crypto/engine/eng_rsax.c

   1 /* crypto/engine/eng_rsax.c */
   2 /* Copyright (c) 2010-2010 Intel Corp.
   3  *   Author: Vinodh.Gopal@intel.com
   4  *           Jim Guilford
   5  *           Erdinc.Ozturk@intel.com
   6  *           Maxim.Perminov@intel.com
   7  *           Ying.Huang@intel.com
   8  *
   9  * More information about algorithm used can be found at:
  10  *   http://www.cse.buffalo.edu/srds2009/escs2009_submission_Gopal.pdf
  11  */
  12 /* ====================================================================
  13  * Copyright (c) 1999-2001 The OpenSSL Project.  All rights reserved.
  14  *
  15  * Redistribution and use in source and binary forms, with or without
  16  * modification, are permitted provided that the following conditions
  17  * are met:
  18  *
  19  * 1. Redistributions of source code must retain the above copyright
  20  *    notice, this list of conditions and the following disclaimer.
  21  *
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in
  24  *    the documentation and/or other materials provided with the
  25  *    distribution.
  26  *
  27  * 3. All advertising materials mentioning features or use of this
  28  *    software must display the following acknowledgment:
  29  *    "This product includes software developed by the OpenSSL Project
  30  *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
  31  *
  32  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  33  *    endorse or promote products derived from this software without
  34  *    prior written permission. For written permission, please contact
  35  *    licensing@OpenSSL.org.
  36  *
  37  * 5. Products derived from this software may not be called "OpenSSL"
  38  *    nor may "OpenSSL" appear in their names without prior written
  39  *    permission of the OpenSSL Project.
  40  *
  41  * 6. Redistributions of any form whatsoever must retain the following
  42  *    acknowledgment:
  43  *    "This product includes software developed by the OpenSSL Project
  44  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
  45  *
  46  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  47  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  48  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  49  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  50  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  51  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  52  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  53  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  54  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  55  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  56  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  57  * OF THE POSSIBILITY OF SUCH DAMAGE.
  58  * ====================================================================
  59  *
  60  * This product includes cryptographic software written by Eric Young
  61  * (eay@cryptsoft.com).  This product includes software written by Tim
  62  * Hudson (tjh@cryptsoft.com).
  63  */
  64
  65 #include <openssl/opensslconf.h>
  66
  67 #include <stdio.h>
  68 #include <string.h>
  69 #include <openssl/crypto.h>
  70 #include <openssl/buffer.h>
  71 #include <openssl/engine.h>
  72 #ifndef OPENSSL_NO_RSA
  73 # include <openssl/rsa.h>
  74 #endif
  75 #include <openssl/bn.h>
  76 #include <openssl/err.h>
  77
  78 /* RSAX is available **ONLY* on x86_64 CPUs */
  79 #undef COMPILE_RSAX
  80
  81 #if (defined(__x86_64) || defined(__x86_64__) || \
  82      defined(_M_AMD64) || defined (_M_X64)) && !defined(OPENSSL_NO_ASM)
  83 # define COMPILE_RSAX
  84 static ENGINE *ENGINE_rsax(void);
  85 #endif
  86
  87 void ENGINE_load_rsax(void)
  88 {
  89 /* On non-x86 CPUs it just returns. */
  90 #ifdef COMPILE_RSAX
  91     ENGINE *toadd = ENGINE_rsax();
  92     if (!toadd)
  93         return;
  94     ENGINE_add(toadd);
  95     ENGINE_free(toadd);
  96     ERR_clear_error();
  97 #endif
  98 }
  99
 100 #ifdef COMPILE_RSAX
 101 # define E_RSAX_LIB_NAME "rsax engine"
 102
 103 static int e_rsax_destroy(ENGINE *e);
 104 static int e_rsax_init(ENGINE *e);
 105 static int e_rsax_finish(ENGINE *e);
 106 static int e_rsax_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f) (void));
 107
 108 # ifndef OPENSSL_NO_RSA
 109 /* RSA stuff */
 110 static int e_rsax_rsa_mod_exp(BIGNUM *r, const BIGNUM *I, RSA *rsa,
 111                               BN_CTX *ctx);
 112 static int e_rsax_rsa_finish(RSA *r);
 113 # endif
 114
 115 static const ENGINE_CMD_DEFN e_rsax_cmd_defns[] = {
 116     {0, NULL, NULL, 0}
 117 };
 118
 119 # ifndef OPENSSL_NO_RSA
 120 /* Our internal RSA_METHOD that we provide pointers to */
 121 static RSA_METHOD e_rsax_rsa = {
 122     "Intel RSA-X method",
 123     NULL,
 124     NULL,
 125     NULL,
 126     NULL,
 127     e_rsax_rsa_mod_exp,
 128     NULL,
 129     NULL,
 130     e_rsax_rsa_finish,
 131     RSA_FLAG_CACHE_PUBLIC | RSA_FLAG_CACHE_PRIVATE,
 132     NULL,
 133     NULL,
 134     NULL
 135 };
 136 # endif
 137
 138 /* Constants used when creating the ENGINE */
 139 static const char *engine_e_rsax_id = "rsax";
 140 static const char *engine_e_rsax_name = "RSAX engine support";
 141
 142 /* This internal function is used by ENGINE_rsax() */
 143 static int bind_helper(ENGINE *e)
 144 {
 145 # ifndef OPENSSL_NO_RSA
 146     const RSA_METHOD *meth1;
 147 # endif
 148     if (!ENGINE_set_id(e, engine_e_rsax_id) ||
 149         !ENGINE_set_name(e, engine_e_rsax_name) ||
 150 # ifndef OPENSSL_NO_RSA
 151         !ENGINE_set_RSA(e, &e_rsax_rsa) ||
 152 # endif
 153         !ENGINE_set_destroy_function(e, e_rsax_destroy) ||
 154         !ENGINE_set_init_function(e, e_rsax_init) ||
 155         !ENGINE_set_finish_function(e, e_rsax_finish) ||
 156         !ENGINE_set_ctrl_function(e, e_rsax_ctrl) ||
 157         !ENGINE_set_cmd_defns(e, e_rsax_cmd_defns))
 158         return 0;
 159
 160 # ifndef OPENSSL_NO_RSA
 161     meth1 = RSA_PKCS1_SSLeay();
 162     e_rsax_rsa.rsa_pub_enc = meth1->rsa_pub_enc;
 163     e_rsax_rsa.rsa_pub_dec = meth1->rsa_pub_dec;
 164     e_rsax_rsa.rsa_priv_enc = meth1->rsa_priv_enc;
 165     e_rsax_rsa.rsa_priv_dec = meth1->rsa_priv_dec;
 166     e_rsax_rsa.bn_mod_exp = meth1->bn_mod_exp;
 167 # endif
 168     return 1;
 169 }
 170
 171 static ENGINE *ENGINE_rsax(void)
 172 {
 173     ENGINE *ret = ENGINE_new();
 174     if (!ret)
 175         return NULL;
 176     if (!bind_helper(ret)) {
 177         ENGINE_free(ret);
 178         return NULL;
 179     }
 180     return ret;
 181 }
 182
 183 # ifndef OPENSSL_NO_RSA
 184 /* Used to attach our own key-data to an RSA structure */
 185 static int rsax_ex_data_idx = -1;
 186 # endif
 187
 188 static int e_rsax_destroy(ENGINE *e)
 189 {
 190     return 1;
 191 }
 192
 193 /* (de)initialisation functions. */
 194 static int e_rsax_init(ENGINE *e)
 195 {
 196 # ifndef OPENSSL_NO_RSA
 197     if (rsax_ex_data_idx == -1)
 198         rsax_ex_data_idx = RSA_get_ex_new_index(0, NULL, NULL, NULL, NULL);
 199 # endif
 200     if (rsax_ex_data_idx == -1)
 201         return 0;
 202     return 1;
 203 }
 204
 205 static int e_rsax_finish(ENGINE *e)
 206 {
 207     return 1;
 208 }
 209
 210 static int e_rsax_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f) (void))
 211 {
 212     int to_return = 1;
 213
 214     switch (cmd) {
 215         /* The command isn't understood by this engine */
 216     default:
 217         to_return = 0;
 218         break;
 219     }
 220
 221     return to_return;
 222 }
 223
 224 # ifndef OPENSSL_NO_RSA
 225
 226 #  ifdef _WIN32
 227 typedef unsigned __int64 UINT64;
 228 #  else
 229 typedef unsigned long long UINT64;
 230 #  endif
 231 typedef unsigned short UINT16;
 232
 233 /*
 234  * Table t is interleaved in the following manner: The order in memory is
 235  * t[0][0], t[0][1], ..., t[0][7], t[1][0], ... A particular 512-bit value is
 236  * stored in t[][index] rather than the more normal t[index][]; i.e. the
 237  * qwords of a particular entry in t are not adjacent in memory
 238  */
 239
 240 /* Init BIGNUM b from the interleaved UINT64 array */
 241 static int interleaved_array_to_bn_512(BIGNUM *b, UINT64 *array);
 242
 243 /*
 244  * Extract array elements from BIGNUM b To set the whole array from b, call
 245  * with n=8
 246  */
 247 static int bn_extract_to_array_512(const BIGNUM *b, unsigned int n,
 248                                    UINT64 *array);
 249
 250 struct mod_ctx_512 {
 251     UINT64 t[8][8];
 252     UINT64 m[8];
 253     UINT64 m1[8];               /* 2^278 % m */
 254     UINT64 m2[8];               /* 2^640 % m */
 255     UINT64 k1[2];               /* (- 1/m) % 2^128 */
 256 };
 257
 258 static int mod_exp_pre_compute_data_512(UINT64 *m, struct mod_ctx_512 *data);
 259
 260 void mod_exp_512(UINT64 *result, /* 512 bits, 8 qwords */
 261                  UINT64 *g,     /* 512 bits, 8 qwords */
 262                  UINT64 *exp,   /* 512 bits, 8 qwords */
 263                  struct mod_ctx_512 *data);
 264
 265 typedef struct st_e_rsax_mod_ctx {
 266     UINT64 type;
 267     union {
 268         struct mod_ctx_512 b512;
 269     } ctx;
 270
 271 } E_RSAX_MOD_CTX;
 272
 273 static E_RSAX_MOD_CTX *e_rsax_get_ctx(RSA *rsa, int idx, BIGNUM *m)
 274 {
 275     E_RSAX_MOD_CTX *hptr;
 276
 277     if (idx < 0 || idx > 2)
 278         return NULL;
 279
 280     hptr = RSA_get_ex_data(rsa, rsax_ex_data_idx);
 281     if (!hptr) {
 282         hptr = OPENSSL_malloc(3 * sizeof(E_RSAX_MOD_CTX));
 283         if (!hptr)
 284             return NULL;
 285         hptr[2].type = hptr[1].type = hptr[0].type = 0;
 286         RSA_set_ex_data(rsa, rsax_ex_data_idx, hptr);
 287     }
 288
 289     if (hptr[idx].type == (UINT64)BN_num_bits(m))
 290         return hptr + idx;
 291
 292     if (BN_num_bits(m) == 512) {
 293         UINT64 _m[8];
 294         bn_extract_to_array_512(m, 8, _m);
 295         memset(&hptr[idx].ctx.b512, 0, sizeof(struct mod_ctx_512));
 296         mod_exp_pre_compute_data_512(_m, &hptr[idx].ctx.b512);
 297     }
 298
 299     hptr[idx].type = BN_num_bits(m);
 300     return hptr + idx;
 301 }
 302
 303 static int e_rsax_rsa_finish(RSA *rsa)
 304 {
 305     E_RSAX_MOD_CTX *hptr = RSA_get_ex_data(rsa, rsax_ex_data_idx);
 306     if (hptr) {
 307         OPENSSL_free(hptr);
 308         RSA_set_ex_data(rsa, rsax_ex_data_idx, NULL);
 309     }
 310     if (rsa->_method_mod_n)
 311         BN_MONT_CTX_free(rsa->_method_mod_n);
 312     if (rsa->_method_mod_p)
 313         BN_MONT_CTX_free(rsa->_method_mod_p);
 314     if (rsa->_method_mod_q)
 315         BN_MONT_CTX_free(rsa->_method_mod_q);
 316     return 1;
 317 }
 318
 319 static int e_rsax_bn_mod_exp(BIGNUM *r, const BIGNUM *g, const BIGNUM *e,
 320                              const BIGNUM *m, BN_CTX *ctx,
 321                              BN_MONT_CTX *in_mont,
 322                              E_RSAX_MOD_CTX *rsax_mod_ctx)
 323 {
 324     if (rsax_mod_ctx && BN_get_flags(e, BN_FLG_CONSTTIME) != 0) {
 325         if (BN_num_bits(m) == 512) {
 326             UINT64 _r[8];
 327             UINT64 _g[8];
 328             UINT64 _e[8];
 329
 330             /* Init the arrays from the BIGNUMs */
 331             bn_extract_to_array_512(g, 8, _g);
 332             bn_extract_to_array_512(e, 8, _e);
 333
 334             mod_exp_512(_r, _g, _e, &rsax_mod_ctx->ctx.b512);
 335             /* Return the result in the BIGNUM */
 336             interleaved_array_to_bn_512(r, _r);
 337             return 1;
 338         }
 339     }
 340
 341     return BN_mod_exp_mont(r, g, e, m, ctx, in_mont);
 342 }
 343
 344 /*
 345  * Declares for the Intel CIAP 512-bit / CRT / 1024 bit RSA modular
 346  * exponentiation routine precalculations and a structure to hold the
 347  * necessary values.  These files are meant to live in crypto/rsa/ in the
 348  * target openssl.
 349  */
 350
 351 /*
 352  * Local method: extracts a piece from a BIGNUM, to fit it into
 353  * an array. Call with n=8 to extract an entire 512-bit BIGNUM
 354  */
 355 static int bn_extract_to_array_512(const BIGNUM *b, unsigned int n,
 356                                    UINT64 *array)
 357 {
 358     int i;
 359     UINT64 tmp;
 360     unsigned char bn_buff[64];
 361     memset(bn_buff, 0, 64);
 362     if (BN_num_bytes(b) > 64) {
 363         printf("Can't support this byte size\n");
 364         return 0;
 365     }
 366     if (BN_num_bytes(b) != 0) {
 367         if (!BN_bn2bin(b, bn_buff + (64 - BN_num_bytes(b)))) {
 368             printf("Error's in bn2bin\n");
 369             /* We have to error, here */
 370             return 0;
 371         }
 372     }
 373     while (n-- > 0) {
 374         array[n] = 0;
 375         for (i = 7; i >= 0; i--) {
 376             tmp = bn_buff[63 - (n * 8 + i)];
 377             array[n] |= tmp << (8 * i);
 378         }
 379     }
 380     return 1;
 381 }
 382
 383 /* Init a 512-bit BIGNUM from the UINT64*_ (8 * 64) interleaved array */
 384 static int interleaved_array_to_bn_512(BIGNUM *b, UINT64 *array)
 385 {
 386     unsigned char tmp[64];
 387     int n = 8;
 388     int i;
 389     while (n-- > 0) {
 390         for (i = 7; i >= 0; i--) {
 391             tmp[63 - (n * 8 + i)] = (unsigned char)(array[n] >> (8 * i));
 392     }}
 393     BN_bin2bn(tmp, 64, b);
 394     return 0;
 395 }
 396
 397 /* The main 512bit precompute call */
 398 static int mod_exp_pre_compute_data_512(UINT64 *m, struct mod_ctx_512 *data)
 399 {
 400     BIGNUM two_768, two_640, two_128, two_512, tmp, _m, tmp2;
 401
 402     /* We need a BN_CTX for the modulo functions */
 403     BN_CTX *ctx;
 404     /* Some tmps */
 405     UINT64 _t[8];
 406     int i, j, ret = 0;
 407
 408     /* Init _m with m */
 409     BN_init(&_m);
 410     interleaved_array_to_bn_512(&_m, m);
 411     memset(_t, 0, 64);
 412
 413     /* Inits */
 414     BN_init(&two_768);
 415     BN_init(&two_640);
 416     BN_init(&two_128);
 417     BN_init(&two_512);
 418     BN_init(&tmp);
 419     BN_init(&tmp2);
 420
 421     /* Create our context */
 422     if ((ctx = BN_CTX_new()) == NULL) {
 423         goto err;
 424     }
 425     BN_CTX_start(ctx);
 426
 427     /*
 428      * For production, if you care, these only need to be set once,
 429      * and may be made constants.
 430      */
 431     BN_lshift(&two_768, BN_value_one(), 768);
 432     BN_lshift(&two_640, BN_value_one(), 640);
 433     BN_lshift(&two_128, BN_value_one(), 128);
 434     BN_lshift(&two_512, BN_value_one(), 512);
 435
 436     if (0 == (m[7] & 0x8000000000000000)) {
 437         exit(1);
 438     }
 439     if (0 == (m[0] & 0x1)) {    /* Odd modulus required for Mont */
 440         exit(1);
 441     }
 442
 443     /* Precompute m1 */
 444     BN_mod(&tmp, &two_768, &_m, ctx);
 445     if (!bn_extract_to_array_512(&tmp, 8, &data->m1[0])) {
 446         goto err;
 447     }
 448
 449     /* Precompute m2 */
 450     BN_mod(&tmp, &two_640, &_m, ctx);
 451     if (!bn_extract_to_array_512(&tmp, 8, &data->m2[0])) {
 452         goto err;
 453     }
 454
 455     /*
 456      * Precompute k1, a 128b number = ((-1)* m-1 ) mod 2128; k1 should
 457      * be non-negative.
 458      */
 459     BN_mod_inverse(&tmp, &_m, &two_128, ctx);
 460     if (!BN_is_zero(&tmp)) {
 461         BN_sub(&tmp, &two_128, &tmp);
 462     }
 463     if (!bn_extract_to_array_512(&tmp, 2, &data->k1[0])) {
 464         goto err;
 465     }
 466
 467     /* Precompute t */
 468     for (i = 0; i < 8; i++) {
 469         BN_zero(&tmp);
 470         if (i & 1) {
 471             BN_add(&tmp, &two_512, &tmp);
 472         }
 473         if (i & 2) {
 474             BN_add(&tmp, &two_512, &tmp);
 475         }
 476         if (i & 4) {
 477             BN_add(&tmp, &two_640, &tmp);
 478         }
 479
 480         BN_nnmod(&tmp2, &tmp, &_m, ctx);
 481         if (!bn_extract_to_array_512(&tmp2, 8, _t)) {
 482             goto err;
 483         }
 484         for (j = 0; j < 8; j++)
 485             data->t[j][i] = _t[j];
 486     }
 487
 488     /* Precompute m */
 489     for (i = 0; i < 8; i++) {
 490         data->m[i] = m[i];
 491     }
 492
 493     ret = 1;
 494
 495  err:
 496     /* Cleanup */
 497     if (ctx != NULL) {
 498         BN_CTX_end(ctx);
 499         BN_CTX_free(ctx);
 500     }
 501     BN_free(&two_768);
 502     BN_free(&two_640);
 503     BN_free(&two_128);
 504     BN_free(&two_512);
 505     BN_free(&tmp);
 506     BN_free(&tmp2);
 507     BN_free(&_m);
 508
 509     return ret;
 510 }
 511
 512 static int e_rsax_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa,
 513                               BN_CTX *ctx)
 514 {
 515     BIGNUM *r1, *m1, *vrfy;
 516     BIGNUM local_dmp1, local_dmq1, local_c, local_r1;
 517     BIGNUM *dmp1, *dmq1, *c, *pr1;
 518     int ret = 0;
 519
 520     BN_CTX_start(ctx);
 521     r1 = BN_CTX_get(ctx);
 522     m1 = BN_CTX_get(ctx);
 523     vrfy = BN_CTX_get(ctx);
 524
 525     {
 526         BIGNUM local_p, local_q;
 527         BIGNUM *p = NULL, *q = NULL;
 528         int error = 0;
 529
 530         /*
 531          * Make sure BN_mod_inverse in Montgomery intialization uses the
 532          * BN_FLG_CONSTTIME flag (unless RSA_FLAG_NO_CONSTTIME is set)
 533          */
 534         if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME)) {
 535             BN_init(&local_p);
 536             p = &local_p;
 537             BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);
 538
 539             BN_init(&local_q);
 540             q = &local_q;
 541             BN_with_flags(q, rsa->q, BN_FLG_CONSTTIME);
 542         } else {
 543             p = rsa->p;
 544             q = rsa->q;
 545         }
 546
 547         if (rsa->flags & RSA_FLAG_CACHE_PRIVATE) {
 548             if (!BN_MONT_CTX_set_locked
 549                 (&rsa->_method_mod_p, CRYPTO_LOCK_RSA, p, ctx))
 550                 error = 1;
 551             if (!BN_MONT_CTX_set_locked
 552                 (&rsa->_method_mod_q, CRYPTO_LOCK_RSA, q, ctx))
 553                 error = 1;
 554         }
 555
 556         /* clean up */
 557         if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME)) {
 558             BN_free(&local_p);
 559             BN_free(&local_q);
 560         }
 561         if (error)
 562             goto err;
 563     }
 564
 565     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 566         if (!BN_MONT_CTX_set_locked
 567             (&rsa->_method_mod_n, CRYPTO_LOCK_RSA, rsa->n, ctx))
 568             goto err;
 569
 570     /* compute I mod q */
 571     if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME)) {
 572         c = &local_c;
 573         BN_with_flags(c, I, BN_FLG_CONSTTIME);
 574         if (!BN_mod(r1, c, rsa->q, ctx))
 575             goto err;
 576     } else {
 577         if (!BN_mod(r1, I, rsa->q, ctx))
 578             goto err;
 579     }
 580
 581     /* compute r1^dmq1 mod q */
 582     if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME)) {
 583         dmq1 = &local_dmq1;
 584         BN_with_flags(dmq1, rsa->dmq1, BN_FLG_CONSTTIME);
 585     } else
 586         dmq1 = rsa->dmq1;
 587
 588     if (!e_rsax_bn_mod_exp(m1, r1, dmq1, rsa->q, ctx,
 589                            rsa->_method_mod_q, e_rsax_get_ctx(rsa, 0,
 590                                                               rsa->q)))
 591         goto err;
 592
 593     /* compute I mod p */
 594     if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME)) {
 595         c = &local_c;
 596         BN_with_flags(c, I, BN_FLG_CONSTTIME);
 597         if (!BN_mod(r1, c, rsa->p, ctx))
 598             goto err;
 599     } else {
 600         if (!BN_mod(r1, I, rsa->p, ctx))
 601             goto err;
 602     }
 603
 604     /* compute r1^dmp1 mod p */
 605     if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME)) {
 606         dmp1 = &local_dmp1;
 607         BN_with_flags(dmp1, rsa->dmp1, BN_FLG_CONSTTIME);
 608     } else
 609         dmp1 = rsa->dmp1;
 610
 611     if (!e_rsax_bn_mod_exp(r0, r1, dmp1, rsa->p, ctx,
 612                            rsa->_method_mod_p, e_rsax_get_ctx(rsa, 1,
 613                                                               rsa->p)))
 614         goto err;
 615
 616     if (!BN_sub(r0, r0, m1))
 617         goto err;
 618     /*
 619      * This will help stop the size of r0 increasing, which does affect the
 620      * multiply if it optimised for a power of 2 size
 621      */
 622     if (BN_is_negative(r0))
 623         if (!BN_add(r0, r0, rsa->p))
 624             goto err;
 625
 626     if (!BN_mul(r1, r0, rsa->iqmp, ctx))
 627         goto err;
 628
 629     /* Turn BN_FLG_CONSTTIME flag on before division operation */
 630     if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME)) {
 631         pr1 = &local_r1;
 632         BN_with_flags(pr1, r1, BN_FLG_CONSTTIME);
 633     } else
 634         pr1 = r1;
 635     if (!BN_mod(r0, pr1, rsa->p, ctx))
 636         goto err;
 637
 638     /*
 639      * If p < q it is occasionally possible for the correction of adding 'p'
 640      * if r0 is negative above to leave the result still negative. This can
 641      * break the private key operations: the following second correction
 642      * should *always* correct this rare occurrence. This will *never* happen
 643      * with OpenSSL generated keys because they ensure p > q [steve]
 644      */
 645     if (BN_is_negative(r0))
 646         if (!BN_add(r0, r0, rsa->p))
 647             goto err;
 648     if (!BN_mul(r1, r0, rsa->q, ctx))
 649         goto err;
 650     if (!BN_add(r0, r1, m1))
 651         goto err;
 652
 653     if (rsa->e && rsa->n) {
 654         if (!e_rsax_bn_mod_exp
 655             (vrfy, r0, rsa->e, rsa->n, ctx, rsa->_method_mod_n,
 656              e_rsax_get_ctx(rsa, 2, rsa->n)))
 657             goto err;
 658
 659         /*
 660          * If 'I' was greater than (or equal to) rsa->n, the operation will
 661          * be equivalent to using 'I mod n'. However, the result of the
 662          * verify will *always* be less than 'n' so we don't check for
 663          * absolute equality, just congruency.
 664          */
 665         if (!BN_sub(vrfy, vrfy, I))
 666             goto err;
 667         if (!BN_mod(vrfy, vrfy, rsa->n, ctx))
 668             goto err;
 669         if (BN_is_negative(vrfy))
 670             if (!BN_add(vrfy, vrfy, rsa->n))
 671                 goto err;
 672         if (!BN_is_zero(vrfy)) {
 673             /*
 674              * 'I' and 'vrfy' aren't congruent mod n. Don't leak
 675              * miscalculated CRT output, just do a raw (slower) mod_exp and
 676              * return that instead.
 677              */
 678
 679             BIGNUM local_d;
 680             BIGNUM *d = NULL;
 681
 682             if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME)) {
 683                 d = &local_d;
 684                 BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 685             } else
 686                 d = rsa->d;
 687             if (!e_rsax_bn_mod_exp(r0, I, d, rsa->n, ctx,
 688                                    rsa->_method_mod_n, e_rsax_get_ctx(rsa, 2,
 689                                                                       rsa->n)))
 690                 goto err;
 691         }
 692     }
 693     ret = 1;
 694
 695  err:
 696     BN_CTX_end(ctx);
 697
 698     return ret;
 699 }
 700 # endif                         /* !OPENSSL_NO_RSA */
 701 #endif                          /* !COMPILE_RSAX */