X-Git-Url: https://git.openssl.org/?p=openssl.git;a=blobdiff_plain;f=crypto%2Fbn%2Fbn_div.c;h=034a80a4a63f5f363b142e0cd53925971e8322fa;hp=2263bdc7da083a7ce998e1d405b6c2a187a6b8c3;hb=134c00659a1bc67ad35a1e4620e16bc4315e6e37;hpb=7dfb0b774e6592dcbfe47015168a0ac8b44e2a17 diff --git a/crypto/bn/bn_div.c b/crypto/bn/bn_div.c index 2263bdc7da..034a80a4a6 100644 --- a/crypto/bn/bn_div.c +++ b/crypto/bn/bn_div.c @@ -56,22 +56,25 @@ * [including the GNU Public Licence.] */ +#define OPENSSL_FIPSAPI + #include +#include #include "cryptlib.h" #include "bn_lcl.h" + /* The old slow way */ #if 0 -int BN_div(dv, rem, m, d,ctx) -BIGNUM *dv; -BIGNUM *rem; -BIGNUM *m; -BIGNUM *d; -BN_CTX *ctx; +int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, + BN_CTX *ctx) { int i,nm,nd; + int ret = 0; BIGNUM *D; + bn_check_top(m); + bn_check_top(d); if (BN_is_zero(d)) { BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO); @@ -86,51 +89,127 @@ BN_CTX *ctx; return(1); } - D=ctx->bn[ctx->tos]; - if (dv == NULL) dv=ctx->bn[ctx->tos+1]; - if (rem == NULL) rem=ctx->bn[ctx->tos+2]; + BN_CTX_start(ctx); + D = BN_CTX_get(ctx); + if (dv == NULL) dv = BN_CTX_get(ctx); + if (rem == NULL) rem = BN_CTX_get(ctx); + if (D == NULL || dv == NULL || rem == NULL) + goto end; nd=BN_num_bits(d); nm=BN_num_bits(m); - if (BN_copy(D,d) == NULL) return(0); - if (BN_copy(rem,m) == NULL) return(0); + if (BN_copy(D,d) == NULL) goto end; + if (BN_copy(rem,m) == NULL) goto end; /* The next 2 are needed so we can do a dv->d[0]|=1 later * since BN_lshift1 will only work once there is a value :-) */ BN_zero(dv); + if(bn_wexpand(dv,1) == NULL) goto end; dv->top=1; - if (!BN_lshift(D,D,nm-nd)) return(0); + if (!BN_lshift(D,D,nm-nd)) goto end; for (i=nm-nd; i>=0; i--) { - if (!BN_lshift1(dv,dv)) return(0); + if (!BN_lshift1(dv,dv)) goto end; if (BN_ucmp(rem,D) >= 0) { dv->d[0]|=1; - bn_qsub(rem,rem,D); + if (!BN_usub(rem,rem,D)) goto end; } /* CAN IMPROVE (and have now :=) */ - if (!BN_rshift1(D,D)) return(0); + if (!BN_rshift1(D,D)) goto end; } rem->neg=BN_is_zero(rem)?0:m->neg; dv->neg=m->neg^d->neg; - return(1); + ret = 1; + end: + BN_CTX_end(ctx); + return(ret); } #else -int BN_div(dv, rm, num, divisor,ctx) -BIGNUM *dv; -BIGNUM *rm; -BIGNUM *num; -BIGNUM *divisor; -BN_CTX *ctx; +#if !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_NO_INLINE_ASM) \ + && !defined(PEDANTIC) && !defined(BN_DIV3W) +# if defined(__GNUC__) && __GNUC__>=2 +# if defined(__i386) || defined (__i386__) + /* + * There were two reasons for implementing this template: + * - GNU C generates a call to a function (__udivdi3 to be exact) + * in reply to ((((BN_ULLONG)n0)< + */ +#undef bn_div_words +# define bn_div_words(n0,n1,d0) \ + ({ asm volatile ( \ + "divl %4" \ + : "=a"(q), "=d"(rem) \ + : "a"(n1), "d"(n0), "g"(d0) \ + : "cc"); \ + q; \ + }) +# define REMAINDER_IS_ALREADY_CALCULATED +# elif defined(__x86_64) && defined(SIXTY_FOUR_BIT_LONG) + /* + * Same story here, but it's 128-bit by 64-bit division. Wow! + * + */ +# undef bn_div_words +# define bn_div_words(n0,n1,d0) \ + ({ asm volatile ( \ + "divq %4" \ + : "=a"(q), "=d"(rem) \ + : "a"(n1), "d"(n0), "g"(d0) \ + : "cc"); \ + q; \ + }) +# define REMAINDER_IS_ALREADY_CALCULATED +# endif /* __ */ +# endif /* __GNUC__ */ +#endif /* OPENSSL_NO_ASM */ + + +/* BN_div computes dv := num / divisor, rounding towards + * zero, and sets up rm such that dv*divisor + rm = num holds. + * Thus: + * dv->neg == num->neg ^ divisor->neg (unless the result is zero) + * rm->neg == num->neg (unless the remainder is zero) + * If 'dv' or 'rm' is NULL, the respective value is not returned. + */ +int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor, + BN_CTX *ctx) { - int norm_shift,i,j,loop; + int norm_shift,i,loop; BIGNUM *tmp,wnum,*snum,*sdiv,*res; BN_ULONG *resp,*wnump; BN_ULONG d0,d1; int num_n,div_n; + int no_branch=0; + + /* Invalid zero-padding would have particularly bad consequences + * in the case of 'num', so don't just rely on bn_check_top() for this one + * (bn_check_top() works only for BN_DEBUG builds) */ + if (num->top > 0 && num->d[num->top - 1] == 0) + { + BNerr(BN_F_BN_DIV,BN_R_NOT_INITIALIZED); + return 0; + } + + bn_check_top(num); + + if ((BN_get_flags(num, BN_FLG_CONSTTIME) != 0) || (BN_get_flags(divisor, BN_FLG_CONSTTIME) != 0)) + { + no_branch=1; + } + + bn_check_top(dv); + bn_check_top(rm); + /* bn_check_top(num); */ /* 'num' has been checked already */ + bn_check_top(divisor); if (BN_is_zero(divisor)) { @@ -138,7 +217,7 @@ BN_CTX *ctx; return(0); } - if (BN_ucmp(num,divisor) < 0) + if (!no_branch && BN_ucmp(num,divisor) < 0) { if (rm != NULL) { if (BN_copy(rm,num) == NULL) return(0); } @@ -146,35 +225,58 @@ BN_CTX *ctx; return(1); } - tmp=ctx->bn[ctx->tos]; - tmp->neg=0; - snum=ctx->bn[ctx->tos+1]; - sdiv=ctx->bn[ctx->tos+2]; + BN_CTX_start(ctx); + tmp=BN_CTX_get(ctx); + snum=BN_CTX_get(ctx); + sdiv=BN_CTX_get(ctx); if (dv == NULL) - res=ctx->bn[ctx->tos+3]; + res=BN_CTX_get(ctx); else res=dv; + if (sdiv == NULL || res == NULL || tmp == NULL || snum == NULL) + goto err; /* First we normalise the numbers */ norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2); - BN_lshift(sdiv,divisor,norm_shift); + if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err; sdiv->neg=0; norm_shift+=BN_BITS2; - BN_lshift(snum,num,norm_shift); + if (!(BN_lshift(snum,num,norm_shift))) goto err; snum->neg=0; + + if (no_branch) + { + /* Since we don't know whether snum is larger than sdiv, + * we pad snum with enough zeroes without changing its + * value. + */ + if (snum->top <= sdiv->top+1) + { + if (bn_wexpand(snum, sdiv->top + 2) == NULL) goto err; + for (i = snum->top; i < sdiv->top + 2; i++) snum->d[i] = 0; + snum->top = sdiv->top + 2; + } + else + { + if (bn_wexpand(snum, snum->top + 1) == NULL) goto err; + snum->d[snum->top] = 0; + snum->top ++; + } + } + div_n=sdiv->top; num_n=snum->top; loop=num_n-div_n; - /* Lets setup a 'window' into snum * This is the part that corresponds to the current * 'area' being divided */ - wnum.d= &(snum->d[loop]); - wnum.top= div_n; - wnum.max= snum->max; /* a bit of a lie */ - wnum.neg= 0; + wnum.neg = 0; + wnum.d = &(snum->d[loop]); + wnum.top = div_n; + /* only needed when BN_ucmp messes up the values between top and max */ + wnum.dmax = snum->dmax - loop; /* so we don't step out of bounds */ /* Get the top 2 words of sdiv */ - /* i=sdiv->top; */ + /* div_n=sdiv->top; */ d0=sdiv->d[div_n-1]; d1=(div_n == 1)?0:sdiv->d[div_n-2]; @@ -183,104 +285,166 @@ BN_CTX *ctx; /* Setup to 'res' */ res->neg= (num->neg^divisor->neg); - res->top=loop; if (!bn_wexpand(res,(loop+1))) goto err; + res->top=loop-no_branch; resp= &(res->d[loop-1]); /* space for temp */ if (!bn_wexpand(tmp,(div_n+1))) goto err; - if (BN_ucmp(&wnum,sdiv) >= 0) + if (!no_branch) { - bn_qsub(&wnum,&wnum,sdiv); - *resp=1; - res->d[res->top-1]=1; + if (BN_ucmp(&wnum,sdiv) >= 0) + { + /* If BN_DEBUG_RAND is defined BN_ucmp changes (via + * bn_pollute) the const bignum arguments => + * clean the values between top and max again */ + bn_clear_top2max(&wnum); + bn_sub_words(wnum.d, wnum.d, sdiv->d, div_n); + *resp=1; + } + else + res->top--; } + + /* if res->top == 0 then clear the neg value otherwise decrease + * the resp pointer */ + if (res->top == 0) + res->neg = 0; else - res->top--; - resp--; + resp--; - for (i=0; i 0x%08X\n", + n0, n1, d0, q); +#endif +#endif + +#ifndef REMAINDER_IS_ALREADY_CALCULATED + /* + * rem doesn't have to be BN_ULLONG. The least we + * know it's less that d0, isn't it? + */ + rem=(n1-q*d0)&BN_MASK2; +#endif t2=(BN_ULLONG)d1*q; - rem=t1-(BN_ULLONG)q*d0; - if ((rem>>BN_BITS2) || - (t2 <= ((BN_ULLONG)(rem< 0x%08X\n", + n0, n1, d0, q); +#endif +#ifndef REMAINDER_IS_ALREADY_CALCULATED + rem=(n1-q*d0)&BN_MASK2; +#endif + +#if defined(BN_UMULT_LOHI) + BN_UMULT_LOHI(t2l,t2h,d1,q); +#elif defined(BN_UMULT_HIGH) + t2l = d1 * q; + t2h = BN_UMULT_HIGH(d1,q); #else - BN_ULONG t1l,t1h,t2l,t2h,t3l,t3h,ql,qh,t3t; - t1h=n0; - t1l=n1; - for (;;) { + BN_ULONG ql, qh; t2l=LBITS(d1); t2h=HBITS(d1); ql =LBITS(q); qh =HBITS(q); mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */ - - t3t=LBITS(d0); t3h=HBITS(d0); - mul64(t3t,t3h,ql,qh); /* t3=t1-(BN_ULLONG)q*d0; */ - t3l=(t1l-t3t)&BN_MASK2; - if (t3l > t1l) t3h++; - t3h=(t1h-t3h)&BN_MASK2; - - /*if ((t3>>BN_BITS2) || - (t2 <= ((t3<d,sdiv->d,div_n,q); - tmp->d[div_n]=l0; - for (j=div_n+1; j>0; j--) - if (tmp->d[j-1]) break; - tmp->top=j; - j=wnum.top; - BN_sub(&wnum,&wnum,tmp); - - snum->top=snum->top+wnum.top-j; + for (;;) + { + if ((t2h < rem) || + ((t2h == rem) && (t2l <= wnump[-2]))) + break; + q--; + rem += d0; + if (rem < d0) break; /* don't let rem overflow */ + if (t2l < d1) t2h--; t2l -= d1; + } +#endif /* !BN_LLONG */ + } +#endif /* !BN_DIV3W */ - if (wnum.neg) + l0=bn_mul_words(tmp->d,sdiv->d,div_n,q); + tmp->d[div_n]=l0; + wnum.d--; + /* ingore top values of the bignums just sub the two + * BN_ULONG arrays with bn_sub_words */ + if (bn_sub_words(wnum.d, wnum.d, tmp->d, div_n+1)) { + /* Note: As we have considered only the leading + * two BN_ULONGs in the calculation of q, sdiv * q + * might be greater than wnum (but then (q-1) * sdiv + * is less or equal than wnum) + */ q--; - j=wnum.top; - BN_add(&wnum,&wnum,sdiv); - snum->top+=wnum.top-j; + if (bn_add_words(wnum.d, wnum.d, sdiv->d, div_n)) + /* we can't have an overflow here (assuming + * that q != 0, but if q == 0 then tmp is + * zero anyway) */ + (*wnump)++; } - *(resp--)=q; - wnump--; + /* store part of the result */ + *resp = q; } + bn_correct_top(snum); if (rm != NULL) { + /* Keep a copy of the neg flag in num because if rm==num + * BN_rshift() will overwrite it. + */ + int neg = num->neg; BN_rshift(rm,snum,norm_shift); - rm->neg=num->neg; + if (!BN_is_zero(rm)) + rm->neg = neg; + bn_check_top(rm); } + if (no_branch) bn_correct_top(res); + BN_CTX_end(ctx); return(1); err: + bn_check_top(rm); + BN_CTX_end(ctx); return(0); } - #endif