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 int DH_set0_key(DH *dh, BIGNUM *pub_key, BIGNUM *priv_key) { 128 if (pub_key != NULL) { 129 BN_free(dh->pub_key); 130 dh->pub_key = pub_key; 131 } 132 133 if (priv_key != NULL) { 134 BN_free(dh->priv_key); 135 dh->priv_key = priv_key; 136 } 137 138 return 1; 139 } 140 141 void DH_get0_pqg(const DH *dh, const BIGNUM **out_p, const BIGNUM **out_q, 142 const BIGNUM **out_g) { 143 if (out_p != NULL) { 144 *out_p = dh->p; 145 } 146 if (out_q != NULL) { 147 *out_q = dh->q; 148 } 149 if (out_g != NULL) { 150 *out_g = dh->g; 151 } 152 } 153 154 int DH_set0_pqg(DH *dh, BIGNUM *p, BIGNUM *q, BIGNUM *g) { 155 if ((dh->p == NULL && p == NULL) || 156 (dh->g == NULL && g == NULL)) { 157 return 0; 158 } 159 160 if (p != NULL) { 161 BN_free(dh->p); 162 dh->p = p; 163 } 164 165 if (q != NULL) { 166 BN_free(dh->q); 167 dh->q = q; 168 } 169 170 if (g != NULL) { 171 BN_free(dh->g); 172 dh->g = g; 173 } 174 175 return 1; 176 } 177 178 int DH_generate_parameters_ex(DH *dh, int prime_bits, int generator, BN_GENCB *cb) { 179 // We generate DH parameters as follows 180 // find a prime q which is prime_bits/2 bits long. 181 // p=(2*q)+1 or (p-1)/2 = q 182 // For this case, g is a generator if 183 // g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1. 184 // Since the factors of p-1 are q and 2, we just need to check 185 // g^2 mod p != 1 and g^q mod p != 1. 186 // 187 // Having said all that, 188 // there is another special case method for the generators 2, 3 and 5. 189 // for 2, p mod 24 == 11 190 // for 3, p mod 12 == 5 <<<<< does not work for safe primes. 191 // for 5, p mod 10 == 3 or 7 192 // 193 // Thanks to Phil Karn <karn (at) qualcomm.com> for the pointers about the 194 // special generators and for answering some of my questions. 195 // 196 // I've implemented the second simple method :-). 197 // Since DH should be using a safe prime (both p and q are prime), 198 // this generator function can take a very very long time to run. 199 200 // Actually there is no reason to insist that 'generator' be a generator. 201 // It's just as OK (and in some sense better) to use a generator of the 202 // order-q subgroup. 203 204 BIGNUM *t1, *t2; 205 int g, ok = 0; 206 BN_CTX *ctx = NULL; 207 208 ctx = BN_CTX_new(); 209 if (ctx == NULL) { 210 goto err; 211 } 212 BN_CTX_start(ctx); 213 t1 = BN_CTX_get(ctx); 214 t2 = BN_CTX_get(ctx); 215 if (t1 == NULL || t2 == NULL) { 216 goto err; 217 } 218 219 // Make sure |dh| has the necessary elements 220 if (dh->p == NULL) { 221 dh->p = BN_new(); 222 if (dh->p == NULL) { 223 goto err; 224 } 225 } 226 if (dh->g == NULL) { 227 dh->g = BN_new(); 228 if (dh->g == NULL) { 229 goto err; 230 } 231 } 232 233 if (generator <= 1) { 234 OPENSSL_PUT_ERROR(DH, DH_R_BAD_GENERATOR); 235 goto err; 236 } 237 if (generator == DH_GENERATOR_2) { 238 if (!BN_set_word(t1, 24)) { 239 goto err; 240 } 241 if (!BN_set_word(t2, 11)) { 242 goto err; 243 } 244 g = 2; 245 } else if (generator == DH_GENERATOR_5) { 246 if (!BN_set_word(t1, 10)) { 247 goto err; 248 } 249 if (!BN_set_word(t2, 3)) { 250 goto err; 251 } 252 // BN_set_word(t3,7); just have to miss 253 // out on these ones :-( 254 g = 5; 255 } else { 256 // in the general case, don't worry if 'generator' is a 257 // generator or not: since we are using safe primes, 258 // it will generate either an order-q or an order-2q group, 259 // which both is OK 260 if (!BN_set_word(t1, 2)) { 261 goto err; 262 } 263 if (!BN_set_word(t2, 1)) { 264 goto err; 265 } 266 g = generator; 267 } 268 269 if (!BN_generate_prime_ex(dh->p, prime_bits, 1, t1, t2, cb)) { 270 goto err; 271 } 272 if (!BN_GENCB_call(cb, 3, 0)) { 273 goto err; 274 } 275 if (!BN_set_word(dh->g, g)) { 276 goto err; 277 } 278 ok = 1; 279 280 err: 281 if (!ok) { 282 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB); 283 } 284 285 if (ctx != NULL) { 286 BN_CTX_end(ctx); 287 BN_CTX_free(ctx); 288 } 289 return ok; 290 } 291 292 int DH_generate_key(DH *dh) { 293 int ok = 0; 294 int generate_new_key = 0; 295 BN_CTX *ctx = NULL; 296 BIGNUM *pub_key = NULL, *priv_key = NULL; 297 298 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 299 OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE); 300 goto err; 301 } 302 303 ctx = BN_CTX_new(); 304 if (ctx == NULL) { 305 goto err; 306 } 307 308 if (dh->priv_key == NULL) { 309 priv_key = BN_new(); 310 if (priv_key == NULL) { 311 goto err; 312 } 313 generate_new_key = 1; 314 } else { 315 priv_key = dh->priv_key; 316 } 317 318 if (dh->pub_key == NULL) { 319 pub_key = BN_new(); 320 if (pub_key == NULL) { 321 goto err; 322 } 323 } else { 324 pub_key = dh->pub_key; 325 } 326 327 if (!BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock, 328 dh->p, ctx)) { 329 goto err; 330 } 331 332 if (generate_new_key) { 333 if (dh->q) { 334 if (!BN_rand_range_ex(priv_key, 2, dh->q)) { 335 goto err; 336 } 337 } else { 338 // secret exponent length 339 unsigned priv_bits = dh->priv_length; 340 if (priv_bits == 0) { 341 const unsigned p_bits = BN_num_bits(dh->p); 342 if (p_bits == 0) { 343 goto err; 344 } 345 346 priv_bits = p_bits - 1; 347 } 348 349 if (!BN_rand(priv_key, priv_bits, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY)) { 350 goto err; 351 } 352 } 353 } 354 355 if (!BN_mod_exp_mont_consttime(pub_key, dh->g, priv_key, dh->p, ctx, 356 dh->method_mont_p)) { 357 goto err; 358 } 359 360 dh->pub_key = pub_key; 361 dh->priv_key = priv_key; 362 ok = 1; 363 364 err: 365 if (ok != 1) { 366 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB); 367 } 368 369 if (dh->pub_key == NULL) { 370 BN_free(pub_key); 371 } 372 if (dh->priv_key == NULL) { 373 BN_free(priv_key); 374 } 375 BN_CTX_free(ctx); 376 return ok; 377 } 378 379 int DH_compute_key(unsigned char *out, const BIGNUM *peers_key, DH *dh) { 380 BN_CTX *ctx = NULL; 381 BIGNUM *shared_key; 382 int ret = -1; 383 int check_result; 384 385 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { 386 OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE); 387 goto err; 388 } 389 390 ctx = BN_CTX_new(); 391 if (ctx == NULL) { 392 goto err; 393 } 394 BN_CTX_start(ctx); 395 shared_key = BN_CTX_get(ctx); 396 if (shared_key == NULL) { 397 goto err; 398 } 399 400 if (dh->priv_key == NULL) { 401 OPENSSL_PUT_ERROR(DH, DH_R_NO_PRIVATE_VALUE); 402 goto err; 403 } 404 405 if (!BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock, 406 dh->p, ctx)) { 407 goto err; 408 } 409 410 if (!DH_check_pub_key(dh, peers_key, &check_result) || check_result) { 411 OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PUBKEY); 412 goto err; 413 } 414 415 if (!BN_mod_exp_mont_consttime(shared_key, peers_key, dh->priv_key, dh->p, 416 ctx, dh->method_mont_p)) { 417 OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB); 418 goto err; 419 } 420 421 ret = BN_bn2bin(shared_key, out); 422 423 err: 424 if (ctx != NULL) { 425 BN_CTX_end(ctx); 426 BN_CTX_free(ctx); 427 } 428 429 return ret; 430 } 431 432 int DH_size(const DH *dh) { return BN_num_bytes(dh->p); } 433 434 unsigned DH_num_bits(const DH *dh) { return BN_num_bits(dh->p); } 435 436 int DH_up_ref(DH *dh) { 437 CRYPTO_refcount_inc(&dh->references); 438 return 1; 439 } 440 441 static int int_dh_bn_cpy(BIGNUM **dst, const BIGNUM *src) { 442 BIGNUM *a = NULL; 443 444 if (src) { 445 a = BN_dup(src); 446 if (!a) { 447 return 0; 448 } 449 } 450 451 BN_free(*dst); 452 *dst = a; 453 return 1; 454 } 455 456 static int int_dh_param_copy(DH *to, const DH *from, int is_x942) { 457 if (is_x942 == -1) { 458 is_x942 = !!from->q; 459 } 460 if (!int_dh_bn_cpy(&to->p, from->p) || 461 !int_dh_bn_cpy(&to->g, from->g)) { 462 return 0; 463 } 464 465 if (!is_x942) { 466 return 1; 467 } 468 469 if (!int_dh_bn_cpy(&to->q, from->q) || 470 !int_dh_bn_cpy(&to->j, from->j)) { 471 return 0; 472 } 473 474 OPENSSL_free(to->seed); 475 to->seed = NULL; 476 to->seedlen = 0; 477 478 if (from->seed) { 479 to->seed = BUF_memdup(from->seed, from->seedlen); 480 if (!to->seed) { 481 return 0; 482 } 483 to->seedlen = from->seedlen; 484 } 485 486 return 1; 487 } 488 489 DH *DHparams_dup(const DH *dh) { 490 DH *ret = DH_new(); 491 if (!ret) { 492 return NULL; 493 } 494 495 if (!int_dh_param_copy(ret, dh, -1)) { 496 DH_free(ret); 497 return NULL; 498 } 499 500 return ret; 501 } 502 503 int DH_get_ex_new_index(long argl, void *argp, CRYPTO_EX_unused *unused, 504 CRYPTO_EX_dup *dup_unused, CRYPTO_EX_free *free_func) { 505 int index; 506 if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp, 507 free_func)) { 508 return -1; 509 } 510 return index; 511 } 512 513 int DH_set_ex_data(DH *d, int idx, void *arg) { 514 return CRYPTO_set_ex_data(&d->ex_data, idx, arg); 515 } 516 517 void *DH_get_ex_data(DH *d, int idx) { 518 return CRYPTO_get_ex_data(&d->ex_data, idx); 519 } 520
