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Heap math: mp_add/submod_ct make work when c == d #6992

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Merged
JacobBarthelmeh merged 1 commit into from
Nov 27, 2023
Merged

Heap math: mp_add/submod_ct make work when c == d #6992

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78 changes: 57 additions & 21 deletions wolfcrypt/src/integer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3068,47 +3068,83 @@ int mp_submod(mp_int* a, mp_int* b, mp_int* c, mp_int* d)
/* d = a + b (mod c) */
int mp_addmod(mp_int* a, mp_int* b, mp_int* c, mp_int* d)
{
int res;
mp_int t;
int res;
mp_int t;

if ((res = mp_init (&t)) != MP_OKAY) {
return res;
}
if ((res = mp_init (&t)) != MP_OKAY) {
return res;
}

res = mp_add (a, b, &t);
if (res == MP_OKAY) {
res = mp_mod (&t, c, d);
}
res = mp_add (a, b, &t);
if (res == MP_OKAY) {
res = mp_mod (&t, c, d);
}

mp_clear (&t);
mp_clear (&t);

return res;
return res;
}

/* d = a - b (mod c) - a < c and b < c and positive */
int mp_submod_ct(mp_int* a, mp_int* b, mp_int* c, mp_int* d)
{
int res;
int res;
mp_int t;
mp_int* r = d;

res = mp_sub(a, b, d);
if (res == MP_OKAY && mp_isneg(d)) {
res = mp_add(d, c, d);
if (c == d) {
r = &t;

if ((res = mp_init (r)) != MP_OKAY) {
return res;
}
}

return res;
res = mp_sub (a, b, r);
if (res == MP_OKAY) {
if (mp_isneg (r)) {
res = mp_add (r, c, d);
} else if (c == d) {
res = mp_copy (r, d);
}
}

if (c == d) {
mp_clear (r);
}

return res;
}

/* d = a + b (mod c) - a < c and b < c and positive */
int mp_addmod_ct(mp_int* a, mp_int* b, mp_int* c, mp_int* d)
{
int res;
int res;
mp_int t;
mp_int* r = d;

if (c == d) {
r = &t;

res = mp_add(a, b, d);
if (res == MP_OKAY && mp_cmp(d, c) != MP_LT) {
res = mp_sub(d, c, d);
if ((res = mp_init (r)) != MP_OKAY) {
return res;
}
}

return res;
res = mp_add (a, b, r);
if (res == MP_OKAY) {
if (mp_cmp (r, c) != MP_LT) {
res = mp_sub (r, c, d);
} else if (c == d) {
res = mp_copy (r, d);
}
}

if (c == d) {
mp_clear (r);
}

return res;
}

/* computes b = a*a */
Expand Down