ec_mult.c@ 94118

Last change on this file since 94118 was 94082, checked in by vboxsync, 3 years ago
libs/openssl-3.0.1: started applying and adjusting our OpenSSL changes to 3.0.1. bugref:10128
File size: 30.8 KB

Line
1	/*
2	* Copyright 2001-2021 The OpenSSL Project Authors. All Rights Reserved.
3	* Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
4	*
5	* Licensed under the Apache License 2.0 (the "License"). You may not use
6	* this file except in compliance with the License. You can obtain a copy
7	* in the file LICENSE in the source distribution or at
8	* https://www.openssl.org/source/license.html
9	*/
10
11	/*
12	* ECDSA low level APIs are deprecated for public use, but still ok for
13	* internal use.
14	*/
15	#include "internal/deprecated.h"
16
17	#include <string.h>
18	#include <openssl/err.h>
19
20	#include "internal/cryptlib.h"
21	#include "crypto/bn.h"
22	#include "ec_local.h"
23	#include "internal/refcount.h"
24
25	/*
26	* This file implements the wNAF-based interleaving multi-exponentiation method
27	* Formerly at:
28	* http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller.html#multiexp
29	* You might now find it here:
30	* http://link.springer.com/chapter/10.1007%2F3-540-45537-X_13
31	* http://www.bmoeller.de/pdf/TI-01-08.multiexp.pdf
32	* For multiplication with precomputation, we use wNAF splitting, formerly at:
33	* http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller.html#fastexp
34	*/
35
36	/* structure for precomputed multiples of the generator */
37	struct ec_pre_comp_st {
38	const EC_GROUP group; / parent EC_GROUP object */
39	size_t blocksize; /* block size for wNAF splitting */
40	size_t numblocks; /* max. number of blocks for which we have
41	* precomputation */
42	size_t w; /* window size */
43	EC_POINT *points; / array with pre-calculated multiples of
44	* generator: 'num' pointers to EC_POINT
45	* objects followed by a NULL */
46	size_t num; /* numblocks * 2^(w-1) */
47	CRYPTO_REF_COUNT references;
48	CRYPTO_RWLOCK *lock;
49	};
50
51	static EC_PRE_COMP ec_pre_comp_new(const EC_GROUP group)
52	{
53	EC_PRE_COMP *ret = NULL;
54
55	if (!group)
56	return NULL;
57
58	ret = OPENSSL_zalloc(sizeof(*ret));
59	if (ret == NULL) {
60	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
61	return ret;
62	}
63
64	ret->group = group;
65	ret->blocksize = 8; /* default */
66	ret->w = 4; /* default */
67	ret->references = 1;
68
69	ret->lock = CRYPTO_THREAD_lock_new();
70	if (ret->lock == NULL) {
71	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
72	OPENSSL_free(ret);
73	return NULL;
74	}
75	return ret;
76	}
77
78	EC_PRE_COMP EC_ec_pre_comp_dup(EC_PRE_COMP pre)
79	{
80	int i;
81	if (pre != NULL)
82	CRYPTO_UP_REF(&pre->references, &i, pre->lock);
83	return pre;
84	}
85
86	void EC_ec_pre_comp_free(EC_PRE_COMP *pre)
87	{
88	int i;
89
90	if (pre == NULL)
91	return;
92
93	CRYPTO_DOWN_REF(&pre->references, &i, pre->lock);
94	REF_PRINT_COUNT("EC_ec", pre);
95	if (i > 0)
96	return;
97	REF_ASSERT_ISNT(i < 0);
98
99	if (pre->points != NULL) {
100	EC_POINT **pts;
101
102	for (pts = pre->points; *pts != NULL; pts++)
103	EC_POINT_free(*pts);
104	OPENSSL_free(pre->points);
105	}
106	CRYPTO_THREAD_lock_free(pre->lock);
107	OPENSSL_free(pre);
108	}
109
110	#define EC_POINT_BN_set_flags(P, flags) do { \
111	BN_set_flags((P)->X, (flags)); \
112	BN_set_flags((P)->Y, (flags)); \
113	BN_set_flags((P)->Z, (flags)); \
114	} while(0)
115
116	/*-
117	* This functions computes a single point multiplication over the EC group,
118	* using, at a high level, a Montgomery ladder with conditional swaps, with
119	* various timing attack defenses.
120	*
121	* It performs either a fixed point multiplication
122	* (scalar * generator)
123	* when point is NULL, or a variable point multiplication
124	* (scalar * point)
125	* when point is not NULL.
126	*
127	* `scalar` cannot be NULL and should be in the range [0,n) otherwise all
128	* constant time bets are off (where n is the cardinality of the EC group).
129	*
130	* This function expects `group->order` and `group->cardinality` to be well
131	* defined and non-zero: it fails with an error code otherwise.
132	*
133	* NB: This says nothing about the constant-timeness of the ladder step
134	* implementation (i.e., the default implementation is based on EC_POINT_add and
135	* EC_POINT_dbl, which of course are not constant time themselves) or the
136	* underlying multiprecision arithmetic.
137	*
138	* The product is stored in `r`.
139	*
140	* This is an internal function: callers are in charge of ensuring that the
141	* input parameters `group`, `r`, `scalar` and `ctx` are not NULL.
142	*
143	* Returns 1 on success, 0 otherwise.
144	*/
145	int ossl_ec_scalar_mul_ladder(const EC_GROUP group, EC_POINT r,
146	const BIGNUM scalar, const EC_POINT point,
147	BN_CTX *ctx)
148	{
149	int i, cardinality_bits, group_top, kbit, pbit, Z_is_one;
150	EC_POINT *p = NULL;
151	EC_POINT *s = NULL;
152	BIGNUM *k = NULL;
153	BIGNUM *lambda = NULL;
154	BIGNUM *cardinality = NULL;
155	int ret = 0;
156
157	/* early exit if the input point is the point at infinity */
158	if (point != NULL && EC_POINT_is_at_infinity(group, point))
159	return EC_POINT_set_to_infinity(group, r);
160
161	if (BN_is_zero(group->order)) {
162	ERR_raise(ERR_LIB_EC, EC_R_UNKNOWN_ORDER);
163	return 0;
164	}
165	if (BN_is_zero(group->cofactor)) {
166	ERR_raise(ERR_LIB_EC, EC_R_UNKNOWN_COFACTOR);
167	return 0;
168	}
169
170	BN_CTX_start(ctx);
171
172	if (((p = EC_POINT_new(group)) == NULL)
173	\|\| ((s = EC_POINT_new(group)) == NULL)) {
174	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
175	goto err;
176	}
177
178	if (point == NULL) {
179	if (!EC_POINT_copy(p, group->generator)) {
180	ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
181	goto err;
182	}
183	} else {
184	if (!EC_POINT_copy(p, point)) {
185	ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
186	goto err;
187	}
188	}
189
190	EC_POINT_BN_set_flags(p, BN_FLG_CONSTTIME);
191	EC_POINT_BN_set_flags(r, BN_FLG_CONSTTIME);
192	EC_POINT_BN_set_flags(s, BN_FLG_CONSTTIME);
193
194	cardinality = BN_CTX_get(ctx);
195	lambda = BN_CTX_get(ctx);
196	k = BN_CTX_get(ctx);
197	if (k == NULL) {
198	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
199	goto err;
200	}
201
202	if (!BN_mul(cardinality, group->order, group->cofactor, ctx)) {
203	ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
204	goto err;
205	}
206
207	/*
208	* Group cardinalities are often on a word boundary.
209	* So when we pad the scalar, some timing diff might
210	* pop if it needs to be expanded due to carries.
211	* So expand ahead of time.
212	*/
213	cardinality_bits = BN_num_bits(cardinality);
214	group_top = bn_get_top(cardinality);
215	if ((bn_wexpand(k, group_top + 2) == NULL)
216	\|\| (bn_wexpand(lambda, group_top + 2) == NULL)) {
217	ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
218	goto err;
219	}
220
221	if (!BN_copy(k, scalar)) {
222	ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
223	goto err;
224	}
225
226	BN_set_flags(k, BN_FLG_CONSTTIME);
227
228	if ((BN_num_bits(k) > cardinality_bits) \|\| (BN_is_negative(k))) {
229	/*-
230	* this is an unusual input, and we don't guarantee
231	* constant-timeness
232	*/
233	if (!BN_nnmod(k, k, cardinality, ctx)) {
234	ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
235	goto err;
236	}
237	}
238
239	if (!BN_add(lambda, k, cardinality)) {
240	ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
241	goto err;
242	}
243	BN_set_flags(lambda, BN_FLG_CONSTTIME);
244	if (!BN_add(k, lambda, cardinality)) {
245	ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
246	goto err;
247	}
248	/*
249	* lambda := scalar + cardinality
250	* k := scalar + 2*cardinality
251	*/
252	kbit = BN_is_bit_set(lambda, cardinality_bits);
253	BN_consttime_swap(kbit, k, lambda, group_top + 2);
254
255	group_top = bn_get_top(group->field);
256	if ((bn_wexpand(s->X, group_top) == NULL)
257	\|\| (bn_wexpand(s->Y, group_top) == NULL)
258	\|\| (bn_wexpand(s->Z, group_top) == NULL)
259	\|\| (bn_wexpand(r->X, group_top) == NULL)
260	\|\| (bn_wexpand(r->Y, group_top) == NULL)
261	\|\| (bn_wexpand(r->Z, group_top) == NULL)
262	\|\| (bn_wexpand(p->X, group_top) == NULL)
263	\|\| (bn_wexpand(p->Y, group_top) == NULL)
264	\|\| (bn_wexpand(p->Z, group_top) == NULL)) {
265	ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
266	goto err;
267	}
268
269	/* ensure input point is in affine coords for ladder step efficiency */
270	if (!p->Z_is_one && (group->meth->make_affine == NULL
271	\|\| !group->meth->make_affine(group, p, ctx))) {
272	ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
273	goto err;
274	}
275
276	/* Initialize the Montgomery ladder */
277	if (!ec_point_ladder_pre(group, r, s, p, ctx)) {
278	ERR_raise(ERR_LIB_EC, EC_R_LADDER_PRE_FAILURE);
279	goto err;
280	}
281
282	/* top bit is a 1, in a fixed pos */
283	pbit = 1;
284
285	#define EC_POINT_CSWAP(c, a, b, w, t) do { \
286	BN_consttime_swap(c, (a)->X, (b)->X, w); \
287	BN_consttime_swap(c, (a)->Y, (b)->Y, w); \
288	BN_consttime_swap(c, (a)->Z, (b)->Z, w); \
289	t = ((a)->Z_is_one ^ (b)->Z_is_one) & (c); \
290	(a)->Z_is_one ^= (t); \
291	(b)->Z_is_one ^= (t); \
292	} while(0)
293
294	/*-
295	* The ladder step, with branches, is
296	*
297	* k[i] == 0: S = add(R, S), R = dbl(R)
298	* k[i] == 1: R = add(S, R), S = dbl(S)
299	*
300	* Swapping R, S conditionally on k[i] leaves you with state
301	*
302	* k[i] == 0: T, U = R, S
303	* k[i] == 1: T, U = S, R
304	*
305	* Then perform the ECC ops.
306	*
307	* U = add(T, U)
308	* T = dbl(T)
309	*
310	* Which leaves you with state
311	*
312	* k[i] == 0: U = add(R, S), T = dbl(R)
313	* k[i] == 1: U = add(S, R), T = dbl(S)
314	*
315	* Swapping T, U conditionally on k[i] leaves you with state
316	*
317	* k[i] == 0: R, S = T, U
318	* k[i] == 1: R, S = U, T
319	*
320	* Which leaves you with state
321	*
322	* k[i] == 0: S = add(R, S), R = dbl(R)
323	* k[i] == 1: R = add(S, R), S = dbl(S)
324	*
325	* So we get the same logic, but instead of a branch it's a
326	* conditional swap, followed by ECC ops, then another conditional swap.
327	*
328	* Optimization: The end of iteration i and start of i-1 looks like
329	*
330	* ...
331	* CSWAP(k[i], R, S)
332	* ECC
333	* CSWAP(k[i], R, S)
334	* (next iteration)
335	* CSWAP(k[i-1], R, S)
336	* ECC
337	* CSWAP(k[i-1], R, S)
338	* ...
339	*
340	* So instead of two contiguous swaps, you can merge the condition
341	* bits and do a single swap.
342	*
343	* k[i] k[i-1] Outcome
344	* 0 0 No Swap
345	* 0 1 Swap
346	* 1 0 Swap
347	* 1 1 No Swap
348	*
349	* This is XOR. pbit tracks the previous bit of k.
350	*/
351
352	for (i = cardinality_bits - 1; i >= 0; i--) {
353	kbit = BN_is_bit_set(k, i) ^ pbit;
354	EC_POINT_CSWAP(kbit, r, s, group_top, Z_is_one);
355
356	/* Perform a single step of the Montgomery ladder */
357	if (!ec_point_ladder_step(group, r, s, p, ctx)) {
358	ERR_raise(ERR_LIB_EC, EC_R_LADDER_STEP_FAILURE);
359	goto err;
360	}
361	/*
362	* pbit logic merges this cswap with that of the
363	* next iteration
364	*/
365	pbit ^= kbit;
366	}
367	/* one final cswap to move the right value into r */
368	EC_POINT_CSWAP(pbit, r, s, group_top, Z_is_one);
369	#undef EC_POINT_CSWAP
370
371	/* Finalize ladder (and recover full point coordinates) */
372	if (!ec_point_ladder_post(group, r, s, p, ctx)) {
373	ERR_raise(ERR_LIB_EC, EC_R_LADDER_POST_FAILURE);
374	goto err;
375	}
376
377	ret = 1;
378
379	err:
380	EC_POINT_free(p);
381	EC_POINT_clear_free(s);
382	BN_CTX_end(ctx);
383
384	return ret;
385	}
386
387	#undef EC_POINT_BN_set_flags
388
389	/*
390	* Table could be optimised for the wNAF-based implementation,
391	* sometimes smaller windows will give better performance (thus the
392	* boundaries should be increased)
393	*/
394	#define EC_window_bits_for_scalar_size(b) \
395	((size_t) \
396	((b) >= 2000 ? 6 : \
397	(b) >= 800 ? 5 : \
398	(b) >= 300 ? 4 : \
399	(b) >= 70 ? 3 : \
400	(b) >= 20 ? 2 : \
401	1))
402
403	/*-
404	* Compute
405	* \sum scalars[i]*points[i],
406	* also including
407	* scalar*generator
408	* in the addition if scalar != NULL
409	*/
410	int ossl_ec_wNAF_mul(const EC_GROUP group, EC_POINT r, const BIGNUM *scalar,
411	size_t num, const EC_POINT *points[],
412	const BIGNUM scalars[], BN_CTX ctx)
413	{
414	const EC_POINT *generator = NULL;
415	EC_POINT *tmp = NULL;
416	size_t totalnum;
417	size_t blocksize = 0, numblocks = 0; /* for wNAF splitting */
418	size_t pre_points_per_block = 0;
419	size_t i, j;
420	int k;
421	int r_is_inverted = 0;
422	int r_is_at_infinity = 1;
423	size_t wsize = NULL; / individual window sizes */
424	signed char *wNAF = NULL; / individual wNAFs */
425	size_t *wNAF_len = NULL;
426	size_t max_len = 0;
427	size_t num_val;
428	EC_POINT *val = NULL; / precomputation */
429	EC_POINT **v;
430	EC_POINT **val_sub = NULL; / pointers to sub-arrays of 'val' or
431	* 'pre_comp->points' */
432	const EC_PRE_COMP *pre_comp = NULL;
433	int num_scalar = 0; /* flag: will be set to 1 if 'scalar' must be
434	* treated like other scalars, i.e.
435	* precomputation is not available */
436	int ret = 0;
437
438	if (!BN_is_zero(group->order) && !BN_is_zero(group->cofactor)) {
439	/*-
440	* Handle the common cases where the scalar is secret, enforcing a
441	* scalar multiplication implementation based on a Montgomery ladder,
442	* with various timing attack defenses.
443	*/
444	if ((scalar != group->order) && (scalar != NULL) && (num == 0)) {
445	/*-
446	* In this case we want to compute scalar * GeneratorPoint: this
447	* codepath is reached most prominently by (ephemeral) key
448	* generation of EC cryptosystems (i.e. ECDSA keygen and sign setup,
449	* ECDH keygen/first half), where the scalar is always secret. This
450	* is why we ignore if BN_FLG_CONSTTIME is actually set and we
451	* always call the ladder version.
452	*/
453	return ossl_ec_scalar_mul_ladder(group, r, scalar, NULL, ctx);
454	}
455	if ((scalar == NULL) && (num == 1) && (scalars[0] != group->order)) {
456	/*-
457	* In this case we want to compute scalar * VariablePoint: this
458	* codepath is reached most prominently by the second half of ECDH,
459	* where the secret scalar is multiplied by the peer's public point.
460	* To protect the secret scalar, we ignore if BN_FLG_CONSTTIME is
461	* actually set and we always call the ladder version.
462	*/
463	return ossl_ec_scalar_mul_ladder(group, r, scalars[0], points[0],
464	ctx);
465	}
466	}
467
468	if (scalar != NULL) {
469	generator = EC_GROUP_get0_generator(group);
470	if (generator == NULL) {
471	ERR_raise(ERR_LIB_EC, EC_R_UNDEFINED_GENERATOR);
472	goto err;
473	}
474
475	/* look if we can use precomputed multiples of generator */
476
477	pre_comp = group->pre_comp.ec;
478	if (pre_comp && pre_comp->numblocks
479	&& (EC_POINT_cmp(group, generator, pre_comp->points[0], ctx) ==
480	0)) {
481	blocksize = pre_comp->blocksize;
482
483	/*
484	* determine maximum number of blocks that wNAF splitting may
485	* yield (NB: maximum wNAF length is bit length plus one)
486	*/
487	numblocks = (BN_num_bits(scalar) / blocksize) + 1;
488
489	/*
490	* we cannot use more blocks than we have precomputation for
491	*/
492	if (numblocks > pre_comp->numblocks)
493	numblocks = pre_comp->numblocks;
494
495	pre_points_per_block = (size_t)1 << (pre_comp->w - 1);
496
497	/* check that pre_comp looks sane */
498	if (pre_comp->num != (pre_comp->numblocks * pre_points_per_block)) {
499	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
500	goto err;
501	}
502	} else {
503	/* can't use precomputation */
504	pre_comp = NULL;
505	numblocks = 1;
506	num_scalar = 1; /* treat 'scalar' like 'num'-th element of
507	* 'scalars' */
508	}
509	}
510
511	totalnum = num + numblocks;
512
513	wsize = OPENSSL_malloc(totalnum * sizeof(wsize[0]));
514	wNAF_len = OPENSSL_malloc(totalnum * sizeof(wNAF_len[0]));
515	/* include space for pivot */
516	wNAF = OPENSSL_malloc((totalnum + 1) * sizeof(wNAF[0]));
517	val_sub = OPENSSL_malloc(totalnum * sizeof(val_sub[0]));
518
519	/* Ensure wNAF is initialised in case we end up going to err */
520	if (wNAF != NULL)
521	wNAF[0] = NULL; /* preliminary pivot */
522
523	if (wsize == NULL \|\| wNAF_len == NULL \|\| wNAF == NULL \|\| val_sub == NULL) {
524	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
525	goto err;
526	}
527
528	/*
529	* num_val will be the total number of temporarily precomputed points
530	*/
531	num_val = 0;
532
533	for (i = 0; i < num + num_scalar; i++) {
534	size_t bits;
535
536	bits = i < num ? BN_num_bits(scalars[i]) : BN_num_bits(scalar);
537	wsize[i] = EC_window_bits_for_scalar_size(bits);
538	num_val += (size_t)1 << (wsize[i] - 1);
539	wNAF[i + 1] = NULL; /* make sure we always have a pivot */
540	wNAF[i] =
541	bn_compute_wNAF((i < num ? scalars[i] : scalar), wsize[i],
542	&wNAF_len[i]);
543	if (wNAF[i] == NULL)
544	goto err;
545	if (wNAF_len[i] > max_len)
546	max_len = wNAF_len[i];
547	}
548
549	if (numblocks) {
550	/* we go here iff scalar != NULL */
551
552	if (pre_comp == NULL) {
553	if (num_scalar != 1) {
554	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
555	goto err;
556	}
557	/* we have already generated a wNAF for 'scalar' */
558	} else {
559	signed char *tmp_wNAF = NULL;
560	size_t tmp_len = 0;
561
562	if (num_scalar != 0) {
563	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
564	goto err;
565	}
566
567	/*
568	* use the window size for which we have precomputation
569	*/
570	wsize[num] = pre_comp->w;
571	tmp_wNAF = bn_compute_wNAF(scalar, wsize[num], &tmp_len);
572	if (!tmp_wNAF)
573	goto err;
574
575	if (tmp_len <= max_len) {
576	/*
577	* One of the other wNAFs is at least as long as the wNAF
578	* belonging to the generator, so wNAF splitting will not buy
579	* us anything.
580	*/
581
582	numblocks = 1;
583	totalnum = num + 1; /* don't use wNAF splitting */
584	wNAF[num] = tmp_wNAF;
585	wNAF[num + 1] = NULL;
586	wNAF_len[num] = tmp_len;
587	/*
588	* pre_comp->points starts with the points that we need here:
589	*/
590	val_sub[num] = pre_comp->points;
591	} else {
592	/*
593	* don't include tmp_wNAF directly into wNAF array - use wNAF
594	* splitting and include the blocks
595	*/
596
597	signed char *pp;
598	EC_POINT **tmp_points;
599
600	if (tmp_len < numblocks * blocksize) {
601	/*
602	* possibly we can do with fewer blocks than estimated
603	*/
604	numblocks = (tmp_len + blocksize - 1) / blocksize;
605	if (numblocks > pre_comp->numblocks) {
606	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
607	OPENSSL_free(tmp_wNAF);
608	goto err;
609	}
610	totalnum = num + numblocks;
611	}
612
613	/* split wNAF in 'numblocks' parts */
614	pp = tmp_wNAF;
615	tmp_points = pre_comp->points;
616
617	for (i = num; i < totalnum; i++) {
618	if (i < totalnum - 1) {
619	wNAF_len[i] = blocksize;
620	if (tmp_len < blocksize) {
621	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
622	OPENSSL_free(tmp_wNAF);
623	goto err;
624	}
625	tmp_len -= blocksize;
626	} else
627	/*
628	* last block gets whatever is left (this could be
629	* more or less than 'blocksize'!)
630	*/
631	wNAF_len[i] = tmp_len;
632
633	wNAF[i + 1] = NULL;
634	wNAF[i] = OPENSSL_malloc(wNAF_len[i]);
635	if (wNAF[i] == NULL) {
636	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
637	OPENSSL_free(tmp_wNAF);
638	goto err;
639	}
640	memcpy(wNAF[i], pp, wNAF_len[i]);
641	if (wNAF_len[i] > max_len)
642	max_len = wNAF_len[i];
643
644	if (*tmp_points == NULL) {
645	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
646	OPENSSL_free(tmp_wNAF);
647	goto err;
648	}
649	val_sub[i] = tmp_points;
650	tmp_points += pre_points_per_block;
651	pp += blocksize;
652	}
653	OPENSSL_free(tmp_wNAF);
654	}
655	}
656	}
657
658	/*
659	* All points we precompute now go into a single array 'val'.
660	* 'val_sub[i]' is a pointer to the subarray for the i-th point, or to a
661	* subarray of 'pre_comp->points' if we already have precomputation.
662	*/
663	val = OPENSSL_malloc((num_val + 1) * sizeof(val[0]));
664	if (val == NULL) {
665	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
666	goto err;
667	}
668	val[num_val] = NULL; /* pivot element */
669
670	/* allocate points for precomputation */
671	v = val;
672	for (i = 0; i < num + num_scalar; i++) {
673	val_sub[i] = v;
674	for (j = 0; j < ((size_t)1 << (wsize[i] - 1)); j++) {
675	*v = EC_POINT_new(group);
676	if (*v == NULL)
677	goto err;
678	v++;
679	}
680	}
681	if (!(v == val + num_val)) {
682	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
683	goto err;
684	}
685
686	if ((tmp = EC_POINT_new(group)) == NULL)
687	goto err;
688
689	/*-
690	* prepare precomputed values:
691	* val_sub[i][0] := points[i]
692	* val_sub[i][1] := 3 * points[i]
693	* val_sub[i][2] := 5 * points[i]
694	* ...
695	*/
696	for (i = 0; i < num + num_scalar; i++) {
697	if (i < num) {
698	if (!EC_POINT_copy(val_sub[i][0], points[i]))
699	goto err;
700	} else {
701	if (!EC_POINT_copy(val_sub[i][0], generator))
702	goto err;
703	}
704
705	if (wsize[i] > 1) {
706	if (!EC_POINT_dbl(group, tmp, val_sub[i][0], ctx))
707	goto err;
708	for (j = 1; j < ((size_t)1 << (wsize[i] - 1)); j++) {
709	if (!EC_POINT_add
710	(group, val_sub[i][j], val_sub[i][j - 1], tmp, ctx))
711	goto err;
712	}
713	}
714	}
715
716	if (group->meth->points_make_affine == NULL
717	\|\| !group->meth->points_make_affine(group, num_val, val, ctx))
718	goto err;
719
720	r_is_at_infinity = 1;
721
722	for (k = max_len - 1; k >= 0; k--) {
723	if (!r_is_at_infinity) {
724	if (!EC_POINT_dbl(group, r, r, ctx))
725	goto err;
726	}
727
728	for (i = 0; i < totalnum; i++) {
729	if (wNAF_len[i] > (size_t)k) {
730	int digit = wNAF[i][k];
731	int is_neg;
732
733	if (digit) {
734	is_neg = digit < 0;
735
736	if (is_neg)
737	digit = -digit;
738
739	if (is_neg != r_is_inverted) {
740	if (!r_is_at_infinity) {
741	if (!EC_POINT_invert(group, r, ctx))
742	goto err;
743	}
744	r_is_inverted = !r_is_inverted;
745	}
746
747	/* digit > 0 */
748
749	if (r_is_at_infinity) {
750	if (!EC_POINT_copy(r, val_sub[i][digit >> 1]))
751	goto err;
752
753	/*-
754	* Apply coordinate blinding for EC_POINT.
755	*
756	* The underlying EC_METHOD can optionally implement this function:
757	* ossl_ec_point_blind_coordinates() returns 0 in case of errors or 1 on
758	* success or if coordinate blinding is not implemented for this
759	* group.
760	*/
761	if (!ossl_ec_point_blind_coordinates(group, r, ctx)) {
762	ERR_raise(ERR_LIB_EC, EC_R_POINT_COORDINATES_BLIND_FAILURE);
763	goto err;
764	}
765
766	r_is_at_infinity = 0;
767	} else {
768	if (!EC_POINT_add
769	(group, r, r, val_sub[i][digit >> 1], ctx))
770	goto err;
771	}
772	}
773	}
774	}
775	}
776
777	if (r_is_at_infinity) {
778	if (!EC_POINT_set_to_infinity(group, r))
779	goto err;
780	} else {
781	if (r_is_inverted)
782	if (!EC_POINT_invert(group, r, ctx))
783	goto err;
784	}
785
786	ret = 1;
787
788	err:
789	EC_POINT_free(tmp);
790	OPENSSL_free(wsize);
791	OPENSSL_free(wNAF_len);
792	if (wNAF != NULL) {
793	signed char **w;
794
795	for (w = wNAF; *w != NULL; w++)
796	OPENSSL_free(*w);
797
798	OPENSSL_free(wNAF);
799	}
800	if (val != NULL) {
801	for (v = val; *v != NULL; v++)
802	EC_POINT_clear_free(*v);
803
804	OPENSSL_free(val);
805	}
806	OPENSSL_free(val_sub);
807	return ret;
808	}
809
810	/*-
811	* ossl_ec_wNAF_precompute_mult()
812	* creates an EC_PRE_COMP object with preprecomputed multiples of the generator
813	* for use with wNAF splitting as implemented in ossl_ec_wNAF_mul().
814	*
815	* 'pre_comp->points' is an array of multiples of the generator
816	* of the following form:
817	* points[0] = generator;
818	* points[1] = 3 * generator;
819	* ...
820	* points[2^(w-1)-1] = (2^(w-1)-1) * generator;
821	* points[2^(w-1)] = 2^blocksize * generator;
822	* points[2^(w-1)+1] = 3 * 2^blocksize * generator;
823	* ...
824	* points[2^(w-1)(numblocks-1)-1] = (2^(w-1)) 2^(blocksize(numblocks-2)) generator
825	* points[2^(w-1)(numblocks-1)] = 2^(blocksize(numblocks-1)) * generator
826	* ...
827	* points[2^(w-1)numblocks-1] = (2^(w-1)) 2^(blocksize(numblocks-1)) generator
828	* points[2^(w-1)*numblocks] = NULL
829	*/
830	int ossl_ec_wNAF_precompute_mult(EC_GROUP group, BN_CTX ctx)
831	{
832	const EC_POINT *generator;
833	EC_POINT tmp_point = NULL, base = NULL, **var;
834	const BIGNUM *order;
835	size_t i, bits, w, pre_points_per_block, blocksize, numblocks, num;
836	EC_POINT **points = NULL;
837	EC_PRE_COMP *pre_comp;
838	int ret = 0;
839	int used_ctx = 0;
840	#ifndef FIPS_MODULE
841	BN_CTX *new_ctx = NULL;
842	#endif
843
844	/* if there is an old EC_PRE_COMP object, throw it away */
845	EC_pre_comp_free(group);
846	if ((pre_comp = ec_pre_comp_new(group)) == NULL)
847	return 0;
848
849	generator = EC_GROUP_get0_generator(group);
850	if (generator == NULL) {
851	ERR_raise(ERR_LIB_EC, EC_R_UNDEFINED_GENERATOR);
852	goto err;
853	}
854
855	#ifndef FIPS_MODULE
856	if (ctx == NULL)
857	ctx = new_ctx = BN_CTX_new();
858	#endif
859	if (ctx == NULL)
860	goto err;
861
862	BN_CTX_start(ctx);
863	used_ctx = 1;
864
865	order = EC_GROUP_get0_order(group);
866	if (order == NULL)
867	goto err;
868	if (BN_is_zero(order)) {
869	ERR_raise(ERR_LIB_EC, EC_R_UNKNOWN_ORDER);
870	goto err;
871	}
872
873	bits = BN_num_bits(order);
874	/*
875	* The following parameters mean we precompute (approximately) one point
876	* per bit. TBD: The combination 8, 4 is perfect for 160 bits; for other
877	* bit lengths, other parameter combinations might provide better
878	* efficiency.
879	*/
880	blocksize = 8;
881	w = 4;
882	if (EC_window_bits_for_scalar_size(bits) > w) {
883	/* let's not make the window too small ... */
884	w = EC_window_bits_for_scalar_size(bits);
885	}
886
887	numblocks = (bits + blocksize - 1) / blocksize; /* max. number of blocks
888	* to use for wNAF
889	* splitting */
890
891	pre_points_per_block = (size_t)1 << (w - 1);
892	num = pre_points_per_block * numblocks; /* number of points to compute
893	* and store */
894
895	points = OPENSSL_malloc(sizeof(points) (num + 1));
896	if (points == NULL) {
897	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
898	goto err;
899	}
900
901	var = points;
902	var[num] = NULL; /* pivot */
903	for (i = 0; i < num; i++) {
904	if ((var[i] = EC_POINT_new(group)) == NULL) {
905	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
906	goto err;
907	}
908	}
909
910	if ((tmp_point = EC_POINT_new(group)) == NULL
911	\|\| (base = EC_POINT_new(group)) == NULL) {
912	ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
913	goto err;
914	}
915
916	if (!EC_POINT_copy(base, generator))
917	goto err;
918
919	/* do the precomputation */
920	for (i = 0; i < numblocks; i++) {
921	size_t j;
922
923	if (!EC_POINT_dbl(group, tmp_point, base, ctx))
924	goto err;
925
926	if (!EC_POINT_copy(*var++, base))
927	goto err;
928
929	for (j = 1; j < pre_points_per_block; j++, var++) {
930	/*
931	* calculate odd multiples of the current base point
932	*/
933	if (!EC_POINT_add(group, var, tmp_point, (var - 1), ctx))
934	goto err;
935	}
936
937	if (i < numblocks - 1) {
938	/*
939	* get the next base (multiply current one by 2^blocksize)
940	*/
941	size_t k;
942
943	if (blocksize <= 2) {
944	ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
945	goto err;
946	}
947
948	if (!EC_POINT_dbl(group, base, tmp_point, ctx))
949	goto err;
950	for (k = 2; k < blocksize; k++) {
951	if (!EC_POINT_dbl(group, base, base, ctx))
952	goto err;
953	}
954	}
955	}
956
957	if (group->meth->points_make_affine == NULL
958	\|\| !group->meth->points_make_affine(group, num, points, ctx))
959	goto err;
960
961	pre_comp->group = group;
962	pre_comp->blocksize = blocksize;
963	pre_comp->numblocks = numblocks;
964	pre_comp->w = w;
965	pre_comp->points = points;
966	points = NULL;
967	pre_comp->num = num;
968	SETPRECOMP(group, ec, pre_comp);
969	pre_comp = NULL;
970	ret = 1;
971
972	err:
973	if (used_ctx)
974	BN_CTX_end(ctx);
975	#ifndef FIPS_MODULE
976	BN_CTX_free(new_ctx);
977	#endif
978	EC_ec_pre_comp_free(pre_comp);
979	if (points) {
980	EC_POINT **p;
981
982	for (p = points; *p != NULL; p++)
983	EC_POINT_free(*p);
984	OPENSSL_free(points);
985	}
986	EC_POINT_free(tmp_point);
987	EC_POINT_free(base);
988	return ret;
989	}
990
991	int ossl_ec_wNAF_have_precompute_mult(const EC_GROUP *group)
992	{
993	return HAVEPRECOMP(group, ec);
994	}

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source: vbox/trunk/src/libs/openssl-3.0.1/crypto/ec/ec_mult.c@ 94118

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