/* crypto/bn/bn_prime.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.]
 */

#include <stdio.h>
#include <time.h>
#include "cryptlib.h"
#include "bn_lcl.h"
#include <openssl/rand.h>

/* The quick sieve algorithm approach to weeding out primes is
 * Philip Zimmermann's, as implemented in PGP.  I have had a read of
 * his comments and implemented my own version.
 */
#include "bn_prime.h"

static int witness(BIGNUM *w, BIGNUM *a, BIGNUM *a1, BIGNUM *a1_odd, int k,
	BN_CTX *ctx, BN_MONT_CTX *mont);
static int probable_prime(BIGNUM *rnd, int bits);
static int probable_prime_dh(BIGNUM *rnd, int bits,
	BIGNUM *add, BIGNUM *rem, BN_CTX *ctx);
static int probable_prime_dh_safe(BIGNUM *rnd, int bits,
	BIGNUM *add, BIGNUM *rem, BN_CTX *ctx);

BIGNUM *BN_generate_prime(BIGNUM *ret, int bits, int safe, BIGNUM *add,
	     BIGNUM *rem, void (*callback)(int,int,void *), void *cb_arg)
	{
	BIGNUM *rnd=NULL;
	BIGNUM t;
	int found=0;
	int i,j,c1=0;
	BN_CTX *ctx;
	int checks = BN_prime_checks_for_size(bits);

	ctx=BN_CTX_new();
	if (ctx == NULL) goto err;
	if (ret == NULL)
		{
		if ((rnd=BN_new()) == NULL) goto err;
		}
	else
		rnd=ret;
	BN_init(&t);
loop: 
	/* make a random number and set the top and bottom bits */
	if (add == NULL)
		{
		if (!probable_prime(rnd,bits)) goto err;
		}
	else
		{
		if (safe)
			{
			if (!probable_prime_dh_safe(rnd,bits,add,rem,ctx))
				 goto err;
			}
		else
			{
			if (!probable_prime_dh(rnd,bits,add,rem,ctx))
				goto err;
			}
		}
	/* if (BN_mod_word(rnd,(BN_ULONG)3) == 1) goto loop; */
	if (callback != NULL) callback(0,c1++,cb_arg);

	if (!safe)
		{
		i=BN_is_prime_fasttest(rnd,checks,callback,ctx,cb_arg,0);
		if (i == -1) goto err;
		if (i == 0) goto loop;
		}
	else
		{
		/* for "safe prime" generation,
		 * check that (p-1)/2 is prime.
		 * Since a prime is odd, We just
		 * need to divide by 2 */
		if (!BN_rshift1(&t,rnd)) goto err;

		for (i=0; i<checks; i++)
			{
			j=BN_is_prime_fasttest(rnd,1,callback,ctx,cb_arg,0);
			if (j == -1) goto err;
			if (j == 0) goto loop;

			j=BN_is_prime_fasttest(&t,1,callback,ctx,cb_arg,0);
			if (j == -1) goto err;
			if (j == 0) goto loop;

			if (callback != NULL) callback(2,c1-1,cb_arg);
			/* We have a safe prime test pass */
			}
		}
	/* we have a prime :-) */
	found = 1;
err:
	if (!found && (ret == NULL) && (rnd != NULL)) BN_free(rnd);
	BN_free(&t);
	if (ctx != NULL) BN_CTX_free(ctx);
	return(found ? rnd : NULL);
	}

int BN_is_prime(BIGNUM *a, int checks, void (*callback)(int,int,void *),
	BN_CTX *ctx_passed, void *cb_arg)
	{
	return BN_is_prime_fasttest(a, checks, callback, ctx_passed, cb_arg, 0);
	}

int BN_is_prime_fasttest(BIGNUM *a, int checks,
		void (*callback)(int,int,void *),
		BN_CTX *ctx_passed, void *cb_arg,
		int do_trial_division)
	{
	int i, j, ret = -1;
	int k;
	BN_CTX *ctx = NULL;
	BIGNUM *a1, *a1_odd, *check; /* taken from ctx */
	BN_MONT_CTX *mont = NULL;

	if (checks == BN_prime_checks)
		checks = BN_prime_checks_for_size(BN_num_bits(a));

	if (a->neg) /* for now, refuse to handle negative numbers */
		return -1;

	/* first look for small factors */
	if (!BN_is_odd(a))
		return(0);
	if (do_trial_division)
		{
		for (i = 1; i < NUMPRIMES; i++)
			if (BN_mod_word(a, primes[i]) == 0) 
				return 0;
		if (callback != NULL) callback(1, -1, cb_arg);
		}

	if (ctx_passed != NULL)
		ctx = ctx_passed;
	else
		if ((ctx=BN_CTX_new()) == NULL)
			goto err;
	a1 = &(ctx->bn[ctx->tos++]);
	a1_odd = &(ctx->bn[ctx->tos++]);
	check = &(ctx->bn[ctx->tos++]);;

	/* compute a1 := a - 1 */
	if (!BN_copy(a1, a))
		goto err;
	if (!BN_sub_word(a1, 1))
		goto err;
	if (BN_is_zero(a1))
		{
		ret = 0;
		goto err;
		}

	/* write  a1  as  a1_odd * 2^k */
	k = 1;
	while (!BN_is_bit_set(a1, k))
		k++;
	if (!BN_rshift(a1_odd, a1, k))
		goto err;

	/* Montgomery setup for computations mod a */
	mont = BN_MONT_CTX_new();
	if (mont == NULL)
		goto err;
	if (!BN_MONT_CTX_set(mont, a, ctx))
		goto err;
	
	for (i = 0; i < checks; i++)
		{
		if (!BN_pseudo_rand(check, BN_num_bits(a1), 0, 0))
			goto err;
		if (BN_cmp(check, a1) >= 0)
			if (!BN_sub(check, check, a1))
				goto err;
		if (!BN_add_word(check, 1))
			goto err;
		/* now 1 <= check < a */

		j = witness(check, a, a1, a1_odd, k, ctx, mont);
		if (j == -1) goto err;
		if (j)
			{
			ret=0;
			goto err;
			}
		if (callback != NULL) callback(1,i,cb_arg);
		}
	ret=1;
err:
	if (ctx_passed != NULL)
		ctx_passed->tos -= 3; /* a1, a1_odd, check */
	else if (ctx != NULL)
		BN_CTX_free(ctx);
	if (mont != NULL)
		BN_MONT_CTX_free(mont);

	return(ret);
	}

static int witness(BIGNUM *w, BIGNUM *a, BIGNUM *a1, BIGNUM *a1_odd, int k,
	BN_CTX *ctx, BN_MONT_CTX *mont)
	{
	if (!BN_mod_exp_mont(w, w, a1_odd, a, ctx, mont)) /* w := w^a1_odd mod a */
		return -1;
	if (BN_is_one(w))
		return 0; /* probably prime */
	if (BN_cmp(w, a1) == 0)
		return 0; /* w == -1 (mod a),  'a' is probably prime */
	while (--k)
		{
		if (!BN_mod_mul(w, w, w, a, ctx)) /* w := w^2 mod a */
			return -1;
		if (BN_is_one(w))
			return 1; /* 'a' is composite, otherwise a previous 'w' would
			           * have been == -1 (mod 'a') */
		if (BN_cmp(w, a1) == 0)
			return 0; /* w == -1 (mod a), 'a' is probably prime */
		}
	/* If we get here, 'w' is the (a-1)/2-th power of the original 'w',
	 * and it is neither -1 nor +1 -- so 'a' cannot be prime */
	return 1;
	}

static int probable_prime(BIGNUM *rnd, int bits)
	{
	int i;
	BN_ULONG mods[NUMPRIMES];
	BN_ULONG delta,d;

again:
	if (!BN_rand(rnd,bits,1,1)) return(0);
	/* we now have a random number 'rand' to test. */
	for (i=1; i<NUMPRIMES; i++)
		mods[i]=BN_mod_word(rnd,(BN_ULONG)primes[i]);
	delta=0;
	loop: for (i=1; i<NUMPRIMES; i++)
		{
		/* check that rnd is not a prime and also
		 * that gcd(rnd-1,primes) == 1 (except for 2) */
		if (((mods[i]+delta)%primes[i]) <= 1)
			{
			d=delta;
			delta+=2;
			/* perhaps need to check for overflow of
			 * delta (but delta can be upto 2^32)
			 * 21-May-98 eay - added overflow check */
			if (delta < d) goto again;
			goto loop;
			}
		}
	if (!BN_add_word(rnd,delta)) return(0);
	return(1);
	}

static int probable_prime_dh(BIGNUM *rnd, int bits, BIGNUM *add, BIGNUM *rem,
	     BN_CTX *ctx)
	{
	int i,ret=0;
	BIGNUM *t1;

	t1= &(ctx->bn[ctx->tos++]);

	if (!BN_rand(rnd,bits,0,1)) goto err;

	/* we need ((rnd-rem) % add) == 0 */

	if (!BN_mod(t1,rnd,add,ctx)) goto err;
	if (!BN_sub(rnd,rnd,t1)) goto err;
	if (rem == NULL)
		{ if (!BN_add_word(rnd,1)) goto err; }
	else
		{ if (!BN_add(rnd,rnd,rem)) goto err; }

	/* we now have a random number 'rand' to test. */

	loop: for (i=1; i<NUMPRIMES; i++)
		{
		/* check that rnd is a prime */
		if (BN_mod_word(rnd,(BN_ULONG)primes[i]) <= 1)
			{
			if (!BN_add(rnd,rnd,add)) goto err;
			goto loop;
			}
		}
	ret=1;
err:
	ctx->tos--;
	return(ret);
	}

static int probable_prime_dh_safe(BIGNUM *p, int bits, BIGNUM *padd,
	     BIGNUM *rem, BN_CTX *ctx)
	{
	int i,ret=0;
	BIGNUM *t1,*qadd=NULL,*q=NULL;

	bits--;
	t1= &(ctx->bn[ctx->tos++]);
	q= &(ctx->bn[ctx->tos++]);
	qadd= &(ctx->bn[ctx->tos++]);

	if (!BN_rshift1(qadd,padd)) goto err;
		
	if (!BN_rand(q,bits,0,1)) goto err;

	/* we need ((rnd-rem) % add) == 0 */
	if (!BN_mod(t1,q,qadd,ctx)) goto err;
	if (!BN_sub(q,q,t1)) goto err;
	if (rem == NULL)
		{ if (!BN_add_word(q,1)) goto err; }
	else
		{
		if (!BN_rshift1(t1,rem)) goto err;
		if (!BN_add(q,q,t1)) goto err;
		}

	/* we now have a random number 'rand' to test. */
	if (!BN_lshift1(p,q)) goto err;
	if (!BN_add_word(p,1)) goto err;

	loop: for (i=1; i<NUMPRIMES; i++)
		{
		/* check that p and q are prime */
		/* check that for p and q
		 * gcd(p-1,primes) == 1 (except for 2) */
		if (	(BN_mod_word(p,(BN_ULONG)primes[i]) == 0) ||
			(BN_mod_word(q,(BN_ULONG)primes[i]) == 0))
			{
			if (!BN_add(p,p,padd)) goto err;
			if (!BN_add(q,q,qadd)) goto err;
			goto loop;
			}
		}
	ret=1;
err:
	ctx->tos-=3;
	return(ret);
	}