1/* crypto/bn/bn_mod.c */
2/* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
3 * for the OpenSSL project. */
4/* ====================================================================
5 * Copyright (c) 1998-2000 The OpenSSL Project.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 *
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in
16 *    the documentation and/or other materials provided with the
17 *    distribution.
18 *
19 * 3. All advertising materials mentioning features or use of this
20 *    software must display the following acknowledgment:
21 *    "This product includes software developed by the OpenSSL Project
22 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
23 *
24 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
25 *    endorse or promote products derived from this software without
26 *    prior written permission. For written permission, please contact
27 *    openssl-core@openssl.org.
28 *
29 * 5. Products derived from this software may not be called "OpenSSL"
30 *    nor may "OpenSSL" appear in their names without prior written
31 *    permission of the OpenSSL Project.
32 *
33 * 6. Redistributions of any form whatsoever must retain the following
34 *    acknowledgment:
35 *    "This product includes software developed by the OpenSSL Project
36 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
37 *
38 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
39 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
40 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
41 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
42 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
43 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
44 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
45 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
46 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
47 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
48 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
49 * OF THE POSSIBILITY OF SUCH DAMAGE.
50 * ====================================================================
51 *
52 * This product includes cryptographic software written by Eric Young
53 * (eay@cryptsoft.com).  This product includes software written by Tim
54 * Hudson (tjh@cryptsoft.com).
55 *
56 */
57/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
58 * All rights reserved.
59 *
60 * This package is an SSL implementation written
61 * by Eric Young (eay@cryptsoft.com).
62 * The implementation was written so as to conform with Netscapes SSL.
63 *
64 * This library is free for commercial and non-commercial use as long as
65 * the following conditions are aheared to.  The following conditions
66 * apply to all code found in this distribution, be it the RC4, RSA,
67 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
68 * included with this distribution is covered by the same copyright terms
69 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
70 *
71 * Copyright remains Eric Young's, and as such any Copyright notices in
72 * the code are not to be removed.
73 * If this package is used in a product, Eric Young should be given attribution
74 * as the author of the parts of the library used.
75 * This can be in the form of a textual message at program startup or
76 * in documentation (online or textual) provided with the package.
77 *
78 * Redistribution and use in source and binary forms, with or without
79 * modification, are permitted provided that the following conditions
80 * are met:
81 * 1. Redistributions of source code must retain the copyright
82 *    notice, this list of conditions and the following disclaimer.
83 * 2. Redistributions in binary form must reproduce the above copyright
84 *    notice, this list of conditions and the following disclaimer in the
85 *    documentation and/or other materials provided with the distribution.
86 * 3. All advertising materials mentioning features or use of this software
87 *    must display the following acknowledgement:
88 *    "This product includes cryptographic software written by
89 *     Eric Young (eay@cryptsoft.com)"
90 *    The word 'cryptographic' can be left out if the rouines from the library
91 *    being used are not cryptographic related :-).
92 * 4. If you include any Windows specific code (or a derivative thereof) from
93 *    the apps directory (application code) you must include an acknowledgement:
94 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
95 *
96 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
97 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
98 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
99 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
100 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
101 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
102 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
103 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
104 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
105 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
106 * SUCH DAMAGE.
107 *
108 * The licence and distribution terms for any publically available version or
109 * derivative of this code cannot be changed.  i.e. this code cannot simply be
110 * copied and put under another distribution licence
111 * [including the GNU Public Licence.]
112 */
113
114#include "cryptlib.h"
115#include "bn_lcl.h"
116
117
118#if 0 /* now just a #define */
119int BN_mod(BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
120	{
121	return(BN_div(NULL,rem,m,d,ctx));
122	/* note that  rem->neg == m->neg  (unless the remainder is zero) */
123	}
124#endif
125
126
127int BN_nnmod(BIGNUM *r, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
128	{
129	/* like BN_mod, but returns non-negative remainder
130	 * (i.e.,  0 <= r < |d|  always holds) */
131
132	if (!(BN_mod(r,m,d,ctx)))
133		return 0;
134	if (!r->neg)
135		return 1;
136	/* now   -|d| < r < 0,  so we have to set  r := r + |d| */
137	return (d->neg ? BN_sub : BN_add)(r, r, d);
138}
139
140
141int BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, BN_CTX *ctx)
142	{
143	if (!BN_add(r, a, b)) return 0;
144	return BN_nnmod(r, r, m, ctx);
145	}
146
147
148/* BN_mod_add variant that may be used if both  a  and  b  are non-negative
149 * and less than  m */
150int BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
151	{
152	if (!BN_uadd(r, a, b)) return 0;
153	if (BN_ucmp(r, m) >= 0)
154		return BN_usub(r, r, m);
155	return 1;
156	}
157
158
159int BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, BN_CTX *ctx)
160	{
161	if (!BN_sub(r, a, b)) return 0;
162	return BN_nnmod(r, r, m, ctx);
163	}
164
165
166/* BN_mod_sub variant that may be used if both  a  and  b  are non-negative
167 * and less than  m */
168int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
169	{
170	if (!BN_sub(r, a, b)) return 0;
171	if (r->neg)
172		return BN_add(r, r, m);
173	return 1;
174	}
175
176
177/* slow but works */
178int BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
179	BN_CTX *ctx)
180	{
181	BIGNUM *t;
182	int ret=0;
183
184	bn_check_top(a);
185	bn_check_top(b);
186	bn_check_top(m);
187
188	BN_CTX_start(ctx);
189	if ((t = BN_CTX_get(ctx)) == NULL) goto err;
190	if (a == b)
191		{ if (!BN_sqr(t,a,ctx)) goto err; }
192	else
193		{ if (!BN_mul(t,a,b,ctx)) goto err; }
194	if (!BN_nnmod(r,t,m,ctx)) goto err;
195	bn_check_top(r);
196	ret=1;
197err:
198	BN_CTX_end(ctx);
199	return(ret);
200	}
201
202
203int BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
204	{
205	if (!BN_sqr(r, a, ctx)) return 0;
206	/* r->neg == 0,  thus we don't need BN_nnmod */
207	return BN_mod(r, r, m, ctx);
208	}
209
210
211int BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
212	{
213	if (!BN_lshift1(r, a)) return 0;
214	bn_check_top(r);
215	return BN_nnmod(r, r, m, ctx);
216	}
217
218
219/* BN_mod_lshift1 variant that may be used if  a  is non-negative
220 * and less than  m */
221int BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m)
222	{
223	if (!BN_lshift1(r, a)) return 0;
224	bn_check_top(r);
225	if (BN_cmp(r, m) >= 0)
226		return BN_sub(r, r, m);
227	return 1;
228	}
229
230
231int BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx)
232	{
233	BIGNUM *abs_m = NULL;
234	int ret;
235
236	if (!BN_nnmod(r, a, m, ctx)) return 0;
237
238	if (m->neg)
239		{
240		abs_m = BN_dup(m);
241		if (abs_m == NULL) return 0;
242		abs_m->neg = 0;
243		}
244
245	ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m));
246	bn_check_top(r);
247
248	if (abs_m)
249		BN_free(abs_m);
250	return ret;
251	}
252
253
254/* BN_mod_lshift variant that may be used if  a  is non-negative
255 * and less than  m */
256int BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m)
257	{
258	if (r != a)
259		{
260		if (BN_copy(r, a) == NULL) return 0;
261		}
262
263	while (n > 0)
264		{
265		int max_shift;
266
267		/* 0 < r < m */
268		max_shift = BN_num_bits(m) - BN_num_bits(r);
269		/* max_shift >= 0 */
270
271		if (max_shift < 0)
272			{
273			BNerr(BN_F_BN_MOD_LSHIFT_QUICK, BN_R_INPUT_NOT_REDUCED);
274			return 0;
275			}
276
277		if (max_shift > n)
278			max_shift = n;
279
280		if (max_shift)
281			{
282			if (!BN_lshift(r, r, max_shift)) return 0;
283			n -= max_shift;
284			}
285		else
286			{
287			if (!BN_lshift1(r, r)) return 0;
288			--n;
289			}
290
291		/* BN_num_bits(r) <= BN_num_bits(m) */
292
293		if (BN_cmp(r, m) >= 0)
294			{
295			if (!BN_sub(r, r, m)) return 0;
296			}
297		}
298	bn_check_top(r);
299
300	return 1;
301	}
302