GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libcrypto/bn/bn_recp.c Lines: 71 82 86.6 %
Date: 2017-11-07 Branches: 36 60 60.0 %

Line Branch Exec Source
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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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59
#include <stdio.h>
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61
#include <openssl/err.h>
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63
#include "bn_lcl.h"
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65
void
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BN_RECP_CTX_init(BN_RECP_CTX *recp)
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{
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3648
	BN_init(&(recp->N));
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1824
	BN_init(&(recp->Nr));
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1824
	recp->num_bits = 0;
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1824
	recp->flags = 0;
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1824
}
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74
BN_RECP_CTX *
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BN_RECP_CTX_new(void)
76
{
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	BN_RECP_CTX *ret;
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79
	if ((ret = malloc(sizeof(BN_RECP_CTX))) == NULL)
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		return (NULL);
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82
	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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87
void
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BN_RECP_CTX_free(BN_RECP_CTX *recp)
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{
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3648
	if (recp == NULL)
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		return;
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1824
	BN_free(&(recp->N));
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1824
	BN_free(&(recp->Nr));
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1824
	if (recp->flags & BN_FLG_MALLOCED)
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		free(recp);
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1824
}
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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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5436
	if (!BN_copy(&(recp->N), d))
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		return 0;
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2718
	BN_zero(&(recp->Nr));
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2718
	recp->num_bits = BN_num_bits(d);
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2718
	recp->shift = 0;
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2718
	return (1);
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2718
}
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110
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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1677820
	BN_CTX_start(ctx);
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838910
	if ((a = BN_CTX_get(ctx)) == NULL)
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		goto err;
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838910
	if (y != NULL) {
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838910
		if (x == y) {
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695160
			if (!BN_sqr(a, x, ctx))
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				goto err;
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		} else {
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143750
			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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838910
	} else
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		ca = x; /* Just do the mod */
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133
838910
	ret = BN_div_recp(NULL, r, ca, recp, ctx);
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135
err:
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838910
	BN_CTX_end(ctx);
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	bn_check_top(r);
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838910
	return (ret);
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}
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141
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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148
1679620
	BN_CTX_start(ctx);
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839810
	a = BN_CTX_get(ctx);
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839810
	b = BN_CTX_get(ctx);
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839810
	if (dv != NULL)
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900
		d = dv;
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	else
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838910
		d = BN_CTX_get(ctx);
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839810
	if (rem != NULL)
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839810
		r = rem;
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	else
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		r = BN_CTX_get(ctx);
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839810
	if (a == NULL || b == NULL || d == NULL || r == NULL)
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		goto err;
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162
839810
	if (BN_ucmp(m, &(recp->N)) < 0) {
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1921
		BN_zero(d);
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3842
		if (!BN_copy(r, m)) {
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			BN_CTX_end(ctx);
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			return 0;
167
		}
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1921
		BN_CTX_end(ctx);
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1921
		return (1);
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	}
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172
	/* 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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178
	/* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */
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837889
	i = BN_num_bits(m);
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837889
	j = recp->num_bits << 1;
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837889
	if (j > i)
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757564
		i = j;
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184
	/* Nr := round(2^i / N) */
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837889
	if (i != recp->shift)
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2700
		recp->shift = BN_reciprocal(&(recp->Nr), &(recp->N), i, ctx);
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188
	/* BN_reciprocal returns i, or -1 for an error */
189
837889
	if (recp->shift == -1)
190
		goto err;
191
192
	/* 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|
196
	 */
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837889
	if (!BN_rshift(a, m, recp->num_bits))
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		goto err;
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837889
	if (!BN_mul(b, a,&(recp->Nr), ctx))
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		goto err;
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837889
	if (!BN_rshift(d, b, i - recp->num_bits))
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		goto err;
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837889
	d->neg = 0;
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205
837889
	if (!BN_mul(b, &(recp->N), d, ctx))
206
		goto err;
207
837889
	if (!BN_usub(r, m, b))
208
		goto err;
209
837889
	r->neg = 0;
210
211
#if 1
212
	j = 0;
213
2305894
	while (BN_ucmp(r, &(recp->N)) >= 0) {
214
630116
		if (j++ > 2) {
215
			BNerror(BN_R_BAD_RECIPROCAL);
216
			goto err;
217
		}
218
630116
		if (!BN_usub(r, r, &(recp->N)))
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			goto err;
220
630116
		if (!BN_add_word(d, 1))
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			goto err;
222
	}
223
#endif
224
225
2513661
	r->neg = BN_is_zero(r) ? 0 : m->neg;
226
837889
	d->neg = m->neg^recp->N.neg;
227
837889
	ret = 1;
228
229
err:
230
837889
	BN_CTX_end(ctx);
231
	bn_check_top(dv);
232
	bn_check_top(rem);
233
837889
	return (ret);
234
839810
}
235
236
/* len is the expected size of the result
237
 * We actually calculate with an extra word of precision, so
238
 * we can do faster division if the remainder is not required.
239
 */
240
/* r := 2^len / m */
241
int
242
BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx)
243
{
244
	int ret = -1;
245
	BIGNUM *t;
246
247
5400
	BN_CTX_start(ctx);
248
2700
	if ((t = BN_CTX_get(ctx)) == NULL)
249
		goto err;
250
251
2700
	if (!BN_set_bit(t, len))
252
		goto err;
253
254
2700
	if (!BN_div_ct(r, NULL, t,m, ctx))
255
		goto err;
256
257
2700
	ret = len;
258
259
err:
260
	bn_check_top(r);
261
2700
	BN_CTX_end(ctx);
262
2700
	return (ret);
263
}