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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, int hash_idx, |
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19 int prng_idx, prng_state *prng, |
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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[1024], mask[sizeof(DB)], salt[sizeof(DB)], hash[sizeof(DB)]; |
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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 /* check sizes */ |
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44 if ((saltlen > sizeof(salt)) || (modulus_len > sizeof(DB)) || (modulus_len < hLen + saltlen + 2)) { |
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45 return CRYPT_INVALID_ARG; |
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46 } |
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47 |
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48 /* generate random salt */ |
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49 if (saltlen > 0) { |
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50 if (prng_descriptor[prng_idx].read(salt, saltlen, prng) != saltlen) { |
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51 return CRYPT_ERROR_READPRNG; |
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52 } |
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53 } |
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54 |
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55 /* M = (eight) 0x00 || msghash || salt, hash = H(M) */ |
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56 hash_descriptor[hash_idx].init(&md); |
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57 zeromem(DB, 8); |
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58 if ((err = hash_descriptor[hash_idx].process(&md, DB, 8)) != CRYPT_OK) { |
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59 return err; |
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60 } |
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61 if ((err = hash_descriptor[hash_idx].process(&md, msghash, msghashlen)) != CRYPT_OK) { |
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62 return err; |
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63 } |
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64 if ((err = hash_descriptor[hash_idx].process(&md, salt, saltlen)) != CRYPT_OK) { |
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65 return err; |
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66 } |
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67 if ((err = hash_descriptor[hash_idx].done(&md, hash)) != CRYPT_OK) { |
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68 return err; |
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69 } |
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70 |
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71 /* generate DB = PS || 0x01 || salt, PS == modulus_len - saltlen - hLen - 2 zero bytes */ |
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72 for (x = 0; x < (modulus_len - saltlen - hLen - 2); x++) { |
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73 DB[x] = 0x00; |
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74 } |
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75 DB[x++] = 0x01; |
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76 for (y = 0; y < saltlen; y++) { |
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77 DB[x++] = salt[y]; |
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78 } |
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79 |
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80 /* generate mask of length modulus_len - hLen - 1 from hash */ |
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81 if ((err = pkcs_1_mgf1(hash, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) { |
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82 return err; |
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83 } |
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84 |
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85 /* xor against DB */ |
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86 for (y = 0; y < (modulus_len - hLen - 1); y++) { |
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87 DB[y] ^= mask[y]; |
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88 } |
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89 |
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90 /* output is DB || hash || 0xBC */ |
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91 if (*outlen < modulus_len) { |
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92 return CRYPT_BUFFER_OVERFLOW; |
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93 } |
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94 |
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95 /* DB */ |
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96 for (y = x = 0; x < modulus_len - hLen - 1; x++) { |
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97 out[y++] = DB[x]; |
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98 } |
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99 /* hash */ |
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100 for (x = 0; x < hLen; x++) { |
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101 out[y++] = hash[x]; |
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102 } |
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103 /* 0xBC */ |
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104 out[y] = 0xBC; |
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105 |
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106 /* now clear the 8*modulus_len - modulus_bitlen most significant bits */ |
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107 out[0] &= 0xFF >> ((modulus_len<<3) - modulus_bitlen); |
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108 |
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109 /* store output size */ |
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110 *outlen = modulus_len; |
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111 |
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112 #ifdef CLEAN_STACK |
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113 zeromem(DB, sizeof(DB)); |
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114 zeromem(mask, sizeof(mask)); |
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115 zeromem(salt, sizeof(salt)); |
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116 zeromem(hash, sizeof(hash)); |
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117 #endif |
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118 |
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119 return CRYPT_OK; |
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120 } |
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121 |
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122 #endif /* PKCS_1 */ |
