/* crypto/rsa/rsa_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.]
 */


/* NB: these functions have been "upgraded", the deprecated versions (which are
 * compatibility wrappers using these functions) are in rsa_depr.c.
 * - Geoff
 */

#include <stdio.h>
#include <time.h>
#include "cryptlib.h"
#include <openssl/bn.h>
#include <openssl/rsa.h>

static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb);

/* NB: this wrapper would normally be placed in rsa_lib.c and the static
 * implementation would probably be in rsa_eay.c. Nonetheless, is kept here so
 * that we don't introduce a new linker dependency. Eg. any application that
 * wasn't previously linking object code related to key-generation won't have to
 * now just because key-generation is part of RSA_METHOD. */
int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)
	{
	if(rsa->meth->rsa_keygen)
		return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
	return rsa_builtin_keygen(rsa, bits, e_value, cb);
	}

static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)
	{
	BIGNUM *r0=NULL,*r1=NULL,*r2=NULL,*r3=NULL,*tmp;
	BIGNUM local_r0,local_d,local_p;
	BIGNUM *pr0,*d,*p;
	int bitsp,bitsq,ok= -1,n=0;
	BN_CTX *ctx=NULL;

	ctx=BN_CTX_new();
	if (ctx == NULL) goto err;
	BN_CTX_start(ctx);
	r0 = BN_CTX_get(ctx);
	r1 = BN_CTX_get(ctx);
	r2 = BN_CTX_get(ctx);
	r3 = BN_CTX_get(ctx);
	if (r3 == NULL) goto err;

	bitsp=(bits+1)/2;
	bitsq=bits-bitsp;

	/* We need the RSA components non-NULL */
	if(!rsa->n && ((rsa->n=BN_new()) == NULL)) goto err;
	if(!rsa->d && ((rsa->d=BN_new()) == NULL)) goto err;
	if(!rsa->e && ((rsa->e=BN_new()) == NULL)) goto err;
	if(!rsa->p && ((rsa->p=BN_new()) == NULL)) goto err;
	if(!rsa->q && ((rsa->q=BN_new()) == NULL)) goto err;
	if(!rsa->dmp1 && ((rsa->dmp1=BN_new()) == NULL)) goto err;
	if(!rsa->dmq1 && ((rsa->dmq1=BN_new()) == NULL)) goto err;
	if(!rsa->iqmp && ((rsa->iqmp=BN_new()) == NULL)) goto err;

	BN_copy(rsa->e, e_value);

	/* generate p and q */
	for (;;)
		{
		if(!BN_generate_prime_ex(rsa->p, bitsp, 0, NULL, NULL, cb))
			goto err;
		if (!BN_sub(r2,rsa->p,BN_value_one())) goto err;
		if (!BN_gcd(r1,r2,rsa->e,ctx)) goto err;
		if (BN_is_one(r1)) break;
		if(!BN_GENCB_call(cb, 2, n++))
			goto err;
		}
	if(!BN_GENCB_call(cb, 3, 0))
		goto err;
	for (;;)
		{
		/* When generating ridiculously small keys, we can get stuck
		 * continually regenerating the same prime values. Check for
		 * this and bail if it happens 3 times. */
		unsigned int degenerate = 0;
		do
			{
			if(!BN_generate_prime_ex(rsa->q, bitsq, 0, NULL, NULL, cb))
				goto err;
			} while((BN_cmp(rsa->p, rsa->q) == 0) && (++degenerate < 3));
		if(degenerate == 3)
			{
			ok = 0; /* we set our own err */
			RSAerr(RSA_F_RSA_BUILTIN_KEYGEN,RSA_R_KEY_SIZE_TOO_SMALL);
			goto err;
			}
		if (!BN_sub(r2,rsa->q,BN_value_one())) goto err;
		if (!BN_gcd(r1,r2,rsa->e,ctx)) goto err;
		if (BN_is_one(r1))
			break;
		if(!BN_GENCB_call(cb, 2, n++))
			goto err;
		}
	if(!BN_GENCB_call(cb, 3, 1))
		goto err;
	if (BN_cmp(rsa->p,rsa->q) < 0)
		{
		tmp=rsa->p;
		rsa->p=rsa->q;
		rsa->q=tmp;
		}

	/* calculate n */
	if (!BN_mul(rsa->n,rsa->p,rsa->q,ctx)) goto err;

	/* calculate d */
	if (!BN_sub(r1,rsa->p,BN_value_one())) goto err;	/* p-1 */
	if (!BN_sub(r2,rsa->q,BN_value_one())) goto err;	/* q-1 */
	if (!BN_mul(r0,r1,r2,ctx)) goto err;	/* (p-1)(q-1) */
	if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME))
		{
		  pr0 = &local_r0;
		  BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);
		}
	else
	  pr0 = r0;
	if (!BN_mod_inverse(rsa->d,rsa->e,pr0,ctx)) goto err;	/* d */

	/* set up d for correct BN_FLG_CONSTTIME flag */
	if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME))
		{
		d = &local_d;
		BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
		}
	else
		d = rsa->d;

	/* calculate d mod (p-1) */
	if (!BN_mod(rsa->dmp1,d,r1,ctx)) goto err;

	/* calculate d mod (q-1) */
	if (!BN_mod(rsa->dmq1,d,r2,ctx)) goto err;

	/* calculate inverse of q mod p */
	if (!(rsa->flags & RSA_FLAG_NO_CONSTTIME))
		{
		p = &local_p;
		BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);
		}
	else
		p = rsa->p;
	if (!BN_mod_inverse(rsa->iqmp,rsa->q,p,ctx)) goto err;

	ok=1;
err:
	if (ok == -1)
		{
		RSAerr(RSA_F_RSA_BUILTIN_KEYGEN,ERR_LIB_BN);
		ok=0;
		}
	if (ctx != NULL)
		{
		BN_CTX_end(ctx);
		BN_CTX_free(ctx);
		}

	return ok;
	}