ecdsa.c revision 1.11
1/* $OpenBSD: ecdsa.c,v 1.11 2023/07/07 13:54:45 beck Exp $ */
2/* ====================================================================
3 * Copyright (c) 2000-2002 The OpenSSL Project.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in
14 *    the documentation and/or other materials provided with the
15 *    distribution.
16 *
17 * 3. All advertising materials mentioning features or use of this
18 *    software must display the following acknowledgment:
19 *    "This product includes software developed by the OpenSSL Project
20 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
21 *
22 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
23 *    endorse or promote products derived from this software without
24 *    prior written permission. For written permission, please contact
25 *    licensing@OpenSSL.org.
26 *
27 * 5. Products derived from this software may not be called "OpenSSL"
28 *    nor may "OpenSSL" appear in their names without prior written
29 *    permission of the OpenSSL Project.
30 *
31 * 6. Redistributions of any form whatsoever must retain the following
32 *    acknowledgment:
33 *    "This product includes software developed by the OpenSSL Project
34 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
35 *
36 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
37 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
38 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
39 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
40 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
41 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
42 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
43 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
45 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
46 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
47 * OF THE POSSIBILITY OF SUCH DAMAGE.
48 * ====================================================================
49 *
50 * This product includes cryptographic software written by Eric Young
51 * (eay@cryptsoft.com).  This product includes software written by Tim
52 * Hudson (tjh@cryptsoft.com).
53 *
54 */
55
56#include <stddef.h>
57#include <stdlib.h>
58#include <string.h>
59
60#include <openssl/opensslconf.h>
61
62#include <openssl/asn1.h>
63#include <openssl/asn1t.h>
64#include <openssl/bn.h>
65#include <openssl/ecdsa.h>
66#include <openssl/ec.h>
67#include <openssl/err.h>
68#include <openssl/evp.h>
69
70#include "bn_local.h"
71#include "ec_local.h"
72#include "ecdsa_local.h"
73
74static const ASN1_TEMPLATE ECDSA_SIG_seq_tt[] = {
75	{
76		.flags = 0,
77		.tag = 0,
78		.offset = offsetof(ECDSA_SIG, r),
79		.field_name = "r",
80		.item = &BIGNUM_it,
81	},
82	{
83		.flags = 0,
84		.tag = 0,
85		.offset = offsetof(ECDSA_SIG, s),
86		.field_name = "s",
87		.item = &BIGNUM_it,
88	},
89};
90
91const ASN1_ITEM ECDSA_SIG_it = {
92	.itype = ASN1_ITYPE_SEQUENCE,
93	.utype = V_ASN1_SEQUENCE,
94	.templates = ECDSA_SIG_seq_tt,
95	.tcount = sizeof(ECDSA_SIG_seq_tt) / sizeof(ASN1_TEMPLATE),
96	.funcs = NULL,
97	.size = sizeof(ECDSA_SIG),
98	.sname = "ECDSA_SIG",
99};
100
101ECDSA_SIG *
102d2i_ECDSA_SIG(ECDSA_SIG **a, const unsigned char **in, long len)
103{
104	return (ECDSA_SIG *)ASN1_item_d2i((ASN1_VALUE **)a, in, len,
105	    &ECDSA_SIG_it);
106}
107LCRYPTO_ALIAS(d2i_ECDSA_SIG);
108
109int
110i2d_ECDSA_SIG(const ECDSA_SIG *a, unsigned char **out)
111{
112	return ASN1_item_i2d((ASN1_VALUE *)a, out, &ECDSA_SIG_it);
113}
114LCRYPTO_ALIAS(i2d_ECDSA_SIG);
115
116ECDSA_SIG *
117ECDSA_SIG_new(void)
118{
119	return (ECDSA_SIG *)ASN1_item_new(&ECDSA_SIG_it);
120}
121LCRYPTO_ALIAS(ECDSA_SIG_new);
122
123void
124ECDSA_SIG_free(ECDSA_SIG *a)
125{
126	ASN1_item_free((ASN1_VALUE *)a, &ECDSA_SIG_it);
127}
128LCRYPTO_ALIAS(ECDSA_SIG_free);
129
130void
131ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps)
132{
133	if (pr != NULL)
134		*pr = sig->r;
135	if (ps != NULL)
136		*ps = sig->s;
137}
138LCRYPTO_ALIAS(ECDSA_SIG_get0);
139
140const BIGNUM *
141ECDSA_SIG_get0_r(const ECDSA_SIG *sig)
142{
143	return sig->r;
144}
145LCRYPTO_ALIAS(ECDSA_SIG_get0_r);
146
147const BIGNUM *
148ECDSA_SIG_get0_s(const ECDSA_SIG *sig)
149{
150	return sig->s;
151}
152LCRYPTO_ALIAS(ECDSA_SIG_get0_s);
153
154int
155ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s)
156{
157	if (r == NULL || s == NULL)
158		return 0;
159
160	BN_free(sig->r);
161	BN_free(sig->s);
162	sig->r = r;
163	sig->s = s;
164	return 1;
165}
166LCRYPTO_ALIAS(ECDSA_SIG_set0);
167
168int
169ECDSA_size(const EC_KEY *r)
170{
171	const EC_GROUP *group;
172	const BIGNUM *order = NULL;
173	ECDSA_SIG sig;
174	int ret = 0;
175
176	if (r == NULL)
177		goto err;
178
179	if ((group = EC_KEY_get0_group(r)) == NULL)
180		goto err;
181
182	if ((order = EC_GROUP_get0_order(group)) == NULL)
183		goto err;
184
185	sig.r = (BIGNUM *)order;
186	sig.s = (BIGNUM *)order;
187
188	if ((ret = i2d_ECDSA_SIG(&sig, NULL)) < 0)
189		ret = 0;
190
191 err:
192	return ret;
193}
194LCRYPTO_ALIAS(ECDSA_size);
195
196/*
197 * FIPS 186-5, section 6.4.1, step 2: convert hashed message into an integer.
198 * Use the order_bits leftmost bits if it exceeds the group order.
199 */
200static int
201ecdsa_prepare_digest(const unsigned char *digest, int digest_len,
202    const EC_KEY *key, BIGNUM *e)
203{
204	const EC_GROUP *group;
205	int digest_bits, order_bits;
206
207	if (BN_bin2bn(digest, digest_len, e) == NULL) {
208		ECerror(ERR_R_BN_LIB);
209		return 0;
210	}
211
212	if ((group = EC_KEY_get0_group(key)) == NULL)
213		return 0;
214	order_bits = EC_GROUP_order_bits(group);
215
216	digest_bits = 8 * digest_len;
217	if (digest_bits <= order_bits)
218		return 1;
219
220	return BN_rshift(e, e, digest_bits - order_bits);
221}
222
223int
224ecdsa_sign(int type, const unsigned char *digest, int digest_len,
225    unsigned char *signature, unsigned int *signature_len, const BIGNUM *kinv,
226    const BIGNUM *r, EC_KEY *key)
227{
228	ECDSA_SIG *sig;
229	int out_len = 0;
230	int ret = 0;
231
232	if ((sig = ECDSA_do_sign_ex(digest, digest_len, kinv, r, key)) == NULL)
233		goto err;
234
235	if ((out_len = i2d_ECDSA_SIG(sig, &signature)) < 0) {
236		out_len = 0;
237		goto err;
238	}
239
240	ret = 1;
241
242 err:
243	*signature_len = out_len;
244	ECDSA_SIG_free(sig);
245
246	return ret;
247}
248
249/*
250 * FIPS 186-5, section 6.4.1, steps 3-8 and 11: Generate k, calculate r and
251 * kinv. If r == 0, try again with a new random k.
252 */
253
254int
255ecdsa_sign_setup(EC_KEY *key, BN_CTX *in_ctx, BIGNUM **out_kinv, BIGNUM **out_r)
256{
257	const EC_GROUP *group;
258	EC_POINT *point = NULL;
259	BN_CTX *ctx = NULL;
260	BIGNUM *k = NULL, *r = NULL;
261	const BIGNUM *order;
262	BIGNUM *x;
263	int order_bits;
264	int ret = 0;
265
266	BN_free(*out_kinv);
267	*out_kinv = NULL;
268
269	BN_free(*out_r);
270	*out_r = NULL;
271
272	if (key == NULL) {
273		ECerror(ERR_R_PASSED_NULL_PARAMETER);
274		goto err;
275	}
276	if ((group = EC_KEY_get0_group(key)) == NULL) {
277		ECerror(ERR_R_PASSED_NULL_PARAMETER);
278		goto err;
279	}
280
281	if ((k = BN_new()) == NULL)
282		goto err;
283	if ((r = BN_new()) == NULL)
284		goto err;
285
286	if ((ctx = in_ctx) == NULL)
287		ctx = BN_CTX_new();
288	if (ctx == NULL) {
289		ECerror(ERR_R_MALLOC_FAILURE);
290		goto err;
291	}
292
293	BN_CTX_start(ctx);
294
295	if ((x = BN_CTX_get(ctx)) == NULL)
296		goto err;
297
298	if ((point = EC_POINT_new(group)) == NULL) {
299		ECerror(ERR_R_EC_LIB);
300		goto err;
301	}
302	if ((order = EC_GROUP_get0_order(group)) == NULL) {
303		ECerror(ERR_R_EC_LIB);
304		goto err;
305	}
306
307	if (BN_cmp(order, BN_value_one()) <= 0) {
308		ECerror(EC_R_INVALID_GROUP_ORDER);
309		goto err;
310	}
311
312	/* Reject curves with an order that is smaller than 80 bits. */
313	if ((order_bits = BN_num_bits(order)) < 80) {
314		ECerror(EC_R_INVALID_GROUP_ORDER);
315		goto err;
316	}
317
318	/* Preallocate space. */
319	if (!BN_set_bit(k, order_bits) ||
320	    !BN_set_bit(r, order_bits) ||
321	    !BN_set_bit(x, order_bits))
322		goto err;
323
324	/* Step 11: repeat until r != 0. */
325	do {
326		/* Step 3: generate random k. */
327		if (!bn_rand_interval(k, BN_value_one(), order))
328			goto err;
329
330		/*
331		 * We do not want timing information to leak the length of k,
332		 * so we compute G * k using an equivalent scalar of fixed
333		 * bit-length.
334		 *
335		 * We unconditionally perform both of these additions to prevent
336		 * a small timing information leakage.  We then choose the sum
337		 * that is one bit longer than the order.  This guarantees the
338		 * code path used in the constant time implementations
339		 * elsewhere.
340		 *
341		 * TODO: revisit the bn_copy aiming for a memory access agnostic
342		 * conditional copy.
343		 */
344		if (!BN_add(r, k, order) ||
345		    !BN_add(x, r, order) ||
346		    !bn_copy(k, BN_num_bits(r) > order_bits ? r : x))
347			goto err;
348
349		BN_set_flags(k, BN_FLG_CONSTTIME);
350
351		/* Step 5: P = k * G. */
352		if (!EC_POINT_mul(group, point, k, NULL, NULL, ctx)) {
353			ECerror(ERR_R_EC_LIB);
354			goto err;
355		}
356		/* Steps 6 (and 7): from P = (x, y) retain the x-coordinate. */
357		if (!EC_POINT_get_affine_coordinates(group, point, x, NULL,
358		    ctx)) {
359			ECerror(ERR_R_EC_LIB);
360			goto err;
361		}
362		/* Step 8: r = x (mod order). */
363		if (!BN_nnmod(r, x, order, ctx)) {
364			ECerror(ERR_R_BN_LIB);
365			goto err;
366		}
367	} while (BN_is_zero(r));
368
369	/* Step 4: calculate kinv. */
370	if (BN_mod_inverse_ct(k, k, order, ctx) == NULL) {
371		ECerror(ERR_R_BN_LIB);
372		goto err;
373	}
374
375	*out_kinv = k;
376	k = NULL;
377
378	*out_r = r;
379	r = NULL;
380
381	ret = 1;
382
383 err:
384	BN_CTX_end(ctx);
385	if (ctx != in_ctx)
386		BN_CTX_free(ctx);
387	BN_free(k);
388	BN_free(r);
389	EC_POINT_free(point);
390
391	return ret;
392}
393
394/*
395 * FIPS 186-5, section 6.4.1, step 9: compute s = inv(k)(e + xr) mod order.
396 * In order to reduce the possibility of a side-channel attack, the following
397 * is calculated using a random blinding value b in [1, order):
398 * s = inv(b)(be + bxr)inv(k) mod order.
399 */
400
401static int
402ecdsa_compute_s(BIGNUM **out_s, const BIGNUM *e, const BIGNUM *kinv,
403    const BIGNUM *r, const EC_KEY *key, BN_CTX *ctx)
404{
405	const EC_GROUP *group;
406	const BIGNUM *order, *priv_key;
407	BIGNUM *b, *binv, *be, *bxr;
408	BIGNUM *s = NULL;
409	int ret = 0;
410
411	*out_s = NULL;
412
413	BN_CTX_start(ctx);
414
415	if ((group = EC_KEY_get0_group(key)) == NULL) {
416		ECerror(ERR_R_PASSED_NULL_PARAMETER);
417		goto err;
418	}
419	if ((order = EC_GROUP_get0_order(group)) == NULL) {
420		ECerror(ERR_R_EC_LIB);
421		goto err;
422	}
423	if ((priv_key = EC_KEY_get0_private_key(key)) == NULL) {
424		ECerror(ERR_R_PASSED_NULL_PARAMETER);
425		goto err;
426	}
427
428	if ((b = BN_CTX_get(ctx)) == NULL)
429		goto err;
430	if ((binv = BN_CTX_get(ctx)) == NULL)
431		goto err;
432	if ((be = BN_CTX_get(ctx)) == NULL)
433		goto err;
434	if ((bxr = BN_CTX_get(ctx)) == NULL)
435		goto err;
436
437	if ((s = BN_new()) == NULL)
438		goto err;
439
440	/*
441	 * In a valid ECDSA signature, r must be in [1, order). Since r can be
442	 * caller provided - either directly or by replacing sign_setup() - we
443	 * can't rely on this being the case.
444	 */
445	if (BN_cmp(r, BN_value_one()) < 0 || BN_cmp(r, order) >= 0) {
446		ECerror(EC_R_BAD_SIGNATURE);
447		goto err;
448	}
449
450	if (!bn_rand_interval(b, BN_value_one(), order)) {
451		ECerror(ERR_R_BN_LIB);
452		goto err;
453	}
454
455	if (BN_mod_inverse_ct(binv, b, order, ctx) == NULL) {
456		ECerror(ERR_R_BN_LIB);
457		goto err;
458	}
459
460	if (!BN_mod_mul(bxr, b, priv_key, order, ctx)) {
461		ECerror(ERR_R_BN_LIB);
462		goto err;
463	}
464	if (!BN_mod_mul(bxr, bxr, r, order, ctx)) {
465		ECerror(ERR_R_BN_LIB);
466		goto err;
467	}
468	if (!BN_mod_mul(be, b, e, order, ctx)) {
469		ECerror(ERR_R_BN_LIB);
470		goto err;
471	}
472	if (!BN_mod_add(s, be, bxr, order, ctx)) {
473		ECerror(ERR_R_BN_LIB);
474		goto err;
475	}
476	/* s = b(e + xr)k^-1 */
477	if (!BN_mod_mul(s, s, kinv, order, ctx)) {
478		ECerror(ERR_R_BN_LIB);
479		goto err;
480	}
481	/* s = (e + xr)k^-1 */
482	if (!BN_mod_mul(s, s, binv, order, ctx)) {
483		ECerror(ERR_R_BN_LIB);
484		goto err;
485	}
486
487	/* Step 11: if s == 0 start over. */
488	if (!BN_is_zero(s)) {
489		*out_s = s;
490		s = NULL;
491	}
492
493	ret = 1;
494
495 err:
496	BN_CTX_end(ctx);
497	BN_free(s);
498
499	return ret;
500}
501
502/*
503 * It is too expensive to check curve parameters on every sign operation.
504 * Instead, cap the number of retries. A single retry is very unlikely, so
505 * allowing 32 retries is amply enough.
506 */
507#define ECDSA_MAX_SIGN_ITERATIONS		32
508
509/*
510 * FIPS 186-5: Section 6.4.1: ECDSA signature generation, steps 2-12.
511 * The caller provides the hash of the message, thus performs step 1.
512 * Step 10, zeroing k and kinv, is done by BN_free().
513 */
514
515ECDSA_SIG *
516ecdsa_sign_sig(const unsigned char *digest, int digest_len,
517    const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *key)
518{
519	BN_CTX *ctx = NULL;
520	BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
521	BIGNUM *e;
522	int caller_supplied_values = 0;
523	int attempts = 0;
524	ECDSA_SIG *sig = NULL;
525
526	if ((ctx = BN_CTX_new()) == NULL) {
527		ECerror(ERR_R_MALLOC_FAILURE);
528		goto err;
529	}
530
531	BN_CTX_start(ctx);
532
533	if ((e = BN_CTX_get(ctx)) == NULL)
534		goto err;
535
536	/* Step 2: convert hash into an integer. */
537	if (!ecdsa_prepare_digest(digest, digest_len, key, e))
538		goto err;
539
540	if (in_kinv != NULL && in_r != NULL) {
541		/*
542		 * Use the caller's kinv and r. Don't call ECDSA_sign_setup().
543		 * If we're unable to compute a valid signature, the caller
544		 * must provide new values.
545		 */
546		caller_supplied_values = 1;
547
548		if ((kinv = BN_dup(in_kinv)) == NULL) {
549			ECerror(ERR_R_MALLOC_FAILURE);
550			goto err;
551		}
552		if ((r = BN_dup(in_r)) == NULL) {
553			ECerror(ERR_R_MALLOC_FAILURE);
554			goto err;
555		}
556	}
557
558	do {
559		/* Steps 3-8: calculate kinv and r. */
560		if (!caller_supplied_values) {
561			if (!ECDSA_sign_setup(key, ctx, &kinv, &r)) {
562				ECerror(ERR_R_EC_LIB);
563				goto err;
564			}
565		}
566
567		/*
568		 * Steps 9 and 11: if s is non-NULL, we have a valid signature.
569		 */
570		if (!ecdsa_compute_s(&s, e, kinv, r, key, ctx))
571			goto err;
572		if (s != NULL)
573			break;
574
575		if (caller_supplied_values) {
576			ECerror(EC_R_NEED_NEW_SETUP_VALUES);
577			goto err;
578		}
579
580		if (++attempts > ECDSA_MAX_SIGN_ITERATIONS) {
581			ECerror(EC_R_WRONG_CURVE_PARAMETERS);
582			goto err;
583		}
584	} while (1);
585
586	/* Step 12: output (r, s). */
587	if ((sig = ECDSA_SIG_new()) == NULL) {
588		ECerror(ERR_R_MALLOC_FAILURE);
589		goto err;
590	}
591	if (!ECDSA_SIG_set0(sig, r, s)) {
592		ECDSA_SIG_free(sig);
593		goto err;
594	}
595	r = NULL;
596	s = NULL;
597
598 err:
599	BN_CTX_end(ctx);
600	BN_CTX_free(ctx);
601	BN_free(kinv);
602	BN_free(r);
603	BN_free(s);
604
605	return sig;
606}
607
608int
609ecdsa_verify(int type, const unsigned char *digest, int digest_len,
610    const unsigned char *sigbuf, int sig_len, EC_KEY *key)
611{
612	ECDSA_SIG *s;
613	unsigned char *der = NULL;
614	const unsigned char *p;
615	int der_len = 0;
616	int ret = -1;
617
618	if ((s = ECDSA_SIG_new()) == NULL)
619		goto err;
620
621	p = sigbuf;
622	if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
623		goto err;
624
625	/* Ensure signature uses DER and doesn't have trailing garbage. */
626	if ((der_len = i2d_ECDSA_SIG(s, &der)) != sig_len)
627		goto err;
628	if (timingsafe_memcmp(sigbuf, der, der_len))
629		goto err;
630
631	ret = ECDSA_do_verify(digest, digest_len, s, key);
632
633 err:
634	freezero(der, der_len);
635	ECDSA_SIG_free(s);
636
637	return ret;
638}
639
640/*
641 * FIPS 186-5, section 6.4.2: ECDSA signature verification.
642 * The caller provides us with the hash of the message, so has performed step 2.
643 */
644
645int
646ecdsa_verify_sig(const unsigned char *digest, int digest_len,
647    const ECDSA_SIG *sig, EC_KEY *key)
648{
649	const EC_GROUP *group;
650	const EC_POINT *pub_key;
651	EC_POINT *point = NULL;
652	const BIGNUM *order;
653	BN_CTX *ctx = NULL;
654	BIGNUM *e, *sinv, *u, *v, *x;
655	int ret = -1;
656
657	if (key == NULL || sig == NULL) {
658		ECerror(EC_R_MISSING_PARAMETERS);
659		goto err;
660	}
661	if ((group = EC_KEY_get0_group(key)) == NULL) {
662		ECerror(EC_R_MISSING_PARAMETERS);
663		goto err;
664	}
665	if ((pub_key = EC_KEY_get0_public_key(key)) == NULL) {
666		ECerror(EC_R_MISSING_PARAMETERS);
667		goto err;
668	}
669
670	if ((ctx = BN_CTX_new()) == NULL) {
671		ECerror(ERR_R_MALLOC_FAILURE);
672		goto err;
673	}
674
675	BN_CTX_start(ctx);
676
677	if ((e = BN_CTX_get(ctx)) == NULL)
678		goto err;
679	if ((sinv = BN_CTX_get(ctx)) == NULL)
680		goto err;
681	if ((u = BN_CTX_get(ctx)) == NULL)
682		goto err;
683	if ((v = BN_CTX_get(ctx)) == NULL)
684		goto err;
685	if ((x = BN_CTX_get(ctx)) == NULL)
686		goto err;
687
688	if ((order = EC_GROUP_get0_order(group)) == NULL) {
689		ECerror(ERR_R_EC_LIB);
690		goto err;
691	}
692
693	/* Step 1: verify that r and s are in the range [1, order). */
694	if (BN_cmp(sig->r, BN_value_one()) < 0 || BN_cmp(sig->r, order) >= 0) {
695		ECerror(EC_R_BAD_SIGNATURE);
696		ret = 0;
697		goto err;
698	}
699	if (BN_cmp(sig->s, BN_value_one()) < 0 || BN_cmp(sig->s, order) >= 0) {
700		ECerror(EC_R_BAD_SIGNATURE);
701		ret = 0;
702		goto err;
703	}
704
705	/* Step 3: convert the hash into an integer. */
706	if (!ecdsa_prepare_digest(digest, digest_len, key, e))
707		goto err;
708
709	/* Step 4: compute the inverse of s modulo order. */
710	if (BN_mod_inverse_ct(sinv, sig->s, order, ctx) == NULL) {
711		ECerror(ERR_R_BN_LIB);
712		goto err;
713	}
714	/* Step 5: compute u = s^-1 * e and v = s^-1 * r (modulo order). */
715	if (!BN_mod_mul(u, e, sinv, order, ctx)) {
716		ECerror(ERR_R_BN_LIB);
717		goto err;
718	}
719	if (!BN_mod_mul(v, sig->r, sinv, order, ctx)) {
720		ECerror(ERR_R_BN_LIB);
721		goto err;
722	}
723
724	/*
725	 * Steps 6 and 7: compute R = G * u + pub_key * v = (x, y). Reject if
726	 * it's the point at infinity - getting affine coordinates fails. Keep
727	 * the x coordinate.
728	 */
729	if ((point = EC_POINT_new(group)) == NULL) {
730		ECerror(ERR_R_MALLOC_FAILURE);
731		goto err;
732	}
733	if (!EC_POINT_mul(group, point, u, pub_key, v, ctx)) {
734		ECerror(ERR_R_EC_LIB);
735		goto err;
736	}
737	if (!EC_POINT_get_affine_coordinates(group, point, x, NULL, ctx)) {
738		ECerror(ERR_R_EC_LIB);
739		goto err;
740	}
741	/* Step 8: convert x to a number in [0, order). */
742	if (!BN_nnmod(x, x, order, ctx)) {
743		ECerror(ERR_R_BN_LIB);
744		goto err;
745	}
746
747	/* Step 9: the signature is valid iff the x-coordinate is equal to r. */
748	ret = (BN_cmp(x, sig->r) == 0);
749
750 err:
751	BN_CTX_end(ctx);
752	BN_CTX_free(ctx);
753	EC_POINT_free(point);
754
755	return ret;
756}
757
758ECDSA_SIG *
759ECDSA_do_sign(const unsigned char *digest, int digest_len, EC_KEY *key)
760{
761	return ECDSA_do_sign_ex(digest, digest_len, NULL, NULL, key);
762}
763LCRYPTO_ALIAS(ECDSA_do_sign);
764
765ECDSA_SIG *
766ECDSA_do_sign_ex(const unsigned char *digest, int digest_len,
767    const BIGNUM *kinv, const BIGNUM *out_r, EC_KEY *key)
768{
769	if (key->meth->sign_sig == NULL) {
770		ECerror(EC_R_NOT_IMPLEMENTED);
771		return 0;
772	}
773	return key->meth->sign_sig(digest, digest_len, kinv, out_r, key);
774}
775LCRYPTO_ALIAS(ECDSA_do_sign_ex);
776
777int
778ECDSA_sign(int type, const unsigned char *digest, int digest_len,
779    unsigned char *signature, unsigned int *signature_len, EC_KEY *key)
780{
781	return ECDSA_sign_ex(type, digest, digest_len, signature, signature_len,
782	    NULL, NULL, key);
783}
784LCRYPTO_ALIAS(ECDSA_sign);
785
786int
787ECDSA_sign_ex(int type, const unsigned char *digest, int digest_len,
788    unsigned char *signature, unsigned int *signature_len, const BIGNUM *kinv,
789    const BIGNUM *r, EC_KEY *key)
790{
791	if (key->meth->sign == NULL) {
792		ECerror(EC_R_NOT_IMPLEMENTED);
793		return 0;
794	}
795	return key->meth->sign(type, digest, digest_len, signature,
796	    signature_len, kinv, r, key);
797}
798LCRYPTO_ALIAS(ECDSA_sign_ex);
799
800int
801ECDSA_sign_setup(EC_KEY *key, BN_CTX *in_ctx, BIGNUM **out_kinv,
802    BIGNUM **out_r)
803{
804	if (key->meth->sign_setup == NULL) {
805		ECerror(EC_R_NOT_IMPLEMENTED);
806		return 0;
807	}
808	return key->meth->sign_setup(key, in_ctx, out_kinv, out_r);
809}
810LCRYPTO_ALIAS(ECDSA_sign_setup);
811
812int
813ECDSA_do_verify(const unsigned char *digest, int digest_len,
814    const ECDSA_SIG *sig, EC_KEY *key)
815{
816	if (key->meth->verify_sig == NULL) {
817		ECerror(EC_R_NOT_IMPLEMENTED);
818		return 0;
819	}
820	return key->meth->verify_sig(digest, digest_len, sig, key);
821}
822LCRYPTO_ALIAS(ECDSA_do_verify);
823
824int
825ECDSA_verify(int type, const unsigned char *digest, int digest_len,
826    const unsigned char *sigbuf, int sig_len, EC_KEY *key)
827{
828	if (key->meth->verify == NULL) {
829		ECerror(EC_R_NOT_IMPLEMENTED);
830		return 0;
831	}
832	return key->meth->verify(type, digest, digest_len, sigbuf, sig_len, key);
833}
834LCRYPTO_ALIAS(ECDSA_verify);
835