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SP int: fixes from review by Claude #10235

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Merged
dgarske merged 1 commit into from
Apr 16, 2026
+50 −32
Merged

SP int: fixes from review by Claude #10235

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82 changes: 50 additions & 32 deletions wolfcrypt/src/sp_int.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8546,14 +8546,17 @@ static int sp_lshb(sp_int* a, int n)
if (a->used != 0) {
/* Calculate number of digits to shift. */
sp_size_t s = (sp_size_t)n >> SP_WORD_SHIFT;
/* Get count of bits to move in digit. */
n &= (int)SP_WORD_MASK;

/* Ensure number has enough digits for result. */
if (a->used + s >= a->size) {
if ((n != 0) && (a->used + s >= a->size)) {
err = MP_VAL;
}
else if ((s > 0) && (a->used + s > a->size)) {
err = MP_VAL;
}
if (err == MP_OKAY) {
/* Get count of bits to move in digit. */
n &= (int)SP_WORD_MASK;
/* Check whether this is a complicated case. */
if (n != 0) {
unsigned int i;
Expand Down Expand Up @@ -12258,24 +12261,30 @@ static int _sp_mulmod_tmp(const sp_int* a, const sp_int* b, const sp_int* m,
sp_int* r)
{
int err = MP_OKAY;
/* Create temporary for multiplication result. */
DECL_SP_INT(t, a->used + b->used);

ALLOC_SP_INT(t, a->used + b->used, err, NULL);
if (err == MP_OKAY) {
err = sp_init_size(t, (sp_size_t)(a->used + b->used));
if (sp_iszero(a) || sp_iszero(b)) {
_sp_zero(r);
}
else {
/* Create temporary for multiplication result. */
DECL_SP_INT(t, a->used + b->used);

/* Multiply and reduce. */
if (err == MP_OKAY) {
err = sp_mul(a, b, t);
}
if (err == MP_OKAY) {
err = sp_mod(t, m, r);
}
ALLOC_SP_INT(t, a->used + b->used, err, NULL);
if (err == MP_OKAY) {
err = sp_init_size(t, (sp_size_t)(a->used + b->used));
}

/* Dispose of an allocated SP int. */
FREE_SP_INT(t, NULL);
/* Multiply and reduce. */
if (err == MP_OKAY) {
err = sp_mul(a, b, t);
}
if (err == MP_OKAY) {
err = sp_mod(t, m, r);
}

/* Dispose of an allocated SP int. */
FREE_SP_INT(t, NULL);
}

return err;
}
Expand Down Expand Up @@ -14851,7 +14860,8 @@ int sp_mod_2d(const sp_int* a, int e, sp_int* r)
if (err == MP_OKAY) {
/* Copy a into r if not same pointer. */
if (a != r) {
XMEMCPY(r->dp, a->dp, digits * (word32)SP_WORD_SIZEOF);
sp_size_t cnt = (a->used < digits) ? a->used : digits;
XMEMCPY(r->dp, a->dp, cnt * (word32)SP_WORD_SIZEOF);
r->used = a->used;
#ifdef WOLFSSL_SP_INT_NEGATIVE
r->sign = a->sign;
Expand All @@ -14870,9 +14880,10 @@ int sp_mod_2d(const sp_int* a, int e, sp_int* r)
if (a->sign == MP_NEG) {
unsigned int i;
sp_int_digit carry = 0;
sp_size_t cnt = (r->used < digits) ? r->used : digits;

/* Negate value. */
for (i = 0; i < r->used; i++) {
for (i = 0; i < cnt; i++) {
sp_int_digit next = r->dp[i] > 0;
r->dp[i] = (sp_int_digit)0 - r->dp[i] - carry;
carry |= next;
Expand Down Expand Up @@ -17401,24 +17412,31 @@ int sp_sqr(const sp_int* a, sp_int* r)
static int _sp_sqrmod(const sp_int* a, const sp_int* m, sp_int* r)
{
int err = MP_OKAY;
/* Create temporary for multiplication result. */
DECL_SP_INT(t, a->used * 2);

ALLOC_SP_INT(t, a->used * 2, err, NULL);
if (err == MP_OKAY) {
err = sp_init_size(t, a->used * 2U);
if (sp_iszero(a)) {
_sp_zero(r);
}
else {
/* Create temporary for multiplication result. */
DECL_SP_INT(t, a->used * 2);

/* Square and reduce. */
if (err == MP_OKAY) {
err = sp_sqr(a, t);
}
if (err == MP_OKAY) {
err = sp_mod(t, m, r);
ALLOC_SP_INT(t, a->used * 2, err, NULL);
if (err == MP_OKAY) {
err = sp_init_size(t, a->used * 2U);
}

/* Square and reduce. */
if (err == MP_OKAY) {
err = sp_sqr(a, t);
}
if (err == MP_OKAY) {
err = sp_mod(t, m, r);
}

/* Dispose of an allocated SP int. */
FREE_SP_INT(t, NULL);
}

/* Dispose of an allocated SP int. */
FREE_SP_INT(t, NULL);
return err;
}

Expand Down
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