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

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mp_addmod_ct and mp_submod_ct expected c and d to be different pointers.
Change code to support this use case.
Fix whitespace.
This commit is contained in:
Sean Parkinson
2023-11-22 07:36:28 +10:00
parent dda72dc19c
commit 416ce54276
1 changed files with 57 additions and 21 deletions
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78
wolfcrypt/src/integer.c
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@ -3068,47 +3068,83 @@ int mp_submod(mp_int* a, mp_int* b, mp_int* c, mp_int* d)
/* d = a + b (mod c) */ /* d = a + b (mod c) */
int mp_addmod(mp_int* a, mp_int* b, mp_int* c, mp_int* d) int mp_addmod(mp_int* a, mp_int* b, mp_int* c, mp_int* d)
{ {
int res; int res;
mp_int t; mp_int t;
if ((res = mp_init (&t)) != MP_OKAY) { if ((res = mp_init (&t)) != MP_OKAY) {
return res; return res;
} }
res = mp_add (a, b, &t); res = mp_add (a, b, &t);
if (res == MP_OKAY) { if (res == MP_OKAY) {
res = mp_mod (&t, c, d); 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 */ /* 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 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 (c == d) {
if (res == MP_OKAY && mp_isneg(d)) { r = &t;
res = mp_add(d, c, d);
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 */ /* 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 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;
res = mp_add(a, b, d); if (c == d) {
if (res == MP_OKAY && mp_cmp(d, c) != MP_LT) { r = &t;
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 */ /* computes b = a*a */