1 /* $OpenBSD: bn_lib.c,v 1.47 2019/06/17 17:11:48 tb Exp $ */ 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 #ifndef BN_DEBUG 60 # undef NDEBUG /* avoid conflicting definitions */ 61 # define NDEBUG 62 #endif 63 64 #include <assert.h> 65 #include <limits.h> 66 #include <stdio.h> 67 #include <string.h> 68 69 #include <openssl/opensslconf.h> 70 71 #include <openssl/err.h> 72 73 #include "bn_lcl.h" 74 75 /* This stuff appears to be completely unused, so is deprecated */ 76 #ifndef OPENSSL_NO_DEPRECATED 77 /* For a 32 bit machine 78 * 2 - 4 == 128 79 * 3 - 8 == 256 80 * 4 - 16 == 512 81 * 5 - 32 == 1024 82 * 6 - 64 == 2048 83 * 7 - 128 == 4096 84 * 8 - 256 == 8192 85 */ 86 static int bn_limit_bits = 0; 87 static int bn_limit_num = 8; /* (1<<bn_limit_bits) */ 88 static int bn_limit_bits_low = 0; 89 static int bn_limit_num_low = 8; /* (1<<bn_limit_bits_low) */ 90 static int bn_limit_bits_high = 0; 91 static int bn_limit_num_high = 8; /* (1<<bn_limit_bits_high) */ 92 static int bn_limit_bits_mont = 0; 93 static int bn_limit_num_mont = 8; /* (1<<bn_limit_bits_mont) */ 94 95 void 96 BN_set_params(int mult, int high, int low, int mont) 97 { 98 if (mult >= 0) { 99 if (mult > (int)(sizeof(int) * 8) - 1) 100 mult = sizeof(int) * 8 - 1; 101 bn_limit_bits = mult; 102 bn_limit_num = 1 << mult; 103 } 104 if (high >= 0) { 105 if (high > (int)(sizeof(int) * 8) - 1) 106 high = sizeof(int) * 8 - 1; 107 bn_limit_bits_high = high; 108 bn_limit_num_high = 1 << high; 109 } 110 if (low >= 0) { 111 if (low > (int)(sizeof(int) * 8) - 1) 112 low = sizeof(int) * 8 - 1; 113 bn_limit_bits_low = low; 114 bn_limit_num_low = 1 << low; 115 } 116 if (mont >= 0) { 117 if (mont > (int)(sizeof(int) * 8) - 1) 118 mont = sizeof(int) * 8 - 1; 119 bn_limit_bits_mont = mont; 120 bn_limit_num_mont = 1 << mont; 121 } 122 } 123 124 int 125 BN_get_params(int which) 126 { 127 if (which == 0) 128 return (bn_limit_bits); 129 else if (which == 1) 130 return (bn_limit_bits_high); 131 else if (which == 2) 132 return (bn_limit_bits_low); 133 else if (which == 3) 134 return (bn_limit_bits_mont); 135 else 136 return (0); 137 } 138 #endif 139 140 const BIGNUM * 141 BN_value_one(void) 142 { 143 static const BN_ULONG data_one = 1L; 144 static const BIGNUM const_one = { 145 (BN_ULONG *)&data_one, 1, 1, 0, BN_FLG_STATIC_DATA 146 }; 147 148 return (&const_one); 149 } 150 151 int 152 BN_num_bits_word(BN_ULONG l) 153 { 154 BN_ULONG x, mask; 155 int bits; 156 unsigned int shift; 157 158 /* Constant time calculation of floor(log2(l)) + 1. */ 159 bits = (l != 0); 160 shift = BN_BITS4; /* On _LP64 this is 32, otherwise 16. */ 161 do { 162 x = l >> shift; 163 /* If x is 0, set mask to 0, otherwise set it to all 1s. */ 164 mask = ((~x & (x - 1)) >> (BN_BITS2 - 1)) - 1; 165 bits += shift & mask; 166 /* If x is 0, leave l alone, otherwise set l = x. */ 167 l ^= (x ^ l) & mask; 168 } while ((shift /= 2) != 0); 169 170 return bits; 171 } 172 173 int 174 BN_num_bits(const BIGNUM *a) 175 { 176 int i = a->top - 1; 177 178 bn_check_top(a); 179 180 if (BN_is_zero(a)) 181 return 0; 182 return ((i * BN_BITS2) + BN_num_bits_word(a->d[i])); 183 } 184 185 void 186 BN_clear_free(BIGNUM *a) 187 { 188 int i; 189 190 if (a == NULL) 191 return; 192 bn_check_top(a); 193 if (a->d != NULL && !(BN_get_flags(a, BN_FLG_STATIC_DATA))) 194 freezero(a->d, a->dmax * sizeof(a->d[0])); 195 i = BN_get_flags(a, BN_FLG_MALLOCED); 196 explicit_bzero(a, sizeof(BIGNUM)); 197 if (i) 198 free(a); 199 } 200 201 void 202 BN_free(BIGNUM *a) 203 { 204 BN_clear_free(a); 205 } 206 207 void 208 BN_init(BIGNUM *a) 209 { 210 memset(a, 0, sizeof(BIGNUM)); 211 bn_check_top(a); 212 } 213 214 BIGNUM * 215 BN_new(void) 216 { 217 BIGNUM *ret; 218 219 if ((ret = malloc(sizeof(BIGNUM))) == NULL) { 220 BNerror(ERR_R_MALLOC_FAILURE); 221 return (NULL); 222 } 223 ret->flags = BN_FLG_MALLOCED; 224 ret->top = 0; 225 ret->neg = 0; 226 ret->dmax = 0; 227 ret->d = NULL; 228 bn_check_top(ret); 229 return (ret); 230 } 231 232 /* This is used both by bn_expand2() and bn_dup_expand() */ 233 /* The caller MUST check that words > b->dmax before calling this */ 234 static BN_ULONG * 235 bn_expand_internal(const BIGNUM *b, int words) 236 { 237 BN_ULONG *A, *a = NULL; 238 const BN_ULONG *B; 239 int i; 240 241 bn_check_top(b); 242 243 if (words > (INT_MAX/(4*BN_BITS2))) { 244 BNerror(BN_R_BIGNUM_TOO_LONG); 245 return NULL; 246 } 247 if (BN_get_flags(b, BN_FLG_STATIC_DATA)) { 248 BNerror(BN_R_EXPAND_ON_STATIC_BIGNUM_DATA); 249 return (NULL); 250 } 251 a = A = reallocarray(NULL, words, sizeof(BN_ULONG)); 252 if (A == NULL) { 253 BNerror(ERR_R_MALLOC_FAILURE); 254 return (NULL); 255 } 256 #if 1 257 B = b->d; 258 /* Check if the previous number needs to be copied */ 259 if (B != NULL) { 260 for (i = b->top >> 2; i > 0; i--, A += 4, B += 4) { 261 /* 262 * The fact that the loop is unrolled 263 * 4-wise is a tribute to Intel. It's 264 * the one that doesn't have enough 265 * registers to accommodate more data. 266 * I'd unroll it 8-wise otherwise:-) 267 * 268 * <appro@fy.chalmers.se> 269 */ 270 BN_ULONG a0, a1, a2, a3; 271 a0 = B[0]; 272 a1 = B[1]; 273 a2 = B[2]; 274 a3 = B[3]; 275 A[0] = a0; 276 A[1] = a1; 277 A[2] = a2; 278 A[3] = a3; 279 } 280 switch (b->top & 3) { 281 case 3: 282 A[2] = B[2]; 283 case 2: 284 A[1] = B[1]; 285 case 1: 286 A[0] = B[0]; 287 } 288 } 289 290 #else 291 memset(A, 0, sizeof(BN_ULONG) * words); 292 memcpy(A, b->d, sizeof(b->d[0]) * b->top); 293 #endif 294 295 return (a); 296 } 297 298 /* This is an internal function that can be used instead of bn_expand2() 299 * when there is a need to copy BIGNUMs instead of only expanding the 300 * data part, while still expanding them. 301 * Especially useful when needing to expand BIGNUMs that are declared 302 * 'const' and should therefore not be changed. 303 * The reason to use this instead of a BN_dup() followed by a bn_expand2() 304 * is memory allocation overhead. A BN_dup() followed by a bn_expand2() 305 * will allocate new memory for the BIGNUM data twice, and free it once, 306 * while bn_dup_expand() makes sure allocation is made only once. 307 */ 308 309 #ifndef OPENSSL_NO_DEPRECATED 310 BIGNUM * 311 bn_dup_expand(const BIGNUM *b, int words) 312 { 313 BIGNUM *r = NULL; 314 315 bn_check_top(b); 316 317 /* This function does not work if 318 * words <= b->dmax && top < words 319 * because BN_dup() does not preserve 'dmax'! 320 * (But bn_dup_expand() is not used anywhere yet.) 321 */ 322 323 if (words > b->dmax) { 324 BN_ULONG *a = bn_expand_internal(b, words); 325 326 if (a) { 327 r = BN_new(); 328 if (r) { 329 r->top = b->top; 330 r->dmax = words; 331 r->neg = b->neg; 332 r->d = a; 333 } else { 334 /* r == NULL, BN_new failure */ 335 free(a); 336 } 337 } 338 /* If a == NULL, there was an error in allocation in 339 bn_expand_internal(), and NULL should be returned */ 340 } else { 341 r = BN_dup(b); 342 } 343 344 bn_check_top(r); 345 return r; 346 } 347 #endif 348 349 /* This is an internal function that should not be used in applications. 350 * It ensures that 'b' has enough room for a 'words' word number 351 * and initialises any unused part of b->d with leading zeros. 352 * It is mostly used by the various BIGNUM routines. If there is an error, 353 * NULL is returned. If not, 'b' is returned. */ 354 355 BIGNUM * 356 bn_expand2(BIGNUM *b, int words) 357 { 358 bn_check_top(b); 359 360 if (words > b->dmax) { 361 BN_ULONG *a = bn_expand_internal(b, words); 362 if (!a) 363 return NULL; 364 if (b->d) 365 freezero(b->d, b->dmax * sizeof(b->d[0])); 366 b->d = a; 367 b->dmax = words; 368 } 369 370 /* None of this should be necessary because of what b->top means! */ 371 #if 0 372 /* NB: bn_wexpand() calls this only if the BIGNUM really has to grow */ 373 if (b->top < b->dmax) { 374 int i; 375 BN_ULONG *A = &(b->d[b->top]); 376 for (i = (b->dmax - b->top) >> 3; i > 0; i--, A += 8) { 377 A[0] = 0; 378 A[1] = 0; 379 A[2] = 0; 380 A[3] = 0; 381 A[4] = 0; 382 A[5] = 0; 383 A[6] = 0; 384 A[7] = 0; 385 } 386 for (i = (b->dmax - b->top)&7; i > 0; i--, A++) 387 A[0] = 0; 388 assert(A == &(b->d[b->dmax])); 389 } 390 #endif 391 bn_check_top(b); 392 return b; 393 } 394 395 BIGNUM * 396 BN_dup(const BIGNUM *a) 397 { 398 BIGNUM *t; 399 400 if (a == NULL) 401 return NULL; 402 bn_check_top(a); 403 404 t = BN_new(); 405 if (t == NULL) 406 return NULL; 407 if (!BN_copy(t, a)) { 408 BN_free(t); 409 return NULL; 410 } 411 bn_check_top(t); 412 return t; 413 } 414 415 BIGNUM * 416 BN_copy(BIGNUM *a, const BIGNUM *b) 417 { 418 int i; 419 BN_ULONG *A; 420 const BN_ULONG *B; 421 422 bn_check_top(b); 423 424 if (a == b) 425 return (a); 426 if (bn_wexpand(a, b->top) == NULL) 427 return (NULL); 428 429 #if 1 430 A = a->d; 431 B = b->d; 432 for (i = b->top >> 2; i > 0; i--, A += 4, B += 4) { 433 BN_ULONG a0, a1, a2, a3; 434 a0 = B[0]; 435 a1 = B[1]; 436 a2 = B[2]; 437 a3 = B[3]; 438 A[0] = a0; 439 A[1] = a1; 440 A[2] = a2; 441 A[3] = a3; 442 } 443 switch (b->top & 3) { 444 case 3: 445 A[2] = B[2]; 446 case 2: 447 A[1] = B[1]; 448 case 1: 449 A[0] = B[0]; 450 } 451 #else 452 memcpy(a->d, b->d, sizeof(b->d[0]) * b->top); 453 #endif 454 455 a->top = b->top; 456 a->neg = b->neg; 457 bn_check_top(a); 458 return (a); 459 } 460 461 void 462 BN_swap(BIGNUM *a, BIGNUM *b) 463 { 464 int flags_old_a, flags_old_b; 465 BN_ULONG *tmp_d; 466 int tmp_top, tmp_dmax, tmp_neg; 467 468 bn_check_top(a); 469 bn_check_top(b); 470 471 flags_old_a = a->flags; 472 flags_old_b = b->flags; 473 474 tmp_d = a->d; 475 tmp_top = a->top; 476 tmp_dmax = a->dmax; 477 tmp_neg = a->neg; 478 479 a->d = b->d; 480 a->top = b->top; 481 a->dmax = b->dmax; 482 a->neg = b->neg; 483 484 b->d = tmp_d; 485 b->top = tmp_top; 486 b->dmax = tmp_dmax; 487 b->neg = tmp_neg; 488 489 a->flags = (flags_old_a & BN_FLG_MALLOCED) | 490 (flags_old_b & BN_FLG_STATIC_DATA); 491 b->flags = (flags_old_b & BN_FLG_MALLOCED) | 492 (flags_old_a & BN_FLG_STATIC_DATA); 493 bn_check_top(a); 494 bn_check_top(b); 495 } 496 497 void 498 BN_clear(BIGNUM *a) 499 { 500 bn_check_top(a); 501 if (a->d != NULL) 502 explicit_bzero(a->d, a->dmax * sizeof(a->d[0])); 503 a->top = 0; 504 a->neg = 0; 505 } 506 507 BN_ULONG 508 BN_get_word(const BIGNUM *a) 509 { 510 if (a->top > 1) 511 return BN_MASK2; 512 else if (a->top == 1) 513 return a->d[0]; 514 /* a->top == 0 */ 515 return 0; 516 } 517 518 BIGNUM * 519 bn_expand(BIGNUM *a, int bits) 520 { 521 if (bits > (INT_MAX - BN_BITS2 + 1)) 522 return (NULL); 523 524 if (((bits + BN_BITS2 - 1) / BN_BITS2) <= a->dmax) 525 return (a); 526 527 return bn_expand2(a, (bits + BN_BITS2 - 1) / BN_BITS2); 528 } 529 530 int 531 BN_set_word(BIGNUM *a, BN_ULONG w) 532 { 533 bn_check_top(a); 534 if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL) 535 return (0); 536 a->neg = 0; 537 a->d[0] = w; 538 a->top = (w ? 1 : 0); 539 bn_check_top(a); 540 return (1); 541 } 542 543 BIGNUM * 544 BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret) 545 { 546 unsigned int i, m; 547 unsigned int n; 548 BN_ULONG l; 549 BIGNUM *bn = NULL; 550 551 if (len < 0) 552 return (NULL); 553 if (ret == NULL) 554 ret = bn = BN_new(); 555 if (ret == NULL) 556 return (NULL); 557 bn_check_top(ret); 558 l = 0; 559 n = len; 560 if (n == 0) { 561 ret->top = 0; 562 return (ret); 563 } 564 i = ((n - 1) / BN_BYTES) + 1; 565 m = ((n - 1) % (BN_BYTES)); 566 if (bn_wexpand(ret, (int)i) == NULL) { 567 BN_free(bn); 568 return NULL; 569 } 570 ret->top = i; 571 ret->neg = 0; 572 while (n--) { 573 l = (l << 8L) | *(s++); 574 if (m-- == 0) { 575 ret->d[--i] = l; 576 l = 0; 577 m = BN_BYTES - 1; 578 } 579 } 580 /* need to call this due to clear byte at top if avoiding 581 * having the top bit set (-ve number) */ 582 bn_correct_top(ret); 583 return (ret); 584 } 585 586 /* ignore negative */ 587 int 588 BN_bn2bin(const BIGNUM *a, unsigned char *to) 589 { 590 int n, i; 591 BN_ULONG l; 592 593 bn_check_top(a); 594 n = i=BN_num_bytes(a); 595 while (i--) { 596 l = a->d[i / BN_BYTES]; 597 *(to++) = (unsigned char)(l >> (8 * (i % BN_BYTES))) & 0xff; 598 } 599 return (n); 600 } 601 602 int 603 BN_ucmp(const BIGNUM *a, const BIGNUM *b) 604 { 605 int i; 606 BN_ULONG t1, t2, *ap, *bp; 607 608 bn_check_top(a); 609 bn_check_top(b); 610 611 i = a->top - b->top; 612 if (i != 0) 613 return (i); 614 ap = a->d; 615 bp = b->d; 616 for (i = a->top - 1; i >= 0; i--) { 617 t1 = ap[i]; 618 t2 = bp[i]; 619 if (t1 != t2) 620 return ((t1 > t2) ? 1 : -1); 621 } 622 return (0); 623 } 624 625 int 626 BN_cmp(const BIGNUM *a, const BIGNUM *b) 627 { 628 int i; 629 int gt, lt; 630 BN_ULONG t1, t2; 631 632 if ((a == NULL) || (b == NULL)) { 633 if (a != NULL) 634 return (-1); 635 else if (b != NULL) 636 return (1); 637 else 638 return (0); 639 } 640 641 bn_check_top(a); 642 bn_check_top(b); 643 644 if (a->neg != b->neg) { 645 if (a->neg) 646 return (-1); 647 else 648 return (1); 649 } 650 if (a->neg == 0) { 651 gt = 1; 652 lt = -1; 653 } else { 654 gt = -1; 655 lt = 1; 656 } 657 658 if (a->top > b->top) 659 return (gt); 660 if (a->top < b->top) 661 return (lt); 662 for (i = a->top - 1; i >= 0; i--) { 663 t1 = a->d[i]; 664 t2 = b->d[i]; 665 if (t1 > t2) 666 return (gt); 667 if (t1 < t2) 668 return (lt); 669 } 670 return (0); 671 } 672 673 int 674 BN_set_bit(BIGNUM *a, int n) 675 { 676 int i, j, k; 677 678 if (n < 0) 679 return 0; 680 681 i = n / BN_BITS2; 682 j = n % BN_BITS2; 683 if (a->top <= i) { 684 if (bn_wexpand(a, i + 1) == NULL) 685 return (0); 686 for (k = a->top; k < i + 1; k++) 687 a->d[k] = 0; 688 a->top = i + 1; 689 } 690 691 a->d[i] |= (((BN_ULONG)1) << j); 692 bn_check_top(a); 693 return (1); 694 } 695 696 int 697 BN_clear_bit(BIGNUM *a, int n) 698 { 699 int i, j; 700 701 bn_check_top(a); 702 if (n < 0) 703 return 0; 704 705 i = n / BN_BITS2; 706 j = n % BN_BITS2; 707 if (a->top <= i) 708 return (0); 709 710 a->d[i] &= (~(((BN_ULONG)1) << j)); 711 bn_correct_top(a); 712 return (1); 713 } 714 715 int 716 BN_is_bit_set(const BIGNUM *a, int n) 717 { 718 int i, j; 719 720 bn_check_top(a); 721 if (n < 0) 722 return 0; 723 i = n / BN_BITS2; 724 j = n % BN_BITS2; 725 if (a->top <= i) 726 return 0; 727 return (int)(((a->d[i]) >> j) & ((BN_ULONG)1)); 728 } 729 730 int 731 BN_mask_bits(BIGNUM *a, int n) 732 { 733 int b, w; 734 735 bn_check_top(a); 736 if (n < 0) 737 return 0; 738 739 w = n / BN_BITS2; 740 b = n % BN_BITS2; 741 if (w >= a->top) 742 return 0; 743 if (b == 0) 744 a->top = w; 745 else { 746 a->top = w + 1; 747 a->d[w] &= ~(BN_MASK2 << b); 748 } 749 bn_correct_top(a); 750 return (1); 751 } 752 753 void 754 BN_set_negative(BIGNUM *a, int b) 755 { 756 if (b && !BN_is_zero(a)) 757 a->neg = 1; 758 else 759 a->neg = 0; 760 } 761 762 int 763 bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n) 764 { 765 int i; 766 BN_ULONG aa, bb; 767 768 aa = a[n - 1]; 769 bb = b[n - 1]; 770 if (aa != bb) 771 return ((aa > bb) ? 1 : -1); 772 for (i = n - 2; i >= 0; i--) { 773 aa = a[i]; 774 bb = b[i]; 775 if (aa != bb) 776 return ((aa > bb) ? 1 : -1); 777 } 778 return (0); 779 } 780 781 /* Here follows a specialised variants of bn_cmp_words(). It has the 782 property of performing the operation on arrays of different sizes. 783 The sizes of those arrays is expressed through cl, which is the 784 common length ( basicall, min(len(a),len(b)) ), and dl, which is the 785 delta between the two lengths, calculated as len(a)-len(b). 786 All lengths are the number of BN_ULONGs... */ 787 788 int 789 bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl) 790 { 791 int n, i; 792 793 n = cl - 1; 794 795 if (dl < 0) { 796 for (i = dl; i < 0; i++) { 797 if (b[n - i] != 0) 798 return -1; /* a < b */ 799 } 800 } 801 if (dl > 0) { 802 for (i = dl; i > 0; i--) { 803 if (a[n + i] != 0) 804 return 1; /* a > b */ 805 } 806 } 807 return bn_cmp_words(a, b, cl); 808 } 809 810 /* 811 * Constant-time conditional swap of a and b. 812 * a and b are swapped if condition is not 0. 813 * The code assumes that at most one bit of condition is set. 814 * nwords is the number of words to swap. 815 * The code assumes that at least nwords are allocated in both a and b, 816 * and that no more than nwords are used by either a or b. 817 * a and b cannot be the same number 818 */ 819 void 820 BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords) 821 { 822 BN_ULONG t; 823 int i; 824 825 bn_wcheck_size(a, nwords); 826 bn_wcheck_size(b, nwords); 827 828 assert(a != b); 829 assert((condition & (condition - 1)) == 0); 830 assert(sizeof(BN_ULONG) >= sizeof(int)); 831 832 condition = ((condition - 1) >> (BN_BITS2 - 1)) - 1; 833 834 t = (a->top^b->top) & condition; 835 a->top ^= t; 836 b->top ^= t; 837 838 #define BN_CONSTTIME_SWAP(ind) \ 839 do { \ 840 t = (a->d[ind] ^ b->d[ind]) & condition; \ 841 a->d[ind] ^= t; \ 842 b->d[ind] ^= t; \ 843 } while (0) 844 845 846 switch (nwords) { 847 default: 848 for (i = 10; i < nwords; i++) 849 BN_CONSTTIME_SWAP(i); 850 /* Fallthrough */ 851 case 10: BN_CONSTTIME_SWAP(9); /* Fallthrough */ 852 case 9: BN_CONSTTIME_SWAP(8); /* Fallthrough */ 853 case 8: BN_CONSTTIME_SWAP(7); /* Fallthrough */ 854 case 7: BN_CONSTTIME_SWAP(6); /* Fallthrough */ 855 case 6: BN_CONSTTIME_SWAP(5); /* Fallthrough */ 856 case 5: BN_CONSTTIME_SWAP(4); /* Fallthrough */ 857 case 4: BN_CONSTTIME_SWAP(3); /* Fallthrough */ 858 case 3: BN_CONSTTIME_SWAP(2); /* Fallthrough */ 859 case 2: BN_CONSTTIME_SWAP(1); /* Fallthrough */ 860 case 1: 861 BN_CONSTTIME_SWAP(0); 862 } 863 #undef BN_CONSTTIME_SWAP 864 } 865 866 /* 867 * Constant-time conditional swap of a and b. 868 * a and b are swapped if condition is not 0. 869 * nwords is the number of words to swap. 870 */ 871 int 872 BN_swap_ct(BN_ULONG condition, BIGNUM *a, BIGNUM *b, size_t nwords) 873 { 874 BN_ULONG t; 875 int i, words; 876 877 if (a == b) 878 return 1; 879 if (nwords > INT_MAX) 880 return 0; 881 words = (int)nwords; 882 if (bn_wexpand(a, words) == NULL || bn_wexpand(b, words) == NULL) 883 return 0; 884 if (a->top > words || b->top > words) { 885 BNerror(BN_R_INVALID_LENGTH); 886 return 0; 887 } 888 889 /* Set condition to 0 (if it was zero) or all 1s otherwise. */ 890 condition = ((~condition & (condition - 1)) >> (BN_BITS2 - 1)) - 1; 891 892 /* swap top field */ 893 t = (a->top ^ b->top) & condition; 894 a->top ^= t; 895 b->top ^= t; 896 897 /* swap neg field */ 898 t = (a->neg ^ b->neg) & condition; 899 a->neg ^= t; 900 b->neg ^= t; 901 902 /* swap BN_FLG_CONSTTIME from flag field */ 903 t = ((a->flags ^ b->flags) & BN_FLG_CONSTTIME) & condition; 904 a->flags ^= t; 905 b->flags ^= t; 906 907 /* swap the data */ 908 for (i = 0; i < words; i++) { 909 t = (a->d[i] ^ b->d[i]) & condition; 910 a->d[i] ^= t; 911 b->d[i] ^= t; 912 } 913 914 return 1; 915 } 916 917 BN_GENCB * 918 BN_GENCB_new(void) 919 { 920 BN_GENCB *cb; 921 922 if ((cb = calloc(1, sizeof(*cb))) == NULL) 923 return NULL; 924 925 return cb; 926 } 927 928 void 929 BN_GENCB_free(BN_GENCB *cb) 930 { 931 if (cb == NULL) 932 return; 933 free(cb); 934 } 935 936 void * 937 BN_GENCB_get_arg(BN_GENCB *cb) 938 { 939 return cb->arg; 940 } 941