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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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15
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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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143
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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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143
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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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143
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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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143
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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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143
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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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143
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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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143
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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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143
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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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143
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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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143
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138 err = CRYPT_OK; |
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139 __ERR: |
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140 #ifdef CLEAN_STACK |
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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 |
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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; |
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153 } |
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154 |
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155 #endif /* PKCS_1 */ |
