/* crypto/bn/bn_mont.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.] */ /* ==================================================================== * Copyright (c) 1998-2006 The OpenSSL Project. All rights reserved. * * 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 above 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 acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" * * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to * endorse or promote products derived from this software without * prior written permission. For written permission, please contact * openssl-core@openssl.org. * * 5. Products derived from this software may not be called "OpenSSL" * nor may "OpenSSL" appear in their names without prior written * permission of the OpenSSL Project. * * 6. Redistributions of any form whatsoever must retain the following * acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit (http://www.openssl.org/)" * * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY * EXPRESSED 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 OpenSSL PROJECT OR * ITS 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. * ==================================================================== * * This product includes cryptographic software written by Eric Young * (eay@cryptsoft.com). This product includes software written by Tim * Hudson (tjh@cryptsoft.com). * */ /* * Details about Montgomery multiplication algorithms can be found at * http://security.ece.orst.edu/publications.html, e.g. * http://security.ece.orst.edu/koc/papers/j37acmon.pdf and * sections 3.8 and 4.2 in http://security.ece.orst.edu/koc/papers/r01rsasw.pdf */ #include <stdio.h> #include "cryptlib.h" #include "bn_lcl.h" #define MONT_WORD /* use the faster word-based algorithm */ #if defined(MONT_WORD) && defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32) /* This condition means we have a specific non-default build: * In the 0.9.8 branch, OPENSSL_BN_ASM_MONT is normally not set for any * BN_BITS2<=32 platform; an explicit "enable-montasm" is required. * I.e., if we are here, the user intentionally deviates from the * normal stable build to get better Montgomery performance from * the 0.9.9-dev backport. * * In this case only, we also enable BN_from_montgomery_word() * (another non-stable feature from 0.9.9-dev). */ #define MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD #endif #ifdef MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont); #endif int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_MONT_CTX *mont, BN_CTX *ctx) { BIGNUM *tmp; int ret=0; #if defined(OPENSSL_BN_ASM_MONT) && defined(MONT_WORD) int num = mont->N.top; if (num>1 && a->top==num && b->top==num) { if (bn_wexpand(r,num) == NULL) return(0); #if 0 /* for OpenSSL 0.9.9 mont->n0 */ if (bn_mul_mont(r->d,a->d,b->d,mont->N.d,mont->n0,num)) #else if (bn_mul_mont(r->d,a->d,b->d,mont->N.d,&mont->n0,num)) #endif { r->neg = a->neg^b->neg; r->top = num; bn_correct_top(r); return(1); } } #endif BN_CTX_start(ctx); tmp = BN_CTX_get(ctx); if (tmp == NULL) goto err; bn_check_top(tmp); if (a == b) { if (!BN_sqr(tmp,a,ctx)) goto err; } else { if (!BN_mul(tmp,a,b,ctx)) goto err; } /* reduce from aRR to aR */ #ifdef MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD if (!BN_from_montgomery_word(r,tmp,mont)) goto err; #else if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err; #endif bn_check_top(r); ret=1; err: BN_CTX_end(ctx); return(ret); } #ifdef MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont) { BIGNUM *n; BN_ULONG *ap,*np,*rp,n0,v,*nrp; int al,nl,max,i,x,ri; n= &(mont->N); /* mont->ri is the size of mont->N in bits (rounded up to the word size) */ al=ri=mont->ri/BN_BITS2; nl=n->top; if ((al == 0) || (nl == 0)) { ret->top=0; return(1); } max=(nl+al+1); /* allow for overflow (no?) XXX */ if (bn_wexpand(r,max) == NULL) return(0); r->neg^=n->neg; np=n->d; rp=r->d; nrp= &(r->d[nl]); /* clear the top words of T */ for (i=r->top; i<max; i++) /* memset? XXX */ r->d[i]=0; r->top=max; #if 0 /* for OpenSSL 0.9.9 mont->n0 */ n0=mont->n0[0]; #else n0=mont->n0; #endif #ifdef BN_COUNT fprintf(stderr,"word BN_from_montgomery_word %d * %d\n",nl,nl); #endif for (i=0; i<nl; i++) { #ifdef __TANDEM { long long t1; long long t2; long long t3; t1 = rp[0] * (n0 & 0177777); t2 = 037777600000l; t2 = n0 & t2; t3 = rp[0] & 0177777; t2 = (t3 * t2) & BN_MASK2; t1 = t1 + t2; v=bn_mul_add_words(rp,np,nl,(BN_ULONG) t1); } #else v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2); #endif nrp++; rp++; if (((nrp[-1]+=v)&BN_MASK2) >= v) continue; else { if (((++nrp[0])&BN_MASK2) != 0) continue; if (((++nrp[1])&BN_MASK2) != 0) continue; for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ; } } bn_correct_top(r); /* mont->ri will be a multiple of the word size and below code * is kind of BN_rshift(ret,r,mont->ri) equivalent */ if (r->top <= ri) { ret->top=0; return(1); } al=r->top-ri; if (bn_wexpand(ret,ri) == NULL) return(0); x=0-(((al-ri)>>(sizeof(al)*8-1))&1); ret->top=x=(ri&~x)|(al&x); /* min(ri,al) */ ret->neg=r->neg; rp=ret->d; ap=&(r->d[ri]); { size_t m1,m2; v=bn_sub_words(rp,ap,np,ri); /* this ----------------^^ works even in al<ri case * thanks to zealous zeroing of top of the vector in the * beginning. */ /* if (al==ri && !v) || al>ri) nrp=rp; else nrp=ap; */ /* in other words if subtraction result is real, then * trick unconditional memcpy below to perform in-place * "refresh" instead of actual copy. */ m1=0-(size_t)(((al-ri)>>(sizeof(al)*8-1))&1); /* al<ri */ m2=0-(size_t)(((ri-al)>>(sizeof(al)*8-1))&1); /* al>ri */ m1|=m2; /* (al!=ri) */ m1|=(0-(size_t)v); /* (al!=ri || v) */ m1&=~m2; /* (al!=ri || v) && !al>ri */ nrp=(BN_ULONG *)(((size_t)rp&~m1)|((size_t)ap&m1)); } /* 'i<ri' is chosen to eliminate dependency on input data, even * though it results in redundant copy in al<ri case. */ for (i=0,ri-=4; i<ri; i+=4) { BN_ULONG t1,t2,t3,t4; t1=nrp[i+0]; t2=nrp[i+1]; t3=nrp[i+2]; ap[i+0]=0; t4=nrp[i+3]; ap[i+1]=0; rp[i+0]=t1; ap[i+2]=0; rp[i+1]=t2; ap[i+3]=0; rp[i+2]=t3; rp[i+3]=t4; } for (ri+=4; i<ri; i++) rp[i]=nrp[i], ap[i]=0; bn_correct_top(r); bn_correct_top(ret); bn_check_top(ret); return(1); } int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, BN_CTX *ctx) { int retn=0; BIGNUM *t; BN_CTX_start(ctx); if ((t = BN_CTX_get(ctx)) && BN_copy(t,a)) retn = BN_from_montgomery_word(ret,t,mont); BN_CTX_end(ctx); return retn; } #else /* !MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD */ int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, BN_CTX *ctx) { int retn=0; #ifdef MONT_WORD BIGNUM *n,*r; BN_ULONG *ap,*np,*rp,n0,v,*nrp; int al,nl,max,i,x,ri; BN_CTX_start(ctx); if ((r = BN_CTX_get(ctx)) == NULL) goto err; if (!BN_copy(r,a)) goto err; n= &(mont->N); ap=a->d; /* mont->ri is the size of mont->N in bits (rounded up to the word size) */ al=ri=mont->ri/BN_BITS2; nl=n->top; if ((al == 0) || (nl == 0)) { r->top=0; return(1); } max=(nl+al+1); /* allow for overflow (no?) XXX */ if (bn_wexpand(r,max) == NULL) goto err; r->neg=a->neg^n->neg; np=n->d; rp=r->d; nrp= &(r->d[nl]); /* clear the top words of T */ #if 1 for (i=r->top; i<max; i++) /* memset? XXX */ r->d[i]=0; #else memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG)); #endif r->top=max; n0=mont->n0; #ifdef BN_COUNT fprintf(stderr,"word BN_from_montgomery %d * %d\n",nl,nl); #endif for (i=0; i<nl; i++) { #ifdef __TANDEM { long long t1; long long t2; long long t3; t1 = rp[0] * (n0 & 0177777); t2 = 037777600000l; t2 = n0 & t2; t3 = rp[0] & 0177777; t2 = (t3 * t2) & BN_MASK2; t1 = t1 + t2; v=bn_mul_add_words(rp,np,nl,(BN_ULONG) t1); } #else v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2); #endif nrp++; rp++; if (((nrp[-1]+=v)&BN_MASK2) >= v) continue; else { if (((++nrp[0])&BN_MASK2) != 0) continue; if (((++nrp[1])&BN_MASK2) != 0) continue; for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ; } } bn_correct_top(r); /* mont->ri will be a multiple of the word size and below code * is kind of BN_rshift(ret,r,mont->ri) equivalent */ if (r->top <= ri) { ret->top=0; retn=1; goto err; } al=r->top-ri; # define BRANCH_FREE 1 # if BRANCH_FREE if (bn_wexpand(ret,ri) == NULL) goto err; x=0-(((al-ri)>>(sizeof(al)*8-1))&1); ret->top=x=(ri&~x)|(al&x); /* min(ri,al) */ ret->neg=r->neg; rp=ret->d; ap=&(r->d[ri]); { size_t m1,m2; v=bn_sub_words(rp,ap,np,ri); /* this ----------------^^ works even in al<ri case * thanks to zealous zeroing of top of the vector in the * beginning. */ /* if (al==ri && !v) || al>ri) nrp=rp; else nrp=ap; */ /* in other words if subtraction result is real, then * trick unconditional memcpy below to perform in-place * "refresh" instead of actual copy. */ m1=0-(size_t)(((al-ri)>>(sizeof(al)*8-1))&1); /* al<ri */ m2=0-(size_t)(((ri-al)>>(sizeof(al)*8-1))&1); /* al>ri */ m1|=m2; /* (al!=ri) */ m1|=(0-(size_t)v); /* (al!=ri || v) */ m1&=~m2; /* (al!=ri || v) && !al>ri */ nrp=(BN_ULONG *)(((size_t)rp&~m1)|((size_t)ap&m1)); } /* 'i<ri' is chosen to eliminate dependency on input data, even * though it results in redundant copy in al<ri case. */ for (i=0,ri-=4; i<ri; i+=4) { BN_ULONG t1,t2,t3,t4; t1=nrp[i+0]; t2=nrp[i+1]; t3=nrp[i+2]; ap[i+0]=0; t4=nrp[i+3]; ap[i+1]=0; rp[i+0]=t1; ap[i+2]=0; rp[i+1]=t2; ap[i+3]=0; rp[i+2]=t3; rp[i+3]=t4; } for (ri+=4; i<ri; i++) rp[i]=nrp[i], ap[i]=0; bn_correct_top(r); bn_correct_top(ret); # else if (bn_wexpand(ret,al) == NULL) goto err; ret->top=al; ret->neg=r->neg; rp=ret->d; ap=&(r->d[ri]); al-=4; for (i=0; i<al; i+=4) { BN_ULONG t1,t2,t3,t4; t1=ap[i+0]; t2=ap[i+1]; t3=ap[i+2]; t4=ap[i+3]; rp[i+0]=t1; rp[i+1]=t2; rp[i+2]=t3; rp[i+3]=t4; } al+=4; for (; i<al; i++) rp[i]=ap[i]; # endif #else /* !MONT_WORD */ BIGNUM *t1,*t2; BN_CTX_start(ctx); t1 = BN_CTX_get(ctx); t2 = BN_CTX_get(ctx); if (t1 == NULL || t2 == NULL) goto err; if (!BN_copy(t1,a)) goto err; BN_mask_bits(t1,mont->ri); if (!BN_mul(t2,t1,&mont->Ni,ctx)) goto err; BN_mask_bits(t2,mont->ri); if (!BN_mul(t1,t2,&mont->N,ctx)) goto err; if (!BN_add(t2,a,t1)) goto err; if (!BN_rshift(ret,t2,mont->ri)) goto err; #endif /* MONT_WORD */ #if !defined(BRANCH_FREE) || BRANCH_FREE==0 if (BN_ucmp(ret, &(mont->N)) >= 0) { if (!BN_usub(ret,ret,&(mont->N))) goto err; } #endif retn=1; bn_check_top(ret); err: BN_CTX_end(ctx); return(retn); } #endif /* MONT_FROM_WORD___NON_DEFAULT_0_9_8_BUILD */ BN_MONT_CTX *BN_MONT_CTX_new(void) { BN_MONT_CTX *ret; if ((ret=(BN_MONT_CTX *)OPENSSL_malloc(sizeof(BN_MONT_CTX))) == NULL) return(NULL); BN_MONT_CTX_init(ret); ret->flags=BN_FLG_MALLOCED; return(ret); } void BN_MONT_CTX_init(BN_MONT_CTX *ctx) { ctx->ri=0; BN_init(&(ctx->RR)); BN_init(&(ctx->N)); BN_init(&(ctx->Ni)); #if 0 /* for OpenSSL 0.9.9 mont->n0 */ ctx->n0[0] = ctx->n0[1] = 0; #else ctx->n0 = 0; #endif ctx->flags=0; } void BN_MONT_CTX_free(BN_MONT_CTX *mont) { if(mont == NULL) return; BN_free(&(mont->RR)); BN_free(&(mont->N)); BN_free(&(mont->Ni)); if (mont->flags & BN_FLG_MALLOCED) OPENSSL_free(mont); } int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx) { int ret = 0; BIGNUM *Ri,*R; BN_CTX_start(ctx); if((Ri = BN_CTX_get(ctx)) == NULL) goto err; R= &(mont->RR); /* grab RR as a temp */ if (!BN_copy(&(mont->N),mod)) goto err; /* Set N */ mont->N.neg = 0; #ifdef MONT_WORD { BIGNUM tmod; BN_ULONG buf[2]; mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2; BN_zero(R); #if 0 /* for OpenSSL 0.9.9 mont->n0, would be "#if defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)", only certain BN_BITS2<=32 platforms actually need this */ if (!(BN_set_bit(R,2*BN_BITS2))) goto err; /* R */ #else if (!(BN_set_bit(R,BN_BITS2))) goto err; /* R */ #endif buf[0]=mod->d[0]; /* tmod = N mod word size */ buf[1]=0; BN_init(&tmod); tmod.d=buf; tmod.top = buf[0] != 0 ? 1 : 0; tmod.dmax=2; tmod.neg=0; #if 0 /* for OpenSSL 0.9.9 mont->n0, would be "#if defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)"; only certain BN_BITS2<=32 platforms actually need this */ tmod.top=0; if ((buf[0] = mod->d[0])) tmod.top=1; if ((buf[1] = mod->top>1 ? mod->d[1] : 0)) tmod.top=2; if ((BN_mod_inverse(Ri,R,&tmod,ctx)) == NULL) goto err; if (!BN_lshift(Ri,Ri,2*BN_BITS2)) goto err; /* R*Ri */ if (!BN_is_zero(Ri)) { if (!BN_sub_word(Ri,1)) goto err; } else /* if N mod word size == 1 */ { if (bn_expand(Ri,(int)sizeof(BN_ULONG)*2) == NULL) goto err; /* Ri-- (mod double word size) */ Ri->neg=0; Ri->d[0]=BN_MASK2; Ri->d[1]=BN_MASK2; Ri->top=2; } if (!BN_div(Ri,NULL,Ri,&tmod,ctx)) goto err; /* Ni = (R*Ri-1)/N, * keep only couple of least significant words: */ mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0; mont->n0[1] = (Ri->top > 1) ? Ri->d[1] : 0; #else /* Ri = R^-1 mod N*/ if ((BN_mod_inverse(Ri,R,&tmod,ctx)) == NULL) goto err; if (!BN_lshift(Ri,Ri,BN_BITS2)) goto err; /* R*Ri */ if (!BN_is_zero(Ri)) { if (!BN_sub_word(Ri,1)) goto err; } else /* if N mod word size == 1 */ { if (!BN_set_word(Ri,BN_MASK2)) goto err; /* Ri-- (mod word size) */ } if (!BN_div(Ri,NULL,Ri,&tmod,ctx)) goto err; /* Ni = (R*Ri-1)/N, * keep only least significant word: */ # if 0 /* for OpenSSL 0.9.9 mont->n0 */ mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0; mont->n0[1] = 0; # else mont->n0 = (Ri->top > 0) ? Ri->d[0] : 0; # endif #endif } #else /* !MONT_WORD */ { /* bignum version */ mont->ri=BN_num_bits(&mont->N); BN_zero(R); if (!BN_set_bit(R,mont->ri)) goto err; /* R = 2^ri */ /* Ri = R^-1 mod N*/ if ((BN_mod_inverse(Ri,R,&mont->N,ctx)) == NULL) goto err; if (!BN_lshift(Ri,Ri,mont->ri)) goto err; /* R*Ri */ if (!BN_sub_word(Ri,1)) goto err; /* Ni = (R*Ri-1) / N */ if (!BN_div(&(mont->Ni),NULL,Ri,&mont->N,ctx)) goto err; } #endif /* setup RR for conversions */ BN_zero(&(mont->RR)); if (!BN_set_bit(&(mont->RR),mont->ri*2)) goto err; if (!BN_mod(&(mont->RR),&(mont->RR),&(mont->N),ctx)) goto err; ret = 1; err: BN_CTX_end(ctx); return ret; } BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from) { if (to == from) return(to); if (!BN_copy(&(to->RR),&(from->RR))) return NULL; if (!BN_copy(&(to->N),&(from->N))) return NULL; if (!BN_copy(&(to->Ni),&(from->Ni))) return NULL; to->ri=from->ri; #if 0 /* for OpenSSL 0.9.9 mont->n0 */ to->n0[0]=from->n0[0]; to->n0[1]=from->n0[1]; #else to->n0=from->n0; #endif return(to); } BN_MONT_CTX *BN_MONT_CTX_set_locked(BN_MONT_CTX **pmont, int lock, const BIGNUM *mod, BN_CTX *ctx) { int got_write_lock = 0; BN_MONT_CTX *ret; CRYPTO_r_lock(lock); if (!*pmont) { CRYPTO_r_unlock(lock); CRYPTO_w_lock(lock); got_write_lock = 1; if (!*pmont) { ret = BN_MONT_CTX_new(); if (ret && !BN_MONT_CTX_set(ret, mod, ctx)) BN_MONT_CTX_free(ret); else *pmont = ret; } } ret = *pmont; if (got_write_lock) CRYPTO_w_unlock(lock); else CRYPTO_r_unlock(lock); return ret; }