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[VM bigint] Fix padding length in Montgomery Reduction (fixes #32626).

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Add regression test to existing bigint test.

Change-Id: I9e470c4002c25493285ce6bb908375ff913a4e17
Reviewed-on: https://dart-review.googlesource.com/54070
Reviewed-by: Alexander Markov <alexmarkov@google.com>
This commit is contained in:
Régis Crelier 2018-05-07 21:38:30 +00:00
parent 8515d74332
commit e62dd0157e
2 changed files with 27 additions and 3 deletions
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7
runtime/lib/bigint_patch.dart
View file

@ -2628,7 +2628,8 @@ class _BigIntMontgomeryReduction implements _BigIntReduction {
}
_BigIntImpl _revert(Uint32List xDigits, int xUsed) {
var resultDigits = _newDigits(2 * _normModulusUsed);
// Reserve enough digits for modulus squaring and accumulator carry.
var resultDigits = _newDigits(2 * _normModulusUsed + 2);
var i = xUsed + (xUsed & 1);
while (--i >= 0) {
resultDigits[i] = xDigits[i];
@ -2640,8 +2641,8 @@ class _BigIntMontgomeryReduction implements _BigIntReduction {
// x = x/R mod _modulus.
// Returns xUsed.
int _reduce(Uint32List xDigits, int xUsed) {
while (xUsed < 2 * _normModulusUsed) {
// Pad x so _mulAdd has enough room later.
while (xUsed < 2 * _normModulusUsed + 2) {
// Pad x so _mulAdd has enough room later for a possible carry.
xDigits[xUsed++] = 0;
}
var i = 0;

23
tests/corelib_2/bigint_test.dart
View file

@ -484,6 +484,29 @@ testBigintModPow() {
e = BigInt.parse("123456789012345678901234567890");
m = BigInt.parse("123456789012345678901234567899");
Expect.equals(BigInt.parse("40128068573873018143207285483"), x.modPow(e, m));
x = BigInt.parse(
"142223781135477974841804437037182877109549636480215350570761436386728140"
"00321219503871352719175100865184619168128345594681547640115731246638");
e = BigInt.parse(
"688057170495263083245752731085731160016625265771524738691797062279575950"
"919479651156310413084174304361991240273181430924411258203766946639349880"
"404106504114953688890200429043051936362182997575167191584461538746041795"
"019663740246921124383173799957296515067912829778249931473903780958741032"
"64534184571632120755");
m = BigInt.parse(
"144173682842817587002196172066264549138375068078359231382946906898412792"
"452632726597279520229873489736777248181678202636100459215718497240474064"
"366927544074501134727745837254834206456400508719134610847814227274992298"
"238973375146473350157304285346424982280927848339601514720098577525635486"
"320547905945936448443");
Expect.equals(
BigInt.parse(
"41228476947144730491819644448449646627743926889389391986712371102685"
"14984467753960109321610008533258676279344318597060690521027646613453"
"25674994677820913027869835916005689276806408148698486814119894325284"
"18918299321385420296108046942018595594076729397423805685944237555128"
"652606412065971965116137839721723231"),
x.modPow(e, m));
}
testBigintModInverse() {