1 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com) 2 * All rights reserved. 3 * 4 * This package is an SSL implementation written 5 * by Eric Young (eay (at) cryptsoft.com). 6 * The implementation was written so as to conform with Netscapes SSL. 7 * 8 * This library is free for commercial and non-commercial use as long as 9 * the following conditions are aheared to. The following conditions 10 * apply to all code found in this distribution, be it the RC4, RSA, 11 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 12 * included with this distribution is covered by the same copyright terms 13 * except that the holder is Tim Hudson (tjh (at) cryptsoft.com). 14 * 15 * Copyright remains Eric Young's, and as such any Copyright notices in 16 * the code are not to be removed. 17 * If this package is used in a product, Eric Young should be given attribution 18 * as the author of the parts of the library used. 19 * This can be in the form of a textual message at program startup or 20 * in documentation (online or textual) provided with the package. 21 * 22 * Redistribution and use in source and binary forms, with or without 23 * modification, are permitted provided that the following conditions 24 * are met: 25 * 1. Redistributions of source code must retain the copyright 26 * notice, this list of conditions and the following disclaimer. 27 * 2. Redistributions in binary form must reproduce the above copyright 28 * notice, this list of conditions and the following disclaimer in the 29 * documentation and/or other materials provided with the distribution. 30 * 3. All advertising materials mentioning features or use of this software 31 * must display the following acknowledgement: 32 * "This product includes cryptographic software written by 33 * Eric Young (eay (at) cryptsoft.com)" 34 * The word 'cryptographic' can be left out if the rouines from the library 35 * being used are not cryptographic related :-). 36 * 4. If you include any Windows specific code (or a derivative thereof) from 37 * the apps directory (application code) you must include an acknowledgement: 38 * "This product includes software written by Tim Hudson (tjh (at) cryptsoft.com)" 39 * 40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 43 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 50 * SUCH DAMAGE. 51 * 52 * The licence and distribution terms for any publically available version or 53 * derivative of this code cannot be changed. i.e. this code cannot simply be 54 * copied and put under another distribution licence 55 * [including the GNU Public Licence.] */ 56 57 #include <openssl/dh.h> 58 59 #include <string.h> 60 61 #include <openssl/bn.h> 62 #include <openssl/buf.h> 63 #include <openssl/err.h> 64 #include <openssl/ex_data.h> 65 #include <openssl/mem.h> 66 #include <openssl/thread.h> 67 68 #include "internal.h" 69 #include "../internal.h" 70 71 72 #define OPENSSL_DH_MAX_MODULUS_BITS 10000 73 74 static CRYPTO_EX_DATA_CLASS g_ex_data_class = CRYPTO_EX_DATA_CLASS_INIT; 75 76 DH *DH_new(void) { 77 DH *dh = (DH *)OPENSSL_malloc(sizeof(DH)); 78 if (dh == NULL) { 79 OPENSSL_PUT_ERROR(DH, ERR_R_MALLOC_FAILURE); 80 return NULL; 81 } 82 83 memset(dh, 0, sizeof(DH)); 84 85 CRYPTO_MUTEX_init(&dh->method_mont_p_lock); 86 87 dh->references = 1; 88 CRYPTO_new_ex_data(&dh->ex_data); 89 90 return dh; 91 } 92 93 void DH_free(DH *dh) { 94 if (dh == NULL) { 95 return; 96 } 97 98 if (!CRYPTO_refcount_dec_and_test_zero(&dh->references)) { 99 return; 100 } 101 102 CRYPTO_free_ex_data(&g_ex_data_class, dh, &dh->ex_data); 103 104 BN_MONT_CTX_free(dh->method_mont_p); 105 BN_clear_free(dh->p); 106 BN_clear_free(dh->g); 107 BN_clear_free(dh->q); 108 BN_clear_free(dh->j); 109 OPENSSL_free(dh->seed); 110 BN_clear_free(dh->counter); 111 BN_clear_free(dh->pub_key); 112 BN_clear_free(dh->priv_key); 113 CRYPTO_MUTEX_cleanup(&dh->method_mont_p_lock); 114 115 OPENSSL_free(dh); 116 } 117 118 int DH_generate_parameters_ex(DH *dh, int prime_bits, int generator, BN_GENCB *cb) { 119 /* We generate DH parameters as follows 120 * find a prime q which is prime_bits/2 bits long. 121 * p=(2*q)+1 or (p-1)/2 = q 122 * For this case, g is a generator if 123 * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1. 124 * Since the factors of p-1 are q and 2, we just need to check 125 * g^2 mod p != 1 and g^q mod p != 1. 126 * 127 * Having said all that, 128 * there is another special case method for the generators 2, 3 and 5. 129 * for 2, p mod 24 == 11 130 * for 3, p mod 12 == 5 <<<<< does not work for safe primes. 131 * for 5, p mod 10 == 3 or 7 132 * 133 * Thanks to Phil Karn <karn (at) qualcomm.com> for the pointers about the 134 * special generators and for answering some of my questions. 135 * 136 * I've implemented the second simple method :-). 137 * Since DH should be using a safe prime (both p and q are prime), 138 * this generator function can take a very very long time to run. 139 */ 140 141 /* Actually there is no reason to insist that 'generator' be a generator. 142 * It's just as OK (and in some sense better) to use a generator of the 143 * order-q subgroup. 144 */ 145 146 BIGNUM *t1, *t2; 147 int g, ok = 0; 148 BN_CTX *ctx = NULL; 149 150 ctx = BN_CTX_new(); 151 if (ctx == NULL) { 152 goto err; 153 } 154 BN_CTX_start(ctx); 155 t1 = BN_CTX_get(ctx); 156 t2 = BN_CTX_get(ctx); 157 if (t1 == NULL || t2 == NULL) { 158 goto err; 159 } 160 161 /* Make sure |dh| has the necessary elements */ 162 if (dh->p == NULL) { 163 dh->p = BN_new(); 164 if (dh->p == NULL) { 165 goto err; 166 } 167 } 168 if (dh->g == NULL) { 169 dh->g = BN_new(); 170 if (dh->g == NULL) { 171 goto err; 172 } 173 } 174 175 if (generator <= 1) { 176 OPENSSL_PUT_ERROR(DH, DH_R_BAD_GENERATOR); 177 goto err; 178 } 179 if (generator == DH_GENERATOR_2) { 180 if (!BN_set_word(t1, 24)) { 181 goto err; 182 } 183 if (!BN_set_word(t2, 11)) { 184 goto err; 185 } 186 g = 2; 187 } else if (generator == DH_GENERATOR_5) { 188 if (!BN_set_word(t1, 10)) { 189 goto err; 190 } 191 if (!BN_set_word(t2, 3)) { 192 goto err; 193 } 194 /* BN_set_word(t3,7); just have to miss 195 * out on these ones :-( */ 196 g = 5; 197 } else { 198 /* in the general case, don't worry if 'generator' is a 199 * generator or not: since we are using safe primes, 200 * it will generate either an order-q or an order-2q group, 201 * which both is OK */ 202 if (!BN_set_word(t1, 2)) { 203 goto err; 204 } 205 if (!BN_set_word(t2, 1)) { 206 goto err; 207 } 208 g = generator; 209 } 210 211 if (!BN_generate_prime_ex(dh->p, prime_bits, 1, t1, t2, cb)) { 212 goto err; 213 } 214 if (!BN_GENCB_call(cb, 3, 0)) { 215 goto err; 216 } 217 if (!BN_set_word(dh->g, g)) { 218 goto err; 219 } 220 ok = 1; 221 222 err: 223 if (!ok) { 224 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB); 225 } 226 227 if (ctx != NULL) { 228 BN_CTX_end(ctx); 229 BN_CTX_free(ctx); 230 } 231 return ok; 232 } 233 234 int DH_generate_key(DH *dh) { 235 int ok = 0; 236 int generate_new_key = 0; 237 unsigned l; 238 BN_CTX *ctx = NULL; 239 BN_MONT_CTX *mont = NULL; 240 BIGNUM *pub_key = NULL, *priv_key = NULL; 241 BIGNUM local_priv; 242 243 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 244 OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE); 245 goto err; 246 } 247 248 ctx = BN_CTX_new(); 249 if (ctx == NULL) { 250 goto err; 251 } 252 253 if (dh->priv_key == NULL) { 254 priv_key = BN_new(); 255 if (priv_key == NULL) { 256 goto err; 257 } 258 generate_new_key = 1; 259 } else { 260 priv_key = dh->priv_key; 261 } 262 263 if (dh->pub_key == NULL) { 264 pub_key = BN_new(); 265 if (pub_key == NULL) { 266 goto err; 267 } 268 } else { 269 pub_key = dh->pub_key; 270 } 271 272 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock, 273 dh->p, ctx); 274 if (!mont) { 275 goto err; 276 } 277 278 if (generate_new_key) { 279 if (dh->q) { 280 do { 281 if (!BN_rand_range(priv_key, dh->q)) { 282 goto err; 283 } 284 } while (BN_is_zero(priv_key) || BN_is_one(priv_key)); 285 } else { 286 /* secret exponent length */ 287 DH_check_standard_parameters(dh); 288 l = dh->priv_length ? dh->priv_length : BN_num_bits(dh->p) - 1; 289 if (!BN_rand(priv_key, l, 0, 0)) { 290 goto err; 291 } 292 } 293 } 294 295 BN_with_flags(&local_priv, priv_key, BN_FLG_CONSTTIME); 296 if (!BN_mod_exp_mont(pub_key, dh->g, &local_priv, dh->p, ctx, mont)) { 297 goto err; 298 } 299 300 dh->pub_key = pub_key; 301 dh->priv_key = priv_key; 302 ok = 1; 303 304 err: 305 if (ok != 1) { 306 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB); 307 } 308 309 if (dh->pub_key == NULL) { 310 BN_free(pub_key); 311 } 312 if (dh->priv_key == NULL) { 313 BN_free(priv_key); 314 } 315 BN_CTX_free(ctx); 316 return ok; 317 } 318 319 int DH_compute_key(unsigned char *out, const BIGNUM *peers_key, DH *dh) { 320 BN_CTX *ctx = NULL; 321 BN_MONT_CTX *mont = NULL; 322 BIGNUM *shared_key; 323 int ret = -1; 324 int check_result; 325 BIGNUM local_priv; 326 327 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 328 OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE); 329 goto err; 330 } 331 332 ctx = BN_CTX_new(); 333 if (ctx == NULL) { 334 goto err; 335 } 336 BN_CTX_start(ctx); 337 shared_key = BN_CTX_get(ctx); 338 if (shared_key == NULL) { 339 goto err; 340 } 341 342 if (dh->priv_key == NULL) { 343 OPENSSL_PUT_ERROR(DH, DH_R_NO_PRIVATE_VALUE); 344 goto err; 345 } 346 347 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock, 348 dh->p, ctx); 349 if (!mont) { 350 goto err; 351 } 352 353 if (!DH_check_pub_key(dh, peers_key, &check_result) || check_result) { 354 OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PUBKEY); 355 goto err; 356 } 357 358 BN_with_flags(&local_priv, dh->priv_key, BN_FLG_CONSTTIME); 359 if (!BN_mod_exp_mont(shared_key, peers_key, &local_priv, dh->p, ctx, 360 mont)) { 361 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB); 362 goto err; 363 } 364 365 ret = BN_bn2bin(shared_key, out); 366 367 err: 368 if (ctx != NULL) { 369 BN_CTX_end(ctx); 370 BN_CTX_free(ctx); 371 } 372 373 return ret; 374 } 375 376 int DH_size(const DH *dh) { return BN_num_bytes(dh->p); } 377 378 unsigned DH_num_bits(const DH *dh) { return BN_num_bits(dh->p); } 379 380 int DH_up_ref(DH *dh) { 381 CRYPTO_refcount_inc(&dh->references); 382 return 1; 383 } 384 385 static int int_dh_bn_cpy(BIGNUM **dst, const BIGNUM *src) { 386 BIGNUM *a = NULL; 387 388 if (src) { 389 a = BN_dup(src); 390 if (!a) { 391 return 0; 392 } 393 } 394 395 BN_free(*dst); 396 *dst = a; 397 return 1; 398 } 399 400 static int int_dh_param_copy(DH *to, const DH *from, int is_x942) { 401 if (is_x942 == -1) { 402 is_x942 = !!from->q; 403 } 404 if (!int_dh_bn_cpy(&to->p, from->p) || 405 !int_dh_bn_cpy(&to->g, from->g)) { 406 return 0; 407 } 408 409 if (!is_x942) { 410 return 1; 411 } 412 413 if (!int_dh_bn_cpy(&to->q, from->q) || 414 !int_dh_bn_cpy(&to->j, from->j)) { 415 return 0; 416 } 417 418 OPENSSL_free(to->seed); 419 to->seed = NULL; 420 to->seedlen = 0; 421 422 if (from->seed) { 423 to->seed = BUF_memdup(from->seed, from->seedlen); 424 if (!to->seed) { 425 return 0; 426 } 427 to->seedlen = from->seedlen; 428 } 429 430 return 1; 431 } 432 433 DH *DHparams_dup(const DH *dh) { 434 DH *ret = DH_new(); 435 if (!ret) { 436 return NULL; 437 } 438 439 if (!int_dh_param_copy(ret, dh, -1)) { 440 DH_free(ret); 441 return NULL; 442 } 443 444 return ret; 445 } 446 447 int DH_get_ex_new_index(long argl, void *argp, CRYPTO_EX_unused *unused, 448 CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func) { 449 int index; 450 if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp, dup_func, 451 free_func)) { 452 return -1; 453 } 454 return index; 455 } 456 457 int DH_set_ex_data(DH *d, int idx, void *arg) { 458 return CRYPTO_set_ex_data(&d->ex_data, idx, arg); 459 } 460 461 void *DH_get_ex_data(DH *d, int idx) { 462 return CRYPTO_get_ex_data(&d->ex_data, idx); 463 } 464
