1 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young (eay@cryptsoft.com).
6 * The implementation was written so as to conform with Netscapes SSL.
7 *
8 * This library is free for commercial and non-commercial use as long as
9 * the following conditions are aheared to. The following conditions
10 * apply to all code found in this distribution, be it the RC4, RSA,
11 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
12 * included with this distribution is covered by the same copyright terms
13 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
14 *
15 * Copyright remains Eric Young's, and as such any Copyright notices in
16 * the code are not to be removed.
17 * If this package is used in a product, Eric Young should be given attribution
18 * as the author of the parts of the library used.
19 * This can be in the form of a textual message at program startup or
20 * in documentation (online or textual) provided with the package.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions
24 * are met:
25 * 1. Redistributions of source code must retain the copyright
26 * notice, this list of conditions and the following disclaimer.
27 * 2. Redistributions in binary form must reproduce the above copyright
28 * notice, this list of conditions and the following disclaimer in the
29 * documentation and/or other materials provided with the distribution.
30 * 3. All advertising materials mentioning features or use of this software
31 * must display the following acknowledgement:
32 * "This product includes cryptographic software written by
33 * Eric Young (eay@cryptsoft.com)"
34 * The word 'cryptographic' can be left out if the rouines from the library
35 * being used are not cryptographic related :-).
36 * 4. If you include any Windows specific code (or a derivative thereof) from
37 * the apps directory (application code) you must include an acknowledgement:
38 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
39 *
40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
51 *
52 * The licence and distribution terms for any publically available version or
53 * derivative of this code cannot be changed. i.e. this code cannot simply be
54 * copied and put under another distribution licence
55 * [including the GNU Public Licence.] */
56
57 #include <openssl/bn.h>
58
59 #include <string.h>
60
61 #include <openssl/err.h>
62 #include <openssl/mem.h>
63
64 #include "internal.h"
65
66
BN_add(BIGNUM * r,const BIGNUM * a,const BIGNUM * b)67 int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
68 const BIGNUM *tmp;
69 int a_neg = a->neg, ret;
70
71 /* a + b a+b
72 * a + -b a-b
73 * -a + b b-a
74 * -a + -b -(a+b)
75 */
76 if (a_neg ^ b->neg) {
77 /* only one is negative */
78 if (a_neg) {
79 tmp = a;
80 a = b;
81 b = tmp;
82 }
83
84 /* we are now a - b */
85 if (BN_ucmp(a, b) < 0) {
86 if (!BN_usub(r, b, a)) {
87 return 0;
88 }
89 r->neg = 1;
90 } else {
91 if (!BN_usub(r, a, b)) {
92 return 0;
93 }
94 r->neg = 0;
95 }
96 return 1;
97 }
98
99 ret = BN_uadd(r, a, b);
100 r->neg = a_neg;
101 return ret;
102 }
103
BN_uadd(BIGNUM * r,const BIGNUM * a,const BIGNUM * b)104 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
105 int max, min, dif;
106 BN_ULONG *ap, *bp, *rp, carry, t1, t2;
107 const BIGNUM *tmp;
108
109 if (a->top < b->top) {
110 tmp = a;
111 a = b;
112 b = tmp;
113 }
114 max = a->top;
115 min = b->top;
116 dif = max - min;
117
118 if (!bn_wexpand(r, max + 1)) {
119 return 0;
120 }
121
122 r->top = max;
123
124 ap = a->d;
125 bp = b->d;
126 rp = r->d;
127
128 carry = bn_add_words(rp, ap, bp, min);
129 rp += min;
130 ap += min;
131 bp += min;
132
133 if (carry) {
134 while (dif) {
135 dif--;
136 t1 = *(ap++);
137 t2 = (t1 + 1) & BN_MASK2;
138 *(rp++) = t2;
139 if (t2) {
140 carry = 0;
141 break;
142 }
143 }
144 if (carry) {
145 /* carry != 0 => dif == 0 */
146 *rp = 1;
147 r->top++;
148 }
149 }
150
151 if (dif && rp != ap) {
152 while (dif--) {
153 /* copy remaining words if ap != rp */
154 *(rp++) = *(ap++);
155 }
156 }
157
158 r->neg = 0;
159 return 1;
160 }
161
BN_add_word(BIGNUM * a,BN_ULONG w)162 int BN_add_word(BIGNUM *a, BN_ULONG w) {
163 BN_ULONG l;
164 int i;
165
166 w &= BN_MASK2;
167
168 /* degenerate case: w is zero */
169 if (!w) {
170 return 1;
171 }
172
173 /* degenerate case: a is zero */
174 if (BN_is_zero(a)) {
175 return BN_set_word(a, w);
176 }
177
178 /* handle 'a' when negative */
179 if (a->neg) {
180 a->neg = 0;
181 i = BN_sub_word(a, w);
182 if (!BN_is_zero(a)) {
183 a->neg = !(a->neg);
184 }
185 return i;
186 }
187
188 for (i = 0; w != 0 && i < a->top; i++) {
189 a->d[i] = l = (a->d[i] + w) & BN_MASK2;
190 w = (w > l) ? 1 : 0;
191 }
192
193 if (w && i == a->top) {
194 if (!bn_wexpand(a, a->top + 1)) {
195 return 0;
196 }
197 a->top++;
198 a->d[i] = w;
199 }
200
201 return 1;
202 }
203
BN_sub(BIGNUM * r,const BIGNUM * a,const BIGNUM * b)204 int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
205 int max;
206 int add = 0, neg = 0;
207 const BIGNUM *tmp;
208
209 /* a - b a-b
210 * a - -b a+b
211 * -a - b -(a+b)
212 * -a - -b b-a
213 */
214 if (a->neg) {
215 if (b->neg) {
216 tmp = a;
217 a = b;
218 b = tmp;
219 } else {
220 add = 1;
221 neg = 1;
222 }
223 } else {
224 if (b->neg) {
225 add = 1;
226 neg = 0;
227 }
228 }
229
230 if (add) {
231 if (!BN_uadd(r, a, b)) {
232 return 0;
233 }
234
235 r->neg = neg;
236 return 1;
237 }
238
239 /* We are actually doing a - b :-) */
240
241 max = (a->top > b->top) ? a->top : b->top;
242 if (!bn_wexpand(r, max)) {
243 return 0;
244 }
245
246 if (BN_ucmp(a, b) < 0) {
247 if (!BN_usub(r, b, a)) {
248 return 0;
249 }
250 r->neg = 1;
251 } else {
252 if (!BN_usub(r, a, b)) {
253 return 0;
254 }
255 r->neg = 0;
256 }
257
258 return 1;
259 }
260
BN_usub(BIGNUM * r,const BIGNUM * a,const BIGNUM * b)261 int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
262 int max, min, dif;
263 register BN_ULONG t1, t2, *ap, *bp, *rp;
264 int i, carry;
265
266 max = a->top;
267 min = b->top;
268 dif = max - min;
269
270 if (dif < 0) /* hmm... should not be happening */
271 {
272 OPENSSL_PUT_ERROR(BN, BN_R_ARG2_LT_ARG3);
273 return 0;
274 }
275
276 if (!bn_wexpand(r, max)) {
277 return 0;
278 }
279
280 ap = a->d;
281 bp = b->d;
282 rp = r->d;
283
284 carry = 0;
285 for (i = min; i != 0; i--) {
286 t1 = *(ap++);
287 t2 = *(bp++);
288 if (carry) {
289 carry = (t1 <= t2);
290 t1 = (t1 - t2 - 1) & BN_MASK2;
291 } else {
292 carry = (t1 < t2);
293 t1 = (t1 - t2) & BN_MASK2;
294 }
295 *(rp++) = t1 & BN_MASK2;
296 }
297
298 if (carry) /* subtracted */
299 {
300 if (!dif) {
301 /* error: a < b */
302 return 0;
303 }
304
305 while (dif) {
306 dif--;
307 t1 = *(ap++);
308 t2 = (t1 - 1) & BN_MASK2;
309 *(rp++) = t2;
310 if (t1) {
311 break;
312 }
313 }
314 }
315
316 if (dif > 0 && rp != ap) {
317 OPENSSL_memcpy(rp, ap, sizeof(*rp) * dif);
318 }
319
320 r->top = max;
321 r->neg = 0;
322 bn_correct_top(r);
323
324 return 1;
325 }
326
BN_sub_word(BIGNUM * a,BN_ULONG w)327 int BN_sub_word(BIGNUM *a, BN_ULONG w) {
328 int i;
329
330 w &= BN_MASK2;
331
332 /* degenerate case: w is zero */
333 if (!w) {
334 return 1;
335 }
336
337 /* degenerate case: a is zero */
338 if (BN_is_zero(a)) {
339 i = BN_set_word(a, w);
340 if (i != 0) {
341 BN_set_negative(a, 1);
342 }
343 return i;
344 }
345
346 /* handle 'a' when negative */
347 if (a->neg) {
348 a->neg = 0;
349 i = BN_add_word(a, w);
350 a->neg = 1;
351 return i;
352 }
353
354 if ((a->top == 1) && (a->d[0] < w)) {
355 a->d[0] = w - a->d[0];
356 a->neg = 1;
357 return 1;
358 }
359
360 i = 0;
361 for (;;) {
362 if (a->d[i] >= w) {
363 a->d[i] -= w;
364 break;
365 } else {
366 a->d[i] = (a->d[i] - w) & BN_MASK2;
367 i++;
368 w = 1;
369 }
370 }
371
372 if ((a->d[i] == 0) && (i == (a->top - 1))) {
373 a->top--;
374 }
375
376 return 1;
377 }
378