crypto/dsa/dsa_gen.c

   1 /* crypto/dsa/dsa_gen.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 #undef GENUINE_DSA
  60
  61 #ifdef GENUINE_DSA
  62 /*
  63  * Parameter generation follows the original release of FIPS PUB 186,
  64  * Appendix 2.2 (i.e. use SHA as defined in FIPS PUB 180)
  65  */
  66 # define HASH    EVP_sha()
  67 #else
  68 /*
  69  * Parameter generation follows the updated Appendix 2.2 for FIPS PUB 186,
  70  * also Appendix 2.2 of FIPS PUB 186-1 (i.e. use SHA as defined in FIPS PUB
  71  * 180-1)
  72  */
  73 # define HASH    EVP_sha1()
  74 #endif
  75
  76 #include <openssl/opensslconf.h> /* To see if OPENSSL_NO_SHA is defined */
  77
  78 #ifndef OPENSSL_NO_SHA
  79
  80 # include <stdio.h>
  81 # include "cryptlib.h"
  82 # include <openssl/evp.h>
  83 # include <openssl/bn.h>
  84 # include <openssl/rand.h>
  85 # include <openssl/sha.h>
  86
  87 # include "dsa_locl.h"
  88
  89 int DSA_generate_parameters_ex(DSA *ret, int bits,
  90                                const unsigned char *seed_in, int seed_len,
  91                                int *counter_ret, unsigned long *h_ret,
  92                                BN_GENCB *cb)
  93 {
  94     if (ret->meth->dsa_paramgen)
  95         return ret->meth->dsa_paramgen(ret, bits, seed_in, seed_len,
  96                                        counter_ret, h_ret, cb);
  97     else {
  98         const EVP_MD *evpmd;
  99         size_t qbits = bits >= 2048 ? 256 : 160;
 100
 101         if (bits >= 2048) {
 102             qbits = 256;
 103             evpmd = EVP_sha256();
 104         } else {
 105             qbits = 160;
 106             evpmd = EVP_sha1();
 107         }
 108
 109         return dsa_builtin_paramgen(ret, bits, qbits, evpmd,
 110                                     seed_in, seed_len, NULL, counter_ret,
 111                                     h_ret, cb);
 112     }
 113 }
 114
 115 int dsa_builtin_paramgen(DSA *ret, size_t bits, size_t qbits,
 116                          const EVP_MD *evpmd, const unsigned char *seed_in,
 117                          size_t seed_len, unsigned char *seed_out,
 118                          int *counter_ret, unsigned long *h_ret, BN_GENCB *cb)
 119 {
 120     int ok = 0;
 121     unsigned char seed[SHA256_DIGEST_LENGTH];
 122     unsigned char md[SHA256_DIGEST_LENGTH];
 123     unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH];
 124     BIGNUM *r0, *W, *X, *c, *test;
 125     BIGNUM *g = NULL, *q = NULL, *p = NULL;
 126     BN_MONT_CTX *mont = NULL;
 127     int i, k, n = 0, m = 0, qsize = qbits >> 3;
 128     int counter = 0;
 129     int r = 0;
 130     BN_CTX *ctx = NULL;
 131     unsigned int h = 2;
 132
 133     if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH &&
 134         qsize != SHA256_DIGEST_LENGTH)
 135         /* invalid q size */
 136         return 0;
 137
 138     if (evpmd == NULL)
 139         /* use SHA1 as default */
 140         evpmd = EVP_sha1();
 141
 142     if (bits < 512)
 143         bits = 512;
 144
 145     bits = (bits + 63) / 64 * 64;
 146
 147     /*
 148      * NB: seed_len == 0 is special case: copy generated seed to seed_in if
 149      * it is not NULL.
 150      */
 151     if (seed_len && (seed_len < (size_t)qsize))
 152         seed_in = NULL;         /* seed buffer too small -- ignore */
 153     if (seed_len > (size_t)qsize)
 154         seed_len = qsize;       /* App. 2.2 of FIPS PUB 186 allows larger
 155                                  * SEED, but our internal buffers are
 156                                  * restricted to 160 bits */
 157     if (seed_in != NULL)
 158         memcpy(seed, seed_in, seed_len);
 159
 160     if ((ctx = BN_CTX_new()) == NULL)
 161         goto err;
 162
 163     if ((mont = BN_MONT_CTX_new()) == NULL)
 164         goto err;
 165
 166     BN_CTX_start(ctx);
 167     r0 = BN_CTX_get(ctx);
 168     g = BN_CTX_get(ctx);
 169     W = BN_CTX_get(ctx);
 170     q = BN_CTX_get(ctx);
 171     X = BN_CTX_get(ctx);
 172     c = BN_CTX_get(ctx);
 173     p = BN_CTX_get(ctx);
 174     test = BN_CTX_get(ctx);
 175
 176     if (!BN_lshift(test, BN_value_one(), bits - 1))
 177         goto err;
 178
 179     for (;;) {
 180         for (;;) {              /* find q */
 181             int seed_is_random;
 182
 183             /* step 1 */
 184             if (!BN_GENCB_call(cb, 0, m++))
 185                 goto err;
 186
 187             if (!seed_len) {
 188                 if (RAND_pseudo_bytes(seed, qsize) < 0)
 189                     goto err;
 190                 seed_is_random = 1;
 191             } else {
 192                 seed_is_random = 0;
 193                 seed_len = 0;   /* use random seed if 'seed_in' turns out to
 194                                  * be bad */
 195             }
 196             memcpy(buf, seed, qsize);
 197             memcpy(buf2, seed, qsize);
 198             /* precompute "SEED + 1" for step 7: */
 199             for (i = qsize - 1; i >= 0; i--) {
 200                 buf[i]++;
 201                 if (buf[i] != 0)
 202                     break;
 203             }
 204
 205             /* step 2 */
 206             if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL))
 207                 goto err;
 208             if (!EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL))
 209                 goto err;
 210             for (i = 0; i < qsize; i++)
 211                 md[i] ^= buf2[i];
 212
 213             /* step 3 */
 214             md[0] |= 0x80;
 215             md[qsize - 1] |= 0x01;
 216             if (!BN_bin2bn(md, qsize, q))
 217                 goto err;
 218
 219             /* step 4 */
 220             r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx,
 221                                         seed_is_random, cb);
 222             if (r > 0)
 223                 break;
 224             if (r != 0)
 225                 goto err;
 226
 227             /* do a callback call */
 228             /* step 5 */
 229         }
 230
 231         if (!BN_GENCB_call(cb, 2, 0))
 232             goto err;
 233         if (!BN_GENCB_call(cb, 3, 0))
 234             goto err;
 235
 236         /* step 6 */
 237         counter = 0;
 238         /* "offset = 2" */
 239
 240         n = (bits - 1) / 160;
 241
 242         for (;;) {
 243             if ((counter != 0) && !BN_GENCB_call(cb, 0, counter))
 244                 goto err;
 245
 246             /* step 7 */
 247             BN_zero(W);
 248             /* now 'buf' contains "SEED + offset - 1" */
 249             for (k = 0; k <= n; k++) {
 250                 /*
 251                  * obtain "SEED + offset + k" by incrementing:
 252                  */
 253                 for (i = qsize - 1; i >= 0; i--) {
 254                     buf[i]++;
 255                     if (buf[i] != 0)
 256                         break;
 257                 }
 258
 259                 if (!EVP_Digest(buf, qsize, md, NULL, evpmd, NULL))
 260                     goto err;
 261
 262                 /* step 8 */
 263                 if (!BN_bin2bn(md, qsize, r0))
 264                     goto err;
 265                 if (!BN_lshift(r0, r0, (qsize << 3) * k))
 266                     goto err;
 267                 if (!BN_add(W, W, r0))
 268                     goto err;
 269             }
 270
 271             /* more of step 8 */
 272             if (!BN_mask_bits(W, bits - 1))
 273                 goto err;
 274             if (!BN_copy(X, W))
 275                 goto err;
 276             if (!BN_add(X, X, test))
 277                 goto err;
 278
 279             /* step 9 */
 280             if (!BN_lshift1(r0, q))
 281                 goto err;
 282             if (!BN_mod(c, X, r0, ctx))
 283                 goto err;
 284             if (!BN_sub(r0, c, BN_value_one()))
 285                 goto err;
 286             if (!BN_sub(p, X, r0))
 287                 goto err;
 288
 289             /* step 10 */
 290             if (BN_cmp(p, test) >= 0) {
 291                 /* step 11 */
 292                 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, ctx, 1, cb);
 293                 if (r > 0)
 294                     goto end;   /* found it */
 295                 if (r != 0)
 296                     goto err;
 297             }
 298
 299             /* step 13 */
 300             counter++;
 301             /* "offset = offset + n + 1" */
 302
 303             /* step 14 */
 304             if (counter >= 4096)
 305                 break;
 306         }
 307     }
 308  end:
 309     if (!BN_GENCB_call(cb, 2, 1))
 310         goto err;
 311
 312     /* We now need to generate g */
 313     /* Set r0=(p-1)/q */
 314     if (!BN_sub(test, p, BN_value_one()))
 315         goto err;
 316     if (!BN_div(r0, NULL, test, q, ctx))
 317         goto err;
 318
 319     if (!BN_set_word(test, h))
 320         goto err;
 321     if (!BN_MONT_CTX_set(mont, p, ctx))
 322         goto err;
 323
 324     for (;;) {
 325         /* g=test^r0%p */
 326         if (!BN_mod_exp_mont(g, test, r0, p, ctx, mont))
 327             goto err;
 328         if (!BN_is_one(g))
 329             break;
 330         if (!BN_add(test, test, BN_value_one()))
 331             goto err;
 332         h++;
 333     }
 334
 335     if (!BN_GENCB_call(cb, 3, 1))
 336         goto err;
 337
 338     ok = 1;
 339  err:
 340     if (ok) {
 341         if (ret->p)
 342             BN_free(ret->p);
 343         if (ret->q)
 344             BN_free(ret->q);
 345         if (ret->g)
 346             BN_free(ret->g);
 347         ret->p = BN_dup(p);
 348         ret->q = BN_dup(q);
 349         ret->g = BN_dup(g);
 350         if (ret->p == NULL || ret->q == NULL || ret->g == NULL) {
 351             ok = 0;
 352             goto err;
 353         }
 354         if (counter_ret != NULL)
 355             *counter_ret = counter;
 356         if (h_ret != NULL)
 357             *h_ret = h;
 358         if (seed_out)
 359             memcpy(seed_out, seed, qsize);
 360     }
 361     if (ctx) {
 362         BN_CTX_end(ctx);
 363         BN_CTX_free(ctx);
 364     }
 365     if (mont != NULL)
 366         BN_MONT_CTX_free(mont);
 367     return ok;
 368 }
 369
 370 /*
 371  * This is a parameter generation algorithm for the DSA2 algorithm as
 372  * described in FIPS 186-3.
 373  */
 374
 375 int dsa_builtin_paramgen2(DSA *ret, size_t L, size_t N,
 376                           const EVP_MD *evpmd, const unsigned char *seed_in,
 377                           size_t seed_len, int idx, unsigned char *seed_out,
 378                           int *counter_ret, unsigned long *h_ret,
 379                           BN_GENCB *cb)
 380 {
 381     int ok = -1;
 382     unsigned char *seed = NULL, *seed_tmp = NULL;
 383     unsigned char md[EVP_MAX_MD_SIZE];
 384     int mdsize;
 385     BIGNUM *r0, *W, *X, *c, *test;
 386     BIGNUM *g = NULL, *q = NULL, *p = NULL;
 387     BN_MONT_CTX *mont = NULL;
 388     int i, k, n = 0, m = 0, qsize = N >> 3;
 389     int counter = 0;
 390     int r = 0;
 391     BN_CTX *ctx = NULL;
 392     EVP_MD_CTX mctx;
 393     unsigned int h = 2;
 394
 395     EVP_MD_CTX_init(&mctx);
 396
 397     if (evpmd == NULL) {
 398         if (N == 160)
 399             evpmd = EVP_sha1();
 400         else if (N == 224)
 401             evpmd = EVP_sha224();
 402         else
 403             evpmd = EVP_sha256();
 404     }
 405
 406     mdsize = M_EVP_MD_size(evpmd);
 407     /* If unverificable g generation only don't need seed */
 408     if (!ret->p || !ret->q || idx >= 0) {
 409         if (seed_len == 0)
 410             seed_len = mdsize;
 411
 412         seed = OPENSSL_malloc(seed_len);
 413
 414         if (seed_out)
 415             seed_tmp = seed_out;
 416         else
 417             seed_tmp = OPENSSL_malloc(seed_len);
 418
 419         if (!seed || !seed_tmp)
 420             goto err;
 421
 422         if (seed_in)
 423             memcpy(seed, seed_in, seed_len);
 424
 425     }
 426
 427     if ((ctx = BN_CTX_new()) == NULL)
 428         goto err;
 429
 430     if ((mont = BN_MONT_CTX_new()) == NULL)
 431         goto err;
 432
 433     BN_CTX_start(ctx);
 434     r0 = BN_CTX_get(ctx);
 435     g = BN_CTX_get(ctx);
 436     W = BN_CTX_get(ctx);
 437     X = BN_CTX_get(ctx);
 438     c = BN_CTX_get(ctx);
 439     test = BN_CTX_get(ctx);
 440
 441     /* if p, q already supplied generate g only */
 442     if (ret->p && ret->q) {
 443         p = ret->p;
 444         q = ret->q;
 445         if (idx >= 0)
 446             memcpy(seed_tmp, seed, seed_len);
 447         goto g_only;
 448     } else {
 449         p = BN_CTX_get(ctx);
 450         q = BN_CTX_get(ctx);
 451     }
 452
 453     if (!BN_lshift(test, BN_value_one(), L - 1))
 454         goto err;
 455     for (;;) {
 456         for (;;) {              /* find q */
 457             unsigned char *pmd;
 458             /* step 1 */
 459             if (!BN_GENCB_call(cb, 0, m++))
 460                 goto err;
 461
 462             if (!seed_in) {
 463                 if (RAND_pseudo_bytes(seed, seed_len) < 0)
 464                     goto err;
 465             }
 466             /* step 2 */
 467             if (!EVP_Digest(seed, seed_len, md, NULL, evpmd, NULL))
 468                 goto err;
 469             /* Take least significant bits of md */
 470             if (mdsize > qsize)
 471                 pmd = md + mdsize - qsize;
 472             else
 473                 pmd = md;
 474
 475             if (mdsize < qsize)
 476                 memset(md + mdsize, 0, qsize - mdsize);
 477
 478             /* step 3 */
 479             pmd[0] |= 0x80;
 480             pmd[qsize - 1] |= 0x01;
 481             if (!BN_bin2bn(pmd, qsize, q))
 482                 goto err;
 483
 484             /* step 4 */
 485             r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx,
 486                                         seed_in ? 1 : 0, cb);
 487             if (r > 0)
 488                 break;
 489             if (r != 0)
 490                 goto err;
 491             /* Provided seed didn't produce a prime: error */
 492             if (seed_in) {
 493                 ok = 0;
 494                 DSAerr(DSA_F_DSA_BUILTIN_PARAMGEN2, DSA_R_Q_NOT_PRIME);
 495                 goto err;
 496             }
 497
 498             /* do a callback call */
 499             /* step 5 */
 500         }
 501         /* Copy seed to seed_out before we mess with it */
 502         if (seed_out)
 503             memcpy(seed_out, seed, seed_len);
 504
 505         if (!BN_GENCB_call(cb, 2, 0))
 506             goto err;
 507         if (!BN_GENCB_call(cb, 3, 0))
 508             goto err;
 509
 510         /* step 6 */
 511         counter = 0;
 512         /* "offset = 1" */
 513
 514         n = (L - 1) / (mdsize << 3);
 515
 516         for (;;) {
 517             if ((counter != 0) && !BN_GENCB_call(cb, 0, counter))
 518                 goto err;
 519
 520             /* step 7 */
 521             BN_zero(W);
 522             /* now 'buf' contains "SEED + offset - 1" */
 523             for (k = 0; k <= n; k++) {
 524                 /*
 525                  * obtain "SEED + offset + k" by incrementing:
 526                  */
 527                 for (i = seed_len - 1; i >= 0; i--) {
 528                     seed[i]++;
 529                     if (seed[i] != 0)
 530                         break;
 531                 }
 532
 533                 if (!EVP_Digest(seed, seed_len, md, NULL, evpmd, NULL))
 534                     goto err;
 535
 536                 /* step 8 */
 537                 if (!BN_bin2bn(md, mdsize, r0))
 538                     goto err;
 539                 if (!BN_lshift(r0, r0, (mdsize << 3) * k))
 540                     goto err;
 541                 if (!BN_add(W, W, r0))
 542                     goto err;
 543             }
 544
 545             /* more of step 8 */
 546             if (!BN_mask_bits(W, L - 1))
 547                 goto err;
 548             if (!BN_copy(X, W))
 549                 goto err;
 550             if (!BN_add(X, X, test))
 551                 goto err;
 552
 553             /* step 9 */
 554             if (!BN_lshift1(r0, q))
 555                 goto err;
 556             if (!BN_mod(c, X, r0, ctx))
 557                 goto err;
 558             if (!BN_sub(r0, c, BN_value_one()))
 559                 goto err;
 560             if (!BN_sub(p, X, r0))
 561                 goto err;
 562
 563             /* step 10 */
 564             if (BN_cmp(p, test) >= 0) {
 565                 /* step 11 */
 566                 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, ctx, 1, cb);
 567                 if (r > 0)
 568                     goto end;   /* found it */
 569                 if (r != 0)
 570                     goto err;
 571             }
 572
 573             /* step 13 */
 574             counter++;
 575             /* "offset = offset + n + 1" */
 576
 577             /* step 14 */
 578             if (counter >= (int)(4 * L))
 579                 break;
 580         }
 581         if (seed_in) {
 582             ok = 0;
 583             DSAerr(DSA_F_DSA_BUILTIN_PARAMGEN2, DSA_R_INVALID_PARAMETERS);
 584             goto err;
 585         }
 586     }
 587  end:
 588     if (!BN_GENCB_call(cb, 2, 1))
 589         goto err;
 590
 591  g_only:
 592
 593     /* We now need to generate g */
 594     /* Set r0=(p-1)/q */
 595     if (!BN_sub(test, p, BN_value_one()))
 596         goto err;
 597     if (!BN_div(r0, NULL, test, q, ctx))
 598         goto err;
 599
 600     if (idx < 0) {
 601         if (!BN_set_word(test, h))
 602             goto err;
 603     } else
 604         h = 1;
 605     if (!BN_MONT_CTX_set(mont, p, ctx))
 606         goto err;
 607
 608     for (;;) {
 609         static const unsigned char ggen[4] = { 0x67, 0x67, 0x65, 0x6e };
 610         if (idx >= 0) {
 611             md[0] = idx & 0xff;
 612             md[1] = (h >> 8) & 0xff;
 613             md[2] = h & 0xff;
 614             if (!EVP_DigestInit_ex(&mctx, evpmd, NULL))
 615                 goto err;
 616             if (!EVP_DigestUpdate(&mctx, seed_tmp, seed_len))
 617                 goto err;
 618             if (!EVP_DigestUpdate(&mctx, ggen, sizeof(ggen)))
 619                 goto err;
 620             if (!EVP_DigestUpdate(&mctx, md, 3))
 621                 goto err;
 622             if (!EVP_DigestFinal_ex(&mctx, md, NULL))
 623                 goto err;
 624             if (!BN_bin2bn(md, mdsize, test))
 625                 goto err;
 626         }
 627         /* g=test^r0%p */
 628         if (!BN_mod_exp_mont(g, test, r0, p, ctx, mont))
 629             goto err;
 630         if (!BN_is_one(g))
 631             break;
 632         if (idx < 0 && !BN_add(test, test, BN_value_one()))
 633             goto err;
 634         h++;
 635         if (idx >= 0 && h > 0xffff)
 636             goto err;
 637     }
 638
 639     if (!BN_GENCB_call(cb, 3, 1))
 640         goto err;
 641
 642     ok = 1;
 643  err:
 644     if (ok == 1) {
 645         if (p != ret->p) {
 646             if (ret->p)
 647                 BN_free(ret->p);
 648             ret->p = BN_dup(p);
 649         }
 650         if (q != ret->q) {
 651             if (ret->q)
 652                 BN_free(ret->q);
 653             ret->q = BN_dup(q);
 654         }
 655         if (ret->g)
 656             BN_free(ret->g);
 657         ret->g = BN_dup(g);
 658         if (ret->p == NULL || ret->q == NULL || ret->g == NULL) {
 659             ok = -1;
 660             goto err;
 661         }
 662         if (counter_ret != NULL)
 663             *counter_ret = counter;
 664         if (h_ret != NULL)
 665             *h_ret = h;
 666     }
 667     if (seed)
 668         OPENSSL_free(seed);
 669     if (seed_out != seed_tmp)
 670         OPENSSL_free(seed_tmp);
 671     if (ctx) {
 672         BN_CTX_end(ctx);
 673         BN_CTX_free(ctx);
 674     }
 675     if (mont != NULL)
 676         BN_MONT_CTX_free(mont);
 677     EVP_MD_CTX_cleanup(&mctx);
 678     return ok;
 679 }
 680
 681 int dsa_paramgen_check_g(DSA *dsa)
 682 {
 683     BN_CTX *ctx;
 684     BIGNUM *tmp;
 685     BN_MONT_CTX *mont = NULL;
 686     int rv = -1;
 687     ctx = BN_CTX_new();
 688     if (!ctx)
 689         return -1;
 690     BN_CTX_start(ctx);
 691     if (BN_cmp(dsa->g, BN_value_one()) <= 0)
 692         return 0;
 693     if (BN_cmp(dsa->g, dsa->p) >= 0)
 694         return 0;
 695     tmp = BN_CTX_get(ctx);
 696     if (!tmp)
 697         goto err;
 698     if ((mont = BN_MONT_CTX_new()) == NULL)
 699         goto err;
 700     if (!BN_MONT_CTX_set(mont, dsa->p, ctx))
 701         goto err;
 702     /* Work out g^q mod p */
 703     if (!BN_mod_exp_mont(tmp, dsa->g, dsa->q, dsa->p, ctx, mont))
 704         goto err;
 705     if (!BN_cmp(tmp, BN_value_one()))
 706         rv = 1;
 707     else
 708         rv = 0;
 709  err:
 710     BN_CTX_end(ctx);
 711     if (mont)
 712         BN_MONT_CTX_free(mont);
 713     BN_CTX_free(ctx);
 714     return rv;
 715
 716 }
 717
 718 #endif