1 /* $OpenBSD: bn_shift.c,v 1.14 2022/06/22 09:03:06 tb 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 #include <string.h>
61
62 #include <openssl/err.h>
63
64 #include "bn_lcl.h"
65
66 int
BN_lshift1(BIGNUM * r,const BIGNUM * a)67 BN_lshift1(BIGNUM *r, const BIGNUM *a)
68 {
69 BN_ULONG *ap, *rp, t, c;
70 int i;
71
72 bn_check_top(r);
73 bn_check_top(a);
74
75 if (r != a) {
76 r->neg = a->neg;
77 if (bn_wexpand(r, a->top + 1) == NULL)
78 return (0);
79 r->top = a->top;
80 } else {
81 if (bn_wexpand(r, a->top + 1) == NULL)
82 return (0);
83 }
84 ap = a->d;
85 rp = r->d;
86 c = 0;
87 for (i = 0; i < a->top; i++) {
88 t= *(ap++);
89 *(rp++) = ((t << 1) | c) & BN_MASK2;
90 c = (t & BN_TBIT) ? 1 : 0;
91 }
92 if (c) {
93 *rp = 1;
94 r->top++;
95 }
96 bn_check_top(r);
97 return (1);
98 }
99
100 int
BN_rshift1(BIGNUM * r,const BIGNUM * a)101 BN_rshift1(BIGNUM *r, const BIGNUM *a)
102 {
103 BN_ULONG *ap, *rp, t, c;
104 int i, j;
105
106 bn_check_top(r);
107 bn_check_top(a);
108
109 if (BN_is_zero(a)) {
110 BN_zero(r);
111 return (1);
112 }
113 i = a->top;
114 ap = a->d;
115 j = i - (ap[i - 1]==1);
116 if (a != r) {
117 if (bn_wexpand(r, j) == NULL)
118 return (0);
119 r->neg = a->neg;
120 }
121 rp = r->d;
122 t = ap[--i];
123 c = (t & 1) ? BN_TBIT : 0;
124 if (t >>= 1)
125 rp[i] = t;
126 while (i > 0) {
127 t = ap[--i];
128 rp[i] = ((t >> 1) & BN_MASK2) | c;
129 c = (t & 1) ? BN_TBIT : 0;
130 }
131 r->top = j;
132 bn_check_top(r);
133 return (1);
134 }
135
136 int
BN_lshift(BIGNUM * r,const BIGNUM * a,int n)137 BN_lshift(BIGNUM *r, const BIGNUM *a, int n)
138 {
139 int i, nw, lb, rb;
140 BN_ULONG *t, *f;
141 BN_ULONG l;
142
143 if (n < 0) {
144 BNerror(BN_R_INVALID_LENGTH);
145 return 0;
146 }
147
148 bn_check_top(r);
149 bn_check_top(a);
150
151 r->neg = a->neg;
152 nw = n / BN_BITS2;
153 if (bn_wexpand(r, a->top + nw + 1) == NULL)
154 return (0);
155 lb = n % BN_BITS2;
156 rb = BN_BITS2 - lb;
157 f = a->d;
158 t = r->d;
159 t[a->top + nw] = 0;
160 if (lb == 0)
161 for (i = a->top - 1; i >= 0; i--)
162 t[nw + i] = f[i];
163 else
164 for (i = a->top - 1; i >= 0; i--) {
165 l = f[i];
166 t[nw + i + 1] |= (l >> rb) & BN_MASK2;
167 t[nw + i] = (l << lb) & BN_MASK2;
168 }
169 memset(t, 0, nw * sizeof(t[0]));
170 /* for (i=0; i<nw; i++)
171 t[i]=0;*/
172 r->top = a->top + nw + 1;
173 bn_correct_top(r);
174 bn_check_top(r);
175 return (1);
176 }
177
178 int
BN_rshift(BIGNUM * r,const BIGNUM * a,int n)179 BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
180 {
181 int i, j, nw, lb, rb;
182 BN_ULONG *t, *f;
183 BN_ULONG l, tmp;
184
185 if (n < 0) {
186 BNerror(BN_R_INVALID_LENGTH);
187 return 0;
188 }
189
190 bn_check_top(r);
191 bn_check_top(a);
192
193 nw = n / BN_BITS2;
194 rb = n % BN_BITS2;
195 lb = BN_BITS2 - rb;
196 if (nw >= a->top || a->top == 0) {
197 BN_zero(r);
198 return (1);
199 }
200 i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2;
201 if (r != a) {
202 r->neg = a->neg;
203 if (bn_wexpand(r, i) == NULL)
204 return (0);
205 } else {
206 if (n == 0)
207 return 1; /* or the copying loop will go berserk */
208 }
209
210 f = &(a->d[nw]);
211 t = r->d;
212 j = a->top - nw;
213 r->top = i;
214
215 if (rb == 0) {
216 for (i = j; i != 0; i--)
217 *(t++) = *(f++);
218 } else {
219 l = *(f++);
220 for (i = j - 1; i != 0; i--) {
221 tmp = (l >> rb) & BN_MASK2;
222 l = *(f++);
223 *(t++) = (tmp|(l << lb)) & BN_MASK2;
224 }
225 if ((l = (l >> rb) & BN_MASK2))
226 *(t) = l;
227 }
228 bn_check_top(r);
229 return (1);
230 }
231