1 | /*
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2 | * Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.
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3 | *
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4 | * Licensed under the OpenSSL license (the "License"). You may not use
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5 | * this file except in compliance with the License. You can obtain a copy
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6 | * in the file LICENSE in the source distribution or at
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7 | * https://www.openssl.org/source/license.html
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8 | */
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9 |
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10 | #include <string.h>
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11 | #include <openssl/err.h>
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12 | #include <openssl/obj_mac.h>
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13 | #include <openssl/bn.h>
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14 | #include <openssl/rand.h>
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15 | #include <openssl/ec.h>
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16 | #include "ec_lcl.h"
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17 |
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18 | int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
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19 | unsigned char *sig, unsigned int *siglen,
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20 | const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
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21 | {
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22 | ECDSA_SIG *s;
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23 | RAND_seed(dgst, dlen);
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24 | s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
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25 | if (s == NULL) {
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26 | *siglen = 0;
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27 | return 0;
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28 | }
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29 | *siglen = i2d_ECDSA_SIG(s, &sig);
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30 | ECDSA_SIG_free(s);
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31 | return 1;
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32 | }
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33 |
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34 | static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
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35 | BIGNUM **kinvp, BIGNUM **rp,
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36 | const unsigned char *dgst, int dlen)
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37 | {
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38 | BN_CTX *ctx = NULL;
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39 | BIGNUM *k = NULL, *r = NULL, *X = NULL;
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40 | const BIGNUM *order;
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41 | EC_POINT *tmp_point = NULL;
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42 | const EC_GROUP *group;
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43 | int ret = 0;
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44 |
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45 | if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
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46 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
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47 | return 0;
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48 | }
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49 |
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50 | if (!EC_KEY_can_sign(eckey)) {
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51 | ECerr(EC_F_ECDSA_SIGN_SETUP, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
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52 | return 0;
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53 | }
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54 |
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55 | if (ctx_in == NULL) {
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56 | if ((ctx = BN_CTX_new()) == NULL) {
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57 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
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58 | return 0;
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59 | }
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60 | } else
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61 | ctx = ctx_in;
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62 |
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63 | k = BN_new(); /* this value is later returned in *kinvp */
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64 | r = BN_new(); /* this value is later returned in *rp */
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65 | X = BN_new();
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66 | if (k == NULL || r == NULL || X == NULL) {
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67 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
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68 | goto err;
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69 | }
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70 | if ((tmp_point = EC_POINT_new(group)) == NULL) {
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71 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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72 | goto err;
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73 | }
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74 | order = EC_GROUP_get0_order(group);
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75 | if (order == NULL) {
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76 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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77 | goto err;
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78 | }
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79 |
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80 | do {
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81 | /* get random k */
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82 | do
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83 | if (dgst != NULL) {
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84 | if (!BN_generate_dsa_nonce
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85 | (k, order, EC_KEY_get0_private_key(eckey), dgst, dlen,
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86 | ctx)) {
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87 | ECerr(EC_F_ECDSA_SIGN_SETUP,
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88 | EC_R_RANDOM_NUMBER_GENERATION_FAILED);
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89 | goto err;
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90 | }
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91 | } else {
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92 | if (!BN_rand_range(k, order)) {
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93 | ECerr(EC_F_ECDSA_SIGN_SETUP,
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94 | EC_R_RANDOM_NUMBER_GENERATION_FAILED);
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95 | goto err;
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96 | }
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97 | }
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98 | while (BN_is_zero(k));
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99 |
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100 | /*
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101 | * We do not want timing information to leak the length of k, so we
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102 | * compute G*k using an equivalent scalar of fixed bit-length.
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103 | */
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104 |
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105 | if (!BN_add(k, k, order))
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106 | goto err;
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107 | if (BN_num_bits(k) <= BN_num_bits(order))
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108 | if (!BN_add(k, k, order))
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109 | goto err;
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110 |
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111 | /* compute r the x-coordinate of generator * k */
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112 | if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
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113 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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114 | goto err;
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115 | }
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116 | if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
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117 | NID_X9_62_prime_field) {
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118 | if (!EC_POINT_get_affine_coordinates_GFp
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119 | (group, tmp_point, X, NULL, ctx)) {
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120 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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121 | goto err;
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122 | }
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123 | }
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124 | #ifndef OPENSSL_NO_EC2M
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125 | else { /* NID_X9_62_characteristic_two_field */
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126 |
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127 | if (!EC_POINT_get_affine_coordinates_GF2m(group,
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128 | tmp_point, X, NULL,
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129 | ctx)) {
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130 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
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131 | goto err;
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132 | }
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133 | }
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134 | #endif
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135 | if (!BN_nnmod(r, X, order, ctx)) {
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136 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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137 | goto err;
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138 | }
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139 | }
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140 | while (BN_is_zero(r));
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141 |
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142 | /* compute the inverse of k */
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143 | if (EC_GROUP_get_mont_data(group) != NULL) {
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144 | /*
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145 | * We want inverse in constant time, therefore we utilize the fact
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146 | * order must be prime and use Fermats Little Theorem instead.
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147 | */
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148 | if (!BN_set_word(X, 2)) {
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149 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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150 | goto err;
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151 | }
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152 | if (!BN_mod_sub(X, order, X, order, ctx)) {
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153 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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154 | goto err;
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155 | }
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156 | BN_set_flags(X, BN_FLG_CONSTTIME);
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157 | if (!BN_mod_exp_mont_consttime
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158 | (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
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159 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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160 | goto err;
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161 | }
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162 | } else {
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163 | if (!BN_mod_inverse(k, k, order, ctx)) {
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164 | ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
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165 | goto err;
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166 | }
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167 | }
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168 |
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169 | /* clear old values if necessary */
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170 | BN_clear_free(*rp);
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171 | BN_clear_free(*kinvp);
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172 | /* save the pre-computed values */
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173 | *rp = r;
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174 | *kinvp = k;
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175 | ret = 1;
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176 | err:
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177 | if (!ret) {
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178 | BN_clear_free(k);
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179 | BN_clear_free(r);
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180 | }
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181 | if (ctx != ctx_in)
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182 | BN_CTX_free(ctx);
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183 | EC_POINT_free(tmp_point);
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184 | BN_clear_free(X);
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185 | return (ret);
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186 | }
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187 |
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188 | int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
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189 | BIGNUM **rp)
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190 | {
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191 | return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
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192 | }
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193 |
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194 | ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
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195 | const BIGNUM *in_kinv, const BIGNUM *in_r,
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196 | EC_KEY *eckey)
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197 | {
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198 | int ok = 0, i;
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199 | BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL;
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200 | const BIGNUM *order, *ckinv;
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201 | BN_CTX *ctx = NULL;
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202 | const EC_GROUP *group;
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203 | ECDSA_SIG *ret;
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204 | const BIGNUM *priv_key;
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205 |
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206 | group = EC_KEY_get0_group(eckey);
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207 | priv_key = EC_KEY_get0_private_key(eckey);
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208 |
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209 | if (group == NULL || priv_key == NULL) {
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210 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
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211 | return NULL;
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212 | }
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213 |
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214 | if (!EC_KEY_can_sign(eckey)) {
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215 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
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216 | return NULL;
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217 | }
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218 |
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219 | ret = ECDSA_SIG_new();
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220 | if (ret == NULL) {
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221 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
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222 | return NULL;
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223 | }
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224 | ret->r = BN_new();
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225 | ret->s = BN_new();
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226 | if (ret->r == NULL || ret->s == NULL) {
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227 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
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228 | goto err;
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229 | }
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230 | s = ret->s;
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231 |
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232 | if ((ctx = BN_CTX_new()) == NULL ||
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233 | (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
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234 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
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235 | goto err;
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236 | }
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237 |
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238 | order = EC_GROUP_get0_order(group);
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239 | if (order == NULL) {
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240 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_EC_LIB);
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241 | goto err;
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242 | }
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243 | i = BN_num_bits(order);
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244 | /*
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245 | * Need to truncate digest if it is too long: first truncate whole bytes.
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246 | */
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247 | if (8 * dgst_len > i)
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248 | dgst_len = (i + 7) / 8;
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249 | if (!BN_bin2bn(dgst, dgst_len, m)) {
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250 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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251 | goto err;
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252 | }
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253 | /* If still too long truncate remaining bits with a shift */
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254 | if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
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255 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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256 | goto err;
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257 | }
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258 | do {
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259 | if (in_kinv == NULL || in_r == NULL) {
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260 | if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
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261 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_ECDSA_LIB);
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262 | goto err;
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263 | }
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264 | ckinv = kinv;
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265 | } else {
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266 | ckinv = in_kinv;
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267 | if (BN_copy(ret->r, in_r) == NULL) {
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268 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
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269 | goto err;
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270 | }
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271 | }
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272 |
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273 | if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
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274 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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275 | goto err;
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276 | }
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277 | if (!BN_mod_add_quick(s, tmp, m, order)) {
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278 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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279 | goto err;
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280 | }
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281 | if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
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282 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
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283 | goto err;
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284 | }
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285 | if (BN_is_zero(s)) {
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286 | /*
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287 | * if kinv and r have been supplied by the caller don't to
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288 | * generate new kinv and r values
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289 | */
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290 | if (in_kinv != NULL && in_r != NULL) {
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291 | ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
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292 | goto err;
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293 | }
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294 | } else
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295 | /* s != 0 => we have a valid signature */
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296 | break;
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297 | }
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298 | while (1);
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299 |
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300 | ok = 1;
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301 | err:
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302 | if (!ok) {
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303 | ECDSA_SIG_free(ret);
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304 | ret = NULL;
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305 | }
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306 | BN_CTX_free(ctx);
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307 | BN_clear_free(m);
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308 | BN_clear_free(tmp);
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309 | BN_clear_free(kinv);
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310 | return ret;
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311 | }
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312 |
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313 | /*-
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314 | * returns
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315 | * 1: correct signature
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316 | * 0: incorrect signature
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317 | * -1: error
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318 | */
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319 | int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
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320 | const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
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321 | {
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322 | ECDSA_SIG *s;
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323 | const unsigned char *p = sigbuf;
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324 | unsigned char *der = NULL;
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325 | int derlen = -1;
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326 | int ret = -1;
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327 |
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328 | s = ECDSA_SIG_new();
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329 | if (s == NULL)
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330 | return (ret);
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331 | if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
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332 | goto err;
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333 | /* Ensure signature uses DER and doesn't have trailing garbage */
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334 | derlen = i2d_ECDSA_SIG(s, &der);
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335 | if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
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336 | goto err;
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337 | ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
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338 | err:
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339 | OPENSSL_clear_free(der, derlen);
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340 | ECDSA_SIG_free(s);
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341 | return (ret);
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342 | }
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343 |
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344 | int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
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345 | const ECDSA_SIG *sig, EC_KEY *eckey)
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346 | {
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347 | int ret = -1, i;
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348 | BN_CTX *ctx;
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349 | const BIGNUM *order;
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350 | BIGNUM *u1, *u2, *m, *X;
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351 | EC_POINT *point = NULL;
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352 | const EC_GROUP *group;
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353 | const EC_POINT *pub_key;
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354 |
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355 | /* check input values */
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356 | if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
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357 | (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
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358 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
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359 | return -1;
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360 | }
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361 |
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362 | if (!EC_KEY_can_sign(eckey)) {
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363 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
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364 | return -1;
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365 | }
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366 |
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367 | ctx = BN_CTX_new();
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368 | if (ctx == NULL) {
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369 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
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370 | return -1;
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371 | }
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372 | BN_CTX_start(ctx);
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373 | u1 = BN_CTX_get(ctx);
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374 | u2 = BN_CTX_get(ctx);
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375 | m = BN_CTX_get(ctx);
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376 | X = BN_CTX_get(ctx);
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377 | if (X == NULL) {
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378 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
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379 | goto err;
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380 | }
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381 |
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382 | order = EC_GROUP_get0_order(group);
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383 | if (order == NULL) {
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384 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
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385 | goto err;
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386 | }
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387 |
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388 | if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
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389 | BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
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390 | BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
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391 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
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392 | ret = 0; /* signature is invalid */
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393 | goto err;
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394 | }
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395 | /* calculate tmp1 = inv(S) mod order */
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396 | if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
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397 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
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398 | goto err;
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399 | }
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400 | /* digest -> m */
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401 | i = BN_num_bits(order);
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402 | /*
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403 | * Need to truncate digest if it is too long: first truncate whole bytes.
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404 | */
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405 | if (8 * dgst_len > i)
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406 | dgst_len = (i + 7) / 8;
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407 | if (!BN_bin2bn(dgst, dgst_len, m)) {
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408 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
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409 | goto err;
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410 | }
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411 | /* If still too long truncate remaining bits with a shift */
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412 | if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
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413 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
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414 | goto err;
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415 | }
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416 | /* u1 = m * tmp mod order */
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417 | if (!BN_mod_mul(u1, m, u2, order, ctx)) {
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418 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
---|
419 | goto err;
|
---|
420 | }
|
---|
421 | /* u2 = r * w mod q */
|
---|
422 | if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
|
---|
423 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
---|
424 | goto err;
|
---|
425 | }
|
---|
426 |
|
---|
427 | if ((point = EC_POINT_new(group)) == NULL) {
|
---|
428 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
|
---|
429 | goto err;
|
---|
430 | }
|
---|
431 | if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
|
---|
432 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
|
---|
433 | goto err;
|
---|
434 | }
|
---|
435 | if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
|
---|
436 | NID_X9_62_prime_field) {
|
---|
437 | if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
|
---|
438 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
|
---|
439 | goto err;
|
---|
440 | }
|
---|
441 | }
|
---|
442 | #ifndef OPENSSL_NO_EC2M
|
---|
443 | else { /* NID_X9_62_characteristic_two_field */
|
---|
444 |
|
---|
445 | if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
|
---|
446 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
|
---|
447 | goto err;
|
---|
448 | }
|
---|
449 | }
|
---|
450 | #endif
|
---|
451 | if (!BN_nnmod(u1, X, order, ctx)) {
|
---|
452 | ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
|
---|
453 | goto err;
|
---|
454 | }
|
---|
455 | /* if the signature is correct u1 is equal to sig->r */
|
---|
456 | ret = (BN_ucmp(u1, sig->r) == 0);
|
---|
457 | err:
|
---|
458 | BN_CTX_end(ctx);
|
---|
459 | BN_CTX_free(ctx);
|
---|
460 | EC_POINT_free(point);
|
---|
461 | return ret;
|
---|
462 | }
|
---|