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 <openssl/err.h>
60 #include <openssl/mem.h>
61
62 #include "internal.h"
63
64
BN_add(BIGNUM * r,const BIGNUM * a,const BIGNUM * b)65 int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
66 const BIGNUM *tmp;
67 int a_neg = a->neg, ret;
68
69 /* a + b a+b
70 * a + -b a-b
71 * -a + b b-a
72 * -a + -b -(a+b)
73 */
74 if (a_neg ^ b->neg) {
75 /* only one is negative */
76 if (a_neg) {
77 tmp = a;
78 a = b;
79 b = tmp;
80 }
81
82 /* we are now a - b */
83 if (BN_ucmp(a, b) < 0) {
84 if (!BN_usub(r, b, a)) {
85 return 0;
86 }
87 r->neg = 1;
88 } else {
89 if (!BN_usub(r, a, b)) {
90 return 0;
91 }
92 r->neg = 0;
93 }
94 return 1;
95 }
96
97 ret = BN_uadd(r, a, b);
98 r->neg = a_neg;
99 return ret;
100 }
101
BN_uadd(BIGNUM * r,const BIGNUM * a,const BIGNUM * b)102 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
103 int max, min, dif;
104 BN_ULONG *ap, *bp, *rp, carry, t1, t2;
105 const BIGNUM *tmp;
106
107 if (a->top < b->top) {
108 tmp = a;
109 a = b;
110 b = tmp;
111 }
112 max = a->top;
113 min = b->top;
114 dif = max - min;
115
116 if (bn_wexpand(r, max + 1) == NULL) {
117 return 0;
118 }
119
120 r->top = max;
121
122 ap = a->d;
123 bp = b->d;
124 rp = r->d;
125
126 carry = bn_add_words(rp, ap, bp, min);
127 rp += min;
128 ap += min;
129 bp += min;
130
131 if (carry) {
132 while (dif) {
133 dif--;
134 t1 = *(ap++);
135 t2 = (t1 + 1) & BN_MASK2;
136 *(rp++) = t2;
137 if (t2) {
138 carry = 0;
139 break;
140 }
141 }
142 if (carry) {
143 /* carry != 0 => dif == 0 */
144 *rp = 1;
145 r->top++;
146 }
147 }
148
149 if (dif && rp != ap) {
150 while (dif--) {
151 /* copy remaining words if ap != rp */
152 *(rp++) = *(ap++);
153 }
154 }
155
156 r->neg = 0;
157 return 1;
158 }
159
BN_add_word(BIGNUM * a,BN_ULONG w)160 int BN_add_word(BIGNUM *a, BN_ULONG w) {
161 BN_ULONG l;
162 int i;
163
164 w &= BN_MASK2;
165
166 /* degenerate case: w is zero */
167 if (!w) {
168 return 1;
169 }
170
171 /* degenerate case: a is zero */
172 if (BN_is_zero(a)) {
173 return BN_set_word(a, w);
174 }
175
176 /* handle 'a' when negative */
177 if (a->neg) {
178 a->neg = 0;
179 i = BN_sub_word(a, w);
180 if (!BN_is_zero(a)) {
181 a->neg = !(a->neg);
182 }
183 return i;
184 }
185
186 for (i = 0; w != 0 && i < a->top; i++) {
187 a->d[i] = l = (a->d[i] + w) & BN_MASK2;
188 w = (w > l) ? 1 : 0;
189 }
190
191 if (w && i == a->top) {
192 if (bn_wexpand(a, a->top + 1) == NULL) {
193 return 0;
194 }
195 a->top++;
196 a->d[i] = w;
197 }
198
199 return 1;
200 }
201
BN_sub(BIGNUM * r,const BIGNUM * a,const BIGNUM * b)202 int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
203 int max;
204 int add = 0, neg = 0;
205 const BIGNUM *tmp;
206
207 /* a - b a-b
208 * a - -b a+b
209 * -a - b -(a+b)
210 * -a - -b b-a
211 */
212 if (a->neg) {
213 if (b->neg) {
214 tmp = a;
215 a = b;
216 b = tmp;
217 } else {
218 add = 1;
219 neg = 1;
220 }
221 } else {
222 if (b->neg) {
223 add = 1;
224 neg = 0;
225 }
226 }
227
228 if (add) {
229 if (!BN_uadd(r, a, b)) {
230 return 0;
231 }
232
233 r->neg = neg;
234 return 1;
235 }
236
237 /* We are actually doing a - b :-) */
238
239 max = (a->top > b->top) ? a->top : b->top;
240 if (bn_wexpand(r, max) == NULL) {
241 return 0;
242 }
243
244 if (BN_ucmp(a, b) < 0) {
245 if (!BN_usub(r, b, a)) {
246 return 0;
247 }
248 r->neg = 1;
249 } else {
250 if (!BN_usub(r, a, b)) {
251 return 0;
252 }
253 r->neg = 0;
254 }
255
256 return 1;
257 }
258
BN_usub(BIGNUM * r,const BIGNUM * a,const BIGNUM * b)259 int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
260 int max, min, dif;
261 register BN_ULONG t1, t2, *ap, *bp, *rp;
262 int i, carry;
263
264 max = a->top;
265 min = b->top;
266 dif = max - min;
267
268 if (dif < 0) /* hmm... should not be happening */
269 {
270 OPENSSL_PUT_ERROR(BN, BN_usub, BN_R_ARG2_LT_ARG3);
271 return 0;
272 }
273
274 if (bn_wexpand(r, max) == NULL) {
275 return 0;
276 }
277
278 ap = a->d;
279 bp = b->d;
280 rp = r->d;
281
282 carry = 0;
283 for (i = min; i != 0; i--) {
284 t1 = *(ap++);
285 t2 = *(bp++);
286 if (carry) {
287 carry = (t1 <= t2);
288 t1 = (t1 - t2 - 1) & BN_MASK2;
289 } else {
290 carry = (t1 < t2);
291 t1 = (t1 - t2) & BN_MASK2;
292 }
293 *(rp++) = t1 & BN_MASK2;
294 }
295
296 if (carry) /* subtracted */
297 {
298 if (!dif) {
299 /* error: a < b */
300 return 0;
301 }
302
303 while (dif) {
304 dif--;
305 t1 = *(ap++);
306 t2 = (t1 - 1) & BN_MASK2;
307 *(rp++) = t2;
308 if (t1) {
309 break;
310 }
311 }
312 }
313
314 if (rp != ap) {
315 for (;;) {
316 if (!dif--) {
317 break;
318 }
319 rp[0] = ap[0];
320 if (!dif--) {
321 break;
322 }
323 rp[1] = ap[1];
324 if (!dif--) {
325 break;
326 }
327 rp[2] = ap[2];
328 if (!dif--) {
329 break;
330 }
331 rp[3] = ap[3];
332 rp += 4;
333 ap += 4;
334 }
335 }
336
337 r->top = max;
338 r->neg = 0;
339 bn_correct_top(r);
340
341 return 1;
342 }
343
BN_sub_word(BIGNUM * a,BN_ULONG w)344 int BN_sub_word(BIGNUM *a, BN_ULONG w) {
345 int i;
346
347 w &= BN_MASK2;
348
349 /* degenerate case: w is zero */
350 if (!w) {
351 return 1;
352 }
353
354 /* degenerate case: a is zero */
355 if (BN_is_zero(a)) {
356 i = BN_set_word(a, w);
357 if (i != 0) {
358 BN_set_negative(a, 1);
359 }
360 return i;
361 }
362
363 /* handle 'a' when negative */
364 if (a->neg) {
365 a->neg = 0;
366 i = BN_add_word(a, w);
367 a->neg = 1;
368 return i;
369 }
370
371 if ((a->top == 1) && (a->d[0] < w)) {
372 a->d[0] = w - a->d[0];
373 a->neg = 1;
374 return 1;
375 }
376
377 i = 0;
378 for (;;) {
379 if (a->d[i] >= w) {
380 a->d[i] -= w;
381 break;
382 } else {
383 a->d[i] = (a->d[i] - w) & BN_MASK2;
384 i++;
385 w = 1;
386 }
387 }
388
389 if ((a->d[i] == 0) && (i == (a->top - 1))) {
390 a->top--;
391 }
392
393 return 1;
394 }
395