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1/* crypto/bn/bn_div.c */
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 <openssl/bn.h>
61#include "cryptlib.h"
62#include "bn_lcl.h"
63
64
65/* The old slow way */
66#if 0
67int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d,
68 BN_CTX *ctx)
69 {
70 int i,nm,nd;
71 int ret = 0;
72 BIGNUM *D;
73
74 bn_check_top(m);
75 bn_check_top(d);
76 if (BN_is_zero(d))
77 {
78 BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
79 return(0);
80 }
81
82 if (BN_ucmp(m,d) < 0)
83 {
84 if (rem != NULL)
85 { if (BN_copy(rem,m) == NULL) return(0); }
86 if (dv != NULL) BN_zero(dv);
87 return(1);
88 }
89
90 BN_CTX_start(ctx);
91 D = BN_CTX_get(ctx);
92 if (dv == NULL) dv = BN_CTX_get(ctx);
93 if (rem == NULL) rem = BN_CTX_get(ctx);
94 if (D == NULL || dv == NULL || rem == NULL)
95 goto end;
96
97 nd=BN_num_bits(d);
98 nm=BN_num_bits(m);
99 if (BN_copy(D,d) == NULL) goto end;
100 if (BN_copy(rem,m) == NULL) goto end;
101
102 /* The next 2 are needed so we can do a dv->d[0]|=1 later
103 * since BN_lshift1 will only work once there is a value :-) */
104 BN_zero(dv);
105 bn_wexpand(dv,1);
106 dv->top=1;
107
108 if (!BN_lshift(D,D,nm-nd)) goto end;
109 for (i=nm-nd; i>=0; i--)
110 {
111 if (!BN_lshift1(dv,dv)) goto end;
112 if (BN_ucmp(rem,D) >= 0)
113 {
114 dv->d[0]|=1;
115 if (!BN_usub(rem,rem,D)) goto end;
116 }
117/* CAN IMPROVE (and have now :=) */
118 if (!BN_rshift1(D,D)) goto end;
119 }
120 rem->neg=BN_is_zero(rem)?0:m->neg;
121 dv->neg=m->neg^d->neg;
122 ret = 1;
123 end:
124 BN_CTX_end(ctx);
125 return(ret);
126 }
127
128#else
129
130#if !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_NO_INLINE_ASM) \
131 && !defined(PEDANTIC) && !defined(BN_DIV3W)
132# if defined(__GNUC__) && __GNUC__>=2
133# if defined(__i386) || defined (__i386__)
134 /*
135 * There were two reasons for implementing this template:
136 * - GNU C generates a call to a function (__udivdi3 to be exact)
137 * in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
138 * understand why...);
139 * - divl doesn't only calculate quotient, but also leaves
140 * remainder in %edx which we can definitely use here:-)
141 *
142 * <appro@fy.chalmers.se>
143 */
144# define bn_div_words(n0,n1,d0) \
145 ({ asm volatile ( \
146 "divl %4" \
147 : "=a"(q), "=d"(rem) \
148 : "a"(n1), "d"(n0), "g"(d0) \
149 : "cc"); \
150 q; \
151 })
152# define REMAINDER_IS_ALREADY_CALCULATED
153# elif defined(__x86_64) && defined(SIXTY_FOUR_BIT_LONG)
154 /*
155 * Same story here, but it's 128-bit by 64-bit division. Wow!
156 * <appro@fy.chalmers.se>
157 */
158# define bn_div_words(n0,n1,d0) \
159 ({ asm volatile ( \
160 "divq %4" \
161 : "=a"(q), "=d"(rem) \
162 : "a"(n1), "d"(n0), "g"(d0) \
163 : "cc"); \
164 q; \
165 })
166# define REMAINDER_IS_ALREADY_CALCULATED
167# endif /* __<cpu> */
168# endif /* __GNUC__ */
169#endif /* OPENSSL_NO_ASM */
170
171
172/* BN_div[_no_branch] computes dv := num / divisor, rounding towards
173 * zero, and sets up rm such that dv*divisor + rm = num holds.
174 * Thus:
175 * dv->neg == num->neg ^ divisor->neg (unless the result is zero)
176 * rm->neg == num->neg (unless the remainder is zero)
177 * If 'dv' or 'rm' is NULL, the respective value is not returned.
178 */
179static int BN_div_no_branch(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num,
180 const BIGNUM *divisor, BN_CTX *ctx);
181int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
182 BN_CTX *ctx)
183 {
184 int norm_shift,i,loop;
185 BIGNUM *tmp,wnum,*snum,*sdiv,*res;
186 BN_ULONG *resp,*wnump;
187 BN_ULONG d0,d1;
188 int num_n,div_n;
189
190 /* Invalid zero-padding would have particularly bad consequences
191 * in the case of 'num', so don't just rely on bn_check_top() for this one
192 * (bn_check_top() works only for BN_DEBUG builds) */
193 if (num->top > 0 && num->d[num->top - 1] == 0)
194 {
195 BNerr(BN_F_BN_DIV,BN_R_NOT_INITIALIZED);
196 return 0;
197 }
198
199 bn_check_top(num);
200
201 if ((BN_get_flags(num, BN_FLG_CONSTTIME) != 0) || (BN_get_flags(divisor, BN_FLG_CONSTTIME) != 0))
202 {
203 return BN_div_no_branch(dv, rm, num, divisor, ctx);
204 }
205
206 bn_check_top(dv);
207 bn_check_top(rm);
208 /* bn_check_top(num); */ /* 'num' has been checked already */
209 bn_check_top(divisor);
210
211 if (BN_is_zero(divisor))
212 {
213 BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
214 return(0);
215 }
216
217 if (BN_ucmp(num,divisor) < 0)
218 {
219 if (rm != NULL)
220 { if (BN_copy(rm,num) == NULL) return(0); }
221 if (dv != NULL) BN_zero(dv);
222 return(1);
223 }
224
225 BN_CTX_start(ctx);
226 tmp=BN_CTX_get(ctx);
227 snum=BN_CTX_get(ctx);
228 sdiv=BN_CTX_get(ctx);
229 if (dv == NULL)
230 res=BN_CTX_get(ctx);
231 else res=dv;
232 if (sdiv == NULL || res == NULL) goto err;
233
234 /* First we normalise the numbers */
235 norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
236 if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err;
237 sdiv->neg=0;
238 norm_shift+=BN_BITS2;
239 if (!(BN_lshift(snum,num,norm_shift))) goto err;
240 snum->neg=0;
241 div_n=sdiv->top;
242 num_n=snum->top;
243 loop=num_n-div_n;
244 /* Lets setup a 'window' into snum
245 * This is the part that corresponds to the current
246 * 'area' being divided */
247 wnum.neg = 0;
248 wnum.d = &(snum->d[loop]);
249 wnum.top = div_n;
250 /* only needed when BN_ucmp messes up the values between top and max */
251 wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */
252
253 /* Get the top 2 words of sdiv */
254 /* div_n=sdiv->top; */
255 d0=sdiv->d[div_n-1];
256 d1=(div_n == 1)?0:sdiv->d[div_n-2];
257
258 /* pointer to the 'top' of snum */
259 wnump= &(snum->d[num_n-1]);
260
261 /* Setup to 'res' */
262 res->neg= (num->neg^divisor->neg);
263 if (!bn_wexpand(res,(loop+1))) goto err;
264 res->top=loop;
265 resp= &(res->d[loop-1]);
266
267 /* space for temp */
268 if (!bn_wexpand(tmp,(div_n+1))) goto err;
269
270 if (BN_ucmp(&wnum,sdiv) >= 0)
271 {
272 /* If BN_DEBUG_RAND is defined BN_ucmp changes (via
273 * bn_pollute) the const bignum arguments =>
274 * clean the values between top and max again */
275 bn_clear_top2max(&wnum);
276 bn_sub_words(wnum.d, wnum.d, sdiv->d, div_n);
277 *resp=1;
278 }
279 else
280 res->top--;
281 /* if res->top == 0 then clear the neg value otherwise decrease
282 * the resp pointer */
283 if (res->top == 0)
284 res->neg = 0;
285 else
286 resp--;
287
288 for (i=0; i<loop-1; i++, wnump--, resp--)
289 {
290 BN_ULONG q,l0;
291 /* the first part of the loop uses the top two words of
292 * snum and sdiv to calculate a BN_ULONG q such that
293 * | wnum - sdiv * q | < sdiv */
294#if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM)
295 BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG);
296 q=bn_div_3_words(wnump,d1,d0);
297#else
298 BN_ULONG n0,n1,rem=0;
299
300 n0=wnump[0];
301 n1=wnump[-1];
302 if (n0 == d0)
303 q=BN_MASK2;
304 else /* n0 < d0 */
305 {
306#ifdef BN_LLONG
307 BN_ULLONG t2;
308
309#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
310 q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0);
311#else
312 q=bn_div_words(n0,n1,d0);
313#ifdef BN_DEBUG_LEVITTE
314 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
315X) -> 0x%08X\n",
316 n0, n1, d0, q);
317#endif
318#endif
319
320#ifndef REMAINDER_IS_ALREADY_CALCULATED
321 /*
322 * rem doesn't have to be BN_ULLONG. The least we
323 * know it's less that d0, isn't it?
324 */
325 rem=(n1-q*d0)&BN_MASK2;
326#endif
327 t2=(BN_ULLONG)d1*q;
328
329 for (;;)
330 {
331 if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
332 break;
333 q--;
334 rem += d0;
335 if (rem < d0) break; /* don't let rem overflow */
336 t2 -= d1;
337 }
338#else /* !BN_LLONG */
339 BN_ULONG t2l,t2h,ql,qh;
340
341 q=bn_div_words(n0,n1,d0);
342#ifdef BN_DEBUG_LEVITTE
343 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
344X) -> 0x%08X\n",
345 n0, n1, d0, q);
346#endif
347#ifndef REMAINDER_IS_ALREADY_CALCULATED
348 rem=(n1-q*d0)&BN_MASK2;
349#endif
350
351#if defined(BN_UMULT_LOHI)
352 BN_UMULT_LOHI(t2l,t2h,d1,q);
353#elif defined(BN_UMULT_HIGH)
354 t2l = d1 * q;
355 t2h = BN_UMULT_HIGH(d1,q);
356#else
357 t2l=LBITS(d1); t2h=HBITS(d1);
358 ql =LBITS(q); qh =HBITS(q);
359 mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
360#endif
361
362 for (;;)
363 {
364 if ((t2h < rem) ||
365 ((t2h == rem) && (t2l <= wnump[-2])))
366 break;
367 q--;
368 rem += d0;
369 if (rem < d0) break; /* don't let rem overflow */
370 if (t2l < d1) t2h--; t2l -= d1;
371 }
372#endif /* !BN_LLONG */
373 }
374#endif /* !BN_DIV3W */
375
376 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
377 tmp->d[div_n]=l0;
378 wnum.d--;
379 /* ingore top values of the bignums just sub the two
380 * BN_ULONG arrays with bn_sub_words */
381 if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n+1))
382 {
383 /* Note: As we have considered only the leading
384 * two BN_ULONGs in the calculation of q, sdiv * q
385 * might be greater than wnum (but then (q-1) * sdiv
386 * is less or equal than wnum)
387 */
388 q--;
389 if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n))
390 /* we can't have an overflow here (assuming
391 * that q != 0, but if q == 0 then tmp is
392 * zero anyway) */
393 (*wnump)++;
394 }
395 /* store part of the result */
396 *resp = q;
397 }
398 bn_correct_top(snum);
399 if (rm != NULL)
400 {
401 /* Keep a copy of the neg flag in num because if rm==num
402 * BN_rshift() will overwrite it.
403 */
404 int neg = num->neg;
405 BN_rshift(rm,snum,norm_shift);
406 if (!BN_is_zero(rm))
407 rm->neg = neg;
408 bn_check_top(rm);
409 }
410 BN_CTX_end(ctx);
411 return(1);
412err:
413 bn_check_top(rm);
414 BN_CTX_end(ctx);
415 return(0);
416 }
417
418
419/* BN_div_no_branch is a special version of BN_div. It does not contain
420 * branches that may leak sensitive information.
421 */
422static int BN_div_no_branch(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num,
423 const BIGNUM *divisor, BN_CTX *ctx)
424 {
425 int norm_shift,i,loop;
426 BIGNUM *tmp,wnum,*snum,*sdiv,*res;
427 BN_ULONG *resp,*wnump;
428 BN_ULONG d0,d1;
429 int num_n,div_n;
430
431 bn_check_top(dv);
432 bn_check_top(rm);
433 /* bn_check_top(num); */ /* 'num' has been checked in BN_div() */
434 bn_check_top(divisor);
435
436 if (BN_is_zero(divisor))
437 {
438 BNerr(BN_F_BN_DIV_NO_BRANCH,BN_R_DIV_BY_ZERO);
439 return(0);
440 }
441
442 BN_CTX_start(ctx);
443 tmp=BN_CTX_get(ctx);
444 snum=BN_CTX_get(ctx);
445 sdiv=BN_CTX_get(ctx);
446 if (dv == NULL)
447 res=BN_CTX_get(ctx);
448 else res=dv;
449 if (sdiv == NULL || res == NULL) goto err;
450
451 /* First we normalise the numbers */
452 norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
453 if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err;
454 sdiv->neg=0;
455 norm_shift+=BN_BITS2;
456 if (!(BN_lshift(snum,num,norm_shift))) goto err;
457 snum->neg=0;
458
459 /* Since we don't know whether snum is larger than sdiv,
460 * we pad snum with enough zeroes without changing its
461 * value.
462 */
463 if (snum->top <= sdiv->top+1)
464 {
465 if (bn_wexpand(snum, sdiv->top + 2) == NULL) goto err;
466 for (i = snum->top; i < sdiv->top + 2; i++) snum->d[i] = 0;
467 snum->top = sdiv->top + 2;
468 }
469 else
470 {
471 if (bn_wexpand(snum, snum->top + 1) == NULL) goto err;
472 snum->d[snum->top] = 0;
473 snum->top ++;
474 }
475
476 div_n=sdiv->top;
477 num_n=snum->top;
478 loop=num_n-div_n;
479 /* Lets setup a 'window' into snum
480 * This is the part that corresponds to the current
481 * 'area' being divided */
482 wnum.neg = 0;
483 wnum.d = &(snum->d[loop]);
484 wnum.top = div_n;
485 /* only needed when BN_ucmp messes up the values between top and max */
486 wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */
487
488 /* Get the top 2 words of sdiv */
489 /* div_n=sdiv->top; */
490 d0=sdiv->d[div_n-1];
491 d1=(div_n == 1)?0:sdiv->d[div_n-2];
492
493 /* pointer to the 'top' of snum */
494 wnump= &(snum->d[num_n-1]);
495
496 /* Setup to 'res' */
497 res->neg= (num->neg^divisor->neg);
498 if (!bn_wexpand(res,(loop+1))) goto err;
499 res->top=loop-1;
500 resp= &(res->d[loop-1]);
501
502 /* space for temp */
503 if (!bn_wexpand(tmp,(div_n+1))) goto err;
504
505 /* if res->top == 0 then clear the neg value otherwise decrease
506 * the resp pointer */
507 if (res->top == 0)
508 res->neg = 0;
509 else
510 resp--;
511
512 for (i=0; i<loop-1; i++, wnump--, resp--)
513 {
514 BN_ULONG q,l0;
515 /* the first part of the loop uses the top two words of
516 * snum and sdiv to calculate a BN_ULONG q such that
517 * | wnum - sdiv * q | < sdiv */
518#if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM)
519 BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG);
520 q=bn_div_3_words(wnump,d1,d0);
521#else
522 BN_ULONG n0,n1,rem=0;
523
524 n0=wnump[0];
525 n1=wnump[-1];
526 if (n0 == d0)
527 q=BN_MASK2;
528 else /* n0 < d0 */
529 {
530#ifdef BN_LLONG
531 BN_ULLONG t2;
532
533#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
534 q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0);
535#else
536 q=bn_div_words(n0,n1,d0);
537#ifdef BN_DEBUG_LEVITTE
538 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
539X) -> 0x%08X\n",
540 n0, n1, d0, q);
541#endif
542#endif
543
544#ifndef REMAINDER_IS_ALREADY_CALCULATED
545 /*
546 * rem doesn't have to be BN_ULLONG. The least we
547 * know it's less that d0, isn't it?
548 */
549 rem=(n1-q*d0)&BN_MASK2;
550#endif
551 t2=(BN_ULLONG)d1*q;
552
553 for (;;)
554 {
555 if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
556 break;
557 q--;
558 rem += d0;
559 if (rem < d0) break; /* don't let rem overflow */
560 t2 -= d1;
561 }
562#else /* !BN_LLONG */
563 BN_ULONG t2l,t2h,ql,qh;
564
565 q=bn_div_words(n0,n1,d0);
566#ifdef BN_DEBUG_LEVITTE
567 fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
568X) -> 0x%08X\n",
569 n0, n1, d0, q);
570#endif
571#ifndef REMAINDER_IS_ALREADY_CALCULATED
572 rem=(n1-q*d0)&BN_MASK2;
573#endif
574
575#if defined(BN_UMULT_LOHI)
576 BN_UMULT_LOHI(t2l,t2h,d1,q);
577#elif defined(BN_UMULT_HIGH)
578 t2l = d1 * q;
579 t2h = BN_UMULT_HIGH(d1,q);
580#else
581 t2l=LBITS(d1); t2h=HBITS(d1);
582 ql =LBITS(q); qh =HBITS(q);
583 mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
584#endif
585
586 for (;;)
587 {
588 if ((t2h < rem) ||
589 ((t2h == rem) && (t2l <= wnump[-2])))
590 break;
591 q--;
592 rem += d0;
593 if (rem < d0) break; /* don't let rem overflow */
594 if (t2l < d1) t2h--; t2l -= d1;
595 }
596#endif /* !BN_LLONG */
597 }
598#endif /* !BN_DIV3W */
599
600 l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
601 tmp->d[div_n]=l0;
602 wnum.d--;
603 /* ingore top values of the bignums just sub the two
604 * BN_ULONG arrays with bn_sub_words */
605 if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n+1))
606 {
607 /* Note: As we have considered only the leading
608 * two BN_ULONGs in the calculation of q, sdiv * q
609 * might be greater than wnum (but then (q-1) * sdiv
610 * is less or equal than wnum)
611 */
612 q--;
613 if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n))
614 /* we can't have an overflow here (assuming
615 * that q != 0, but if q == 0 then tmp is
616 * zero anyway) */
617 (*wnump)++;
618 }
619 /* store part of the result */
620 *resp = q;
621 }
622 bn_correct_top(snum);
623 if (rm != NULL)
624 {
625 /* Keep a copy of the neg flag in num because if rm==num
626 * BN_rshift() will overwrite it.
627 */
628 int neg = num->neg;
629 BN_rshift(rm,snum,norm_shift);
630 if (!BN_is_zero(rm))
631 rm->neg = neg;
632 bn_check_top(rm);
633 }
634 bn_correct_top(res);
635 BN_CTX_end(ctx);
636 return(1);
637err:
638 bn_check_top(rm);
639 BN_CTX_end(ctx);
640 return(0);
641 }
642
643#endif
generated by cgit v1.2.3-55-g6feb (git 2.39.1) at 2025-04-03 03:47:19 +0000