Add FIPS 186-2 DSA parameter generation algorithm.
[openssl.git] / 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
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30  *    documentation and/or other materials provided with the distribution.
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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 :-).
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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
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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.
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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 /* Parameter generation follows the original release of FIPS PUB 186,
63  * Appendix 2.2 (i.e. use SHA as defined in FIPS PUB 180) */
64 #define HASH    EVP_sha()
65 #else
66 /* Parameter generation follows the updated Appendix 2.2 for FIPS PUB 186,
67  * also Appendix 2.2 of FIPS PUB 186-1 (i.e. use SHA as defined in
68  * FIPS PUB 180-1) */
69 #define HASH    EVP_sha1()
70 #endif 
71
72 #include <openssl/opensslconf.h> /* To see if OPENSSL_NO_SHA is defined */
73
74 #ifndef OPENSSL_NO_SHA
75
76 #include <stdio.h>
77 #include "cryptlib.h"
78 #include <openssl/evp.h>
79 #include <openssl/bn.h>
80 #include <openssl/rand.h>
81 #include <openssl/sha.h>
82 #include "dsa_locl.h"
83
84 #ifdef OPENSSL_FIPS
85 /* Workaround bug in prototype */
86 #define fips_dsa_builtin_paramgen2 fips_dsa_paramgen_bad
87 #include <openssl/fips.h>
88 #endif
89
90 int DSA_generate_parameters_ex(DSA *ret, int bits,
91                 const unsigned char *seed_in, int seed_len,
92                 int *counter_ret, unsigned long *h_ret, BN_GENCB *cb)
93         {
94 #ifdef OPENSSL_FIPS
95         if (FIPS_mode() && !(ret->meth->flags & DSA_FLAG_FIPS_METHOD)
96                         && !(ret->flags & DSA_FLAG_NON_FIPS_ALLOW))
97                 {
98                 DSAerr(DSA_F_DSA_GENERATE_PARAMETERS_EX, DSA_R_NON_FIPS_DSA_METHOD);
99                 return 0;
100                 }
101 #endif
102         if(ret->meth->dsa_paramgen)
103                 return ret->meth->dsa_paramgen(ret, bits, seed_in, seed_len,
104                                 counter_ret, h_ret, cb);
105 #ifdef OPENSSL_FIPS
106         else if (FIPS_mode())
107                 {
108                 return FIPS_dsa_generate_parameters_ex(ret, bits, 
109                                                         seed_in, seed_len,
110                                                         counter_ret, h_ret, cb);
111                 }
112 #endif
113         else
114                 {
115                 const EVP_MD *evpmd;
116                 size_t qbits = bits >= 2048 ? 256 : 160;
117
118                 if (bits >= 2048)
119                         {
120                         qbits = 256;
121                         evpmd = EVP_sha256();
122                         }
123                 else
124                         {
125                         qbits = 160;
126                         evpmd = EVP_sha1();
127                         }
128
129                 return dsa_builtin_paramgen(ret, bits, qbits, evpmd,
130                         seed_in, seed_len, NULL, counter_ret, h_ret, cb);
131                 }
132         }
133
134 int dsa_builtin_paramgen(DSA *ret, size_t bits, size_t qbits,
135         const EVP_MD *evpmd, const unsigned char *seed_in, size_t seed_len,
136         unsigned char *seed_out,
137         int *counter_ret, unsigned long *h_ret, BN_GENCB *cb)
138         {
139         int ok=0;
140         unsigned char seed[SHA256_DIGEST_LENGTH];
141         unsigned char md[SHA256_DIGEST_LENGTH];
142         unsigned char buf[SHA256_DIGEST_LENGTH],buf2[SHA256_DIGEST_LENGTH];
143         BIGNUM *r0,*W,*X,*c,*test;
144         BIGNUM *g=NULL,*q=NULL,*p=NULL;
145         BN_MONT_CTX *mont=NULL;
146         int i, k, n=0, m=0, qsize = qbits >> 3;
147         int counter=0;
148         int r=0;
149         BN_CTX *ctx=NULL;
150         unsigned int h=2;
151
152         if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH &&
153             qsize != SHA256_DIGEST_LENGTH)
154                 /* invalid q size */
155                 return 0;
156
157         if (evpmd == NULL)
158                 /* use SHA1 as default */
159                 evpmd = EVP_sha1();
160
161         if (bits < 512)
162                 bits = 512;
163
164         bits = (bits+63)/64*64;
165
166         /* NB: seed_len == 0 is special case: copy generated seed to
167          * seed_in if it is not NULL.
168          */
169         if (seed_len && (seed_len < (size_t)qsize))
170                 seed_in = NULL;         /* seed buffer too small -- ignore */
171         if (seed_len > (size_t)qsize) 
172                 seed_len = qsize;       /* App. 2.2 of FIPS PUB 186 allows larger SEED,
173                                          * but our internal buffers are restricted to 160 bits*/
174         if (seed_in != NULL)
175                 memcpy(seed, seed_in, seed_len);
176
177         if ((ctx=BN_CTX_new()) == NULL)
178                 goto err;
179
180         if ((mont=BN_MONT_CTX_new()) == NULL)
181                 goto err;
182
183         BN_CTX_start(ctx);
184         r0 = BN_CTX_get(ctx);
185         g = BN_CTX_get(ctx);
186         W = BN_CTX_get(ctx);
187         q = BN_CTX_get(ctx);
188         X = BN_CTX_get(ctx);
189         c = BN_CTX_get(ctx);
190         p = BN_CTX_get(ctx);
191         test = BN_CTX_get(ctx);
192
193         if (!BN_lshift(test,BN_value_one(),bits-1))
194                 goto err;
195
196         for (;;)
197                 {
198                 for (;;) /* find q */
199                         {
200                         int seed_is_random;
201
202                         /* step 1 */
203                         if(!BN_GENCB_call(cb, 0, m++))
204                                 goto err;
205
206                         if (!seed_len)
207                                 {
208                                 RAND_pseudo_bytes(seed, qsize);
209                                 seed_is_random = 1;
210                                 }
211                         else
212                                 {
213                                 seed_is_random = 0;
214                                 seed_len=0; /* use random seed if 'seed_in' turns out to be bad*/
215                                 }
216                         memcpy(buf , seed, qsize);
217                         memcpy(buf2, seed, qsize);
218                         /* precompute "SEED + 1" for step 7: */
219                         for (i = qsize-1; i >= 0; i--)
220                                 {
221                                 buf[i]++;
222                                 if (buf[i] != 0)
223                                         break;
224                                 }
225
226                         /* step 2 */
227                         if (!EVP_Digest(seed, qsize, md,   NULL, evpmd, NULL))
228                                 goto err;
229                         if (!EVP_Digest(buf,  qsize, buf2, NULL, evpmd, NULL))
230                                 goto err;
231                         for (i = 0; i < qsize; i++)
232                                 md[i]^=buf2[i];
233
234                         /* step 3 */
235                         md[0] |= 0x80;
236                         md[qsize-1] |= 0x01;
237                         if (!BN_bin2bn(md, qsize, q))
238                                 goto err;
239
240                         /* step 4 */
241                         r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx,
242                                         seed_is_random, cb);
243                         if (r > 0)
244                                 break;
245                         if (r != 0)
246                                 goto err;
247
248                         /* do a callback call */
249                         /* step 5 */
250                         }
251
252                 if(!BN_GENCB_call(cb, 2, 0)) goto err;
253                 if(!BN_GENCB_call(cb, 3, 0)) goto err;
254
255                 /* step 6 */
256                 counter=0;
257                 /* "offset = 2" */
258
259                 n=(bits-1)/160;
260
261                 for (;;)
262                         {
263                         if ((counter != 0) && !BN_GENCB_call(cb, 0, counter))
264                                 goto err;
265
266                         /* step 7 */
267                         BN_zero(W);
268                         /* now 'buf' contains "SEED + offset - 1" */
269                         for (k=0; k<=n; k++)
270                                 {
271                                 /* obtain "SEED + offset + k" by incrementing: */
272                                 for (i = qsize-1; i >= 0; i--)
273                                         {
274                                         buf[i]++;
275                                         if (buf[i] != 0)
276                                                 break;
277                                         }
278
279                                 if (!EVP_Digest(buf, qsize, md ,NULL, evpmd,
280                                                                         NULL))
281                                         goto err;
282
283                                 /* step 8 */
284                                 if (!BN_bin2bn(md, qsize, r0))
285                                         goto err;
286                                 if (!BN_lshift(r0,r0,(qsize << 3)*k)) goto err;
287                                 if (!BN_add(W,W,r0)) goto err;
288                                 }
289
290                         /* more of step 8 */
291                         if (!BN_mask_bits(W,bits-1)) goto err;
292                         if (!BN_copy(X,W)) goto err;
293                         if (!BN_add(X,X,test)) goto err;
294
295                         /* step 9 */
296                         if (!BN_lshift1(r0,q)) goto err;
297                         if (!BN_mod(c,X,r0,ctx)) goto err;
298                         if (!BN_sub(r0,c,BN_value_one())) goto err;
299                         if (!BN_sub(p,X,r0)) goto err;
300
301                         /* step 10 */
302                         if (BN_cmp(p,test) >= 0)
303                                 {
304                                 /* step 11 */
305                                 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks,
306                                                 ctx, 1, cb);
307                                 if (r > 0)
308                                                 goto end; /* found it */
309                                 if (r != 0)
310                                         goto err;
311                                 }
312
313                         /* step 13 */
314                         counter++;
315                         /* "offset = offset + n + 1" */
316
317                         /* step 14 */
318                         if (counter >= 4096) break;
319                         }
320                 }
321 end:
322         if(!BN_GENCB_call(cb, 2, 1))
323                 goto err;
324
325         /* We now need to generate g */
326         /* Set r0=(p-1)/q */
327         if (!BN_sub(test,p,BN_value_one())) goto err;
328         if (!BN_div(r0,NULL,test,q,ctx)) goto err;
329
330         if (!BN_set_word(test,h)) goto err;
331         if (!BN_MONT_CTX_set(mont,p,ctx)) goto err;
332
333         for (;;)
334                 {
335                 /* g=test^r0%p */
336                 if (!BN_mod_exp_mont(g,test,r0,p,ctx,mont)) goto err;
337                 if (!BN_is_one(g)) break;
338                 if (!BN_add(test,test,BN_value_one())) goto err;
339                 h++;
340                 }
341
342         if(!BN_GENCB_call(cb, 3, 1))
343                 goto err;
344
345         ok=1;
346 err:
347         if (ok)
348                 {
349                 if(ret->p) BN_free(ret->p);
350                 if(ret->q) BN_free(ret->q);
351                 if(ret->g) BN_free(ret->g);
352                 ret->p=BN_dup(p);
353                 ret->q=BN_dup(q);
354                 ret->g=BN_dup(g);
355                 if (ret->p == NULL || ret->q == NULL || ret->g == NULL)
356                         {
357                         ok=0;
358                         goto err;
359                         }
360                 if (counter_ret != NULL) *counter_ret=counter;
361                 if (h_ret != NULL) *h_ret=h;
362                 if (seed_out)
363                         memcpy(seed_out, seed, qsize);
364                 }
365         if(ctx)
366                 {
367                 BN_CTX_end(ctx);
368                 BN_CTX_free(ctx);
369                 }
370         if (mont != NULL) BN_MONT_CTX_free(mont);
371         return ok;
372         }
373
374 #ifdef OPENSSL_FIPS
375 #undef fips_dsa_builtin_paramgen2
376 extern int fips_dsa_builtin_paramgen2(DSA *ret, size_t L, size_t N,
377         const EVP_MD *evpmd, const unsigned char *seed_in, size_t seed_len,
378         int idx, unsigned char *seed_out,
379         int *counter_ret, unsigned long *h_ret, BN_GENCB *cb);
380 #endif
381
382 /* This is a parameter generation algorithm for the DSA2 algorithm as
383  * described in FIPS 186-3.
384  */
385
386 int dsa_builtin_paramgen2(DSA *ret, size_t L, size_t N,
387         const EVP_MD *evpmd, const unsigned char *seed_in, size_t seed_len,
388         int idx, unsigned char *seed_out,
389         int *counter_ret, unsigned long *h_ret, BN_GENCB *cb)
390         {
391         int ok=-1;
392         unsigned char *seed = NULL, *seed_tmp = NULL;
393         unsigned char md[EVP_MAX_MD_SIZE];
394         int mdsize;
395         BIGNUM *r0,*W,*X,*c,*test;
396         BIGNUM *g=NULL,*q=NULL,*p=NULL;
397         BN_MONT_CTX *mont=NULL;
398         int i, k, n=0, m=0, qsize = N >> 3;
399         int counter=0;
400         int r=0;
401         BN_CTX *ctx=NULL;
402         EVP_MD_CTX mctx;
403         unsigned int h=2;
404
405 #ifdef OPENSSL_FIPS
406
407         if (FIPS_mode())
408                 return fips_dsa_builtin_paramgen2(ret, L, N, evpmd,
409                                                   seed_in, seed_len, idx,
410                                                   seed_out, counter_ret,
411                                                   h_ret, cb);
412 #endif
413
414         EVP_MD_CTX_init(&mctx);
415
416         if (evpmd == NULL)
417                 {
418                 if (N == 160)
419                         evpmd = EVP_sha1();
420                 else if (N == 224)
421                         evpmd = EVP_sha224();
422                 else
423                         evpmd = EVP_sha256();
424                 }
425
426         mdsize = EVP_MD_size(evpmd);
427         /* If unverificable g generation only don't need seed */
428         if (!ret->p || !ret->q || idx >= 0)
429                 {
430                 if (seed_len == 0)
431                         seed_len = mdsize;
432
433                 seed = OPENSSL_malloc(seed_len);
434
435                 if (seed_out)
436                         seed_tmp = seed_out;
437                 else
438                         seed_tmp = OPENSSL_malloc(seed_len);
439
440                 if (!seed || !seed_tmp)
441                         goto err;
442
443                 if (seed_in)
444                         memcpy(seed, seed_in, seed_len);
445
446                 }
447
448         if ((ctx=BN_CTX_new()) == NULL)
449                 goto err;
450
451         if ((mont=BN_MONT_CTX_new()) == NULL)
452                 goto err;
453
454         BN_CTX_start(ctx);
455         r0 = BN_CTX_get(ctx);
456         g = BN_CTX_get(ctx);
457         W = BN_CTX_get(ctx);
458         X = BN_CTX_get(ctx);
459         c = BN_CTX_get(ctx);
460         test = BN_CTX_get(ctx);
461
462         /* if p, q already supplied generate g only */
463         if (ret->p && ret->q)
464                 {
465                 p = ret->p;
466                 q = ret->q;
467                 if (idx >= 0)
468                         memcpy(seed_tmp, seed, seed_len);
469                 goto g_only;
470                 }
471         else
472                 {
473                 p = BN_CTX_get(ctx);
474                 q = BN_CTX_get(ctx);
475                 }
476
477         if (!BN_lshift(test,BN_value_one(),L-1))
478                 goto err;
479         for (;;)
480                 {
481                 for (;;) /* find q */
482                         {
483                         unsigned char *pmd;
484                         /* step 1 */
485                         if(!BN_GENCB_call(cb, 0, m++))
486                                 goto err;
487
488                         if (!seed_in)
489                                 {
490                                 if (RAND_pseudo_bytes(seed, seed_len) < 0)
491                                         goto err;
492                                 }
493                         /* step 2 */
494                         if (!EVP_Digest(seed, seed_len, md, NULL, evpmd, NULL))
495                                 goto err;
496                         /* Take least significant bits of md */
497                         if (mdsize > qsize)
498                                 pmd = md + mdsize - qsize;
499                         else
500                                 pmd = md;
501
502                         if (mdsize < qsize)
503                                 memset(md + mdsize, 0, qsize - mdsize);
504
505                         /* step 3 */
506                         pmd[0] |= 0x80;
507                         pmd[qsize-1] |= 0x01;
508                         if (!BN_bin2bn(pmd, qsize, q))
509                                 goto err;
510
511                         /* step 4 */
512                         r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx,
513                                         seed_in ? 1 : 0, cb);
514                         if (r > 0)
515                                 break;
516                         if (r != 0)
517                                 goto err;
518                         /* Provided seed didn't produce a prime: error */
519                         if (seed_in)
520                                 {
521                                 ok = 0;
522                                 DSAerr(DSA_F_DSA_BUILTIN_PARAMGEN2, DSA_R_Q_NOT_PRIME);
523                                 goto err;
524                                 }
525
526                         /* do a callback call */
527                         /* step 5 */
528                         }
529                 /* Copy seed to seed_out before we mess with it */
530                 if (seed_out)
531                         memcpy(seed_out, seed, seed_len);
532
533                 if(!BN_GENCB_call(cb, 2, 0)) goto err;
534                 if(!BN_GENCB_call(cb, 3, 0)) goto err;
535
536                 /* step 6 */
537                 counter=0;
538                 /* "offset = 1" */
539
540                 n=(L-1)/(mdsize << 3);
541
542                 for (;;)
543                         {
544                         if ((counter != 0) && !BN_GENCB_call(cb, 0, counter))
545                                 goto err;
546
547                         /* step 7 */
548                         BN_zero(W);
549                         /* now 'buf' contains "SEED + offset - 1" */
550                         for (k=0; k<=n; k++)
551                                 {
552                                 /* obtain "SEED + offset + k" by incrementing: */
553                                 for (i = seed_len-1; i >= 0; i--)
554                                         {
555                                         seed[i]++;
556                                         if (seed[i] != 0)
557                                                 break;
558                                         }
559
560                                 if (!EVP_Digest(seed, seed_len, md ,NULL, evpmd,
561                                                                         NULL))
562                                         goto err;
563
564                                 /* step 8 */
565                                 if (!BN_bin2bn(md, mdsize, r0))
566                                         goto err;
567                                 if (!BN_lshift(r0,r0,(mdsize << 3)*k)) goto err;
568                                 if (!BN_add(W,W,r0)) goto err;
569                                 }
570
571                         /* more of step 8 */
572                         if (!BN_mask_bits(W,L-1)) goto err;
573                         if (!BN_copy(X,W)) goto err;
574                         if (!BN_add(X,X,test)) goto err;
575
576                         /* step 9 */
577                         if (!BN_lshift1(r0,q)) goto err;
578                         if (!BN_mod(c,X,r0,ctx)) goto err;
579                         if (!BN_sub(r0,c,BN_value_one())) goto err;
580                         if (!BN_sub(p,X,r0)) goto err;
581
582                         /* step 10 */
583                         if (BN_cmp(p,test) >= 0)
584                                 {
585                                 /* step 11 */
586                                 r = BN_is_prime_fasttest_ex(p, DSS_prime_checks,
587                                                 ctx, 1, cb);
588                                 if (r > 0)
589                                                 goto end; /* found it */
590                                 if (r != 0)
591                                         goto err;
592                                 }
593
594                         /* step 13 */
595                         counter++;
596                         /* "offset = offset + n + 1" */
597
598                         /* step 14 */
599                         if (counter >= (int)(4 * L)) break;
600                         }
601                 if (seed_in)
602                         {
603                         ok = 0;
604                         DSAerr(DSA_F_DSA_BUILTIN_PARAMGEN2, DSA_R_INVALID_PARAMETERS);
605                         goto err;
606                         }
607                 }
608 end:
609         if(!BN_GENCB_call(cb, 2, 1))
610                 goto err;
611
612         g_only:
613
614         /* We now need to generate g */
615         /* Set r0=(p-1)/q */
616         if (!BN_sub(test,p,BN_value_one())) goto err;
617         if (!BN_div(r0,NULL,test,q,ctx)) goto err;
618
619         if (idx < 0)
620                 {
621                 if (!BN_set_word(test,h))
622                         goto err;
623                 }
624         else
625                 h = 1;
626         if (!BN_MONT_CTX_set(mont,p,ctx)) goto err;
627
628         for (;;)
629                 {
630                 static const unsigned char ggen[4] = {0x67,0x67,0x65,0x6e};
631                 if (idx >= 0)
632                         {
633                         md[0] = idx & 0xff;
634                         md[1] = (h >> 8) & 0xff;
635                         md[2] = h & 0xff;
636                         if (!EVP_DigestInit_ex(&mctx, evpmd, NULL))
637                                 goto err;
638                         if (!EVP_DigestUpdate(&mctx, seed_tmp, seed_len))
639                                 goto err;
640                         if (!EVP_DigestUpdate(&mctx, ggen, sizeof(ggen)))
641                                 goto err;
642                         if (!EVP_DigestUpdate(&mctx, md, 3))
643                                 goto err;
644                         if (!EVP_DigestFinal_ex(&mctx, md, NULL))
645                                 goto err;
646                         if (!BN_bin2bn(md, mdsize, test))
647                                 goto err;
648                         }
649                 /* g=test^r0%p */
650                 if (!BN_mod_exp_mont(g,test,r0,p,ctx,mont)) goto err;
651                 if (!BN_is_one(g)) break;
652                 if (idx < 0 && !BN_add(test,test,BN_value_one())) goto err;
653                 h++;
654                 if ( idx >= 0 && h > 0xffff)
655                         goto err;
656                 }
657
658         if(!BN_GENCB_call(cb, 3, 1))
659                 goto err;
660
661         ok=1;
662 err:
663         if (ok == 1)
664                 {
665                 if (p != ret->p)
666                         {
667                         if(ret->p) BN_free(ret->p);
668                         ret->p=BN_dup(p);
669                         }
670                 if (q != ret->q)
671                         {
672                         if(ret->q) BN_free(ret->q);
673                         ret->q=BN_dup(q);
674                         }
675                 if(ret->g) BN_free(ret->g);
676                 ret->g=BN_dup(g);
677                 if (ret->p == NULL || ret->q == NULL || ret->g == NULL)
678                         {
679                         ok=-1;
680                         goto err;
681                         }
682                 if (counter_ret != NULL) *counter_ret=counter;
683                 if (h_ret != NULL) *h_ret=h;
684                 }
685         if (seed)
686                 OPENSSL_free(seed);
687         if (seed_out != seed_tmp)
688                 OPENSSL_free(seed_tmp);
689         if(ctx)
690                 {
691                 BN_CTX_end(ctx);
692                 BN_CTX_free(ctx);
693                 }
694         if (mont != NULL) BN_MONT_CTX_free(mont);
695         EVP_MD_CTX_cleanup(&mctx);
696         return ok;
697         }
698
699 int dsa_paramgen_check_g(DSA *dsa)
700         {
701         BN_CTX *ctx;
702         BIGNUM *tmp;
703         BN_MONT_CTX *mont = NULL;
704         int rv = -1;
705         ctx = BN_CTX_new();
706         if (!ctx)
707                 return -1;
708         BN_CTX_start(ctx);
709         if (BN_cmp(dsa->g, BN_value_one()) <= 0)
710                 return 0;
711         if (BN_cmp(dsa->g, dsa->p) >= 0)
712                 return 0;
713         tmp = BN_CTX_get(ctx);
714         if (!tmp)
715                 goto err;
716         if ((mont=BN_MONT_CTX_new()) == NULL)
717                 goto err;
718         if (!BN_MONT_CTX_set(mont,dsa->p,ctx))
719                 goto err;
720         /* Work out g^q mod p */
721         if (!BN_mod_exp_mont(tmp,dsa->g,dsa->q, dsa->p, ctx, mont))
722                 goto err;
723         if (!BN_cmp(tmp, BN_value_one()))
724                 rv = 1;
725         else
726                 rv = 0;
727         err:
728         BN_CTX_end(ctx);
729         if (mont)
730                 BN_MONT_CTX_free(mont);
731         BN_CTX_free(ctx);
732         return rv;
733
734         }
735 #endif