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 70 71 #define OPENSSL_DH_MAX_MODULUS_BITS 10000 72 73 static CRYPTO_EX_DATA_CLASS g_ex_data_class = CRYPTO_EX_DATA_CLASS_INIT; 74 75 DH *DH_new(void) { 76 DH *dh = OPENSSL_malloc(sizeof(DH)); 77 if (dh == NULL) { 78 OPENSSL_PUT_ERROR(DH, ERR_R_MALLOC_FAILURE); 79 return NULL; 80 } 81 82 OPENSSL_memset(dh, 0, sizeof(DH)); 83 84 CRYPTO_MUTEX_init(&dh->method_mont_p_lock); 85 86 dh->references = 1; 87 CRYPTO_new_ex_data(&dh->ex_data); 88 89 return dh; 90 } 91 92 void DH_free(DH *dh) { 93 if (dh == NULL) { 94 return; 95 } 96 97 if (!CRYPTO_refcount_dec_and_test_zero(&dh->references)) { 98 return; 99 } 100 101 CRYPTO_free_ex_data(&g_ex_data_class, dh, &dh->ex_data); 102 103 BN_MONT_CTX_free(dh->method_mont_p); 104 BN_clear_free(dh->p); 105 BN_clear_free(dh->g); 106 BN_clear_free(dh->q); 107 BN_clear_free(dh->j); 108 OPENSSL_free(dh->seed); 109 BN_clear_free(dh->counter); 110 BN_clear_free(dh->pub_key); 111 BN_clear_free(dh->priv_key); 112 CRYPTO_MUTEX_cleanup(&dh->method_mont_p_lock); 113 114 OPENSSL_free(dh); 115 } 116 117 void DH_get0_key(const DH *dh, const BIGNUM **out_pub_key, 118 const BIGNUM **out_priv_key) { 119 if (out_pub_key != NULL) { 120 *out_pub_key = dh->pub_key; 121 } 122 if (out_priv_key != NULL) { 123 *out_priv_key = dh->priv_key; 124 } 125 } 126 127 void DH_get0_pqg(const DH *dh, const BIGNUM **out_p, const BIGNUM **out_q, 128 const BIGNUM **out_g) { 129 if (out_p != NULL) { 130 *out_p = dh->p; 131 } 132 if (out_q != NULL) { 133 *out_q = dh->q; 134 } 135 if (out_g != NULL) { 136 *out_g = dh->g; 137 } 138 } 139 140 int DH_generate_parameters_ex(DH *dh, int prime_bits, int generator, BN_GENCB *cb) { 141 /* We generate DH parameters as follows 142 * find a prime q which is prime_bits/2 bits long. 143 * p=(2*q)+1 or (p-1)/2 = q 144 * For this case, g is a generator if 145 * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1. 146 * Since the factors of p-1 are q and 2, we just need to check 147 * g^2 mod p != 1 and g^q mod p != 1. 148 * 149 * Having said all that, 150 * there is another special case method for the generators 2, 3 and 5. 151 * for 2, p mod 24 == 11 152 * for 3, p mod 12 == 5 <<<<< does not work for safe primes. 153 * for 5, p mod 10 == 3 or 7 154 * 155 * Thanks to Phil Karn <karn (at) qualcomm.com> for the pointers about the 156 * special generators and for answering some of my questions. 157 * 158 * I've implemented the second simple method :-). 159 * Since DH should be using a safe prime (both p and q are prime), 160 * this generator function can take a very very long time to run. 161 */ 162 163 /* Actually there is no reason to insist that 'generator' be a generator. 164 * It's just as OK (and in some sense better) to use a generator of the 165 * order-q subgroup. 166 */ 167 168 BIGNUM *t1, *t2; 169 int g, ok = 0; 170 BN_CTX *ctx = NULL; 171 172 ctx = BN_CTX_new(); 173 if (ctx == NULL) { 174 goto err; 175 } 176 BN_CTX_start(ctx); 177 t1 = BN_CTX_get(ctx); 178 t2 = BN_CTX_get(ctx); 179 if (t1 == NULL || t2 == NULL) { 180 goto err; 181 } 182 183 /* Make sure |dh| has the necessary elements */ 184 if (dh->p == NULL) { 185 dh->p = BN_new(); 186 if (dh->p == NULL) { 187 goto err; 188 } 189 } 190 if (dh->g == NULL) { 191 dh->g = BN_new(); 192 if (dh->g == NULL) { 193 goto err; 194 } 195 } 196 197 if (generator <= 1) { 198 OPENSSL_PUT_ERROR(DH, DH_R_BAD_GENERATOR); 199 goto err; 200 } 201 if (generator == DH_GENERATOR_2) { 202 if (!BN_set_word(t1, 24)) { 203 goto err; 204 } 205 if (!BN_set_word(t2, 11)) { 206 goto err; 207 } 208 g = 2; 209 } else if (generator == DH_GENERATOR_5) { 210 if (!BN_set_word(t1, 10)) { 211 goto err; 212 } 213 if (!BN_set_word(t2, 3)) { 214 goto err; 215 } 216 /* BN_set_word(t3,7); just have to miss 217 * out on these ones :-( */ 218 g = 5; 219 } else { 220 /* in the general case, don't worry if 'generator' is a 221 * generator or not: since we are using safe primes, 222 * it will generate either an order-q or an order-2q group, 223 * which both is OK */ 224 if (!BN_set_word(t1, 2)) { 225 goto err; 226 } 227 if (!BN_set_word(t2, 1)) { 228 goto err; 229 } 230 g = generator; 231 } 232 233 if (!BN_generate_prime_ex(dh->p, prime_bits, 1, t1, t2, cb)) { 234 goto err; 235 } 236 if (!BN_GENCB_call(cb, 3, 0)) { 237 goto err; 238 } 239 if (!BN_set_word(dh->g, g)) { 240 goto err; 241 } 242 ok = 1; 243 244 err: 245 if (!ok) { 246 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB); 247 } 248 249 if (ctx != NULL) { 250 BN_CTX_end(ctx); 251 BN_CTX_free(ctx); 252 } 253 return ok; 254 } 255 256 int DH_generate_key(DH *dh) { 257 int ok = 0; 258 int generate_new_key = 0; 259 BN_CTX *ctx = NULL; 260 BIGNUM *pub_key = NULL, *priv_key = NULL; 261 262 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 263 OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE); 264 goto err; 265 } 266 267 ctx = BN_CTX_new(); 268 if (ctx == NULL) { 269 goto err; 270 } 271 272 if (dh->priv_key == NULL) { 273 priv_key = BN_new(); 274 if (priv_key == NULL) { 275 goto err; 276 } 277 generate_new_key = 1; 278 } else { 279 priv_key = dh->priv_key; 280 } 281 282 if (dh->pub_key == NULL) { 283 pub_key = BN_new(); 284 if (pub_key == NULL) { 285 goto err; 286 } 287 } else { 288 pub_key = dh->pub_key; 289 } 290 291 if (!BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock, 292 dh->p, ctx)) { 293 goto err; 294 } 295 296 if (generate_new_key) { 297 if (dh->q) { 298 if (!BN_rand_range_ex(priv_key, 2, dh->q)) { 299 goto err; 300 } 301 } else { 302 /* secret exponent length */ 303 unsigned priv_bits = dh->priv_length; 304 if (priv_bits == 0) { 305 const unsigned p_bits = BN_num_bits(dh->p); 306 if (p_bits == 0) { 307 goto err; 308 } 309 310 priv_bits = p_bits - 1; 311 } 312 313 if (!BN_rand(priv_key, priv_bits, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY)) { 314 goto err; 315 } 316 } 317 } 318 319 if (!BN_mod_exp_mont_consttime(pub_key, dh->g, priv_key, dh->p, ctx, 320 dh->method_mont_p)) { 321 goto err; 322 } 323 324 dh->pub_key = pub_key; 325 dh->priv_key = priv_key; 326 ok = 1; 327 328 err: 329 if (ok != 1) { 330 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB); 331 } 332 333 if (dh->pub_key == NULL) { 334 BN_free(pub_key); 335 } 336 if (dh->priv_key == NULL) { 337 BN_free(priv_key); 338 } 339 BN_CTX_free(ctx); 340 return ok; 341 } 342 343 int DH_compute_key(unsigned char *out, const BIGNUM *peers_key, DH *dh) { 344 BN_CTX *ctx = NULL; 345 BIGNUM *shared_key; 346 int ret = -1; 347 int check_result; 348 349 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 350 OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE); 351 goto err; 352 } 353 354 ctx = BN_CTX_new(); 355 if (ctx == NULL) { 356 goto err; 357 } 358 BN_CTX_start(ctx); 359 shared_key = BN_CTX_get(ctx); 360 if (shared_key == NULL) { 361 goto err; 362 } 363 364 if (dh->priv_key == NULL) { 365 OPENSSL_PUT_ERROR(DH, DH_R_NO_PRIVATE_VALUE); 366 goto err; 367 } 368 369 if (!BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock, 370 dh->p, ctx)) { 371 goto err; 372 } 373 374 if (!DH_check_pub_key(dh, peers_key, &check_result) || check_result) { 375 OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PUBKEY); 376 goto err; 377 } 378 379 if (!BN_mod_exp_mont_consttime(shared_key, peers_key, dh->priv_key, dh->p, 380 ctx, dh->method_mont_p)) { 381 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB); 382 goto err; 383 } 384 385 ret = BN_bn2bin(shared_key, out); 386 387 err: 388 if (ctx != NULL) { 389 BN_CTX_end(ctx); 390 BN_CTX_free(ctx); 391 } 392 393 return ret; 394 } 395 396 int DH_size(const DH *dh) { return BN_num_bytes(dh->p); } 397 398 unsigned DH_num_bits(const DH *dh) { return BN_num_bits(dh->p); } 399 400 int DH_up_ref(DH *dh) { 401 CRYPTO_refcount_inc(&dh->references); 402 return 1; 403 } 404 405 static int int_dh_bn_cpy(BIGNUM **dst, const BIGNUM *src) { 406 BIGNUM *a = NULL; 407 408 if (src) { 409 a = BN_dup(src); 410 if (!a) { 411 return 0; 412 } 413 } 414 415 BN_free(*dst); 416 *dst = a; 417 return 1; 418 } 419 420 static int int_dh_param_copy(DH *to, const DH *from, int is_x942) { 421 if (is_x942 == -1) { 422 is_x942 = !!from->q; 423 } 424 if (!int_dh_bn_cpy(&to->p, from->p) || 425 !int_dh_bn_cpy(&to->g, from->g)) { 426 return 0; 427 } 428 429 if (!is_x942) { 430 return 1; 431 } 432 433 if (!int_dh_bn_cpy(&to->q, from->q) || 434 !int_dh_bn_cpy(&to->j, from->j)) { 435 return 0; 436 } 437 438 OPENSSL_free(to->seed); 439 to->seed = NULL; 440 to->seedlen = 0; 441 442 if (from->seed) { 443 to->seed = BUF_memdup(from->seed, from->seedlen); 444 if (!to->seed) { 445 return 0; 446 } 447 to->seedlen = from->seedlen; 448 } 449 450 return 1; 451 } 452 453 DH *DHparams_dup(const DH *dh) { 454 DH *ret = DH_new(); 455 if (!ret) { 456 return NULL; 457 } 458 459 if (!int_dh_param_copy(ret, dh, -1)) { 460 DH_free(ret); 461 return NULL; 462 } 463 464 return ret; 465 } 466 467 int DH_get_ex_new_index(long argl, void *argp, CRYPTO_EX_unused *unused, 468 CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func) { 469 int index; 470 if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp, dup_func, 471 free_func)) { 472 return -1; 473 } 474 return index; 475 } 476 477 int DH_set_ex_data(DH *d, int idx, void *arg) { 478 return CRYPTO_set_ex_data(&d->ex_data, idx, arg); 479 } 480 481 void *DH_get_ex_data(DH *d, int idx) { 482 return CRYPTO_get_ex_data(&d->ex_data, idx); 483 } 484
