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ecmult: Clean up integer types in _ecmult_wnaf #1795

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ecmult: Clean up integer types in _ecmult_wnaf #1795

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0f75e12
ecmult: Clean up integer types in strauss
real-or-random Jan 7, 2026
242df7f
ecmult: Fix VERIFY_CHECK to exclude UB
real-or-random Jan 7, 2026
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60 changes: 31 additions & 29 deletions src/ecmult_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -114,15 +114,15 @@ static void secp256k1_ecmult_odd_multiples_table(size_t n, secp256k1_ge *pre_a,
secp256k1_fe_mul(z, &ai.z, &d.z);
}

SECP256K1_INLINE static void secp256k1_ecmult_table_verify(int n, int w) {
SECP256K1_INLINE static void secp256k1_ecmult_table_verify(int32_t n, size_t w) {
(void)n;
(void)w;
VERIFY_CHECK(((n) & 1) == 1);
VERIFY_CHECK((n) >= -((1 << ((w)-1)) - 1));
VERIFY_CHECK((n) <= ((1 << ((w)-1)) - 1));
}

SECP256K1_INLINE static void secp256k1_ecmult_table_get_ge(secp256k1_ge *r, const secp256k1_ge *pre, int n, int w) {
SECP256K1_INLINE static void secp256k1_ecmult_table_get_ge(secp256k1_ge *r, const secp256k1_ge *pre, int32_t n, size_t w) {
secp256k1_ecmult_table_verify(n,w);
if (n > 0) {
*r = pre[(n-1)/2];
Expand All @@ -132,7 +132,7 @@ SECP256K1_INLINE static void secp256k1_ecmult_table_get_ge(secp256k1_ge *r, cons
}
}

SECP256K1_INLINE static void secp256k1_ecmult_table_get_ge_lambda(secp256k1_ge *r, const secp256k1_ge *pre, const secp256k1_fe *x, int n, int w) {
SECP256K1_INLINE static void secp256k1_ecmult_table_get_ge_lambda(secp256k1_ge *r, const secp256k1_ge *pre, const secp256k1_fe *x, int32_t n, size_t w) {
secp256k1_ecmult_table_verify(n,w);
if (n > 0) {
secp256k1_ge_set_xy(r, &x[(n-1)/2], &pre[(n-1)/2].y);
Expand All @@ -142,7 +142,7 @@ SECP256K1_INLINE static void secp256k1_ecmult_table_get_ge_lambda(secp256k1_ge *
}
}

SECP256K1_INLINE static void secp256k1_ecmult_table_get_ge_storage(secp256k1_ge *r, const secp256k1_ge_storage *pre, int n, int w) {
SECP256K1_INLINE static void secp256k1_ecmult_table_get_ge_storage(secp256k1_ge *r, const secp256k1_ge_storage *pre, int32_t n, size_t w) {
secp256k1_ecmult_table_verify(n,w);
if (n > 0) {
secp256k1_ge_from_storage(r, &pre[(n-1)/2]);
Expand All @@ -159,17 +159,17 @@ SECP256K1_INLINE static void secp256k1_ecmult_table_get_ge_storage(secp256k1_ge
* - the number of set values in wnaf is returned. This number is at most 256, and at most one more
* than the number of bits in the (absolute value) of the input.
*/
static int secp256k1_ecmult_wnaf(int *wnaf, int len, const secp256k1_scalar *a, int w) {
static size_t secp256k1_ecmult_wnaf(int32_t *wnaf, size_t len, const secp256k1_scalar *a, size_t w) {
secp256k1_scalar s;
int last_set_bit = -1;
int bit = 0;
int sign = 1;
int carry = 0;
size_t last_set_bit = -1;
size_t bit = 0;
int32_t sign = 1;
int32_t carry = 0;

VERIFY_CHECK(wnaf != NULL);
VERIFY_CHECK(0 <= len && len <= 256);
VERIFY_CHECK(len <= 256);
VERIFY_CHECK(a != NULL);
VERIFY_CHECK(2 <= w && w <= 31);
VERIFY_CHECK(2 <= w && w <= 30);

for (bit = 0; bit < len; bit++) {
wnaf[bit] = 0;
Expand All @@ -183,9 +183,9 @@ static int secp256k1_ecmult_wnaf(int *wnaf, int len, const secp256k1_scalar *a,

bit = 0;
while (bit < len) {
int now;
int word;
if (secp256k1_scalar_get_bits_limb32(&s, bit, 1) == (unsigned int)carry) {
size_t now;
int32_t word;
if (secp256k1_scalar_get_bits_limb32(&s, bit, 1) == (uint32_t)carry) {
bit++;
continue;
}
Expand All @@ -195,7 +195,7 @@ static int secp256k1_ecmult_wnaf(int *wnaf, int len, const secp256k1_scalar *a,
now = len - bit;
}

word = secp256k1_scalar_get_bits_var(&s, bit, now) + carry;
word = (int32_t)secp256k1_scalar_get_bits_var(&s, bit, now) + carry;

carry = (word >> (w-1)) & 1;
word -= carry << w;
Expand All @@ -207,7 +207,7 @@ static int secp256k1_ecmult_wnaf(int *wnaf, int len, const secp256k1_scalar *a,
}
#ifdef VERIFY
{
int verify_bit = bit;
size_t verify_bit = bit;

VERIFY_CHECK(carry == 0);

Expand All @@ -221,9 +221,10 @@ static int secp256k1_ecmult_wnaf(int *wnaf, int len, const secp256k1_scalar *a,
}

/* Same as secp256k1_ecmult_wnaf, but stores to int8_t array. Requires w <= 8. */
static int secp256k1_ecmult_wnaf_small(int8_t *wnaf, int len, const secp256k1_scalar *a, int w) {
int wnaf_tmp[256];
int ret, i;
static size_t secp256k1_ecmult_wnaf_small(int8_t *wnaf, size_t len, const secp256k1_scalar *a, size_t w) {
int32_t wnaf_tmp[256];
size_t ret;
size_t i;

VERIFY_CHECK(2 <= w && w <= 8);
ret = secp256k1_ecmult_wnaf(wnaf_tmp, len, a, w);
Expand All @@ -238,8 +239,8 @@ static int secp256k1_ecmult_wnaf_small(int8_t *wnaf, int len, const secp256k1_sc
struct secp256k1_strauss_point_state {
int8_t wnaf_na_1[129];
int8_t wnaf_na_lam[129];
int bits_na_1;
int bits_na_lam;
size_t bits_na_1;
size_t bits_na_lam;
};

struct secp256k1_strauss_state {
Expand All @@ -254,12 +255,12 @@ static void secp256k1_ecmult_strauss_wnaf(const struct secp256k1_strauss_state *
secp256k1_fe Z;
/* Split G factors. */
secp256k1_scalar ng_1, ng_128;
int wnaf_ng_1[129];
int bits_ng_1 = 0;
int wnaf_ng_128[129];
int bits_ng_128 = 0;
int i;
int bits = 0;
int32_t wnaf_ng_1[129];
size_t bits_ng_1 = 0;
int32_t wnaf_ng_128[129];
size_t bits_ng_128 = 0;
size_t i;
size_t bits = 0;
size_t np;
size_t no = 0;

Expand Down Expand Up @@ -334,8 +335,9 @@ static void secp256k1_ecmult_strauss_wnaf(const struct secp256k1_strauss_state *

secp256k1_gej_set_infinity(r);

for (i = bits - 1; i >= 0; i--) {
int n;
i = bits;
while (i-- > 0) {
int32_t n;
secp256k1_gej_double_var(r, r, NULL);
for (np = 0; np < no; ++np) {
if (i < state->ps[np].bits_na_1 && (n = state->ps[np].wnaf_na_1[i])) {
Expand Down