[hash_idx].init(&md)) != CRYPT_OK) {
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81 goto __ERR;
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82 }
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83 zeromem(DB, 8);
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84 if ((err = hash_descriptor[hash_idx].process(&md, DB, 8)) != CRYPT_OK) {
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85 goto __ERR;
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86 }
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87 if ((err = hash_descriptor[hash_idx].process(&md, msghash, msghashlen)) != CRYPT_OK) {
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88 goto __ERR;
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89 }
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90 if ((err = hash_descriptor[hash_idx].process(&md, salt, saltlen)) != CRYPT_OK) {
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91 goto __ERR;
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92 }
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93 if ((err = hash_descriptor[hash_idx].done(&md, hash)) != CRYPT_OK) {
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94 goto __ERR;
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95 }
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96
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97 /* generate DB = PS || 0x01 || salt, PS == modulus_len - saltlen - hLen - 2 zero bytes */
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98 for (x = 0; x < (modulus_len - saltlen - hLen - 2); x++) {
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99 DB[x] = 0x00;
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100 }
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101 DB[x++] = 0x01;
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102 for (y = 0; y < saltlen; y++) {
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103 DB[x++] = salt[y];
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104 }
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105
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106 /* generate mask of length modulus_len - hLen - 1 from hash */
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107 if ((err = pkcs_1_mgf1(hash, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) {
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108 goto __ERR;
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109 }
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110
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111 /* xor against DB */
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112 for (y = 0; y < (modulus_len - hLen - 1); y++) {
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113 DB[y] ^= mask[y];
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114 }
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115
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116 /* output is DB || hash || 0xBC */
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117 if (*outlen < modulus_len) {
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118 err = CRYPT_BUFFER_OVERFLOW;
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119 goto __ERR;
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120 }
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121
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122 /* DB */
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123 for (y = x = 0; x < modulus_len - hLen - 1; x++) {
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124 out[y++] = DB[x];
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125 }
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126 /* hash */
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127 for (x = 0; x < hLen; x++) {
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128 out[y++] = hash[x];
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129 }
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130 /* 0xBC */
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131 out[y] = 0xBC;
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132
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133 /* now clear the 8*modulus_len - modulus_bitlen most significant bits */
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134 out[0] &= 0xFF >> ((modulus_len<<3) - (modulus_bitlen-1));
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135
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136 /* store output size */
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137 *outlen = modulus_len;
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138 err = CRYPT_OK;
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139 __ERR:
3
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140 #ifdef CLEAN_STACK
143
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141 zeromem(DB, modulus_len);
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142 zeromem(mask, modulus_len);
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143 zeromem(salt, modulus_len);
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144 zeromem(hash, modulus_len);
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145 #endif
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146
143
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147 XFREE(hash);
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148 XFREE(salt);
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149 XFREE(mask);
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150 XFREE(DB);
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151
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152 return err;
3
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153 }
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154
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155 #endif /* PKCS_1 */