796 lines
18 KiB
C
796 lines
18 KiB
C
/* $OpenBSD: ecdsa.c,v 1.16 2023/07/28 09:18:10 tb Exp $ */
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/* ====================================================================
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* Copyright (c) 2000-2002 The OpenSSL Project. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. All advertising materials mentioning features or use of this
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* software must display the following acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
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*
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* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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* endorse or promote products derived from this software without
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* prior written permission. For written permission, please contact
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* licensing@OpenSSL.org.
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*
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* 5. Products derived from this software may not be called "OpenSSL"
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* nor may "OpenSSL" appear in their names without prior written
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* permission of the OpenSSL Project.
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*
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* 6. Redistributions of any form whatsoever must retain the following
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* acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
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*
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* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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* ====================================================================
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*
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* This product includes cryptographic software written by Eric Young
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* (eay@cryptsoft.com). This product includes software written by Tim
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* Hudson (tjh@cryptsoft.com).
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*
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*/
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#include <stddef.h>
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#include <stdlib.h>
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#include <string.h>
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#include <openssl/asn1.h>
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#include <openssl/asn1t.h>
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#include <openssl/bn.h>
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#include <openssl/ec.h>
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#include <openssl/err.h>
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#include "bn_local.h"
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#include "ec_local.h"
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#include "ecdsa_local.h"
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static const ASN1_TEMPLATE ECDSA_SIG_seq_tt[] = {
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{
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.flags = 0,
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.tag = 0,
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.offset = offsetof(ECDSA_SIG, r),
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.field_name = "r",
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.item = &BIGNUM_it,
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},
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{
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.flags = 0,
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.tag = 0,
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.offset = offsetof(ECDSA_SIG, s),
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.field_name = "s",
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.item = &BIGNUM_it,
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},
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};
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const ASN1_ITEM ECDSA_SIG_it = {
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.itype = ASN1_ITYPE_SEQUENCE,
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.utype = V_ASN1_SEQUENCE,
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.templates = ECDSA_SIG_seq_tt,
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.tcount = sizeof(ECDSA_SIG_seq_tt) / sizeof(ASN1_TEMPLATE),
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.funcs = NULL,
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.size = sizeof(ECDSA_SIG),
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.sname = "ECDSA_SIG",
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};
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ECDSA_SIG *
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d2i_ECDSA_SIG(ECDSA_SIG **a, const unsigned char **in, long len)
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{
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return (ECDSA_SIG *)ASN1_item_d2i((ASN1_VALUE **)a, in, len,
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&ECDSA_SIG_it);
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}
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LCRYPTO_ALIAS(d2i_ECDSA_SIG);
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int
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i2d_ECDSA_SIG(const ECDSA_SIG *a, unsigned char **out)
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{
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return ASN1_item_i2d((ASN1_VALUE *)a, out, &ECDSA_SIG_it);
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}
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LCRYPTO_ALIAS(i2d_ECDSA_SIG);
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ECDSA_SIG *
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ECDSA_SIG_new(void)
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{
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return (ECDSA_SIG *)ASN1_item_new(&ECDSA_SIG_it);
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}
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LCRYPTO_ALIAS(ECDSA_SIG_new);
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void
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ECDSA_SIG_free(ECDSA_SIG *a)
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{
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ASN1_item_free((ASN1_VALUE *)a, &ECDSA_SIG_it);
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}
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LCRYPTO_ALIAS(ECDSA_SIG_free);
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void
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ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps)
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{
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if (pr != NULL)
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*pr = sig->r;
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if (ps != NULL)
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*ps = sig->s;
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}
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LCRYPTO_ALIAS(ECDSA_SIG_get0);
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const BIGNUM *
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ECDSA_SIG_get0_r(const ECDSA_SIG *sig)
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{
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return sig->r;
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}
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LCRYPTO_ALIAS(ECDSA_SIG_get0_r);
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const BIGNUM *
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ECDSA_SIG_get0_s(const ECDSA_SIG *sig)
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{
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return sig->s;
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}
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LCRYPTO_ALIAS(ECDSA_SIG_get0_s);
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int
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ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s)
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{
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if (r == NULL || s == NULL)
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return 0;
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BN_free(sig->r);
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BN_free(sig->s);
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sig->r = r;
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sig->s = s;
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return 1;
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}
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LCRYPTO_ALIAS(ECDSA_SIG_set0);
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int
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ECDSA_size(const EC_KEY *key)
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{
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const EC_GROUP *group;
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const BIGNUM *order = NULL;
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ECDSA_SIG sig;
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int ret = 0;
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if (key == NULL)
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goto err;
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if ((group = EC_KEY_get0_group(key)) == NULL)
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goto err;
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if ((order = EC_GROUP_get0_order(group)) == NULL)
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goto err;
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sig.r = (BIGNUM *)order;
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sig.s = (BIGNUM *)order;
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if ((ret = i2d_ECDSA_SIG(&sig, NULL)) < 0)
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ret = 0;
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err:
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return ret;
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}
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LCRYPTO_ALIAS(ECDSA_size);
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/*
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* FIPS 186-5, section 6.4.1, step 2: convert hashed message into an integer.
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* Use the order_bits leftmost bits if it exceeds the group order.
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*/
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static int
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ecdsa_prepare_digest(const unsigned char *digest, int digest_len,
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const EC_KEY *key, BIGNUM *e)
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{
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const EC_GROUP *group;
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int digest_bits, order_bits;
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if (BN_bin2bn(digest, digest_len, e) == NULL) {
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ECerror(ERR_R_BN_LIB);
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return 0;
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}
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if ((group = EC_KEY_get0_group(key)) == NULL)
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return 0;
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order_bits = EC_GROUP_order_bits(group);
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digest_bits = 8 * digest_len;
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if (digest_bits <= order_bits)
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return 1;
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return BN_rshift(e, e, digest_bits - order_bits);
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}
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int
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ecdsa_sign(int type, const unsigned char *digest, int digest_len,
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unsigned char *signature, unsigned int *signature_len, const BIGNUM *kinv,
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const BIGNUM *r, EC_KEY *key)
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{
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ECDSA_SIG *sig = NULL;
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int out_len = 0;
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int ret = 0;
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if (kinv != NULL || r != NULL) {
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ECerror(EC_R_NOT_IMPLEMENTED);
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goto err;
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}
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if ((sig = ECDSA_do_sign(digest, digest_len, key)) == NULL)
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goto err;
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if ((out_len = i2d_ECDSA_SIG(sig, &signature)) < 0) {
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out_len = 0;
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goto err;
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}
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ret = 1;
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err:
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*signature_len = out_len;
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ECDSA_SIG_free(sig);
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return ret;
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}
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int
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ECDSA_sign(int type, const unsigned char *digest, int digest_len,
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unsigned char *signature, unsigned int *signature_len, EC_KEY *key)
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{
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if (key->meth->sign == NULL) {
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ECerror(EC_R_NOT_IMPLEMENTED);
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return 0;
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}
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return key->meth->sign(type, digest, digest_len, signature,
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signature_len, NULL, NULL, key);
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}
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LCRYPTO_ALIAS(ECDSA_sign);
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/*
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* FIPS 186-5, section 6.4.1, steps 3-8 and 11: Generate k, calculate r and
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* kinv. If r == 0, try again with a new random k.
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*/
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int
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ecdsa_sign_setup(EC_KEY *key, BN_CTX *in_ctx, BIGNUM **out_kinv, BIGNUM **out_r)
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{
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const EC_GROUP *group;
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EC_POINT *point = NULL;
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BN_CTX *ctx = NULL;
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BIGNUM *k = NULL, *r = NULL;
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const BIGNUM *order;
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BIGNUM *x;
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int order_bits;
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int ret = 0;
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BN_free(*out_kinv);
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*out_kinv = NULL;
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BN_free(*out_r);
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*out_r = NULL;
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if (key == NULL) {
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ECerror(ERR_R_PASSED_NULL_PARAMETER);
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goto err;
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}
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if ((group = EC_KEY_get0_group(key)) == NULL) {
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ECerror(ERR_R_PASSED_NULL_PARAMETER);
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goto err;
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}
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if ((k = BN_new()) == NULL)
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goto err;
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if ((r = BN_new()) == NULL)
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goto err;
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if ((ctx = in_ctx) == NULL)
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ctx = BN_CTX_new();
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if (ctx == NULL) {
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ECerror(ERR_R_MALLOC_FAILURE);
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goto err;
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}
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BN_CTX_start(ctx);
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if ((x = BN_CTX_get(ctx)) == NULL)
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goto err;
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if ((point = EC_POINT_new(group)) == NULL) {
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ECerror(ERR_R_EC_LIB);
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goto err;
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}
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if ((order = EC_GROUP_get0_order(group)) == NULL) {
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ECerror(ERR_R_EC_LIB);
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goto err;
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}
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if (BN_cmp(order, BN_value_one()) <= 0) {
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ECerror(EC_R_INVALID_GROUP_ORDER);
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goto err;
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}
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/* Reject curves with an order that is smaller than 80 bits. */
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if ((order_bits = BN_num_bits(order)) < 80) {
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ECerror(EC_R_INVALID_GROUP_ORDER);
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goto err;
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}
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/* Preallocate space. */
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if (!BN_set_bit(k, order_bits) ||
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!BN_set_bit(r, order_bits) ||
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!BN_set_bit(x, order_bits))
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goto err;
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/* Step 11: repeat until r != 0. */
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do {
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/* Step 3: generate random k. */
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if (!bn_rand_interval(k, BN_value_one(), order))
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goto err;
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/*
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* We do not want timing information to leak the length of k,
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* so we compute G * k using an equivalent scalar of fixed
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* bit-length.
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*
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* We unconditionally perform both of these additions to prevent
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* a small timing information leakage. We then choose the sum
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* that is one bit longer than the order. This guarantees the
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* code path used in the constant time implementations
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* elsewhere.
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*
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* TODO: revisit the bn_copy aiming for a memory access agnostic
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* conditional copy.
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*/
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if (!BN_add(r, k, order) ||
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!BN_add(x, r, order) ||
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!bn_copy(k, BN_num_bits(r) > order_bits ? r : x))
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goto err;
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BN_set_flags(k, BN_FLG_CONSTTIME);
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/* Step 5: P = k * G. */
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if (!EC_POINT_mul(group, point, k, NULL, NULL, ctx)) {
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ECerror(ERR_R_EC_LIB);
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goto err;
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}
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/* Steps 6 (and 7): from P = (x, y) retain the x-coordinate. */
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if (!EC_POINT_get_affine_coordinates(group, point, x, NULL,
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ctx)) {
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ECerror(ERR_R_EC_LIB);
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goto err;
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}
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/* Step 8: r = x (mod order). */
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if (!BN_nnmod(r, x, order, ctx)) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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} while (BN_is_zero(r));
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/* Step 4: calculate kinv. */
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if (BN_mod_inverse_ct(k, k, order, ctx) == NULL) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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*out_kinv = k;
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k = NULL;
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*out_r = r;
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r = NULL;
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ret = 1;
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err:
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BN_CTX_end(ctx);
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if (ctx != in_ctx)
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BN_CTX_free(ctx);
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BN_free(k);
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BN_free(r);
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EC_POINT_free(point);
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return ret;
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}
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static int
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ECDSA_sign_setup(EC_KEY *key, BN_CTX *in_ctx, BIGNUM **out_kinv,
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BIGNUM **out_r)
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{
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if (key->meth->sign_setup == NULL) {
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ECerror(EC_R_NOT_IMPLEMENTED);
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return 0;
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}
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return key->meth->sign_setup(key, in_ctx, out_kinv, out_r);
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}
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/*
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* FIPS 186-5, section 6.4.1, step 9: compute s = inv(k)(e + xr) mod order.
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* In order to reduce the possibility of a side-channel attack, the following
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* is calculated using a random blinding value b in [1, order):
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* s = inv(b)(be + bxr)inv(k) mod order.
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*/
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static int
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ecdsa_compute_s(BIGNUM **out_s, const BIGNUM *e, const BIGNUM *kinv,
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const BIGNUM *r, const EC_KEY *key, BN_CTX *ctx)
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{
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const EC_GROUP *group;
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const BIGNUM *order, *priv_key;
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BIGNUM *b, *binv, *be, *bxr;
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BIGNUM *s = NULL;
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int ret = 0;
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*out_s = NULL;
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BN_CTX_start(ctx);
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if ((group = EC_KEY_get0_group(key)) == NULL) {
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ECerror(ERR_R_PASSED_NULL_PARAMETER);
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goto err;
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}
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if ((order = EC_GROUP_get0_order(group)) == NULL) {
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ECerror(ERR_R_EC_LIB);
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goto err;
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}
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if ((priv_key = EC_KEY_get0_private_key(key)) == NULL) {
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ECerror(ERR_R_PASSED_NULL_PARAMETER);
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goto err;
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}
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if ((b = BN_CTX_get(ctx)) == NULL)
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goto err;
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if ((binv = BN_CTX_get(ctx)) == NULL)
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goto err;
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if ((be = BN_CTX_get(ctx)) == NULL)
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goto err;
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if ((bxr = BN_CTX_get(ctx)) == NULL)
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goto err;
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if ((s = BN_new()) == NULL)
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goto err;
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/*
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* In a valid ECDSA signature, r must be in [1, order). Since r can be
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* caller provided - either directly or by replacing sign_setup() - we
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* can't rely on this being the case.
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*/
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if (BN_cmp(r, BN_value_one()) < 0 || BN_cmp(r, order) >= 0) {
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ECerror(EC_R_BAD_SIGNATURE);
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goto err;
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}
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if (!bn_rand_interval(b, BN_value_one(), order)) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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if (BN_mod_inverse_ct(binv, b, order, ctx) == NULL) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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if (!BN_mod_mul(bxr, b, priv_key, order, ctx)) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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if (!BN_mod_mul(bxr, bxr, r, order, ctx)) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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if (!BN_mod_mul(be, b, e, order, ctx)) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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if (!BN_mod_add(s, be, bxr, order, ctx)) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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/* s = b(e + xr)k^-1 */
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if (!BN_mod_mul(s, s, kinv, order, ctx)) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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/* s = (e + xr)k^-1 */
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if (!BN_mod_mul(s, s, binv, order, ctx)) {
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ECerror(ERR_R_BN_LIB);
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goto err;
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}
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/* Step 11: if s == 0 start over. */
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if (!BN_is_zero(s)) {
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*out_s = s;
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s = NULL;
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}
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ret = 1;
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err:
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BN_CTX_end(ctx);
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BN_free(s);
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return ret;
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}
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/*
|
|
* It is too expensive to check curve parameters on every sign operation.
|
|
* Instead, cap the number of retries. A single retry is very unlikely, so
|
|
* allowing 32 retries is amply enough.
|
|
*/
|
|
#define ECDSA_MAX_SIGN_ITERATIONS 32
|
|
|
|
/*
|
|
* FIPS 186-5: Section 6.4.1: ECDSA signature generation, steps 2-12.
|
|
* The caller provides the hash of the message, thus performs step 1.
|
|
* Step 10, zeroing k and kinv, is done by BN_free().
|
|
*/
|
|
|
|
ECDSA_SIG *
|
|
ecdsa_sign_sig(const unsigned char *digest, int digest_len,
|
|
const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *key)
|
|
{
|
|
BN_CTX *ctx = NULL;
|
|
BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
|
|
BIGNUM *e;
|
|
int attempts = 0;
|
|
ECDSA_SIG *sig = NULL;
|
|
|
|
if (in_kinv != NULL || in_r != NULL) {
|
|
ECerror(EC_R_NOT_IMPLEMENTED);
|
|
goto err;
|
|
}
|
|
|
|
if ((ctx = BN_CTX_new()) == NULL) {
|
|
ECerror(ERR_R_MALLOC_FAILURE);
|
|
goto err;
|
|
}
|
|
|
|
BN_CTX_start(ctx);
|
|
|
|
if ((e = BN_CTX_get(ctx)) == NULL)
|
|
goto err;
|
|
|
|
/* Step 2: convert hash into an integer. */
|
|
if (!ecdsa_prepare_digest(digest, digest_len, key, e))
|
|
goto err;
|
|
|
|
do {
|
|
/* Steps 3-8: calculate kinv and r. */
|
|
if (!ECDSA_sign_setup(key, ctx, &kinv, &r)) {
|
|
ECerror(ERR_R_EC_LIB);
|
|
goto err;
|
|
}
|
|
|
|
/*
|
|
* Steps 9 and 11: if s is non-NULL, we have a valid signature.
|
|
*/
|
|
if (!ecdsa_compute_s(&s, e, kinv, r, key, ctx))
|
|
goto err;
|
|
if (s != NULL)
|
|
break;
|
|
|
|
if (++attempts > ECDSA_MAX_SIGN_ITERATIONS) {
|
|
ECerror(EC_R_WRONG_CURVE_PARAMETERS);
|
|
goto err;
|
|
}
|
|
} while (1);
|
|
|
|
/* Step 12: output (r, s). */
|
|
if ((sig = ECDSA_SIG_new()) == NULL) {
|
|
ECerror(ERR_R_MALLOC_FAILURE);
|
|
goto err;
|
|
}
|
|
if (!ECDSA_SIG_set0(sig, r, s)) {
|
|
ECDSA_SIG_free(sig);
|
|
goto err;
|
|
}
|
|
r = NULL;
|
|
s = NULL;
|
|
|
|
err:
|
|
BN_CTX_end(ctx);
|
|
BN_CTX_free(ctx);
|
|
BN_free(kinv);
|
|
BN_free(r);
|
|
BN_free(s);
|
|
|
|
return sig;
|
|
}
|
|
|
|
ECDSA_SIG *
|
|
ECDSA_do_sign(const unsigned char *digest, int digest_len, EC_KEY *key)
|
|
{
|
|
if (key->meth->sign_sig == NULL) {
|
|
ECerror(EC_R_NOT_IMPLEMENTED);
|
|
return 0;
|
|
}
|
|
return key->meth->sign_sig(digest, digest_len, NULL, NULL, key);
|
|
}
|
|
LCRYPTO_ALIAS(ECDSA_do_sign);
|
|
|
|
int
|
|
ecdsa_verify(int type, const unsigned char *digest, int digest_len,
|
|
const unsigned char *sigbuf, int sig_len, EC_KEY *key)
|
|
{
|
|
ECDSA_SIG *s;
|
|
unsigned char *der = NULL;
|
|
const unsigned char *p;
|
|
int der_len = 0;
|
|
int ret = -1;
|
|
|
|
if ((s = ECDSA_SIG_new()) == NULL)
|
|
goto err;
|
|
|
|
p = sigbuf;
|
|
if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
|
|
goto err;
|
|
|
|
/* Ensure signature uses DER and doesn't have trailing garbage. */
|
|
if ((der_len = i2d_ECDSA_SIG(s, &der)) != sig_len)
|
|
goto err;
|
|
if (timingsafe_memcmp(sigbuf, der, der_len))
|
|
goto err;
|
|
|
|
ret = ECDSA_do_verify(digest, digest_len, s, key);
|
|
|
|
err:
|
|
freezero(der, der_len);
|
|
ECDSA_SIG_free(s);
|
|
|
|
return ret;
|
|
}
|
|
|
|
int
|
|
ECDSA_verify(int type, const unsigned char *digest, int digest_len,
|
|
const unsigned char *sigbuf, int sig_len, EC_KEY *key)
|
|
{
|
|
if (key->meth->verify == NULL) {
|
|
ECerror(EC_R_NOT_IMPLEMENTED);
|
|
return 0;
|
|
}
|
|
return key->meth->verify(type, digest, digest_len, sigbuf, sig_len, key);
|
|
}
|
|
LCRYPTO_ALIAS(ECDSA_verify);
|
|
|
|
/*
|
|
* FIPS 186-5, section 6.4.2: ECDSA signature verification.
|
|
* The caller provides us with the hash of the message, so has performed step 2.
|
|
*/
|
|
|
|
int
|
|
ecdsa_verify_sig(const unsigned char *digest, int digest_len,
|
|
const ECDSA_SIG *sig, EC_KEY *key)
|
|
{
|
|
const EC_GROUP *group;
|
|
const EC_POINT *pub_key;
|
|
EC_POINT *point = NULL;
|
|
const BIGNUM *order;
|
|
BN_CTX *ctx = NULL;
|
|
BIGNUM *e, *sinv, *u, *v, *x;
|
|
int ret = -1;
|
|
|
|
if (key == NULL || sig == NULL) {
|
|
ECerror(EC_R_MISSING_PARAMETERS);
|
|
goto err;
|
|
}
|
|
if ((group = EC_KEY_get0_group(key)) == NULL) {
|
|
ECerror(EC_R_MISSING_PARAMETERS);
|
|
goto err;
|
|
}
|
|
if ((pub_key = EC_KEY_get0_public_key(key)) == NULL) {
|
|
ECerror(EC_R_MISSING_PARAMETERS);
|
|
goto err;
|
|
}
|
|
|
|
if ((ctx = BN_CTX_new()) == NULL) {
|
|
ECerror(ERR_R_MALLOC_FAILURE);
|
|
goto err;
|
|
}
|
|
|
|
BN_CTX_start(ctx);
|
|
|
|
if ((e = BN_CTX_get(ctx)) == NULL)
|
|
goto err;
|
|
if ((sinv = BN_CTX_get(ctx)) == NULL)
|
|
goto err;
|
|
if ((u = BN_CTX_get(ctx)) == NULL)
|
|
goto err;
|
|
if ((v = BN_CTX_get(ctx)) == NULL)
|
|
goto err;
|
|
if ((x = BN_CTX_get(ctx)) == NULL)
|
|
goto err;
|
|
|
|
if ((order = EC_GROUP_get0_order(group)) == NULL) {
|
|
ECerror(ERR_R_EC_LIB);
|
|
goto err;
|
|
}
|
|
|
|
/* Step 1: verify that r and s are in the range [1, order). */
|
|
if (BN_cmp(sig->r, BN_value_one()) < 0 || BN_cmp(sig->r, order) >= 0) {
|
|
ECerror(EC_R_BAD_SIGNATURE);
|
|
ret = 0;
|
|
goto err;
|
|
}
|
|
if (BN_cmp(sig->s, BN_value_one()) < 0 || BN_cmp(sig->s, order) >= 0) {
|
|
ECerror(EC_R_BAD_SIGNATURE);
|
|
ret = 0;
|
|
goto err;
|
|
}
|
|
|
|
/* Step 3: convert the hash into an integer. */
|
|
if (!ecdsa_prepare_digest(digest, digest_len, key, e))
|
|
goto err;
|
|
|
|
/* Step 4: compute the inverse of s modulo order. */
|
|
if (BN_mod_inverse_ct(sinv, sig->s, order, ctx) == NULL) {
|
|
ECerror(ERR_R_BN_LIB);
|
|
goto err;
|
|
}
|
|
/* Step 5: compute u = s^-1 * e and v = s^-1 * r (modulo order). */
|
|
if (!BN_mod_mul(u, e, sinv, order, ctx)) {
|
|
ECerror(ERR_R_BN_LIB);
|
|
goto err;
|
|
}
|
|
if (!BN_mod_mul(v, sig->r, sinv, order, ctx)) {
|
|
ECerror(ERR_R_BN_LIB);
|
|
goto err;
|
|
}
|
|
|
|
/*
|
|
* Steps 6 and 7: compute R = G * u + pub_key * v = (x, y). Reject if
|
|
* it's the point at infinity - getting affine coordinates fails. Keep
|
|
* the x coordinate.
|
|
*/
|
|
if ((point = EC_POINT_new(group)) == NULL) {
|
|
ECerror(ERR_R_MALLOC_FAILURE);
|
|
goto err;
|
|
}
|
|
if (!EC_POINT_mul(group, point, u, pub_key, v, ctx)) {
|
|
ECerror(ERR_R_EC_LIB);
|
|
goto err;
|
|
}
|
|
if (!EC_POINT_get_affine_coordinates(group, point, x, NULL, ctx)) {
|
|
ECerror(ERR_R_EC_LIB);
|
|
goto err;
|
|
}
|
|
/* Step 8: convert x to a number in [0, order). */
|
|
if (!BN_nnmod(x, x, order, ctx)) {
|
|
ECerror(ERR_R_BN_LIB);
|
|
goto err;
|
|
}
|
|
|
|
/* Step 9: the signature is valid iff the x-coordinate is equal to r. */
|
|
ret = (BN_cmp(x, sig->r) == 0);
|
|
|
|
err:
|
|
BN_CTX_end(ctx);
|
|
BN_CTX_free(ctx);
|
|
EC_POINT_free(point);
|
|
|
|
return ret;
|
|
}
|
|
|
|
int
|
|
ECDSA_do_verify(const unsigned char *digest, int digest_len,
|
|
const ECDSA_SIG *sig, EC_KEY *key)
|
|
{
|
|
if (key->meth->verify_sig == NULL) {
|
|
ECerror(EC_R_NOT_IMPLEMENTED);
|
|
return 0;
|
|
}
|
|
return key->meth->verify_sig(digest, digest_len, sig, key);
|
|
}
|
|
LCRYPTO_ALIAS(ECDSA_do_verify);
|