1 /* 2 * Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved. 3 * 4 * Licensed under the Apache License 2.0 (the "License"). You may not use 5 * this file except in compliance with the License. You can obtain a copy 6 * in the file LICENSE in the source distribution or at 7 * https://www.openssl.org/source/license.html 8 */ 9 10 #include "internal/cryptlib.h" 11 #include "internal/constant_time.h" 12 #include "bn_local.h" 13 14 #include <stdlib.h> 15 #ifdef _WIN32 16 # include <malloc.h> 17 # ifndef alloca 18 # define alloca _alloca 19 # endif 20 #elif defined(__GNUC__) 21 # ifndef alloca 22 # define alloca(s) __builtin_alloca((s)) 23 # endif 24 #elif defined(__sun) 25 # include <alloca.h> 26 #endif 27 28 #include "rsaz_exp.h" 29 30 #undef SPARC_T4_MONT 31 #if defined(OPENSSL_BN_ASM_MONT) && (defined(__sparc__) || defined(__sparc)) 32 # include "crypto/sparc_arch.h" 33 # define SPARC_T4_MONT 34 #endif 35 36 /* maximum precomputation table size for *variable* sliding windows */ 37 #define TABLE_SIZE 32 38 39 /* 40 * Beyond this limit the constant time code is disabled due to 41 * the possible overflow in the computation of powerbufLen in 42 * BN_mod_exp_mont_consttime. 43 * When this limit is exceeded, the computation will be done using 44 * non-constant time code, but it will take very long. 45 */ 46 #define BN_CONSTTIME_SIZE_LIMIT (INT_MAX / BN_BYTES / 256) 47 48 /* this one works - simple but works */ 49 int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx) 50 { 51 int i, bits, ret = 0; 52 BIGNUM *v, *rr; 53 54 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 55 || BN_get_flags(a, BN_FLG_CONSTTIME) != 0) { 56 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ 57 ERR_raise(ERR_LIB_BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); 58 return 0; 59 } 60 61 BN_CTX_start(ctx); 62 rr = ((r == a) || (r == p)) ? BN_CTX_get(ctx) : r; 63 v = BN_CTX_get(ctx); 64 if (rr == NULL || v == NULL) 65 goto err; 66 67 if (BN_copy(v, a) == NULL) 68 goto err; 69 bits = BN_num_bits(p); 70 71 if (BN_is_odd(p)) { 72 if (BN_copy(rr, a) == NULL) 73 goto err; 74 } else { 75 if (!BN_one(rr)) 76 goto err; 77 } 78 79 for (i = 1; i < bits; i++) { 80 if (!BN_sqr(v, v, ctx)) 81 goto err; 82 if (BN_is_bit_set(p, i)) { 83 if (!BN_mul(rr, rr, v, ctx)) 84 goto err; 85 } 86 } 87 if (r != rr && BN_copy(r, rr) == NULL) 88 goto err; 89 90 ret = 1; 91 err: 92 BN_CTX_end(ctx); 93 bn_check_top(r); 94 return ret; 95 } 96 97 int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, 98 BN_CTX *ctx) 99 { 100 int ret; 101 102 bn_check_top(a); 103 bn_check_top(p); 104 bn_check_top(m); 105 106 /*- 107 * For even modulus m = 2^k*m_odd, it might make sense to compute 108 * a^p mod m_odd and a^p mod 2^k separately (with Montgomery 109 * exponentiation for the odd part), using appropriate exponent 110 * reductions, and combine the results using the CRT. 111 * 112 * For now, we use Montgomery only if the modulus is odd; otherwise, 113 * exponentiation using the reciprocal-based quick remaindering 114 * algorithm is used. 115 * 116 * (Timing obtained with expspeed.c [computations a^p mod m 117 * where a, p, m are of the same length: 256, 512, 1024, 2048, 118 * 4096, 8192 bits], compared to the running time of the 119 * standard algorithm: 120 * 121 * BN_mod_exp_mont 33 .. 40 % [AMD K6-2, Linux, debug configuration] 122 * 55 .. 77 % [UltraSparc processor, but 123 * debug-solaris-sparcv8-gcc conf.] 124 * 125 * BN_mod_exp_recp 50 .. 70 % [AMD K6-2, Linux, debug configuration] 126 * 62 .. 118 % [UltraSparc, debug-solaris-sparcv8-gcc] 127 * 128 * On the Sparc, BN_mod_exp_recp was faster than BN_mod_exp_mont 129 * at 2048 and more bits, but at 512 and 1024 bits, it was 130 * slower even than the standard algorithm! 131 * 132 * "Real" timings [linux-elf, solaris-sparcv9-gcc configurations] 133 * should be obtained when the new Montgomery reduction code 134 * has been integrated into OpenSSL.) 135 */ 136 137 #define MONT_MUL_MOD 138 #define MONT_EXP_WORD 139 #define RECP_MUL_MOD 140 141 #ifdef MONT_MUL_MOD 142 if (BN_is_odd(m)) { 143 # ifdef MONT_EXP_WORD 144 if (a->top == 1 && !a->neg 145 && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0) 146 && (BN_get_flags(a, BN_FLG_CONSTTIME) == 0) 147 && (BN_get_flags(m, BN_FLG_CONSTTIME) == 0)) { 148 BN_ULONG A = a->d[0]; 149 ret = BN_mod_exp_mont_word(r, A, p, m, ctx, NULL); 150 } else 151 # endif 152 ret = BN_mod_exp_mont(r, a, p, m, ctx, NULL); 153 } else 154 #endif 155 #ifdef RECP_MUL_MOD 156 { 157 ret = BN_mod_exp_recp(r, a, p, m, ctx); 158 } 159 #else 160 { 161 ret = BN_mod_exp_simple(r, a, p, m, ctx); 162 } 163 #endif 164 165 bn_check_top(r); 166 return ret; 167 } 168 169 int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 170 const BIGNUM *m, BN_CTX *ctx) 171 { 172 int i, j, bits, ret = 0, wstart, wend, window, wvalue; 173 int start = 1; 174 BIGNUM *aa; 175 /* Table of variables obtained from 'ctx' */ 176 BIGNUM *val[TABLE_SIZE]; 177 BN_RECP_CTX recp; 178 179 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 180 || BN_get_flags(a, BN_FLG_CONSTTIME) != 0 181 || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) { 182 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ 183 ERR_raise(ERR_LIB_BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); 184 return 0; 185 } 186 187 bits = BN_num_bits(p); 188 if (bits == 0) { 189 /* x**0 mod 1, or x**0 mod -1 is still zero. */ 190 if (BN_abs_is_word(m, 1)) { 191 ret = 1; 192 BN_zero(r); 193 } else { 194 ret = BN_one(r); 195 } 196 return ret; 197 } 198 199 BN_RECP_CTX_init(&recp); 200 201 BN_CTX_start(ctx); 202 aa = BN_CTX_get(ctx); 203 val[0] = BN_CTX_get(ctx); 204 if (val[0] == NULL) 205 goto err; 206 207 if (m->neg) { 208 /* ignore sign of 'm' */ 209 if (!BN_copy(aa, m)) 210 goto err; 211 aa->neg = 0; 212 if (BN_RECP_CTX_set(&recp, aa, ctx) <= 0) 213 goto err; 214 } else { 215 if (BN_RECP_CTX_set(&recp, m, ctx) <= 0) 216 goto err; 217 } 218 219 if (!BN_nnmod(val[0], a, m, ctx)) 220 goto err; /* 1 */ 221 if (BN_is_zero(val[0])) { 222 BN_zero(r); 223 ret = 1; 224 goto err; 225 } 226 227 window = BN_window_bits_for_exponent_size(bits); 228 if (window > 1) { 229 if (!BN_mod_mul_reciprocal(aa, val[0], val[0], &recp, ctx)) 230 goto err; /* 2 */ 231 j = 1 << (window - 1); 232 for (i = 1; i < j; i++) { 233 if (((val[i] = BN_CTX_get(ctx)) == NULL) || 234 !BN_mod_mul_reciprocal(val[i], val[i - 1], aa, &recp, ctx)) 235 goto err; 236 } 237 } 238 239 start = 1; /* This is used to avoid multiplication etc 240 * when there is only the value '1' in the 241 * buffer. */ 242 wvalue = 0; /* The 'value' of the window */ 243 wstart = bits - 1; /* The top bit of the window */ 244 wend = 0; /* The bottom bit of the window */ 245 246 if (r == p) { 247 BIGNUM *p_dup = BN_CTX_get(ctx); 248 249 if (p_dup == NULL || BN_copy(p_dup, p) == NULL) 250 goto err; 251 p = p_dup; 252 } 253 254 if (!BN_one(r)) 255 goto err; 256 257 for (;;) { 258 if (BN_is_bit_set(p, wstart) == 0) { 259 if (!start) 260 if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx)) 261 goto err; 262 if (wstart == 0) 263 break; 264 wstart--; 265 continue; 266 } 267 /* 268 * We now have wstart on a 'set' bit, we now need to work out how bit 269 * a window to do. To do this we need to scan forward until the last 270 * set bit before the end of the window 271 */ 272 wvalue = 1; 273 wend = 0; 274 for (i = 1; i < window; i++) { 275 if (wstart - i < 0) 276 break; 277 if (BN_is_bit_set(p, wstart - i)) { 278 wvalue <<= (i - wend); 279 wvalue |= 1; 280 wend = i; 281 } 282 } 283 284 /* wend is the size of the current window */ 285 j = wend + 1; 286 /* add the 'bytes above' */ 287 if (!start) 288 for (i = 0; i < j; i++) { 289 if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx)) 290 goto err; 291 } 292 293 /* wvalue will be an odd number < 2^window */ 294 if (!BN_mod_mul_reciprocal(r, r, val[wvalue >> 1], &recp, ctx)) 295 goto err; 296 297 /* move the 'window' down further */ 298 wstart -= wend + 1; 299 wvalue = 0; 300 start = 0; 301 if (wstart < 0) 302 break; 303 } 304 ret = 1; 305 err: 306 BN_CTX_end(ctx); 307 BN_RECP_CTX_free(&recp); 308 bn_check_top(r); 309 return ret; 310 } 311 312 int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, 313 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) 314 { 315 int i, j, bits, ret = 0, wstart, wend, window, wvalue; 316 int start = 1; 317 BIGNUM *d, *r; 318 const BIGNUM *aa; 319 /* Table of variables obtained from 'ctx' */ 320 BIGNUM *val[TABLE_SIZE]; 321 BN_MONT_CTX *mont = NULL; 322 323 bn_check_top(a); 324 bn_check_top(p); 325 bn_check_top(m); 326 327 if (!BN_is_odd(m)) { 328 ERR_raise(ERR_LIB_BN, BN_R_CALLED_WITH_EVEN_MODULUS); 329 return 0; 330 } 331 332 if (m->top <= BN_CONSTTIME_SIZE_LIMIT 333 && (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 334 || BN_get_flags(a, BN_FLG_CONSTTIME) != 0 335 || BN_get_flags(m, BN_FLG_CONSTTIME) != 0)) { 336 return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont); 337 } 338 339 bits = BN_num_bits(p); 340 if (bits == 0) { 341 /* x**0 mod 1, or x**0 mod -1 is still zero. */ 342 if (BN_abs_is_word(m, 1)) { 343 ret = 1; 344 BN_zero(rr); 345 } else { 346 ret = BN_one(rr); 347 } 348 return ret; 349 } 350 351 BN_CTX_start(ctx); 352 d = BN_CTX_get(ctx); 353 r = BN_CTX_get(ctx); 354 val[0] = BN_CTX_get(ctx); 355 if (val[0] == NULL) 356 goto err; 357 358 /* 359 * If this is not done, things will break in the montgomery part 360 */ 361 362 if (in_mont != NULL) 363 mont = in_mont; 364 else { 365 if ((mont = BN_MONT_CTX_new()) == NULL) 366 goto err; 367 if (!BN_MONT_CTX_set(mont, m, ctx)) 368 goto err; 369 } 370 371 if (a->neg || BN_ucmp(a, m) >= 0) { 372 if (!BN_nnmod(val[0], a, m, ctx)) 373 goto err; 374 aa = val[0]; 375 } else 376 aa = a; 377 if (!bn_to_mont_fixed_top(val[0], aa, mont, ctx)) 378 goto err; /* 1 */ 379 380 window = BN_window_bits_for_exponent_size(bits); 381 if (window > 1) { 382 if (!bn_mul_mont_fixed_top(d, val[0], val[0], mont, ctx)) 383 goto err; /* 2 */ 384 j = 1 << (window - 1); 385 for (i = 1; i < j; i++) { 386 if (((val[i] = BN_CTX_get(ctx)) == NULL) || 387 !bn_mul_mont_fixed_top(val[i], val[i - 1], d, mont, ctx)) 388 goto err; 389 } 390 } 391 392 start = 1; /* This is used to avoid multiplication etc 393 * when there is only the value '1' in the 394 * buffer. */ 395 wvalue = 0; /* The 'value' of the window */ 396 wstart = bits - 1; /* The top bit of the window */ 397 wend = 0; /* The bottom bit of the window */ 398 399 #if 1 /* by Shay Gueron's suggestion */ 400 j = m->top; /* borrow j */ 401 if (m->d[j - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) { 402 if (bn_wexpand(r, j) == NULL) 403 goto err; 404 /* 2^(top*BN_BITS2) - m */ 405 r->d[0] = (0 - m->d[0]) & BN_MASK2; 406 for (i = 1; i < j; i++) 407 r->d[i] = (~m->d[i]) & BN_MASK2; 408 r->top = j; 409 r->flags |= BN_FLG_FIXED_TOP; 410 } else 411 #endif 412 if (!bn_to_mont_fixed_top(r, BN_value_one(), mont, ctx)) 413 goto err; 414 for (;;) { 415 if (BN_is_bit_set(p, wstart) == 0) { 416 if (!start) { 417 if (!bn_mul_mont_fixed_top(r, r, r, mont, ctx)) 418 goto err; 419 } 420 if (wstart == 0) 421 break; 422 wstart--; 423 continue; 424 } 425 /* 426 * We now have wstart on a 'set' bit, we now need to work out how bit 427 * a window to do. To do this we need to scan forward until the last 428 * set bit before the end of the window 429 */ 430 wvalue = 1; 431 wend = 0; 432 for (i = 1; i < window; i++) { 433 if (wstart - i < 0) 434 break; 435 if (BN_is_bit_set(p, wstart - i)) { 436 wvalue <<= (i - wend); 437 wvalue |= 1; 438 wend = i; 439 } 440 } 441 442 /* wend is the size of the current window */ 443 j = wend + 1; 444 /* add the 'bytes above' */ 445 if (!start) 446 for (i = 0; i < j; i++) { 447 if (!bn_mul_mont_fixed_top(r, r, r, mont, ctx)) 448 goto err; 449 } 450 451 /* wvalue will be an odd number < 2^window */ 452 if (!bn_mul_mont_fixed_top(r, r, val[wvalue >> 1], mont, ctx)) 453 goto err; 454 455 /* move the 'window' down further */ 456 wstart -= wend + 1; 457 wvalue = 0; 458 start = 0; 459 if (wstart < 0) 460 break; 461 } 462 /* 463 * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery 464 * removes padding [if any] and makes return value suitable for public 465 * API consumer. 466 */ 467 #if defined(SPARC_T4_MONT) 468 if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) { 469 j = mont->N.top; /* borrow j */ 470 val[0]->d[0] = 1; /* borrow val[0] */ 471 for (i = 1; i < j; i++) 472 val[0]->d[i] = 0; 473 val[0]->top = j; 474 if (!BN_mod_mul_montgomery(rr, r, val[0], mont, ctx)) 475 goto err; 476 } else 477 #endif 478 if (!BN_from_montgomery(rr, r, mont, ctx)) 479 goto err; 480 ret = 1; 481 err: 482 if (in_mont == NULL) 483 BN_MONT_CTX_free(mont); 484 BN_CTX_end(ctx); 485 bn_check_top(rr); 486 return ret; 487 } 488 489 static BN_ULONG bn_get_bits(const BIGNUM *a, int bitpos) 490 { 491 BN_ULONG ret = 0; 492 int wordpos; 493 494 wordpos = bitpos / BN_BITS2; 495 bitpos %= BN_BITS2; 496 if (wordpos >= 0 && wordpos < a->top) { 497 ret = a->d[wordpos] & BN_MASK2; 498 if (bitpos) { 499 ret >>= bitpos; 500 if (++wordpos < a->top) 501 ret |= a->d[wordpos] << (BN_BITS2 - bitpos); 502 } 503 } 504 505 return ret & BN_MASK2; 506 } 507 508 /* 509 * BN_mod_exp_mont_consttime() stores the precomputed powers in a specific 510 * layout so that accessing any of these table values shows the same access 511 * pattern as far as cache lines are concerned. The following functions are 512 * used to transfer a BIGNUM from/to that table. 513 */ 514 515 static int MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM *b, int top, 516 unsigned char *buf, int idx, 517 int window) 518 { 519 int i, j; 520 int width = 1 << window; 521 BN_ULONG *table = (BN_ULONG *)buf; 522 523 if (top > b->top) 524 top = b->top; /* this works because 'buf' is explicitly 525 * zeroed */ 526 for (i = 0, j = idx; i < top; i++, j += width) { 527 table[j] = b->d[i]; 528 } 529 530 return 1; 531 } 532 533 static int MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int top, 534 unsigned char *buf, int idx, 535 int window) 536 { 537 int i, j; 538 int width = 1 << window; 539 /* 540 * We declare table 'volatile' in order to discourage compiler 541 * from reordering loads from the table. Concern is that if 542 * reordered in specific manner loads might give away the 543 * information we are trying to conceal. Some would argue that 544 * compiler can reorder them anyway, but it can as well be 545 * argued that doing so would be violation of standard... 546 */ 547 volatile BN_ULONG *table = (volatile BN_ULONG *)buf; 548 549 if (bn_wexpand(b, top) == NULL) 550 return 0; 551 552 if (window <= 3) { 553 for (i = 0; i < top; i++, table += width) { 554 BN_ULONG acc = 0; 555 556 for (j = 0; j < width; j++) { 557 acc |= table[j] & 558 ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1)); 559 } 560 561 b->d[i] = acc; 562 } 563 } else { 564 int xstride = 1 << (window - 2); 565 BN_ULONG y0, y1, y2, y3; 566 567 i = idx >> (window - 2); /* equivalent of idx / xstride */ 568 idx &= xstride - 1; /* equivalent of idx % xstride */ 569 570 y0 = (BN_ULONG)0 - (constant_time_eq_int(i,0)&1); 571 y1 = (BN_ULONG)0 - (constant_time_eq_int(i,1)&1); 572 y2 = (BN_ULONG)0 - (constant_time_eq_int(i,2)&1); 573 y3 = (BN_ULONG)0 - (constant_time_eq_int(i,3)&1); 574 575 for (i = 0; i < top; i++, table += width) { 576 BN_ULONG acc = 0; 577 578 for (j = 0; j < xstride; j++) { 579 acc |= ( (table[j + 0 * xstride] & y0) | 580 (table[j + 1 * xstride] & y1) | 581 (table[j + 2 * xstride] & y2) | 582 (table[j + 3 * xstride] & y3) ) 583 & ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1)); 584 } 585 586 b->d[i] = acc; 587 } 588 } 589 590 b->top = top; 591 b->flags |= BN_FLG_FIXED_TOP; 592 return 1; 593 } 594 595 /* 596 * Given a pointer value, compute the next address that is a cache line 597 * multiple. 598 */ 599 #define MOD_EXP_CTIME_ALIGN(x_) \ 600 ((unsigned char*)(x_) + (MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH - (((size_t)(x_)) & (MOD_EXP_CTIME_MIN_CACHE_LINE_MASK)))) 601 602 /* 603 * This variant of BN_mod_exp_mont() uses fixed windows and the special 604 * precomputation memory layout to limit data-dependency to a minimum to 605 * protect secret exponents (cf. the hyper-threading timing attacks pointed 606 * out by Colin Percival, 607 * http://www.daemonology.net/hyperthreading-considered-harmful/) 608 */ 609 int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, 610 const BIGNUM *m, BN_CTX *ctx, 611 BN_MONT_CTX *in_mont) 612 { 613 int i, bits, ret = 0, window, wvalue, wmask, window0; 614 int top; 615 BN_MONT_CTX *mont = NULL; 616 617 int numPowers; 618 unsigned char *powerbufFree = NULL; 619 int powerbufLen = 0; 620 unsigned char *powerbuf = NULL; 621 BIGNUM tmp, am; 622 #if defined(SPARC_T4_MONT) 623 unsigned int t4 = 0; 624 #endif 625 626 bn_check_top(a); 627 bn_check_top(p); 628 bn_check_top(m); 629 630 if (!BN_is_odd(m)) { 631 ERR_raise(ERR_LIB_BN, BN_R_CALLED_WITH_EVEN_MODULUS); 632 return 0; 633 } 634 635 top = m->top; 636 637 if (top > BN_CONSTTIME_SIZE_LIMIT) { 638 /* Prevent overflowing the powerbufLen computation below */ 639 return BN_mod_exp_mont(rr, a, p, m, ctx, in_mont); 640 } 641 642 /* 643 * Use all bits stored in |p|, rather than |BN_num_bits|, so we do not leak 644 * whether the top bits are zero. 645 */ 646 bits = p->top * BN_BITS2; 647 if (bits == 0) { 648 /* x**0 mod 1, or x**0 mod -1 is still zero. */ 649 if (BN_abs_is_word(m, 1)) { 650 ret = 1; 651 BN_zero(rr); 652 } else { 653 ret = BN_one(rr); 654 } 655 return ret; 656 } 657 658 BN_CTX_start(ctx); 659 660 /* 661 * Allocate a montgomery context if it was not supplied by the caller. If 662 * this is not done, things will break in the montgomery part. 663 */ 664 if (in_mont != NULL) 665 mont = in_mont; 666 else { 667 if ((mont = BN_MONT_CTX_new()) == NULL) 668 goto err; 669 if (!BN_MONT_CTX_set(mont, m, ctx)) 670 goto err; 671 } 672 673 if (a->neg || BN_ucmp(a, m) >= 0) { 674 BIGNUM *reduced = BN_CTX_get(ctx); 675 if (reduced == NULL 676 || !BN_nnmod(reduced, a, m, ctx)) { 677 goto err; 678 } 679 a = reduced; 680 } 681 682 #ifdef RSAZ_ENABLED 683 /* 684 * If the size of the operands allow it, perform the optimized 685 * RSAZ exponentiation. For further information see 686 * crypto/bn/rsaz_exp.c and accompanying assembly modules. 687 */ 688 if ((16 == a->top) && (16 == p->top) && (BN_num_bits(m) == 1024) 689 && rsaz_avx2_eligible()) { 690 if (NULL == bn_wexpand(rr, 16)) 691 goto err; 692 RSAZ_1024_mod_exp_avx2(rr->d, a->d, p->d, m->d, mont->RR.d, 693 mont->n0[0]); 694 rr->top = 16; 695 rr->neg = 0; 696 bn_correct_top(rr); 697 ret = 1; 698 goto err; 699 } else if ((8 == a->top) && (8 == p->top) && (BN_num_bits(m) == 512)) { 700 if (NULL == bn_wexpand(rr, 8)) 701 goto err; 702 RSAZ_512_mod_exp(rr->d, a->d, p->d, m->d, mont->n0[0], mont->RR.d); 703 rr->top = 8; 704 rr->neg = 0; 705 bn_correct_top(rr); 706 ret = 1; 707 goto err; 708 } 709 #endif 710 711 /* Get the window size to use with size of p. */ 712 window = BN_window_bits_for_ctime_exponent_size(bits); 713 #if defined(SPARC_T4_MONT) 714 if (window >= 5 && (top & 15) == 0 && top <= 64 && 715 (OPENSSL_sparcv9cap_P[1] & (CFR_MONTMUL | CFR_MONTSQR)) == 716 (CFR_MONTMUL | CFR_MONTSQR) && (t4 = OPENSSL_sparcv9cap_P[0])) 717 window = 5; 718 else 719 #endif 720 #if defined(OPENSSL_BN_ASM_MONT5) 721 if (window >= 5 && top <= BN_SOFT_LIMIT) { 722 window = 5; /* ~5% improvement for RSA2048 sign, and even 723 * for RSA4096 */ 724 /* reserve space for mont->N.d[] copy */ 725 powerbufLen += top * sizeof(mont->N.d[0]); 726 } 727 #endif 728 (void)0; 729 730 /* 731 * Allocate a buffer large enough to hold all of the pre-computed powers 732 * of am, am itself and tmp. 733 */ 734 numPowers = 1 << window; 735 powerbufLen += sizeof(m->d[0]) * (top * numPowers + 736 ((2 * top) > 737 numPowers ? (2 * top) : numPowers)); 738 #ifdef alloca 739 if (powerbufLen < 3072) 740 powerbufFree = 741 alloca(powerbufLen + MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH); 742 else 743 #endif 744 if ((powerbufFree = 745 OPENSSL_malloc(powerbufLen + MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH)) 746 == NULL) 747 goto err; 748 749 powerbuf = MOD_EXP_CTIME_ALIGN(powerbufFree); 750 memset(powerbuf, 0, powerbufLen); 751 752 #ifdef alloca 753 if (powerbufLen < 3072) 754 powerbufFree = NULL; 755 #endif 756 757 /* lay down tmp and am right after powers table */ 758 tmp.d = (BN_ULONG *)(powerbuf + sizeof(m->d[0]) * top * numPowers); 759 am.d = tmp.d + top; 760 tmp.top = am.top = 0; 761 tmp.dmax = am.dmax = top; 762 tmp.neg = am.neg = 0; 763 tmp.flags = am.flags = BN_FLG_STATIC_DATA; 764 765 /* prepare a^0 in Montgomery domain */ 766 #if 1 /* by Shay Gueron's suggestion */ 767 if (m->d[top - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) { 768 /* 2^(top*BN_BITS2) - m */ 769 tmp.d[0] = (0 - m->d[0]) & BN_MASK2; 770 for (i = 1; i < top; i++) 771 tmp.d[i] = (~m->d[i]) & BN_MASK2; 772 tmp.top = top; 773 } else 774 #endif 775 if (!bn_to_mont_fixed_top(&tmp, BN_value_one(), mont, ctx)) 776 goto err; 777 778 /* prepare a^1 in Montgomery domain */ 779 if (!bn_to_mont_fixed_top(&am, a, mont, ctx)) 780 goto err; 781 782 if (top > BN_SOFT_LIMIT) 783 goto fallback; 784 785 #if defined(SPARC_T4_MONT) 786 if (t4) { 787 typedef int (*bn_pwr5_mont_f) (BN_ULONG *tp, const BN_ULONG *np, 788 const BN_ULONG *n0, const void *table, 789 int power, int bits); 790 int bn_pwr5_mont_t4_8(BN_ULONG *tp, const BN_ULONG *np, 791 const BN_ULONG *n0, const void *table, 792 int power, int bits); 793 int bn_pwr5_mont_t4_16(BN_ULONG *tp, const BN_ULONG *np, 794 const BN_ULONG *n0, const void *table, 795 int power, int bits); 796 int bn_pwr5_mont_t4_24(BN_ULONG *tp, const BN_ULONG *np, 797 const BN_ULONG *n0, const void *table, 798 int power, int bits); 799 int bn_pwr5_mont_t4_32(BN_ULONG *tp, const BN_ULONG *np, 800 const BN_ULONG *n0, const void *table, 801 int power, int bits); 802 static const bn_pwr5_mont_f pwr5_funcs[4] = { 803 bn_pwr5_mont_t4_8, bn_pwr5_mont_t4_16, 804 bn_pwr5_mont_t4_24, bn_pwr5_mont_t4_32 805 }; 806 bn_pwr5_mont_f pwr5_worker = pwr5_funcs[top / 16 - 1]; 807 808 typedef int (*bn_mul_mont_f) (BN_ULONG *rp, const BN_ULONG *ap, 809 const void *bp, const BN_ULONG *np, 810 const BN_ULONG *n0); 811 int bn_mul_mont_t4_8(BN_ULONG *rp, const BN_ULONG *ap, const void *bp, 812 const BN_ULONG *np, const BN_ULONG *n0); 813 int bn_mul_mont_t4_16(BN_ULONG *rp, const BN_ULONG *ap, 814 const void *bp, const BN_ULONG *np, 815 const BN_ULONG *n0); 816 int bn_mul_mont_t4_24(BN_ULONG *rp, const BN_ULONG *ap, 817 const void *bp, const BN_ULONG *np, 818 const BN_ULONG *n0); 819 int bn_mul_mont_t4_32(BN_ULONG *rp, const BN_ULONG *ap, 820 const void *bp, const BN_ULONG *np, 821 const BN_ULONG *n0); 822 static const bn_mul_mont_f mul_funcs[4] = { 823 bn_mul_mont_t4_8, bn_mul_mont_t4_16, 824 bn_mul_mont_t4_24, bn_mul_mont_t4_32 825 }; 826 bn_mul_mont_f mul_worker = mul_funcs[top / 16 - 1]; 827 828 void bn_mul_mont_vis3(BN_ULONG *rp, const BN_ULONG *ap, 829 const void *bp, const BN_ULONG *np, 830 const BN_ULONG *n0, int num); 831 void bn_mul_mont_t4(BN_ULONG *rp, const BN_ULONG *ap, 832 const void *bp, const BN_ULONG *np, 833 const BN_ULONG *n0, int num); 834 void bn_mul_mont_gather5_t4(BN_ULONG *rp, const BN_ULONG *ap, 835 const void *table, const BN_ULONG *np, 836 const BN_ULONG *n0, int num, int power); 837 void bn_flip_n_scatter5_t4(const BN_ULONG *inp, size_t num, 838 void *table, size_t power); 839 void bn_gather5_t4(BN_ULONG *out, size_t num, 840 void *table, size_t power); 841 void bn_flip_t4(BN_ULONG *dst, BN_ULONG *src, size_t num); 842 843 BN_ULONG *np = mont->N.d, *n0 = mont->n0; 844 int stride = 5 * (6 - (top / 16 - 1)); /* multiple of 5, but less 845 * than 32 */ 846 847 /* 848 * BN_to_montgomery can contaminate words above .top [in 849 * BN_DEBUG build... 850 */ 851 for (i = am.top; i < top; i++) 852 am.d[i] = 0; 853 for (i = tmp.top; i < top; i++) 854 tmp.d[i] = 0; 855 856 bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 0); 857 bn_flip_n_scatter5_t4(am.d, top, powerbuf, 1); 858 if (!(*mul_worker) (tmp.d, am.d, am.d, np, n0) && 859 !(*mul_worker) (tmp.d, am.d, am.d, np, n0)) 860 bn_mul_mont_vis3(tmp.d, am.d, am.d, np, n0, top); 861 bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 2); 862 863 for (i = 3; i < 32; i++) { 864 /* Calculate a^i = a^(i-1) * a */ 865 if (!(*mul_worker) (tmp.d, tmp.d, am.d, np, n0) && 866 !(*mul_worker) (tmp.d, tmp.d, am.d, np, n0)) 867 bn_mul_mont_vis3(tmp.d, tmp.d, am.d, np, n0, top); 868 bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, i); 869 } 870 871 /* switch to 64-bit domain */ 872 np = alloca(top * sizeof(BN_ULONG)); 873 top /= 2; 874 bn_flip_t4(np, mont->N.d, top); 875 876 /* 877 * The exponent may not have a whole number of fixed-size windows. 878 * To simplify the main loop, the initial window has between 1 and 879 * full-window-size bits such that what remains is always a whole 880 * number of windows 881 */ 882 window0 = (bits - 1) % 5 + 1; 883 wmask = (1 << window0) - 1; 884 bits -= window0; 885 wvalue = bn_get_bits(p, bits) & wmask; 886 bn_gather5_t4(tmp.d, top, powerbuf, wvalue); 887 888 /* 889 * Scan the exponent one window at a time starting from the most 890 * significant bits. 891 */ 892 while (bits > 0) { 893 if (bits < stride) 894 stride = bits; 895 bits -= stride; 896 wvalue = bn_get_bits(p, bits); 897 898 if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride)) 899 continue; 900 /* retry once and fall back */ 901 if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride)) 902 continue; 903 904 bits += stride - 5; 905 wvalue >>= stride - 5; 906 wvalue &= 31; 907 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); 908 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); 909 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); 910 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); 911 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top); 912 bn_mul_mont_gather5_t4(tmp.d, tmp.d, powerbuf, np, n0, top, 913 wvalue); 914 } 915 916 bn_flip_t4(tmp.d, tmp.d, top); 917 top *= 2; 918 /* back to 32-bit domain */ 919 tmp.top = top; 920 bn_correct_top(&tmp); 921 OPENSSL_cleanse(np, top * sizeof(BN_ULONG)); 922 } else 923 #endif 924 #if defined(OPENSSL_BN_ASM_MONT5) 925 if (window == 5 && top > 1) { 926 /* 927 * This optimization uses ideas from https://eprint.iacr.org/2011/239, 928 * specifically optimization of cache-timing attack countermeasures, 929 * pre-computation optimization, and Almost Montgomery Multiplication. 930 * 931 * The paper discusses a 4-bit window to optimize 512-bit modular 932 * exponentiation, used in RSA-1024 with CRT, but RSA-1024 is no longer 933 * important. 934 * 935 * |bn_mul_mont_gather5| and |bn_power5| implement the "almost" 936 * reduction variant, so the values here may not be fully reduced. 937 * They are bounded by R (i.e. they fit in |top| words), not |m|. 938 * Additionally, we pass these "almost" reduced inputs into 939 * |bn_mul_mont|, which implements the normal reduction variant. 940 * Given those inputs, |bn_mul_mont| may not give reduced 941 * output, but it will still produce "almost" reduced output. 942 */ 943 void bn_mul_mont_gather5(BN_ULONG *rp, const BN_ULONG *ap, 944 const void *table, const BN_ULONG *np, 945 const BN_ULONG *n0, int num, int power); 946 void bn_scatter5(const BN_ULONG *inp, size_t num, 947 void *table, size_t power); 948 void bn_gather5(BN_ULONG *out, size_t num, void *table, size_t power); 949 void bn_power5(BN_ULONG *rp, const BN_ULONG *ap, 950 const void *table, const BN_ULONG *np, 951 const BN_ULONG *n0, int num, int power); 952 int bn_get_bits5(const BN_ULONG *ap, int off); 953 954 BN_ULONG *n0 = mont->n0, *np; 955 956 /* 957 * BN_to_montgomery can contaminate words above .top [in 958 * BN_DEBUG build... 959 */ 960 for (i = am.top; i < top; i++) 961 am.d[i] = 0; 962 for (i = tmp.top; i < top; i++) 963 tmp.d[i] = 0; 964 965 /* 966 * copy mont->N.d[] to improve cache locality 967 */ 968 for (np = am.d + top, i = 0; i < top; i++) 969 np[i] = mont->N.d[i]; 970 971 bn_scatter5(tmp.d, top, powerbuf, 0); 972 bn_scatter5(am.d, am.top, powerbuf, 1); 973 bn_mul_mont(tmp.d, am.d, am.d, np, n0, top); 974 bn_scatter5(tmp.d, top, powerbuf, 2); 975 976 # if 0 977 for (i = 3; i < 32; i++) { 978 /* Calculate a^i = a^(i-1) * a */ 979 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1); 980 bn_scatter5(tmp.d, top, powerbuf, i); 981 } 982 # else 983 /* same as above, but uses squaring for 1/2 of operations */ 984 for (i = 4; i < 32; i *= 2) { 985 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); 986 bn_scatter5(tmp.d, top, powerbuf, i); 987 } 988 for (i = 3; i < 8; i += 2) { 989 int j; 990 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1); 991 bn_scatter5(tmp.d, top, powerbuf, i); 992 for (j = 2 * i; j < 32; j *= 2) { 993 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); 994 bn_scatter5(tmp.d, top, powerbuf, j); 995 } 996 } 997 for (; i < 16; i += 2) { 998 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1); 999 bn_scatter5(tmp.d, top, powerbuf, i); 1000 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); 1001 bn_scatter5(tmp.d, top, powerbuf, 2 * i); 1002 } 1003 for (; i < 32; i += 2) { 1004 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1); 1005 bn_scatter5(tmp.d, top, powerbuf, i); 1006 } 1007 # endif 1008 /* 1009 * The exponent may not have a whole number of fixed-size windows. 1010 * To simplify the main loop, the initial window has between 1 and 1011 * full-window-size bits such that what remains is always a whole 1012 * number of windows 1013 */ 1014 window0 = (bits - 1) % 5 + 1; 1015 wmask = (1 << window0) - 1; 1016 bits -= window0; 1017 wvalue = bn_get_bits(p, bits) & wmask; 1018 bn_gather5(tmp.d, top, powerbuf, wvalue); 1019 1020 /* 1021 * Scan the exponent one window at a time starting from the most 1022 * significant bits. 1023 */ 1024 if (top & 7) { 1025 while (bits > 0) { 1026 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); 1027 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); 1028 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); 1029 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); 1030 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top); 1031 bn_mul_mont_gather5(tmp.d, tmp.d, powerbuf, np, n0, top, 1032 bn_get_bits5(p->d, bits -= 5)); 1033 } 1034 } else { 1035 while (bits > 0) { 1036 bn_power5(tmp.d, tmp.d, powerbuf, np, n0, top, 1037 bn_get_bits5(p->d, bits -= 5)); 1038 } 1039 } 1040 1041 tmp.top = top; 1042 /* 1043 * The result is now in |tmp| in Montgomery form, but it may not be 1044 * fully reduced. This is within bounds for |BN_from_montgomery| 1045 * (tmp < R <= m*R) so it will, when converting from Montgomery form, 1046 * produce a fully reduced result. 1047 * 1048 * This differs from Figure 2 of the paper, which uses AMM(h, 1) to 1049 * convert from Montgomery form with unreduced output, followed by an 1050 * extra reduction step. In the paper's terminology, we replace 1051 * steps 9 and 10 with MM(h, 1). 1052 */ 1053 } else 1054 #endif 1055 { 1056 fallback: 1057 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0, window)) 1058 goto err; 1059 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&am, top, powerbuf, 1, window)) 1060 goto err; 1061 1062 /* 1063 * If the window size is greater than 1, then calculate 1064 * val[i=2..2^winsize-1]. Powers are computed as a*a^(i-1) (even 1065 * powers could instead be computed as (a^(i/2))^2 to use the slight 1066 * performance advantage of sqr over mul). 1067 */ 1068 if (window > 1) { 1069 if (!bn_mul_mont_fixed_top(&tmp, &am, &am, mont, ctx)) 1070 goto err; 1071 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 2, 1072 window)) 1073 goto err; 1074 for (i = 3; i < numPowers; i++) { 1075 /* Calculate a^i = a^(i-1) * a */ 1076 if (!bn_mul_mont_fixed_top(&tmp, &am, &tmp, mont, ctx)) 1077 goto err; 1078 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, i, 1079 window)) 1080 goto err; 1081 } 1082 } 1083 1084 /* 1085 * The exponent may not have a whole number of fixed-size windows. 1086 * To simplify the main loop, the initial window has between 1 and 1087 * full-window-size bits such that what remains is always a whole 1088 * number of windows 1089 */ 1090 window0 = (bits - 1) % window + 1; 1091 wmask = (1 << window0) - 1; 1092 bits -= window0; 1093 wvalue = bn_get_bits(p, bits) & wmask; 1094 if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&tmp, top, powerbuf, wvalue, 1095 window)) 1096 goto err; 1097 1098 wmask = (1 << window) - 1; 1099 /* 1100 * Scan the exponent one window at a time starting from the most 1101 * significant bits. 1102 */ 1103 while (bits > 0) { 1104 1105 /* Square the result window-size times */ 1106 for (i = 0; i < window; i++) 1107 if (!bn_mul_mont_fixed_top(&tmp, &tmp, &tmp, mont, ctx)) 1108 goto err; 1109 1110 /* 1111 * Get a window's worth of bits from the exponent 1112 * This avoids calling BN_is_bit_set for each bit, which 1113 * is not only slower but also makes each bit vulnerable to 1114 * EM (and likely other) side-channel attacks like One&Done 1115 * (for details see "One&Done: A Single-Decryption EM-Based 1116 * Attack on OpenSSL's Constant-Time Blinded RSA" by M. Alam, 1117 * H. Khan, M. Dey, N. Sinha, R. Callan, A. Zajic, and 1118 * M. Prvulovic, in USENIX Security'18) 1119 */ 1120 bits -= window; 1121 wvalue = bn_get_bits(p, bits) & wmask; 1122 /* 1123 * Fetch the appropriate pre-computed value from the pre-buf 1124 */ 1125 if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&am, top, powerbuf, wvalue, 1126 window)) 1127 goto err; 1128 1129 /* Multiply the result into the intermediate result */ 1130 if (!bn_mul_mont_fixed_top(&tmp, &tmp, &am, mont, ctx)) 1131 goto err; 1132 } 1133 } 1134 1135 /* 1136 * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery 1137 * removes padding [if any] and makes return value suitable for public 1138 * API consumer. 1139 */ 1140 #if defined(SPARC_T4_MONT) 1141 if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) { 1142 am.d[0] = 1; /* borrow am */ 1143 for (i = 1; i < top; i++) 1144 am.d[i] = 0; 1145 if (!BN_mod_mul_montgomery(rr, &tmp, &am, mont, ctx)) 1146 goto err; 1147 } else 1148 #endif 1149 if (!BN_from_montgomery(rr, &tmp, mont, ctx)) 1150 goto err; 1151 ret = 1; 1152 err: 1153 if (in_mont == NULL) 1154 BN_MONT_CTX_free(mont); 1155 if (powerbuf != NULL) { 1156 OPENSSL_cleanse(powerbuf, powerbufLen); 1157 OPENSSL_free(powerbufFree); 1158 } 1159 BN_CTX_end(ctx); 1160 return ret; 1161 } 1162 1163 int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p, 1164 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) 1165 { 1166 BN_MONT_CTX *mont = NULL; 1167 int b, bits, ret = 0; 1168 int r_is_one; 1169 BN_ULONG w, next_w; 1170 BIGNUM *r, *t; 1171 BIGNUM *swap_tmp; 1172 #define BN_MOD_MUL_WORD(r, w, m) \ 1173 (BN_mul_word(r, (w)) && \ 1174 (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \ 1175 (BN_mod(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1)))) 1176 /* 1177 * BN_MOD_MUL_WORD is only used with 'w' large, so the BN_ucmp test is 1178 * probably more overhead than always using BN_mod (which uses BN_copy if 1179 * a similar test returns true). 1180 */ 1181 /* 1182 * We can use BN_mod and do not need BN_nnmod because our accumulator is 1183 * never negative (the result of BN_mod does not depend on the sign of 1184 * the modulus). 1185 */ 1186 #define BN_TO_MONTGOMERY_WORD(r, w, mont) \ 1187 (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx)) 1188 1189 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 1190 || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) { 1191 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ 1192 ERR_raise(ERR_LIB_BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); 1193 return 0; 1194 } 1195 1196 bn_check_top(p); 1197 bn_check_top(m); 1198 1199 if (!BN_is_odd(m)) { 1200 ERR_raise(ERR_LIB_BN, BN_R_CALLED_WITH_EVEN_MODULUS); 1201 return 0; 1202 } 1203 if (m->top == 1) 1204 a %= m->d[0]; /* make sure that 'a' is reduced */ 1205 1206 bits = BN_num_bits(p); 1207 if (bits == 0) { 1208 /* x**0 mod 1, or x**0 mod -1 is still zero. */ 1209 if (BN_abs_is_word(m, 1)) { 1210 ret = 1; 1211 BN_zero(rr); 1212 } else { 1213 ret = BN_one(rr); 1214 } 1215 return ret; 1216 } 1217 if (a == 0) { 1218 BN_zero(rr); 1219 ret = 1; 1220 return ret; 1221 } 1222 1223 BN_CTX_start(ctx); 1224 r = BN_CTX_get(ctx); 1225 t = BN_CTX_get(ctx); 1226 if (t == NULL) 1227 goto err; 1228 1229 if (in_mont != NULL) 1230 mont = in_mont; 1231 else { 1232 if ((mont = BN_MONT_CTX_new()) == NULL) 1233 goto err; 1234 if (!BN_MONT_CTX_set(mont, m, ctx)) 1235 goto err; 1236 } 1237 1238 r_is_one = 1; /* except for Montgomery factor */ 1239 1240 /* bits-1 >= 0 */ 1241 1242 /* The result is accumulated in the product r*w. */ 1243 w = a; /* bit 'bits-1' of 'p' is always set */ 1244 for (b = bits - 2; b >= 0; b--) { 1245 /* First, square r*w. */ 1246 next_w = w * w; 1247 if ((next_w / w) != w) { /* overflow */ 1248 if (r_is_one) { 1249 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) 1250 goto err; 1251 r_is_one = 0; 1252 } else { 1253 if (!BN_MOD_MUL_WORD(r, w, m)) 1254 goto err; 1255 } 1256 next_w = 1; 1257 } 1258 w = next_w; 1259 if (!r_is_one) { 1260 if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) 1261 goto err; 1262 } 1263 1264 /* Second, multiply r*w by 'a' if exponent bit is set. */ 1265 if (BN_is_bit_set(p, b)) { 1266 next_w = w * a; 1267 if ((next_w / a) != w) { /* overflow */ 1268 if (r_is_one) { 1269 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) 1270 goto err; 1271 r_is_one = 0; 1272 } else { 1273 if (!BN_MOD_MUL_WORD(r, w, m)) 1274 goto err; 1275 } 1276 next_w = a; 1277 } 1278 w = next_w; 1279 } 1280 } 1281 1282 /* Finally, set r:=r*w. */ 1283 if (w != 1) { 1284 if (r_is_one) { 1285 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) 1286 goto err; 1287 r_is_one = 0; 1288 } else { 1289 if (!BN_MOD_MUL_WORD(r, w, m)) 1290 goto err; 1291 } 1292 } 1293 1294 if (r_is_one) { /* can happen only if a == 1 */ 1295 if (!BN_one(rr)) 1296 goto err; 1297 } else { 1298 if (!BN_from_montgomery(rr, r, mont, ctx)) 1299 goto err; 1300 } 1301 ret = 1; 1302 err: 1303 if (in_mont == NULL) 1304 BN_MONT_CTX_free(mont); 1305 BN_CTX_end(ctx); 1306 bn_check_top(rr); 1307 return ret; 1308 } 1309 1310 /* The old fallback, simple version :-) */ 1311 int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 1312 const BIGNUM *m, BN_CTX *ctx) 1313 { 1314 int i, j, bits, ret = 0, wstart, wend, window, wvalue; 1315 int start = 1; 1316 BIGNUM *d; 1317 /* Table of variables obtained from 'ctx' */ 1318 BIGNUM *val[TABLE_SIZE]; 1319 1320 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0 1321 || BN_get_flags(a, BN_FLG_CONSTTIME) != 0 1322 || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) { 1323 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */ 1324 ERR_raise(ERR_LIB_BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); 1325 return 0; 1326 } 1327 1328 if (r == m) { 1329 ERR_raise(ERR_LIB_BN, ERR_R_PASSED_INVALID_ARGUMENT); 1330 return 0; 1331 } 1332 1333 bits = BN_num_bits(p); 1334 if (bits == 0) { 1335 /* x**0 mod 1, or x**0 mod -1 is still zero. */ 1336 if (BN_abs_is_word(m, 1)) { 1337 ret = 1; 1338 BN_zero(r); 1339 } else { 1340 ret = BN_one(r); 1341 } 1342 return ret; 1343 } 1344 1345 BN_CTX_start(ctx); 1346 d = BN_CTX_get(ctx); 1347 val[0] = BN_CTX_get(ctx); 1348 if (val[0] == NULL) 1349 goto err; 1350 1351 if (!BN_nnmod(val[0], a, m, ctx)) 1352 goto err; /* 1 */ 1353 if (BN_is_zero(val[0])) { 1354 BN_zero(r); 1355 ret = 1; 1356 goto err; 1357 } 1358 1359 window = BN_window_bits_for_exponent_size(bits); 1360 if (window > 1) { 1361 if (!BN_mod_mul(d, val[0], val[0], m, ctx)) 1362 goto err; /* 2 */ 1363 j = 1 << (window - 1); 1364 for (i = 1; i < j; i++) { 1365 if (((val[i] = BN_CTX_get(ctx)) == NULL) || 1366 !BN_mod_mul(val[i], val[i - 1], d, m, ctx)) 1367 goto err; 1368 } 1369 } 1370 1371 start = 1; /* This is used to avoid multiplication etc 1372 * when there is only the value '1' in the 1373 * buffer. */ 1374 wvalue = 0; /* The 'value' of the window */ 1375 wstart = bits - 1; /* The top bit of the window */ 1376 wend = 0; /* The bottom bit of the window */ 1377 1378 if (r == p) { 1379 BIGNUM *p_dup = BN_CTX_get(ctx); 1380 1381 if (p_dup == NULL || BN_copy(p_dup, p) == NULL) 1382 goto err; 1383 p = p_dup; 1384 } 1385 1386 if (!BN_one(r)) 1387 goto err; 1388 1389 for (;;) { 1390 if (BN_is_bit_set(p, wstart) == 0) { 1391 if (!start) 1392 if (!BN_mod_mul(r, r, r, m, ctx)) 1393 goto err; 1394 if (wstart == 0) 1395 break; 1396 wstart--; 1397 continue; 1398 } 1399 /* 1400 * We now have wstart on a 'set' bit, we now need to work out how bit 1401 * a window to do. To do this we need to scan forward until the last 1402 * set bit before the end of the window 1403 */ 1404 wvalue = 1; 1405 wend = 0; 1406 for (i = 1; i < window; i++) { 1407 if (wstart - i < 0) 1408 break; 1409 if (BN_is_bit_set(p, wstart - i)) { 1410 wvalue <<= (i - wend); 1411 wvalue |= 1; 1412 wend = i; 1413 } 1414 } 1415 1416 /* wend is the size of the current window */ 1417 j = wend + 1; 1418 /* add the 'bytes above' */ 1419 if (!start) 1420 for (i = 0; i < j; i++) { 1421 if (!BN_mod_mul(r, r, r, m, ctx)) 1422 goto err; 1423 } 1424 1425 /* wvalue will be an odd number < 2^window */ 1426 if (!BN_mod_mul(r, r, val[wvalue >> 1], m, ctx)) 1427 goto err; 1428 1429 /* move the 'window' down further */ 1430 wstart -= wend + 1; 1431 wvalue = 0; 1432 start = 0; 1433 if (wstart < 0) 1434 break; 1435 } 1436 ret = 1; 1437 err: 1438 BN_CTX_end(ctx); 1439 bn_check_top(r); 1440 return ret; 1441 } 1442 1443 /* 1444 * This is a variant of modular exponentiation optimization that does 1445 * parallel 2-primes exponentiation using 256-bit (AVX512VL) AVX512_IFMA ISA 1446 * in 52-bit binary redundant representation. 1447 * If such instructions are not available, or input data size is not supported, 1448 * it falls back to two BN_mod_exp_mont_consttime() calls. 1449 */ 1450 int BN_mod_exp_mont_consttime_x2(BIGNUM *rr1, const BIGNUM *a1, const BIGNUM *p1, 1451 const BIGNUM *m1, BN_MONT_CTX *in_mont1, 1452 BIGNUM *rr2, const BIGNUM *a2, const BIGNUM *p2, 1453 const BIGNUM *m2, BN_MONT_CTX *in_mont2, 1454 BN_CTX *ctx) 1455 { 1456 int ret = 0; 1457 1458 #ifdef RSAZ_ENABLED 1459 BN_MONT_CTX *mont1 = NULL; 1460 BN_MONT_CTX *mont2 = NULL; 1461 1462 if (ossl_rsaz_avx512ifma_eligible() && 1463 ((a1->top == 16) && (p1->top == 16) && (BN_num_bits(m1) == 1024) && 1464 (a2->top == 16) && (p2->top == 16) && (BN_num_bits(m2) == 1024))) { 1465 1466 if (bn_wexpand(rr1, 16) == NULL) 1467 goto err; 1468 if (bn_wexpand(rr2, 16) == NULL) 1469 goto err; 1470 1471 /* Ensure that montgomery contexts are initialized */ 1472 if (in_mont1 != NULL) { 1473 mont1 = in_mont1; 1474 } else { 1475 if ((mont1 = BN_MONT_CTX_new()) == NULL) 1476 goto err; 1477 if (!BN_MONT_CTX_set(mont1, m1, ctx)) 1478 goto err; 1479 } 1480 if (in_mont2 != NULL) { 1481 mont2 = in_mont2; 1482 } else { 1483 if ((mont2 = BN_MONT_CTX_new()) == NULL) 1484 goto err; 1485 if (!BN_MONT_CTX_set(mont2, m2, ctx)) 1486 goto err; 1487 } 1488 1489 ret = ossl_rsaz_mod_exp_avx512_x2(rr1->d, a1->d, p1->d, m1->d, 1490 mont1->RR.d, mont1->n0[0], 1491 rr2->d, a2->d, p2->d, m2->d, 1492 mont2->RR.d, mont2->n0[0], 1493 1024 /* factor bit size */); 1494 1495 rr1->top = 16; 1496 rr1->neg = 0; 1497 bn_correct_top(rr1); 1498 bn_check_top(rr1); 1499 1500 rr2->top = 16; 1501 rr2->neg = 0; 1502 bn_correct_top(rr2); 1503 bn_check_top(rr2); 1504 1505 goto err; 1506 } 1507 #endif 1508 1509 /* rr1 = a1^p1 mod m1 */ 1510 ret = BN_mod_exp_mont_consttime(rr1, a1, p1, m1, ctx, in_mont1); 1511 /* rr2 = a2^p2 mod m2 */ 1512 ret &= BN_mod_exp_mont_consttime(rr2, a2, p2, m2, ctx, in_mont2); 1513 1514 #ifdef RSAZ_ENABLED 1515 err: 1516 if (in_mont2 == NULL) 1517 BN_MONT_CTX_free(mont2); 1518 if (in_mont1 == NULL) 1519 BN_MONT_CTX_free(mont1); 1520 #endif 1521 1522 return ret; 1523 } 1524