sl@0: /* crypto/bn/bn_mont.c */
sl@0: /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
sl@0:  * All rights reserved.
sl@0:  *
sl@0:  * This package is an SSL implementation written
sl@0:  * by Eric Young (eay@cryptsoft.com).
sl@0:  * The implementation was written so as to conform with Netscapes SSL.
sl@0:  * 
sl@0:  * This library is free for commercial and non-commercial use as long as
sl@0:  * the following conditions are aheared to.  The following conditions
sl@0:  * apply to all code found in this distribution, be it the RC4, RSA,
sl@0:  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
sl@0:  * included with this distribution is covered by the same copyright terms
sl@0:  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
sl@0:  * 
sl@0:  * Copyright remains Eric Young's, and as such any Copyright notices in
sl@0:  * the code are not to be removed.
sl@0:  * If this package is used in a product, Eric Young should be given attribution
sl@0:  * as the author of the parts of the library used.
sl@0:  * This can be in the form of a textual message at program startup or
sl@0:  * in documentation (online or textual) provided with the package.
sl@0:  * 
sl@0:  * Redistribution and use in source and binary forms, with or without
sl@0:  * modification, are permitted provided that the following conditions
sl@0:  * are met:
sl@0:  * 1. Redistributions of source code must retain the copyright
sl@0:  *    notice, this list of conditions and the following disclaimer.
sl@0:  * 2. Redistributions in binary form must reproduce the above copyright
sl@0:  *    notice, this list of conditions and the following disclaimer in the
sl@0:  *    documentation and/or other materials provided with the distribution.
sl@0:  * 3. All advertising materials mentioning features or use of this software
sl@0:  *    must display the following acknowledgement:
sl@0:  *    "This product includes cryptographic software written by
sl@0:  *     Eric Young (eay@cryptsoft.com)"
sl@0:  *    The word 'cryptographic' can be left out if the rouines from the library
sl@0:  *    being used are not cryptographic related :-).
sl@0:  * 4. If you include any Windows specific code (or a derivative thereof) from 
sl@0:  *    the apps directory (application code) you must include an acknowledgement:
sl@0:  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
sl@0:  * 
sl@0:  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
sl@0:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
sl@0:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
sl@0:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
sl@0:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
sl@0:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
sl@0:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
sl@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
sl@0:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
sl@0:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
sl@0:  * SUCH DAMAGE.
sl@0:  * 
sl@0:  * The licence and distribution terms for any publically available version or
sl@0:  * derivative of this code cannot be changed.  i.e. this code cannot simply be
sl@0:  * copied and put under another distribution licence
sl@0:  * [including the GNU Public Licence.]
sl@0:  */
sl@0: /* ====================================================================
sl@0:  * Copyright (c) 1998-2006 The OpenSSL Project.  All rights reserved.
sl@0:  *
sl@0:  * Redistribution and use in source and binary forms, with or without
sl@0:  * modification, are permitted provided that the following conditions
sl@0:  * are met:
sl@0:  *
sl@0:  * 1. Redistributions of source code must retain the above copyright
sl@0:  *    notice, this list of conditions and the following disclaimer. 
sl@0:  *
sl@0:  * 2. Redistributions in binary form must reproduce the above copyright
sl@0:  *    notice, this list of conditions and the following disclaimer in
sl@0:  *    the documentation and/or other materials provided with the
sl@0:  *    distribution.
sl@0:  *
sl@0:  * 3. All advertising materials mentioning features or use of this
sl@0:  *    software must display the following acknowledgment:
sl@0:  *    "This product includes software developed by the OpenSSL Project
sl@0:  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
sl@0:  *
sl@0:  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
sl@0:  *    endorse or promote products derived from this software without
sl@0:  *    prior written permission. For written permission, please contact
sl@0:  *    openssl-core@openssl.org.
sl@0:  *
sl@0:  * 5. Products derived from this software may not be called "OpenSSL"
sl@0:  *    nor may "OpenSSL" appear in their names without prior written
sl@0:  *    permission of the OpenSSL Project.
sl@0:  *
sl@0:  * 6. Redistributions of any form whatsoever must retain the following
sl@0:  *    acknowledgment:
sl@0:  *    "This product includes software developed by the OpenSSL Project
sl@0:  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
sl@0:  *
sl@0:  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
sl@0:  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
sl@0:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
sl@0:  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
sl@0:  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
sl@0:  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
sl@0:  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
sl@0:  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
sl@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
sl@0:  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
sl@0:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
sl@0:  * OF THE POSSIBILITY OF SUCH DAMAGE.
sl@0:  * ====================================================================
sl@0:  *
sl@0:  * This product includes cryptographic software written by Eric Young
sl@0:  * (eay@cryptsoft.com).  This product includes software written by Tim
sl@0:  * Hudson (tjh@cryptsoft.com).
sl@0:  *
sl@0:  */
sl@0: 
sl@0: /*
sl@0:  * Details about Montgomery multiplication algorithms can be found at
sl@0:  * http://security.ece.orst.edu/publications.html, e.g.
sl@0:  * http://security.ece.orst.edu/koc/papers/j37acmon.pdf and
sl@0:  * sections 3.8 and 4.2 in http://security.ece.orst.edu/koc/papers/r01rsasw.pdf
sl@0:  */
sl@0: 
sl@0: #include <stdio.h>
sl@0: #include "cryptlib.h"
sl@0: #include "bn_lcl.h"
sl@0: 
sl@0: #define MONT_WORD /* use the faster word-based algorithm */
sl@0: 
sl@0: EXPORT_C int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
sl@0: 			  BN_MONT_CTX *mont, BN_CTX *ctx)
sl@0: 	{
sl@0: 	BIGNUM *tmp;
sl@0: 	int ret=0;
sl@0: 
sl@0: 	BN_CTX_start(ctx);
sl@0: 	tmp = BN_CTX_get(ctx);
sl@0: 	if (tmp == NULL) goto err;
sl@0: 
sl@0: 	bn_check_top(tmp);
sl@0: 	if (a == b)
sl@0: 		{
sl@0: 		if (!BN_sqr(tmp,a,ctx)) goto err;
sl@0: 		}
sl@0: 	else
sl@0: 		{
sl@0: 		if (!BN_mul(tmp,a,b,ctx)) goto err;
sl@0: 		}
sl@0: 	/* reduce from aRR to aR */
sl@0: 	if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;
sl@0: 	bn_check_top(r);
sl@0: 	ret=1;
sl@0: err:
sl@0: 	BN_CTX_end(ctx);
sl@0: 	return(ret);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont,
sl@0: 	     BN_CTX *ctx)
sl@0: 	{
sl@0: 	int retn=0;
sl@0: 
sl@0: #ifdef MONT_WORD
sl@0: 	BIGNUM *n,*r;
sl@0: 	BN_ULONG *ap,*np,*rp,n0,v,*nrp;
sl@0: 	int al,nl,max,i,x,ri;
sl@0: 
sl@0: 	BN_CTX_start(ctx);
sl@0: 	if ((r = BN_CTX_get(ctx)) == NULL) goto err;
sl@0: 
sl@0: 	if (!BN_copy(r,a)) goto err;
sl@0: 	n= &(mont->N);
sl@0: 
sl@0: 	ap=a->d;
sl@0: 	/* mont->ri is the size of mont->N in bits (rounded up
sl@0: 	   to the word size) */
sl@0: 	al=ri=mont->ri/BN_BITS2;
sl@0: 	
sl@0: 	nl=n->top;
sl@0: 	if ((al == 0) || (nl == 0)) { r->top=0; return(1); }
sl@0: 
sl@0: 	max=(nl+al+1); /* allow for overflow (no?) XXX */
sl@0: 	if (bn_wexpand(r,max) == NULL) goto err;
sl@0: 
sl@0: 	r->neg=a->neg^n->neg;
sl@0: 	np=n->d;
sl@0: 	rp=r->d;
sl@0: 	nrp= &(r->d[nl]);
sl@0: 
sl@0: 	/* clear the top words of T */
sl@0: #if 1
sl@0: 	for (i=r->top; i<max; i++) /* memset? XXX */
sl@0: 		r->d[i]=0;
sl@0: #else
sl@0: 	memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG)); 
sl@0: #endif
sl@0: 
sl@0: 	r->top=max;
sl@0: 	n0=mont->n0;
sl@0: 
sl@0: #ifdef BN_COUNT
sl@0: 	fprintf(stderr,"word BN_from_montgomery %d * %d\n",nl,nl);
sl@0: #endif
sl@0: 	for (i=0; i<nl; i++)
sl@0: 		{
sl@0: #ifdef __TANDEM
sl@0:                 {
sl@0:                    long long t1;
sl@0:                    long long t2;
sl@0:                    long long t3;
sl@0:                    t1 = rp[0] * (n0 & 0177777);
sl@0:                    t2 = 037777600000l;
sl@0:                    t2 = n0 & t2;
sl@0:                    t3 = rp[0] & 0177777;
sl@0:                    t2 = (t3 * t2) & BN_MASK2;
sl@0:                    t1 = t1 + t2;
sl@0:                    v=bn_mul_add_words(rp,np,nl,(BN_ULONG) t1);
sl@0:                 }
sl@0: #else
sl@0: 		v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2);
sl@0: #endif
sl@0: 		nrp++;
sl@0: 		rp++;
sl@0: 		if (((nrp[-1]+=v)&BN_MASK2) >= v)
sl@0: 			continue;
sl@0: 		else
sl@0: 			{
sl@0: 			if (((++nrp[0])&BN_MASK2) != 0) continue;
sl@0: 			if (((++nrp[1])&BN_MASK2) != 0) continue;
sl@0: 			for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ;
sl@0: 			}
sl@0: 		}
sl@0: 	bn_correct_top(r);
sl@0: 	
sl@0: 	/* mont->ri will be a multiple of the word size and below code
sl@0: 	 * is kind of BN_rshift(ret,r,mont->ri) equivalent */
sl@0: 	if (r->top <= ri)
sl@0: 		{
sl@0: 		ret->top=0;
sl@0: 		retn=1;
sl@0: 		goto err;
sl@0: 		}
sl@0: 	al=r->top-ri;
sl@0: 
sl@0: # define BRANCH_FREE 1
sl@0: # if BRANCH_FREE
sl@0: 	if (bn_wexpand(ret,ri) == NULL) goto err;
sl@0: 	x=0-(((al-ri)>>(sizeof(al)*8-1))&1);
sl@0: 	ret->top=x=(ri&~x)|(al&x);	/* min(ri,al) */
sl@0: 	ret->neg=r->neg;
sl@0: 
sl@0: 	rp=ret->d;
sl@0: 	ap=&(r->d[ri]);
sl@0: 
sl@0: 	{
sl@0: 	size_t m1,m2;
sl@0: 
sl@0: 	v=bn_sub_words(rp,ap,np,ri);
sl@0: 	/* this ----------------^^ works even in al<ri case
sl@0: 	 * thanks to zealous zeroing of top of the vector in the
sl@0: 	 * beginning. */
sl@0: 
sl@0: 	/* if (al==ri && !v) || al>ri) nrp=rp; else nrp=ap; */
sl@0: 	/* in other words if subtraction result is real, then
sl@0: 	 * trick unconditional memcpy below to perform in-place
sl@0: 	 * "refresh" instead of actual copy. */
sl@0: 	m1=0-(size_t)(((al-ri)>>(sizeof(al)*8-1))&1);	/* al<ri */
sl@0: 	m2=0-(size_t)(((ri-al)>>(sizeof(al)*8-1))&1);	/* al>ri */
sl@0: 	m1|=m2;			/* (al!=ri) */
sl@0: 	m1|=(0-(size_t)v);	/* (al!=ri || v) */
sl@0: 	m1&=~m2;		/* (al!=ri || v) && !al>ri */
sl@0: 	nrp=(BN_ULONG *)(((size_t)rp&~m1)|((size_t)ap&m1));
sl@0: 	}
sl@0: 
sl@0: 	/* 'i<ri' is chosen to eliminate dependency on input data, even
sl@0: 	 * though it results in redundant copy in al<ri case. */
sl@0: 	for (i=0,ri-=4; i<ri; i+=4)
sl@0: 		{
sl@0: 		BN_ULONG t1,t2,t3,t4;
sl@0: 		
sl@0: 		t1=nrp[i+0];
sl@0: 		t2=nrp[i+1];
sl@0: 		t3=nrp[i+2];	ap[i+0]=0;
sl@0: 		t4=nrp[i+3];	ap[i+1]=0;
sl@0: 		rp[i+0]=t1;	ap[i+2]=0;
sl@0: 		rp[i+1]=t2;	ap[i+3]=0;
sl@0: 		rp[i+2]=t3;
sl@0: 		rp[i+3]=t4;
sl@0: 		}
sl@0: 	for (ri+=4; i<ri; i++)
sl@0: 		rp[i]=nrp[i], ap[i]=0;
sl@0: 	bn_correct_top(r);
sl@0: 	bn_correct_top(ret);
sl@0: # else
sl@0: 	if (bn_wexpand(ret,al) == NULL) goto err;
sl@0: 	ret->top=al;
sl@0: 	ret->neg=r->neg;
sl@0: 
sl@0: 	rp=ret->d;
sl@0: 	ap=&(r->d[ri]);
sl@0: 	al-=4;
sl@0: 	for (i=0; i<al; i+=4)
sl@0: 		{
sl@0: 		BN_ULONG t1,t2,t3,t4;
sl@0: 		
sl@0: 		t1=ap[i+0];
sl@0: 		t2=ap[i+1];
sl@0: 		t3=ap[i+2];
sl@0: 		t4=ap[i+3];
sl@0: 		rp[i+0]=t1;
sl@0: 		rp[i+1]=t2;
sl@0: 		rp[i+2]=t3;
sl@0: 		rp[i+3]=t4;
sl@0: 		}
sl@0: 	al+=4;
sl@0: 	for (; i<al; i++)
sl@0: 		rp[i]=ap[i];
sl@0: #endif
sl@0: #else /* !MONT_WORD */ 
sl@0: 	BIGNUM *t1,*t2;
sl@0: 
sl@0: 	BN_CTX_start(ctx);
sl@0: 	t1 = BN_CTX_get(ctx);
sl@0: 	t2 = BN_CTX_get(ctx);
sl@0: 	if (t1 == NULL || t2 == NULL) goto err;
sl@0: 	
sl@0: 	if (!BN_copy(t1,a)) goto err;
sl@0: 	BN_mask_bits(t1,mont->ri);
sl@0: 
sl@0: 	if (!BN_mul(t2,t1,&mont->Ni,ctx)) goto err;
sl@0: 	BN_mask_bits(t2,mont->ri);
sl@0: 
sl@0: 	if (!BN_mul(t1,t2,&mont->N,ctx)) goto err;
sl@0: 	if (!BN_add(t2,a,t1)) goto err;
sl@0: 	if (!BN_rshift(ret,t2,mont->ri)) goto err;
sl@0: #endif /* MONT_WORD */
sl@0: 
sl@0: #if !defined(BRANCH_FREE) || BRANCH_FREE==0
sl@0: 	if (BN_ucmp(ret, &(mont->N)) >= 0)
sl@0: 		{
sl@0: 		if (!BN_usub(ret,ret,&(mont->N))) goto err;
sl@0: 		}
sl@0: #endif
sl@0: 	retn=1;
sl@0: 	bn_check_top(ret);
sl@0:  err:
sl@0: 	BN_CTX_end(ctx);
sl@0: 	return(retn);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C BN_MONT_CTX *BN_MONT_CTX_new(void)
sl@0: 	{
sl@0: 	BN_MONT_CTX *ret;
sl@0: 
sl@0: 	if ((ret=(BN_MONT_CTX *)OPENSSL_malloc(sizeof(BN_MONT_CTX))) == NULL)
sl@0: 		return(NULL);
sl@0: 
sl@0: 	BN_MONT_CTX_init(ret);
sl@0: 	ret->flags=BN_FLG_MALLOCED;
sl@0: 	return(ret);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C void BN_MONT_CTX_init(BN_MONT_CTX *ctx)
sl@0: 	{
sl@0: 	ctx->ri=0;
sl@0: 	BN_init(&(ctx->RR));
sl@0: 	BN_init(&(ctx->N));
sl@0: 	BN_init(&(ctx->Ni));
sl@0: 	ctx->flags=0;
sl@0: 	}
sl@0: 
sl@0: EXPORT_C void BN_MONT_CTX_free(BN_MONT_CTX *mont)
sl@0: 	{
sl@0: 	if(mont == NULL)
sl@0: 	    return;
sl@0: 
sl@0: 	BN_free(&(mont->RR));
sl@0: 	BN_free(&(mont->N));
sl@0: 	BN_free(&(mont->Ni));
sl@0: 	if (mont->flags & BN_FLG_MALLOCED)
sl@0: 		OPENSSL_free(mont);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
sl@0: 	{
sl@0: 	int ret = 0;
sl@0: 	BIGNUM *Ri,*R;
sl@0: 
sl@0: 	BN_CTX_start(ctx);
sl@0: 	if((Ri = BN_CTX_get(ctx)) == NULL) goto err;
sl@0: 	R= &(mont->RR);					/* grab RR as a temp */
sl@0: 	if (!BN_copy(&(mont->N),mod)) goto err;		/* Set N */
sl@0: 	mont->N.neg = 0;
sl@0: 
sl@0: #ifdef MONT_WORD
sl@0: 		{
sl@0: 		BIGNUM tmod;
sl@0: 		BN_ULONG buf[2];
sl@0: 
sl@0: 		mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
sl@0: 		BN_zero(R);
sl@0: 		if (!(BN_set_bit(R,BN_BITS2))) goto err;	/* R */
sl@0: 
sl@0: 		buf[0]=mod->d[0]; /* tmod = N mod word size */
sl@0: 		buf[1]=0;
sl@0: 		tmod.d=buf;
sl@0: 		tmod.top = buf[0] != 0 ? 1 : 0;
sl@0: 		tmod.dmax=2;
sl@0: 		tmod.neg=0;
sl@0: 							/* Ri = R^-1 mod N*/
sl@0: 		if ((BN_mod_inverse(Ri,R,&tmod,ctx)) == NULL)
sl@0: 			goto err;
sl@0: 		if (!BN_lshift(Ri,Ri,BN_BITS2)) goto err; /* R*Ri */
sl@0: 		if (!BN_is_zero(Ri))
sl@0: 			{
sl@0: 			if (!BN_sub_word(Ri,1)) goto err;
sl@0: 			}
sl@0: 		else /* if N mod word size == 1 */
sl@0: 			{
sl@0: 			if (!BN_set_word(Ri,BN_MASK2)) goto err;  /* Ri-- (mod word size) */
sl@0: 			}
sl@0: 		if (!BN_div(Ri,NULL,Ri,&tmod,ctx)) goto err;
sl@0: 		/* Ni = (R*Ri-1)/N,
sl@0: 		 * keep only least significant word: */
sl@0: 		mont->n0 = (Ri->top > 0) ? Ri->d[0] : 0;
sl@0: 		}
sl@0: #else /* !MONT_WORD */
sl@0: 		{ /* bignum version */
sl@0: 		mont->ri=BN_num_bits(&mont->N);
sl@0: 		BN_zero(R);
sl@0: 		if (!BN_set_bit(R,mont->ri)) goto err;  /* R = 2^ri */
sl@0: 		                                        /* Ri = R^-1 mod N*/
sl@0: 		if ((BN_mod_inverse(Ri,R,&mont->N,ctx)) == NULL)
sl@0: 			goto err;
sl@0: 		if (!BN_lshift(Ri,Ri,mont->ri)) goto err; /* R*Ri */
sl@0: 		if (!BN_sub_word(Ri,1)) goto err;
sl@0: 							/* Ni = (R*Ri-1) / N */
sl@0: 		if (!BN_div(&(mont->Ni),NULL,Ri,&mont->N,ctx)) goto err;
sl@0: 		}
sl@0: #endif
sl@0: 
sl@0: 	/* setup RR for conversions */
sl@0: 	BN_zero(&(mont->RR));
sl@0: 	if (!BN_set_bit(&(mont->RR),mont->ri*2)) goto err;
sl@0: 	if (!BN_mod(&(mont->RR),&(mont->RR),&(mont->N),ctx)) goto err;
sl@0: 
sl@0: 	ret = 1;
sl@0: err:
sl@0: 	BN_CTX_end(ctx);
sl@0: 	return ret;
sl@0: 	}
sl@0: 
sl@0: EXPORT_C BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from)
sl@0: 	{
sl@0: 	if (to == from) return(to);
sl@0: 
sl@0: 	if (!BN_copy(&(to->RR),&(from->RR))) return NULL;
sl@0: 	if (!BN_copy(&(to->N),&(from->N))) return NULL;
sl@0: 	if (!BN_copy(&(to->Ni),&(from->Ni))) return NULL;
sl@0: 	to->ri=from->ri;
sl@0: 	to->n0=from->n0;
sl@0: 	return(to);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C BN_MONT_CTX *BN_MONT_CTX_set_locked(BN_MONT_CTX **pmont, int lock,
sl@0: 					const BIGNUM *mod, BN_CTX *ctx)
sl@0: 	{
sl@0: 		int got_write_lock = 0;
sl@0: 	BN_MONT_CTX *ret;
sl@0: 
sl@0: 	CRYPTO_r_lock(lock);
sl@0: 	if (!*pmont)
sl@0: 		{
sl@0: 		CRYPTO_r_unlock(lock);
sl@0: 		CRYPTO_w_lock(lock);
sl@0: 		got_write_lock = 1;
sl@0: 
sl@0: 		if (!*pmont)
sl@0: 			{
sl@0: 			ret = BN_MONT_CTX_new();
sl@0: 			if (ret && !BN_MONT_CTX_set(ret, mod, ctx))
sl@0: 				BN_MONT_CTX_free(ret);
sl@0: 			else
sl@0: 				*pmont = ret;
sl@0: 			}
sl@0: 		}
sl@0: 	
sl@0: 	ret = *pmont;
sl@0: 	
sl@0: 	if (got_write_lock)
sl@0: 		CRYPTO_w_unlock(lock);
sl@0: 	else
sl@0: 		CRYPTO_r_unlock(lock);
sl@0: 		
sl@0: 	return ret;
sl@0: 	}