1 | /*
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2 | * Copyright 1995-2016 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 <stdio.h>
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11 | #include "internal/cryptlib.h"
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12 | #include "dh_locl.h"
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13 | #include "internal/bn_int.h"
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14 |
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15 | static int generate_key(DH *dh);
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16 | static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
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17 | static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
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18 | const BIGNUM *a, const BIGNUM *p,
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19 | const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
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20 | static int dh_init(DH *dh);
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21 | static int dh_finish(DH *dh);
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22 |
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23 | int DH_generate_key(DH *dh)
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24 | {
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25 | return dh->meth->generate_key(dh);
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26 | }
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27 |
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28 | int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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29 | {
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30 | return dh->meth->compute_key(key, pub_key, dh);
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31 | }
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32 |
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33 | int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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34 | {
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35 | int rv, pad;
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36 | rv = dh->meth->compute_key(key, pub_key, dh);
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37 | if (rv <= 0)
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38 | return rv;
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39 | pad = BN_num_bytes(dh->p) - rv;
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40 | if (pad > 0) {
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41 | memmove(key + pad, key, rv);
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42 | memset(key, 0, pad);
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43 | }
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44 | return rv + pad;
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45 | }
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46 |
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47 | static DH_METHOD dh_ossl = {
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48 | "OpenSSL DH Method",
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49 | generate_key,
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50 | compute_key,
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51 | dh_bn_mod_exp,
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52 | dh_init,
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53 | dh_finish,
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54 | DH_FLAG_FIPS_METHOD,
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55 | NULL,
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56 | NULL
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57 | };
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58 |
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59 | const DH_METHOD *DH_OpenSSL(void)
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60 | {
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61 | return &dh_ossl;
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62 | }
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63 |
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64 | static int generate_key(DH *dh)
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65 | {
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66 | int ok = 0;
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67 | int generate_new_key = 0;
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68 | unsigned l;
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69 | BN_CTX *ctx;
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70 | BN_MONT_CTX *mont = NULL;
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71 | BIGNUM *pub_key = NULL, *priv_key = NULL;
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72 |
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73 | ctx = BN_CTX_new();
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74 | if (ctx == NULL)
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75 | goto err;
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76 |
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77 | if (dh->priv_key == NULL) {
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78 | priv_key = BN_secure_new();
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79 | if (priv_key == NULL)
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80 | goto err;
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81 | generate_new_key = 1;
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82 | } else
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83 | priv_key = dh->priv_key;
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84 |
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85 | if (dh->pub_key == NULL) {
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86 | pub_key = BN_new();
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87 | if (pub_key == NULL)
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88 | goto err;
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89 | } else
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90 | pub_key = dh->pub_key;
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91 |
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92 | if (dh->flags & DH_FLAG_CACHE_MONT_P) {
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93 | mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
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94 | dh->lock, dh->p, ctx);
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95 | if (!mont)
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96 | goto err;
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97 | }
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98 |
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99 | if (generate_new_key) {
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100 | if (dh->q) {
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101 | do {
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102 | if (!BN_rand_range(priv_key, dh->q))
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103 | goto err;
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104 | }
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105 | while (BN_is_zero(priv_key) || BN_is_one(priv_key));
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106 | } else {
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107 | /* secret exponent length */
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108 | l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;
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109 | if (!BN_rand(priv_key, l, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY))
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110 | goto err;
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111 | }
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112 | }
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113 |
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114 | {
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115 | BIGNUM *prk = BN_new();
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116 |
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117 | if (prk == NULL)
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118 | goto err;
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119 | BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
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120 |
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121 | if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) {
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122 | BN_free(prk);
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123 | goto err;
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124 | }
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125 | /* We MUST free prk before any further use of priv_key */
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126 | BN_free(prk);
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127 | }
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128 |
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129 | dh->pub_key = pub_key;
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130 | dh->priv_key = priv_key;
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131 | ok = 1;
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132 | err:
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133 | if (ok != 1)
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134 | DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB);
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135 |
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136 | if (pub_key != dh->pub_key)
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137 | BN_free(pub_key);
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138 | if (priv_key != dh->priv_key)
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139 | BN_free(priv_key);
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140 | BN_CTX_free(ctx);
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141 | return (ok);
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142 | }
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143 |
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144 | static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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145 | {
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146 | BN_CTX *ctx = NULL;
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147 | BN_MONT_CTX *mont = NULL;
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148 | BIGNUM *tmp;
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149 | int ret = -1;
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150 | int check_result;
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151 |
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152 | if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
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153 | DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
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154 | goto err;
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155 | }
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156 |
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157 | ctx = BN_CTX_new();
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158 | if (ctx == NULL)
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159 | goto err;
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160 | BN_CTX_start(ctx);
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161 | tmp = BN_CTX_get(ctx);
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162 | if (tmp == NULL)
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163 | goto err;
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164 |
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165 | if (dh->priv_key == NULL) {
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166 | DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE);
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167 | goto err;
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168 | }
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169 |
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170 | if (dh->flags & DH_FLAG_CACHE_MONT_P) {
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171 | mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
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172 | dh->lock, dh->p, ctx);
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173 | BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
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174 | if (!mont)
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175 | goto err;
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176 | }
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177 |
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178 | if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
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179 | DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY);
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180 | goto err;
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181 | }
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182 |
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183 | if (!dh->
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184 | meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) {
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185 | DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB);
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186 | goto err;
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187 | }
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188 |
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189 | ret = BN_bn2bin(tmp, key);
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190 | err:
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191 | if (ctx != NULL) {
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192 | BN_CTX_end(ctx);
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193 | BN_CTX_free(ctx);
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194 | }
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195 | return (ret);
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196 | }
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197 |
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198 | static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
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199 | const BIGNUM *a, const BIGNUM *p,
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200 | const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
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201 | {
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202 | return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
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203 | }
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204 |
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205 | static int dh_init(DH *dh)
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206 | {
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207 | dh->flags |= DH_FLAG_CACHE_MONT_P;
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208 | return (1);
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209 | }
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210 |
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211 | static int dh_finish(DH *dh)
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212 | {
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213 | BN_MONT_CTX_free(dh->method_mont_p);
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214 | return (1);
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215 | }
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