1 /* $OpenBSD: bn_word.c,v 1.21 2023/07/08 12:21:58 beck Exp $ */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59 #include <stdio.h>
60
61 #include "bn_local.h"
62
63 BN_ULONG
BN_mod_word(const BIGNUM * a,BN_ULONG w)64 BN_mod_word(const BIGNUM *a, BN_ULONG w)
65 {
66 #ifndef BN_LLONG
67 BN_ULONG ret = 0;
68 #else
69 BN_ULLONG ret = 0;
70 #endif
71 int i;
72
73 if (w == 0)
74 return (BN_ULONG) - 1;
75
76 #ifndef BN_ULLONG
77 /* If |w| is too long and we don't have |BN_ULLONG| then we need to fall back
78 * to using |BN_div_word|. */
79 if (w > ((BN_ULONG)1 << BN_BITS4)) {
80 BIGNUM *tmp = BN_dup(a);
81 if (tmp == NULL) {
82 return (BN_ULONG)-1;
83 }
84 ret = BN_div_word(tmp, w);
85 BN_free(tmp);
86 return ret;
87 }
88 #endif
89
90 w &= BN_MASK2;
91 for (i = a->top - 1; i >= 0; i--) {
92 #ifndef BN_LLONG
93 ret = ((ret << BN_BITS4) | ((a->d[i] >> BN_BITS4) &
94 BN_MASK2l)) % w;
95 ret = ((ret << BN_BITS4) | (a->d[i] & BN_MASK2l)) % w;
96 #else
97 ret = (BN_ULLONG)(((ret << (BN_ULLONG)BN_BITS2) |
98 a->d[i]) % (BN_ULLONG)w);
99 #endif
100 }
101 return ((BN_ULONG)ret);
102 }
103 LCRYPTO_ALIAS(BN_mod_word);
104
105 BN_ULONG
BN_div_word(BIGNUM * a,BN_ULONG w)106 BN_div_word(BIGNUM *a, BN_ULONG w)
107 {
108 BN_ULONG ret = 0;
109 int i, j;
110
111 w &= BN_MASK2;
112
113 if (!w)
114 /* actually this an error (division by zero) */
115 return (BN_ULONG) - 1;
116 if (a->top == 0)
117 return 0;
118
119 /* normalize input (so bn_div_words doesn't complain) */
120 j = BN_BITS2 - BN_num_bits_word(w);
121 w <<= j;
122 if (!BN_lshift(a, a, j))
123 return (BN_ULONG) - 1;
124
125 for (i = a->top - 1; i >= 0; i--) {
126 BN_ULONG l, d;
127
128 l = a->d[i];
129 bn_div_rem_words(ret, l, w, &d, &ret);
130 a->d[i] = d;
131 }
132 if ((a->top > 0) && (a->d[a->top - 1] == 0))
133 a->top--;
134 ret >>= j;
135
136 /* Set negative again, to handle -0 case. */
137 BN_set_negative(a, a->neg);
138
139 return (ret);
140 }
141 LCRYPTO_ALIAS(BN_div_word);
142
143 int
BN_add_word(BIGNUM * a,BN_ULONG w)144 BN_add_word(BIGNUM *a, BN_ULONG w)
145 {
146 BN_ULONG l;
147 int i;
148
149 w &= BN_MASK2;
150
151 /* degenerate case: w is zero */
152 if (!w)
153 return 1;
154 /* degenerate case: a is zero */
155 if (BN_is_zero(a))
156 return BN_set_word(a, w);
157 /* handle 'a' when negative */
158 if (a->neg) {
159 a->neg = 0;
160 i = BN_sub_word(a, w);
161 BN_set_negative(a, !a->neg);
162 return (i);
163 }
164 for (i = 0; w != 0 && i < a->top; i++) {
165 a->d[i] = l = (a->d[i] + w) & BN_MASK2;
166 w = (w > l) ? 1 : 0;
167 }
168 if (w && i == a->top) {
169 if (!bn_wexpand(a, a->top + 1))
170 return 0;
171 a->top++;
172 a->d[i] = w;
173 }
174 return (1);
175 }
176 LCRYPTO_ALIAS(BN_add_word);
177
178 int
BN_sub_word(BIGNUM * a,BN_ULONG w)179 BN_sub_word(BIGNUM *a, BN_ULONG w)
180 {
181 int i;
182
183 w &= BN_MASK2;
184
185 /* degenerate case: w is zero */
186 if (!w)
187 return 1;
188 /* degenerate case: a is zero */
189 if (BN_is_zero(a)) {
190 i = BN_set_word(a, w);
191 if (i != 0)
192 BN_set_negative(a, 1);
193 return i;
194 }
195 /* handle 'a' when negative */
196 if (a->neg) {
197 a->neg = 0;
198 i = BN_add_word(a, w);
199 BN_set_negative(a, !a->neg);
200 return (i);
201 }
202
203 if ((a->top == 1) && (a->d[0] < w)) {
204 a->d[0] = w - a->d[0];
205 BN_set_negative(a, 1);
206 return (1);
207 }
208 i = 0;
209 for (;;) {
210 if (a->d[i] >= w) {
211 a->d[i] -= w;
212 break;
213 } else {
214 a->d[i] = (a->d[i] - w) & BN_MASK2;
215 i++;
216 w = 1;
217 }
218 }
219 if ((a->d[i] == 0) && (i == (a->top - 1)))
220 a->top--;
221 return (1);
222 }
223 LCRYPTO_ALIAS(BN_sub_word);
224
225 int
BN_mul_word(BIGNUM * a,BN_ULONG w)226 BN_mul_word(BIGNUM *a, BN_ULONG w)
227 {
228 BN_ULONG ll;
229
230 w &= BN_MASK2;
231 if (a->top) {
232 if (w == 0)
233 BN_zero(a);
234 else {
235 ll = bn_mul_words(a->d, a->d, a->top, w);
236 if (ll) {
237 if (!bn_wexpand(a, a->top + 1))
238 return (0);
239 a->d[a->top++] = ll;
240 }
241 }
242 }
243 return (1);
244 }
245 LCRYPTO_ALIAS(BN_mul_word);
246