/* 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