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SP int: sp_invmod_div check div result before proceeding

pull/5829/head
Sean Parkinson 2022-11-30 17:37:21 +10:00
parent faf848a915
commit c7c80be15e
1 changed files with 54 additions and 49 deletions
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103
wolfcrypt/src/sp_int.c
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@ -11430,8 +11430,8 @@ static int _sp_invmod_div(sp_int* a, sp_int* m, sp_int* x, sp_int* y, sp_int* b,
sp_int* c, sp_int* inv)
{
int err = MP_OKAY;
sp_int* d;
sp_int* r;
sp_int* d = NULL;
sp_int* r = NULL;
sp_int* s;
#ifndef WOLFSSL_SP_INT_NEGATIVE
int bneg = 0;
@ -11456,23 +11456,25 @@ static int _sp_invmod_div(sp_int* a, sp_int* m, sp_int* x, sp_int* y, sp_int* b,
while ((err == MP_OKAY) && (!sp_isone(x)) && (!sp_iszero(x))) {
/* 2.1. d = x / y, r = x mod y */
err = sp_div(x, y, d, r);
/* 2.2. c -= d * b */
if (sp_isone(d)) {
/* c -= 1 * b */
sp_sub(c, b, c);
}
else {
/* d *= b */
err = sp_mul(d, b, d);
/* c -= d */
if (err == MP_OKAY) {
sp_sub(c, d, c);
if (err == MP_OKAY) {
/* 2.2. c -= d * b */
if (sp_isone(d)) {
/* c -= 1 * b */
sp_sub(c, b, c);
}
else {
/* d *= b */
err = sp_mul(d, b, d);
/* c -= d */
if (err == MP_OKAY) {
sp_sub(c, d, c);
}
}
/* 2.3. x = y, y = r */
s = x; x = y; y = r; r = s;
/* 2.4. s = b, b = c, c = s */
s = b; b = c; c = s;
}
/* 2.3. x = y, y = r */
s = x; x = y; y = r; r = s;
/* 2.4. s = b, b = c, c = s */
s = b; b = c; c = s;
}
/* 3. If y != 0 then NO_INVERSE */
if ((err == MP_OKAY) && (!sp_iszero(y))) {
@ -11491,46 +11493,49 @@ static int _sp_invmod_div(sp_int* a, sp_int* m, sp_int* x, sp_int* y, sp_int* b,
while ((err == MP_OKAY) && (!sp_isone(x)) && (!sp_iszero(x))) {
/* 2.1. d = x / y, r = x mod y */
err = sp_div(x, y, d, r);
if (sp_isone(d)) {
/* c -= 1 * b */
if ((bneg ^ cneg) == 1) {
/* c -= -b or -c -= b, therefore add. */
_sp_add_off(c, b, c, 0);
}
else if (_sp_cmp_abs(c, b) == MP_LT) {
/* |c| < |b| and same sign, reverse subtract and negate. */
_sp_sub_off(b, c, c, 0);
cneg = !cneg;
}
else {
/* |c| >= |b| */
_sp_sub_off(c, b, c, 0);
}
}
else {
/* d *= b */
err = sp_mul(d, b, d);
/* c -= d */
if (err == MP_OKAY) {
if (err == MP_OKAY) {
if (sp_isone(d)) {
/* c -= 1 * b */
if ((bneg ^ cneg) == 1) {
/* c -= -d or -c -= d, therefore add. */
_sp_add_off(c, d, c, 0);
/* c -= -b or -c -= b, therefore add. */
_sp_add_off(c, b, c, 0);
}
else if (_sp_cmp_abs(c, d) == MP_LT) {
/* |c| < |d| and same sign, reverse subtract and negate. */
_sp_sub_off(d, c, c, 0);
else if (_sp_cmp_abs(c, b) == MP_LT) {
/* |c| < |b| and same sign, reverse subtract and negate. */
_sp_sub_off(b, c, c, 0);
cneg = !cneg;
}
else {
_sp_sub_off(c, d, c, 0);
/* |c| >= |b| */
_sp_sub_off(c, b, c, 0);
}
}
else {
/* d *= b */
err = sp_mul(d, b, d);
/* c -= d */
if (err == MP_OKAY) {
if ((bneg ^ cneg) == 1) {
/* c -= -d or -c -= d, therefore add. */
_sp_add_off(c, d, c, 0);
}
else if (_sp_cmp_abs(c, d) == MP_LT) {
/* |c| < |d| and same sign, reverse subtract and negate.
*/
_sp_sub_off(d, c, c, 0);
cneg = !cneg;
}
else {
_sp_sub_off(c, d, c, 0);
}
}
}
/* 2.3. x = y, y = r */
s = x; x = y; y = r; r = s;
/* 2.4. s = b, b = c, c = s */
s = b; b = c; c = s;
neg = bneg; bneg = cneg; cneg = neg;
}
/* 2.3. x = y, y = r */
s = x; x = y; y = r; r = s;
/* 2.4. s = b, b = c, c = s */
s = b; b = c; c = s;
neg = bneg; bneg = cneg; cneg = neg;
}
/* 3. If y != 0 then NO_INVERSE */
if ((err == MP_OKAY) && (!sp_iszero(y))) {