1 /*
2 * Copyright 1995-2021 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 /* this one works - simple but works */
BN_exp(BIGNUM * r,const BIGNUM * a,const BIGNUM * p,BN_CTX * ctx)40 int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
41 {
42 int i, bits, ret = 0;
43 BIGNUM *v, *rr;
44
45 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
46 || BN_get_flags(a, BN_FLG_CONSTTIME) != 0) {
47 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
48 ERR_raise(ERR_LIB_BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
49 return 0;
50 }
51
52 BN_CTX_start(ctx);
53 rr = ((r == a) || (r == p)) ? BN_CTX_get(ctx) : r;
54 v = BN_CTX_get(ctx);
55 if (rr == NULL || v == NULL)
56 goto err;
57
58 if (BN_copy(v, a) == NULL)
59 goto err;
60 bits = BN_num_bits(p);
61
62 if (BN_is_odd(p)) {
63 if (BN_copy(rr, a) == NULL)
64 goto err;
65 } else {
66 if (!BN_one(rr))
67 goto err;
68 }
69
70 for (i = 1; i < bits; i++) {
71 if (!BN_sqr(v, v, ctx))
72 goto err;
73 if (BN_is_bit_set(p, i)) {
74 if (!BN_mul(rr, rr, v, ctx))
75 goto err;
76 }
77 }
78 if (r != rr && BN_copy(r, rr) == NULL)
79 goto err;
80
81 ret = 1;
82 err:
83 BN_CTX_end(ctx);
84 bn_check_top(r);
85 return ret;
86 }
87
BN_mod_exp(BIGNUM * r,const BIGNUM * a,const BIGNUM * p,const BIGNUM * m,BN_CTX * ctx)88 int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
89 BN_CTX *ctx)
90 {
91 int ret;
92
93 bn_check_top(a);
94 bn_check_top(p);
95 bn_check_top(m);
96
97 /*-
98 * For even modulus m = 2^k*m_odd, it might make sense to compute
99 * a^p mod m_odd and a^p mod 2^k separately (with Montgomery
100 * exponentiation for the odd part), using appropriate exponent
101 * reductions, and combine the results using the CRT.
102 *
103 * For now, we use Montgomery only if the modulus is odd; otherwise,
104 * exponentiation using the reciprocal-based quick remaindering
105 * algorithm is used.
106 *
107 * (Timing obtained with expspeed.c [computations a^p mod m
108 * where a, p, m are of the same length: 256, 512, 1024, 2048,
109 * 4096, 8192 bits], compared to the running time of the
110 * standard algorithm:
111 *
112 * BN_mod_exp_mont 33 .. 40 % [AMD K6-2, Linux, debug configuration]
113 * 55 .. 77 % [UltraSparc processor, but
114 * debug-solaris-sparcv8-gcc conf.]
115 *
116 * BN_mod_exp_recp 50 .. 70 % [AMD K6-2, Linux, debug configuration]
117 * 62 .. 118 % [UltraSparc, debug-solaris-sparcv8-gcc]
118 *
119 * On the Sparc, BN_mod_exp_recp was faster than BN_mod_exp_mont
120 * at 2048 and more bits, but at 512 and 1024 bits, it was
121 * slower even than the standard algorithm!
122 *
123 * "Real" timings [linux-elf, solaris-sparcv9-gcc configurations]
124 * should be obtained when the new Montgomery reduction code
125 * has been integrated into OpenSSL.)
126 */
127
128 #define MONT_MUL_MOD
129 #define MONT_EXP_WORD
130 #define RECP_MUL_MOD
131
132 #ifdef MONT_MUL_MOD
133 if (BN_is_odd(m)) {
134 # ifdef MONT_EXP_WORD
135 if (a->top == 1 && !a->neg
136 && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0)
137 && (BN_get_flags(a, BN_FLG_CONSTTIME) == 0)
138 && (BN_get_flags(m, BN_FLG_CONSTTIME) == 0)) {
139 BN_ULONG A = a->d[0];
140 ret = BN_mod_exp_mont_word(r, A, p, m, ctx, NULL);
141 } else
142 # endif
143 ret = BN_mod_exp_mont(r, a, p, m, ctx, NULL);
144 } else
145 #endif
146 #ifdef RECP_MUL_MOD
147 {
148 ret = BN_mod_exp_recp(r, a, p, m, ctx);
149 }
150 #else
151 {
152 ret = BN_mod_exp_simple(r, a, p, m, ctx);
153 }
154 #endif
155
156 bn_check_top(r);
157 return ret;
158 }
159
BN_mod_exp_recp(BIGNUM * r,const BIGNUM * a,const BIGNUM * p,const BIGNUM * m,BN_CTX * ctx)160 int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
161 const BIGNUM *m, BN_CTX *ctx)
162 {
163 int i, j, bits, ret = 0, wstart, wend, window, wvalue;
164 int start = 1;
165 BIGNUM *aa;
166 /* Table of variables obtained from 'ctx' */
167 BIGNUM *val[TABLE_SIZE];
168 BN_RECP_CTX recp;
169
170 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
171 || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
172 || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
173 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
174 ERR_raise(ERR_LIB_BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
175 return 0;
176 }
177
178 bits = BN_num_bits(p);
179 if (bits == 0) {
180 /* x**0 mod 1, or x**0 mod -1 is still zero. */
181 if (BN_abs_is_word(m, 1)) {
182 ret = 1;
183 BN_zero(r);
184 } else {
185 ret = BN_one(r);
186 }
187 return ret;
188 }
189
190 BN_CTX_start(ctx);
191 aa = BN_CTX_get(ctx);
192 val[0] = BN_CTX_get(ctx);
193 if (val[0] == NULL)
194 goto err;
195
196 BN_RECP_CTX_init(&recp);
197 if (m->neg) {
198 /* ignore sign of 'm' */
199 if (!BN_copy(aa, m))
200 goto err;
201 aa->neg = 0;
202 if (BN_RECP_CTX_set(&recp, aa, ctx) <= 0)
203 goto err;
204 } else {
205 if (BN_RECP_CTX_set(&recp, m, ctx) <= 0)
206 goto err;
207 }
208
209 if (!BN_nnmod(val[0], a, m, ctx))
210 goto err; /* 1 */
211 if (BN_is_zero(val[0])) {
212 BN_zero(r);
213 ret = 1;
214 goto err;
215 }
216
217 window = BN_window_bits_for_exponent_size(bits);
218 if (window > 1) {
219 if (!BN_mod_mul_reciprocal(aa, val[0], val[0], &recp, ctx))
220 goto err; /* 2 */
221 j = 1 << (window - 1);
222 for (i = 1; i < j; i++) {
223 if (((val[i] = BN_CTX_get(ctx)) == NULL) ||
224 !BN_mod_mul_reciprocal(val[i], val[i - 1], aa, &recp, ctx))
225 goto err;
226 }
227 }
228
229 start = 1; /* This is used to avoid multiplication etc
230 * when there is only the value '1' in the
231 * buffer. */
232 wvalue = 0; /* The 'value' of the window */
233 wstart = bits - 1; /* The top bit of the window */
234 wend = 0; /* The bottom bit of the window */
235
236 if (!BN_one(r))
237 goto err;
238
239 for (;;) {
240 if (BN_is_bit_set(p, wstart) == 0) {
241 if (!start)
242 if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx))
243 goto err;
244 if (wstart == 0)
245 break;
246 wstart--;
247 continue;
248 }
249 /*
250 * We now have wstart on a 'set' bit, we now need to work out how bit
251 * a window to do. To do this we need to scan forward until the last
252 * set bit before the end of the window
253 */
254 wvalue = 1;
255 wend = 0;
256 for (i = 1; i < window; i++) {
257 if (wstart - i < 0)
258 break;
259 if (BN_is_bit_set(p, wstart - i)) {
260 wvalue <<= (i - wend);
261 wvalue |= 1;
262 wend = i;
263 }
264 }
265
266 /* wend is the size of the current window */
267 j = wend + 1;
268 /* add the 'bytes above' */
269 if (!start)
270 for (i = 0; i < j; i++) {
271 if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx))
272 goto err;
273 }
274
275 /* wvalue will be an odd number < 2^window */
276 if (!BN_mod_mul_reciprocal(r, r, val[wvalue >> 1], &recp, ctx))
277 goto err;
278
279 /* move the 'window' down further */
280 wstart -= wend + 1;
281 wvalue = 0;
282 start = 0;
283 if (wstart < 0)
284 break;
285 }
286 ret = 1;
287 err:
288 BN_CTX_end(ctx);
289 BN_RECP_CTX_free(&recp);
290 bn_check_top(r);
291 return ret;
292 }
293
BN_mod_exp_mont(BIGNUM * rr,const BIGNUM * a,const BIGNUM * p,const BIGNUM * m,BN_CTX * ctx,BN_MONT_CTX * in_mont)294 int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
295 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
296 {
297 int i, j, bits, ret = 0, wstart, wend, window, wvalue;
298 int start = 1;
299 BIGNUM *d, *r;
300 const BIGNUM *aa;
301 /* Table of variables obtained from 'ctx' */
302 BIGNUM *val[TABLE_SIZE];
303 BN_MONT_CTX *mont = NULL;
304
305 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
306 || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
307 || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
308 return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont);
309 }
310
311 bn_check_top(a);
312 bn_check_top(p);
313 bn_check_top(m);
314
315 if (!BN_is_odd(m)) {
316 ERR_raise(ERR_LIB_BN, BN_R_CALLED_WITH_EVEN_MODULUS);
317 return 0;
318 }
319 bits = BN_num_bits(p);
320 if (bits == 0) {
321 /* x**0 mod 1, or x**0 mod -1 is still zero. */
322 if (BN_abs_is_word(m, 1)) {
323 ret = 1;
324 BN_zero(rr);
325 } else {
326 ret = BN_one(rr);
327 }
328 return ret;
329 }
330
331 BN_CTX_start(ctx);
332 d = BN_CTX_get(ctx);
333 r = BN_CTX_get(ctx);
334 val[0] = BN_CTX_get(ctx);
335 if (val[0] == NULL)
336 goto err;
337
338 /*
339 * If this is not done, things will break in the montgomery part
340 */
341
342 if (in_mont != NULL)
343 mont = in_mont;
344 else {
345 if ((mont = BN_MONT_CTX_new()) == NULL)
346 goto err;
347 if (!BN_MONT_CTX_set(mont, m, ctx))
348 goto err;
349 }
350
351 if (a->neg || BN_ucmp(a, m) >= 0) {
352 if (!BN_nnmod(val[0], a, m, ctx))
353 goto err;
354 aa = val[0];
355 } else
356 aa = a;
357 if (!bn_to_mont_fixed_top(val[0], aa, mont, ctx))
358 goto err; /* 1 */
359
360 window = BN_window_bits_for_exponent_size(bits);
361 if (window > 1) {
362 if (!bn_mul_mont_fixed_top(d, val[0], val[0], mont, ctx))
363 goto err; /* 2 */
364 j = 1 << (window - 1);
365 for (i = 1; i < j; i++) {
366 if (((val[i] = BN_CTX_get(ctx)) == NULL) ||
367 !bn_mul_mont_fixed_top(val[i], val[i - 1], d, mont, ctx))
368 goto err;
369 }
370 }
371
372 start = 1; /* This is used to avoid multiplication etc
373 * when there is only the value '1' in the
374 * buffer. */
375 wvalue = 0; /* The 'value' of the window */
376 wstart = bits - 1; /* The top bit of the window */
377 wend = 0; /* The bottom bit of the window */
378
379 #if 1 /* by Shay Gueron's suggestion */
380 j = m->top; /* borrow j */
381 if (m->d[j - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) {
382 if (bn_wexpand(r, j) == NULL)
383 goto err;
384 /* 2^(top*BN_BITS2) - m */
385 r->d[0] = (0 - m->d[0]) & BN_MASK2;
386 for (i = 1; i < j; i++)
387 r->d[i] = (~m->d[i]) & BN_MASK2;
388 r->top = j;
389 r->flags |= BN_FLG_FIXED_TOP;
390 } else
391 #endif
392 if (!bn_to_mont_fixed_top(r, BN_value_one(), mont, ctx))
393 goto err;
394 for (;;) {
395 if (BN_is_bit_set(p, wstart) == 0) {
396 if (!start) {
397 if (!bn_mul_mont_fixed_top(r, r, r, mont, ctx))
398 goto err;
399 }
400 if (wstart == 0)
401 break;
402 wstart--;
403 continue;
404 }
405 /*
406 * We now have wstart on a 'set' bit, we now need to work out how bit
407 * a window to do. To do this we need to scan forward until the last
408 * set bit before the end of the window
409 */
410 wvalue = 1;
411 wend = 0;
412 for (i = 1; i < window; i++) {
413 if (wstart - i < 0)
414 break;
415 if (BN_is_bit_set(p, wstart - i)) {
416 wvalue <<= (i - wend);
417 wvalue |= 1;
418 wend = i;
419 }
420 }
421
422 /* wend is the size of the current window */
423 j = wend + 1;
424 /* add the 'bytes above' */
425 if (!start)
426 for (i = 0; i < j; i++) {
427 if (!bn_mul_mont_fixed_top(r, r, r, mont, ctx))
428 goto err;
429 }
430
431 /* wvalue will be an odd number < 2^window */
432 if (!bn_mul_mont_fixed_top(r, r, val[wvalue >> 1], mont, ctx))
433 goto err;
434
435 /* move the 'window' down further */
436 wstart -= wend + 1;
437 wvalue = 0;
438 start = 0;
439 if (wstart < 0)
440 break;
441 }
442 /*
443 * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery
444 * removes padding [if any] and makes return value suitable for public
445 * API consumer.
446 */
447 #if defined(SPARC_T4_MONT)
448 if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) {
449 j = mont->N.top; /* borrow j */
450 val[0]->d[0] = 1; /* borrow val[0] */
451 for (i = 1; i < j; i++)
452 val[0]->d[i] = 0;
453 val[0]->top = j;
454 if (!BN_mod_mul_montgomery(rr, r, val[0], mont, ctx))
455 goto err;
456 } else
457 #endif
458 if (!BN_from_montgomery(rr, r, mont, ctx))
459 goto err;
460 ret = 1;
461 err:
462 if (in_mont == NULL)
463 BN_MONT_CTX_free(mont);
464 BN_CTX_end(ctx);
465 bn_check_top(rr);
466 return ret;
467 }
468
bn_get_bits(const BIGNUM * a,int bitpos)469 static BN_ULONG bn_get_bits(const BIGNUM *a, int bitpos)
470 {
471 BN_ULONG ret = 0;
472 int wordpos;
473
474 wordpos = bitpos / BN_BITS2;
475 bitpos %= BN_BITS2;
476 if (wordpos >= 0 && wordpos < a->top) {
477 ret = a->d[wordpos] & BN_MASK2;
478 if (bitpos) {
479 ret >>= bitpos;
480 if (++wordpos < a->top)
481 ret |= a->d[wordpos] << (BN_BITS2 - bitpos);
482 }
483 }
484
485 return ret & BN_MASK2;
486 }
487
488 /*
489 * BN_mod_exp_mont_consttime() stores the precomputed powers in a specific
490 * layout so that accessing any of these table values shows the same access
491 * pattern as far as cache lines are concerned. The following functions are
492 * used to transfer a BIGNUM from/to that table.
493 */
494
MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM * b,int top,unsigned char * buf,int idx,int window)495 static int MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM *b, int top,
496 unsigned char *buf, int idx,
497 int window)
498 {
499 int i, j;
500 int width = 1 << window;
501 BN_ULONG *table = (BN_ULONG *)buf;
502
503 if (top > b->top)
504 top = b->top; /* this works because 'buf' is explicitly
505 * zeroed */
506 for (i = 0, j = idx; i < top; i++, j += width) {
507 table[j] = b->d[i];
508 }
509
510 return 1;
511 }
512
MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM * b,int top,unsigned char * buf,int idx,int window)513 static int MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int top,
514 unsigned char *buf, int idx,
515 int window)
516 {
517 int i, j;
518 int width = 1 << window;
519 /*
520 * We declare table 'volatile' in order to discourage compiler
521 * from reordering loads from the table. Concern is that if
522 * reordered in specific manner loads might give away the
523 * information we are trying to conceal. Some would argue that
524 * compiler can reorder them anyway, but it can as well be
525 * argued that doing so would be violation of standard...
526 */
527 volatile BN_ULONG *table = (volatile BN_ULONG *)buf;
528
529 if (bn_wexpand(b, top) == NULL)
530 return 0;
531
532 if (window <= 3) {
533 for (i = 0; i < top; i++, table += width) {
534 BN_ULONG acc = 0;
535
536 for (j = 0; j < width; j++) {
537 acc |= table[j] &
538 ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1));
539 }
540
541 b->d[i] = acc;
542 }
543 } else {
544 int xstride = 1 << (window - 2);
545 BN_ULONG y0, y1, y2, y3;
546
547 i = idx >> (window - 2); /* equivalent of idx / xstride */
548 idx &= xstride - 1; /* equivalent of idx % xstride */
549
550 y0 = (BN_ULONG)0 - (constant_time_eq_int(i,0)&1);
551 y1 = (BN_ULONG)0 - (constant_time_eq_int(i,1)&1);
552 y2 = (BN_ULONG)0 - (constant_time_eq_int(i,2)&1);
553 y3 = (BN_ULONG)0 - (constant_time_eq_int(i,3)&1);
554
555 for (i = 0; i < top; i++, table += width) {
556 BN_ULONG acc = 0;
557
558 for (j = 0; j < xstride; j++) {
559 acc |= ( (table[j + 0 * xstride] & y0) |
560 (table[j + 1 * xstride] & y1) |
561 (table[j + 2 * xstride] & y2) |
562 (table[j + 3 * xstride] & y3) )
563 & ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1));
564 }
565
566 b->d[i] = acc;
567 }
568 }
569
570 b->top = top;
571 b->flags |= BN_FLG_FIXED_TOP;
572 return 1;
573 }
574
575 /*
576 * Given a pointer value, compute the next address that is a cache line
577 * multiple.
578 */
579 #define MOD_EXP_CTIME_ALIGN(x_) \
580 ((unsigned char*)(x_) + (MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH - (((size_t)(x_)) & (MOD_EXP_CTIME_MIN_CACHE_LINE_MASK))))
581
582 /*
583 * This variant of BN_mod_exp_mont() uses fixed windows and the special
584 * precomputation memory layout to limit data-dependency to a minimum to
585 * protect secret exponents (cf. the hyper-threading timing attacks pointed
586 * out by Colin Percival,
587 * http://www.daemonology.net/hyperthreading-considered-harmful/)
588 */
BN_mod_exp_mont_consttime(BIGNUM * rr,const BIGNUM * a,const BIGNUM * p,const BIGNUM * m,BN_CTX * ctx,BN_MONT_CTX * in_mont)589 int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
590 const BIGNUM *m, BN_CTX *ctx,
591 BN_MONT_CTX *in_mont)
592 {
593 int i, bits, ret = 0, window, wvalue, wmask, window0;
594 int top;
595 BN_MONT_CTX *mont = NULL;
596
597 int numPowers;
598 unsigned char *powerbufFree = NULL;
599 int powerbufLen = 0;
600 unsigned char *powerbuf = NULL;
601 BIGNUM tmp, am;
602 #if defined(SPARC_T4_MONT)
603 unsigned int t4 = 0;
604 #endif
605
606 bn_check_top(a);
607 bn_check_top(p);
608 bn_check_top(m);
609
610 if (!BN_is_odd(m)) {
611 ERR_raise(ERR_LIB_BN, BN_R_CALLED_WITH_EVEN_MODULUS);
612 return 0;
613 }
614
615 top = m->top;
616
617 /*
618 * Use all bits stored in |p|, rather than |BN_num_bits|, so we do not leak
619 * whether the top bits are zero.
620 */
621 bits = p->top * BN_BITS2;
622 if (bits == 0) {
623 /* x**0 mod 1, or x**0 mod -1 is still zero. */
624 if (BN_abs_is_word(m, 1)) {
625 ret = 1;
626 BN_zero(rr);
627 } else {
628 ret = BN_one(rr);
629 }
630 return ret;
631 }
632
633 BN_CTX_start(ctx);
634
635 /*
636 * Allocate a montgomery context if it was not supplied by the caller. If
637 * this is not done, things will break in the montgomery part.
638 */
639 if (in_mont != NULL)
640 mont = in_mont;
641 else {
642 if ((mont = BN_MONT_CTX_new()) == NULL)
643 goto err;
644 if (!BN_MONT_CTX_set(mont, m, ctx))
645 goto err;
646 }
647
648 if (a->neg || BN_ucmp(a, m) >= 0) {
649 BIGNUM *reduced = BN_CTX_get(ctx);
650 if (reduced == NULL
651 || !BN_nnmod(reduced, a, m, ctx)) {
652 goto err;
653 }
654 a = reduced;
655 }
656
657 #ifdef RSAZ_ENABLED
658 /*
659 * If the size of the operands allow it, perform the optimized
660 * RSAZ exponentiation. For further information see
661 * crypto/bn/rsaz_exp.c and accompanying assembly modules.
662 */
663 if ((16 == a->top) && (16 == p->top) && (BN_num_bits(m) == 1024)
664 && rsaz_avx2_eligible()) {
665 if (NULL == bn_wexpand(rr, 16))
666 goto err;
667 RSAZ_1024_mod_exp_avx2(rr->d, a->d, p->d, m->d, mont->RR.d,
668 mont->n0[0]);
669 rr->top = 16;
670 rr->neg = 0;
671 bn_correct_top(rr);
672 ret = 1;
673 goto err;
674 } else if ((8 == a->top) && (8 == p->top) && (BN_num_bits(m) == 512)) {
675 if (NULL == bn_wexpand(rr, 8))
676 goto err;
677 RSAZ_512_mod_exp(rr->d, a->d, p->d, m->d, mont->n0[0], mont->RR.d);
678 rr->top = 8;
679 rr->neg = 0;
680 bn_correct_top(rr);
681 ret = 1;
682 goto err;
683 }
684 #endif
685
686 /* Get the window size to use with size of p. */
687 window = BN_window_bits_for_ctime_exponent_size(bits);
688 #if defined(SPARC_T4_MONT)
689 if (window >= 5 && (top & 15) == 0 && top <= 64 &&
690 (OPENSSL_sparcv9cap_P[1] & (CFR_MONTMUL | CFR_MONTSQR)) ==
691 (CFR_MONTMUL | CFR_MONTSQR) && (t4 = OPENSSL_sparcv9cap_P[0]))
692 window = 5;
693 else
694 #endif
695 #if defined(OPENSSL_BN_ASM_MONT5)
696 if (window >= 5) {
697 window = 5; /* ~5% improvement for RSA2048 sign, and even
698 * for RSA4096 */
699 /* reserve space for mont->N.d[] copy */
700 powerbufLen += top * sizeof(mont->N.d[0]);
701 }
702 #endif
703 (void)0;
704
705 /*
706 * Allocate a buffer large enough to hold all of the pre-computed powers
707 * of am, am itself and tmp.
708 */
709 numPowers = 1 << window;
710 powerbufLen += sizeof(m->d[0]) * (top * numPowers +
711 ((2 * top) >
712 numPowers ? (2 * top) : numPowers));
713 #ifdef alloca
714 if (powerbufLen < 3072)
715 powerbufFree =
716 alloca(powerbufLen + MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH);
717 else
718 #endif
719 if ((powerbufFree =
720 OPENSSL_malloc(powerbufLen + MOD_EXP_CTIME_MIN_CACHE_LINE_WIDTH))
721 == NULL)
722 goto err;
723
724 powerbuf = MOD_EXP_CTIME_ALIGN(powerbufFree);
725 memset(powerbuf, 0, powerbufLen);
726
727 #ifdef alloca
728 if (powerbufLen < 3072)
729 powerbufFree = NULL;
730 #endif
731
732 /* lay down tmp and am right after powers table */
733 tmp.d = (BN_ULONG *)(powerbuf + sizeof(m->d[0]) * top * numPowers);
734 am.d = tmp.d + top;
735 tmp.top = am.top = 0;
736 tmp.dmax = am.dmax = top;
737 tmp.neg = am.neg = 0;
738 tmp.flags = am.flags = BN_FLG_STATIC_DATA;
739
740 /* prepare a^0 in Montgomery domain */
741 #if 1 /* by Shay Gueron's suggestion */
742 if (m->d[top - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) {
743 /* 2^(top*BN_BITS2) - m */
744 tmp.d[0] = (0 - m->d[0]) & BN_MASK2;
745 for (i = 1; i < top; i++)
746 tmp.d[i] = (~m->d[i]) & BN_MASK2;
747 tmp.top = top;
748 } else
749 #endif
750 if (!bn_to_mont_fixed_top(&tmp, BN_value_one(), mont, ctx))
751 goto err;
752
753 /* prepare a^1 in Montgomery domain */
754 if (!bn_to_mont_fixed_top(&am, a, mont, ctx))
755 goto err;
756
757 #if defined(SPARC_T4_MONT)
758 if (t4) {
759 typedef int (*bn_pwr5_mont_f) (BN_ULONG *tp, const BN_ULONG *np,
760 const BN_ULONG *n0, const void *table,
761 int power, int bits);
762 int bn_pwr5_mont_t4_8(BN_ULONG *tp, const BN_ULONG *np,
763 const BN_ULONG *n0, const void *table,
764 int power, int bits);
765 int bn_pwr5_mont_t4_16(BN_ULONG *tp, const BN_ULONG *np,
766 const BN_ULONG *n0, const void *table,
767 int power, int bits);
768 int bn_pwr5_mont_t4_24(BN_ULONG *tp, const BN_ULONG *np,
769 const BN_ULONG *n0, const void *table,
770 int power, int bits);
771 int bn_pwr5_mont_t4_32(BN_ULONG *tp, const BN_ULONG *np,
772 const BN_ULONG *n0, const void *table,
773 int power, int bits);
774 static const bn_pwr5_mont_f pwr5_funcs[4] = {
775 bn_pwr5_mont_t4_8, bn_pwr5_mont_t4_16,
776 bn_pwr5_mont_t4_24, bn_pwr5_mont_t4_32
777 };
778 bn_pwr5_mont_f pwr5_worker = pwr5_funcs[top / 16 - 1];
779
780 typedef int (*bn_mul_mont_f) (BN_ULONG *rp, const BN_ULONG *ap,
781 const void *bp, const BN_ULONG *np,
782 const BN_ULONG *n0);
783 int bn_mul_mont_t4_8(BN_ULONG *rp, const BN_ULONG *ap, const void *bp,
784 const BN_ULONG *np, const BN_ULONG *n0);
785 int bn_mul_mont_t4_16(BN_ULONG *rp, const BN_ULONG *ap,
786 const void *bp, const BN_ULONG *np,
787 const BN_ULONG *n0);
788 int bn_mul_mont_t4_24(BN_ULONG *rp, const BN_ULONG *ap,
789 const void *bp, const BN_ULONG *np,
790 const BN_ULONG *n0);
791 int bn_mul_mont_t4_32(BN_ULONG *rp, const BN_ULONG *ap,
792 const void *bp, const BN_ULONG *np,
793 const BN_ULONG *n0);
794 static const bn_mul_mont_f mul_funcs[4] = {
795 bn_mul_mont_t4_8, bn_mul_mont_t4_16,
796 bn_mul_mont_t4_24, bn_mul_mont_t4_32
797 };
798 bn_mul_mont_f mul_worker = mul_funcs[top / 16 - 1];
799
800 void bn_mul_mont_vis3(BN_ULONG *rp, const BN_ULONG *ap,
801 const void *bp, const BN_ULONG *np,
802 const BN_ULONG *n0, int num);
803 void bn_mul_mont_t4(BN_ULONG *rp, const BN_ULONG *ap,
804 const void *bp, const BN_ULONG *np,
805 const BN_ULONG *n0, int num);
806 void bn_mul_mont_gather5_t4(BN_ULONG *rp, const BN_ULONG *ap,
807 const void *table, const BN_ULONG *np,
808 const BN_ULONG *n0, int num, int power);
809 void bn_flip_n_scatter5_t4(const BN_ULONG *inp, size_t num,
810 void *table, size_t power);
811 void bn_gather5_t4(BN_ULONG *out, size_t num,
812 void *table, size_t power);
813 void bn_flip_t4(BN_ULONG *dst, BN_ULONG *src, size_t num);
814
815 BN_ULONG *np = mont->N.d, *n0 = mont->n0;
816 int stride = 5 * (6 - (top / 16 - 1)); /* multiple of 5, but less
817 * than 32 */
818
819 /*
820 * BN_to_montgomery can contaminate words above .top [in
821 * BN_DEBUG build...
822 */
823 for (i = am.top; i < top; i++)
824 am.d[i] = 0;
825 for (i = tmp.top; i < top; i++)
826 tmp.d[i] = 0;
827
828 bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 0);
829 bn_flip_n_scatter5_t4(am.d, top, powerbuf, 1);
830 if (!(*mul_worker) (tmp.d, am.d, am.d, np, n0) &&
831 !(*mul_worker) (tmp.d, am.d, am.d, np, n0))
832 bn_mul_mont_vis3(tmp.d, am.d, am.d, np, n0, top);
833 bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, 2);
834
835 for (i = 3; i < 32; i++) {
836 /* Calculate a^i = a^(i-1) * a */
837 if (!(*mul_worker) (tmp.d, tmp.d, am.d, np, n0) &&
838 !(*mul_worker) (tmp.d, tmp.d, am.d, np, n0))
839 bn_mul_mont_vis3(tmp.d, tmp.d, am.d, np, n0, top);
840 bn_flip_n_scatter5_t4(tmp.d, top, powerbuf, i);
841 }
842
843 /* switch to 64-bit domain */
844 np = alloca(top * sizeof(BN_ULONG));
845 top /= 2;
846 bn_flip_t4(np, mont->N.d, top);
847
848 /*
849 * The exponent may not have a whole number of fixed-size windows.
850 * To simplify the main loop, the initial window has between 1 and
851 * full-window-size bits such that what remains is always a whole
852 * number of windows
853 */
854 window0 = (bits - 1) % 5 + 1;
855 wmask = (1 << window0) - 1;
856 bits -= window0;
857 wvalue = bn_get_bits(p, bits) & wmask;
858 bn_gather5_t4(tmp.d, top, powerbuf, wvalue);
859
860 /*
861 * Scan the exponent one window at a time starting from the most
862 * significant bits.
863 */
864 while (bits > 0) {
865 if (bits < stride)
866 stride = bits;
867 bits -= stride;
868 wvalue = bn_get_bits(p, bits);
869
870 if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride))
871 continue;
872 /* retry once and fall back */
873 if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride))
874 continue;
875
876 bits += stride - 5;
877 wvalue >>= stride - 5;
878 wvalue &= 31;
879 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
880 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
881 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
882 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
883 bn_mul_mont_t4(tmp.d, tmp.d, tmp.d, np, n0, top);
884 bn_mul_mont_gather5_t4(tmp.d, tmp.d, powerbuf, np, n0, top,
885 wvalue);
886 }
887
888 bn_flip_t4(tmp.d, tmp.d, top);
889 top *= 2;
890 /* back to 32-bit domain */
891 tmp.top = top;
892 bn_correct_top(&tmp);
893 OPENSSL_cleanse(np, top * sizeof(BN_ULONG));
894 } else
895 #endif
896 #if defined(OPENSSL_BN_ASM_MONT5)
897 if (window == 5 && top > 1) {
898 /*
899 * This optimization uses ideas from http://eprint.iacr.org/2011/239,
900 * specifically optimization of cache-timing attack countermeasures
901 * and pre-computation optimization.
902 */
903
904 /*
905 * Dedicated window==4 case improves 512-bit RSA sign by ~15%, but as
906 * 512-bit RSA is hardly relevant, we omit it to spare size...
907 */
908 void bn_mul_mont_gather5(BN_ULONG *rp, const BN_ULONG *ap,
909 const void *table, const BN_ULONG *np,
910 const BN_ULONG *n0, int num, int power);
911 void bn_scatter5(const BN_ULONG *inp, size_t num,
912 void *table, size_t power);
913 void bn_gather5(BN_ULONG *out, size_t num, void *table, size_t power);
914 void bn_power5(BN_ULONG *rp, const BN_ULONG *ap,
915 const void *table, const BN_ULONG *np,
916 const BN_ULONG *n0, int num, int power);
917 int bn_get_bits5(const BN_ULONG *ap, int off);
918 int bn_from_montgomery(BN_ULONG *rp, const BN_ULONG *ap,
919 const BN_ULONG *not_used, const BN_ULONG *np,
920 const BN_ULONG *n0, int num);
921
922 BN_ULONG *n0 = mont->n0, *np;
923
924 /*
925 * BN_to_montgomery can contaminate words above .top [in
926 * BN_DEBUG build...
927 */
928 for (i = am.top; i < top; i++)
929 am.d[i] = 0;
930 for (i = tmp.top; i < top; i++)
931 tmp.d[i] = 0;
932
933 /*
934 * copy mont->N.d[] to improve cache locality
935 */
936 for (np = am.d + top, i = 0; i < top; i++)
937 np[i] = mont->N.d[i];
938
939 bn_scatter5(tmp.d, top, powerbuf, 0);
940 bn_scatter5(am.d, am.top, powerbuf, 1);
941 bn_mul_mont(tmp.d, am.d, am.d, np, n0, top);
942 bn_scatter5(tmp.d, top, powerbuf, 2);
943
944 # if 0
945 for (i = 3; i < 32; i++) {
946 /* Calculate a^i = a^(i-1) * a */
947 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
948 bn_scatter5(tmp.d, top, powerbuf, i);
949 }
950 # else
951 /* same as above, but uses squaring for 1/2 of operations */
952 for (i = 4; i < 32; i *= 2) {
953 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
954 bn_scatter5(tmp.d, top, powerbuf, i);
955 }
956 for (i = 3; i < 8; i += 2) {
957 int j;
958 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
959 bn_scatter5(tmp.d, top, powerbuf, i);
960 for (j = 2 * i; j < 32; j *= 2) {
961 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
962 bn_scatter5(tmp.d, top, powerbuf, j);
963 }
964 }
965 for (; i < 16; i += 2) {
966 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
967 bn_scatter5(tmp.d, top, powerbuf, i);
968 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
969 bn_scatter5(tmp.d, top, powerbuf, 2 * i);
970 }
971 for (; i < 32; i += 2) {
972 bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
973 bn_scatter5(tmp.d, top, powerbuf, i);
974 }
975 # endif
976 /*
977 * The exponent may not have a whole number of fixed-size windows.
978 * To simplify the main loop, the initial window has between 1 and
979 * full-window-size bits such that what remains is always a whole
980 * number of windows
981 */
982 window0 = (bits - 1) % 5 + 1;
983 wmask = (1 << window0) - 1;
984 bits -= window0;
985 wvalue = bn_get_bits(p, bits) & wmask;
986 bn_gather5(tmp.d, top, powerbuf, wvalue);
987
988 /*
989 * Scan the exponent one window at a time starting from the most
990 * significant bits.
991 */
992 if (top & 7) {
993 while (bits > 0) {
994 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
995 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
996 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
997 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
998 bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
999 bn_mul_mont_gather5(tmp.d, tmp.d, powerbuf, np, n0, top,
1000 bn_get_bits5(p->d, bits -= 5));
1001 }
1002 } else {
1003 while (bits > 0) {
1004 bn_power5(tmp.d, tmp.d, powerbuf, np, n0, top,
1005 bn_get_bits5(p->d, bits -= 5));
1006 }
1007 }
1008
1009 ret = bn_from_montgomery(tmp.d, tmp.d, NULL, np, n0, top);
1010 tmp.top = top;
1011 bn_correct_top(&tmp);
1012 if (ret) {
1013 if (!BN_copy(rr, &tmp))
1014 ret = 0;
1015 goto err; /* non-zero ret means it's not error */
1016 }
1017 } else
1018 #endif
1019 {
1020 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0, window))
1021 goto err;
1022 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&am, top, powerbuf, 1, window))
1023 goto err;
1024
1025 /*
1026 * If the window size is greater than 1, then calculate
1027 * val[i=2..2^winsize-1]. Powers are computed as a*a^(i-1) (even
1028 * powers could instead be computed as (a^(i/2))^2 to use the slight
1029 * performance advantage of sqr over mul).
1030 */
1031 if (window > 1) {
1032 if (!bn_mul_mont_fixed_top(&tmp, &am, &am, mont, ctx))
1033 goto err;
1034 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 2,
1035 window))
1036 goto err;
1037 for (i = 3; i < numPowers; i++) {
1038 /* Calculate a^i = a^(i-1) * a */
1039 if (!bn_mul_mont_fixed_top(&tmp, &am, &tmp, mont, ctx))
1040 goto err;
1041 if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, i,
1042 window))
1043 goto err;
1044 }
1045 }
1046
1047 /*
1048 * The exponent may not have a whole number of fixed-size windows.
1049 * To simplify the main loop, the initial window has between 1 and
1050 * full-window-size bits such that what remains is always a whole
1051 * number of windows
1052 */
1053 window0 = (bits - 1) % window + 1;
1054 wmask = (1 << window0) - 1;
1055 bits -= window0;
1056 wvalue = bn_get_bits(p, bits) & wmask;
1057 if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&tmp, top, powerbuf, wvalue,
1058 window))
1059 goto err;
1060
1061 wmask = (1 << window) - 1;
1062 /*
1063 * Scan the exponent one window at a time starting from the most
1064 * significant bits.
1065 */
1066 while (bits > 0) {
1067
1068 /* Square the result window-size times */
1069 for (i = 0; i < window; i++)
1070 if (!bn_mul_mont_fixed_top(&tmp, &tmp, &tmp, mont, ctx))
1071 goto err;
1072
1073 /*
1074 * Get a window's worth of bits from the exponent
1075 * This avoids calling BN_is_bit_set for each bit, which
1076 * is not only slower but also makes each bit vulnerable to
1077 * EM (and likely other) side-channel attacks like One&Done
1078 * (for details see "One&Done: A Single-Decryption EM-Based
1079 * Attack on OpenSSL's Constant-Time Blinded RSA" by M. Alam,
1080 * H. Khan, M. Dey, N. Sinha, R. Callan, A. Zajic, and
1081 * M. Prvulovic, in USENIX Security'18)
1082 */
1083 bits -= window;
1084 wvalue = bn_get_bits(p, bits) & wmask;
1085 /*
1086 * Fetch the appropriate pre-computed value from the pre-buf
1087 */
1088 if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&am, top, powerbuf, wvalue,
1089 window))
1090 goto err;
1091
1092 /* Multiply the result into the intermediate result */
1093 if (!bn_mul_mont_fixed_top(&tmp, &tmp, &am, mont, ctx))
1094 goto err;
1095 }
1096 }
1097
1098 /*
1099 * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery
1100 * removes padding [if any] and makes return value suitable for public
1101 * API consumer.
1102 */
1103 #if defined(SPARC_T4_MONT)
1104 if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) {
1105 am.d[0] = 1; /* borrow am */
1106 for (i = 1; i < top; i++)
1107 am.d[i] = 0;
1108 if (!BN_mod_mul_montgomery(rr, &tmp, &am, mont, ctx))
1109 goto err;
1110 } else
1111 #endif
1112 if (!BN_from_montgomery(rr, &tmp, mont, ctx))
1113 goto err;
1114 ret = 1;
1115 err:
1116 if (in_mont == NULL)
1117 BN_MONT_CTX_free(mont);
1118 if (powerbuf != NULL) {
1119 OPENSSL_cleanse(powerbuf, powerbufLen);
1120 OPENSSL_free(powerbufFree);
1121 }
1122 BN_CTX_end(ctx);
1123 return ret;
1124 }
1125
BN_mod_exp_mont_word(BIGNUM * rr,BN_ULONG a,const BIGNUM * p,const BIGNUM * m,BN_CTX * ctx,BN_MONT_CTX * in_mont)1126 int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,
1127 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)
1128 {
1129 BN_MONT_CTX *mont = NULL;
1130 int b, bits, ret = 0;
1131 int r_is_one;
1132 BN_ULONG w, next_w;
1133 BIGNUM *r, *t;
1134 BIGNUM *swap_tmp;
1135 #define BN_MOD_MUL_WORD(r, w, m) \
1136 (BN_mul_word(r, (w)) && \
1137 (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \
1138 (BN_mod(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1))))
1139 /*
1140 * BN_MOD_MUL_WORD is only used with 'w' large, so the BN_ucmp test is
1141 * probably more overhead than always using BN_mod (which uses BN_copy if
1142 * a similar test returns true).
1143 */
1144 /*
1145 * We can use BN_mod and do not need BN_nnmod because our accumulator is
1146 * never negative (the result of BN_mod does not depend on the sign of
1147 * the modulus).
1148 */
1149 #define BN_TO_MONTGOMERY_WORD(r, w, mont) \
1150 (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx))
1151
1152 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
1153 || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
1154 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
1155 ERR_raise(ERR_LIB_BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
1156 return 0;
1157 }
1158
1159 bn_check_top(p);
1160 bn_check_top(m);
1161
1162 if (!BN_is_odd(m)) {
1163 ERR_raise(ERR_LIB_BN, BN_R_CALLED_WITH_EVEN_MODULUS);
1164 return 0;
1165 }
1166 if (m->top == 1)
1167 a %= m->d[0]; /* make sure that 'a' is reduced */
1168
1169 bits = BN_num_bits(p);
1170 if (bits == 0) {
1171 /* x**0 mod 1, or x**0 mod -1 is still zero. */
1172 if (BN_abs_is_word(m, 1)) {
1173 ret = 1;
1174 BN_zero(rr);
1175 } else {
1176 ret = BN_one(rr);
1177 }
1178 return ret;
1179 }
1180 if (a == 0) {
1181 BN_zero(rr);
1182 ret = 1;
1183 return ret;
1184 }
1185
1186 BN_CTX_start(ctx);
1187 r = BN_CTX_get(ctx);
1188 t = BN_CTX_get(ctx);
1189 if (t == NULL)
1190 goto err;
1191
1192 if (in_mont != NULL)
1193 mont = in_mont;
1194 else {
1195 if ((mont = BN_MONT_CTX_new()) == NULL)
1196 goto err;
1197 if (!BN_MONT_CTX_set(mont, m, ctx))
1198 goto err;
1199 }
1200
1201 r_is_one = 1; /* except for Montgomery factor */
1202
1203 /* bits-1 >= 0 */
1204
1205 /* The result is accumulated in the product r*w. */
1206 w = a; /* bit 'bits-1' of 'p' is always set */
1207 for (b = bits - 2; b >= 0; b--) {
1208 /* First, square r*w. */
1209 next_w = w * w;
1210 if ((next_w / w) != w) { /* overflow */
1211 if (r_is_one) {
1212 if (!BN_TO_MONTGOMERY_WORD(r, w, mont))
1213 goto err;
1214 r_is_one = 0;
1215 } else {
1216 if (!BN_MOD_MUL_WORD(r, w, m))
1217 goto err;
1218 }
1219 next_w = 1;
1220 }
1221 w = next_w;
1222 if (!r_is_one) {
1223 if (!BN_mod_mul_montgomery(r, r, r, mont, ctx))
1224 goto err;
1225 }
1226
1227 /* Second, multiply r*w by 'a' if exponent bit is set. */
1228 if (BN_is_bit_set(p, b)) {
1229 next_w = w * a;
1230 if ((next_w / a) != w) { /* overflow */
1231 if (r_is_one) {
1232 if (!BN_TO_MONTGOMERY_WORD(r, w, mont))
1233 goto err;
1234 r_is_one = 0;
1235 } else {
1236 if (!BN_MOD_MUL_WORD(r, w, m))
1237 goto err;
1238 }
1239 next_w = a;
1240 }
1241 w = next_w;
1242 }
1243 }
1244
1245 /* Finally, set r:=r*w. */
1246 if (w != 1) {
1247 if (r_is_one) {
1248 if (!BN_TO_MONTGOMERY_WORD(r, w, mont))
1249 goto err;
1250 r_is_one = 0;
1251 } else {
1252 if (!BN_MOD_MUL_WORD(r, w, m))
1253 goto err;
1254 }
1255 }
1256
1257 if (r_is_one) { /* can happen only if a == 1 */
1258 if (!BN_one(rr))
1259 goto err;
1260 } else {
1261 if (!BN_from_montgomery(rr, r, mont, ctx))
1262 goto err;
1263 }
1264 ret = 1;
1265 err:
1266 if (in_mont == NULL)
1267 BN_MONT_CTX_free(mont);
1268 BN_CTX_end(ctx);
1269 bn_check_top(rr);
1270 return ret;
1271 }
1272
1273 /* The old fallback, simple version :-) */
BN_mod_exp_simple(BIGNUM * r,const BIGNUM * a,const BIGNUM * p,const BIGNUM * m,BN_CTX * ctx)1274 int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
1275 const BIGNUM *m, BN_CTX *ctx)
1276 {
1277 int i, j, bits, ret = 0, wstart, wend, window, wvalue;
1278 int start = 1;
1279 BIGNUM *d;
1280 /* Table of variables obtained from 'ctx' */
1281 BIGNUM *val[TABLE_SIZE];
1282
1283 if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
1284 || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
1285 || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
1286 /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
1287 ERR_raise(ERR_LIB_BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
1288 return 0;
1289 }
1290
1291 bits = BN_num_bits(p);
1292 if (bits == 0) {
1293 /* x**0 mod 1, or x**0 mod -1 is still zero. */
1294 if (BN_abs_is_word(m, 1)) {
1295 ret = 1;
1296 BN_zero(r);
1297 } else {
1298 ret = BN_one(r);
1299 }
1300 return ret;
1301 }
1302
1303 BN_CTX_start(ctx);
1304 d = BN_CTX_get(ctx);
1305 val[0] = BN_CTX_get(ctx);
1306 if (val[0] == NULL)
1307 goto err;
1308
1309 if (!BN_nnmod(val[0], a, m, ctx))
1310 goto err; /* 1 */
1311 if (BN_is_zero(val[0])) {
1312 BN_zero(r);
1313 ret = 1;
1314 goto err;
1315 }
1316
1317 window = BN_window_bits_for_exponent_size(bits);
1318 if (window > 1) {
1319 if (!BN_mod_mul(d, val[0], val[0], m, ctx))
1320 goto err; /* 2 */
1321 j = 1 << (window - 1);
1322 for (i = 1; i < j; i++) {
1323 if (((val[i] = BN_CTX_get(ctx)) == NULL) ||
1324 !BN_mod_mul(val[i], val[i - 1], d, m, ctx))
1325 goto err;
1326 }
1327 }
1328
1329 start = 1; /* This is used to avoid multiplication etc
1330 * when there is only the value '1' in the
1331 * buffer. */
1332 wvalue = 0; /* The 'value' of the window */
1333 wstart = bits - 1; /* The top bit of the window */
1334 wend = 0; /* The bottom bit of the window */
1335
1336 if (!BN_one(r))
1337 goto err;
1338
1339 for (;;) {
1340 if (BN_is_bit_set(p, wstart) == 0) {
1341 if (!start)
1342 if (!BN_mod_mul(r, r, r, m, ctx))
1343 goto err;
1344 if (wstart == 0)
1345 break;
1346 wstart--;
1347 continue;
1348 }
1349 /*
1350 * We now have wstart on a 'set' bit, we now need to work out how bit
1351 * a window to do. To do this we need to scan forward until the last
1352 * set bit before the end of the window
1353 */
1354 wvalue = 1;
1355 wend = 0;
1356 for (i = 1; i < window; i++) {
1357 if (wstart - i < 0)
1358 break;
1359 if (BN_is_bit_set(p, wstart - i)) {
1360 wvalue <<= (i - wend);
1361 wvalue |= 1;
1362 wend = i;
1363 }
1364 }
1365
1366 /* wend is the size of the current window */
1367 j = wend + 1;
1368 /* add the 'bytes above' */
1369 if (!start)
1370 for (i = 0; i < j; i++) {
1371 if (!BN_mod_mul(r, r, r, m, ctx))
1372 goto err;
1373 }
1374
1375 /* wvalue will be an odd number < 2^window */
1376 if (!BN_mod_mul(r, r, val[wvalue >> 1], m, ctx))
1377 goto err;
1378
1379 /* move the 'window' down further */
1380 wstart -= wend + 1;
1381 wvalue = 0;
1382 start = 0;
1383 if (wstart < 0)
1384 break;
1385 }
1386 ret = 1;
1387 err:
1388 BN_CTX_end(ctx);
1389 bn_check_top(r);
1390 return ret;
1391 }
1392
1393 /*
1394 * This is a variant of modular exponentiation optimization that does
1395 * parallel 2-primes exponentiation using 256-bit (AVX512VL) AVX512_IFMA ISA
1396 * in 52-bit binary redundant representation.
1397 * If such instructions are not available, or input data size is not supported,
1398 * it falls back to two BN_mod_exp_mont_consttime() calls.
1399 */
BN_mod_exp_mont_consttime_x2(BIGNUM * rr1,const BIGNUM * a1,const BIGNUM * p1,const BIGNUM * m1,BN_MONT_CTX * in_mont1,BIGNUM * rr2,const BIGNUM * a2,const BIGNUM * p2,const BIGNUM * m2,BN_MONT_CTX * in_mont2,BN_CTX * ctx)1400 int BN_mod_exp_mont_consttime_x2(BIGNUM *rr1, const BIGNUM *a1, const BIGNUM *p1,
1401 const BIGNUM *m1, BN_MONT_CTX *in_mont1,
1402 BIGNUM *rr2, const BIGNUM *a2, const BIGNUM *p2,
1403 const BIGNUM *m2, BN_MONT_CTX *in_mont2,
1404 BN_CTX *ctx)
1405 {
1406 int ret = 0;
1407
1408 #ifdef RSAZ_ENABLED
1409 BN_MONT_CTX *mont1 = NULL;
1410 BN_MONT_CTX *mont2 = NULL;
1411
1412 if (ossl_rsaz_avx512ifma_eligible() &&
1413 ((a1->top == 16) && (p1->top == 16) && (BN_num_bits(m1) == 1024) &&
1414 (a2->top == 16) && (p2->top == 16) && (BN_num_bits(m2) == 1024))) {
1415
1416 if (bn_wexpand(rr1, 16) == NULL)
1417 goto err;
1418 if (bn_wexpand(rr2, 16) == NULL)
1419 goto err;
1420
1421 /* Ensure that montgomery contexts are initialized */
1422 if (in_mont1 != NULL) {
1423 mont1 = in_mont1;
1424 } else {
1425 if ((mont1 = BN_MONT_CTX_new()) == NULL)
1426 goto err;
1427 if (!BN_MONT_CTX_set(mont1, m1, ctx))
1428 goto err;
1429 }
1430 if (in_mont2 != NULL) {
1431 mont2 = in_mont2;
1432 } else {
1433 if ((mont2 = BN_MONT_CTX_new()) == NULL)
1434 goto err;
1435 if (!BN_MONT_CTX_set(mont2, m2, ctx))
1436 goto err;
1437 }
1438
1439 ret = ossl_rsaz_mod_exp_avx512_x2(rr1->d, a1->d, p1->d, m1->d,
1440 mont1->RR.d, mont1->n0[0],
1441 rr2->d, a2->d, p2->d, m2->d,
1442 mont2->RR.d, mont2->n0[0],
1443 1024 /* factor bit size */);
1444
1445 rr1->top = 16;
1446 rr1->neg = 0;
1447 bn_correct_top(rr1);
1448 bn_check_top(rr1);
1449
1450 rr2->top = 16;
1451 rr2->neg = 0;
1452 bn_correct_top(rr2);
1453 bn_check_top(rr2);
1454
1455 goto err;
1456 }
1457 #endif
1458
1459 /* rr1 = a1^p1 mod m1 */
1460 ret = BN_mod_exp_mont_consttime(rr1, a1, p1, m1, ctx, in_mont1);
1461 /* rr2 = a2^p2 mod m2 */
1462 ret &= BN_mod_exp_mont_consttime(rr2, a2, p2, m2, ctx, in_mont2);
1463
1464 #ifdef RSAZ_ENABLED
1465 err:
1466 if (in_mont2 == NULL)
1467 BN_MONT_CTX_free(mont2);
1468 if (in_mont1 == NULL)
1469 BN_MONT_CTX_free(mont1);
1470 #endif
1471
1472 return ret;
1473 }
1474