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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 |
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12 /* Implementation of Fortuna by Tom St Denis |
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13 |
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14 We deviate slightly here for reasons of simplicity [and to fit in the API]. First all "sources" |
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15 in the AddEntropy function are fixed to 0. Second since no reliable timer is provided |
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16 we reseed automatically when len(pool0) >= 64 or every FORTUNA_WD calls to the read function */ |
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17 |
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18 #include "mycrypt.h" |
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19 |
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20 #ifdef FORTUNA |
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21 |
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22 /* requries SHA256 and AES */ |
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23 #if !(defined(RIJNDAEL) && defined(SHA256)) |
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24 #error FORTUNA requires SHA256 and RIJNDAEL (AES) |
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25 #endif |
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26 |
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27 #ifndef FORTUNA_POOLS |
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28 #warning FORTUNA_POOLS was not previously defined (old headers?) |
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29 #define FORTUNA_POOLS 32 |
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30 #endif |
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31 |
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32 #if FORTUNA_POOLS < 4 || FORTUNA_POOLS > 32 |
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33 #error FORTUNA_POOLS must be in [4..32] |
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34 #endif |
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35 |
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36 const struct _prng_descriptor fortuna_desc = { |
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37 "fortuna", 1024, |
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38 &fortuna_start, |
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39 &fortuna_add_entropy, |
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40 &fortuna_ready, |
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41 &fortuna_read, |
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42 &fortuna_done, |
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43 &fortuna_export, |
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44 &fortuna_import, |
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45 &fortuna_test |
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46 }; |
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47 |
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48 /* update the IV */ |
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49 static void fortuna_update_iv(prng_state *prng) |
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50 { |
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51 int x; |
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52 unsigned char *IV; |
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53 /* update IV */ |
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54 IV = prng->fortuna.IV; |
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55 for (x = 0; x < 16; x++) { |
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56 IV[x] = (IV[x] + 1) & 255; |
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57 if (IV[x] != 0) break; |
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58 } |
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59 } |
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60 |
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61 /* reseed the PRNG */ |
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62 static int fortuna_reseed(prng_state *prng) |
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63 { |
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64 unsigned char tmp[MAXBLOCKSIZE]; |
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65 hash_state md; |
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66 int err, x; |
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67 |
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68 ++prng->fortuna.reset_cnt; |
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69 |
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70 /* new K == SHA256(K || s) where s == SHA256(P0) || SHA256(P1) ... */ |
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71 sha256_init(&md); |
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72 if ((err = sha256_process(&md, prng->fortuna.K, 32)) != CRYPT_OK) { |
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73 return err; |
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74 } |
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75 |
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76 for (x = 0; x < FORTUNA_POOLS; x++) { |
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77 if (x == 0 || ((prng->fortuna.reset_cnt >> (x-1)) & 1) == 0) { |
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78 /* terminate this hash */ |
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79 if ((err = sha256_done(&prng->fortuna.pool[x], tmp)) != CRYPT_OK) { |
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80 return err; |
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81 } |
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82 /* add it to the string */ |
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83 if ((err = sha256_process(&md, tmp, 32)) != CRYPT_OK) { |
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84 return err; |
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85 } |
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86 /* reset this pool */ |
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87 sha256_init(&prng->fortuna.pool[x]); |
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88 } else { |
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89 break; |
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90 } |
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91 } |
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92 |
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93 /* finish key */ |
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94 if ((err = sha256_done(&md, prng->fortuna.K)) != CRYPT_OK) { |
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95 return err; |
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96 } |
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97 if ((err = rijndael_setup(prng->fortuna.K, 32, 0, &prng->fortuna.skey)) != CRYPT_OK) { |
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98 return err; |
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99 } |
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100 fortuna_update_iv(prng); |
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101 |
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102 /* reset pool len */ |
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103 prng->fortuna.pool0_len = 0; |
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104 prng->fortuna.wd = 0; |
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105 |
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106 |
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107 #ifdef CLEAN_STACK |
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108 zeromem(&md, sizeof(md)); |
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109 zeromem(tmp, sizeof(tmp)); |
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110 #endif |
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111 |
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112 return CRYPT_OK; |
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113 } |
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114 |
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115 int fortuna_start(prng_state *prng) |
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116 { |
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117 int err, x; |
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118 |
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119 _ARGCHK(prng != NULL); |
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120 |
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121 /* initialize the pools */ |
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122 for (x = 0; x < FORTUNA_POOLS; x++) { |
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123 sha256_init(&prng->fortuna.pool[x]); |
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124 } |
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125 prng->fortuna.pool_idx = prng->fortuna.pool0_len = prng->fortuna.reset_cnt = |
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126 prng->fortuna.wd = 0; |
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127 |
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128 /* reset bufs */ |
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129 zeromem(prng->fortuna.K, 32); |
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130 if ((err = rijndael_setup(prng->fortuna.K, 32, 0, &prng->fortuna.skey)) != CRYPT_OK) { |
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131 return err; |
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132 } |
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133 zeromem(prng->fortuna.IV, 16); |
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134 |
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135 return CRYPT_OK; |
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136 } |
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137 |
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138 int fortuna_add_entropy(const unsigned char *buf, unsigned long len, prng_state *prng) |
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139 { |
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140 unsigned char tmp[2]; |
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141 int err; |
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142 |
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143 _ARGCHK(buf != NULL); |
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144 _ARGCHK(prng != NULL); |
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145 |
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146 /* ensure len <= 32 */ |
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147 if (len > 32) { |
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148 return CRYPT_INVALID_ARG; |
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149 } |
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150 |
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151 /* add s || length(buf) || buf to pool[pool_idx] */ |
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152 tmp[0] = 0; |
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153 tmp[1] = len; |
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154 if ((err = sha256_process(&prng->fortuna.pool[prng->fortuna.pool_idx], tmp, 2)) != CRYPT_OK) { |
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155 return err; |
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156 } |
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157 if ((err = sha256_process(&prng->fortuna.pool[prng->fortuna.pool_idx], buf, len)) != CRYPT_OK) { |
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158 return err; |
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159 } |
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160 if (prng->fortuna.pool_idx == 0) { |
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161 prng->fortuna.pool0_len += len; |
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162 } |
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163 if (++(prng->fortuna.pool_idx) == FORTUNA_POOLS) { |
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164 prng->fortuna.pool_idx = 0; |
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165 } |
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166 |
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167 return CRYPT_OK; |
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168 } |
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169 |
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170 int fortuna_ready(prng_state *prng) |
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171 { |
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172 return fortuna_reseed(prng); |
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173 } |
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174 |
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175 unsigned long fortuna_read(unsigned char *dst, unsigned long len, prng_state *prng) |
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176 { |
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177 unsigned char tmp[16]; |
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178 int err; |
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179 unsigned long tlen; |
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180 |
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181 _ARGCHK(dst != NULL); |
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182 _ARGCHK(prng != NULL); |
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183 |
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184 /* do we have to reseed? */ |
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185 if (++prng->fortuna.wd == FORTUNA_WD || prng->fortuna.pool0_len >= 64) { |
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186 if ((err = fortuna_reseed(prng)) != CRYPT_OK) { |
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187 return 0; |
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188 } |
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189 } |
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190 |
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191 /* now generate the blocks required */ |
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192 tlen = len; |
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193 |
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194 /* handle whole blocks without the extra memcpy */ |
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195 while (len >= 16) { |
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196 /* encrypt the IV and store it */ |
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197 rijndael_ecb_encrypt(prng->fortuna.IV, dst, &prng->fortuna.skey); |
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198 dst += 16; |
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199 len -= 16; |
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200 fortuna_update_iv(prng); |
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201 } |
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202 |
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203 /* left over bytes? */ |
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204 if (len > 0) { |
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205 rijndael_ecb_encrypt(prng->fortuna.IV, tmp, &prng->fortuna.skey); |
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206 XMEMCPY(dst, tmp, len); |
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207 fortuna_update_iv(prng); |
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208 } |
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209 |
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210 /* generate new key */ |
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211 rijndael_ecb_encrypt(prng->fortuna.IV, prng->fortuna.K , &prng->fortuna.skey); fortuna_update_iv(prng); |
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212 rijndael_ecb_encrypt(prng->fortuna.IV, prng->fortuna.K+16, &prng->fortuna.skey); fortuna_update_iv(prng); |
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213 if ((err = rijndael_setup(prng->fortuna.K, 32, 0, &prng->fortuna.skey)) != CRYPT_OK) { |
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214 return 0; |
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215 } |
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216 |
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217 #ifdef CLEAN_STACK |
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218 zeromem(tmp, sizeof(tmp)); |
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219 #endif |
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220 return tlen; |
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221 } |
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222 |
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223 int fortuna_done(prng_state *prng) |
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224 { |
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225 int err, x; |
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226 unsigned char tmp[32]; |
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227 |
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228 _ARGCHK(prng != NULL); |
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229 |
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230 /* terminate all the hashes */ |
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231 for (x = 0; x < FORTUNA_POOLS; x++) { |
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232 if ((err = sha256_done(&(prng->fortuna.pool[x]), tmp)) != CRYPT_OK) { |
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233 return err; |
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234 } |
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235 } |
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236 /* call cipher done when we invent one ;-) */ |
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237 |
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238 #ifdef CLEAN_STACK |
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239 zeromem(tmp, sizeof(tmp)); |
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240 #endif |
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241 |
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242 return CRYPT_OK; |
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243 } |
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244 |
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245 int fortuna_export(unsigned char *out, unsigned long *outlen, prng_state *prng) |
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246 { |
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247 int x, err; |
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248 hash_state *md; |
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249 |
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250 _ARGCHK(out != NULL); |
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251 _ARGCHK(outlen != NULL); |
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252 _ARGCHK(prng != NULL); |
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253 |
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254 /* we'll write bytes for s&g's */ |
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255 if (*outlen < 32*FORTUNA_POOLS) { |
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256 return CRYPT_BUFFER_OVERFLOW; |
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257 } |
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258 |
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259 md = XMALLOC(sizeof(hash_state)); |
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260 if (md == NULL) { |
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261 return CRYPT_MEM; |
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262 } |
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263 |
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264 /* to emit the state we copy each pool, terminate it then hash it again so |
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265 * an attacker who sees the state can't determine the current state of the PRNG |
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266 */ |
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267 for (x = 0; x < FORTUNA_POOLS; x++) { |
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268 /* copy the PRNG */ |
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269 XMEMCPY(md, &(prng->fortuna.pool[x]), sizeof(*md)); |
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270 |
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271 /* terminate it */ |
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272 if ((err = sha256_done(md, out+x*32)) != CRYPT_OK) { |
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273 goto __ERR; |
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274 } |
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275 |
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276 /* now hash it */ |
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277 if ((err = sha256_init(md)) != CRYPT_OK) { |
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278 goto __ERR; |
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279 } |
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280 if ((err = sha256_process(md, out+x*32, 32)) != CRYPT_OK) { |
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281 goto __ERR; |
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282 } |
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283 if ((err = sha256_done(md, out+x*32)) != CRYPT_OK) { |
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284 goto __ERR; |
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285 } |
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286 } |
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287 *outlen = 32*FORTUNA_POOLS; |
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288 err = CRYPT_OK; |
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289 |
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290 __ERR: |
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291 #ifdef CLEAN_STACK |
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292 zeromem(md, sizeof(*md)); |
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293 #endif |
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294 XFREE(md); |
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295 return err; |
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296 } |
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297 |
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298 int fortuna_import(const unsigned char *in, unsigned long inlen, prng_state *prng) |
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299 { |
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300 int err, x; |
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301 |
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302 _ARGCHK(in != NULL); |
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303 _ARGCHK(prng != NULL); |
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304 |
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305 if (inlen != 32*FORTUNA_POOLS) { |
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306 return CRYPT_INVALID_ARG; |
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307 } |
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308 |
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309 if ((err = fortuna_start(prng)) != CRYPT_OK) { |
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310 return err; |
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311 } |
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312 for (x = 0; x < FORTUNA_POOLS; x++) { |
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313 if ((err = fortuna_add_entropy(in+x*32, 32, prng)) != CRYPT_OK) { |
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314 return err; |
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315 } |
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316 } |
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317 return err; |
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318 } |
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319 |
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320 int fortuna_test(void) |
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321 { |
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322 #ifndef LTC_TEST |
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323 return CRYPT_NOP; |
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324 #else |
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325 int err; |
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326 |
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327 if ((err = sha256_test()) != CRYPT_OK) { |
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328 return err; |
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329 } |
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330 return rijndael_test(); |
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331 #endif |
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332 } |
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333 |
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334 #endif |
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335 |
