1/* crypto/bn/bn_exp.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) 1998-2000 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#include <stdio.h> 114#include "cryptlib.h" 115#include "bn_lcl.h" 116#ifdef ATALLA 117# include <alloca.h> 118# include <atasi.h> 119# include <assert.h> 120# include <dlfcn.h> 121#endif 122 123 124#define TABLE_SIZE 32 125 126/* slow but works */ 127int BN_mod_mul(BIGNUM *ret, BIGNUM *a, BIGNUM *b, const BIGNUM *m, BN_CTX *ctx) 128 { 129 BIGNUM *t; 130 int r=0; 131 132 bn_check_top(a); 133 bn_check_top(b); 134 bn_check_top(m); 135 136 BN_CTX_start(ctx); 137 if ((t = BN_CTX_get(ctx)) == NULL) goto err; 138 if (a == b) 139 { if (!BN_sqr(t,a,ctx)) goto err; } 140 else 141 { if (!BN_mul(t,a,b,ctx)) goto err; } 142 if (!BN_mod(ret,t,m,ctx)) goto err; 143 r=1; 144err: 145 BN_CTX_end(ctx); 146 return(r); 147 } 148 149 150/* this one works - simple but works */ 151int BN_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx) 152 { 153 int i,bits,ret=0; 154 BIGNUM *v,*rr; 155 156 BN_CTX_start(ctx); 157 if ((r == a) || (r == p)) 158 rr = BN_CTX_get(ctx); 159 else 160 rr = r; 161 if ((v = BN_CTX_get(ctx)) == NULL) goto err; 162 163 if (BN_copy(v,a) == NULL) goto err; 164 bits=BN_num_bits(p); 165 166 if (BN_is_odd(p)) 167 { if (BN_copy(rr,a) == NULL) goto err; } 168 else { if (!BN_one(rr)) goto err; } 169 170 for (i=1; i<bits; i++) 171 { 172 if (!BN_sqr(v,v,ctx)) goto err; 173 if (BN_is_bit_set(p,i)) 174 { 175 if (!BN_mul(rr,rr,v,ctx)) goto err; 176 } 177 } 178 ret=1; 179err: 180 if (r != rr) BN_copy(r,rr); 181 BN_CTX_end(ctx); 182 return(ret); 183 } 184 185 186#ifdef ATALLA 187 188/* 189 * This routine will dynamically check for the existance of an Atalla AXL-200 190 * SSL accelerator module. If one is found, the variable 191 * asi_accelerator_present is set to 1 and the function pointers 192 * ptr_ASI_xxxxxx above will be initialized to corresponding ASI API calls. 193 */ 194typedef int tfnASI_GetPerformanceStatistics(int reset_flag, 195 unsigned int *ret_buf); 196typedef int tfnASI_GetHardwareConfig(long card_num, unsigned int *ret_buf); 197typedef int tfnASI_RSAPrivateKeyOpFn(RSAPrivateKey * rsaKey, 198 unsigned char *output, 199 unsigned char *input, 200 unsigned int modulus_len); 201 202static tfnASI_GetHardwareConfig *ptr_ASI_GetHardwareConfig; 203static tfnASI_RSAPrivateKeyOpFn *ptr_ASI_RSAPrivateKeyOpFn; 204static tfnASI_GetPerformanceStatistics *ptr_ASI_GetPerformanceStatistics; 205static int asi_accelerator_present; 206static int tried_atalla; 207 208void atalla_initialize_accelerator_handle(void) 209 { 210 void *dl_handle; 211 int status; 212 unsigned int config_buf[1024]; 213 static int tested; 214 215 if(tested) 216 return; 217 218 tested=1; 219 220 bzero((void *)config_buf, 1024); 221 222 /* 223 * Check to see if the library is present on the system 224 */ 225 dl_handle = dlopen("atasi.so", RTLD_NOW); 226 if (dl_handle == (void *) NULL) 227 { 228/* printf("atasi.so library is not present on the system\n"); 229 printf("No HW acceleration available\n");*/ 230 return; 231 } 232 233 /* 234 * The library is present. Now we'll check to insure that the 235 * LDM is up and running. First we'll get the address of the 236 * function in the atasi library that we need to see if the 237 * LDM is operating. 238 */ 239 240 ptr_ASI_GetHardwareConfig = 241 (tfnASI_GetHardwareConfig *)dlsym(dl_handle,"ASI_GetHardwareConfig"); 242 243 if (ptr_ASI_GetHardwareConfig) 244 { 245 /* 246 * We found the call, now we'll get our config 247 * status. If we get a non 0 result, the LDM is not 248 * running and we cannot use the Atalla ASI * 249 * library. 250 */ 251 status = (*ptr_ASI_GetHardwareConfig)(0L, config_buf); 252 if (status != 0) 253 { 254 printf("atasi.so library is present but not initialized\n"); 255 printf("No HW acceleration available\n"); 256 return; 257 } 258 } 259 else 260 { 261/* printf("We found the library, but not the function. Very Strange!\n");*/ 262 return ; 263 } 264 265 /* 266 * It looks like we have acceleration capabilities. Load up the 267 * pointers to our ASI API calls. 268 */ 269 ptr_ASI_RSAPrivateKeyOpFn= 270 (tfnASI_RSAPrivateKeyOpFn *)dlsym(dl_handle, "ASI_RSAPrivateKeyOpFn"); 271 if (ptr_ASI_RSAPrivateKeyOpFn == NULL) 272 { 273/* printf("We found the library, but no RSA function. Very Strange!\n");*/ 274 return; 275 } 276 277 ptr_ASI_GetPerformanceStatistics = 278 (tfnASI_GetPerformanceStatistics *)dlsym(dl_handle, "ASI_GetPerformanceStatistics"); 279 if (ptr_ASI_GetPerformanceStatistics == NULL) 280 { 281/* printf("We found the library, but no stat function. Very Strange!\n");*/ 282 return; 283 } 284 285 /* 286 * Indicate that acceleration is available 287 */ 288 asi_accelerator_present = 1; 289 290/* printf("This system has acceleration!\n");*/ 291 292 return; 293 } 294 295/* make sure this only gets called once when bn_mod_exp calls bn_mod_exp_mont */ 296int BN_mod_exp_atalla(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m) 297 { 298 unsigned char *abin; 299 unsigned char *pbin; 300 unsigned char *mbin; 301 unsigned char *rbin; 302 int an,pn,mn,ret; 303 RSAPrivateKey keydata; 304 305 atalla_initialize_accelerator_handle(); 306 if(!asi_accelerator_present) 307 return 0; 308 309 310/* We should be able to run without size testing */ 311# define ASIZE 128 312 an=BN_num_bytes(a); 313 pn=BN_num_bytes(p); 314 mn=BN_num_bytes(m); 315 316 if(an <= ASIZE && pn <= ASIZE && mn <= ASIZE) 317 { 318 int size=mn; 319 320 assert(an <= mn); 321 abin=alloca(size); 322 memset(abin,'\0',mn); 323 BN_bn2bin(a,abin+size-an); 324 325 pbin=alloca(pn); 326 BN_bn2bin(p,pbin); 327 328 mbin=alloca(size); 329 memset(mbin,'\0',mn); 330 BN_bn2bin(m,mbin+size-mn); 331 332 rbin=alloca(size); 333 334 memset(&keydata,'\0',sizeof keydata); 335 keydata.privateExponent.data=pbin; 336 keydata.privateExponent.len=pn; 337 keydata.modulus.data=mbin; 338 keydata.modulus.len=size; 339 340 ret=(*ptr_ASI_RSAPrivateKeyOpFn)(&keydata,rbin,abin,keydata.modulus.len); 341/*fprintf(stderr,"!%s\n",BN_bn2hex(a));*/ 342 if(!ret) 343 { 344 BN_bin2bn(rbin,keydata.modulus.len,r); 345/*fprintf(stderr,"?%s\n",BN_bn2hex(r));*/ 346 return 1; 347 } 348 } 349 return 0; 350 } 351#endif /* def ATALLA */ 352 353 354int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m, 355 BN_CTX *ctx) 356 { 357 int ret; 358 359 bn_check_top(a); 360 bn_check_top(p); 361 bn_check_top(m); 362 363#ifdef ATALLA 364 if(BN_mod_exp_atalla(r,a,p,m)) 365 return 1; 366/* If it fails, try the other methods (but don't try atalla again) */ 367 tried_atalla=1; 368#endif 369 370#ifdef MONT_MUL_MOD 371 /* I have finally been able to take out this pre-condition of 372 * the top bit being set. It was caused by an error in BN_div 373 * with negatives. There was also another problem when for a^b%m 374 * a >= m. eay 07-May-97 */ 375/* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */ 376 377 if (BN_is_odd(m)) 378 { 379 if (a->top == 1) 380 { 381 BN_ULONG A = a->d[0]; 382 ret=BN_mod_exp_mont_word(r,A,p,m,ctx,NULL); 383 } 384 else 385 ret=BN_mod_exp_mont(r,a,p,m,ctx,NULL); 386 } 387 else 388#endif 389#ifdef RECP_MUL_MOD 390 { ret=BN_mod_exp_recp(r,a,p,m,ctx); } 391#else 392 { ret=BN_mod_exp_simple(r,a,p,m,ctx); } 393#endif 394 395#ifdef ATALLA 396 tried_atalla=0; 397#endif 398 399 return(ret); 400 } 401 402 403int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 404 const BIGNUM *m, BN_CTX *ctx) 405 { 406 int i,j,bits,ret=0,wstart,wend,window,wvalue; 407 int start=1,ts=0; 408 BIGNUM *aa; 409 BIGNUM val[TABLE_SIZE]; 410 BN_RECP_CTX recp; 411 412 bits=BN_num_bits(p); 413 414 if (bits == 0) 415 { 416 BN_one(r); 417 return(1); 418 } 419 420 BN_CTX_start(ctx); 421 if ((aa = BN_CTX_get(ctx)) == NULL) goto err; 422 423 BN_RECP_CTX_init(&recp); 424 if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err; 425 426 BN_init(&(val[0])); 427 ts=1; 428 429 if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */ 430 431 window = BN_window_bits_for_exponent_size(bits); 432 if (window > 1) 433 { 434 if (!BN_mod_mul_reciprocal(aa,&(val[0]),&(val[0]),&recp,ctx)) 435 goto err; /* 2 */ 436 j=1<<(window-1); 437 for (i=1; i<j; i++) 438 { 439 BN_init(&val[i]); 440 if (!BN_mod_mul_reciprocal(&(val[i]),&(val[i-1]),aa,&recp,ctx)) 441 goto err; 442 } 443 ts=i; 444 } 445 446 start=1; /* This is used to avoid multiplication etc 447 * when there is only the value '1' in the 448 * buffer. */ 449 wvalue=0; /* The 'value' of the window */ 450 wstart=bits-1; /* The top bit of the window */ 451 wend=0; /* The bottom bit of the window */ 452 453 if (!BN_one(r)) goto err; 454 455 for (;;) 456 { 457 if (BN_is_bit_set(p,wstart) == 0) 458 { 459 if (!start) 460 if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx)) 461 goto err; 462 if (wstart == 0) break; 463 wstart--; 464 continue; 465 } 466 /* We now have wstart on a 'set' bit, we now need to work out 467 * how bit a window to do. To do this we need to scan 468 * forward until the last set bit before the end of the 469 * window */ 470 j=wstart; 471 wvalue=1; 472 wend=0; 473 for (i=1; i<window; i++) 474 { 475 if (wstart-i < 0) break; 476 if (BN_is_bit_set(p,wstart-i)) 477 { 478 wvalue<<=(i-wend); 479 wvalue|=1; 480 wend=i; 481 } 482 } 483 484 /* wend is the size of the current window */ 485 j=wend+1; 486 /* add the 'bytes above' */ 487 if (!start) 488 for (i=0; i<j; i++) 489 { 490 if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx)) 491 goto err; 492 } 493 494 /* wvalue will be an odd number < 2^window */ 495 if (!BN_mod_mul_reciprocal(r,r,&(val[wvalue>>1]),&recp,ctx)) 496 goto err; 497 498 /* move the 'window' down further */ 499 wstart-=wend+1; 500 wvalue=0; 501 start=0; 502 if (wstart < 0) break; 503 } 504 ret=1; 505err: 506 BN_CTX_end(ctx); 507 for (i=0; i<ts; i++) 508 BN_clear_free(&(val[i])); 509 BN_RECP_CTX_free(&recp); 510 return(ret); 511 } 512 513 514int BN_mod_exp_mont(BIGNUM *rr, BIGNUM *a, const BIGNUM *p, 515 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) 516 { 517 int i,j,bits,ret=0,wstart,wend,window,wvalue; 518 int start=1,ts=0; 519 BIGNUM *d,*r; 520 BIGNUM *aa; 521 BIGNUM val[TABLE_SIZE]; 522 BN_MONT_CTX *mont=NULL; 523 524 bn_check_top(a); 525 bn_check_top(p); 526 bn_check_top(m); 527 528#ifdef ATALLA 529 if(!tried_atalla && BN_mod_exp_atalla(rr,a,p,m)) 530 return 1; 531/* If it fails, try the other methods */ 532#endif 533 534 if (!(m->d[0] & 1)) 535 { 536 BNerr(BN_F_BN_MOD_EXP_MONT,BN_R_CALLED_WITH_EVEN_MODULUS); 537 return(0); 538 } 539 bits=BN_num_bits(p); 540 if (bits == 0) 541 { 542 BN_one(rr); 543 return(1); 544 } 545 BN_CTX_start(ctx); 546 d = BN_CTX_get(ctx); 547 r = BN_CTX_get(ctx); 548 if (d == NULL || r == NULL) goto err; 549 550 /* If this is not done, things will break in the montgomery 551 * part */ 552 553 if (in_mont != NULL) 554 mont=in_mont; 555 else 556 { 557 if ((mont=BN_MONT_CTX_new()) == NULL) goto err; 558 if (!BN_MONT_CTX_set(mont,m,ctx)) goto err; 559 } 560 561 BN_init(&val[0]); 562 ts=1; 563 if (BN_ucmp(a,m) >= 0) 564 { 565 if (!BN_mod(&(val[0]),a,m,ctx)) 566 goto err; 567 aa= &(val[0]); 568 } 569 else 570 aa=a; 571 if (!BN_to_montgomery(&(val[0]),aa,mont,ctx)) goto err; /* 1 */ 572 573 window = BN_window_bits_for_exponent_size(bits); 574 if (window > 1) 575 { 576 if (!BN_mod_mul_montgomery(d,&(val[0]),&(val[0]),mont,ctx)) goto err; /* 2 */ 577 j=1<<(window-1); 578 for (i=1; i<j; i++) 579 { 580 BN_init(&(val[i])); 581 if (!BN_mod_mul_montgomery(&(val[i]),&(val[i-1]),d,mont,ctx)) 582 goto err; 583 } 584 ts=i; 585 } 586 587 start=1; /* This is used to avoid multiplication etc 588 * when there is only the value '1' in the 589 * buffer. */ 590 wvalue=0; /* The 'value' of the window */ 591 wstart=bits-1; /* The top bit of the window */ 592 wend=0; /* The bottom bit of the window */ 593 594 if (!BN_to_montgomery(r,BN_value_one(),mont,ctx)) goto err; 595 for (;;) 596 { 597 if (BN_is_bit_set(p,wstart) == 0) 598 { 599 if (!start) 600 { 601 if (!BN_mod_mul_montgomery(r,r,r,mont,ctx)) 602 goto err; 603 } 604 if (wstart == 0) break; 605 wstart--; 606 continue; 607 } 608 /* We now have wstart on a 'set' bit, we now need to work out 609 * how bit a window to do. To do this we need to scan 610 * forward until the last set bit before the end of the 611 * window */ 612 j=wstart; 613 wvalue=1; 614 wend=0; 615 for (i=1; i<window; i++) 616 { 617 if (wstart-i < 0) break; 618 if (BN_is_bit_set(p,wstart-i)) 619 { 620 wvalue<<=(i-wend); 621 wvalue|=1; 622 wend=i; 623 } 624 } 625 626 /* wend is the size of the current window */ 627 j=wend+1; 628 /* add the 'bytes above' */ 629 if (!start) 630 for (i=0; i<j; i++) 631 { 632 if (!BN_mod_mul_montgomery(r,r,r,mont,ctx)) 633 goto err; 634 } 635 636 /* wvalue will be an odd number < 2^window */ 637 if (!BN_mod_mul_montgomery(r,r,&(val[wvalue>>1]),mont,ctx)) 638 goto err; 639 640 /* move the 'window' down further */ 641 wstart-=wend+1; 642 wvalue=0; 643 start=0; 644 if (wstart < 0) break; 645 } 646 if (!BN_from_montgomery(rr,r,mont,ctx)) goto err; 647 ret=1; 648err: 649 if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont); 650 BN_CTX_end(ctx); 651 for (i=0; i<ts; i++) 652 BN_clear_free(&(val[i])); 653 return(ret); 654 } 655 656int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p, 657 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) 658 { 659 BN_MONT_CTX *mont = NULL; 660 int b, bits, ret=0; 661 int r_is_one; 662 BN_ULONG w, next_w; 663 BIGNUM *d, *r, *t; 664 BIGNUM *swap_tmp; 665#define BN_MOD_MUL_WORD(r, w, m) \ 666 (BN_mul_word(r, (w)) && \ 667 (/* BN_ucmp(r, (m)) < 0 ? 1 :*/ \ 668 (BN_mod(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1)))) 669 /* BN_MOD_MUL_WORD is only used with 'w' large, 670 * so the BN_ucmp test is probably more overhead 671 * than always using BN_mod (which uses BN_copy if 672 * a similar test returns true). */ 673#define BN_TO_MONTGOMERY_WORD(r, w, mont) \ 674 (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx)) 675 676 bn_check_top(p); 677 bn_check_top(m); 678 679 if (!(m->d[0] & 1)) 680 { 681 BNerr(BN_F_BN_MOD_EXP_MONT_WORD,BN_R_CALLED_WITH_EVEN_MODULUS); 682 return(0); 683 } 684 bits = BN_num_bits(p); 685 if (bits == 0) 686 { 687 BN_one(rr); 688 return(1); 689 } 690 BN_CTX_start(ctx); 691 d = BN_CTX_get(ctx); 692 r = BN_CTX_get(ctx); 693 t = BN_CTX_get(ctx); 694 if (d == NULL || r == NULL || t == NULL) goto err; 695 696#ifdef ATALLA 697 if (!tried_atalla) 698 { 699 BN_set_word(t, a); 700 if (BN_mod_exp_atalla(rr, t, p, m)) 701 { 702 BN_CTX_end(ctx); 703 return 1; 704 } 705 } 706/* If it fails, try the other methods */ 707#endif 708 709 if (in_mont != NULL) 710 mont=in_mont; 711 else 712 { 713 if ((mont = BN_MONT_CTX_new()) == NULL) goto err; 714 if (!BN_MONT_CTX_set(mont, m, ctx)) goto err; 715 } 716 717 r_is_one = 1; /* except for Montgomery factor */ 718 719 /* bits-1 >= 0 */ 720 721 /* The result is accumulated in the product r*w. */ 722 w = a; /* bit 'bits-1' of 'p' is always set */ 723 for (b = bits-2; b >= 0; b--) 724 { 725 /* First, square r*w. */ 726 next_w = w*w; 727 if ((next_w/w) != w) /* overflow */ 728 { 729 if (r_is_one) 730 { 731 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err; 732 r_is_one = 0; 733 } 734 else 735 { 736 if (!BN_MOD_MUL_WORD(r, w, m)) goto err; 737 } 738 next_w = 1; 739 } 740 w = next_w; 741 if (!r_is_one) 742 { 743 if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) goto err; 744 } 745 746 /* Second, multiply r*w by 'a' if exponent bit is set. */ 747 if (BN_is_bit_set(p, b)) 748 { 749 next_w = w*a; 750 if ((next_w/a) != w) /* overflow */ 751 { 752 if (r_is_one) 753 { 754 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err; 755 r_is_one = 0; 756 } 757 else 758 { 759 if (!BN_MOD_MUL_WORD(r, w, m)) goto err; 760 } 761 next_w = a; 762 } 763 w = next_w; 764 } 765 } 766 767 /* Finally, set r:=r*w. */ 768 if (w != 1) 769 { 770 if (r_is_one) 771 { 772 if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err; 773 r_is_one = 0; 774 } 775 else 776 { 777 if (!BN_MOD_MUL_WORD(r, w, m)) goto err; 778 } 779 } 780 781 if (r_is_one) /* can happen only if a == 1*/ 782 { 783 if (!BN_one(rr)) goto err; 784 } 785 else 786 { 787 if (!BN_from_montgomery(rr, r, mont, ctx)) goto err; 788 } 789 ret = 1; 790err: 791 if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont); 792 BN_CTX_end(ctx); 793 return(ret); 794 } 795 796 797/* The old fallback, simple version :-) */ 798int BN_mod_exp_simple(BIGNUM *r, BIGNUM *a, BIGNUM *p, BIGNUM *m, 799 BN_CTX *ctx) 800 { 801 int i,j,bits,ret=0,wstart,wend,window,wvalue,ts=0; 802 int start=1; 803 BIGNUM *d; 804 BIGNUM val[TABLE_SIZE]; 805 806 bits=BN_num_bits(p); 807 808 if (bits == 0) 809 { 810 BN_one(r); 811 return(1); 812 } 813 814 BN_CTX_start(ctx); 815 if ((d = BN_CTX_get(ctx)) == NULL) goto err; 816 817 BN_init(&(val[0])); 818 ts=1; 819 if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */ 820 821 window = BN_window_bits_for_exponent_size(bits); 822 if (window > 1) 823 { 824 if (!BN_mod_mul(d,&(val[0]),&(val[0]),m,ctx)) 825 goto err; /* 2 */ 826 j=1<<(window-1); 827 for (i=1; i<j; i++) 828 { 829 BN_init(&(val[i])); 830 if (!BN_mod_mul(&(val[i]),&(val[i-1]),d,m,ctx)) 831 goto err; 832 } 833 ts=i; 834 } 835 836 start=1; /* This is used to avoid multiplication etc 837 * when there is only the value '1' in the 838 * buffer. */ 839 wvalue=0; /* The 'value' of the window */ 840 wstart=bits-1; /* The top bit of the window */ 841 wend=0; /* The bottom bit of the window */ 842 843 if (!BN_one(r)) goto err; 844 845 for (;;) 846 { 847 if (BN_is_bit_set(p,wstart) == 0) 848 { 849 if (!start) 850 if (!BN_mod_mul(r,r,r,m,ctx)) 851 goto err; 852 if (wstart == 0) break; 853 wstart--; 854 continue; 855 } 856 /* We now have wstart on a 'set' bit, we now need to work out 857 * how bit a window to do. To do this we need to scan 858 * forward until the last set bit before the end of the 859 * window */ 860 j=wstart; 861 wvalue=1; 862 wend=0; 863 for (i=1; i<window; i++) 864 { 865 if (wstart-i < 0) break; 866 if (BN_is_bit_set(p,wstart-i)) 867 { 868 wvalue<<=(i-wend); 869 wvalue|=1; 870 wend=i; 871 } 872 } 873 874 /* wend is the size of the current window */ 875 j=wend+1; 876 /* add the 'bytes above' */ 877 if (!start) 878 for (i=0; i<j; i++) 879 { 880 if (!BN_mod_mul(r,r,r,m,ctx)) 881 goto err; 882 } 883 884 /* wvalue will be an odd number < 2^window */ 885 if (!BN_mod_mul(r,r,&(val[wvalue>>1]),m,ctx)) 886 goto err; 887 888 /* move the 'window' down further */ 889 wstart-=wend+1; 890 wvalue=0; 891 start=0; 892 if (wstart < 0) break; 893 } 894 ret=1; 895err: 896 BN_CTX_end(ctx); 897 for (i=0; i<ts; i++) 898 BN_clear_free(&(val[i])); 899 return(ret); 900 } 901 902