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sp_div improved to handle when a has less digits than d

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This commit is contained in:
Sean Parkinson
2019-11-21 10:15:12 +10:00
parent b396ed0984
commit 8315ae892f
1 changed files with 44 additions and 23 deletions
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67
wolfcrypt/src/sp_int.c
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@ -402,13 +402,13 @@ int sp_copy(sp_int* a, sp_int* r)
/* creates "a" then copies b into it */
int sp_init_copy (sp_int * a, sp_int * b)
{
int res;
if ((res = sp_init(a)) == MP_OKAY) {
if((res = sp_copy (b, a)) != MP_OKAY) {
int err;
if ((err = sp_init(a)) == MP_OKAY) {
if((err = sp_copy (b, a)) != MP_OKAY) {
sp_clear(a);
}
}
return res;
return err;
}
#endif
@ -635,6 +635,8 @@ static void _sp_mul_d(sp_int* a, sp_int_digit n, sp_int* r, int o)
static int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
{
int err = MP_OKAY;
int ret;
int done = 0;
int i;
int s;
sp_int_word w = 0;
@ -655,8 +657,24 @@ static int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
if (sp_iszero(d))
err = MP_VAL;
ret = sp_cmp(a, d);
if (ret == MP_LT) {
sp_copy(a, rem);
if (r != NULL) {
sp_set(r, 0);
}
done = 1;
}
else if (ret == MP_EQ) {
sp_set(rem, 0);
if (r != NULL) {
sp_set(r, 1);
}
done = 1;
}
#ifdef WOLFSSL_SMALL_STACK
if (err == MP_OKAY) {
if (!done && err == MP_OKAY) {
sa = (sp_int*)XMALLOC(sizeof(sp_int) * 4, NULL, DYNAMIC_TYPE_BIGINT);
if (sa == NULL)
err = MP_MEM;
@ -668,7 +686,7 @@ static int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
}
#endif
if (err == MP_OKAY) {
if (!done && err == MP_OKAY) {
sp_init(sa);
sp_init(sd);
sp_init(tr);
@ -685,26 +703,29 @@ static int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
}
tr->used = sa->used - d->used;
if ((sa->dp[sa->used-1] >> (SP_WORD_SIZE - 1)) == 1) {
_sp_mul_d(d, 1, trial, sa->used - d->used);
if (sp_cmp(sa, trial) != MP_LT) {
tr->used++;
sp_sub(sa, trial, sa);
tr->dp[sa->used - d->used] = 1;
}
}
sp_clear(tr);
dt = d->dp[d->used-1];
for (i = sa->used - 1; i >= d->used; i--) {
w = ((sp_int_word)sa->dp[i] << SP_WORD_SIZE) | sa->dp[i-1];
t = (sp_int_digit)(w / dt);
_sp_mul_d(d, t, trial, i - d->used);
while (sp_cmp(trial, sa) == MP_GT) {
t--;
_sp_mul_d(d, t, trial, i - d->used);
w /= dt;
if (w > (sp_int_digit)-1) {
t = (sp_int_digit)-1;
}
else {
t = (sp_int_digit)w;
}
if (t > 0) {
_sp_mul_d(d, t, trial, i - d->used);
while (sp_cmp(trial, sa) == MP_GT) {
t--;
_sp_mul_d(d, t, trial, i - d->used);
}
sp_sub(sa, trial, sa);
tr->dp[i - d->used] += t;
if (w > (sp_int_digit)-1) {
i++;
}
}
sp_sub(sa, trial, sa);
tr->dp[i - d->used] = t;
}
sp_clamp(tr);
@ -1882,7 +1903,7 @@ int sp_prime_is_prime_ex(sp_int* a, int t, int* result, WC_RNG* rng)
}
#ifndef NO_DH
int sp_exch (sp_int* a, sp_int* b)
int sp_exch(sp_int* a, sp_int* b)
{
int err = MP_OKAY;
#ifndef WOLFSSL_SMALL_STACK