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[dart2wasm] Implement _SecureRandom._getBytes

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This only changes `_SecureRandom._getBytes` to make the rest of the code
work. Implementation is currently slow: for each random number
generation, it allocates one JS `Uint8Array`, and because we can't
directly read from a JS `Uint8Array` using `dart:js_interop`, a Dart
`Uint8List` wrapper for it. We can optimize separately.

Fixes #55031.

Fixes test lib/math/random_secure_test on browsers. The test keeps
failing in d8 as d8 doesn't define the `crypto` object.

Change-Id: I9d6bbd1bb576c0d0b7206cb2939ee65d987ec297
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/356040
Commit-Queue: Ömer Ağacan <omersa@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
This commit is contained in:
Ömer Sinan Ağacan 2024-03-12 21:26:51 +00:00 committed by Commit Queue
parent ff0f5c4bdb
commit 12859761b9
1 changed files with 40 additions and 6 deletions
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46
sdk/lib/_internal/wasm/lib/math_patch.dart
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@ -2,9 +2,9 @@
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import "dart:_internal" show mix64, patch;
import "dart:typed_data" show Uint32List;
import "dart:_internal" show mix64, patch, unsafeCast;
import "dart:_js_types" show JSUint8ArrayImpl;
import "dart:js_interop";
/// There are no parts of this patch library.
@ -236,19 +236,53 @@ class _Random implements Random {
}
}
@JS('crypto')
external _JSCrypto get _jsCryptoGetter;
final _JSCrypto _jsCrypto = _jsCryptoGetter;
extension type _JSCrypto._(JSObject _jsCrypto) implements JSObject {}
extension _JSCryptoGetRandomValues on _JSCrypto {
@JS('getRandomValues')
external void getRandomValues(JSUint8Array array);
}
@JS('Uint8Array')
extension type _JSUint8Array(JSObject _) {
external factory _JSUint8Array.create(int length);
}
class _SecureRandom implements Random {
final JSUint8ArrayImpl _buffer = unsafeCast<JSUint8ArrayImpl>(
(_JSUint8Array.create(8) as JSUint8Array).toDart);
_SecureRandom() {
// Throw early in constructor if entropy source is not hooked up.
_getBytes(1);
}
// Return count bytes of entropy as a positive integer; count <= 8.
external static int _getBytes(int count);
// Return count bytes of entropy as an integer; count <= 8.
int _getBytes(int count) {
final JSUint8ArrayImpl bufferView =
JSUint8ArrayImpl.view(_buffer.buffer, 0, count);
final JSUint8Array bufferViewJS = bufferView.toJS;
_jsCrypto.getRandomValues(bufferViewJS);
int value = 0;
for (int i = 0; i < count; i += 1) {
value = (value << 8) | bufferView[i];
}
return value;
}
int nextInt(int max) {
RangeError.checkValueInInterval(
max, 1, _POW2_32, "max", "Must be positive and <= 2^32");
final byteCount = ((max - 1).bitLength + 7) >> 3;
final byteCount =
((max - 1).bitLength + 7) >> 3; // Divide number of bits by 8, round up.
if (byteCount == 0) {
return 0; // Not random if max == 1.
}