/* 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>

 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);

 EXPORT_C 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