int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
BN_CTX *ctx)
{
int norm_shift,i,loop;
BIGNUM *tmp,*snum,*sdiv,*res;
#ifdef BN_ALLOC /* pcg */
BIGNUM wnum;
#else
BN_ULONG *wnum_d;
#endif /* !BN_ALLOC */
BN_ULONG *resp,*wnump;
BN_ULONG d0,d1;
int num_n,div_n;
/* 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))
{
return BN_div_no_branch(dv, rm, num, divisor, ctx);
}
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))
{
BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
return(0);
}
if (BN_ucmp(num,divisor) < 0)
{
if (rm != NULL)
{ if (BN_copy(rm,num) == NULL) return(0); }
if (dv != NULL) BN_zero(dv);
return(1);
}
BN_CTX_start(ctx);
tmp=BN_CTX_get(ctx);
snum=BN_CTX_get_ext( ctx, BIGNUM_EXT_MUL1 ); /* pcg */
sdiv=BN_CTX_get(ctx);
if (dv == NULL)
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);
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;
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 */
#ifdef BN_ALLOC /* pcg */
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 */
#else
wnum_d = &(snum->d[loop]);
#endif /* BN_ALLOC */
/* 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;
resp= &(res->d[loop-1]);
/* space for temp */
if( div_n+1 > BIGNUM_ALLOC_WORDS ) { assert( 0 ); goto err; }
if (BN_ucmp_word(wnum_d,div_n,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
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;
#if !defined( BN_UMULT_LOHI ) && !defined( BN_UMULT_HIGH ) /* pcg */
BN_ULONG ql,qh;
#endif
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
{
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; */
}
#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_CTX_end_ext( ctx, BIGNUM_EXT_MUL1 ); /* pcg */
return(1);
err:
bn_check_top(rm);
BN_CTX_end_ext( ctx, BIGNUM_EXT_MUL1 ); /* pcg */
return(0);
}
int BN_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
{
int ret = 0;
int top, al, bl;
BIGNUM *rr;
#if defined(BN_MUL_COMBA) || defined(BN_RECURSION)
int i;
#endif
#ifdef BN_RECURSION
BIGNUM *t = NULL;
int j = 0, k;
#endif
#ifdef BN_COUNT
fprintf(stderr, "BN_mul %d * %d\n", a->top, b->top);
#endif
bn_check_top(a);
bn_check_top(b);
bn_check_top(r);
al = a->top;
bl = b->top;
if ((al == 0) || (bl == 0)) {
BN_zero(r);
return (1);
}
top = al + bl;
BN_CTX_start(ctx);
if ((r == a) || (r == b)) {
if ((rr = BN_CTX_get(ctx)) == NULL)
goto err;
} else
/* Changes for cryptlib - pcg */
{
/* Usually we can set:
rr = r;
but in the cases where t gets large (see the check further down
for overflow due to k * 2 / k * 4) the value of rr needs to be
large as well. We can't predict in advance when this will occur
so we have to use an extended-size bignum for rr in all cases */
rr = ( BIGNUM * ) BN_CTX_get_ext( ctx, BIGNUM_EXT_MUL1 );
if( rr == NULL )
goto err;
}
/* End changes for cryptlib - pcg */
rr->neg = a->neg ^ b->neg;
#if defined(BN_MUL_COMBA) || defined(BN_RECURSION)
i = al - bl;
#endif
#ifdef BN_MUL_COMBA
if (i == 0) {
# if 0
if (al == 4) {
if (bn_wexpand(rr, 8) == NULL)
goto err;
rr->top = 8;
bn_mul_comba4(rr->d, a->d, b->d);
goto end;
}
# endif
if (al == 8) {
if (bn_wexpand(rr, 16) == NULL)
goto err;
rr->top = 16;
bn_mul_comba8(rr->d, a->d, b->d);
goto end;
}
}
#endif /* BN_MUL_COMBA */
#ifdef BN_RECURSION
if ((al >= BN_MULL_SIZE_NORMAL) && (bl >= BN_MULL_SIZE_NORMAL)) {
if (i >= -1 && i <= 1) {
/*
* Find out the power of two lower or equal to the longest of the
* two numbers
*/
if (i >= 0) {
j = BN_num_bits_word((BN_ULONG)al);
}
if (i == -1) {
j = BN_num_bits_word((BN_ULONG)bl);
}
j = 1 << (j - 1);
assert(j <= al || j <= bl);
k = j + j;
/* Changes for cryptlib - pcg */
if( ( k * 2 > BIGNUM_ALLOC_WORDS ) || \
( ( al > j || bl > j ) && ( k * 4 > BIGNUM_ALLOC_WORDS ) ) )
{
/* We're about to expand the temporary bignum that we're
using to an enormous size, get a special extended-size
bignum that won't result in a storage size-check error
when used */
t = BN_CTX_get_ext( ctx, BIGNUM_EXT_MUL2 );
}
else
t = BN_CTX_get(ctx);
/* End changes for cryptlib - pcg */
if (t == NULL)
goto err;
if (al > j || bl > j) {
if (bn_wexpand(t, k * 4) == NULL)
goto err;
if (bn_wexpand(rr, k * 4) == NULL)
goto err;
bn_mul_part_recursive(rr->d, a->d, b->d,
j, al - j, bl - j, t->d);
} else { /* al <= j || bl <= j */
if (bn_wexpand(t, k * 2) == NULL)
goto err;
if (bn_wexpand(rr, k * 2) == NULL)
goto err;
bn_mul_recursive(rr->d, a->d, b->d, j, al - j, bl - j, t->d);
}
rr->top = top;
goto end;
}
# if 0
if (i == 1 && !BN_get_flags(b, BN_FLG_STATIC_DATA)) {
BIGNUM *tmp_bn = (BIGNUM *)b;
if (bn_wexpand(tmp_bn, al) == NULL)
goto err;
tmp_bn->d[bl] = 0;
bl++;
i--;
} else if (i == -1 && !BN_get_flags(a, BN_FLG_STATIC_DATA)) {
BIGNUM *tmp_bn = (BIGNUM *)a;
if (bn_wexpand(tmp_bn, bl) == NULL)
goto err;
tmp_bn->d[al] = 0;
al++;
i++;
}
if (i == 0) {
/* symmetric and > 4 */
/* 16 or larger */
j = BN_num_bits_word((BN_ULONG)al);
j = 1 << (j - 1);
k = j + j;
t = BN_CTX_get(ctx);
if (al == j) { /* exact multiple */
if (bn_wexpand(t, k * 2) == NULL)
goto err;
if (bn_wexpand(rr, k * 2) == NULL)
goto err;
bn_mul_recursive(rr->d, a->d, b->d, al, t->d);
} else {
if (bn_wexpand(t, k * 4) == NULL)
goto err;
if (bn_wexpand(rr, k * 4) == NULL)
goto err;
bn_mul_part_recursive(rr->d, a->d, b->d, al - j, j, t->d);
}
rr->top = top;
goto end;
}
# endif
}
#endif /* BN_RECURSION */
if (bn_wexpand(rr, top) == NULL)
goto err;
rr->top = top;
bn_mul_normal(rr->d, a->d, al, b->d, bl);
#if defined(BN_MUL_COMBA) || defined(BN_RECURSION)
end:
#endif
bn_correct_top(rr);
if (r != rr)
BN_copy(r, rr);
ret = 1;
err:
bn_check_top(r);
BN_CTX_end_ext( ctx, BIGNUM_EXT_MUL1 ); /* pcg */
return (ret);
}
