crypto/openssl-0.9/crypto/bn/bn_mont.c

   1 /* crypto/bn/bn_mont.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  * Copyright (c) 1998-2006 The OpenSSL Project.  All rights reserved.
  60  *
  61  * Redistribution and use in source and binary forms, with or without
  62  * modification, are permitted provided that the following conditions
  63  * are met:
  64  *
  65  * 1. Redistributions of source code must retain the above copyright
  66  *    notice, this list of conditions and the following disclaimer.
  67  *
  68  * 2. Redistributions in binary form must reproduce the above copyright
  69  *    notice, this list of conditions and the following disclaimer in
  70  *    the documentation and/or other materials provided with the
  71  *    distribution.
  72  *
  73  * 3. All advertising materials mentioning features or use of this
  74  *    software must display the following acknowledgment:
  75  *    "This product includes software developed by the OpenSSL Project
  76  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  77  *
  78  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  79  *    endorse or promote products derived from this software without
  80  *    prior written permission. For written permission, please contact
  81  *    openssl-core@openssl.org.
  82  *
  83  * 5. Products derived from this software may not be called "OpenSSL"
  84  *    nor may "OpenSSL" appear in their names without prior written
  85  *    permission of the OpenSSL Project.
  86  *
  87  * 6. Redistributions of any form whatsoever must retain the following
  88  *    acknowledgment:
  89  *    "This product includes software developed by the OpenSSL Project
  90  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  91  *
  92  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  93  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  94  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  95  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  96  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  97  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  98  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  99  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 100  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 101  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 102  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 103  * OF THE POSSIBILITY OF SUCH DAMAGE.
 104  * ====================================================================
 105  *
 106  * This product includes cryptographic software written by Eric Young
 107  * (eay@cryptsoft.com).  This product includes software written by Tim
 108  * Hudson (tjh@cryptsoft.com).
 109  *
 110  */
 111
 112 /*
 113  * Details about Montgomery multiplication algorithms can be found at
 114  * http://security.ece.orst.edu/publications.html, e.g.
 115  * http://security.ece.orst.edu/koc/papers/j37acmon.pdf and
 116  * sections 3.8 and 4.2 in http://security.ece.orst.edu/koc/papers/r01rsasw.pdf
 117  */
 118
 119 #include <stdio.h>
 120 #include "cryptlib.h"
 121 #include "bn_lcl.h"
 122
 123 #define MONT_WORD /* use the faster word-based algorithm */
 124
 125 #if defined(MONT_WORD) && defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)
 126 /* This condition means we have a specific non-default build:
 127  * In the 0.9.8 branch, OPENSSL_BN_ASM_MONT is normally not set for any
 128  * BN_BITS2<=32 platform; an explicit "enable-montasm" is required.
 129  * I.e., if we are here, the user intentionally deviates from the
 130  * normal stable build to get better Montgomery performance from
 131  * the 0.9.9-dev backport.
 132  *
 133  * In this case only, we also enable BN_from_montgomery_word()
 134  * (another non-stable feature from 0.9.9-dev).
 135  */
 136 #define MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD
 137 #endif
 138
 139 #ifdef MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD
 140 static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont);
 141 #endif
 142
 143
 144
 145 int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
 146                           BN_MONT_CTX *mont, BN_CTX *ctx)
 147         {
 148         BIGNUM *tmp;
 149         int ret=0;
 150 #if defined(OPENSSL_BN_ASM_MONT) && defined(MONT_WORD)
 151         int num = mont->N.top;
 152
 153         if (num>1 && a->top==num && b->top==num)
 154                 {
 155                 if (bn_wexpand(r,num) == NULL) return(0);
 156 #if 0 /* for OpenSSL 0.9.9 mont->n0 */
 157                 if (bn_mul_mont(r->d,a->d,b->d,mont->N.d,mont->n0,num))
 158 #else
 159                 if (bn_mul_mont(r->d,a->d,b->d,mont->N.d,&mont->n0,num))
 160 #endif
 161                         {
 162                         r->neg = a->neg^b->neg;
 163                         r->top = num;
 164                         bn_correct_top(r);
 165                         return(1);
 166                         }
 167                 }
 168 #endif
 169
 170         BN_CTX_start(ctx);
 171         tmp = BN_CTX_get(ctx);
 172         if (tmp == NULL) goto err;
 173
 174         bn_check_top(tmp);
 175         if (a == b)
 176                 {
 177                 if (!BN_sqr(tmp,a,ctx)) goto err;
 178                 }
 179         else
 180                 {
 181                 if (!BN_mul(tmp,a,b,ctx)) goto err;
 182                 }
 183         /* reduce from aRR to aR */
 184 #ifdef MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD
 185         if (!BN_from_montgomery_word(r,tmp,mont)) goto err;
 186 #else
 187         if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;
 188 #endif
 189         bn_check_top(r);
 190         ret=1;
 191 err:
 192         BN_CTX_end(ctx);
 193         return(ret);
 194         }
 195
 196 #ifdef MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD
 197 static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont)
 198         {
 199         BIGNUM *n;
 200         BN_ULONG *ap,*np,*rp,n0,v,*nrp;
 201         int al,nl,max,i,x,ri;
 202
 203         n= &(mont->N);
 204         /* mont->ri is the size of mont->N in bits (rounded up
 205            to the word size) */
 206         al=ri=mont->ri/BN_BITS2;
 207
 208         nl=n->top;
 209         if ((al == 0) || (nl == 0)) { ret->top=0; return(1); }
 210
 211         max=(nl+al+1); /* allow for overflow (no?) XXX */
 212         if (bn_wexpand(r,max) == NULL) return(0);
 213
 214         r->neg^=n->neg;
 215         np=n->d;
 216         rp=r->d;
 217         nrp= &(r->d[nl]);
 218
 219         /* clear the top words of T */
 220         for (i=r->top; i<max; i++) /* memset? XXX */
 221                 r->d[i]=0;
 222
 223         r->top=max;
 224 #if 0 /* for OpenSSL 0.9.9 mont->n0 */
 225         n0=mont->n0[0];
 226 #else
 227         n0=mont->n0;
 228 #endif
 229
 230 #ifdef BN_COUNT
 231         fprintf(stderr,"word BN_from_montgomery_word %d * %d\n",nl,nl);
 232 #endif
 233         for (i=0; i<nl; i++)
 234                 {
 235 #ifdef __TANDEM
 236                 {
 237                    long long t1;
 238                    long long t2;
 239                    long long t3;
 240                    t1 = rp[0] * (n0 & 0177777);
 241                    t2 = 037777600000l;
 242                    t2 = n0 & t2;
 243                    t3 = rp[0] & 0177777;
 244                    t2 = (t3 * t2) & BN_MASK2;
 245                    t1 = t1 + t2;
 246                    v=bn_mul_add_words(rp,np,nl,(BN_ULONG) t1);
 247                 }
 248 #else
 249                 v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2);
 250 #endif
 251                 nrp++;
 252                 rp++;
 253                 if (((nrp[-1]+=v)&BN_MASK2) >= v)
 254                         continue;
 255                 else
 256                         {
 257                         if (((++nrp[0])&BN_MASK2) != 0) continue;
 258                         if (((++nrp[1])&BN_MASK2) != 0) continue;
 259                         for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ;
 260                         }
 261                 }
 262         bn_correct_top(r);
 263
 264         /* mont->ri will be a multiple of the word size and below code
 265          * is kind of BN_rshift(ret,r,mont->ri) equivalent */
 266         if (r->top <= ri)
 267                 {
 268                 ret->top=0;
 269                 return(1);
 270                 }
 271         al=r->top-ri;
 272
 273         if (bn_wexpand(ret,ri) == NULL) return(0);
 274         x=0-(((al-ri)>>(sizeof(al)*8-1))&1);
 275         ret->top=x=(ri&~x)|(al&x);      /* min(ri,al) */
 276         ret->neg=r->neg;
 277
 278         rp=ret->d;
 279         ap=&(r->d[ri]);
 280
 281         {
 282         size_t m1,m2;
 283
 284         v=bn_sub_words(rp,ap,np,ri);
 285         /* this ----------------^^ works even in al<ri case
 286          * thanks to zealous zeroing of top of the vector in the
 287          * beginning. */
 288
 289         /* if (al==ri && !v) || al>ri) nrp=rp; else nrp=ap; */
 290         /* in other words if subtraction result is real, then
 291          * trick unconditional memcpy below to perform in-place
 292          * "refresh" instead of actual copy. */
 293         m1=0-(size_t)(((al-ri)>>(sizeof(al)*8-1))&1);   /* al<ri */
 294         m2=0-(size_t)(((ri-al)>>(sizeof(al)*8-1))&1);   /* al>ri */
 295         m1|=m2;                 /* (al!=ri) */
 296         m1|=(0-(size_t)v);      /* (al!=ri || v) */
 297         m1&=~m2;                /* (al!=ri || v) && !al>ri */
 298         nrp=(BN_ULONG *)(((size_t)rp&~m1)|((size_t)ap&m1));
 299         }
 300
 301         /* 'i<ri' is chosen to eliminate dependency on input data, even
 302          * though it results in redundant copy in al<ri case. */
 303         for (i=0,ri-=4; i<ri; i+=4)
 304                 {
 305                 BN_ULONG t1,t2,t3,t4;
 306
 307                 t1=nrp[i+0];
 308                 t2=nrp[i+1];
 309                 t3=nrp[i+2];    ap[i+0]=0;
 310                 t4=nrp[i+3];    ap[i+1]=0;
 311                 rp[i+0]=t1;     ap[i+2]=0;
 312                 rp[i+1]=t2;     ap[i+3]=0;
 313                 rp[i+2]=t3;
 314                 rp[i+3]=t4;
 315                 }
 316         for (ri+=4; i<ri; i++)
 317                 rp[i]=nrp[i], ap[i]=0;
 318         bn_correct_top(r);
 319         bn_correct_top(ret);
 320         bn_check_top(ret);
 321
 322         return(1);
 323         }
 324
 325 int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,
 326              BN_CTX *ctx)
 327         {
 328         int retn=0;
 329         BIGNUM *t;
 330
 331         BN_CTX_start(ctx);
 332         if ((t = BN_CTX_get(ctx)) && BN_copy(t,a))
 333                 retn = BN_from_montgomery_word(ret,t,mont);
 334         BN_CTX_end(ctx);
 335         return retn;
 336         }
 337
 338 #else /* !MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD */
 339
 340 int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,
 341              BN_CTX *ctx)
 342         {
 343         int retn=0;
 344
 345 #ifdef MONT_WORD
 346         BIGNUM *n,*r;
 347         BN_ULONG *ap,*np,*rp,n0,v,*nrp;
 348         int al,nl,max,i,x,ri;
 349
 350         BN_CTX_start(ctx);
 351         if ((r = BN_CTX_get(ctx)) == NULL) goto err;
 352
 353         if (!BN_copy(r,a)) goto err;
 354         n= &(mont->N);
 355
 356         ap=a->d;
 357         /* mont->ri is the size of mont->N in bits (rounded up
 358            to the word size) */
 359         al=ri=mont->ri/BN_BITS2;
 360
 361         nl=n->top;
 362         if ((al == 0) || (nl == 0)) { r->top=0; return(1); }
 363
 364         max=(nl+al+1); /* allow for overflow (no?) XXX */
 365         if (bn_wexpand(r,max) == NULL) goto err;
 366
 367         r->neg=a->neg^n->neg;
 368         np=n->d;
 369         rp=r->d;
 370         nrp= &(r->d[nl]);
 371
 372         /* clear the top words of T */
 373 #if 1
 374         for (i=r->top; i<max; i++) /* memset? XXX */
 375                 r->d[i]=0;
 376 #else
 377         memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG));
 378 #endif
 379
 380         r->top=max;
 381         n0=mont->n0;
 382
 383 #ifdef BN_COUNT
 384         fprintf(stderr,"word BN_from_montgomery %d * %d\n",nl,nl);
 385 #endif
 386         for (i=0; i<nl; i++)
 387                 {
 388 #ifdef __TANDEM
 389                 {
 390                    long long t1;
 391                    long long t2;
 392                    long long t3;
 393                    t1 = rp[0] * (n0 & 0177777);
 394                    t2 = 037777600000l;
 395                    t2 = n0 & t2;
 396                    t3 = rp[0] & 0177777;
 397                    t2 = (t3 * t2) & BN_MASK2;
 398                    t1 = t1 + t2;
 399                    v=bn_mul_add_words(rp,np,nl,(BN_ULONG) t1);
 400                 }
 401 #else
 402                 v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2);
 403 #endif
 404                 nrp++;
 405                 rp++;
 406                 if (((nrp[-1]+=v)&BN_MASK2) >= v)
 407                         continue;
 408                 else
 409                         {
 410                         if (((++nrp[0])&BN_MASK2) != 0) continue;
 411                         if (((++nrp[1])&BN_MASK2) != 0) continue;
 412                         for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ;
 413                         }
 414                 }
 415         bn_correct_top(r);
 416
 417         /* mont->ri will be a multiple of the word size and below code
 418          * is kind of BN_rshift(ret,r,mont->ri) equivalent */
 419         if (r->top <= ri)
 420                 {
 421                 ret->top=0;
 422                 retn=1;
 423                 goto err;
 424                 }
 425         al=r->top-ri;
 426
 427 # define BRANCH_FREE 1
 428 # if BRANCH_FREE
 429         if (bn_wexpand(ret,ri) == NULL) goto err;
 430         x=0-(((al-ri)>>(sizeof(al)*8-1))&1);
 431         ret->top=x=(ri&~x)|(al&x);      /* min(ri,al) */
 432         ret->neg=r->neg;
 433
 434         rp=ret->d;
 435         ap=&(r->d[ri]);
 436
 437         {
 438         size_t m1,m2;
 439
 440         v=bn_sub_words(rp,ap,np,ri);
 441         /* this ----------------^^ works even in al<ri case
 442          * thanks to zealous zeroing of top of the vector in the
 443          * beginning. */
 444
 445         /* if (al==ri && !v) || al>ri) nrp=rp; else nrp=ap; */
 446         /* in other words if subtraction result is real, then
 447          * trick unconditional memcpy below to perform in-place
 448          * "refresh" instead of actual copy. */
 449         m1=0-(size_t)(((al-ri)>>(sizeof(al)*8-1))&1);   /* al<ri */
 450         m2=0-(size_t)(((ri-al)>>(sizeof(al)*8-1))&1);   /* al>ri */
 451         m1|=m2;                 /* (al!=ri) */
 452         m1|=(0-(size_t)v);      /* (al!=ri || v) */
 453         m1&=~m2;                /* (al!=ri || v) && !al>ri */
 454         nrp=(BN_ULONG *)(((size_t)rp&~m1)|((size_t)ap&m1));
 455         }
 456
 457         /* 'i<ri' is chosen to eliminate dependency on input data, even
 458          * though it results in redundant copy in al<ri case. */
 459         for (i=0,ri-=4; i<ri; i+=4)
 460                 {
 461                 BN_ULONG t1,t2,t3,t4;
 462
 463                 t1=nrp[i+0];
 464                 t2=nrp[i+1];
 465                 t3=nrp[i+2];    ap[i+0]=0;
 466                 t4=nrp[i+3];    ap[i+1]=0;
 467                 rp[i+0]=t1;     ap[i+2]=0;
 468                 rp[i+1]=t2;     ap[i+3]=0;
 469                 rp[i+2]=t3;
 470                 rp[i+3]=t4;
 471                 }
 472         for (ri+=4; i<ri; i++)
 473                 rp[i]=nrp[i], ap[i]=0;
 474         bn_correct_top(r);
 475         bn_correct_top(ret);
 476 # else
 477         if (bn_wexpand(ret,al) == NULL) goto err;
 478         ret->top=al;
 479         ret->neg=r->neg;
 480
 481         rp=ret->d;
 482         ap=&(r->d[ri]);
 483         al-=4;
 484         for (i=0; i<al; i+=4)
 485                 {
 486                 BN_ULONG t1,t2,t3,t4;
 487
 488                 t1=ap[i+0];
 489                 t2=ap[i+1];
 490                 t3=ap[i+2];
 491                 t4=ap[i+3];
 492                 rp[i+0]=t1;
 493                 rp[i+1]=t2;
 494                 rp[i+2]=t3;
 495                 rp[i+3]=t4;
 496                 }
 497         al+=4;
 498         for (; i<al; i++)
 499                 rp[i]=ap[i];
 500 # endif
 501 #else /* !MONT_WORD */
 502         BIGNUM *t1,*t2;
 503
 504         BN_CTX_start(ctx);
 505         t1 = BN_CTX_get(ctx);
 506         t2 = BN_CTX_get(ctx);
 507         if (t1 == NULL || t2 == NULL) goto err;
 508
 509         if (!BN_copy(t1,a)) goto err;
 510         BN_mask_bits(t1,mont->ri);
 511
 512         if (!BN_mul(t2,t1,&mont->Ni,ctx)) goto err;
 513         BN_mask_bits(t2,mont->ri);
 514
 515         if (!BN_mul(t1,t2,&mont->N,ctx)) goto err;
 516         if (!BN_add(t2,a,t1)) goto err;
 517         if (!BN_rshift(ret,t2,mont->ri)) goto err;
 518 #endif /* MONT_WORD */
 519
 520 #if !defined(BRANCH_FREE) || BRANCH_FREE==0
 521         if (BN_ucmp(ret, &(mont->N)) >= 0)
 522                 {
 523                 if (!BN_usub(ret,ret,&(mont->N))) goto err;
 524                 }
 525 #endif
 526         retn=1;
 527         bn_check_top(ret);
 528  err:
 529         BN_CTX_end(ctx);
 530         return(retn);
 531         }
 532 #endif /* MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD */
 533
 534 BN_MONT_CTX *BN_MONT_CTX_new(void)
 535         {
 536         BN_MONT_CTX *ret;
 537
 538         if ((ret=(BN_MONT_CTX *)OPENSSL_malloc(sizeof(BN_MONT_CTX))) == NULL)
 539                 return(NULL);
 540
 541         BN_MONT_CTX_init(ret);
 542         ret->flags=BN_FLG_MALLOCED;
 543         return(ret);
 544         }
 545
 546 void BN_MONT_CTX_init(BN_MONT_CTX *ctx)
 547         {
 548         ctx->ri=0;
 549         BN_init(&(ctx->RR));
 550         BN_init(&(ctx->N));
 551         BN_init(&(ctx->Ni));
 552 #if 0 /* for OpenSSL 0.9.9 mont->n0 */
 553         ctx->n0[0] = ctx->n0[1] = 0;
 554 #else
 555         ctx->n0 = 0;
 556 #endif
 557         ctx->flags=0;
 558         }
 559
 560 void BN_MONT_CTX_free(BN_MONT_CTX *mont)
 561         {
 562         if(mont == NULL)
 563             return;
 564
 565         BN_free(&(mont->RR));
 566         BN_free(&(mont->N));
 567         BN_free(&(mont->Ni));
 568         if (mont->flags & BN_FLG_MALLOCED)
 569                 OPENSSL_free(mont);
 570         }
 571
 572 int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
 573         {
 574         int ret = 0;
 575         BIGNUM *Ri,*R;
 576
 577         BN_CTX_start(ctx);
 578         if((Ri = BN_CTX_get(ctx)) == NULL) goto err;
 579         R= &(mont->RR);                                 /* grab RR as a temp */
 580         if (!BN_copy(&(mont->N),mod)) goto err;         /* Set N */
 581         mont->N.neg = 0;
 582
 583 #ifdef MONT_WORD
 584                 {
 585                 BIGNUM tmod;
 586                 BN_ULONG buf[2];
 587
 588                 mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
 589                 BN_zero(R);
 590 #if 0 /* for OpenSSL 0.9.9 mont->n0, would be "#if defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)",
 591          only certain BN_BITS2<=32 platforms actually need this */
 592                 if (!(BN_set_bit(R,2*BN_BITS2))) goto err;      /* R */
 593 #else
 594                 if (!(BN_set_bit(R,BN_BITS2))) goto err;        /* R */
 595 #endif
 596
 597                 buf[0]=mod->d[0]; /* tmod = N mod word size */
 598                 buf[1]=0;
 599
 600                 BN_init(&tmod);
 601                 tmod.d=buf;
 602                 tmod.top = buf[0] != 0 ? 1 : 0;
 603                 tmod.dmax=2;
 604                 tmod.neg=0;
 605
 606 #if 0 /* for OpenSSL 0.9.9 mont->n0, would be "#if defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)";
 607          only certain BN_BITS2<=32 platforms actually need this */
 608                                                                 tmod.top=0;
 609                 if ((buf[0] = mod->d[0]))                       tmod.top=1;
 610                 if ((buf[1] = mod->top>1 ? mod->d[1] : 0))      tmod.top=2;
 611
 612                 if ((BN_mod_inverse(Ri,R,&tmod,ctx)) == NULL)
 613                         goto err;
 614                 if (!BN_lshift(Ri,Ri,2*BN_BITS2)) goto err; /* R*Ri */
 615                 if (!BN_is_zero(Ri))
 616                         {
 617                         if (!BN_sub_word(Ri,1)) goto err;
 618                         }
 619                 else /* if N mod word size == 1 */
 620                         {
 621                         if (bn_expand(Ri,(int)sizeof(BN_ULONG)*2) == NULL)
 622                                 goto err;
 623                         /* Ri-- (mod double word size) */
 624                         Ri->neg=0;
 625                         Ri->d[0]=BN_MASK2;
 626                         Ri->d[1]=BN_MASK2;
 627                         Ri->top=2;
 628                         }
 629                 if (!BN_div(Ri,NULL,Ri,&tmod,ctx)) goto err;
 630                 /* Ni = (R*Ri-1)/N,
 631                  * keep only couple of least significant words: */
 632                 mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;
 633                 mont->n0[1] = (Ri->top > 1) ? Ri->d[1] : 0;
 634 #else
 635                                                         /* Ri = R^-1 mod N*/
 636                 if ((BN_mod_inverse(Ri,R,&tmod,ctx)) == NULL)
 637                         goto err;
 638                 if (!BN_lshift(Ri,Ri,BN_BITS2)) goto err; /* R*Ri */
 639                 if (!BN_is_zero(Ri))
 640                         {
 641                         if (!BN_sub_word(Ri,1)) goto err;
 642                         }
 643                 else /* if N mod word size == 1 */
 644                         {
 645                         if (!BN_set_word(Ri,BN_MASK2)) goto err;  /* Ri-- (mod word size) */
 646                         }
 647                 if (!BN_div(Ri,NULL,Ri,&tmod,ctx)) goto err;
 648                 /* Ni = (R*Ri-1)/N,
 649                  * keep only least significant word: */
 650 # if 0 /* for OpenSSL 0.9.9 mont->n0 */
 651                 mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;
 652                 mont->n0[1] = 0;
 653 # else
 654                 mont->n0 = (Ri->top > 0) ? Ri->d[0] : 0;
 655 # endif
 656 #endif
 657                 }
 658 #else /* !MONT_WORD */
 659                 { /* bignum version */
 660                 mont->ri=BN_num_bits(&mont->N);
 661                 BN_zero(R);
 662                 if (!BN_set_bit(R,mont->ri)) goto err;  /* R = 2^ri */
 663                                                         /* Ri = R^-1 mod N*/
 664                 if ((BN_mod_inverse(Ri,R,&mont->N,ctx)) == NULL)
 665                         goto err;
 666                 if (!BN_lshift(Ri,Ri,mont->ri)) goto err; /* R*Ri */
 667                 if (!BN_sub_word(Ri,1)) goto err;
 668                                                         /* Ni = (R*Ri-1) / N */
 669                 if (!BN_div(&(mont->Ni),NULL,Ri,&mont->N,ctx)) goto err;
 670                 }
 671 #endif
 672
 673         /* setup RR for conversions */
 674         BN_zero(&(mont->RR));
 675         if (!BN_set_bit(&(mont->RR),mont->ri*2)) goto err;
 676         if (!BN_mod(&(mont->RR),&(mont->RR),&(mont->N),ctx)) goto err;
 677
 678         ret = 1;
 679 err:
 680         BN_CTX_end(ctx);
 681         return ret;
 682         }
 683
 684 BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from)
 685         {
 686         if (to == from) return(to);
 687
 688         if (!BN_copy(&(to->RR),&(from->RR))) return NULL;
 689         if (!BN_copy(&(to->N),&(from->N))) return NULL;
 690         if (!BN_copy(&(to->Ni),&(from->Ni))) return NULL;
 691         to->ri=from->ri;
 692 #if 0 /* for OpenSSL 0.9.9 mont->n0 */
 693         to->n0[0]=from->n0[0];
 694         to->n0[1]=from->n0[1];
 695 #else
 696         to->n0=from->n0;
 697 #endif
 698         return(to);
 699         }
 700
 701 BN_MONT_CTX *BN_MONT_CTX_set_locked(BN_MONT_CTX **pmont, int lock,
 702                                         const BIGNUM *mod, BN_CTX *ctx)
 703         {
 704         int got_write_lock = 0;
 705         BN_MONT_CTX *ret;
 706
 707         CRYPTO_r_lock(lock);
 708         if (!*pmont)
 709                 {
 710                 CRYPTO_r_unlock(lock);
 711                 CRYPTO_w_lock(lock);
 712                 got_write_lock = 1;
 713
 714                 if (!*pmont)
 715                         {
 716                         ret = BN_MONT_CTX_new();
 717                         if (ret && !BN_MONT_CTX_set(ret, mod, ctx))
 718                                 BN_MONT_CTX_free(ret);
 719                         else
 720                                 *pmont = ret;
 721                         }
 722                 }
 723
 724         ret = *pmont;
 725
 726         if (got_write_lock)
 727                 CRYPTO_w_unlock(lock);
 728         else
 729                 CRYPTO_r_unlock(lock);
 730
 731         return ret;
 732         }