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
67int 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
104int 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) == NULL) {
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
162int 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) == NULL) {
195      return 0;
196    }
197    a->top++;
198    a->d[i] = w;
199  }
200
201  return 1;
202}
203
204int 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) == NULL) {
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
261int 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) == NULL) {
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    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
327int 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