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dsa_gen.c

/* crypto/dsa/dsa_gen.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 * 
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 * 
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from 
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 * 
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#undef GENUINE_DSA

#ifdef GENUINE_DSA
/* Parameter generation follows the original release of FIPS PUB 186,
 * Appendix 2.2 (i.e. use SHA as defined in FIPS PUB 180) */
#define HASH    EVP_sha()
#else
/* Parameter generation follows the updated Appendix 2.2 for FIPS PUB 186,
 * also Appendix 2.2 of FIPS PUB 186-1 (i.e. use SHA as defined in
 * FIPS PUB 180-1) */
#define HASH    EVP_sha1()
#endif 

#include <openssl/opensslconf.h> /* To see if OPENSSL_NO_SHA is defined */

#ifndef OPENSSL_NO_SHA

#include <stdio.h>
#include <time.h>
#include "cryptlib.h"
#include <openssl/evp.h>
#include <openssl/bn.h>
#include <openssl/dsa.h>
#include <openssl/rand.h>
#include <openssl/sha.h>

#ifndef OPENSSL_FIPS

static int dsa_builtin_paramgen(DSA *ret, int bits,
            unsigned char *seed_in, int seed_len,
            int *counter_ret, unsigned long *h_ret, BN_GENCB *cb);

int DSA_generate_parameters_ex(DSA *ret, int bits,
            unsigned char *seed_in, int seed_len,
            int *counter_ret, unsigned long *h_ret, BN_GENCB *cb)
      {
      if(ret->meth->dsa_paramgen)
            return ret->meth->dsa_paramgen(ret, bits, seed_in, seed_len,
                        counter_ret, h_ret, cb);
      return dsa_builtin_paramgen(ret, bits, seed_in, seed_len,
                  counter_ret, h_ret, cb);
      }

static int dsa_builtin_paramgen(DSA *ret, int bits,
            unsigned char *seed_in, int seed_len,
            int *counter_ret, unsigned long *h_ret, BN_GENCB *cb)
      {
      int ok=0;
      unsigned char seed[SHA_DIGEST_LENGTH];
      unsigned char md[SHA_DIGEST_LENGTH];
      unsigned char buf[SHA_DIGEST_LENGTH],buf2[SHA_DIGEST_LENGTH];
      BIGNUM *r0,*W,*X,*c,*test;
      BIGNUM *g=NULL,*q=NULL,*p=NULL;
      BN_MONT_CTX *mont=NULL;
      int k,n=0,i,b,m=0;
      int counter=0;
      int r=0;
      BN_CTX *ctx=NULL;
      unsigned int h=2;

      if (bits < 512) bits=512;
      bits=(bits+63)/64*64;

      /* NB: seed_len == 0 is special case: copy generated seed to
       * seed_in if it is not NULL.
       */
      if (seed_len && (seed_len < 20))
            seed_in = NULL; /* seed buffer too small -- ignore */
      if (seed_len > 20) 
            seed_len = 20; /* App. 2.2 of FIPS PUB 186 allows larger SEED,
                            * but our internal buffers are restricted to 160 bits*/
      if ((seed_in != NULL) && (seed_len == 20))
            {
            memcpy(seed,seed_in,seed_len);
            /* set seed_in to NULL to avoid it being copied back */
            seed_in = NULL;
            }

      if ((ctx=BN_CTX_new()) == NULL) goto err;

      if ((mont=BN_MONT_CTX_new()) == NULL) goto err;

      BN_CTX_start(ctx);
      r0 = BN_CTX_get(ctx);
      g = BN_CTX_get(ctx);
      W = BN_CTX_get(ctx);
      q = BN_CTX_get(ctx);
      X = BN_CTX_get(ctx);
      c = BN_CTX_get(ctx);
      p = BN_CTX_get(ctx);
      test = BN_CTX_get(ctx);

      if (!BN_lshift(test,BN_value_one(),bits-1))
            goto err;

      for (;;)
            {
            for (;;) /* find q */
                  {
                  int seed_is_random;

                  /* step 1 */
                  if(!BN_GENCB_call(cb, 0, m++))
                        goto err;

                  if (!seed_len)
                        {
                        RAND_pseudo_bytes(seed,SHA_DIGEST_LENGTH);
                        seed_is_random = 1;
                        }
                  else
                        {
                        seed_is_random = 0;
                        seed_len=0; /* use random seed if 'seed_in' turns out to be bad*/
                        }
                  memcpy(buf,seed,SHA_DIGEST_LENGTH);
                  memcpy(buf2,seed,SHA_DIGEST_LENGTH);
                  /* precompute "SEED + 1" for step 7: */
                  for (i=SHA_DIGEST_LENGTH-1; i >= 0; i--)
                        {
                        buf[i]++;
                        if (buf[i] != 0) break;
                        }

                  /* step 2 */
                  EVP_Digest(seed,SHA_DIGEST_LENGTH,md,NULL,HASH, NULL);
                  EVP_Digest(buf,SHA_DIGEST_LENGTH,buf2,NULL,HASH, NULL);
                  for (i=0; i<SHA_DIGEST_LENGTH; i++)
                        md[i]^=buf2[i];

                  /* step 3 */
                  md[0]|=0x80;
                  md[SHA_DIGEST_LENGTH-1]|=0x01;
                  if (!BN_bin2bn(md,SHA_DIGEST_LENGTH,q)) goto err;

                  /* step 4 */
                  r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx,
                              seed_is_random, cb);
                  if (r > 0)
                        break;
                  if (r != 0)
                        goto err;

                  /* do a callback call */
                  /* step 5 */
                  }

            if(!BN_GENCB_call(cb, 2, 0)) goto err;
            if(!BN_GENCB_call(cb, 3, 0)) goto err;

            /* step 6 */
            counter=0;
            /* "offset = 2" */

            n=(bits-1)/160;
            b=(bits-1)-n*160;

            for (;;)
                  {
                  if ((counter != 0) && !BN_GENCB_call(cb, 0, counter))
                        goto err;

                  /* step 7 */
                  BN_zero(W);
                  /* now 'buf' contains "SEED + offset - 1" */
                  for (k=0; k<=n; k++)
                        {
                        /* obtain "SEED + offset + k" by incrementing: */
                        for (i=SHA_DIGEST_LENGTH-1; i >= 0; i--)
                              {
                              buf[i]++;
                              if (buf[i] != 0) break;
                              }

                        EVP_Digest(buf,SHA_DIGEST_LENGTH,md,NULL,HASH, NULL);

                        /* step 8 */
                        if (!BN_bin2bn(md,SHA_DIGEST_LENGTH,r0))
                              goto err;
                        if (!BN_lshift(r0,r0,160*k)) goto err;
                        if (!BN_add(W,W,r0)) goto err;
                        }

                  /* more of step 8 */
                  if (!BN_mask_bits(W,bits-1)) goto err;
                  if (!BN_copy(X,W)) goto err;
                  if (!BN_add(X,X,test)) goto err;

                  /* step 9 */
                  if (!BN_lshift1(r0,q)) goto err;
                  if (!BN_mod(c,X,r0,ctx)) goto err;
                  if (!BN_sub(r0,c,BN_value_one())) goto err;
                  if (!BN_sub(p,X,r0)) goto err;

                  /* step 10 */
                  if (BN_cmp(p,test) >= 0)
                        {
                        /* step 11 */
                        r = BN_is_prime_fasttest_ex(p, DSS_prime_checks,
                                    ctx, 1, cb);
                        if (r > 0)
                                    goto end; /* found it */
                        if (r != 0)
                              goto err;
                        }

                  /* step 13 */
                  counter++;
                  /* "offset = offset + n + 1" */

                  /* step 14 */
                  if (counter >= 4096) break;
                  }
            }
end:
      if(!BN_GENCB_call(cb, 2, 1))
            goto err;

      /* We now need to generate g */
      /* Set r0=(p-1)/q */
      if (!BN_sub(test,p,BN_value_one())) goto err;
      if (!BN_div(r0,NULL,test,q,ctx)) goto err;

      if (!BN_set_word(test,h)) goto err;
      if (!BN_MONT_CTX_set(mont,p,ctx)) goto err;

      for (;;)
            {
            /* g=test^r0%p */
            if (!BN_mod_exp_mont(g,test,r0,p,ctx,mont)) goto err;
            if (!BN_is_one(g)) break;
            if (!BN_add(test,test,BN_value_one())) goto err;
            h++;
            }

      if(!BN_GENCB_call(cb, 3, 1))
            goto err;

      ok=1;
err:
      if (ok)
            {
            if(ret->p) BN_free(ret->p);
            if(ret->q) BN_free(ret->q);
            if(ret->g) BN_free(ret->g);
            ret->p=BN_dup(p);
            ret->q=BN_dup(q);
            ret->g=BN_dup(g);
            if (ret->p == NULL || ret->q == NULL || ret->g == NULL)
                  {
                  ok=0;
                  goto err;
                  }
            if (seed_in != NULL) memcpy(seed_in,seed,20);
            if (counter_ret != NULL) *counter_ret=counter;
            if (h_ret != NULL) *h_ret=h;
            }
      if(ctx)
            {
            BN_CTX_end(ctx);
            BN_CTX_free(ctx);
            }
      if (mont != NULL) BN_MONT_CTX_free(mont);
      return ok;
      }
#endif
#endif

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