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-rw-r--r--src/lib/libcrypto/ec/ec_mult.c886
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diff --git a/src/lib/libcrypto/ec/ec_mult.c b/src/lib/libcrypto/ec/ec_mult.c
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1/* $OpenBSD: ec_mult.c,v 1.19 2015/09/10 15:56:25 jsing Exp $ */
2/*
3 * Originally written by Bodo Moeller and Nils Larsch for the OpenSSL project.
4 */
5/* ====================================================================
6 * Copyright (c) 1998-2007 The OpenSSL Project. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in
17 * the documentation and/or other materials provided with the
18 * distribution.
19 *
20 * 3. All advertising materials mentioning features or use of this
21 * software must display the following acknowledgment:
22 * "This product includes software developed by the OpenSSL Project
23 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
24 *
25 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
26 * endorse or promote products derived from this software without
27 * prior written permission. For written permission, please contact
28 * openssl-core@openssl.org.
29 *
30 * 5. Products derived from this software may not be called "OpenSSL"
31 * nor may "OpenSSL" appear in their names without prior written
32 * permission of the OpenSSL Project.
33 *
34 * 6. Redistributions of any form whatsoever must retain the following
35 * acknowledgment:
36 * "This product includes software developed by the OpenSSL Project
37 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
38 *
39 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
40 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
41 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
42 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
43 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
45 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
46 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
48 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
49 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
50 * OF THE POSSIBILITY OF SUCH DAMAGE.
51 * ====================================================================
52 *
53 * This product includes cryptographic software written by Eric Young
54 * (eay@cryptsoft.com). This product includes software written by Tim
55 * Hudson (tjh@cryptsoft.com).
56 *
57 */
58/* ====================================================================
59 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
60 * Portions of this software developed by SUN MICROSYSTEMS, INC.,
61 * and contributed to the OpenSSL project.
62 */
63
64#include <string.h>
65
66#include <openssl/err.h>
67
68#include "ec_lcl.h"
69
70
71/*
72 * This file implements the wNAF-based interleaving multi-exponentation method
73 * (<URL:http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller.html#multiexp>);
74 * for multiplication with precomputation, we use wNAF splitting
75 * (<URL:http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller.html#fastexp>).
76 */
77
78
79
80
81/* structure for precomputed multiples of the generator */
82typedef struct ec_pre_comp_st {
83 const EC_GROUP *group; /* parent EC_GROUP object */
84 size_t blocksize; /* block size for wNAF splitting */
85 size_t numblocks; /* max. number of blocks for which we have
86 * precomputation */
87 size_t w; /* window size */
88 EC_POINT **points; /* array with pre-calculated multiples of
89 * generator: 'num' pointers to EC_POINT
90 * objects followed by a NULL */
91 size_t num; /* numblocks * 2^(w-1) */
92 int references;
93} EC_PRE_COMP;
94
95/* functions to manage EC_PRE_COMP within the EC_GROUP extra_data framework */
96static void *ec_pre_comp_dup(void *);
97static void ec_pre_comp_free(void *);
98static void ec_pre_comp_clear_free(void *);
99
100static EC_PRE_COMP *
101ec_pre_comp_new(const EC_GROUP * group)
102{
103 EC_PRE_COMP *ret = NULL;
104
105 if (!group)
106 return NULL;
107
108 ret = malloc(sizeof(EC_PRE_COMP));
109 if (!ret) {
110 ECerr(EC_F_EC_PRE_COMP_NEW, ERR_R_MALLOC_FAILURE);
111 return ret;
112 }
113 ret->group = group;
114 ret->blocksize = 8; /* default */
115 ret->numblocks = 0;
116 ret->w = 4; /* default */
117 ret->points = NULL;
118 ret->num = 0;
119 ret->references = 1;
120 return ret;
121}
122
123static void *
124ec_pre_comp_dup(void *src_)
125{
126 EC_PRE_COMP *src = src_;
127
128 /* no need to actually copy, these objects never change! */
129
130 CRYPTO_add(&src->references, 1, CRYPTO_LOCK_EC_PRE_COMP);
131
132 return src_;
133}
134
135static void
136ec_pre_comp_free(void *pre_)
137{
138 int i;
139 EC_PRE_COMP *pre = pre_;
140
141 if (!pre)
142 return;
143
144 i = CRYPTO_add(&pre->references, -1, CRYPTO_LOCK_EC_PRE_COMP);
145 if (i > 0)
146 return;
147
148 if (pre->points) {
149 EC_POINT **p;
150
151 for (p = pre->points; *p != NULL; p++)
152 EC_POINT_free(*p);
153 free(pre->points);
154 }
155 free(pre);
156}
157
158static void
159ec_pre_comp_clear_free(void *pre_)
160{
161 int i;
162 EC_PRE_COMP *pre = pre_;
163
164 if (!pre)
165 return;
166
167 i = CRYPTO_add(&pre->references, -1, CRYPTO_LOCK_EC_PRE_COMP);
168 if (i > 0)
169 return;
170
171 if (pre->points) {
172 EC_POINT **p;
173
174 for (p = pre->points; *p != NULL; p++) {
175 EC_POINT_clear_free(*p);
176 explicit_bzero(p, sizeof *p);
177 }
178 free(pre->points);
179 }
180 explicit_bzero(pre, sizeof *pre);
181 free(pre);
182}
183
184
185
186
187/* Determine the modified width-(w+1) Non-Adjacent Form (wNAF) of 'scalar'.
188 * This is an array r[] of values that are either zero or odd with an
189 * absolute value less than 2^w satisfying
190 * scalar = \sum_j r[j]*2^j
191 * where at most one of any w+1 consecutive digits is non-zero
192 * with the exception that the most significant digit may be only
193 * w-1 zeros away from that next non-zero digit.
194 */
195static signed char *
196compute_wNAF(const BIGNUM * scalar, int w, size_t * ret_len)
197{
198 int window_val;
199 int ok = 0;
200 signed char *r = NULL;
201 int sign = 1;
202 int bit, next_bit, mask;
203 size_t len = 0, j;
204
205 if (BN_is_zero(scalar)) {
206 r = malloc(1);
207 if (!r) {
208 ECerr(EC_F_COMPUTE_WNAF, ERR_R_MALLOC_FAILURE);
209 goto err;
210 }
211 r[0] = 0;
212 *ret_len = 1;
213 return r;
214 }
215 if (w <= 0 || w > 7) {
216 /* 'signed char' can represent integers with
217 * absolute values less than 2^7 */
218 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR);
219 goto err;
220 }
221 bit = 1 << w; /* at most 128 */
222 next_bit = bit << 1; /* at most 256 */
223 mask = next_bit - 1; /* at most 255 */
224
225 if (BN_is_negative(scalar)) {
226 sign = -1;
227 }
228 if (scalar->d == NULL || scalar->top == 0) {
229 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR);
230 goto err;
231 }
232 len = BN_num_bits(scalar);
233 r = malloc(len + 1); /* modified wNAF may be one digit longer than
234 * binary representation (*ret_len will be
235 * set to the actual length, i.e. at most
236 * BN_num_bits(scalar) + 1) */
237 if (r == NULL) {
238 ECerr(EC_F_COMPUTE_WNAF, ERR_R_MALLOC_FAILURE);
239 goto err;
240 }
241 window_val = scalar->d[0] & mask;
242 j = 0;
243 while ((window_val != 0) || (j + w + 1 < len)) {
244 /* if j+w+1 >= len, window_val will not increase */
245 int digit = 0;
246
247 /* 0 <= window_val <= 2^(w+1) */
248 if (window_val & 1) {
249 /* 0 < window_val < 2^(w+1) */
250 if (window_val & bit) {
251 digit = window_val - next_bit; /* -2^w < digit < 0 */
252
253#if 1 /* modified wNAF */
254 if (j + w + 1 >= len) {
255 /*
256 * special case for generating
257 * modified wNAFs: no new bits will
258 * be added into window_val, so using
259 * a positive digit here will
260 * decrease the total length of the
261 * representation
262 */
263
264 digit = window_val & (mask >> 1); /* 0 < digit < 2^w */
265 }
266#endif
267 } else {
268 digit = window_val; /* 0 < digit < 2^w */
269 }
270
271 if (digit <= -bit || digit >= bit || !(digit & 1)) {
272 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR);
273 goto err;
274 }
275 window_val -= digit;
276
277 /*
278 * now window_val is 0 or 2^(w+1) in standard wNAF
279 * generation; for modified window NAFs, it may also
280 * be 2^w
281 */
282 if (window_val != 0 && window_val != next_bit && window_val != bit) {
283 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR);
284 goto err;
285 }
286 }
287 r[j++] = sign * digit;
288
289 window_val >>= 1;
290 window_val += bit * BN_is_bit_set(scalar, j + w);
291
292 if (window_val > next_bit) {
293 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR);
294 goto err;
295 }
296 }
297
298 if (j > len + 1) {
299 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR);
300 goto err;
301 }
302 len = j;
303 ok = 1;
304
305err:
306 if (!ok) {
307 free(r);
308 r = NULL;
309 }
310 if (ok)
311 *ret_len = len;
312 return r;
313}
314
315
316/* TODO: table should be optimised for the wNAF-based implementation,
317 * sometimes smaller windows will give better performance
318 * (thus the boundaries should be increased)
319 */
320#define EC_window_bits_for_scalar_size(b) \
321 ((size_t) \
322 ((b) >= 2000 ? 6 : \
323 (b) >= 800 ? 5 : \
324 (b) >= 300 ? 4 : \
325 (b) >= 70 ? 3 : \
326 (b) >= 20 ? 2 : \
327 1))
328
329/* Compute
330 * \sum scalars[i]*points[i],
331 * also including
332 * scalar*generator
333 * in the addition if scalar != NULL
334 */
335int
336ec_wNAF_mul(const EC_GROUP * group, EC_POINT * r, const BIGNUM * scalar,
337 size_t num, const EC_POINT * points[], const BIGNUM * scalars[], BN_CTX * ctx)
338{
339 BN_CTX *new_ctx = NULL;
340 const EC_POINT *generator = NULL;
341 EC_POINT *tmp = NULL;
342 size_t totalnum;
343 size_t blocksize = 0, numblocks = 0; /* for wNAF splitting */
344 size_t pre_points_per_block = 0;
345 size_t i, j;
346 int k;
347 int r_is_inverted = 0;
348 int r_is_at_infinity = 1;
349 size_t *wsize = NULL; /* individual window sizes */
350 signed char **wNAF = NULL; /* individual wNAFs */
351 signed char *tmp_wNAF = NULL;
352 size_t *wNAF_len = NULL;
353 size_t max_len = 0;
354 size_t num_val;
355 EC_POINT **val = NULL; /* precomputation */
356 EC_POINT **v;
357 EC_POINT ***val_sub = NULL; /* pointers to sub-arrays of 'val' or
358 * 'pre_comp->points' */
359 const EC_PRE_COMP *pre_comp = NULL;
360 int num_scalar = 0; /* flag: will be set to 1 if 'scalar' must be
361 * treated like other scalars, i.e.
362 * precomputation is not available */
363 int ret = 0;
364
365 if (group->meth != r->meth) {
366 ECerr(EC_F_EC_WNAF_MUL, EC_R_INCOMPATIBLE_OBJECTS);
367 return 0;
368 }
369 if ((scalar == NULL) && (num == 0)) {
370 return EC_POINT_set_to_infinity(group, r);
371 }
372 for (i = 0; i < num; i++) {
373 if (group->meth != points[i]->meth) {
374 ECerr(EC_F_EC_WNAF_MUL, EC_R_INCOMPATIBLE_OBJECTS);
375 return 0;
376 }
377 }
378
379 if (ctx == NULL) {
380 ctx = new_ctx = BN_CTX_new();
381 if (ctx == NULL)
382 goto err;
383 }
384 if (scalar != NULL) {
385 generator = EC_GROUP_get0_generator(group);
386 if (generator == NULL) {
387 ECerr(EC_F_EC_WNAF_MUL, EC_R_UNDEFINED_GENERATOR);
388 goto err;
389 }
390 /* look if we can use precomputed multiples of generator */
391
392 pre_comp = EC_EX_DATA_get_data(group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free);
393
394 if (pre_comp && pre_comp->numblocks &&
395 (EC_POINT_cmp(group, generator, pre_comp->points[0], ctx) == 0)) {
396 blocksize = pre_comp->blocksize;
397
398 /*
399 * determine maximum number of blocks that wNAF
400 * splitting may yield (NB: maximum wNAF length is
401 * bit length plus one)
402 */
403 numblocks = (BN_num_bits(scalar) / blocksize) + 1;
404
405 /*
406 * we cannot use more blocks than we have
407 * precomputation for
408 */
409 if (numblocks > pre_comp->numblocks)
410 numblocks = pre_comp->numblocks;
411
412 pre_points_per_block = (size_t) 1 << (pre_comp->w - 1);
413
414 /* check that pre_comp looks sane */
415 if (pre_comp->num != (pre_comp->numblocks * pre_points_per_block)) {
416 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
417 goto err;
418 }
419 } else {
420 /* can't use precomputation */
421 pre_comp = NULL;
422 numblocks = 1;
423 num_scalar = 1; /* treat 'scalar' like 'num'-th
424 * element of 'scalars' */
425 }
426 }
427 totalnum = num + numblocks;
428
429 /* includes space for pivot */
430 wNAF = reallocarray(NULL, (totalnum + 1), sizeof wNAF[0]);
431 if (wNAF == NULL) {
432 ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
433 goto err;
434 }
435
436 wNAF[0] = NULL; /* preliminary pivot */
437
438 wsize = reallocarray(NULL, totalnum, sizeof wsize[0]);
439 wNAF_len = reallocarray(NULL, totalnum, sizeof wNAF_len[0]);
440 val_sub = reallocarray(NULL, totalnum, sizeof val_sub[0]);
441
442 if (wsize == NULL || wNAF_len == NULL || val_sub == NULL) {
443 ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
444 goto err;
445 }
446
447 /* num_val will be the total number of temporarily precomputed points */
448 num_val = 0;
449
450 for (i = 0; i < num + num_scalar; i++) {
451 size_t bits;
452
453 bits = i < num ? BN_num_bits(scalars[i]) : BN_num_bits(scalar);
454 wsize[i] = EC_window_bits_for_scalar_size(bits);
455 num_val += (size_t) 1 << (wsize[i] - 1);
456 wNAF[i + 1] = NULL; /* make sure we always have a pivot */
457 wNAF[i] = compute_wNAF((i < num ? scalars[i] : scalar), wsize[i], &wNAF_len[i]);
458 if (wNAF[i] == NULL)
459 goto err;
460 if (wNAF_len[i] > max_len)
461 max_len = wNAF_len[i];
462 }
463
464 if (numblocks) {
465 /* we go here iff scalar != NULL */
466
467 if (pre_comp == NULL) {
468 if (num_scalar != 1) {
469 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
470 goto err;
471 }
472 /* we have already generated a wNAF for 'scalar' */
473 } else {
474 size_t tmp_len = 0;
475
476 if (num_scalar != 0) {
477 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
478 goto err;
479 }
480 /*
481 * use the window size for which we have
482 * precomputation
483 */
484 wsize[num] = pre_comp->w;
485 tmp_wNAF = compute_wNAF(scalar, wsize[num], &tmp_len);
486 if (tmp_wNAF == NULL)
487 goto err;
488
489 if (tmp_len <= max_len) {
490 /*
491 * One of the other wNAFs is at least as long
492 * as the wNAF belonging to the generator, so
493 * wNAF splitting will not buy us anything.
494 */
495
496 numblocks = 1;
497 totalnum = num + 1; /* don't use wNAF
498 * splitting */
499 wNAF[num] = tmp_wNAF;
500 tmp_wNAF = NULL;
501 wNAF[num + 1] = NULL;
502 wNAF_len[num] = tmp_len;
503 if (tmp_len > max_len)
504 max_len = tmp_len;
505 /*
506 * pre_comp->points starts with the points
507 * that we need here:
508 */
509 val_sub[num] = pre_comp->points;
510 } else {
511 /*
512 * don't include tmp_wNAF directly into wNAF
513 * array - use wNAF splitting and include the
514 * blocks
515 */
516
517 signed char *pp;
518 EC_POINT **tmp_points;
519
520 if (tmp_len < numblocks * blocksize) {
521 /*
522 * possibly we can do with fewer
523 * blocks than estimated
524 */
525 numblocks = (tmp_len + blocksize - 1) / blocksize;
526 if (numblocks > pre_comp->numblocks) {
527 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
528 goto err;
529 }
530 totalnum = num + numblocks;
531 }
532 /* split wNAF in 'numblocks' parts */
533 pp = tmp_wNAF;
534 tmp_points = pre_comp->points;
535
536 for (i = num; i < totalnum; i++) {
537 if (i < totalnum - 1) {
538 wNAF_len[i] = blocksize;
539 if (tmp_len < blocksize) {
540 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
541 goto err;
542 }
543 tmp_len -= blocksize;
544 } else
545 /*
546 * last block gets whatever
547 * is left (this could be
548 * more or less than
549 * 'blocksize'!)
550 */
551 wNAF_len[i] = tmp_len;
552
553 wNAF[i + 1] = NULL;
554 wNAF[i] = malloc(wNAF_len[i]);
555 if (wNAF[i] == NULL) {
556 ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
557 goto err;
558 }
559 memcpy(wNAF[i], pp, wNAF_len[i]);
560 if (wNAF_len[i] > max_len)
561 max_len = wNAF_len[i];
562
563 if (*tmp_points == NULL) {
564 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
565 goto err;
566 }
567 val_sub[i] = tmp_points;
568 tmp_points += pre_points_per_block;
569 pp += blocksize;
570 }
571 }
572 }
573 }
574 /*
575 * All points we precompute now go into a single array 'val'.
576 * 'val_sub[i]' is a pointer to the subarray for the i-th point, or
577 * to a subarray of 'pre_comp->points' if we already have
578 * precomputation.
579 */
580 val = reallocarray(NULL, (num_val + 1), sizeof val[0]);
581 if (val == NULL) {
582 ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
583 goto err;
584 }
585 val[num_val] = NULL; /* pivot element */
586
587 /* allocate points for precomputation */
588 v = val;
589 for (i = 0; i < num + num_scalar; i++) {
590 val_sub[i] = v;
591 for (j = 0; j < ((size_t) 1 << (wsize[i] - 1)); j++) {
592 *v = EC_POINT_new(group);
593 if (*v == NULL)
594 goto err;
595 v++;
596 }
597 }
598 if (!(v == val + num_val)) {
599 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
600 goto err;
601 }
602 if (!(tmp = EC_POINT_new(group)))
603 goto err;
604
605 /*
606 * prepare precomputed values: val_sub[i][0] := points[i]
607 * val_sub[i][1] := 3 * points[i] val_sub[i][2] := 5 * points[i] ...
608 */
609 for (i = 0; i < num + num_scalar; i++) {
610 if (i < num) {
611 if (!EC_POINT_copy(val_sub[i][0], points[i]))
612 goto err;
613 } else {
614 if (!EC_POINT_copy(val_sub[i][0], generator))
615 goto err;
616 }
617
618 if (wsize[i] > 1) {
619 if (!EC_POINT_dbl(group, tmp, val_sub[i][0], ctx))
620 goto err;
621 for (j = 1; j < ((size_t) 1 << (wsize[i] - 1)); j++) {
622 if (!EC_POINT_add(group, val_sub[i][j], val_sub[i][j - 1], tmp, ctx))
623 goto err;
624 }
625 }
626 }
627
628 if (!EC_POINTs_make_affine(group, num_val, val, ctx))
629 goto err;
630
631 r_is_at_infinity = 1;
632
633 for (k = max_len - 1; k >= 0; k--) {
634 if (!r_is_at_infinity) {
635 if (!EC_POINT_dbl(group, r, r, ctx))
636 goto err;
637 }
638 for (i = 0; i < totalnum; i++) {
639 if (wNAF_len[i] > (size_t) k) {
640 int digit = wNAF[i][k];
641 int is_neg;
642
643 if (digit) {
644 is_neg = digit < 0;
645
646 if (is_neg)
647 digit = -digit;
648
649 if (is_neg != r_is_inverted) {
650 if (!r_is_at_infinity) {
651 if (!EC_POINT_invert(group, r, ctx))
652 goto err;
653 }
654 r_is_inverted = !r_is_inverted;
655 }
656 /* digit > 0 */
657
658 if (r_is_at_infinity) {
659 if (!EC_POINT_copy(r, val_sub[i][digit >> 1]))
660 goto err;
661 r_is_at_infinity = 0;
662 } else {
663 if (!EC_POINT_add(group, r, r, val_sub[i][digit >> 1], ctx))
664 goto err;
665 }
666 }
667 }
668 }
669 }
670
671 if (r_is_at_infinity) {
672 if (!EC_POINT_set_to_infinity(group, r))
673 goto err;
674 } else {
675 if (r_is_inverted)
676 if (!EC_POINT_invert(group, r, ctx))
677 goto err;
678 }
679
680 ret = 1;
681
682err:
683 BN_CTX_free(new_ctx);
684 EC_POINT_free(tmp);
685 free(wsize);
686 free(wNAF_len);
687 free(tmp_wNAF);
688 if (wNAF != NULL) {
689 signed char **w;
690
691 for (w = wNAF; *w != NULL; w++)
692 free(*w);
693
694 free(wNAF);
695 }
696 if (val != NULL) {
697 for (v = val; *v != NULL; v++)
698 EC_POINT_clear_free(*v);
699 free(val);
700 }
701 free(val_sub);
702 return ret;
703}
704
705
706/* ec_wNAF_precompute_mult()
707 * creates an EC_PRE_COMP object with preprecomputed multiples of the generator
708 * for use with wNAF splitting as implemented in ec_wNAF_mul().
709 *
710 * 'pre_comp->points' is an array of multiples of the generator
711 * of the following form:
712 * points[0] = generator;
713 * points[1] = 3 * generator;
714 * ...
715 * points[2^(w-1)-1] = (2^(w-1)-1) * generator;
716 * points[2^(w-1)] = 2^blocksize * generator;
717 * points[2^(w-1)+1] = 3 * 2^blocksize * generator;
718 * ...
719 * points[2^(w-1)*(numblocks-1)-1] = (2^(w-1)) * 2^(blocksize*(numblocks-2)) * generator
720 * points[2^(w-1)*(numblocks-1)] = 2^(blocksize*(numblocks-1)) * generator
721 * ...
722 * points[2^(w-1)*numblocks-1] = (2^(w-1)) * 2^(blocksize*(numblocks-1)) * generator
723 * points[2^(w-1)*numblocks] = NULL
724 */
725int
726ec_wNAF_precompute_mult(EC_GROUP * group, BN_CTX * ctx)
727{
728 const EC_POINT *generator;
729 EC_POINT *tmp_point = NULL, *base = NULL, **var;
730 BN_CTX *new_ctx = NULL;
731 BIGNUM *order;
732 size_t i, bits, w, pre_points_per_block, blocksize, numblocks,
733 num;
734 EC_POINT **points = NULL;
735 EC_PRE_COMP *pre_comp;
736 int ret = 0;
737
738 /* if there is an old EC_PRE_COMP object, throw it away */
739 EC_EX_DATA_free_data(&group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free);
740
741 if ((pre_comp = ec_pre_comp_new(group)) == NULL)
742 return 0;
743
744 generator = EC_GROUP_get0_generator(group);
745 if (generator == NULL) {
746 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNDEFINED_GENERATOR);
747 goto err;
748 }
749 if (ctx == NULL) {
750 ctx = new_ctx = BN_CTX_new();
751 if (ctx == NULL)
752 goto err;
753 }
754 BN_CTX_start(ctx);
755 if ((order = BN_CTX_get(ctx)) == NULL)
756 goto err;
757
758 if (!EC_GROUP_get_order(group, order, ctx))
759 goto err;
760 if (BN_is_zero(order)) {
761 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNKNOWN_ORDER);
762 goto err;
763 }
764 bits = BN_num_bits(order);
765 /*
766 * The following parameters mean we precompute (approximately) one
767 * point per bit.
768 *
769 * TBD: The combination 8, 4 is perfect for 160 bits; for other bit
770 * lengths, other parameter combinations might provide better
771 * efficiency.
772 */
773 blocksize = 8;
774 w = 4;
775 if (EC_window_bits_for_scalar_size(bits) > w) {
776 /* let's not make the window too small ... */
777 w = EC_window_bits_for_scalar_size(bits);
778 }
779 numblocks = (bits + blocksize - 1) / blocksize; /* max. number of blocks
780 * to use for wNAF
781 * splitting */
782
783 pre_points_per_block = (size_t) 1 << (w - 1);
784 num = pre_points_per_block * numblocks; /* number of points to
785 * compute and store */
786
787 points = reallocarray(NULL, (num + 1), sizeof(EC_POINT *));
788 if (!points) {
789 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE);
790 goto err;
791 }
792 var = points;
793 var[num] = NULL; /* pivot */
794 for (i = 0; i < num; i++) {
795 if ((var[i] = EC_POINT_new(group)) == NULL) {
796 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE);
797 goto err;
798 }
799 }
800
801 if (!(tmp_point = EC_POINT_new(group)) || !(base = EC_POINT_new(group))) {
802 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE);
803 goto err;
804 }
805 if (!EC_POINT_copy(base, generator))
806 goto err;
807
808 /* do the precomputation */
809 for (i = 0; i < numblocks; i++) {
810 size_t j;
811
812 if (!EC_POINT_dbl(group, tmp_point, base, ctx))
813 goto err;
814
815 if (!EC_POINT_copy(*var++, base))
816 goto err;
817
818 for (j = 1; j < pre_points_per_block; j++, var++) {
819 /* calculate odd multiples of the current base point */
820 if (!EC_POINT_add(group, *var, tmp_point, *(var - 1), ctx))
821 goto err;
822 }
823
824 if (i < numblocks - 1) {
825 /*
826 * get the next base (multiply current one by
827 * 2^blocksize)
828 */
829 size_t k;
830
831 if (blocksize <= 2) {
832 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_INTERNAL_ERROR);
833 goto err;
834 }
835 if (!EC_POINT_dbl(group, base, tmp_point, ctx))
836 goto err;
837 for (k = 2; k < blocksize; k++) {
838 if (!EC_POINT_dbl(group, base, base, ctx))
839 goto err;
840 }
841 }
842 }
843
844 if (!EC_POINTs_make_affine(group, num, points, ctx))
845 goto err;
846
847 pre_comp->group = group;
848 pre_comp->blocksize = blocksize;
849 pre_comp->numblocks = numblocks;
850 pre_comp->w = w;
851 pre_comp->points = points;
852 points = NULL;
853 pre_comp->num = num;
854
855 if (!EC_EX_DATA_set_data(&group->extra_data, pre_comp,
856 ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free))
857 goto err;
858 pre_comp = NULL;
859
860 ret = 1;
861err:
862 if (ctx != NULL)
863 BN_CTX_end(ctx);
864 BN_CTX_free(new_ctx);
865 ec_pre_comp_free(pre_comp);
866 if (points) {
867 EC_POINT **p;
868
869 for (p = points; *p != NULL; p++)
870 EC_POINT_free(*p);
871 free(points);
872 }
873 EC_POINT_free(tmp_point);
874 EC_POINT_free(base);
875 return ret;
876}
877
878
879int
880ec_wNAF_have_precompute_mult(const EC_GROUP * group)
881{
882 if (EC_EX_DATA_get_data(group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free) != NULL)
883 return 1;
884 else
885 return 0;
886}
generated by cgit v1.2.3-55-g6feb (git 2.39.1) at 2025-12-24 19:07:26 +0000