BN_ULONG d0,d1;
int num_n,div_n;
- if (dv)
- bn_check_top(dv);
- if (rm)
- bn_check_top(rm);
+ if ((BN_get_flags(num, BN_FLG_CONSTTIME) != 0) || (BN_get_flags(divisor, BN_FLG_CONSTTIME) != 0))
+ {
+ return BN_div_no_branch(dv, rm, num, divisor, ctx);
+ }
+
+ bn_check_top(dv);
+ bn_check_top(rm);
bn_check_top(num);
bn_check_top(divisor);
BN_CTX_end(ctx);
return(1);
err:
- if (rm)
+ bn_check_top(rm);
+ BN_CTX_end(ctx);
+ return(0);
+ }
+
+
+/* BN_div_no_branch is a special version of BN_div. It does not contain
+ * branches that may leak sensitive information.
+ */
+int BN_div_no_branch(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num,
+ const BIGNUM *divisor, BN_CTX *ctx)
+ {
+ int norm_shift,i,loop;
+ BIGNUM *tmp,wnum,*snum,*sdiv,*res;
+ BN_ULONG *resp,*wnump;
+ BN_ULONG d0,d1;
+ int num_n,div_n;
+
+ bn_check_top(dv);
+ bn_check_top(rm);
+ bn_check_top(num);
+ bn_check_top(divisor);
+
+ if (BN_is_zero(divisor))
+ {
+ BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
+ return(0);
+ }
+
+ BN_CTX_start(ctx);
+ tmp=BN_CTX_get(ctx);
+ snum=BN_CTX_get(ctx);
+ sdiv=BN_CTX_get(ctx);
+ if (dv == NULL)
+ res=BN_CTX_get(ctx);
+ else res=dv;
+ if (sdiv == NULL || res == NULL) goto err;
+
+ /* First we normalise the numbers */
+ norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
+ if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err;
+ sdiv->neg=0;
+ norm_shift+=BN_BITS2;
+ if (!(BN_lshift(snum,num,norm_shift))) goto err;
+ snum->neg=0;
+
+ /* 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.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 */
+ /* div_n=sdiv->top; */
+ d0=sdiv->d[div_n-1];
+ d1=(div_n == 1)?0:sdiv->d[div_n-2];
+
+ /* pointer to the 'top' of snum */
+ wnump= &(snum->d[num_n-1]);
+
+ /* Setup to 'res' */
+ res->neg= (num->neg^divisor->neg);
+ if (!bn_wexpand(res,(loop+1))) goto err;
+ res->top=loop-1;
+ resp= &(res->d[loop-1]);
+
+ /* space for temp */
+ if (!bn_wexpand(tmp,(div_n+1))) goto err;
+
+ /* if res->top == 0 then clear the neg value otherwise decrease
+ * the resp pointer */
+ if (res->top == 0)
+ res->neg = 0;
+ else
+ resp--;
+
+ for (i=0; i<loop-1; i++, wnump--, resp--)
+ {
+ BN_ULONG q,l0;
+ /* the first part of the loop uses the top two words of
+ * snum and sdiv to calculate a BN_ULONG q such that
+ * | wnum - sdiv * q | < sdiv */
+#if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM)
+ BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG);
+ q=bn_div_3_words(wnump,d1,d0);
+#else
+ BN_ULONG n0,n1,rem=0;
+
+ n0=wnump[0];
+ n1=wnump[-1];
+ if (n0 == d0)
+ q=BN_MASK2;
+ else /* n0 < d0 */
+ {
+#ifdef BN_LLONG
+ BN_ULLONG t2;
+
+#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
+ q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0);
+#else
+ q=bn_div_words(n0,n1,d0);
+#ifdef BN_DEBUG_LEVITTE
+ fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
+X) -> 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;
+
+ for (;;)
+ {
+ if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
+ break;
+ q--;
+ rem += d0;
+ if (rem < d0) break; /* don't let rem overflow */
+ t2 -= d1;
+ }
+#else /* !BN_LLONG */
+ BN_ULONG t2l,t2h,ql,qh;
+
+ q=bn_div_words(n0,n1,d0);
+#ifdef BN_DEBUG_LEVITTE
+ fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\
+X) -> 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
+ t2l=LBITS(d1); t2h=HBITS(d1);
+ ql =LBITS(q); qh =HBITS(q);
+ mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
+#endif
+
+ 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 */
+
+ 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--;
+ 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)++;
+ }
+ /* 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);
+ if (!BN_is_zero(rm))
+ rm->neg = neg;
bn_check_top(rm);
+ }
+ bn_correct_top(res);
+ BN_CTX_end(ctx);
+ return(1);
+err:
+ bn_check_top(rm);
BN_CTX_end(ctx);
return(0);
}
projects / openssl.git / blobdiff