dh_key.c revision 296341
1/* crypto/dh/dh_key.c */ 2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay@cryptsoft.com). 7 * The implementation was written so as to conform with Netscapes SSL. 8 * 9 * This library is free for commercial and non-commercial use as long as 10 * the following conditions are aheared to. The following conditions 11 * apply to all code found in this distribution, be it the RC4, RSA, 12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 13 * included with this distribution is covered by the same copyright terms 14 * except that the holder is Tim Hudson (tjh@cryptsoft.com). 15 * 16 * Copyright remains Eric Young's, and as such any Copyright notices in 17 * the code are not to be removed. 18 * If this package is used in a product, Eric Young should be given attribution 19 * as the author of the parts of the library used. 20 * This can be in the form of a textual message at program startup or 21 * in documentation (online or textual) provided with the package. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 3. All advertising materials mentioning features or use of this software 32 * must display the following acknowledgement: 33 * "This product includes cryptographic software written by 34 * Eric Young (eay@cryptsoft.com)" 35 * The word 'cryptographic' can be left out if the rouines from the library 36 * being used are not cryptographic related :-). 37 * 4. If you include any Windows specific code (or a derivative thereof) from 38 * the apps directory (application code) you must include an acknowledgement: 39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 40 * 41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 51 * SUCH DAMAGE. 52 * 53 * The licence and distribution terms for any publically available version or 54 * derivative of this code cannot be changed. i.e. this code cannot simply be 55 * copied and put under another distribution licence 56 * [including the GNU Public Licence.] 57 */ 58 59#include <stdio.h> 60#include "cryptlib.h" 61#include <openssl/bn.h> 62#include <openssl/rand.h> 63#include <openssl/dh.h> 64 65static int generate_key(DH *dh); 66static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh); 67static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, 68 const BIGNUM *a, const BIGNUM *p, 69 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); 70static int dh_init(DH *dh); 71static int dh_finish(DH *dh); 72 73int DH_generate_key(DH *dh) 74{ 75#ifdef OPENSSL_FIPS 76 if (FIPS_mode() && !(dh->meth->flags & DH_FLAG_FIPS_METHOD) 77 && !(dh->flags & DH_FLAG_NON_FIPS_ALLOW)) { 78 DHerr(DH_F_DH_GENERATE_KEY, DH_R_NON_FIPS_METHOD); 79 return 0; 80 } 81#endif 82 return dh->meth->generate_key(dh); 83} 84 85int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 86{ 87#ifdef OPENSSL_FIPS 88 if (FIPS_mode() && !(dh->meth->flags & DH_FLAG_FIPS_METHOD) 89 && !(dh->flags & DH_FLAG_NON_FIPS_ALLOW)) { 90 DHerr(DH_F_DH_COMPUTE_KEY, DH_R_NON_FIPS_METHOD); 91 return 0; 92 } 93#endif 94 return dh->meth->compute_key(key, pub_key, dh); 95} 96 97static DH_METHOD dh_ossl = { 98 "OpenSSL DH Method", 99 generate_key, 100 compute_key, 101 dh_bn_mod_exp, 102 dh_init, 103 dh_finish, 104 0, 105 NULL, 106 NULL 107}; 108 109const DH_METHOD *DH_OpenSSL(void) 110{ 111 return &dh_ossl; 112} 113 114static int generate_key(DH *dh) 115{ 116 int ok = 0; 117 int generate_new_key = 0; 118 unsigned l; 119 BN_CTX *ctx; 120 BN_MONT_CTX *mont = NULL; 121 BIGNUM *pub_key = NULL, *priv_key = NULL; 122 123 ctx = BN_CTX_new(); 124 if (ctx == NULL) 125 goto err; 126 127 if (dh->priv_key == NULL) { 128 priv_key = BN_new(); 129 if (priv_key == NULL) 130 goto err; 131 generate_new_key = 1; 132 } else 133 priv_key = dh->priv_key; 134 135 if (dh->pub_key == NULL) { 136 pub_key = BN_new(); 137 if (pub_key == NULL) 138 goto err; 139 } else 140 pub_key = dh->pub_key; 141 142 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 143 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 144 CRYPTO_LOCK_DH, dh->p, ctx); 145 if (!mont) 146 goto err; 147 } 148 149 if (generate_new_key) { 150 if (dh->q) { 151 do { 152 if (!BN_rand_range(priv_key, dh->q)) 153 goto err; 154 } 155 while (BN_is_zero(priv_key) || BN_is_one(priv_key)); 156 } else { 157 /* secret exponent length */ 158 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; 159 if (!BN_rand(priv_key, l, 0, 0)) 160 goto err; 161 } 162 } 163 164 { 165 BIGNUM local_prk; 166 BIGNUM *prk; 167 168 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) { 169 BN_init(&local_prk); 170 prk = &local_prk; 171 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME); 172 } else 173 prk = priv_key; 174 175 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) 176 goto err; 177 } 178 179 dh->pub_key = pub_key; 180 dh->priv_key = priv_key; 181 ok = 1; 182 err: 183 if (ok != 1) 184 DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB); 185 186 if ((pub_key != NULL) && (dh->pub_key == NULL)) 187 BN_free(pub_key); 188 if ((priv_key != NULL) && (dh->priv_key == NULL)) 189 BN_free(priv_key); 190 BN_CTX_free(ctx); 191 return (ok); 192} 193 194static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) 195{ 196 BN_CTX *ctx = NULL; 197 BN_MONT_CTX *mont = NULL; 198 BIGNUM *tmp; 199 int ret = -1; 200 int check_result; 201 202 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 203 DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE); 204 goto err; 205 } 206 207 ctx = BN_CTX_new(); 208 if (ctx == NULL) 209 goto err; 210 BN_CTX_start(ctx); 211 tmp = BN_CTX_get(ctx); 212 213 if (dh->priv_key == NULL) { 214 DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE); 215 goto err; 216 } 217 218 if (dh->flags & DH_FLAG_CACHE_MONT_P) { 219 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, 220 CRYPTO_LOCK_DH, dh->p, ctx); 221 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) { 222 /* XXX */ 223 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); 224 } 225 if (!mont) 226 goto err; 227 } 228 229 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { 230 DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY); 231 goto err; 232 } 233 234 if (!dh-> 235 meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) { 236 DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB); 237 goto err; 238 } 239 240 ret = BN_bn2bin(tmp, key); 241 err: 242 if (ctx != NULL) { 243 BN_CTX_end(ctx); 244 BN_CTX_free(ctx); 245 } 246 return (ret); 247} 248 249static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, 250 const BIGNUM *a, const BIGNUM *p, 251 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) 252{ 253 /* 254 * If a is only one word long and constant time is false, use the faster 255 * exponenentiation function. 256 */ 257 if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) { 258 BN_ULONG A = a->d[0]; 259 return BN_mod_exp_mont_word(r, A, p, m, ctx, m_ctx); 260 } else 261 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); 262} 263 264static int dh_init(DH *dh) 265{ 266 dh->flags |= DH_FLAG_CACHE_MONT_P; 267 return (1); 268} 269 270static int dh_finish(DH *dh) 271{ 272 if (dh->method_mont_p) 273 BN_MONT_CTX_free(dh->method_mont_p); 274 return (1); 275} 276