264 lines
6.8 KiB
C
264 lines
6.8 KiB
C
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/* $OpenBSD: bn_recp.c,v 1.15 2017/01/29 17:49:22 beck Exp $ */
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/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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* All rights reserved.
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*
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* This package is an SSL implementation written
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* by Eric Young (eay@cryptsoft.com).
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* The implementation was written so as to conform with Netscapes SSL.
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*
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* This library is free for commercial and non-commercial use as long as
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* the following conditions are aheared to. The following conditions
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* apply to all code found in this distribution, be it the RC4, RSA,
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* lhash, DES, etc., code; not just the SSL code. The SSL documentation
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* included with this distribution is covered by the same copyright terms
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* except that the holder is Tim Hudson (tjh@cryptsoft.com).
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*
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* Copyright remains Eric Young's, and as such any Copyright notices in
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* the code are not to be removed.
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* If this package is used in a product, Eric Young should be given attribution
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* as the author of the parts of the library used.
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* This can be in the form of a textual message at program startup or
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* in documentation (online or textual) provided with the package.
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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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* 1. Redistributions of source code must retain the copyright
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* notice, this list of conditions and the following disclaimer.
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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 the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* "This product includes cryptographic software written by
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* Eric Young (eay@cryptsoft.com)"
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* The word 'cryptographic' can be left out if the rouines from the library
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* being used are not cryptographic related :-).
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* 4. If you include any Windows specific code (or a derivative thereof) from
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* the apps directory (application code) you must include an acknowledgement:
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* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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*
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* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* The licence and distribution terms for any publically available version or
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* derivative of this code cannot be changed. i.e. this code cannot simply be
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* copied and put under another distribution licence
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* [including the GNU Public Licence.]
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*/
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#include <stdio.h>
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#include <openssl/err.h>
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#include "bn_lcl.h"
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void
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BN_RECP_CTX_init(BN_RECP_CTX *recp)
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{
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BN_init(&(recp->N));
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BN_init(&(recp->Nr));
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recp->num_bits = 0;
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recp->flags = 0;
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}
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BN_RECP_CTX *
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BN_RECP_CTX_new(void)
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{
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BN_RECP_CTX *ret;
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if ((ret = malloc(sizeof(BN_RECP_CTX))) == NULL)
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return (NULL);
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BN_RECP_CTX_init(ret);
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ret->flags = BN_FLG_MALLOCED;
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return (ret);
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}
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void
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BN_RECP_CTX_free(BN_RECP_CTX *recp)
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{
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if (recp == NULL)
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return;
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BN_free(&(recp->N));
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BN_free(&(recp->Nr));
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if (recp->flags & BN_FLG_MALLOCED)
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free(recp);
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}
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int
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BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx)
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{
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if (!BN_copy(&(recp->N), d))
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return 0;
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BN_zero(&(recp->Nr));
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recp->num_bits = BN_num_bits(d);
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recp->shift = 0;
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return (1);
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}
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int
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BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y,
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BN_RECP_CTX *recp, BN_CTX *ctx)
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{
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int ret = 0;
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BIGNUM *a;
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const BIGNUM *ca;
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BN_CTX_start(ctx);
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if ((a = BN_CTX_get(ctx)) == NULL)
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goto err;
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if (y != NULL) {
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if (x == y) {
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if (!BN_sqr(a, x, ctx))
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goto err;
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} else {
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if (!BN_mul(a, x, y, ctx))
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goto err;
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}
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ca = a;
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} else
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ca = x; /* Just do the mod */
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ret = BN_div_recp(NULL, r, ca, recp, ctx);
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err:
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BN_CTX_end(ctx);
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bn_check_top(r);
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return (ret);
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}
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int
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BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, BN_RECP_CTX *recp,
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BN_CTX *ctx)
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{
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int i, j, ret = 0;
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BIGNUM *a, *b, *d, *r;
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BN_CTX_start(ctx);
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a = BN_CTX_get(ctx);
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b = BN_CTX_get(ctx);
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if (dv != NULL)
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d = dv;
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else
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d = BN_CTX_get(ctx);
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if (rem != NULL)
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r = rem;
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else
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r = BN_CTX_get(ctx);
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if (a == NULL || b == NULL || d == NULL || r == NULL)
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goto err;
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if (BN_ucmp(m, &(recp->N)) < 0) {
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BN_zero(d);
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if (!BN_copy(r, m)) {
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BN_CTX_end(ctx);
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return 0;
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}
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BN_CTX_end(ctx);
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return (1);
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}
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/* We want the remainder
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* Given input of ABCDEF / ab
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* we need multiply ABCDEF by 3 digests of the reciprocal of ab
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*
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*/
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/* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */
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i = BN_num_bits(m);
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j = recp->num_bits << 1;
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if (j > i)
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i = j;
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/* Nr := round(2^i / N) */
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if (i != recp->shift)
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recp->shift = BN_reciprocal(&(recp->Nr), &(recp->N), i, ctx);
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/* BN_reciprocal returns i, or -1 for an error */
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if (recp->shift == -1)
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goto err;
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/* d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))|
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* = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))|
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* <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)|
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* = |m/N|
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*/
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if (!BN_rshift(a, m, recp->num_bits))
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goto err;
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if (!BN_mul(b, a,&(recp->Nr), ctx))
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goto err;
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if (!BN_rshift(d, b, i - recp->num_bits))
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goto err;
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d->neg = 0;
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if (!BN_mul(b, &(recp->N), d, ctx))
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goto err;
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if (!BN_usub(r, m, b))
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goto err;
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r->neg = 0;
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#if 1
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j = 0;
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while (BN_ucmp(r, &(recp->N)) >= 0) {
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if (j++ > 2) {
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BNerror(BN_R_BAD_RECIPROCAL);
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goto err;
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}
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if (!BN_usub(r, r, &(recp->N)))
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goto err;
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if (!BN_add_word(d, 1))
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goto err;
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}
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#endif
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r->neg = BN_is_zero(r) ? 0 : m->neg;
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d->neg = m->neg^recp->N.neg;
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ret = 1;
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err:
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BN_CTX_end(ctx);
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bn_check_top(dv);
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bn_check_top(rem);
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return (ret);
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}
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/* len is the expected size of the result
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* We actually calculate with an extra word of precision, so
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* we can do faster division if the remainder is not required.
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*/
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/* r := 2^len / m */
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int
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BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx)
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{
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int ret = -1;
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BIGNUM *t;
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BN_CTX_start(ctx);
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if ((t = BN_CTX_get(ctx)) == NULL)
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goto err;
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if (!BN_set_bit(t, len))
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goto err;
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if (!BN_div_ct(r, NULL, t,m, ctx))
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goto err;
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ret = len;
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err:
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bn_check_top(r);
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BN_CTX_end(ctx);
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return (ret);
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}
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