1 | /* dsa.c
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2 | *
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3 | * Copyright (C) 2006-2015 wolfSSL Inc.
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4 | *
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5 | * This file is part of wolfSSL. (formerly known as CyaSSL)
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6 | *
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7 | * wolfSSL is free software; you can redistribute it and/or modify
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8 | * it under the terms of the GNU General Public License as published by
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9 | * the Free Software Foundation; either version 2 of the License, or
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10 | * (at your option) any later version.
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11 | *
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12 | * wolfSSL is distributed in the hope that it will be useful,
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 | * GNU General Public License for more details.
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16 | *
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17 | * You should have received a copy of the GNU General Public License
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18 | * along with this program; if not, write to the Free Software
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19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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20 | */
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21 |
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22 | #ifdef HAVE_CONFIG_H
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23 | #include <config.h>
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24 | #endif
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25 |
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26 | #include <wolfssl/wolfcrypt/settings.h>
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27 |
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28 | #ifndef NO_DSA
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29 |
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30 | #include <wolfssl/wolfcrypt/random.h>
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31 | #include <wolfssl/wolfcrypt/integer.h>
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32 | #include <wolfssl/wolfcrypt/error-crypt.h>
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33 | #include <wolfssl/wolfcrypt/logging.h>
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34 | #include <wolfssl/wolfcrypt/sha.h>
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35 | #include <wolfssl/wolfcrypt/dsa.h>
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36 |
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37 |
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38 | enum {
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39 | DSA_HALF_SIZE = 20, /* r and s size */
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40 | DSA_SIG_SIZE = 40 /* signature size */
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41 | };
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42 |
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43 |
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44 | #ifdef min
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45 | #define WOLFSSL_HAVE_MIN
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46 | #endif
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47 | #ifndef WOLFSSL_HAVE_MIN
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48 | #define WOLFSSL_HAVE_MIN
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49 |
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50 | static INLINE word32 min(word32 a, word32 b)
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51 | {
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52 | return a > b ? b : a;
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53 | }
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54 |
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55 | #endif /* WOLFSSL_HAVE_MIN */
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56 |
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57 |
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58 | void wc_InitDsaKey(DsaKey* key)
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59 | {
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60 | key->type = -1; /* haven't decided yet */
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61 |
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62 | /* TomsFastMath doesn't use memory allocation */
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63 | #ifndef USE_FAST_MATH
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64 | key->p.dp = 0; /* public alloc parts */
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65 | key->q.dp = 0;
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66 | key->g.dp = 0;
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67 | key->y.dp = 0;
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68 |
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69 | key->x.dp = 0; /* private alloc parts */
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70 | #endif
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71 | }
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72 |
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73 |
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74 | void wc_FreeDsaKey(DsaKey* key)
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75 | {
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76 | (void)key;
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77 | /* TomsFastMath doesn't use memory allocation */
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78 | #ifndef USE_FAST_MATH
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79 | if (key->type == DSA_PRIVATE)
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80 | mp_clear(&key->x);
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81 | mp_clear(&key->y);
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82 | mp_clear(&key->g);
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83 | mp_clear(&key->q);
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84 | mp_clear(&key->p);
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85 | #endif
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86 | }
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87 |
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88 | #ifdef WOLFSSL_KEY_GEN
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89 |
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90 | int wc_MakeDsaKey(WC_RNG *rng, DsaKey *dsa)
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91 | {
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92 | unsigned char *buf;
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93 | int qsize, err;
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94 |
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95 | if (rng == NULL || dsa == NULL)
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96 | return BAD_FUNC_ARG;
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97 |
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98 | qsize = mp_unsigned_bin_size(&dsa->q);
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99 | if (qsize == 0)
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100 | return BAD_FUNC_ARG;
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101 |
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102 | /* allocate ram */
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103 | buf = (unsigned char *)XMALLOC(qsize, NULL,
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104 | DYNAMIC_TYPE_TMP_BUFFER);
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105 | if (buf == NULL)
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106 | return MEMORY_E;
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107 |
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108 | if (mp_init(&dsa->x) != MP_OKAY) {
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109 | XFREE(buf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
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110 | return MP_INIT_E;
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111 | }
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112 |
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113 | do {
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114 | /* make a random exponent mod q */
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115 | err = wc_RNG_GenerateBlock(rng, buf, qsize);
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116 | if (err != MP_OKAY) {
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117 | mp_clear(&dsa->x);
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118 | XFREE(buf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
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119 | return err;
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120 | }
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121 |
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122 | err = mp_read_unsigned_bin(&dsa->x, buf, qsize);
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123 | if (err != MP_OKAY) {
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124 | mp_clear(&dsa->x);
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125 | XFREE(buf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
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126 | return err;
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127 | }
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128 | } while (mp_cmp_d(&dsa->x, 1) != MP_GT);
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129 |
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130 | XFREE(buf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
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131 |
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132 | if (mp_init(&dsa->y) != MP_OKAY) {
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133 | mp_clear(&dsa->x);
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134 | return MP_INIT_E;
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135 | }
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136 |
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137 | /* public key : y = g^x mod p */
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138 | err = mp_exptmod(&dsa->g, &dsa->x, &dsa->p, &dsa->y);
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139 | if (err != MP_OKAY) {
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140 | mp_clear(&dsa->x);
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141 | mp_clear(&dsa->y);
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142 | return err;
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143 | }
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144 |
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145 | dsa->type = DSA_PRIVATE;
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146 |
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147 | return MP_OKAY;
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148 | }
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149 |
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150 | /* modulus_size in bits */
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151 | int wc_MakeDsaParameters(WC_RNG *rng, int modulus_size, DsaKey *dsa)
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152 | {
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153 | mp_int tmp, tmp2;
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154 | int err, msize, qsize,
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155 | loop_check_prime = 0,
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156 | check_prime = MP_NO;
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157 | unsigned char *buf;
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158 |
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159 | if (rng == NULL || dsa == NULL)
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160 | return BAD_FUNC_ARG;
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161 |
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162 | /* set group size in bytes from modulus size
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163 | * FIPS 186-4 defines valid values (1024, 160) (2048, 256) (3072, 256)
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164 | */
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165 | switch (modulus_size) {
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166 | case 1024:
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167 | qsize = 20;
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168 | break;
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169 | case 2048:
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170 | case 3072:
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171 | qsize = 32;
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172 | break;
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173 | default:
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174 | return BAD_FUNC_ARG;
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175 | break;
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176 | }
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177 |
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178 | /* modulus size in bytes */
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179 | msize = modulus_size / 8;
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180 |
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181 | /* allocate ram */
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182 | buf = (unsigned char *)XMALLOC(msize - qsize,
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183 | NULL, DYNAMIC_TYPE_TMP_BUFFER);
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184 | if (buf == NULL) {
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185 | return MEMORY_E;
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186 | }
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187 |
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188 | /* make a random string that will be multplied against q */
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189 | err = wc_RNG_GenerateBlock(rng, buf, msize - qsize);
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190 | if (err != MP_OKAY) {
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191 | XFREE(buf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
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192 | return err;
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193 | }
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194 |
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195 | /* force magnitude */
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196 | buf[0] |= 0xC0;
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197 |
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198 | /* force even */
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199 | buf[msize - qsize - 1] &= ~1;
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200 |
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201 | if (mp_init_multi(&tmp2, &dsa->p, &dsa->q, 0, 0, 0) != MP_OKAY) {
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202 | mp_clear(&dsa->q);
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203 | XFREE(buf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
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204 | return MP_INIT_E;
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205 | }
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206 |
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207 | err = mp_read_unsigned_bin(&tmp2, buf, msize - qsize);
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208 | if (err != MP_OKAY) {
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209 | mp_clear(&dsa->q);
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210 | mp_clear(&dsa->p);
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211 | mp_clear(&tmp2);
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212 | XFREE(buf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
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213 | return err;
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214 | }
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215 | XFREE(buf, NULL, DYNAMIC_TYPE_TMP_BUFFER);
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216 |
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217 | /* make our prime q */
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218 | err = mp_rand_prime(&dsa->q, qsize, rng, NULL);
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219 | if (err != MP_OKAY) {
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220 | mp_clear(&dsa->q);
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221 | mp_clear(&dsa->p);
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222 | mp_clear(&tmp2);
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223 | return err;
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224 | }
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225 |
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226 | /* p = random * q */
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227 | err = mp_mul(&dsa->q, &tmp2, &dsa->p);
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228 | if (err != MP_OKAY) {
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229 | mp_clear(&dsa->q);
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230 | mp_clear(&dsa->p);
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231 | mp_clear(&tmp2);
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232 | return err;
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233 | }
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234 |
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235 | /* p = random * q + 1, so q is a prime divisor of p-1 */
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236 | err = mp_add_d(&dsa->p, 1, &dsa->p);
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237 | if (err != MP_OKAY) {
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238 | mp_clear(&dsa->q);
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239 | mp_clear(&dsa->p);
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240 | mp_clear(&tmp2);
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241 | return err;
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242 | }
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243 |
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244 | if (mp_init(&tmp) != MP_OKAY) {
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245 | mp_clear(&dsa->q);
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246 | mp_clear(&dsa->p);
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247 | mp_clear(&tmp2);
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248 | return MP_INIT_E;
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249 | }
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250 |
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251 | /* tmp = 2q */
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252 | err = mp_add(&dsa->q, &dsa->q, &tmp);
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253 | if (err != MP_OKAY) {
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254 | mp_clear(&dsa->q);
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255 | mp_clear(&dsa->p);
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256 | mp_clear(&tmp);
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257 | mp_clear(&tmp2);
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258 | return err;
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259 | }
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260 |
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261 | /* loop until p is prime */
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262 | while (check_prime == MP_NO) {
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263 | err = mp_prime_is_prime(&dsa->p, 8, &check_prime);
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264 | if (err != MP_OKAY) {
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265 | mp_clear(&dsa->q);
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266 | mp_clear(&dsa->p);
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267 | mp_clear(&tmp);
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268 | mp_clear(&tmp2);
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269 | return err;
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270 | }
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271 |
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272 | if (check_prime != MP_YES) {
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273 | /* p += 2q */
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274 | err = mp_add(&tmp, &dsa->p, &dsa->p);
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275 | if (err != MP_OKAY) {
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276 | mp_clear(&dsa->q);
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277 | mp_clear(&dsa->p);
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278 | mp_clear(&tmp);
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279 | mp_clear(&tmp2);
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280 | return err;
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281 | }
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282 |
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283 | loop_check_prime++;
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284 | }
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285 | }
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286 |
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287 | /* tmp2 += (2*loop_check_prime)
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288 | * to have p = (q * tmp2) + 1 prime
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289 | */
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290 | if (loop_check_prime) {
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291 | err = mp_add_d(&tmp2, 2*loop_check_prime, &tmp2);
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292 | if (err != MP_OKAY) {
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293 | mp_clear(&dsa->q);
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294 | mp_clear(&dsa->p);
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295 | mp_clear(&tmp);
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296 | mp_clear(&tmp2);
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297 | return err;
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298 | }
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299 | }
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300 |
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301 | if (mp_init(&dsa->g) != MP_OKAY) {
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302 | mp_clear(&dsa->q);
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303 | mp_clear(&dsa->p);
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304 | mp_clear(&tmp);
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305 | mp_clear(&tmp2);
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306 | return MP_INIT_E;
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307 | }
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308 |
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309 | /* find a value g for which g^tmp2 != 1 */
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310 | mp_set(&dsa->g, 1);
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311 |
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312 | do {
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313 | err = mp_add_d(&dsa->g, 1, &dsa->g);
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314 | if (err != MP_OKAY) {
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315 | mp_clear(&dsa->q);
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316 | mp_clear(&dsa->p);
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317 | mp_clear(&dsa->g);
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318 | mp_clear(&tmp);
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319 | mp_clear(&tmp2);
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320 | return err;
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321 | }
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322 |
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323 | err = mp_exptmod(&dsa->g, &tmp2, &dsa->p, &tmp);
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324 | if (err != MP_OKAY) {
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325 | mp_clear(&dsa->q);
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326 | mp_clear(&dsa->p);
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327 | mp_clear(&dsa->g);
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328 | mp_clear(&tmp);
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329 | mp_clear(&tmp2);
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330 | return err;
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331 | }
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332 |
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333 | } while (mp_cmp_d(&tmp, 1) == MP_EQ);
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334 |
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335 | /* at this point tmp generates a group of order q mod p */
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336 | mp_exch(&tmp, &dsa->g);
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337 |
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338 | mp_clear(&tmp);
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339 | mp_clear(&tmp2);
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340 |
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341 | return MP_OKAY;
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342 | }
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343 | #endif /* WOLFSSL_KEY_GEN */
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344 |
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345 |
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346 | int wc_DsaSign(const byte* digest, byte* out, DsaKey* key, WC_RNG* rng)
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347 | {
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348 | mp_int k, kInv, r, s, H;
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349 | int ret, sz;
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350 | byte buffer[DSA_HALF_SIZE];
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351 |
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352 | sz = min(sizeof(buffer), mp_unsigned_bin_size(&key->q));
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353 |
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354 | /* generate k */
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355 | ret = wc_RNG_GenerateBlock(rng, buffer, sz);
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356 | if (ret != 0)
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357 | return ret;
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358 |
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359 | buffer[0] |= 0x0C;
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360 |
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361 | if (mp_init_multi(&k, &kInv, &r, &s, &H, 0) != MP_OKAY)
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362 | return MP_INIT_E;
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363 |
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364 | if (mp_read_unsigned_bin(&k, buffer, sz) != MP_OKAY)
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365 | ret = MP_READ_E;
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366 |
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367 | if (ret == 0 && mp_cmp_d(&k, 1) != MP_GT)
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368 | ret = MP_CMP_E;
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369 |
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370 | /* inverse k mod q */
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371 | if (ret == 0 && mp_invmod(&k, &key->q, &kInv) != MP_OKAY)
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372 | ret = MP_INVMOD_E;
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373 |
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374 | /* generate r, r = (g exp k mod p) mod q */
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375 | if (ret == 0 && mp_exptmod(&key->g, &k, &key->p, &r) != MP_OKAY)
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376 | ret = MP_EXPTMOD_E;
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377 |
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378 | if (ret == 0 && mp_mod(&r, &key->q, &r) != MP_OKAY)
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379 | ret = MP_MOD_E;
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380 |
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381 | /* generate H from sha digest */
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382 | if (ret == 0 && mp_read_unsigned_bin(&H, digest,SHA_DIGEST_SIZE) != MP_OKAY)
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383 | ret = MP_READ_E;
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384 |
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385 | /* generate s, s = (kInv * (H + x*r)) % q */
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386 | if (ret == 0 && mp_mul(&key->x, &r, &s) != MP_OKAY)
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387 | ret = MP_MUL_E;
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388 |
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389 | if (ret == 0 && mp_add(&s, &H, &s) != MP_OKAY)
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390 | ret = MP_ADD_E;
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391 |
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392 | if (ret == 0 && mp_mulmod(&s, &kInv, &key->q, &s) != MP_OKAY)
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393 | ret = MP_MULMOD_E;
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394 |
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395 | /* write out */
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396 | if (ret == 0) {
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397 | int rSz = mp_unsigned_bin_size(&r);
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398 | int sSz = mp_unsigned_bin_size(&s);
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399 |
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400 | if (rSz == DSA_HALF_SIZE - 1) {
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401 | out[0] = 0;
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402 | out++;
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403 | }
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404 |
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405 | if (mp_to_unsigned_bin(&r, out) != MP_OKAY)
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406 | ret = MP_TO_E;
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407 | else {
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408 | if (sSz == DSA_HALF_SIZE - 1) {
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409 | out[rSz] = 0;
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410 | out++;
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411 | }
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412 | ret = mp_to_unsigned_bin(&s, out + rSz);
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413 | }
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414 | }
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415 |
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416 | mp_clear(&H);
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417 | mp_clear(&s);
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418 | mp_clear(&r);
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419 | mp_clear(&kInv);
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420 | mp_clear(&k);
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421 |
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422 | return ret;
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423 | }
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424 |
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425 |
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426 | int wc_DsaVerify(const byte* digest, const byte* sig, DsaKey* key, int* answer)
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427 | {
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428 | mp_int w, u1, u2, v, r, s;
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429 | int ret = 0;
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430 |
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431 | if (mp_init_multi(&w, &u1, &u2, &v, &r, &s) != MP_OKAY)
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432 | return MP_INIT_E;
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433 |
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434 | /* set r and s from signature */
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435 | if (mp_read_unsigned_bin(&r, sig, DSA_HALF_SIZE) != MP_OKAY ||
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436 | mp_read_unsigned_bin(&s, sig + DSA_HALF_SIZE, DSA_HALF_SIZE) != MP_OKAY)
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437 | ret = MP_READ_E;
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438 |
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439 | /* sanity checks */
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440 | if (ret == 0) {
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441 | if (mp_iszero(&r) == MP_YES || mp_iszero(&s) == MP_YES ||
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442 | mp_cmp(&r, &key->q) != MP_LT || mp_cmp(&s, &key->q) != MP_LT) {
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443 | ret = MP_ZERO_E;
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444 | }
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445 | }
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446 |
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447 | /* put H into u1 from sha digest */
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448 | if (ret == 0 && mp_read_unsigned_bin(&u1,digest,SHA_DIGEST_SIZE) != MP_OKAY)
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449 | ret = MP_READ_E;
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450 |
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451 | /* w = s invmod q */
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452 | if (ret == 0 && mp_invmod(&s, &key->q, &w) != MP_OKAY)
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453 | ret = MP_INVMOD_E;
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454 |
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455 | /* u1 = (H * w) % q */
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456 | if (ret == 0 && mp_mulmod(&u1, &w, &key->q, &u1) != MP_OKAY)
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457 | ret = MP_MULMOD_E;
|
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458 |
|
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459 | /* u2 = (r * w) % q */
|
---|
460 | if (ret == 0 && mp_mulmod(&r, &w, &key->q, &u2) != MP_OKAY)
|
---|
461 | ret = MP_MULMOD_E;
|
---|
462 |
|
---|
463 | /* verify v = ((g^u1 * y^u2) mod p) mod q */
|
---|
464 | if (ret == 0 && mp_exptmod(&key->g, &u1, &key->p, &u1) != MP_OKAY)
|
---|
465 | ret = MP_EXPTMOD_E;
|
---|
466 |
|
---|
467 | if (ret == 0 && mp_exptmod(&key->y, &u2, &key->p, &u2) != MP_OKAY)
|
---|
468 | ret = MP_EXPTMOD_E;
|
---|
469 |
|
---|
470 | if (ret == 0 && mp_mulmod(&u1, &u2, &key->p, &v) != MP_OKAY)
|
---|
471 | ret = MP_MULMOD_E;
|
---|
472 |
|
---|
473 | if (ret == 0 && mp_mod(&v, &key->q, &v) != MP_OKAY)
|
---|
474 | ret = MP_MULMOD_E;
|
---|
475 |
|
---|
476 | /* do they match */
|
---|
477 | if (ret == 0 && mp_cmp(&r, &v) == MP_EQ)
|
---|
478 | *answer = 1;
|
---|
479 | else
|
---|
480 | *answer = 0;
|
---|
481 |
|
---|
482 | mp_clear(&s);
|
---|
483 | mp_clear(&r);
|
---|
484 | mp_clear(&u1);
|
---|
485 | mp_clear(&u2);
|
---|
486 | mp_clear(&w);
|
---|
487 | mp_clear(&v);
|
---|
488 |
|
---|
489 | return ret;
|
---|
490 | }
|
---|
491 |
|
---|
492 |
|
---|
493 | #endif /* NO_DSA */
|
---|
494 |
|
---|