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
65int 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
102int 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
160int 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
202int 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
259int 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
344int 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